NSC 216 HUMAN ANATOMY 3 - Nou.edu.ng

COURSE MATERIALSTable of ContentsModule 1- Cardiovascular SystemUnit 1- Heart and Blood VesselsUnit 2 - BloodUnit 3- Lymphatic SystemModule 2- Respiratory SystemUnit 1- Anatomy of the lungsUnit 2- Developmental anatomy of the lungsUnit 3- Anatomy of the diaphragm and mediastinumModule 3- Digestive systemUnit 1- Anatomy of the StomachUnit 2- Anatomy of the Small IntestineUnit 3- Anatomy of the Large IntestineUnit 4- Other Accessory Organs of Digestion

MODULE 1- CARDIOVASULAR SYSTEMIntroductionMost buildings in this century have a water pump system installed which comprises thepumping machine, the pipes that distribute water to the different parts of the building and thecontrol valves that regulates the flow. So, you can liken the water pump system to thecardiovascular system with the pipes being the vessels, the pumping machine being the heartand the valves, well, being the valves. The heart is a biological pump that works with miles ofblood vessels to supply nutrients, oxygen and also take wastes away to other systems fordisposal. In this module, we would cover the structures of the various organs that make up thecardiovascular system.Module Objectives: At the end of this module, you should be able to:i. Discuss the structures of the various organs that make up the cardiovascular systemCONTENTUnit 1: Heart and Blood VesselsUnit 2: BloodUnit 3: Lymphatic SystemUNIT ONE- THE HEART AND BLOOD VESSELSCONTENT1.0 Introduction2.0 0bjectives3.0 Main Content3.1 Pericardium3.2 Gross anatomy of the heart3.3 Developmental and microanatomy of the heart3.4 Developmental and microanatomy of the great vessels4.0 Conclusion5.0 Summary6.0 Tutor Marked Assignments

6.1 Activity6.2 Tutor Marked Tests7.0 References1.0 IntroductionPeople always talk about the heart as the seat of control of emotions. At one stage or the otherin your life, you must have fallen in love or had a broken heart. People often refer to the heartas if it were the seat of certain strong emotions. A very determined person may be described ashaving “a lot of heart”, and a person who has been disappointed romantically can be describedas having a “broken heart”. A popular holiday in February not only dramatically distorts theheart‘s anatomy but also attaches romantic emotions to it. One important reference, howeverabout the heart is that “without a functioning heart, there is no life”. The heart is a muscularorgan that is essential for life because it pumps blood through the body. Emotions are a productof brain function, not heart function but without the heart performing its functions efficiently,brain cells die within a short time! In this unit your knowledge of the structures and the organsin relations to the heart will be explored.2.0 ObjectivesAt the end of this unit, you should be able toi. Describe the location, size and shape of the heartii. Highlight the functions of the heartiii. List the parts and functions of the pericardiumiv. Contrast the three layers of the heart wall with respect to structure and functionv. With the aid of a well labeled diagram, describe the position of the heartvi. With the aid of a well labeled diagram, describe the pathway for the flow of blood throughthe heart chambers and large vessels associated with the heartvii. Describe the vasculature of the heart with the aid of a diagramviii. Describe structural variations in some abnormalities of the heart and the vessels.

ix. Explain what happens in pericardial effusion and pericarditis3.1 The PericardiumThe pericardium is a protective sheath that encloses the heart, it has two parts: the fibrouspericardium and the serous pericardium.Figure 1.1: The Heart and the Coverings

Fibrous pericardiumThe pericardium has an outer single-layered fibrous sac that encloses the heart and the roots ofthe great vessels, fusing with the adventitia of these vessels. Its broad base overlies the centraltendon of the diaphragm, with which it is inseparably blended, both being derived from theseptum transversum.The phrenic nerves lie on the surface of the fibrous pericardium and the mediastinal pleura isadherent to it, wherever the two membranes are in contact with each other. The fibrouspericardium is connected to the back of the sternum by weak sternopericardial ligaments.Serous pericardiumA serous layer lines the inside of the fibrous pericardium, where it is reflected around the rootsof the great vessels to cover the entire surface of the heart, where it forms the epicardium.Between these parietal and visceral layers there are two sinuses: the transverse sinus and theoblique sinus of the pericardium.The transverse sinus is a passage above the heart, between the ascending aorta and pulmonarytrunk in front and the superior vena cava, left atrium and pulmonary veins behind. The obliquesinus is a space behind the heart, between the left atrium in front and the fibrous pericardiumbehind, posterior to which lies the oesophagus. A hand passed from below easily enters theoblique sinus, but the fingertips can only pass up as far as a double fold of serous pericardiumthat separates the oblique and transverse sinuses from each other.It is through the transverse sinus that a temporary ligature is passed to occlude pulmonary trunkand aorta during pulmonary embolectomy and cardiac operations.Nerve supplyThe fibrous pericardium is supplied by the phrenic nerve. The parietal layer of serouspericardium that lines it is similarly innervated, but the visceral layer on the heart surface isinsensitive. Pain from the heart (angina) originates in the muscle or the vessels and istransmitted by sympathetic nerves. The pain of pericarditis originates in the parietal layer only,and is transmitted by the phrenic nerve.

Blood supplyPericardial blood supply is derived from the internal thoracic artery, its pericardiophrenic andmusculophrenic branches, bronchial arteries and the thoracic aorta. The veins drain into theazygos system.Pericardial drainageA needle inserted in the angle between the xiphoid process and the left seventh costal cartilageand directed upwards at an angle of 45, towards the left shoulder, passes through the centraltendon of the diaphragm into the pericardial cavity. The creation of a small pericardial windowsurgically through the same route, or through the anterior end of the fourth intercostal space,provides more effective drainage.

3.2 Gross anatomy of the heartThe heart, slightly larger than a clenched fist, is a double, self-adjusting suction and pressurepump, the parts of which work in unison to propel blood to all parts of the body. The right sideof the heart (right heart) receives poorly oxygenated (venous) blood from the body through theSVC and IVC and pumps it through the pulmonary trunk and arteries to the lungs foroxygenation. The left side of the heart (left heart) receives well-oxygenated (arterial) bloodfrom the lungs through the pulmonary veins and pumps it into the aorta for distribution to thebody.Figure 1.2: The Anterior View of the HeartChambers of the heartThe heart has four chambers: right and left atria and right and left ventricles. The atria arereceiving chambers that pump blood into the ventricles (the discharging chambers). Thesynchronous pumping actions of the heart's two atrioventricular (AV) pumps (right and leftchambers) constitute the cardiac cycle. The cycle begins with a period of ventricular elongationand filling (diastole) and ends with a period of ventricular shortening and emptying (systole).

Two heart sounds are heard with a stethoscope: a lub (1st) sound as the blood is transferredfrom the atria into the ventricles and a dub (2nd) sound as the ventricles expel blood from theheart. The heart sounds are produced by the snapping shut of the one-way valves that normallykeep blood from flowing backward during contractions of the heart.The wall of each heart chamber consists of three layers, from superficial to deep: Endocardium, a thin internal layer (endothelium and subendothelial connective tissue)or lining membrane of the heart that also covers its valves. Myocardium, a thick, helical middle layer composed of cardiac muscle. Epicardium, a thin external layer (mesothelium) formed by the visceral layer of serouspericardium.Fig. 1.3: Wall of the heart

Contraction of the heartThe walls of the heart consist mostly of myocardium, especially in the ventricles. When theventricles contract, they produce a wringing motion because of the double helical orientationof the cardiac muscle fibers. This motion initially ejects the blood from the ventricles as theouter (basal) spiral contracts, first narrowing and then shortening the heart, reducing the volumeof the ventricular chambers. Continued sequential contraction of the inner (apical) spiralelongates the heart, followed by widening as the myocardium briefly relaxes, increasing thevolume of the chambers to draw blood from the atria.The muscle fibers are anchored to the fibrous skeleton of the heart. This is a complexframework of dense collagen forming four fibrous rings (L. anulifibrosi) that surround theorifices of the valves, a right and left fibrous trigone (formed by connections between rings),and the membranous parts of the interatrial and interventricular septa.Fig.1.4: The Musculature and Valves of the HeartThe fibrous skeleton of the heart:i. Keeps the orifices of the AV and semilunar valves patent and prevents them from beingoverly distended by an increased volume of blood pumping through them.

ii. Provides attachments for the leaflets and cusps of the valves.iii. Provides attachment for the myocardium, which, when uncoiled, forms a continuousventricular myocardial band that originates primarily from the fibrous ring of the pulmonaryvalve and inserts primarily into the fibrous ring of the aortic valve.iv. Forms an electrical insulator, by separating the myenterically conducted impulses of theatria and ventricles so that they contract independently and by surrounding and providingpassage for the initial part of the AV bundle of the conducting system of the heart (discussedlater in this chapter).DemarcationsExternally, the atria are demarcated from the ventricles by the coronary sulcus (atrioventriculargroove), and the right and left ventricles are demarcated from each other by anterior andposterior interventricular (IV) sulci (grooves). The heart appears trapezoidal from an anterioror posterior view, but in three dimensions it is shaped like a tipped-over pyramid with its apex(directed anteriorly and to the left), a base (opposite the apex, facing mostly posteriorly), andfour sides.The apex of the heart: Is formed by the inferolateral part of the left ventricle. Lies posterior to the left 5th intercostal space in adults, usually approximately 9 cm (ahand's breadth) from the median plane. Remains motionless throughout the cardiac cycle. Is where the sounds of mitral valve closure are maximal (apex beat); the apex underliesthe site where the heartbeat may be auscultated on the thoracic wall.The base of the heart: Is the heart's posterior aspect (opposite the apex). Is formed mainly by the left atrium, with a lesser contribution by the right atrium. Faces posteriorly toward the bodies of vertebrae T6-T9 and is separated from them bythe pericardium, oblique pericardial sinus, esophagus, and aorta.

Extends superiorly to the bifurcation of the pulmonary trunk and inferiorly to thecoronary sulcus. Receives the pulmonary veins on the right and left sides of its left atrial portion and thesuperior and inferior venae cavae at the superior and inferior ends of its right atrialportion.The four surfaces of the heart are the: Anterior (sternocostal) surface, formed mainly by the right ventricle. Diaphragmatic (inferior) surface, formed mainly by the left ventricle and partly by theright ventricle; it is related mainly to the central tendon of the diaphragm. Right pulmonary surface, formed mainly by the right atrium. Left pulmonary surface, formed mainly by the left ventricle; it forms the cardiacimpression in the left lung.The heart appears trapezoidal in both anterior and posterior views.The four borders of the heart are the: Right border (slightly convex), formed by the right atrium and extending between theSVC and the IVC. Inferior border (nearly horizontal), formed mainly by the right ventricle and slightly bythe left ventricle. Left border (oblique, nearly vertical), formed mainly by the left ventricle and slightlyby the left auricle. Superior border formed by the right and left atria and auricles in an anterior view; theascending aorta and pulmonary trunk emerge from this border and the SVC enters itsright side. Posterior to the aorta and pulmonary trunk and anterior to the SVC, thisborder forms the inferior boundary of the transverse pericardial sinus.The pulmonary trunk, approximately 5 cm long and 3 cm wide, is the arterial continuation ofthe right ventricle and divides into right and left pulmonary arteries. The pulmonary trunk andarteries conduct low-oxygen blood to the lungs for oxygenation.

Figure 1.5: The Posterior View of the HeartVasculature of heartThe blood vessels of the heart comprise the coronary arteries and cardiac veins, which carryblood to and from most of the myocardium. The endocardium and some subendocardial tissuelocated immediately external to the endocardium receive oxygen and nutrients by diffusion ormicrovasculature directly from the chambers of the heart. The blood vessels of the heart,normally embedded in fat, course across the surface of the heart just deep to the epicardium.Occasionally, parts of the vessels become embedded within the myocardium. The blood vesselsof the heart are affected by both sympathetic and parasympathetic innervation.Arterial supply of heart.The coronary arteries, the first branches of the aorta, supply the myocardium and epicardium.The right and left coronary arteries arise from the corresponding aortic sinuses at the proximalpart of the ascending aorta, just superior to the aortic valve, and pass around opposite sides ofthe pulmonary trunk. The coronary arteries supply both the atria and the ventricles; however,

the atrial branches are usually small and not readily apparent in the cadaveric heart. Theventricular distribution of each coronary artery is not sharply demarcated.Figure 1.6: The Blood Supply of the HeartThe right coronary artery (RCA) arises from the right aortic sinus of the ascending aorta andpasses to the right side of the pulmonary trunk, running in the coronary sulcus. Near its origin,the RCA usually gives off an ascending sinuatrial nodal branch, which supplies the SA node.The RCA then descends in the coronary sulcus and gives off the right marginal branch, whichsupplies the right border of the heart as it runs toward (but does not reach) the apex of the heart.After giving off this branch, the RCA turns to the left and continues in the coronary sulcus tothe posterior aspect of the heart. At the posterior aspect of the crux (L. cross) of the heart—thejunction of the interatrial and interventricular (IV) septa between the four heart chambers—theRCA gives rise to the atrioventricular nodal branch, which supplies the AV node. The SA andAV nodes are part of the conducting system of the heart.

Typically, the RCA supplies: The right atrium. Most of right ventricle. Part of the left ventricle (the diaphragmatic surface). Part of the IV septum, usually the posterior third. The SA node (in approximately 60% of people). The AV node (in approximately 80% of people).The left coronary artery (LCA) arises from the left aortic sinus of the ascending aorta, passesbetween the left auricle and the left side of the pulmonary trunk, and runs in the coronarysulcus. In approximately 40% of people, the SA nodal branch arises from the circumflex branchof the LCA and ascends on the posterior surface of the left atrium to the SA node. As it entersthe coronary sulcus, at the superior end of the anterior IV groove, the LCA divides into twobranches, the anterior IV branch (clinicians continue to use LAD, the abbreviation for theformer term ―left anterior descending‖ artery) and the circumflex branch.The anterior IV branch passes along the IV groove to the apex of the heart. Here it turns aroundthe inferior border of the heart and commonly anastomoses with the posterior IV branch of theright coronary artery. The anterior IV branch supplies adjacent parts of both ventricles and, viaIV septal branches, the anterior two thirds of the IVS. In many people, the anterior IV branchgives rise to a lateral branch (diagonal artery), which descends on the anterior surface of theheart.The smaller circumflex branch of the LCA follows the coronary sulcus around the left borderof the heart to the posterior surface of the heart. The left marginal branch of the circumflexbranch follows the left margin of the heart and supplies the left ventricle. Most commonly, thecircumflex branch of the LCA terminates in the coronary sulcus on the posterior aspect of theheart before reaching the crux of the heart, but in approximately one third of hearts it continuesto supply a branch that runs in or adjacent to the posterior IV groove.Typically, the LCA supplies:i. The left atrium.ii. Most of the left ventricle.iii. Part of the right ventricle.

iv. Most of the IVS (usually its anterior two thirds), including the AV bundle of the conductingsystem of the heart, through its perforating IV septal branches.v. The SA node (in approximately 40% of people).Venous drainage of the heartThe heart is drained mainly by veins that empty into the coronary sinus and partly by smallveins that empty into the right atrium. The coronary sinus, the main vein of the heart, is a widevenous channel that runs from left to right in the posterior part of the coronary sulcus. Thecoronary sinus receives the great cardiac vein at its left end and the middle cardiac vein andsmall cardiac veins at its right end. The left pos

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