Laboratory 2: Heart Anatomy and Blood VesselsIntroduction: In this lab we will use a variety of materials to study the structures that supportthe blood and its circulation through our body. We will examine the anatomy of the heart usinga heart model, preserved sheep hearts and a fresh heart from a pig (same size and shape as ahuman heart). Be sure to look at the pig heart in lab, it will not be available for use during theopen lab sessions. Remember that you are really looking at the same short list of structures indifferent organisms, the structures of the heart are amazingly similar in all mammals. Thissimilarity is why pigs have been considered as potential sources for organ donation to human inneed of a heart transplant (i.e., xenotransplants). The second part of the lab will have you identifysome of the major histological structures of arteries and veins. The last part of the lab will haveyou identify the major arteries and veins on the torso model and the female human cadaver.Bring your book and computer!PART I: HEART MODELSOrient yourself to the anterior surface of the heart model by looking for a prominent diagonalgroove (e.g., looks like a gun-sight) that is filled with fat and coronary blood vessels. Thisgroove is named the anterior interventricular sulcus. The less prominent posterior interventricularsulcus can be observed on the posterior (back side that faces the vertebrae) aspect of the heart.Next, locate the right and left sides of the heart, but remember to use the hearts frame ofreference – like it was in a cadaver, not your own. The superior region with where the largeblood vessels enter and leave is the base and the inferior end that tapers to a blunt point is calledthe apex.Now that you know front (i.e., anterior) and back (i.e., posterior) as well as right and left, orientyourself to the hearts internal chambers by way of the external auricles. The right and leftauricles are the pink flaps on either side of the upper part of the heart. The auricles got theirname, which means "little ear", because they are small ear-shaped appendages of the two upperchambers of the heart, the right and left atria. Remember: the auricles are atrial appendages.Locate the spacious right and left atria (chambers) by opening up the heart model. Inferior tothese chambers find the right and left ventricles. The four heart chambers can now be used tolocate the valves and great vessels attached to the chambers.The vessels attached to the right atrium are the large, blue (this means deoxygenated bloodtravels through this vessel) superior and inferior vena cava. These vessels receive blood from allover the body and deliver it to the right atrium. Find the internal openings of the vena cava on thewalls of the right atrium.Blood from the right atrium (deoxygenated) is pushed by the contraction of the atrium and by thevacuum from the expansion of the ventricles through a large valve named the right atrio-ventricular valve (i.e., tricuspid), into the right ventricle. (The term tricuspid is being phased outand so you should try and learn the structure by the anatomically correct name.) Blood from theright ventricle must then do a big U-turn to exit from the anterior superior part of the rightventricle. Look on the front piece of the model to find the anterior half of the ventricle. In theanterior, superior part of that chamber, find the point of exit of blood through a three-partedvalve named the pulmonary semilunar valve. This valve occurs at the junction between the rightventricle and the pulmonary trunk. The pulmonary trunk is so named because it has not yet splitinto a right and left half. Locate both parts of the blue pulmonary trunk, reassemble the model,and trace the pulmonary trunk to the point where it splits into the pulmonary arteries. Eachpulmonary artery carries blood to one of the lungs where it becomes oxygenated.
Oxygenated blood (bright red in coloration) returns from the lungs to the left atrium through thepulmonary veins. Reopen the heart model. On the inside of the left atrium, find four black-painted circles representing the openings of the four pulmonary veins. Locate the four redpulmonary vein stubs externally. Two are found on each side of the model corresponding to theright and left sides of the body.Next, find the left atrio-ventricular valve (i.e., bicuspid) below the left atrium. (Like the tricuspidname, the bicuspid name is being phased out and you should try and learn the structure by theanatomically correct term.) Blood passes through it into the left ventricle. Blood in this chambermust again make a big U-turn to pass through the aortic semilunar valve into the red, curvedaorta. Find the aortic semilunar valve and aorta on the back piece of the heart. Blood from theaorta is distributed to all parts of the body through numerous branch arteries.Note: On the model the color of the vessel indicates whether the blood it contains is oxygenated(red) or deoxygenated (blue), not strictly speaking if it is a vein or an artery.VALVE PARTS:The heart models show some features of the heart valves as well. The aortic semilunar valve andpulmonary semilunar valve show three semilunar valve flaps which meet snugly in the middlewhen closed.The two atrio-ventricular valves have a more complicated structure. The main closure of theopening between the atrium and ventricle is achieved by the atrio-ventricular valve flaps. Thereare three main valve flaps (or cusps) on the right side of the heart and two main valve flaps onthe left side of the heart and these structures gave rise to the obsolete names tricuspid andbicuspid respectively. The edges of the valve flaps are supported by numerous connective tissuecords called chordae tendinae (tendinous cords). Conical mounds of heart muscle (i.e., papillarymuscle) serve as anchors for the chordae tendinae to the ventricle walls. Several of thesepapillary muscles (finger-like muscles) show up well on this model.LAYERS:Three layers make up the wall of the heart. From outside to inside they are named theepicardium, myocardium and endocardium. Start with the appearance of these three layers on thedetachable piece of the big heart model. You should then be able to find the layers elsewhere onthe model.All parts of the inside of the heart, including the heart wall, papillary muscles, chordae tendinaeand valve flaps, are covered by a thin layer named the endocardium (simple squamous epithelialtissues). Blood inside the heart chambers is actually in contact only with the endocardium. Themission of the endocardium is to prevent inappropriate adhesion of platelets to its surface, thiswould result in a blood clot (thrombosis). This endothelial layer is continuous throughout thevasculature.The myocardium of the ventricles is represented on the big heart model by a dark red color –indicative of the color of muscle. On the anterior surface of the heart a square segment (i.e.,window) of the myocardium has been removed to show that the myocardium consists of severallayers and that the muscle fibers in the different layers run at angles to one another. Thisprovides different planes for contraction. Only the myocardium contains cardiac muscle tissue.(The walls of the atria also have a myocardial layer, but it is not clearly shown on this model.)
The epicardium covers the outer surface of the entire heart and the anterior surface of this piece.It is shown as a rather thin, yellow layer which has been partly cut away. The yellow colorrepresents adipose tissue which commonly builds up in the epicardium. Another name for theepicardium is the visceral pericardium. This is the connective tissue sac that encloses the heart.SEPTA (Walls) BETWEEN THE ATRIA AND VENTRICLESThe word septum means "wall" (as in nasal septum) (plural=septa). There are two septa in theheart, the interventricular septum and the interatrial septum. The interventricular septum is, asthe name implies, a wall that lies between the two ventricles. To locate it, put a finger in the leftventricle and a thumb in the right ventricle. When you squeeze together, you will be pinching thethick interventricular septum. The other septum, the interatrial septum, occupies a positionbetween the atria. On this model, the aorta occupies the front part of the interatrial septum. Usethe thumb and finger method to locate the posterior part of this septum.A less distinct septa also exists between the right and left atria. During your existence as a fetus,there was a hole in your heart at this location called a Foramen Ovale. Sometimes you can see asmall divit (place where the septum is very thin) on the surface of the interatrial septum wherethis structure used to be (try to find it on the fresh pig heart). In about 80% of the population thishole is sealed. The other 20% of the population is said to have a patent foramen ovale (PFO).Often we do not discover this “hole” until relatively late in life because the heart is veryadaptable when you are young, but sometimes can’t keep up with the increased work load as youget older. When you were born a flap of tissue quickly sealed this hole (assuming your heart ishealthy), fixing the hole as an adult requires surgery via catheter-based closure, however in manycases the individual would simply be treated with anticoagulants like warfarin (Coumadin) orclopidrogrel (plavix) to prevent the formation of a thromosis within this structure.CORONARY ARTERIESThe Right Coronary artery (typically larger) and the Left coronary artery (typically smaller) exitthe aorta right behind the left semilunar valves. The Right Coronary artery supplies the rightventricle and atrium and crosses the right atrioventricular sulcus and usually becomes theposterior interventricular artery supplying the posterior aspects of the ventricles.The left coronary artery is a short segment that splits into two parts: the anterior interventricularartery and the circumflex branch of the left coronary artery. The Anterior Interventricular Artery(also called Left Anterior Descending or LAD) is easy to find in the sulcus along the anteriorsurface of the heart. The circumflex branch of the left coronary artery delivers blood to thelateral aspects of the left ventricle and is located in a left atrioventricular groove between theatria and ventricles and protected by the epicardial fat that covers it. It is usually the left coronaryartery and its branches that create problems with respect to heart attacks because the left side ofthe ventricle (that they supply) has to generally do more work than the right.The left coronary artery is sometimes called the left common coronary artery, it is also oftentimes called the “Widow Maker”. This short vessel supplies blood to both the circumflex ANDLAD, and a clot here means the entire anterior aspect of the left ventricle is not delivered withoxygen. As a result the left ventricular tissue dies and pumping into the aorta stops (massiveheart attack) and the individual dies. The left anterior descending artery is often where arterialstents (they look like small wire springs) are placed to “open up” a clogged coronary arterybecause there are a large number of bifurcations where atherosclerotic plaques can accumulate.
The coronary arteries that supply the myocardium with oxygenated blood run along the surfaceof the epicardium. When the myocardial tissues use the oxygen the blood becomesdeoxygenated and it enters veins. The deoxygenated blood enters veins that travel to the surfaceof the epicardium. A small amount of deoxygenated venous blood also drains directly into theventricle. It is important to remember that blood flow into, out of or through the myocardialtissue only occurs during diastole (heart rest), this is why a high heart rate is especially hard on aweak heart, you just plain don’t supply oxygen if it is contracting too much.When you have cardiac bypass surgery, the cardiologist removes a section of vein fromsomewhere in your body (typically the saphaneous vein in the leg although if you have varicoseveins and have had them stripped this is out) and splices the new vessels into and across wherethe old coronary artery was clogged shut. As a result oxygenated blood flow is restored to thetissues distal (downstream) to the occlusion and the heart can do more work again.ELECTRICAL CONDUCTION SYSTEM OF THE HEART (Only on big red heartmodels)Depolarization and contraction of myocardial tissues occurs along a finely controlled pathway.The electrical conducting system of the heart is a lecture topic that students often find difficult tounderstand. Try to get a 3-dimensional idea of its structure by studying the big, red heart model(the only model which shows it).The starting point for depolarization that stimulates the heart to contract is the sino-atrial node,commonly called the pacemaker of the heart. This is a patch of cells specialized in generatingaction potentials. Find this structure, represented in green, at the junction between the superiorvena cava and right atrium. The wave of depolarization moves across the atria andsimultaneously travels into a second important patch of cells of the conducting system called theatrio-ventricular node, also represented in green. Find this structure on the medial surface of theright atrium.Faint white lines (cellular pathways) can be traced from near the atrio-ventricular node down theentire length of the interventricular septum. This entire structure is called the Bundle of His(atrioventricular bundle) and carries the depolarization fro mthe AV node to the ventricle. The“common” part of the Bundle splits into two separate branches called the left and right bundlebranches that travel side-by-side down the interventricular septum to their respective right andleft ventricles. These non-contractile bundle branch tissues permit the wave of depolarization tobe conducted into the contractile tissues of the interventricular septum. The smallest branchesoutside of the septum are intended to represent the Purkinje fibers (the last part of the conductionsystem) that actually reach individual contractile cells.When you have had the lecture on the electrical conducting system, return to this model.Consider the sequence of electrical impulse transmission through each of the above parts, andthrough the skeleton of the heart, the atrial syncytium and the ventricular syncytium. Rememberthat the cells of the heart are connected into an electrical syncitium because there are gapjunctions between the cells, which ensure that if one cell is depolarized the next adjacent cell isalso depolarized.Note: While structures of the conduction pathway are “idealized” on the large heart model theyare difficult to observe on the preserved and fresh hearts. The conduction pathway questions onthe lab test will be limited to the large plastic heart model.
PART II: PRESERVED SHEEP HEART and FRESH PIG HEART:Find these same structures on the preserved and fresh hearts. When looking at the freshheart, try pulling on things and stretching things. See how durable this structure really is! Ifyou over stretch something and it tears, the pig will forgive you. A couple of hearts will befrozen for use on the lab exam later, so do not skip this section thinking there will not be afresh heart on the lab practical. The material below will help you walk through thesestructures once again.Important Tip! Take a metal probe or your finger and move it through the chamber openings.If you put the finger in one opening predict the place where it should reappear. On a test tryto be able to identify the structure at the end of the arrow or tip of the pin, but also try toidentify the reference structures on either side of what you look at.Find these external anatomical features: ANTERIOR INTERVENTRICULAR SULCUS -this fat-filled groove passes diagonally across the anterior surface of the heart. It contains branchcoronary arteries and veins. Use the anterior interventricular sulcus to locate the anteriorsurface of the heart. Now you know what is anatomical LEFT and RIGHT on the heart you arelooking at! POSTERIOR INTERVENTRICULAR SULCUS - this fat-filled groove is vertical. Itoccurs on the posterior surface of the heart. CORONARY SULCUS - this groove is usuallycompletely obscured by fat. It circles the heart between the atria and ventricles. Locate theRIGHT AURICLE and LEFT AURICLE - these ear-like flaps are gray in color. They are quitelarge and distinct on the sheep heart. RIGHT ATRIUM - the large cavity of this chamber of theheart is located posterior and inferior to the right auricle. SUPERIOR VENA CAVA - this veinis a thin-walled vessel which enters the right atrium from above. Locate its opening by probingthe superior wall of the right atrium from the inside with your finger. Often both the superior andinferior vena cava will be collapsed. (It is useful to remember that arteries have much thickerwalls than veins of the same size. Arteries usually retain their shape, while veins often collapse.)INFERIOR VENA CAVA - this vessel is difficult to find on the sheep heart because it adheresclosely to the posterior part of the heart. In the sheep heart, it enters the right atrium from thelower medial side. A probe passed through it will make an angle of about 90o with one passedthrough the superior vena cava. This orientation is quite different from the situation with thehuman inferior vena cava which is vertical in orientation. With these directions in mind, probefor the opening to this vessel.Find these Internal Structures: RIGHT ATRIOVENTRICULAR VALVE - this valve liesbetween the right atrium and right ventricle. The valve consists of valve flaps and chordaetendinae attached to papillary muscles. ATRIO-VENTRICULAR VALVE FLAPS - these thinnearly transparent pieces of tissue meet to close off the opening between the atrium and ventricleto prevent the backflow of blood. CHORDAE TENDINAE - these numerous thin connectivetissue cords are attached to the edges of the valve flaps. They prevent valve flap reversal.PAPILLARY MUSCLES - these irregularly shaped mounds of cardiac muscle can be found atvarious positions on the walls of the ventricle. They serve as passive anchors for the chordaetendinae. They do not act to pull the valve open. PULMONARY TRUNK - the term "trunk"refers to that undivided part of the vessel that splits to form the two main pulmonary arteries.PULMONARY SEMILUNAR VALVE - this valve can be found at the very first part of thepulmonary trunk. It consists of three somewhat shriveled-up, thin valve flaps. Semilunar valveshave no chordae tendinae or papillary muscles. From the pulmonary arteries blood flows throughbranch arteries to the capillaries in the lungs.
Oxygenated blood flows back to the heart via the pulmonary veins. LEFT AURICLE - this flapserves as a landmark for the location of the left atrium. LEFT ATRIUM - this chamber liesposterior to the left auricle. Determine its full extent by probing. PULMONARY VEINS - thesevessels are almost always cut off very short when the sheeps lungs are removed. Often only theholes, where they were attached, remain. Locate the stubs of the pulmonary veins or the openingswhere they were attached to the posterior surface of the left atrium by gently probing the wall ofthe atrium from the inside. LEFT ATRIOVENTRICULAR VALVE - this valve, like the rightatrioventricular valve in structure, can be found between the left atrium and left ventricle. Locateits valve flaps, chordae tendinae and papillary muscles. LEFT VENTRICLE - note the thickmyocardial wall of this chamber. The blood from the left ventricle exits by way of the aorta. Theconnection between the main chamber of the left ventricle and the aorta is difficult to find.Blood passes through the left atrioventricular valve (i.e., bicuspid valve), U-turns and passesbehind the medial valve flap to reach the aorta. AORTA - this large, thick-walled vessel extendsupward from the central axis of the heart. It arches off to the left and produces one major branch,the brachiocephalic artery. (The human aorta has three major branches off its arch.) AORTICSEMILUNAR VALVE - this valve is similar in structure to the pulmonary semilunar valve,consisting of three valve flaps. It occurs at the very base of the aorta. SEMILUNAR VALVEFLAPS - the attachment of these thin structures to the wall of the aorta can be easily observed inthe aortic semilunar valve. Their structure has been distorted by the preservative.CHECKLIST OF PARTS OF THE HEARTBase Apex Anterior/Posterior Left/RightAnterior Tricuspid or right atrio- Atrio-ventricular valve Circumflex branch ofinterventricular sulcus ventricular valve flap left coronary artery Pulmonary semilunar Anterior interventricularRight auricle Chordae tendinae valve artery Posterior interventricularLeft auricle Pulmonary trunk Papillary muscles artery Epicardium or visceralRight atrium Pulmonary arteries Sino-atrial node pericardiumLeft atrium Pulmonary veins Endocardium Atrio-ventricular node Atrio-ventricular Bicuspid or left atrio-Right ventricle Myocardium bundle ventricular valve Bundle of HisLeft ventricle Aortic semilunar valve Interventricular septum Rt/Lt Bundle BranchesSuperior vena cava Aorta Interatrial septum Purkinje Fibers Right and left coronary T.Q. Above Bold onInferior vena cava Semilunar valve flap arteries (origin on Large Heart Model aorta) Only!If you had a string that passes through the vena cava to the pulmonary artery, could you name thestructures it crosses?If you had a string at the pulmonary vein could you name the structures it crosses over prior toexiting the heart at the aorta?TIP: Whenever you pick up a heart, model or other, look for the anterior sulcus (largegunsight-like groove). This will be the anterior aspect of the heart, so now you know the
left and right sides. You can also identify where the great vessels enter and leave, this iscalled the superior end or the “base” and the inferior end called the apex is its opposite.PART III: ARTERIES AND VEINS OF THE TORSO MODELFind these blood vessels on the human torso model. In several places in this lab you will beasked to find the vessel/structure using a figure or table in the book. These figures andstructures may appear on the lab exam if they are listed on the “torso” checklist at the endof this lab. Pay special attention to items in bold and italics, these may also appear on test.ARTERIES: Remove the heart and lungs from the torso model. Find the pulmonary trunk andthe pulmonary arteries (Figure 20.19). They are painted blue to suggest that they carrydeoxygenated blood. Replace the heart and notice how short the pulmonary arteries are. Findtheir major branches in the lungs. If a thrombosis blocked blood from passing through thepulmonary artery, what would happen to the blood pressure in the pulmonary veins, the lungvasculature and the aorta or vena cava?Next locate the aorta on the heart. A small part of the ascending aorta is visible. Remove theheart and follow the aortic arch on the model. Note that it arches posteriorly and slightly to theleft and then begins to descend. Part of the descending thoracic aorta is visible. Note that itpasses behind the trachea. The TV movie star John Ritter died in 2004 when an aortic archaneurism ruptured causing massive hemorrhaging. What would have happened to his bloodpressure, blood volume, and heart rate when this occurred?The three major branches off the aortic arch proper are visible, although somewhat obscured bythe brachiocephalic vein. From right to left, these three branches are the: brachiocephalic trunk(artery), left common carotid artery and left subclavian artery. Trace the brachiocephalicartery upward until it splits into the right common carotid artery and the right subclavianartery (there is no left brachiocephalic artery because the left common carotid and leftsubclavian branch directly off of the aortic arch) which carries blood to the shoulder and arm.Follow both common carotid arteries up the neck. These vessels are called common becausethey will give rise to an internal and external branch distally. Look carefully and find the path ofthe left subclavian artery out toward the left shoulder and arm. (Figure 20.4, 20.21 and 20.23).Find the diaphragm that divides the peritoneal and thoracic cavities. Remove the abdominalviscera. Find the descending aorta, inferior to the diaphragm it is called the abdominal aorta.Note three stubs of major branch arteries that project anteriorly from it. The upper one, nearestthe diaphragm, is the celiac trunk. This vessel supplies blood to the abdominal viscera. Near therenal artery – the one to the kidney, locate the superior mesenteric arterys base. This vesselsupplies blood to the small intestines and some of the large intestine. The lowest unpaired vesselis the inferior mesenteric artery. This supplies blood to the distal end of the large intestine.You should have no trouble finding the paired renal arteries to the kidneys. Remember thatthese two kidneys receive up to about 25% (12.5% each) of the cardiac output when at rest.(Figure 20.21 and 20.27).Finally, locate the termination of the aorta in the lower peritoneal cavity where it splits to formthe right and left common iliac arteries. The common iliac arteries will branch into the internaland external iliac arteries. On the right side, the smaller internal iliac artery (figure 20.27) canbe seen along the pelvic wall near the rectum. This vessel provides blood to numerous otherarteries including the gluteal, vaginal uterine and middle rectal. The continuation of the commoniliac artery below the internal iliac artery is the larger external iliac artery. This artery is calledthe femoral artery after it exits the peritoneal cavity, this supplies blood to the leg. Assume
your leg was amputated at the knee as a result of fiery car crash (or a horrible Anatomyexperiment gone bad). Would you want the paramedic to put strong direct pressure over thesuperior ramus of the pubic bone OR over the lesser sciatic notch of the ischium (please do nottry amputation at home or in lab!). Why would you choose this place for applying thepressure to stop the bleeding?VEINSLet us begin with the pulmonary veins (Figure 20.20). On this model they are painted redindicating that the blood they carry from the lungs to the heart is oxygenated. Find thepulmonary branch veins in the lungs. On the heart, inferior to the pulmonary arteries, two leftpulmonary veins and four right pulmonary vein branches are shown. Usually the branches cometogether to form two main veins that enter the left atrium on each side.Next, look at the Torso Model and Figure 20.33, find the superior vena cava. Trace it upwarduntil it splits into the right and left brachiocephalic veins. They extend laterally as the two verylarge internal jugular veins. The external jugular veins are not shown on this model. Theywould typically drain into the superior vena cava just distal to the internal jugular veins. If aperson applies light pressure to the surface of the skin to one side of the neck you can often seeblood pool in the external jugular vein, if you palpate the skin you can feel the pooled bloodinside the vessel. CAUTION: do this at your own risk and do not try this if you are olderthan 40 years of age or have circulatory disease! Instead, think about what a tight collaron a button up shirt might do and the appearance you might have with respect to this vein?Lateral to the base of the internal jugular veins, the continuation of the brachiocephalic vein thatcarries blood from the arm, is the subclavian vein. Note that this vein is actually "beneath theclavicle", as its name implies. Distal to the clavicle this vein is called the axillary vein. Why?Return to the heart and locate the stub of the inferior vena cava where it is attached to the rightatrium. Find the next segment of it as it passes through the liver. The rest of the inferior venacava can be located to the right of the aorta on the posterior abdominal wall. Trace it to itstermination where it splits to form the common iliac veins. By analogy with the arteries of thesame name, find the following veins: renal veins, internal iliac veins, external iliac veins andfemoral veins.Blood vessels tend to vasodilate (open-up) in response to local heat and the body has somespecial tricks it can use to dissipate heat when too warm, or to conserve body heat when exposedto the cold. When excess heat is present the smooth muscle tends to relax and the vessel willdilate allowing blood to enter them and fill distant capillaries. When smooth muscle gets cold ittends to cause the vascular smooth muscle to constrict making it difficult for blood to enter avessel. The blood draining the regions below the knee have two veins they can take to return tothe external iliac and vena cava. The returning blood can travel deep in the leg next to the femurbone through the femoral vein or it can travel just under the surface of the skin of your innerthigh in the saphenous vein.When you exercise the blood is warm and causes the smooth muscle on the saphenous vein torelax and dilate, making it easy for blood to travel through it. As a result heat can easily radiateout of the superficial saphenous vein warming adjacent tissue and allowing heat transfer from thesurface of the skin to the surrounding air. This safely cools the blood before it enters yourbody’s core. When you are cold, the smooth muscle of the saphenous vein constricts and bloodis diverted to the deeper femoral vein. Blood coming from the femoral vein has not lost as muchof its warmth, so it is not too cold when it enters the body cavity next to your internal organs.
When the saphenous vein is removed for heart bypass, the person will of course be less able toradiate heat when they exercise because all venous blood must return via the femoral vein.It is possible to find the hepatic portal vein (and some of its branches) on this model and onFigure 20.38. Look on the detachable piece containing the pancreas. On the posterior surface ofthis piece, the hepatic portal vein is shown in purple. Its continuation is also depicted on the livernear the common bile duct. The hepatic portal vein carries blood that was deoxygenated by thecells of the intestine and abdominal organs, it carries nutrients from the food you ate and mayalso carry toxins that entered the blood in the gut. The blood is “cleaned up” in the liver prior todelivery by the hepatic veins into the vena cava and the heart proper. The red vessel traveling tothe liver from the celiac artery is the hepatic artery. What was the importance of this portalsystem? Why does the liver also need a separate system that brings oxygenated blood via thehepatic artery (branched of cephalic artery near diaphragm? Would the use of bloodcontaining very little oxygen help an important organ function well?)PART IV: BLOOD VESSELS OF THE FEMALE CADAVER:Be sure to be able to identify the following blood vessels on the female cadaver. CadaverArteries: Aortic Arch, Abdominal Aorta, Renal Arteries, Common Iliac Arteries CommonCarotid arteries, and Subclavian arteries. Cadaver Veins: Vena Cava (Inferior/Superior),Common Iliac veins, Femoral Veins, and Saphenous veins.PART V: HISTOLOGY OF ARTERIES AND VEINS:The histology of the artery and vein on the artery, vein, and nerve slide (Slide #3) was examinedlast semester and it will now be reviewed again. First, relocate the artery and the vein. Recallthat the artery has a much thicker wall than the vein. Also note that the wall of the artery containslots of smooth muscle tissue (thick walled) , while the veins wall contains less smooth muscle(thin walled). These differences in anatomy illustrate functional differences in the vessels. Youcan also find cross sections of nerves traveling along with the artery and nerve in aneurovascular bundle. The nerves are solid structures without a lumen. At 40X you should beable to see cross sections of nerve fibers which have a dot-like axon in the center of a clearmyelin sheath.Each of these vessels has three layers or "coats" called tunics (See Figure 20.2 Saladin). Thenames of the three layers are, from inside to outside, the tunica intima, tunica media and tunicaexterna. Let us study the layers of the artery first. The tunica intima of the artery has twodistinctive parts. Next to the blood is the layer of simple squamous epithelial tissue we studiedpreviously. The name given to this layer in an artery or elsewhere in the circulatory system is theendothelium. You will have to look very carefully to see the thin flattened cells of theendothelium. (Remember that they are cut in cross section.)Beneath the endothelium is the elastic membrane. This structure is the distinctly solid andrippled layer that literally looks like a rubber band. Both the endothelium and the elasticmembrane are parts of the tunica intima. Together they act to provide a smooth, flexible surfaceover which blood can flow, the elastic properties let vessels snap back into place after beingstretched.The second major layer is the tunica media. In all but the largest (elastic) arteries this layer ismade up of circularly arranged smooth muscle tissue. When these smooth muscle cells constrictthe lumen (inside open diameter) of a blood vessel decreases. This strong layer must also resist
the high pressure of the blood in the artery. It also can contract to help control blood pressure andblood flow.Name a paracrine messenger that can be created by platelets and could cause constrictionof the smooth muscle in an artery. What would this do to the delivery of blood and oxygento a region of the heart supplied by the artery? In a healthy blood vessel, what cellsproduce prostacyclin? How would prostacyclin reduce the release of paracrine messengersand constriction? If the endothelium was injured, perhaps due to materials in cigarettesmoke, what might the blood vessel do?Surrounding the tunica media, and often blending into the surrounding tissue, is the tunicaexterna. This outer layer of the artery consists of loose connective tissue that helps hold theartery in position among surrounding organs. Next, we will compare the structure of the artery tothat of a vein. The tunica intima of the vein has an observable lining of endothelium like theartery but the elastic membrane is usually not visible. The thinner tunica media of the veincontains much dense connective tissue, but relatively little smooth muscle tissue. Finally, thetunica externa of the vein is relatively much thicker than the corresponding layer of the artery.It makes up much of the thickness of the wall of the vein. It probably strengthens the wall of thevein as well as holds the vein in place.CHECKLIST FOR ARTERIES AND VEINS OF THE TORSO MODELArteries Arteries Veins VeinsPulmonary trunk Pulmonary arteries Pulmonary veins Superior vena cavaAscending aorta Aortic arch R&L Brachiocephalic veins Internal jugular veinsDescending thoracic aorta Brachiocephalic artery Subclavian vein Inferior vena cavaLeft common carotid artery Left subclavian artery Common iliac veins Renal veinsRight common carotid artery Right subclavian artery Internal iliac veins External iliac veinsAbdominal aorta Celiac trunk Femoral veins Greater saphenous veinSuperior mesenteric artery Inferior mesenteric artery Hepatic portal veinRenal artery Common iliac artery Portal SystemInternal iliac artery External iliac artery Diaphragm (is a muscular Diaphragm is used as a sheet between thoracic and reference point for names of peritoneal cavities) arteries and veins.Femoral artery Checklist for Vessel Histology simple squamous Artery (thick wall) Vein (thin wall) Nerve endothelium epithelial tissue elastic membrane tunica intima of A&V tunica media of A&V tunica externa of A&V Endothelial cell Where are thromboxane, prostacyclin and nitric oxide produced? What do they do to smooth muscle cells?