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The Human Body
Web www.EmergencyMedicalEd.com

The Human Body is a complex organization of cells.  These cells are organized into sheets of tissue, the tissue is organized into structures called organs, the organs are organized into organ systems and those organ systems are organized into an organism which we call "The Human Body."  Each system in the body serves to assist other systems for the good of the organism.  An understanding of the body's organ systems is important, if the EMT is to understand what can go wrong, should one of the systems be damaged or unable to function.  In this section we will go through the human body, discussing each system in as much detail as we feel is necessary in order to adequately familiarize you with the function of that system, and how it interrelates with other systems.  For the purposes of this course, we will discuss the Skeletal System, the Muscular System (referred to as the Musculoskeletal System, when it's interaction with the skeletal system is discussed,) the Respiratory System, the Circulatory System (sometimes referred to as the Cardiovascular System, when it does not include the Lymphatic sub-system,) the Nervous System, the Integumentary System, the Endocrine system, the Digestive System, the Urinary System, and the Reproductive System.

Before we begin our discussion of the various systems of the human body, we need to set some ground work regarding terminology.

Basic Terminology

This illustration depicts a position called the "Anatomical Position."  We will refer to it many times during the course of this website dissertation.  It represents the basis from which all directions and directional concepts will be developed.  In addition to the "obvious," please note, that the subject is standing with his arms at his side and the palms of the hands are facing forward.

There are five surfaces (sometimes referred to as "planes" or "aspects") that need definition.

The anterior surface of this subject's body is that surface that can be seen (the front,) and the posterior surface is that surface that can not be seen (the back.)  The midline is kind of self-explanatory.  It is a line drawn down the anterior (or posterior) aspect dividing the body into left and right halves.  There are four other such lines, (not illustrated here).  Two of which, are referred to as midclavicular (one left, one right,) which originate at the approximate midpoint of a bone called the clavicle (more about bones, later.) and define planes which are parallel to the midline and divide each half in half again.  The other two lines, referred to as midaxillary (again, left and right,) originate under the arms, an area referred to as the axilla.  They divide each half (as defined by the midline) into quarters.

There are eight pairs of directional concepts to define.  Left and right, always refer to the patient's left or right. To the left or right of the midline, moving away from it or back toward it, is a concept that defines lateral or medial. Lateral being farther from the midline, medial being closer to the midline.  Superior is closer to the head, than inferior which is closer to the feet (simply stated higher or lower.)  Proximal and distal refer to directions or relationships between different structures or aspects of the extremities (arms and legs.)  For example the elbow is proximal to the wrist, and the elbow is distal to the shoulder.  Superficial and deep are "measurements" of depth from the surface of the skin, and don't need much explanation.  Ventral and dorsal refer to the anterior and posterior aspects of the torso (generally used when the patient is not in the "anatomical position," or the "patient" is not customarily thought of as one who walks upright.)   Our "trick" for remembering which is which (ventral or dorsal,) is to picture a shark gliding through the water with it's "dorsal" fin exposed (that's the fin that is on the sharks "back.")  These two terms are also useful to describe aspects of the feet and hands, but more specifically the ventral (inferior) aspect of the foot is referred to as plantar and the ventral (anterior) aspect of the hand as palmar.)  Bilateral and unilateral are used to describe structures or occurrences in the body.  Eyes, for example are bilateral (one on either side of the midline,) whereas some organs are unilateral (the spleen.)  A patient might be a bilateral amputee (having lost both legs,) or might be experiencing unilateral paralysis secondary to a stroke.  Contralateral and ipsilateral  refer to the same side or different sides.  A patient might have pain that originates in an area just superior to the left ear, travels over the superior aspect of the skull and travels down the contralateral aspect of the upper torso. (pain starts just over the left ear, goes over the top of the head and down the right side of the body,) or may have sustained superficial burns to the medial aspect of the right upper extremity, with superficial and deep burns to lateral aspect of the ipsilateral lower extremity (superficial burns to the inside of the right arm and superficial and full thickness burns to the outside of the right leg.)  That's medical terminology, cool, Huh?

To help "locate" injury or pain in the abdomen, it has been divided into quadrants.  The quadrants are defined by the intersection of the midline and a horizontal line drawn through the umbilicus, dividing the abdomen into right upper (RUQ,) right lower (RLQ,) left upper (LUQ,) and left lower (LLQ) quadrants.

If a joint is designed to move, it can rotateflex or extent, abduct or adduct.  Rotation is a simple concept, but if it's one that you don't understand, shake you head "NO."  You just rotated the skull at the  Atlas (C-1) around the Axis (C-2.)  In general, flexion and abduction are movements away from the anatomical position, for example, bending the arm forward or leg backwards, or the trunk forward (away from the anatomical position) is flexion, and moving the legs or arms to the side (away from the anatomical position) is abduction.  Extension and adduction are movements back toward the anatomical position.  Two exceptions are the head and feet.  From the anatomical position, moving the foot upward is flexion (extension would be the opposite, "pointing your toes")  and moving the top of the head posteriorly would be extension (you've all taken CPR classes, and should understand the concept of "hyperextension.")

You need some terminology for the different positions in which patients may be found or transported.

Recumbent is lying down and erect is standing up. Prone is lying face down, supine is face up, and lateral is lying on the side.  A patient found "left lateral recumbent" is lying down on the left side.  Fowler's position is sitting with the knees slightly bent.  Some texts further break this position down into low Fowler's and high Fowler's depending on the amount of flexion added to the upper torso.  Trendelenburg's position is where the head is lower than the body and there is no flexion in the torso.  The shock position is where the feet are raised a few inches (according to local protocol) and the torso is slightly flexed at the hips (sometimes referred to as modified Trendelenburg's position.)  If the patient has a hip injury, this modified Trendelenburg's position should not be used, for obvious reasons.  Transporting a patient in the prone position is, from our experience, dangerous.  The patient's airway CAN NOT be maintained when a patient is transported while pronated, but it's important to know because the patient may be found lying prone.  The recovery position is left lateral recumbent (or "right" with sustained injury to the left side) with some flexion added to the extremities.

Decortication and decerebration are rather advanced concepts of positioning but you may find a patient in either and we feel that given the proper information, you should be able to recognize them.  Both are indications of profound brain damage, one being worse than the other.  At the "on-set" of this profound brain damage, the patient will decorticate (upper extremities flex toward the midline and lower extremities adduct. Both upper and lower extremities become rigid,) as the damage continues the patient begins to decerebrate (extremities flail away from the midline and abduct, and rigidity subsides.)  In the presence of either of these two positions, coupled with unresponsiveness, look for indications of head injury or rising intracranial pressure.

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The Skeletal System

There are 206 bones in the Human Body.  Don't believe us?  Start counting.

The skeletal system serves a couple of functions.  It provides shape to (and support for) the body, some parts of the skeletal system provide protection for vital organs, its lever system (in conjunction with the muscles) makes motion possible, and the "flat bones," (specifically, the ribs and sternum) are responsible for the production of red blood cells.

It's important to know the names of the major bones, or groups of bones, that make up the human skeleton because they are used to identify anatomical locations (or "regions") on the body.  In order to be able to identify areas of the skull, you would have to know the location of  the parietal bone, temporal bone, frontal bone, occipital bone, maxillae and mandible.  If the patient has sustained an injury to the face, it is probably more appropriate to use  descriptive terms like eyes, nose or mouth, and not as important to know the individual bones in the "orbit" (eye socket) or the individual "nasal bones." One exception would be the zygomatic bones (commonly referred to as "cheek bones") used to locate the zygomatic arch, a common landmark on the face.  The clavicle, sternum, scapulae, ribs, cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum, coccyx, and pelvis, help identify areas of the neck, thorax, upper and lower back. The femur, tibia, and fibula identify regions of the lower extremities, while the humerus, ulna, and radius do the same on the upper extremities.  The tarsals, metatarsals, and phalanges identify areas of the ankle and foot.  Carpals, metacarpals, and phalanges are bones that make up the wrist and hand, identifying anatomical areas on that part of the upper extremities.   If you were looking for a radial pulse, it's likely to be found near the radius (DUH!,), or a femoral pulse near the femur.  Or if the patient has a suspected fracture of the lower leg, it would sound far more professional (and add greatly to your creditability) to report a suspect fracture of the tibia/fibula.  If the patient has a broken jaw,  the medical terminology used to "describe" the jaw is "the temporomandibular joint" (TMJ,) that "place" where those two bones join, just in front of the ear.  That joint (as well as all joints)  is held in place by ligaments,  "cord-like pieces" of dense connective tissue that attach bone to bone.


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The Muscular System (Musculoskeletal System)

There are over 600 muscles in the Human Body (don't bother trying to count them, it's an exercise in frustration.)  Some muscles are very large, designed to perform heavy "work," like Quadriceps, Triceps brachi and Biceps brachi (can you guess what pulse we would find immediately below the Biceps brachi muscle?  Another DUH!,) others are very small like the extra ocular muscles that control eye movement, and some can barely be seen like the erector pili muscles that act to pull the skin hair erect causing "goose bumps" or "goose flesh. 

There are three different types of muscle tissue.  Striated/Skeletal muscle (Voluntary Muscle,) Smooth muscle (Involuntary muscle,) and Cardiac Muscle.  All muscles are capable of only one action, contraction, meaning that a muscle is capable of applying it's "work" in only one direction.  It does this by getting shorter. 

The Musculoskeletal System is part of the Muscular System and, as its name implies, it includes Skeletal muscle, its attachment to bones, and the interaction between that part of the Muscular System and the Skeletal System.  Skeletal muscles are attached to bones by "cord-like" pieces of dense connective tissue call tendons.  We have always had trouble distinguishing between the definition of  tendons and ligaments.  We decided to associate tendons with the tendency to stretch.  They don't, to any degree, but the muscles to which they are attached can certainly change their length.  Just another "trick" we use to remember "stuff."

All skeletal muscles can be stimulated to contract at will (voluntary.) Some skeletal muscle groups require exacting coordination in order to move a limb.  For example when the biceps contract, to flex the arm, the triceps must relax and "allow" the motion to occur.  Conversely, extending the arm requires the biceps to relax as the triceps contract.  Just flexing and extending the arm is a relatively simple operation.  Think about all of the individual muscles that are involved, and all of the coordinated action that must occur, in a relatively "simple" operation like picking up a pencil, arranging it in your hand, visually locating the spot on the piece of paper where you will ultimately write, flexing and extending the arm (as necessary) while rotating the hand to properly align  the tip of the pencil with the chosen spot, then forming the letters into words, and finally returning the pencil to the table and releasing it.  Each individual muscle receives an impulse from the brain through a series of efferent nerve pathways, then sends a "message" back to the brain via afferent nerve pathways, "describing" it's position in space.  The brain re-evaluates that "position" with reference to the chosen "spot" and sends impulses to re-adjust (if necessary) the point of the pencil. (And all THAT just gets the pencil to the paper.)  This communication network is more complex and faster than any computer.  Imagine for a moment if some injury or disease process interrupted the procedure.  The resulting "chaos" can lead to partial paralysis, lack of coordination, or tremor.

Some skeletal muscles are also controlled by the autonomic nervous system, making them "dual purpose."  For example, small muscles in the eyes that focus the lens, or  the diaphragm, a large flat muscle attached to the bottom of the lungs that helps us breathe (two "functions that we can control) are functions that commonly occur without our direct intervention.

Smooth muscle (involuntary) is under the exclusive control of the autonomic nervous system.  We have no control over it, nor would we want to devote the time, if we were "offered" such control.  Functions such as digestion, as well as other organ and/or system functions, that we don't want to be "bothered with," are controlled by the autonomic nervous system and the smooth muscles are well designed to follow this boring routine.

The autonomic nervous system also controls, to some degree, cardiac muscle.  This special blend of muscle tissue, which forms the heart, is well suited to the constant work that must be performed 24/7 for the entire span of the patient's life.  In addition to accepting direction from the autonomic nervous system, this muscle mass has the special ability to "run its own show."  Each cardiac muscle cell is capable of "automaticity,"  the talent to due what the autonomic nervous system, under better circumstances, directs the "sinoatrial node" to do, start a cardiac depolarization wave.  Cardiac muscle cells also boast the ability to propagate a depolarization wave from one cell to the next, a process called "excitability."   And, again under the best of circumstances, this propagation begins in the upper left corner of the left atrium at the sinoatrial node, and "propagates" toward the lower left corner of the left ventricle. Add to these, a third function called "irritability" (the degradation of the cell wall secondary to hypoxia, which causes the cell to become more prone to automaticity) and it becomes apparent that this "copy-cat" function (called excitability) can begin at any cardiac muscle cell and travel in any direction, in a heart that is starved for oxygen.  The special capabilities of cardiac muscle notwithstanding, this type of muscle is very sensitive to drops in oxygen supply, and under such conditions, very likely to cause "extra beats" which originate from different parts of the heart, and can cause life threatening conditions.  Whether the drop in oxygen is secondary to a respiratory system failure, a circulatory system failure, or a disease process, is what the healthcare team needs to determine, and subsequently correct.  The First Responders, EMT-B's and Paramedics, in the field, are strongly "encouraged" to provide this patient with supplemental oxygen in high concentration.


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The Respiratory System

The respiratory system is a collection of muscles, passageways, tubes, and sacs that provide for the exchange of oxygen and carbon dioxide.  It is open to the outside environment  and consists of the nose and mouth, the nasopharynx and oropharynx, the pharynx, the epiglottis, larynx, trachea, bronchi, bronchioles, and alveoli.  The passageways, as the air moves in from the outside environment, get smaller and smaller until they reach the smallest structure in the system, the alveolus.  It is here, in the alveolus, that the exchange of carbon dioxide and oxygen takes place. 

How smart these carbon dioxide and oxygen "guys" must be, to "know" that carbon dioxide should move in one direction, and oxygen should move in the other direction.  Right?  Aihh!  Not really.  You see, it all has to do with the partial pressure of each of the individual gases in the two different locations (the lungs, on one side of the alveolar membrane,) and the blood (on the other side of the alveolar membrane, referred to as the "pulmonary capillary.")   The gases move from an area of higher pressure to an area of lower pressure, seeking equilibrium.  In the pulmonary capillaries (in the lungs) the partial pressure of carbon dioxide is higher than the  partial pressure of carbon dioxide in the alveolus, and consequently, the carbon dioxide moves from the blood into the lungs.  In the alveolus, the partial pressure of oxygen is higher than the partial pressure of oxygen in the pulmonary capillary, and consequently the oxygen is "drawn" into the blood.  Picture, if you will, the alveoli as a bunch of grapes.  A well grown bunch of tightly packed grapes. The grapes, however, are round, and no matter how "tightly" you pack round objects, there will always be a small gap (or sulcus) between adjacent objects.  Into these sulci place a blood vessel, keeping in mind that the bunch of grapes is three dimensional, and that at some points the sulci may actually go off in more than one direction.  What you've created in your mind is a three dimensional array of a "bunch of grapes," covered with blood vessels that go over, under and around the grapes.  Now, take the "skin of the grapes" and make it the same as the "skin" of the blood vessels.  Two more steps.  Make the "skin" just one cell thick, and the blood vessel small enough that the red blood cells have to "line up" one behind the other in order to fit through.  What you end up with is a bunch of carbon dioxide laden red blood cells, marching single file, past (over, under, and around) a bunch of oxygen laden alveoli, and those red blood cells are only one cell's distance away from the oxygen that is in those alveoli  As the blood moves through the lungs, the "opportunity" to exchange gases is repeated over and over again, as the blood passes over (under and around) subsequent alveoli. 

More about the circulation of blood later, in the Circulatory System.  (Beginning to see how these systems are interrelated?)  

Now, with all of this gas exchange occurring through the semi permeable membrane that makes up the barrier between air and blood, you can imaging the amount of "quality control" that must be exercised in order to assure that the "air" that comes is contact with the membrane is very clean (so we don't " clog up" the pores of the membrane,) and is the proper temperature so that we don't "over cool" the blood, and, OH, it should also have a controlled amount of moisture in it so that it doesn't dry out the membrane, and to make it easier to control and maintain a certain temperature.  Wow, some 'quality control inspector' is going to be making some good "overtime" here.  Actually, all of the "stuff" in the respiratory system, before the alveoli, is well suited to accomplishing  this control.  The upper airway (the nasal air passages, including the sinuses, the nasopharynx, and the pharynx, and to a lesser extent, the oropharynx) are responsible for doing the initial filtration (sorting out and removing the BIG stuff, like dust,) for adding the necessary moisture, and bringing the air up to a proper temperature.  The lower airway (trachea, bronchi, and bronchioles) does the final filtration, removing unwanted molecular particles and doing final adjustments to the temperature.  The filtration is accomplished through a series of hairs and hair-like structures that get progressively smaller as the passageways get smaller. 

So, just HOW does the body get this properly tempered, moisturized, cleaned, air into the lungs.  Well, that's where the final structure of the respiratory system comes into play.  The associated muscles.  The largest of these is the diaphragm.  A flat muscle attached to the inferior aspect of the lungs.  At rest it is curved upward, kind of like a upside-down bowl.  When inhaling, the muscle flattens, pulling the inferior aspect of the lungs downward.  At the same time, muscles between the ribs, called intercostal muscles, move the anterior aspect of the thoracic cage outward and slightly upward, and muscles in the shoulders move the superior aspect of the thoracic cage upward.  This change in configuration (geometry) of the chest cavity tends to make the thoracic cage bigger, causing a negative pressure inside the lungs, which is "quenched" by the flow of air into the alveoli.  It's kind of like blowing up a balloon, but instead of holding the neck of the balloon and blowing it up by creating positive pressure on the inside walls of the balloon,  the balloon is turned around, the body of the balloon is placed in the mouth, the neck of the balloon is left exposed to the air, and a negative pressure is exerted on the outside of the balloon by "sucking" it into the mouth.  PLEASE, don't try it, just understand the concept.  So, all that serves to get oxygen laden air into the lungs, what gets the carbon dioxide laden air out of the lungs?  Relaxation.  The diaphragm relaxes, intercostal muscles relax, and shoulder muscles relax.  The chest geometry returns to the "relaxed state," the pressure inside the lungs increases and the air is expelled.  Note that the inhalation is the result of "positive" muscle action, but that exhalation does not normally require any muscular effort.  Interestingly, the muscle "effort" is both voluntary and involuntary.  Breathing is normally an involuntary function controlled by the brainstem, but is also a function that we can control at will.  As an involuntary function, breathing is a process controlled by the acidity in the blood.  Chemo-receptors in the blood stream monitor the amount of acid, which increases proportionally with the amount of carbon dioxide.  When that acidity reaches a certain level, the brainstem "creates" the urge to inhale (albeit, at times, an unconscious "urge.")  Normally, the body is motivated to inhale by an over abundance of carbon dioxide (unusual levels of acid,) but the body is very adaptable.  For individuals that "normally" have elevated levels of carbon dioxide in their blood, such as emphysemics, the brainstem tends to ignore carbon dioxide levels (because they are usually elevated anyway) and relies on  a back-up system called the hypoxic drive, which monitors the levels of oxygen in arterial blood.  When oxygen levels drop, this back-up system is also capable of initialing the urge to breathe.  This back-up system is less reliable and not as sensitive, and may not serve to maintain the balance in blood chemistry as well, especially during times when breathing is, by necessity, an involuntary function, such as sleeping.  For this reason, some people with breathing disorder, may find that their sleep is interrupted by the effects of hypoxia (as discussed in the "Foreign Body Airway Obstruction - Infant" section of an earlier page entitled "Obstructed Airway," in the First Aide Section of this website.)

Time for another mental exercise.  Think about the last group of people that you were with (maybe it was the other students in your EMT class.)  For the entire time that you were with them, you can be certain that each and every one of them was breathing.  But, how many of them did you notice breathing?  Not many, if any, we would guess.  Breathing is not, under normal circumstances, a function that is generally detectable without mindful awareness.  Even your own breathing is not something that warrants attentiveness.  The point is made so that should you, during your career, encounter a patient and the first thing that you notice is their breathing effort, they ARE HAVING A PROBLEM BREATHING.  It might be a chronic problem (one they've had for a while) that they have become accustomed to (learned how to "compensate.")  And when asked if they are having any difficulty breathing, they deny the problem, because for them, there's no "additional problem."  Nevertheless, something is wrong.  In addition to "noticeable effort," there are some other "things" you might initially observe.  The use of accessory muscles (muscles not normally associated with breathing, in the stomach or neck,) intercostal retractions (the surface of the chest cavity is "sucked" in-between the ribs) and tripoding (the patient is sitting with hands on knees, bent forward slightly,) a position where the patient tries to "suspend" the lungs over his/her lap using gravity to "help" inflate the lungs.

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The Circulatory System

The circulatory system is closed system, (meaning that it is not open to the atmosphere under normal conditions,) of tubes (arteries, arterioles, capillaries, venules, and veins) which carry fluid throughout the body.

A complete discussion of the circulatory system would have to include the lymphatic system.  Another system that interacts with the cardiovascular system.  Although this secondary circulatory system is somewhat beyond the scope of the everyday Basis Emergency Medical Technician, a simplistic understanding of it's existence and purpose adds to the well-rounded understanding of the well-trained EMT-B .  The lymphatic system stores a (near clear) type of serosanguineous fluid called lymph.  Lymphocytes (white blood cells) normally stored in the lymph glands (lymph nodes) are "dispatched" by those glands by allowing the lymphocytes to move across the blood vessel walls adjacent to the lymph gland into the cardiovascular system, to fight cancer cells and bacteria.  Having completed their mission, the lymphocytes are re-absorbed into the lymph glands for "revival." Ready for the next battle.  Kind of like little "squad buildings" located at strategic points throughout the body, where the "ambulances" (white blood cells) sit waiting to be dispatched to an area of "need."  Medical professionals can diagnose an existing "problem" in the body by counting the number of white blood cells in central circulation (elevated above normal when infection is present,) and by feeling the size of the lymph glands (enlarged after abnormal activity.)

One of the explanations that many students have found helpful to understand the circulatory system is one where we ask the class to imagine that they are a red blood cell, and we follow the cell through the entire "trip."  So, if you'll bear with us, let's get ready to take a trip.

We start in the right ventricle.  It seems that we have just arrived with all the other blood products, when without warning, we are suddenly pushed into the Pulmonary Artery.  Incidentally, arteries always carry blood away from the heart (two "A's"  artery and away.)  This is the only artery in the male body that carries deoxygenated blood.  In a pregnant female the placental arteries carry deoxygenated blood away from the baby.  Sorry, we have this habit of digressing.  So.....the blood moves away from the Heart in the pulmonary artery toward the lungs.  It enters smaller and smaller blood vessels until the red blood cells (that's you) are forced to "line-up" one behind the other.  As this happens, you're entering part of the alveoli called the Pulmonary Capillaries.  The alveoli are the very delicate lung  tissues.  Imagine a bunch of grapes.  Big round healthy grapes, packed together as tightly as you can visualize.  Now, because the grapes are round, no matter how tightly you pack the grapes, there will always be a space between adjacent grapes.  In this "space" place a blood vessel.  Remember that the grapes are three dimensional and that the blood vessels could branch off in several directions at any space.  Now, construct this three dimensional grape structure so that the "skin" of the grape and the wall of the blood vessel are one membrane.  Inside the grapes is air, in the blood vessels is ..............YES, blood.  The membrane separating them (the air and the blood) is only one cell thick.  In other words, the blood is only one cell away from the air.  This is where the blood cell (you) is going to give up it's Carbon Dioxide and assume  Oxygen.  That smart little blood cell knows that it's supposed to give up Carbon Dioxide at this end of the journey and give up Oxygen at the other end of the journey (later on,... out in the body.)  Not so.  The whole "transaction" is based on a rather simple concept from Physics.  That all matter seeks a state of equilibrium.  For example, if you took the room that you are in right now, and constructed a water tight divider in the center of the room.  Then, filled one side of the room with water. Then, removed the divider.  The water would flow into the "dry" side of the room until the level of the water was at the same height in both sides of the room.  So,  here you come into the alveolus, with your arms full of Carbon Dioxide and a empty wheel barrow that would normally carry oxygen.  At the same time, another "guy" is marching into the lungs with his arms full of Oxygen and an empty wheel barrow that would normally carry Carbon Dioxide.  You get to one of those grapes and suddenly you can "dump" some of  that Carbon Dioxide into his wheel barrow and he dumps some of his Oxygen into your wheel barrow, until equilibrium is achieved.  If you can't get rid of ALL the CO2, or can't get enough O2, from the first guy, don't worry, the trip through the grapes is a long winding one, that will expose you to a whole bunch of "guys," and as long as they have more Oxygen than you and you have more Carbon Dioxide than they, a transfer will occur.   And so, you exit the lungs, very happy, with lots of Oxygen (looking very proud and red,) and you start moving into larger and larger blood vessels until you enter the Pulmonary Vein returning to the Heart.  You enter the Heart through the Left Atrium and flow into the Left Ventricle.  It's at this point that we usually ask the class, "What is the purpose of the atrium."  Invariably, students will respond with, "It pumps blood from the atrium to the ventricle."  This answer is not completely wrong, but it is somewhat misleading.  The flow of blood into the heart (all four chambers) is "passive."  There's no "sucking" action that draws blood into the heart.  The valves between the atria and the ventricles are normally open during diastole (at rest,) while the heart is filling.  When blood enters the atria, it flows all the way down into the ventricles, until each ventricle is full, then continues to flow into the heart until each atrium is full.  At this point, the atrium contracts, causing an additional volume of blood to be forced into the ventricle, increasing the pressure in the ventricle, which "helps" close the valve between the atrium and ventricle, just before the ventricle contracts.  This creates a kind of "explosive" ejection of blood from the ventricle and creates the systolic blood pressure in the two large arteries leaving the heart.  Now, if you have just been forced out of the left ventricle, you find yourself entering the Aorta.  A large vessel that is at the top of the heart.  You travel upward for a short period then find yourself "turning" downward through a part of the Aorta called the "Aortic Arch."  As long as we're here, let's talk about what it does.  This is going to be a lengthy digression.  So if you're hungry or thirsty, why not go get a snack (or drink) and hurry back...........I'll wait.............................Back so soon? 

  Okay, let's talk about the heart for a minute.  First of all, we know that the heart is a muscle, and, when it contracts, it pumps blood into the body.  But there's one part of the body that it can not "pump into" during it's contraction.  ITSELF.  The muscle fibers in the heart are tense at this point and all the little blood vessels in the heart are "squeezed shut" by that tension.   Consequently, we have to find another way, another time to profuse the heart muscle.  The heart receives blood through a process called "retrograde profusion."  Most of the blood that is in the Aorta makes it all the way over the Aortic Arch and flows (through the "Descending Aorta") into the body, some blood enters smaller arteries at the top of the arch (and just outside the aortic valve) and travels into the head (and the very beginning of the heart's circulatory system.)  Some is left in the first part of the Aorta (before the Arch) and, at the end of the systolic cycle, it "falls" back toward the heart and enters the heart's arterial system and profuses the heart muscle during the next diastolic cycle.  This "retrograde" flow continues until the Aortic Valve closes.  It has just been forced open by the flow of blood coming from the Left Ventricle during the Systolic Cycle.  At the end of the Systolic Cycle, it takes a few milliseconds for the Aortic Valve to close and it is during this time that the blood flows back into the heart.  When you take a blood pressure by auscultation, you are listening for a change in the sound that the pulse is making as you lower the external pressure exerted on the artery.  The systolic pressure is heard during the Systolic Cycle (as long as the external pressure that is being exerted is the same as, or slightly less than,  the pressure created by the heart.  At pressures above this value, no pulse is heard.)  It is the pressure that the blood exerts against the artery during the time that the aortic valve is opened.  Immediately following the end of the Systolic Cycle, the pressure in the artery begins to drop.  It will continue to drop until the aortic valve closes.  When this occurs, the pressure against the artery stabilizes and the sound changes, as we continue to reduce the pressure against that artery, and it is at this "change" in sound that we record the Diastolic pressure, and it is at this point at which the Aortic Valve closes, and the heart receives NO MORE retrograde flow.  Now, if the difference between the Systolic and Diastolic "numbers" is called the "Pulse Pressure," then pulse pressure is a measure of how well the heart is being profused.  That is actually  an over-simplification.  One must consider heart rate as well, because Diastolic Fill Time (when the heart is filling) has a direct effect on the cardiac output, which might not necessarily affect blood pressure, but would affect retrograde profusion.  Hey, listen, if we've confused you with all of this, write to us and we'll try to clear it all up.  We just thought you might like to know.  It's not really that important, at this stage of your development.  Meanwhile, back in the Descending Aorta, you continue to flow down into the body (let's assume that you're going to travel all the way down to the feet.)  You keep flowing through smaller and smaller blood vessels until, once again, you (a red blood cell) are forced to line up single file behind the other red blood cells.  The exchange of CO2 and O2 again take place, much the same as they did in the lungs, and the return trip starts.  Another digression.  The question is posed, "What gets the blood back to the heart."  Some of our students have suggested that it is 'blood pressure.'  Think about it for a minute.  If any "blood pressure" existed in the alveolus or in the capillary, the pressure would destroy the delicate tissue.  The fact is that the journey into smaller and smaller blood vessels, has also served to reduce the blood pressure until once at the endpoint (alveolus or capillary) the blood pressure is non-existent.  So now, the journey begins back to the heart.  The veins are surrounded by skeletal muscles, and if one contracts those muscles, the blood in the vein is "squeezed" out.  The veins also have valves in them so that the blood can only flow in one direction, back toward the heart.  So the return of blood to the heart is not dependant on blood pressure, but movement of the extremity from which the blood is returning.  If that "return" is from the lungs, negative pressure in the thoracic cavity and the fact that the blood is moving into ever larger and larger blood vessels, helps return the blood to the heart.  Lack of extremity movement is one of the reasons that bed ridden people may have some swelling in the lower extremities (the heart is pumping the blood "down," but they are not walking around to help "pump" it back and consequently the collection of additional blood causes an unusual rise in pressure exerted on the vessel walls and fluid permeates the vessel wall and collects in the interstitial spaces.)  And so, the journey continues into larger and larger blood vessels until you enter the Vena Cava (a large vein that conducts the return blood flow from the body to the right side of the heart.)  You flow through the right atrium into the right ventricle, and the journey starts all over.

An integral part of this system is the pump (the heart) that initiates the movement of blood through the pipes.  As discussed in another section, this is a special type muscle that is capable of performing on an average of 60 - 100 times per minute.  That's a lot of demand, and requires a specialized type of muscle fiber.  Muscles in other parts of the body normally need a considerable rest period immediately following exertion, but this muscle (the heart) MUST perform over and over again, without rest, for the extent of the patient's life.  In addition to this incredible ability, the heart (which under normal circumstances takes direction from other parts of the body regarding the need for increased rate or output,) has it's own "self-motivated' electrical system that, in the event of isolation from the rest of the body, will keep it functioning, even if at a "sub-standard" rate.  If you're interested in a more detailed explanation of the electrical system of the heart, we have one in the "Auto. External Defibrillator" section of CPR, and this link will take you there.  However, there is not return link, so just use your browser's "Back Button" to return to this page.

The blood being circulated by this system is composed of plasma (a gooey yellowish fluid that serves as the main "vehicle" for the rest of the components,) red blood cells (erythrocytes) which carry hemoglobin (a molecule capable of carrying oxygen) which imparts a red coloration to the blood, white blood cells (leukocytes) which help fight infection and provide immunity, and platelets (small elements in the blood that help clotting.)

The circulation of the blood (as well as heart rate, regularity and to a lesser extent the "force" of the heartbeat) can be monitored by palpating a pulse.  This process is also useful for evaluating the perfusion of an extremity or of  tissue distal to an injury (usually in an extremity.)  A graphic of the location of pulse points throughout the body is available here.  The actual palpation of a pulse is something that takes practice and this forum is probably not the best place to learn how.  We do however have some suggestions and comments.  A pulse is the tactile representation of  a "fluid hammer," (directly from the left ventricle) caused by a beating heart, and in order to be able to "feel" the wave of pressure pass the palpation point, the artery must be partially compressed between the rescuer's finger(s) and some "sounding board" behind the artery (such as bone or cartilage.)  For most of the pulse points this is just a matter of find the correct point to palpate.  Where the pulse point is located in a joint (such as the distal brachial, or the popliteal pulses) it's important to remember that the joint must be fully extended in order to effectively palpate the pulse.  Flexing the joint, even just a little, moves the "sounding board" (in this case, the cartilaginous joint 'material') away from the artery, making it difficult, at best, to palpate the pulse.

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The Nervous System

The nervous system is a very complex collection of "information" pathways connected to a "central processing unit" that puts to shame anything you could buy in an electronics outlet.  All activity in the body is controlled by the nervous system.

There are two major divisions of the system.  The central nervous system and the peripheral nervous system.

Voluntary activity is controlled by the somatic nervous system and involuntary activity by the autonomic nervous system.  Each of these are sub-divisions of the central and peripheral nervous systems.

Each of the subdivisions can carry information to, or from, the brain, along "wires" called nerves (or nerve pathways.)  Afferent (sensory) nerves carry information from the tissue toward the brain, and efferent (motor) nerves carry information away from the brain.

The foregoing is a simplified overview of the construction of the nervous system and is offered in this introduction in an effort to properly orient the reader to what will prove to be a involved explanation. (Like we haven't had a couple of those, yet)

The central nervous system (CNS) includes the brain and that part of the spinal cord protected by the spinal column. 

The brain is that "central processing unit" referred to above.  It is divided into three parts.  The cerebrum (sometimes referred to as gray matter) pretty much conceals the other two parts and is the largest of the three.  It is first divided into right and left halves.  The right half, for the most part, controls the left side of the body, and the left half, the right side of the body.  It is further divided into four regions, frontal, parietal, temporal, and occipital.  Each region is responsible for different activities/functions/interpretations coming from or going to specific parts of the body.  The cerebrum is also responsible for the "storage" of "self," (those characteristics and emotions that distinguish one individual from another.)

Tucked up underneath, and slightly in front of, the occipital region of the cerebrum is the cerebellum.  This is kind of like a "modem" for the cerebrum.  It coordinates the activities of the cerebrum, and is the body's source of coordination as well.  Patients with injury to the back of the skull, may exhibit loss of muscular coordination (be unable to walk a straight line, stand up unassisted, etc.,) or loss of informational coordination (be unable to properly form words or understand concepts.)

At the base of the brain, just above a giant hole (the foramen magnum) in the floor of the skull (sometimes referred to as the basilar skull) is a very primitive part of the brain called the brain stem.  Primitive in as-much-as it controls virtually all the activities of the body that are absolutely necessary for life, but so damn mundane that we don't 'want to be bothered' with controlling their occurrence.  Cardiac, respiratory, digestive, and  endogenous defense mechanisms are just some of these activities.  Can you imagine how our lifestyles would change if, after eating, for about 1 or 2 hours, we had to consciously think about digesting all that food that we just ate?  Thank the brainstem.

The brain collects, sorts, and acts upon a vast amount of information, fed to it on a continuing basis.  Some of the action taken is voluntary (somatic) and some is involuntary (autonomic.)

The spinal cord (the second major part of the central nervous system) attaches to the brain stem and cerebellum at, or about, the foreman magnum, where all the connecting fibers come together to form a single cord.  It travels down the back through the spinal column which is formed by adjacent holes in the center of  individual vertebra.  At each vertebral joint there are two lateral holes which permit nerve fibers to exit and link the central nervous system to various organs of the body.  Just below the level of the second lumbar vertebra the cord exits the canal and forms the "cauda equina," (Latin for "horses tail,") where the fibers continue to split left and right.

Specialized areas of the spinal cord have "decision making" capability.  In extremely emergent situations, where immediate action is  imperative, all of the actual "information" never travels all the way to the brain, but is "short circuited" (in part) by a connecting nerve (or "reflex arc".)  Have you ever inadvertently placed your hand on a hot surface, and found that you pulled it back before you even "realized" that the surface was actually hot?  Kind of an immediate response to a possible injury.  The shortcoming of this secondary "decision making" area is that, at times, it's wrong, but it always assumes that some protective action needs to be initiated.  Have you ever pulled your hand back from a surface that you, for a brief instant, 'thought' was hot, only to find that it wasn't?  Kind of an immediate response to a perceived injury.  The classic "knee-jerk" reaction is a test of this reflex arc function.

The peripheral nervous system is that part of the nervous system that is NOT part of the central nervous system.  It is a collection of:

  1. nerve pathways that carry sensory (affective) information toward the brain on afferent nerves, and motor (effective) impulses from the brain on efferent nerves, and

  2. nerve cells that initiate the informational/impulse transfer. 

It is in the peripheral nervous system that its complexity becomes mind boggling. 

As previously mentioned there are nerve fibers that exit the spinal cord at various levels (from the first cervical level to the fifth sacral level.)  Each motor nerve has a nerve cell (located in the spinal cord) which initiates the impulse (received from the brain) and an efferent pathway (nerve fiber) carries the directive to its intended target.  Each sensory nerve has a cell located in the periphery which "senses" some specific environmental input (heat, cold, salt, sweet, bitter, pressure, pain, light, movement, odor, and position) There are probably others but, you get the idea. Each of these cells initiates an informational impulse and an afferent pathway (nerve fiber) carries the information back to the spinal cord to a specific location (to be relayed to the brain.)  "Communication" in the nervous system is conducted between nerve cells by way of nerve fibers.  Much like the way a telephone communication system communicates between central communication centers.  Like that telephone communication system, nerves are "paired," one efferent pathway is associated with one afferent pathway, completing the "communication" ability.  Unlike the telephone system, nerve pathways are not "solid" wires.  They consist of segments  (called "axons") of various lengths that look something like this.   Graphic of Synaptic Cleft showing constructed so that movement of the impluse is from left to right.  The impulse "jumps" from the axon terminal to the next axon (across the synaptic cleft,) by a process called synapsis, using a neurotransmitter.  A clever little physiological function that keeps impulses traveling in only one direction.  In the above illustration the impulse would be moving from left to right.

Like the central nervous system, there are some portions of the peripheral nervous system that are somatic and others that are autonomic.

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The Integumentary System

The Integumentary System consists of skin, hair and nails.  Hair and nails have little to with Emergency Medical Services (in spite of the fact that some females "believe" that a 'bad hair day' or 'broken nail' constitutes justification for calling an ambulance.)

The skin is the largest organ in the human body and that fact, coupled with its anatomical and physiological complexity, practically warrants it's treatment as a separate organ system.

The skin serves three purposes. 

  1. Environmental protection

  2. Temperature regulation, and

  3. Sensory input

Environmental protection includes, maintaining the delicate balance of fluid (water) to tissue.  The Human Body is over 70% water and the skin (a water-tight collection of "dead" cells at its surface) helps keep this percentage within acceptable ranges.  This narrow percentage range of acceptable values between fluid and tissue is necessary to maintain a proper acidic environment for various chemical reactions that sustain life. The skin also provides environmental protection from infection.  This protection is breeched only when the skin is broken, highlighting the necessity for antiseptic procedure when dealing with such circumstances. 

Temperature control has a direct effect on metabolic rate, and metabolic rate a direct effect of the "quality" of existence. 

The body's metabolic process is an exothermic one, creating a significant amount of heat, and in some external environments we are subjected to higher than optimal temperatures.  Through a process of evaporation, which produces a cooling effect, as an end result of sweat production by the sweat glands in the skin, the human body can control over-heating (whether from internal or external sources,) by routing the blood into areas close to the surface of the skin, cooling the blood and carrying that 'cooling effect' back to the interior of the body.  On the superior surface of the skull, where the skin is relatively thin and immediately "backed-up" by the skull, the concentration of blood vessels is relatively high, and consequently, major heat loss is experienced through that region. It is also for this reason (the concentration of blood vessels) that scalp wounds seem to bleed so profusely.  When over heated (again, from either internal or external sources) the patient will exhibit a flushed or red appearance.  Please note that it is not just the production of sweat that cools the patient.  The evaporation of that fluid is a necessary occurrence in the process.  Consequently, a sweating patient in a humid environment, where sweat is just collecting on the skin, may still be overheated.

In some external environments, patients are exposed to colder than optimal temperatures, and the skin "helps" maintain proper body temperature by first sensing the temperature variant (the same as it might if the environment were too hot,) then shunting the blood away from the exterior surface, thereby maintaining (or conserving) body temperature.  Patients experiencing hypothermia (to whatever degree) will have a pale, or cyanotic appearance.

Of interest at this point, is that the skin must "sense" the temperature variant, then communicate that information to the brain, in order for the expected outcome to be exhibited.  The presentations as described above are "normal" even though, under certain circumstances, they may be beyond acceptable limits.  If the environment, patient history and physical exam, and/or other findings are dictating this "normal" presentation, but you "see" something else, then the "communication" ability (Nervous System) or the "sensory"  ability (Integumentary System,) or sweat production ability, may be compromised.

The anatomical structure of the skin is very complex.  A picture is worth a thousand words and we have one for you here.

A breakdown of each of the layers of the skin can be found in your text.  Generally, the editors of the various texts do an excellent job of describing the components of skin.  One text that we find exceptional is, Emergency Care and Transportation of the Sick and Injured, Eighth Edition, Published by Jones and Bartlett Publishers in Sudbury, MA.

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The Endocrine System

The Endocrine System is the body's message and control system.  It, at the direction of the brain, controls the activity of certain body functions.  The human body is constantly seeking a state of equilibrium.  Certain 'functions' in the body need to increase or decrease activity as the demand, or internal/external environmental conditions change. 

For example, blood pressure is affected by three variables, the rate of pump (the heart,) the size of the container (the arteries and veins,) and the amount of fluid (the blood.)  Under normal circumstances, the amount of fluid is constant.  The size of the container and the rate of the pump, however, are variables that can be controlled.  You will have a better understanding of how this happens after you read through the "digression" offered below.  Be patient it IS the granddaddy of all "digressions," thus far.

Substances called hormones, secreted by endocrine glands, are either released directly into target organs, (as in the case of the pituitary gland secreting hormones which control the activity of the pineal gland which controls metabolism,) or are release into the blood stream (as in the case of the of the adrenal glands secreting hormones into the blood stream which has a more global effect.)

The hormone secreted by the adrenals is 'adrenaline.'  When in central circulation, adrenaline invokes the "fight or flight" syndrome. 

Digression.  In an effort to help you remember the changes in the body that take place as a result of the "fight or flight" syndrome, we would like you to consider what happens when you are suddenly placed in a stressful environment. 

Imagine you're driving down a country back road, within the speed limit, enjoying the scenery, relatively relaxed.  Suddenly, as you crest a hill, a car enters the roadway from an intersecting road, and you are forced to swerve into the oncoming lane of traffic, where you narrowly avoid collision with an oncoming vehicle, by again swerving back into the proper lane.  As all of this transpires, you feel a rush of warmth spread throughout your body.  This is one of the affects of adrenaline (epinephrine) and a marker of the "fight or flight" syndrome.  What we are going to do is consider each major area in the body, determine whether its involvement is essential for the successful resolution of the problem, and how the human body and some of its  systems would have to be altered in order to achieve the desired outcome.

Let's start at the top and work our way down.

The brain.  Is its involvement essential?  Absolutely!  The ability to make fast (snap) decisions is crucial to an acceptable outcome.  Consequently, the release of adrenaline into central circulation causes blood vessels in the brain to dilate, providing more oxygen and nutrients to the brain, enabling it to perform above standard levels.  Other hormones are also released which greatly increase the metabolic rate of the brain which achieves the desired outcome (being able to think faster) but has an interesting effect on time perception.  Everything seems  t-o   s - l - o - w      d - o - w - n , because the brain is processing information, including time, at a significantly accelerated rate.

The eyes.  Do they need to be capable of performing their function with more efficiency?  Again, absolutely!  The release from the adrenal glands    (Another digression.  [If you keeping track, this is actually a digression within a digression, Charlie would be proud] Where are the adrenal ('ad' - 'renal') glands located?  Yes, as the name implies, 'above' (ad) the 'kidneys' (the renals.)  One is actually attached to the top of each kidney.  The kidneys are well vasculated and have a rich blood supply.  A perfect "dispatch point" for a substance that needs to be into and out of the system as quickly as is indicated by this emergent situation and the somewhat threatening side effects of the "drug.")    cause the pupils in the eyes to dilate.  Information needs to be able to "get in" faster to supply the overact brain.  As a matter of fact, ALL sensory input is elevated to DEFCON 2, a heightened state of alert, with some reasonable exceptions.  It's obvious that your ability to taste/smell food is probably not heightened, but sight (as mentioned above,) hearing (by increasing the circulation into the auditory canal,) and sensory contact (by exciting erector pili muscles causing hairs to stand on end,) are key players in this emergency.

The respiratory system.  Key player?  You bet.  The entire respiratory tract is dilated, allowing for more efficient exchange of Oxygen and Carbon Dioxide, and the respiratory rate is increased in order to supply the increased metabolism.

The cardiovascular system.  The heart rate increases, blood vessels in 'key' areas are dilated (vessels that supply the large muscles in the legs and arms, vessels that carry blood to the head and respiratory system,) but blood pressure is probably only slightly higher, because, although the rate of the pump increased, the size of the container probably experienced only a slight increase in overall size because for all the 'key' vessels that are dilated, many 'non-key' vessels are constricted (for example: blood vessels in the skin are constricted, causing a look of pallor [got to conserve that 'heat' for all this increased metabolism].)  One kind of offsets the other.  The lymphatic system is also probably in a state of readiness, although, we would guess, to a somewhat lesser degree.

The digestive system.  Think you're going to take time out for a sandwich?  Probably not.  And the last thing you need to do is be "forced" into taking a toilet break.  The digestive system will essentially shut down.  It is for this reason, that some of us find ourselves in the middle of "one of those calls" that would gag a maggot, and we just seem to "do what needs to be done."  However, immediately following the call, when things settle down, and all systems are back online at normal functioning levels, we go off somewhere (alone) and lose lunch.  As a matter of fact, the digestive, urinary, and reproductive systems are all considered third string at this point and are more than likely not of concern to the brain.

The musculoskeletal and the integumentary systems are going to have a 'mixed' response.  Large blood vessels, that supply large muscles (strength preparedness) will dilate.  Smaller blood vessels (near the surface of the skin) will constrict, conserving body heat for the increased metabolism in other areas.  This will impart a pale look to the person involved in this situation.

WOW!  Was that a digression, or what?

Back to the "balancing act" performed by the endocrine system.

We were talking about blood pressure.  Blood pressure is a value that is constantly changing.  The body attempts to achieve a state of equilibrium, but true equilibrium is only achieved, by the body, a short time after death.  A perfect blood pressure for most individuals would be 120/80 and, it is this state of perfection that the body seeks.  If the B/P drops below the norm, the brain receives a message from sensors in central circulation, and either increases the heart rate or decrease the size of the container (or a combination of both) to elevate the falling B/P.  As the pressure elevates, the sensors send messages to the brain, and the action taken to raise the pressure is discontinued.  If the pressure continues to rise, the brain starts to dilate blood vessels in an effort of drop the tension.  If, again, it drops below acceptable limits, the process starts over and the pressure begins to rise.  This is a never end 'battle,' a continuing quest for equilibrium, but as stated above, this is an unachievable goal, short of death.  Think about it, a blood pressure of  0/0 must certainly be considered a life threat, but it is probably the most stable blood pressure attainable.

The endocrine system is responsible for directing this balancing act, throughout the body.  Controlling different aspects of metabolism, growth, chemical composition, etc., and monitoring the outcome of the controlling effort, then shutting off the effort when no longer needed is what this system does best.

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The Digestive System

The Digestive System is open to the atmosphere at both ends and includes everything between the mouth and the anus that is associated with nourishment intact, processing, and elimination.  It includes: the mouth and salivary glands (where the process of digestion is started,) the oropharynx, and esophagus (which conduct the food to the stomach,) the stomach (where the ingested food is mixed with gastric juices, prepared and stored for movement into the duodenum,) the pancreas, liver, gallbladder, and bile ducts (which work in cooperation with each other to add pancreatic fluid and bile to the duodenum,) the duodenum (where digestive juices are added and the ingested food, now referred to as 'chyme' is conducted into the small intestine,) the small intestine (where the digestive enzymes extract amino acids, fatty acids, simple sugars, vitamins, minerals and water for absorption through the walls of the small intestine,) the appendix (whose function is unknown,) the large intestine (consisting of the cecum, the colon, and the rectum, where the remaining fluids and electrolytes are reabsorbed from the chyme and the resulting formed stool is stored [in the rectum] for elimination through the anus,) and the anus (a collection of sphincter muscles which control the escape of solids, liquids and gases from the digestive tract.

Our interest in the digestive system needs to focus on those parts which may be affected in such a way as to create an 'emergency' that can be corrected , abated, or 'treated' by the pre-hospital team.

The mouth and oropharynx are also 'parts' of the respiratory system and their involvement in a possible airway blockage needs to be kept in mind.  Clearing a blocked airway is covered in the "Obstructed Airway" section of this web site.

The esophagus, and it's proximity to the trachea, are of concern to providers who are trained in the skill of endotracheal intubation and a discussion of this will be had in the "Advanced Life Support" section.

The pancreas, bile ducts, gallbladder, small and large intestines are either well protected by the anatomy or such 'soft' organs that the likelihood of injury is slim.  As pre-hospital care providers we needn't be too concerned.

The liver (a large, solid organ that sits beneath the diaphragm, mainly in the right upper quadrant of the abdomen with a small portion extending into the left upper quadrant,) is held in place by a ligament (ligamentum teres hepatis) and it is a relatively heavy organ.  When the human body is subjected to sudden deceleration, the liver continues to move forward, and the ligament acts like a cheese slicer cutting into, and possible through, the liver.  Because it is a highly vascular organ and the subsequent bleeding can be significant, the pre-hospital provider is encouraged to remember (in the presence of a deceleration event, or other findings that might indicate liver injury,) this possibility when the patient is complaining of upper abdominal discomfort.

In closing this section, we are reminded of three engineers who were discussing the construction of the human body.  Each claimed that GOD must have been some kind of engineer to be able to create such a complex 'machine.'  The Electrical Engineer marveled at the electrical complexity of the human body and was certain the GOD must have been an Electrical Engineer.  The Mechanical Engineer stated that GOD must have been a Mechanical Engineer, highlighting the use of levers and fulcrums throughout the body.  The Civil Engineer stated, without explanation, that GOD was a Civil Engineer.  When taken to task, by the other two, the Civil Engineer went on to explain that only a Civil Engineer would put a sewage plant next to a playground.  Think about it.

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The Urinary System

The Urinary System is responsible for the removal of impurities from the blood and the elimination of those impurities in urine.  The system consists of the kidneys, the uteters, the urinary bladder, and the urethra.  The system is slightly different in males and females (DUH.)

In the emergency medical field, there isn't much concern with the urinary system, with maybe two exceptions.

Traumatic injury to the external organs of the urinary system, and unilateral flank pain.

Traumatic injury to the penis or vulva is, at best, embarrassing for the patient and, at worst, a situation that requires appropriate bleeding control.  We can't think of any other situation involving these organs that would be of immediate concern to the Emergency Medical Technician.

Unilateral flank pain is usually an indication of renal colic (a kidney stone.)  The pain can be excruciating but the definitive care for this condition requires advanced skills.

Most texts do a good job of describing the system in detail, and a well educated Emergency Medical Technician needs to be familiar with this information.

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The Reproductive System

The Reproductive System is responsible for the reproductive process (Another DUH.)  And again (as mentioned above,) other than traumatic injury to the external organs, there isn't much concern here for providers in the emergency medical field.

Finally (as mentioned above,) the well educated Emergency Medical Technician would be smart to familiarize himself/herself with the information included on the pages of their text.

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Last updated: 02/23/15.