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welcome to this module in which you will beprovided with an overview of the human body and the physiology of its various systems.once completed with this module, you should be able to:identify the topographical anatomy and directional terms utilized by the emt.list the components of each of the major body systems.list the elements of the life support chain. acquire a basic understanding of common latinmedical terminology. first and foremost, this module will be lookingat the structure of the human body and its function. the study of the body’s structureis called anatomy. the study of its function is called physiology. thus, one could saythat this module is a cursory study of anatomy

and physiology.before we begin our discussion of the human body, it is important to ensure we are speakingthe same language. there must be a standardized way we view the human body, and this standardizedview provides the basis for any discussion regarding human anatomy.within the health care professions, that standard is referred to as normal anatomical position.all descriptions of the human body use this position as the starting point.as you see from the illustration, this position is a person standing, facing forward, withpalms forward. again, all descriptions of the human body, even if your specific patientat the time is nowhere close to being in this position, are made from this common referencepoint.

from this starting position, we can now identifysome landmarks. the first thing we will do is divide the body into planes.given the normal anatomical position, splitting the body down the middle from top to bottomgenerates sagittal, medial, or lateral planes. (the terms are used interchangeably; you maysee one used over another in various textbooks.) the line we just drew to produce the sagittal/median/lateralplanes is referred to as the midline. this also breaks the body up into both a rightand a left side. with the normal anatomical position as our reference, right and leftalways refer to the patient’s right and left, not the provider’s (which is oppositewhen looking at the patient from the front). using this midline for a reference, itemscloser to the midline are considered medial,

while those away from the midline, towardthe periphery, are referred to as lateral. your arms, for instance, have both a medialand a lateral side. along similar lines, we also can refer tothings on a relative basis by using the terms proximal and distal. body parts and structuresthat are closer to the midline or torso than other body parts and structures are said tobe proximal. inversely, body parts and structures that are further from the midline or torsothan other body parts and structures are said to be distal. for instance, the elbow is distalfrom the shoulder, but proximal from the wrist. your collarbones are called clavicles. mid-clavicularrefers to a vertical line drawn across the middle of the clavicle.when viewed from the normal anatomical position,

there is a great deal of symmetry betweenthe right and left sides of the body. if a body part or structure is present on bothsides of the body, such as a person’s eyes, they are said to be bilateral. inversely,something located on a single side of the body is said to be unilateral.if we were to split the body in half, top and bottom, along the pelvic girdle, we wouldcreate transverse or axial planes. given the normal anatomical position, the term superiorrefers to anything above something else and inferior refers to anything below somethingelse. the terms are relative. for instance, the nose may be superior to the mouth, butit is inferior to the eyes. when viewing the human body from the side,we begin with the middle of the armpit as

our landmark. the armpit is called the axilla.if we draw a line from the middle of the axilla to the ankle, the result is the mid-axillaryline. this line then creates the frontal or coronal planes.when referring to the front half of the body, the terms anterior or ventral are used. whenreferring to the back half of the body, the terms posterior or dorsal are used.given the many positions in which you may find a patient, it is important to rememberthat these terms are not relative, they are absolute. thus, an individual’s posteriorside is the same, regardless of whether the patient is face-up, face-down, or somewherein the middle. when abdominal emergencies are discussed laterin this course, it will be important to know

the anatomical structures within each quadrant.in discussing a patient’s abdomen, we divide the abdomen into quarters, or quadrants, byimaginary horizontal and vertical lines that intersect at the belly button (navel). again,our reference is that of the patient’s perspective, so the quadrants on the right-hand side ofthe patient are called right upper and right lower quadrants (with the upper quadrant obviouslysuperior to the lower, or the lower quadrant inferior to the upper, depending on your perspective).given that, the quadrants on the left-hand side of the patient are called the left upperand left lower quadrants. hands and feet are very important to the humanbody and have their own terms as well. plantar refers to the sole of the foot and palmarrefers to the palm of the hand.

in addition to a knowledge of common landmarks,it is also important to be familiar with various positions in which a patient may be foundor transported. a person on his or her back (face-up) is ina supine position. a person on his or her abdomen (face-down)is in a prone position. a person on his or her side is in a lateralrecumbent position. because this is a common position in which to transport unconscious,non-trauma patients (given the repositioning of the mouth to allow for the drainage offluid or vomit), this position is often times referred to as the recovery position.in many instances, it is preferable to transport patients in a sitting position. such a positionis called the fowlers position. if the patient

is in a semi-sitting position, the positionis called semi-fowlers. exactly when fowlers becomes semi-fowlers and vice-versa is a greyarea with no specific definition. some consider a 45Ⱐangle to still be fowlers, while manywould call it semi-fowlers. ultimately, the more upright someone is sitting, the closerit is to fowlers; the more someone is reclining, the closer it is to semi-fowlers.there is also a position called the trendelenburg position in which the patient’s feet areelevated above his or her head. first aid teaches that a person in shock should havehis or her feet elevated so gravity can assist in keeping blood up in the head and torso.as a result, this position is also referred to as the shock position.with our introduction to anatomical landmarks

and positional terms completed, we can nowbegin focusing on the different systems within the body.we will begin by first discussing the six major body systems:skeletal, muscular, respiratory, circulatory, nervous, and integumentary.we will then continue by discussing the remaining systems:digestive, endocrine, renal, and reproductive. the first body system we will be discussingis the skeletal system. the skeletal system is comprised of bones,206 in all for an adult. joints are formed where bones meet (and will be discussed ingreater detail later in this course). the skeletal system provides infrastructurefor the human body. think of the skeletal

system as the framing for a building. withoutthe 2’x4’s underneath, drywall and paint are useless. without our bones, there wouldbe no structure for our other systems and tissues. our bones also provide critical protectionfor many of our organs, such as the heart, lungs, kidneys, spleen, etc. our joints makeit possible for us to move (in conjunction with the muscular system) and the bones themselvescreate blood cells (in the bone marrow) and store minerals.working our way from the top to the bottom, we first encounter the skull. the skull isthe bony structure of the head. it’s main purpose is to enclose and protect the brain.on the anterior side is the face. there are several bones that make up the face. the functionof the face is obvious. the eyes are protected

by the facial bones, as are the superior portionsof our respiratory and digestive systems (which we will discuss later).beneath the head is our spinal or vertebral column. our spine consists of 33 separatevertebrae, all designed to keep us upright, provide for motion, and protect our centralnervous system and spinal cord. the spine is divided into five parts. the first theis the cervical spine. consisting of seven vertebrae, this is the portion of the spinelaymen would describe as the neck. proceeding inferior are the 12 vertebrae of the thoracicspine. these vertebrae form the upper back and also are connected to the posterior ribcage. inferior to the thoracic spine are the five vertebrae of the lumbar spine, whichform the small of the back. inferior to the

lumbar spine is the sacral spine, which isactually five separate vertebrae fused together to form a structure known as the sacrum. lastly,we come to the coccygeal spine, which contains four vertebrae fused together to form thecoccyx. to tell the difference between the various vertebrae, they are named based ontheir relative position within these spinal regions. cervical vertebrae are labeled witha capital c, followed by the number one through seven with c1 being superior and c7 beinginferior. the same is done for the thoracic vertebrae, using the letter t and the numbersone through twelve. the lumbar vertebrae use an l and the numbers one through five, andthe sacral vertebrae use an s and the numbers one through five as well. the spine is sovery important to the health of the body given

its protection of our spinal cord. significantinjuries to the spine can result in chronic pain, paralysis, or even death. as a result,spinal precautions for trauma patients will be covered in tremendous depth later withinthis course. anterior to the vertebral column, inferiorto the skull and face, sits the thorax. in lay terms, the thorax is a person’s chest.the ribs and other bones of the thorax serve primarily to protect our vital organs andmajor blood vessels. in conjunction with the diaphragm and intercostal muscles, the thoraxalso produces both negative and positive thoracic pressure that results in ventilation (breathing).inferior to the thorax sits the pelvis. the pelvis consists of three separate bones thatare fused together and it serves as the foundation

(the basement floor, if you will) for theorgans located above it, such as the intestines, bladder, and female reproductive organs. italso provides varying levels of protection for those organs as well.continuing down, we encounter the lower extremities. otherwise known as the legs and feet. thelarge bone connected to the pelvis is the femur. inferior to the femur are the tibiaand fibula, which form the lower leg. (to differentiate the two bones, the tibia iscommonly called the shin bone.) the patella is the bone that covers the knee joint betweenthe femur and the tibia. on the bottom of the lower extremities are the tarsals, metatarsals,calcaneus, and phalanges of the ankle, heel, feet, and toes.lastly, we need to move back up the body to

discuss our upper extremities. connected tothe thorax are our shoulders, arms, and hands. the shoulder consists predominantly of theclavicle, our collarbone; the scapula, the flat bone on the posterior side; and, theproximal humerus. the upper arm is therefore called the humerus. distal is the elbow jointthat joins the humerus with the distal arm bones, the radius and ulna. (the radius isthe lateral bone of the forearm. it is always aligned with the thumb.) distal from the radiusand ulna are the carpals, metacarpals, and phalanges of the wrists, hands, and fingers.remember that bones are rigid and do not bend. so that we can move, our skeletal system alsocontains joints where these rigid bones meet. some joints work like hinges, such as theknee and elbow. the joints between vertebrae

allow for rotational movement so we can twistand turn our bodies, in addition to allowing us a certain amount of flexibility to bendover and backward. ball and socket joints, such as the hips and shoulders, provide fortremendous articulation and range of motion. ligaments, cartilage, bones, muscles, andtendons all work in concert to provide for movement.injuries to the skeletal system can have dire consequences given its role in protectingorgans, providing structure, and allowing for movement and range of motion. addressingissues pertinent to the skeletal system is a vital component of practicing emergencymedicine. integral to the skeletal system is the muscularsystem. the two are so intertwined that some

refer to both systems as a single musculoskeletalsystem. for our purposes as emergency medicine providers, however, we will consider the twoas separate systems. the muscles in our body perform some veryimportant functions. first and foremost, the muscles provide for movement. this movementis not just that associated with gross and fine motor functions, such as standing, sitting,walking, and manipulating objects in our environment, but the muscles are also responsible for themovement of blood within our body and air in and out of our lungs.our muscles give our bodies their shape; they provide additional protection for our vitalorgans and vessels; and, because muscles consume a lot of calories, they also generate ourbody heat.

it is important to recognize that not allmuscle is created equal. there are actually three different types of muscle cells withinthe human body: skeletal, smooth, and cardiac. skeletal muscle cells are also called voluntarymuscles as these are the muscles that we control through conscious thought. these are the musclesresponsible for gross movement and fine motor functions. by their very name, skeletal musclesare those we commonly think of when discussing the muscular system. they exist attached toour bones, to our skeletal system, the shape and outlines of which are commonly visibleunder the body’s skin. by contracting and relaxing in concert with each other, thesemuscles help us stand, walk, write, grab, push, pull, etc.smooth muscle cells are responsible for movement

that is not a result of conscious thought.such movement includes that of the gastrointestinal system, respiratory system, cardiac system(with the exception of the heart), and renal system. these muscles respond directly toimpulses from the brain without any intent or conscious thought on the part of the individual.as a result, these cells are also called involuntary muscle cells because they cannot be voluntarilycontrolled by the person. we do not have to think about digesting food or breathing. noconscious thought is given to constricting or relaxing blood vessels to regulate bloodpressure. given their function, smooth muscles are obviously vital to the proper functioningof the human body. the last type of muscle cells to be discussedare actually a type or subset of involuntary

cells. the heart is a muscular organ builtfrom cardiac muscle cells. these cells are very specialized and do a lot of work. imaginedoing 60 to 100 (or more) pushups per minute from before we are born until the day we die.seems unfathomable. that is exactly what the cardiac muscle in the heart does. the heartbeats by contracting and relaxing its cardiac muscle cells once a second (or more) for decades.these cells are also very unique in that the heart has the ability to generate and conductelectrical impulses on its own. (this property is called automaticity.) given the importanceof the heart to the survivability of the body and the specialized work of the cardiac cells,the heart (and its cardiac cells) needs a constant supply of oxygen and has its ownblood supply. (we will be covering the heart

and its functioning comprehensively in anothercourse module.) our next system to discuss is the respiratorysystem. before we delve into the function of the respiratory system, we will first identifythe structures of the respiratory system, beginning with the upper airway, continuingwith the lower airway, and concluding with the other structures that support ventilation.starting at the top of the respiratory system and working our way down, we first encounterthe nasal cavity. the nasal cavity does more than just give us a pathway for air to enterthe respiratory system; it also cleanses, warms and humidifies our inhaled air.just below the nasal cavity is our oral cavity, which contains the mouth, teeth, tongue, andjaw. in many instances, ems providers must

manipulate the mouth, jaw, and tongue to ensurea patent airway in an unconscious patient, so it is important to be familiar with thestructures in the oral cavity. (these structures, their significance, and their manipulationby the emt will be discussed in greater depth during the module pertinent to airway management.)the posterior of the airway in the head and neck is called the pharynx. the pharynx isdivided into three separate areas. the nasopharynx is located posterior to the nasal cavity.the oropharynx is posterior to the oral cavity. inferior to the oropharynx is the laryngopharynx,which connects the airway to the larynx and esophagus.the epiglottis lies superior to the larynx, anterior to the pharynx. it is a structureof elastic cartilage covered with a mucous

membrane and is designed to cover the larynxwhen we swallow to protect the lower airway from foreign bodies, such as food or beverages.the last upper airway structure is the larynx. commonly referred to as the voice box, thelarynx contains the vocal cords and serves as the connecting structure between the pharynxand the trachea. inferior to the larynx lies the lower airwayand its structures. the first structure is the trachea, whichis essentially the tube through with air passes from the upper airway down into bronchi, wherethe air is then diverted to both the left and right lungs. the bronchi continue to branchoff while diminishing in size to route the air throughout the entire lung. when the bronchidiminish in size to the point where they no

longer contain cartilage or glands, they becomebronchioles. at the end of the bronchioles are the alveoli.it is in the alveoli, these little sacs, that gas exchange actually occurs between the airand our bloodstream. in addition to the structures that compriseour upper and lower airways, there are other structures within our body that are essentialto supporting ventilation. we have muscles that exist between our ribs.these muscles are called intercostal muscles. we also have a diaphragm, which is a largemuscle that sits inferior to the lungs. these muscles work in conjunction with our chestwall to produce both positive and negative pressure in our lungs. when we need to breathe,it is the phrenic nerve that carries messages

back-and-forth between the respiratory controlcenter in the spinal cord and the diaphragm. because our lungs need to expand and contractwithin the chest cavity, both the lungs and the chest cavity are covered with a membraneknown as the pleura. given the existence of pleural fluid between these two layers ofmembranes, the inner and outer pleura can glide effortlessly against each other, thusfacilitating the mechanical process of breathing. lastly, the respiratory system has to connectwith the circulatory system at some point so that oxygen and carbon dioxide can be exchanged.this process occurs in the alveoli, which are covered by pulmonary capillaries.as you will find throughout the course, not all patients are the same. this is especiallytrue when discussing the respiratory system

of a pediatric patient.when managing the airway of a pediatric patient, it is important to recognize the followingdifferences in the pediatric airway: mouth and nose are smaller.the tongue is proportionally larger, taking up more relative space in the oral cavity.trachea is narrower. cricoid cartilage is less rigid and developed.airway structures are more anterior and the head is proportionally larger than the restof the body, making airway maintenance more difficult.given that the airway structures are smaller than in an adult, obstructions occur withgreater ease. this includes foreign bodies, as well as airway restriction or obstructiondue to mucous or inflammation.

airway management considerations and techniquesfor pediatrics will be discussed in greater depth in a different course module.now that we are familiar with the components of the respiratory system, it is time to identifythe system’s functions. to a layperson, the respiratory system isresponsible for breathing. for an emt, however, the respiratory system is much more complicatedthan that. the respiratory system makes both ventilationand respiration possible. while these terms are sometimes used interchangeably, doingso is actually incorrect as they mean two very different things. ventilation is themechanical process of moving air into and out of the lungs. picture a balloon inflatingand deflating. that movement of air into and

out of the balloon is ventilation. just movingair into and out of the lungs is not enough, however. somehow, we need the oxygen in thatair to enter our bloodstream. we then need that oxygen in the bloodstream to enter individualcells. as a part of doing work, our cells produce waste products, such as carbon dioxide.that carbon dioxide needs to leave the cells, enter the bloodstream, and then somehow beexpelled from the body in the air we exhale. the process by which oxygen and carbon dioxidepass between the bloodstream and cells is called respiration (or cellular respiration).within the lungs themselves, oxygen and carbon dioxide move between the alveoli and the bloodstreamby a process known as diffusion. for additional reference, perfusion will alsobe mentioned throughout this course. perfusion

is defined as the circulation of blood throughthe capillaries, which is where respiration occurs. without perfusion, there could beno diffusion or respiration. as a result, the moving of gasses, nutrients, and wasteproducts through the capillaries to and from the cells of the body is sometimes calledperfusion instead of respiration, depending on the textbook author. there are texts thatare even more specific in their definition of perfusion, using the word to describe thepassing of oxygen from the capillaries into cells (without any mention to the need forcarbon dioxide to also pass from the cells back into the capillaries). when discussingshock later in this course, the ability of the body to deliver oxygen to its cells isreferred to as perfusion, or the ability to

perfuse.the difference between ventilation and respiration is important to understand as a patient maybe ventilating adequately, but due to some ailment, is unable to respirate or perfuse.inversely, compression-only cpr works because of respiration, not ventilation. moving airin-and-out of the lungs is not as important as circulating the oxygen already existingwithin the body so that the process of cellular respiration can occur. obviously, withoutsome ventilation, some fresh oxygen in the lungs, respiration will eventually cease evenif adequate compressions are being performed as there is no oxygen left in the blood tosupply the cells. as a result, maintaining an adequate airway and ventilating a patientis an important part of performing cpr. hopefully

this example illustrates the difference betweenventilation and respiration. another function of the respiratory systemdeals with something called the acid-base balance within our bodies. our cells are constantlyproducing hydrogen ions, which become acids within the body. too much or too little acidwithin the body is a bad thing, so the body regulates its acid-base balance through severalmechanisms, one of which is through the respiratory system. carbon dioxide is a byproduct of cellularmetabolism and we expel carbon dioxide from our body by exhaling. carbon dioxide is alsoacidic. as a result, an increase in respiratory rate results in more carbon dioxide beingexpelled, making the body more alkaline. a decrease in respiratory rate, on the otherhand, retains carbon dioxide, making the body

more acidic. this process works in conjunctionwith something called the buffer (or bicarbonate buffer) system and the kidneys to regulateour body’s acid-base balance, and is yet another important function of the respiratorysystem. while all of our body systems are important,the circulatory system (or cardiovascular system, as it is also called) receives significantfocus within ems. many of the interventions you will learn within this course pertaindirectly to the circulatory system. whether the emt is performing cpr, controlling bleeding,or administering medications for chest pain, the circulatory system is a crucial body systemthat cannot be overlooked. as with the respiratory system, we will beginour discussion of the circulatory system by

identifying the structures within the system,we will examine our blood and its components, and we will conclude with information pertainingto the functions of the circulatory system. the best place to start when examining thecirculatory system is the heart. when discussing the anatomy of the heart, we begin by dividingthe heart in to a right and left side. (because the heart sits at a slight angle within thebody, the line we drew is not completely vertical.) each side of the heart has two chambers. thesuperior chamber on each side is called the atrium. we differentiate between the two bythe side on which each respective atrium sits. thus, we have a right atrium, as well as aleft atrium. the inferior chambers of the heart are the ventricles. as before, we differentiatebetween the two by referring to the right

and left sides, resulting in a right ventricleand a left ventricle. these chambers within the heart are separatedby a series of valves that prevent blood from flowing backward. the tricuspid valve liesbetween the right atrium and the right ventricle. the pulmonary valve is between the right ventricleand the pulmonary artery (which we will identify in just a bit). on the left side of the heart,the left atrium and left ventricle are separated by the mitral valve. the aortic valve thenlies between the left ventricle and the aorta (which we will be identifying soon as well).essentially, deoxygenated blood enters the heart from the rest of the body through theright atrium. from the right atrium, the blood moves into the right ventricle where it ispumped out through the pulmonary arteries

to the lungs. oxygenated blood returns fromthe lungs through the pulmonary veins into the left atrium. from the left atrium, bloodenters the main pumping chamber of the heart, the left ventricle, where the blood is thenpumped out to the rest of the body. now, do not worry if that description wenta little fast. we will be discussing the functioning of the heart and its chambers in much greaterdepth in a different module of this course. the heart also has an electrical system withwhich the emt must be familiar. the heart’s electrical system will be a topic of discussionin another module as well. for the time being, just know that the heart has four chambers:the right atrium, right ventricle, left atrium, and left ventricle.when we discussed muscles before, it was said

that the heart is such an important musclethat it has its own blood supply. while the heart itself is filled with blood, the bloodwithin the heart does not supply the muscle of the heart with oxygen. rather, the heartreceives its supply of oxygen through the coronary arteries. the red arteries on thiscomputer model are the coronary arteries. these arteries branch off from the aorta toprovide the heart with fresh, oxygenated blood. they are labeled right and left based uponthe side of the heart to which they supply blood. when someone has a heart attack, itis commonly due to a blockage in a coronary artery, which reduces or stops the flow ofblood (and, as a result, oxygen) distal to the blockage.by definition, arteries are the vessels that

take blood away from the heart. there aretwo main arteries that leave the heart. the first is the pulmonary artery, which takesoxygen-depleted blood from the right ventricle to the lungs. because blood returns to theheart from the body through the right atrium, into the right ventricle, and then throughthe pulmonary artery before going to the lungs to exchange carbon dioxide for oxygen, thepulmonary artery is the only artery in the body that carries oxygen-depleted blood.the other main artery leaving the heart also happens to be the largest artery in the body.it is the aorta. once blood is oxygenated in the lungs, it returns to the heart throughthe left atrium, into the left ventricle, and then into the aorta for distribution throughoutthe body. the aorta extends superior to the

heart, providing blood to the coronary artiesand the head before traveling inferiorly to provide blood to the rest of the body.beyond the aorta lie the remaining arteries. the anatomical locations of the main arteriesare important to know as these are the locations in which the emt will check for a patient’spulse. the carotid arteries (one on each side ofthe neck, left and right) supply blood to the head and its organs. they are locatedon the neck, inferior to the jaw, lateral to the thorax.the brachial artery is located in each arm, on the anterior crease of the elbow, alongthe medial aspect of the upper arm. this artery is commonly used for a pulse check on infantsand it is also the location for stethoscope

placement when taking a blood pressure.the radial artery is located on the anterior side of each wrist, proximal from the thumb.the radial artery is adjacent to the radius in the lower arm, thus its name. it is verycommon for ems providers to obtain a patient’s pulse by palpating the radial artery in eitherthe patient’s left or right wrist. there are two femoral arteries, one for boththe left and right legs. these arteries can be palpated in the crease between the abdomenand the groin. proceeding down the lower extremities, thereare two other pulse locations commonly used by ems providers. the first is the posteriortibial artery, which is on the posterior aspect of the medial malleous. (stated another way,it is on the inside of the ankle, toward the

heel.) the second is the dorsalis pedis artery,which is on the dorsal part of the foot (the top), lateral to the large tendon of the bigtoe. these arteries exist in both the right and left leg, and they are commonly palpatedto confirm circulation to the lower extremities. as the arteries extend from the heart, theynarrow in size. eventually, we reach the smallest branch of an artery, called an arteriole.these small vessels then lead to capillaries. when we discussed respiration and perfusionassociated with the respiratory system, capillaries were an important component. the pulmonarycapillaries are where the circulatory system meets the respiratory system. it is throughthese capillaries that gasses are exchanged between the air in our lungs and our bloodstream.the other capillaries in our body (not associated

with the lungs and alveoli) perform a similarfunction with the other cells in our body, exchanging gases, nutrients, and waste productsbetween the circulatory system and those cells. to accomplish this exchange, capillaries arevery small (the width of a single blood cell). with that gaseous exchange completed withthe cells of our body, the blood then enters the venous system. the entry point for whichis the venule, the smallest part of the vein that connects the capillaries to the restof the venous system. the network of veins throughout the humanbody is very similar to the network of arteries. if the arteries carry blood away from theheart, something has to carry it back. thus, wherever the arteries go, the veins must goas well. the veins close the proverbial loop

of the circulatory system. the veins returnblood from the extremities, torso, and head to the heart. when someone initiates an iv(intravenous therapy), they are accessing the circulatory system through the venous,not arterial, blood supply. ultimately, blood returns to the heart fromthe venous system through the vena cava. there is both a superior vena cava, which returnsblood from the head and upper body, and an inferior vena cava, which returns blood fromthe lower body and extremities. the blood from the vena cava enters the right atrium,where the blood begins its journey through the circulatory system once again.once the blood is infused with oxygen in the lungs, it returns to the heart through thepulmonary veins. because the pulmonary veins

return to the heart from the lungs, they arethe only veins in the body that carry oxygenated blood. all other veins return to the heartwith a depleted oxygen supply. (when looking at illustrations of the circulatory system,arteries are typically drawn as red because the blood they carry are oxygen-rich, thusmaking the blood a bright shade of red. veins, on the other hand, carry blood saturated withcarbon dioxide instead of oxygen, resulting in a much darker red color. veins look blueunder our skin, so veins are typically illustrated as being blue in color. the pulmonary arteriesand veins are colored inversely to what other arteries and veins are colored given theirposition between the heart and the lungs.) the last vital component to the circulatorysystem is one with which everyone is familiar,

our blood. blood is responsible for movinggasses, nutrients, and waste products through the body. if the circulatory system is thebody’s plumbing system, the blood is the fluid that fills it.our blood is composed of several different types of cells; all of which have a specificfunction. red blood cells, or erythrocytes, carry oxygenand carbon dioxide. the shape of the cells is vital in carrying these gasses. sicklecell disease, for instances, is a disease where the red blood cells are deformed, thusreducing the ability to carry oxygen and carbon dioxide. red blood cells are also responsiblefor giving blood its red color. also known as leukocytes, our white bloodcells are essential in keeping us healthy.

these specialized cells produce antibodiesthat help us resist infection. white blood cells also destroy invading microorganisms(germs) as well. there are five primary types of white blood cells. at this point in thecourse, however, it is not necessary to know the names and function of each.platelets are very important in that they have the ability to release a chemical knownas a clotting factor. as the name implies, these clotting factors are responsible forproducing blood clots. clotting is important in stopping bleeding from cuts, scrapes, andother trauma. without platelets and clotting factors, even a small laceration could proveproblematic as there would be no way to stop the bleeding. these clots produce scabs, underwhich the body grows new skin. in some instances,

these clotting factors can be a major problemif they accumulate in an area within the blood supply. we will discuss many of these conditionslater in the course. approximately 45% of our blood is comprisedof these three cells (about 44% is red blood cells and 1% or less are white blood cellsand platelets). the remaining portion of our blood is called plasma. plasma is a watery,salty, yellowish, somewhat translucent fluid that carries the red blood cells, white bloodcells, and platelets throughout our body. located in the upper left quadrant of theabdomen, toward the lateral aspect of the body, is the spleen. (the spleen is part ofthe lymphatic system, which is commonly considered to be part of the circulatory system. whilewe will not be discussing the lymphatic system

as it plays little role in the practice ofemergency medicine, the spleen is a special organ with which the emt must be familiar.)the spleen supports the body’s immune system and also serves as a reservoir for blood.it is a very vascular organ, about the size of your palm. while very well protected withinthe rib cage by bones, the spine, and muscles, it is also considered to be the body’s mostfragile abdominal organ. injuries to the spleen are typically a result of blunt or penetratingtrauma. such injuries can result in tremendous internal bleeding from the spleen, posinga true emergency for the patient if significant injury was sustained.now that we are familiar with the structures that comprise our circulatory system, someof the functions performed by the circulatory

system should not be a surprise.the circulatory system is responsible for the movement of nutrients, gases, and wasteproducts throughout our bodies. through the process of cellular respiration, we are ableto exchange gasses between the cells in our bodies and the red blood cells within thecirculatory system. where the circulatory system meets the respiratory system, diffusionallows us to exchange those gasses with the air in our lungs.the circulatory system also provides a reservoir for blood. an adult carries approximatelyfive liters of blood within his or her circulatory system, which can accommodate instances inwhich some blood is lost, typically due to trauma or some type of internal hemorrhage.that additional blood, that reservoir, allows

our bodies to compensate when blood volumeis lost. (as more blood is lost, however, our bodies lose the ability to adequatelyperfuse to the periphery and, eventually, vital organs. this type of emergency willbe discussed later in the course.) as mentioned with the respiratory system,the circulatory system also plays a part in regulating the body’s acid-base balance.through mechanisms known as the bicarbonate and phosphate buffer systems, our circulatorysystem works to ensure a healthy ph balance within the body. unlike the respiratory system,it takes longer for the circulatory system to regulate ph. on the other hand, the effectsof the blood buffer system on ph within the body are much more persistent; it lasts longer.the white blood cells within the circulatory

system are integral to infectious responseand our platelets are responsible for coagulation. together, the blood and the organs of thecirculatory system ensure the health of the body’s cells through these various and importantfunctions. the next major body system to analyze is thenervous system. the nervous system is broken down into twoprimary components. the first is the central nervous system, which includes the brain andspinal cord. everything else branches off from the central nervous system and is a partof the peripheral nervous system. within the peripheral nervous system are sensory andmotor nerves that help the body interact with its environment.our nervous system performs several vital

functions for the body. the first is referredto as autonomic control or response. these are the things our bodies do without any consciousthought. we do not need to think to breathe or to blink our eyes, for instance. this isall automatic. this autonomic control is integral in the body’s fight-or-flight and feed-or-breedresponses with the sympathetic and parasympathetic nervous systems, which we will be discussingin a few moments. the central nervous system is the center ofour consciousness, our thoughts, personality, and essential being. located within the brainare areas for logic, language, intuition, reasoning, and analytic thought, to name afew. this is why brain injury, from trauma, a stroke, or some other disease process canbe so debilitating as such injury has the

potential to strike at the very core of theperson’s own identity and abilities. within our consciousness is also something calledthe reticular activating system, which is responsible for regulating our sleep-wakecycle and also plays a part in transitioning between periods of conscious relaxation andheightened attention. while not an all-inclusive list, the reticular activating system is acomplex mechanism that has been linked to schizophrenia, narcolepsy, depression, autism,alzheimer’s, parkinson’s, attention deficit, and post-traumatic stress pathologies.the nervous system allows us to receive feedback from the environment in which we live throughthe body’s senses of hearing, smell, taste, sight, and touch. sensations of both pleasureand pain have cursory effects on the other

parts of the central nervous system, whichcan trigger the sympathetic or parasympathetic nervous systems, impact our consciousness,and provoke an involuntary motor response (which just so happens to be the last functionof the nervous system that needs to be identified). motor function, that is the flexion or relaxationof skeletal muscles to produce movement, is a function of our nervous system as well.while these functions are listed separately, they are all related and, in many instances,interdependent. sensory input, such as an alarm clock, can trigger the reticular activatingsystem to wake us from sleep. during that process, the person may consciously decideto stretch, thus triggering a motor response. when the person realizes that she hit thesnooze button once too many times, there is

a sympathetic response when she realizes sheis late for work. within a few moments, however, she realizes it’s a saturday and the alarmshould not have been on in the first place, triggering the parasympathetic nervous systemand, if she’s lucky, the reticular activating system that allows her to grab an extra hourof sleep. to understand how the nervous system performsautonomic functions, it is important to have familiarity with the sympathetic and parasympatheticnervous systems. the sympathetic nervous system is responsiblefor what is known as the “fight or flight” reaction. it is the system that kicks in whenwe are threatened or when we need to be aggressive. stated another way, this is the system thathelps our bodies respond to stress. it is

the system responsible for that “jolt”you feel when you narrowly miss being in a car accident, go bungee jumping, or becomeinvolved in an altercation. this response is designed to heighten our senses and improvethe ability to respond for the sake of preserving ourselves. this is a primal response thatdoes not even involve the brain. in simple terms, this is the body’s gas pedal. pushit and the engine revs up. at the emt level, it is not necessary to knowthe fine intricacies of how the sympathetic nervous system works. on a simplistic level,our body receives feedback from the environment that activates neurons in the spinal cord(within the t1 to l2 region). these signals proceed through bundles of nerves, known asganglia, to various target organs. of great

importance is the effect on the endocrinesystem. the sympathetic nervous system directly stimulates the adrenal medulla (in the adrenalgland, located on top of the kidneys). this causes the release of the hormones norepinephrineand epinephrine into the circulatory system. where the nerves of the sympathetic nervoussystem do not reach, the hormones do, and these hormones have a direct impact on ourcirculatory and respiratory systems. when active, the sympathetic nervous systemrecognizes the need for the body to respond quickly. as a result, blood flow is increasedto vital organs and decreased to those that are less vital to immediate survival. oureyes dilate to receive more light; our heart rate increases to move more blood and, subsequently,more oxygen to our muscles; the bronchi relax

to allow for greater air exchange into andout of the lungs; and, the liver converts an increased level of glycogen to glucose(to supply additional sugar to the brain and active muscles). inversely, the digestiveand renal systems slow down substantially (the last thing you need to do when fightingor running for your life, so to speak, is stop for a bathroom break).if we called the sympathetic nervous system the body’s gas pedal, the the parasympatheticnervous system would be the brake. this is the system that turns off the sympatheticnervous system. it is also the system that works to regulate vegetative functions, suchas maintaining a normal heart rate or blood pressure. because this system slows us down,so to speak, it is often referred to as the

“feed or breed” system.while we have not talked a great deal about how nerves function, it is important to knowthat chemicals are used as neurotransmitters to transmit messages from nerve cell to nervecell. in the case of the sympathetic nervous system, those chemicals are norepinephrineand epinephrine. in the parasympathetic nervous system, however, the chemical used as a neurotransmitteris acetylcholine. when activated, impulses originating from the brainstem and the neuronsin the s2 to s4 spinal cord travel throughout the parasympathetic nerve fibers (using acetylcholineas a neurotransmitter) to facilitate the processing of food, energy absorption, relaxation, andreproduction. the effect is obviously quite the oppositeof the sympathetic nervous system. with the

parasympathetic nervous system in control,our heart rate slows, blood pressure is reduced, pupils constrict, and digestive system activityincreases. thus far, every body system discussed hasbeen labeled as important or integral to the body’s functioning, and the nervous systemis no exception. our next body system is the integumentarysystem, which is ultimately a very fancy way of describing our skin.our skin is actually considered to be an organ, and it is the largest organ in (or, arguably,on) our bodies. the skin is comprised of three major layers. the first is the outermost,called the epidermis. the skin cells within the epidermis divide rapidly, resulting inthe movement of skin cells up, away from the

body. as the cells progress away from theskin’s blood supply, those cells die and are eventually shed away from the body. believeit or not, the skin we see with our eyes are actually dead skin cells that will soon (withintwo to four weeks) be washed or brushed away to be replaced by other dying cells. thisprocess helps protect the body against bacterial infection as the outermost skin layer is constantlymoving cells out away from the body. note that there are no nerves or vasculature withinthe epidermis. the prefix “epi” is derived from a greekpreposition meaning, on, above, or over. thus it makes sense that the epidermis sits abovethe dermis, the skin’s second major layer. the dermis is far more busy, if you will,than the epidermis. within the dermis are

blood vessels, nerve endings, glands, andother structures. given the existence of these structures, injuries exposing the dermis canlead to significant bleeding, intense pain, and infection. it is within the dermis thatour bodies will begin an assault on foreign materials, including organisms and damagedcells, with the white blood cells within our immune system. it is also the area where plateletswithin the circulatory system will work to repair damage to the skin, such as cuts andabrasions. the dermis is also the layer that experiences the most degradation over time.as we age, our glands produce less sweat and natural oils, thus drying out the skin; then,some of the vasculature within the dermis is lost, and the skin becomes thinner andmore prone to injury.

the innermost layer of the skin is calledthe subcutaneous layer. this layer contains fatty (also called adipose) and soft tissue.it, too, is rich in blood supply, nerves, and other structures, just like the dermis.injuries that extend down to the subcutaneous skin layer (or beyond, for that matter) areprone to infection, are associated with significant pain, and can generate a great deal of bleeding.if not evident thus far, one of the primary purposes of the skin is to protect the bodyfrom infection. the skin is a protective envelope for our bodies. it is our first line of defenseagainst bacteria, viruses, foreign bodies, and other microorganisms that would harm us.additionally, the skin serves a significant role in regulating the body’s temperature.the subcutaneous layer provides a great deal

of insulation. heat passes through this layerof the skin three times slower than it does through muscle or the other layers of theskin, which helps conserve body heat. the sweat glands within the skin also help coolthe body through the evaporative process (the evaporation of sweat on the skin helps coolthe body). while arguably not an essential function, the skin also serves at the basisfor what we consider to be appealing or beautiful. unfortunately for some, the skin can alsobe the basis for bias and prejudice given ethnic variations in skin pigmentation andother features. because sight is such an important sense for human beings, our skin is one ofthe first things people notice about us; it presents us to the world. as an ems student,you will eventually learn how to form an initial

impression on your patient’s condition based,in part, upon how the patient’s skin looks. next on our list is the digestive system.the purpose of the digestive system is pretty simple, it supplies our bodies with nutrients.we consume food and drink, the digestive system absorbs fats, proteins, carbohydrates, vitamins,minerals, and other nutrients, and it then dispels of the waste.food and beverages enter the body through the mouth and oral cavity. processing of ourfood begins right away as we chew the food, which is mixed with saliva.as we swallow, our food and drink hopefully bypass the trachea, which leads to the lungs,and enters the esophagus, a smooth-muscle tube that carries food down into a holloworgan known as the stomach.

the environment within the stomach is nota pleasant one. protected by a layer of mucous, the stomach mixes our food with hydrochloricacid and enzymes to produce a thick fluid called chyme. while we are discussing thestomach, please take note of its location within the body. the stomach lies in the upperleft abdominal quadrant. this is important because patients will often complain of “stomachpain” when the pain is located somewhere else in their abdomen, nowhere near the stomach.from the stomach, the chyme is passed through a tube called the duodenum before it findsits way into the bowels. while in the duodenum, chyme is mixed with bile, which is producedby the liver and stored in the gallbladder, and pancreatic digestive juices. these substanceshelp the body break down the food even further,

while also increasing the ph of the chymeso that it is less acidic. once in the small intestines, the nutrientscontained within the food are absorbed through the intestinal wall into the bloodstream,where a pass is made through the liver to detoxify the blood before distribution throughthe remainder of the circulatory system. thus, the liver not only produces bile to assistin digestion, but it also serves as a filter for the blood, removing toxins (such as alcohol)that enter through the digestive process. the liver also removes damaged red blood cellsfrom our system, which are then used to make bile.after the small intestines are the large intestines. during this part of the journey, bacteria(intestinal flora, as they are sometimes called)

assist in releasing vitamins and fluid whilethe bowel absorbs that fluid back into the blood stream. anything left over becomes wasteproduct (stool or feces) that is passed outside the body through the rectum and anus duringexcretion/defecation. one additional structure in the digestivesystem with which an emt must be familiar is the appendix (or vermiform appendix, ifyou want to be proper). located in the lower right quadrant, the appendix is believed tohave served an evolutionary purpose that no longer exists by housing bacteria that brokedown cellulose molecules found in plants. whether or not that is the actual case isirrelevant when a patient is complaining of abdominal pain in that area as appendicitiscan prove to be a significant medical emergency.

that will be discussed more in a later module,though. as you may have noticed, some of our organsare considered to be parts of multiple body systems. the lungs are respiratory, but theyalso have a circulatory component. our oral cavity is used by the both the respiratoryand digestive systems. if there is one system in particular that seems to have numerousorgans that also serve a role in another system, it would be the endocrine system.the endocrine system is a system that regulates bodily functions through the use of chemicalscalled hormones. we have many organs, usually called glands, responsible for producing thesehormones. the testes and ovaries, collectively referred to as gonads, regulate the male andfemale reproductive systems, respectively.

the pancreas regulates our blood sugar andwill be discussed in greater depth in just a bit. we have some familiarity with the adrenalglands as they work with the sympathetic nervous system. they also serve a role in regulatingwater and electrolyte levels within the body. the thymus gland is integral in the developmentof our immune system. the thyroid (medial) and parathyroid (lateral) glands regulatemetabolic rate and blood calcium levels. the pineal gland regulates our body’s internalclock, known as our circadian clock or circadian rhythm. the pituitary gland, though small(about the size of a pea) is powerful in that it governs some of the functions of many otherglands. it is also regulates or impacts our growth, metabolism, blood pressure, reproductiveorgans, water balance, and thyroid gland function,

to name a few.as ems providers, there are a few organs in the endocrine system that are of particularimportance. the first such organ is the pancreas. located posterior to the stomach, restingsuperior to the bowels, the pancreas is important because it plays a very important role inthe regulation of blood sugar. as we will discuss in a few slides, sugar is vital tothe proper functioning of our cells and, thus, our bodies. the pancreas works in regulatingour blood sugar by producing two critical hormones, glucagon and insulin.glucagon is a hormone responsible for breaking down glycogen, a complex carbohydrate, intoa simpler form of sugar, or glucose. by breaking glycogen down into individual glucose molecules,glucagon increases the blood sugar concentration

within the blood stream. because the liveris the largest and heaviest organ in the body, and an average liver can store five to eightpercent of its weight as glycogen, a lot of the work being done by glucagon is in theliver. in addition to breaking down glycogen into glucose, glucagon also stimulates theliver into breaking down proteins and fats into glucose as well. one of the skills youwill be learning as an emt is how to administer glucagon to a person suffering from hypoglycemia(low blood sugar). in administering this medication, the emt is hoping to raise the patient’sblood sugar by converting stored glycogen in the liver into glucose.in addition to increasing blood sugar concentration through the release of glucagon, the pancreasalso produces a hormone called insulin that

is responsible for lowering a person’s bloodsugar. imagine, for a minute, that your cells have little doorways in their membrane wallsthat allow sugar to pass into the cell. insulin is essentially the “key” for those doors.when introduced into the bloodstream, insulin increases the uptake of glucose into our cells,thus resulting in a decrease of the concentration of glucose within the bloodstream. insulinalso promotes the creation of glycogen, protein, and fat to store energy within the body. youwill delve into greater detail regarding diabetic emergencies and complications later withinthis course. while already discussed as part of the sympatheticnervous system, the adrenal glands deserve special recognition within this endocrinesystem discussion given their importance in

the functioning of the sympathetic nervoussystem by the production of the hormones norepinephrine and epinephrine.as a quick refresher, norepinephrine and epinephrine are neurotransmitters that engage the sympatheticnervous system. these hormones are released from presynaptic cells for activation of receptorsin post synaptic cells. within the lungs, norepinephrine and epinephrine activate whatare known as beta 2 receptors in the lungs that stimulate the bronchioles to dilate,thus allowing more air into the lungs themselves. the receptor sites in the heart are calledalpha 1 receptors. when activated by norepinephrine and epinephrine, the alpha 1 receptors inthe heart increase the heart rate and the force of contraction, which results in moreblood and, by extension, more oxygen, being

moved around the body to fuel our organs forthat ever-so-vital fight or flight response. the renal system is also called the urinarysystem. comprised of four primary structures, the kidneys, ureters, bladder, and urethra,the renal system is designed to primarily regulate fluid and electrolyte levels in thebody, filter chemicals from our blood stream, and also maintain the acid-base balance withinthe body. an average adult will excrete 1.5 liters ofurine per day. if a person is dehydrated, the renal system will compensate by retainingfluid, thus reducing the frequency of urination and quantity of urine expelled. inversely,what happens when you drink a lot of fluids over a short period of time? the renal systemincreases urine production, resulting in much

more frequent urination. the kidneys managethis by regulating the flow of electrolytes, such as sodium (salt), bicarbonate, potassium,hydrogen, and chloride. in managing hydrogen in particular, the kidneys help to ensurea proper acid-base balance within the body. for lack of a better term, the kidneys serveas filters for our bloodstream. the kidneys filter all the blood in our circulatory systemapproximately 60 times a day, which makes them very efficient at removing waste productsin the blood. these waste products are commonly a substance called urea, which is the substanceresponsible for giving urine its yellow color. the kidneys are also responsible for removingother toxins, including drug metabolites, which is why individuals on certain prescriptionmedications must have their kidney function

monitored routinely to ensure the kidneysare not being damaged by the medication. the renal system also helps to manage ourblood sugar by excreting glucose in our urine if the concentration of glucose in the bloodexceeds a certain threshold and it even plays a part in regulating our blood pressure bycontrolling the fluid levels within the body and releasing an enzyme called renin thatultimately results in elevating our blood pressure.if not already evident, the urethra is shorter in women than in men given that it must passthrough the male penis. as a result, women are much more susceptible to bladder and urinarytract infections than men. the last body system we need to cover is thereproductive system.

by its very name, it should be evident thatthe main purpose of the reproductive system is reproduction, the making of babies to ensurethe survival of the species. the reproductive system also serves an additionalpurpose by producing hormones that affect our emotions, mood, and physical development.ovaries in females produce estrogen, which is essential in the development of secondarysexual characteristics, such as breasts, and the regulation of the menstrual cycle. estrogencan also accelerate the metabolism, increase fat stores, and increase bone formation. menalso have low levels of estrogen in their bodies (compared to women) given some productionin the liver and adrenal glands, which serves various functions related to the male reproductivesystem.

in men, the testes produce testosterone, whichis vital to the development of male reproductive organs. testosterone also contributes to increasingmuscle mass, bone mass, and the growth of hair. women also have low levels of testosteronein their systems (approximately seven to eight times less than men) given some productionin the ovaries and adrenal glands. lastly, given the inclusion of the urethra(part of the renal system) within the penis (a reproductive organ), the male reproductivesystem is also involved in the process of urination.as the reproductive systems vary between men and women, we will look at each independently.beginning with the female reproductive system, we will first identify the ovaries. theseare the female sex glands. they produce the

hormones estrogen and progesterone. they arealso responsible for the development and release of eggs for reproduction.the fallopian tubes, also called uterine tubes, are thin, flexible tubes that extend fromthe ovaries to the uterus. the purpose of these tubes is to deliver the eggs producedin the ovaries to the uterus. if fertilization of an egg occurs, it usually does so whilethe egg is still in the fallopian tube. if the fertilized egg fails to move down intothe uterus, an ectopic pregnancy will result. this is a significant medical emergency thatwill be discussed in greater depth later in this course.the uterus is where fetal development occurs. it is a hollow, thick-walled, muscular organsuperior to the vagina.

the vagina is located just below the uterusand serves several purposes. it receives the penis during intercourse, it provides a routefor the discharge of menstrual blood and tissues, and it is also called the birth canal as itis the final passageway from the uterus to the outside world for a baby during delivery.lastly are the external genitalia. structures such as the perineum, mons pubis, labia, andclitoris protect the opening to the vagina and serve a role in sexual functioning.while not absolutely essential in the process of reproduction, female breasts are commonlyincluded within the reproductive system as they do assist in the reproductive processby producing stimulus to both the male and female in varying degrees during the reproductiveprocess. the breasts also contain mammary

glands that provide breast milk (nourishment)to newborns and infants. as women age, ovarian function diminishes,menstrual periods cease, external genitalia (the labia and clitoris) become smaller, thevagina narrows and shortens, the lining of the vagina becomes thinner and dry, and theovaries and uterus decrease in size. by comparison, the male carries his sex glands,his testes, on the outside of his body within a muscular sac known as the scrotum. the testesproduce hormones and, most importantly to reproduction, sperm. sperm produced in thetestes is stored in the epididymis until needed. during intercourse, sperm moves from the epididymisthrough a tube called the vas deferens to an area in the prostate gland where the spermis combined with seminal fluid to produce

semen. the semen is then routed into the urethra,located within the penis, for ejaculation. the penis itself is a spongy organ that, whenengorged with blood, becomes erect. as you may notice from the diagram, the urethrapasses from the bladder through the prostate gland, before entering the penis. as a result,an enlarged prostate can lead to urinary problems in men, which typically becomes more commonwith age. along those lines, men also experience a reduction in the size of their penis andtheir testes hang lower in the scrotum as they age.given that you should now have some understanding of the systems within the body, their structures,and functioning, we can now talk about something known as the life support chain.combined, the circulatory and respiratory

systems form the cardiopulmonary system. theproper functioning of this system creates something called the life support chain. solong as all the elements of the chain are in place, the organism should continue living.remove an element of the chain, however, and death is inevitable.there are three main components within this life support chain: oxygenation, perfusion,and the cellular environment itself. focusing on oxygenation, our first primaryconcern is being able to exchange gases in the lungs. this means the body must be ableto breathe, to ventilate itself, moving atmospheric air (containing 21% oxygen) into and out ofthe lungs. given this supply of air in the lungs, it is then necessary for gas exchangeto occur within the alveoli. oxygen from the

air must diffuse into the alveolar capillariesand carbon dioxide must diffuse from the alveolar capillaries into the air within the lungsto be exhaled. even if this process is working within the lungs, we must also recognize theneed for cellular respiration throughout the body. our cells must expel carbon dioxideinto the bloodstream so there is room, so to speak, for oxygen to enter. inherent inthis process is also the fact that the circulatory system is working; that the heart is pumpingblood throughout the body. having this gaseous exchange occur at the cellular level or withinthe alveoli is no longer beneficial if the blood in those locations does not make thetrip throughout the body. the freshly oxygenated blood in the lungs needs to move to the cellsto deliver that oxygen, and it needs to return

to the lungs to expel the waste carbon dioxide.within that process, perfusion into the individual cells of the body is important. within thiscontext, perfusion means the ability to move gases and nutrients between the bloodstreamand the cells. we obviously want oxygen to enter the cells and carbon dioxide to leavethe cells. we also need glucose (sugar) to enter the cells as well. for that to happen,our body needs insulin to open the proverbial door into the cell for the glucose. our cellsalso produce other waste products that must be removed as well, otherwise the cells willdie in their own waste. these are all important components of adequate perfusion into thecells. lastly, we need to look at the cellular environmentitself. up to this point, we have not discussed

how the cells within our bodies actually work.the cell is the basic building block within the body. cells form tissues, which form organs,which forms systems, that eventually result in the full organism or, in our case, thehuman body itself. ultimately, our cells are living things. they need energy to do work,and they need a way to expel the waste products produced by doing that work.within a healthy environment, our cells have an ample supply of oxygen. when a cell isproducing energy with oxygen, it is said to be functioning with aerobic metabolism. inaerobic metabolism, the cell has ample oxygen that allows it to break sugar down into achemical called adenosine triphosphate (atp) very efficiently. given the inclusion of oxygeninto the process, the cell can produce a great

deal of energy with the rather innocuous byproductsof water and carbon dioxide. when the cells are deprived of oxygen, however,they enter into a state knows as anaerobic metabolism. without oxygen, the cells cannotprocess glucose very efficiently, resulting in low atp (low energy) production and thewaste product of lactic acid. if a supply of oxygen is not restored to the cell, itwill continue to function producing low energy and lactic acid until the ph of the cell becomestoo acidic and the cell dies. as more cells suffer the same fate, the tissues and organsin the affected area become compromised, which may very well threaten the health of the organism,the body, itself. from our discussion thus far, it may be clearthat the functioning of a single body system

is rather complex. as soon as it is apparentthat multiple systems rely on others, the complexity surrounding the functioning ofour bodies reaches an entirely new level. for this reason, the life support chain canbe a fragile thing and a break in one link of the proverbial chain can spell disasterfor the entire system. this life support chain relies on the air we breathe, a patent airway,the ability to ventilate, the ability to respirate, the movement of gasses throughout our bodies,the amount of blood in our circulatory system (especially when compared to the relativecapacity of the circulatory system itself), the health of the heart, and the maintenanceof the body’s acid-base balance. our life support chain begins outside thebody with the air we breathe. common ambient

air contains 21% oxygen, 78% nitrogen, and1% other gases. this 21% oxygen is of critical importance.a lack of oxygen in the air we breathe can have a profound impact on the body. the brainitself uses approximately 20% of the oxygen within the body and does not respond wellto a reduction in available oxygen. if we see a reduction of just 1.5% to 19.5% oxygenin the air, the ability to work strenuously is impaired; we may see coordination suffer;and, people who are unhealthy to begin with, such as those with circulatory or respiratoryproblems, may begin to experience symptoms associated with their disease. it is importantto keep in mind as well that, for every 1.5% of oxygen reduced in the air, approximately7.5% of other stuff takes its place (as the

oxygen is not only being displaced, but sotoo is the nitrogen). that which displaces the oxygen may have negative repercussionsfor the body on its own as well. thus, an oxygen deficient atmosphere, such as thatwhich exists in a confined space, typically brings a multitude of hazards.as the oxygen saturation in the air is decreased to 15%, coordination, perception, and judgmentis impaired. at 12%, our body can no longer provide enough oxygen to adequately perfuseour extremities, resulting in cyanosis (where the skin turns blue due to the lack of oxygen).the impact is even more pronounced at 10% with nausea, vomiting, mental failure, andunconsciousness. at 8%, half the people in that environment for eight minutes will bedead. (a quarter are dead after only six minutes.)

if the atmosphere has less than 6% oxygenin it, the person is dead within seconds. a patent airway is an established, affirmativeairway. it is an airway that works; an airway that allows us to move air into and out ofour lungs. if the airway is blocked or restricted, itbecomes difficult or impossible to exchange the air in our lungs with the ambient airin the atmosphere. a person choking or suffering from asthma would be an example of an airwayproblem. if we are unable to bring air into the lungs, there is no oxygen available withinthe lungs to enter our bloodstream. somewhat related to having a patent airwayis the ability to ventilate, the ability to physically move air into and out of the lungs.having a patent airway does no good if the

person is unable to breathe on his or herown. have you ever fallen on your back and had the “wind knocked out of you?” thatuncomfortable feeling of not being able to take a breath is actually a result of a diaphragmspasm. if the diaphragm is not working, ventilation becomes a significant challenge.there are other things that can cause a ventilation problem as well. a neurological disorder ortrauma to the spinal cord may disrupt the impulses that prompt our diaphragm to constrict.a drug overdose, especially of a narcotic substance, may depress the body’s centralnervous system to the point where it no longer remembers to breathe, resulting in death.a pneumothorax (a collapsed lung) can greatly reduce the ability to move air as well.a crushing injury, such as a heavy object

on the chest, may not allow for chest wallexpansion, which would negatively impact the ability to ventilate. if you have ever beensnorkeling, does it feel harder to breathe through the snorkel tube? the reason is becausewater has weight (approximately eight pounds per gallon). as you place water on top ofyour body, it reduces the ability to expand your chest, just like any other heavy object.for more proof, take the same snorkel and breathe through it without being in the water.you should be able to breathe without a problem. the deeper you go in the water, however, themore difficult it is to breathe, which is why snorkels have a limited length. scubadivers can breathe regulated air under water because that air is pressurized; it pushesthe lungs open and overcomes the tremendous

pressure placed on the thoracic cavity bythe water above the diver. this is also why it feels more difficult tobreathe at higher altitudes. the process of creating negative pressure in the thoraciccavity is not that difficult at high altitudes. the problem, though, is that the air (or barometricpressure) is less, meaning that the air has less push into our lungs. as a result, the“push” of oxygen into our blood stream through the alveoli is not as great, meaningwe have to work harder to saturate our bodies at higher altitudes where there is less airpressure than at lower altitudes where there is more air pressure.trench rescue is a special discipline in which victims are rescued (or recovered) from trenchesthat have collapsed. falling dirt has weight

and just three inches of dirt on top of aperson’s chest is enough to overpower the body’s muscles of ventilation. even witha patent airway and readily accessible ambient air with 21% oxygen, the ability to ventilate,to move that air into and out of the lungs, is absolutely critical.assuming the air has 21% oxygen, our airway is patent, and we are able to move that airinto the lungs, we still have to move the oxygen in the air into our bloodstream. thatprocess begins in the alveoli. damaged alveoli, due to diseases like pneumonia, emphysema,or asbestosis can greatly reduce the ability to exchange gases through the alveolar wall.having an adequate supply of blood to the lungs is important as well. a blockage ina pulmonary artery, called a pulmonary embolism,

can be just as bad as air not entering thelungs in the first place. depending on the size of the embolism, a great deal of thelung may lose its capacity to exchange gases because there is no blood flowing to thatarea of the lung. once the oxygen is in the bloodstream, wemust also be able to move the gases between the capillaries and the individual cells.within the cell, it is also imperative that the cellular environment contain the electrolytesand nutrients necessary to function, including glucose.using the words respiration and perfusion interchangeably, if we ventilate adequately,but do not perfuse, or are perfusing without adequate ventilations, we have what is knownas a ventilation/perfusion mismatch. v/q mismatch

(where v equals ventilation and q equals perfusion)is the terminology used to delineate a difference in the amount of oxygen-containing air inthe lungs and the amount of oxygen within the blood stream. air in the lungs does notmatter if it cannot enter the bloodstream (or the cells). inversely, being able to perfusedoes not matter if our lungs are somehow deprived of oxygen.just because the oxygen in the lungs is able to enter the bloodstream does not necessarilymean it is being carried where it needs to go. there are diseases, such as sickle cellanemia, that impair the ability of the body’s red blood cells to transport oxygen throughoutthe body. there are also gases, such as carbon monoxide, that can displace oxygen withinour bloodstream. thus, another important link

in the life support chain is the ability ofthe blood to carry oxygen, nutrients, electrolytes, and waste products.of equal importance to the life support chain is having adequate blood within our circulatorysystem. an adult human has about four and one-half to five liters of blood within hisor her circulatory system. (there is obviously some variance depending on the size of theperson and the textbook being referenced.) that same body can typically withstand a 15to 20% drop in blood volume (approximately one liter) before the life support chain issignificantly impacted. the body experiences different levels of hypovolemic shock between15 and 40% blood loss. at or beyond 40% blood loss, death becomes increasingly probable.we will talk about shock later in this course.

for the time being, however, know that thebody works to protect the organism by sacrificing, if you will, non-vital parts of itself. givensevere shock, the sympathetic nervous system shuts down the blood supply to extremities,trying to shunt as much blood (and, therefore, oxygen) as possible to the heart, lungs, andbrain. as the volume of circulating blood within a person dwindles, however, the lifesupport chain becomes more difficult to sustain. now picture, for a minute, the vessels ofthe circulatory system and the amount of blood they can contain at any one time. we alsohave organs, such as the liver and spleen, that contain reservoirs of blood as well.combined, that system holds up to five liters of blood. what would happen if our circulatorysystem (our arteries and veins, predominantly)

suddenly increased in size without increasingthe amount of blood to circulate within it? increase the size of the container withoutincreasing the volume of fluid within it and there is no longer enough fluid to fill thecontainer. systemic vascular resistance is a fancy wayof saying blood pressure. ultimately, we have to maintain a healthy blood pressure to maintainperfusion to our cells. our veins and arteries are lined with muscles that allow them toexpand and contract. this is what allows our sympathetic and parasympathetic nervous systemsto restrict or reestablish blood flow to a given area. our bodies function with manyof these vessels somewhat constricted. if we happen to lose too much blood or our vesselsall dilate at the same time, we can no longer

maintain a perfusing blood pressure; thereis not enough blood to fill is the vessels of our circulatory system. on the previousslide, we discussed how the loss of circulating blood volume negatively impacts the body.if we reduce the circulating blood volume, it is important for the body to be able toconstrict blood vessels to conserve blood for critical organs, such as the heart, lungs,and brains. whether we increase the size of the container or reduce the amount of fluidwithin the container, the result is the same… too little blood in the circulatory systemis problematic. just 23 days after conception, our heartsbegan beating and circulating blood. from that time until right now, your heart hasbeen maintaining the persistent rhythm of

muscular contraction and relaxation to moveblood around the body. so what happens if the heart begins to fail, as occurs with ageor a disease process? obviously, the heart is critical to the life support chain anda failing heart can quickly lead to the deterioration and eventual collapse of that chain. the failurecan be a gradual process, or something more catastrophic, such as sudden-onset myocardialinfarction (heart attack). one last item that can break the life supportchain is related to the functioning of the cell itself. more specifically, the acid-basebalance within the body and its cells. as we already discussed, cells produce energy.they do so by breaking down oxygen and glucose to produce adenosine triphosphate (atp). whenthe cells have access to oxygen, this process

is very efficient with a lot of energy produced.the byproducts are carbon dioxide and water. if the cells are starved of oxygen, however,they function anaerobically. this process produces substantially less energy and theultimate byproduct is lactic acid. as this lactic acid begins to build without a sourceof oxygen being established, the body itself becomes acidotic, meaning the acid-base balanceis shifting, making the body more acidic. this is called acidosis and it has a negativeimpact on the body. too much acid and the cell will die. how quickly depends on thearea affected, whether oxygen availability is simply reduced or is completely halted,the types of cells impacted, and the amount of time those cells have to function withreduced or no oxygen. brain cells, for instance,

are not at all tolerant of oxygen deprivation.remove oxygen from brain cells and they begin to die within six to eight minutes. on theother hand, skeletal muscles and tissues can survive a longer time, typically up to hours,without adequate perfusion. up to this point, we have covered some medicalterminology to facilitate our discussion about the structures within the human body. it isnow time to delve a little deeper in medical terminology to start pulling everything togetherand serve as a foundation for upcoming course modules.medical words are built from three different parts, if you will. there is a root word,which commonly refers to the organ, system, or tissues involved. the root is then joinedwith a prefix before the root, a suffix after

the root, or both. the prefixes and suffixesare designed to describe the root, to give it greater definition.within the medical field, there are numerous roots for virtually every part and componentof the body. for an ems provider, some of the most common are:cardi or cardium, which refers to the heart. neur, referring to a nerve or the nervoussystem. pnea, related to breathing.pneumo, referring to the lung. nas refers to nose or nasal.or refers to mouth or oral. hem or hemat refers to the blood.osteo refers to bone. arthr refers to joints.myo refers to muscles.

prefixes are added to the beginning of rootsto modify or qualify their meaning. some common prefixes include:hyper, for fast, high, or above normal. hypo, for slow, low, or below normal.tachy, for rapid or above normal rate. brady, for slow or below normal rate.dys is difficult or painful. a is without.cyan is blue. intra means inside or within.quad refers to four. bi refers to two.there are also suffixes, added to the end of roots, that complete their meaning. forinstance: ac or al means “pertaining to.”ology is the study of something.

ist refers to one who specializes in something.osis is a disease condition. ultimately, these prefixes, suffixes, androots are combined to form medical terms that have significant meaning for the healthcareprovider. for instance, adding tachy to cardi forms the word tachycardia, meaning a fastheart rate. neur and ology is neurology, the study of nerves and the neurological system.cardi plus ology and ist is cardiologist, one who specializes in the study of the heart.a is without and pnea is breathing. combining the two is apnea, or the absence of breathing.similarly, dys plus pnea is dyspnea, which means difficulty breathing.the list provided here is far from inclusive, and you may find yourself using other prefixes,roots, and suffixes with greater frequency

in your eventual practice of emergency medicine.the important takeaway from this slide is that, once you identify a common prefix, suffix,or root, its meaning does not fluctuate and you can use the combination of those threeword parts to describe patients, organs, diseases, tissues, signs, symptoms, and conditions.if confronted with a medical term that you do not understand, first see if you can breakthe word apart into its components (prefix, root, and suffix). for instance, hematomais a common medical word used in ems. hemat refers to blood and oma means tumor. thus,hematoma is a tumor (a swelling or growth) containing blood. hematoma is a fancy wayof saying bruise. when we delve deeper into medical terminology,one might wonder how these words developed,

how they came to be. ultimately, we go backto ancient rome and greece where the study of the human body has some recognized origins.when describing the body’s anatomical structure, we use latin words. other words pertainingto diseases, conditions, treatments, or diagnosis have greek roots. we also find that it ispossible to divide the terms up by their subject matter. some terms are associated with bodystructure, some are related to the body systems we already discussed, and others pertain tobody direction or position. for instance, epigastric and superficial aremedical terms related to the body’s structure. ocul refers to the eye and bronchiol refersto bronchial tubes, both are associated with body systems. bilaterial and flexion are termspertaining to the body’s direction or position.

at this point, including pertinent medicalterms and definitions would be counter-productive as there are so many of them. medical dictionariesare very thick books and there is not enough time in the day to cover all of the medicalterms you may encounter through your practice in ems. with that being the case, it is recognizedthat much of the medical terminology you will need to know as a newly-licensed ems providerwill be included within subsequent modules of this course. additionally, if confrontedwith a medical term to which you do not know the definition or meaning, you are encouragedto look it up. emt textbooks, medical dictionaries, and the internet are all readily availableresources for finding the definition of various medical terms.another factor to consider regarding medical

terminology is that you, as an emt, must rememberyour audience when using such terms. if you are giving a report to the hospital, theywill know what a myocardial infarction is. when speaking with a patient, however, thatterm may be completely foreign to him or her. speak in plain, lay person terms when dealingwith patients and the public. using a word like “epistaxis” may sound impressive,but the average person has no idea that word is medical terminology for a nosebleed. donot assume the patient knows what you mean when using medical terminology as communicationproblems can lead to errors in formulating a field impression and the delivery of properemergency care to that patient. additionally, do not go out of your way to use verbose medicalterminology when simple words or descriptions

will work just fine, even with other healthcare providers. the last thing you want when ensuring continuity of care for your patientis a communication problem because you used a fancy term incorrectly or the person towhom you were speaking did not understand the term and was embarrassed to ask for clarification.lastly, given the complexity and length of many medical terms, health care providerswill occasionally use abbreviations and acronyms in both oral communications as well as writtendocumentation. the problem with the use of acronyms and abbreviations, however, is thatthey are not always standardized or universally recognized between various health care providersand systems. true, there are some abbreviations and acronyms that are used by virtually everyone.some examples include:

chf for congestive heart failure.bvm for bag-valve mask. mi for myocardial infarction.cms for circulation, motion, and sensation. iv for intravenous.jvd for jugular vein distension. there are also numerous acronyms and abbreviationsthat that can mean multiple things. for instance: bs can be breath sounds, bowel sounds, orblood sugar. co routinely means complaining of, but canalso be carbon monoxide. min can refer to minutes as a measure of timeor can also mean minimum. hr is heart rate or hour.w/o can be wide open or without. if you are positive that an acronym or abbreviationis universally used and accepted within the

healthcare community, then its use in conversationor reports may be acceptable. on the other hand, using acronyms or abbreviations thatmay not be widely used or that require the receiver of the message to consider the acronymor abbreviation in context to know what you are saying or writing is not a good idea.additionally, if you make it a habit of using acronyms and abbreviations in your normalcommunications, you may do so as well when dealing with others outside the healthcareprofession, such as patients, their families, or the public at-large. if a patient cannotunderstand you due to the use of acronyms and abbreviations in your speech, that isa problem. lastly, many systems actually have protocolsthat define proper acronyms and abbreviations.

if you are using an acronym or abbreviationincorrectly, or are using an acronym or abbreviation that is not approved by your local protocols,that is also an area of concern. for these reasons, it is not a bad idea tocommunicate without using acronyms or abbreviations wherever possible. ultimately, follow yourlocal protocols and exercise some common sense in your communications with other professionalsas well as the lay public. with that, we are completed with this module.you should now be able to: identify the topographical anatomy and directionalterms utilized by the emt. list the components of each of the major bodysystems. list the elements of the life support chain.have acquired a basic understanding of common

latin medical terminology.that concludes this module on the overview of the human body and physiology. if needbe, do not hesitate to play this presentation again. please contact your course instructorwith any questions you may have regarding the material in this module.this presentation was created by waukesha county technical college with grant fundingfrom the wisconsin technical college system.