CARDIOVASCULAR SYSTEM

1. CARDIOVASCULAR SYSTEM Dr Ünal USLU

2. INTRODUCTION • The Circulatory System consist of THREEmajor components: • The Heart • The Blood Vascular System • The LymphVascular System • The heart, a modified blood vessel.This is specialized as adouble pump for propulsion of blood. • The cardiovascular system consists of a pump represented bythe heart and blood vessels, • This systemprovide the route by whichblood circulates to and from all parts of the body. • The heart pumps the blood through the arterial system undersignificant pressure; blood is returned to the heart under lowpressure with the assistance of negative pressure in the thoraciccavity during inspiration and compression of the veins byskeletal muscle. • The blood vessels are arranged so that blooddelivered from the heart quickly reaches a network of narrow,thin-walled vessels—the blood capillaries—within or in proximityto the tissues in every part of the body. • Blood from the body enters the right side of the heart and is pumped to the lungs. The left side of the hearth receives the blood from the lungs and distubutes it to all other organs and tissues of the body.

4. CIRCULATION • Two circuits distribute blood in the body: the systemicandthe pulmonary circulations. • Pulmonary circulation conveys blood from the heart tothe lungs and from the lungs to the heart. • Systemic circulation conveys blood from the heart toother tissues of the body and from other tissues of the body to the heart. • In some partsof the systemic circulation it is modified so that a vein or anarteriole is interposed between two capillary networks; these vessels constitute a portal system. • Venous portal systems occur in vessels carrying blood to the liver, namely, the hepaticportal system (portal vein), • In vessels leading to thepituitary, the hypothalamic–hypophyseal portal system.

5. PART OF CIRCULATION • The arteries, a series of afferent vessels, which become smaller as they branch. They distribute nutritients, oxygen and hormones to all parts of the body. • The capillaries, a network of small, thin-walled vessels through whose walls the interchange between blood and tissue occurs. • The veins, the afferent vessels to the hearth, which join into system of larger vessels that convey the cellular products of metabolism.

6. GENERAL FEATURES OF ARTERIS AND VEINS • Layers of Vascular Wall: • The walls of arteries and veins are composed of three layerscalledtunics. • The three layers of the vascular wall, from the lumen outward, are the following: • Tunica Intima • Tunica Media • Tunica Adventitia

7. TUNICA INTIMA • The tunica intima, the innermost layer of the vessel, consistsof three components: • (a) a single layer of squamousepithelial cells, the endothelium; • (b) the basal lamina ofthe endothelial cells (a thin extracellular layer composedchiefly of collagen, proteoglycans, and glycoproteins); • (c) the subendothelial layer, consisting of loose connectivetissue. • Occasional smooth muscle cells are found inthe loose connective tissue. • The subendothelial layer of theintima in arteries and arterioles contains a sheetlike layer orlamella of fenestrated elastic material called the internal elastic membrane.

8. TUNICA MEDIA • The tunica media, or middle layer, consists primarily ofcircumferentially arranged layers of smooth muscle cells. • In arteries, this layer is relatively thick and extends fromthe internal elastic membrane to the external elasticmembrane. • The external elastic membrane is a layer ofelastin that separates the tunica media from the tunica adventitia. • Variable amounts of elastin, reticular fibers, andproteoglycans are interposed between the smooth musclecells of the tunica media. • All of the extracellular components of the tunica media areproduced by the smooth muscle cells.

9. TUNICA ADVENTITIA • The tunica adventitia, or outermost connective tissuelayer, is composed primarily of longitudinally arrangedcollagenous tissue and a few elastic fibers. • The tunica adventitiaranges from relatively thin in most of the arterialsystemtoquite thick in the venules and veins, where it is the majorcomponent of the vessel wall. • In addition, the tunica adventitiaof large arteries and veins contains a system of vesselscalled the vasa vasorumthat supplies blood to thevascular walls themselves, as well as a network of autonomicnerves called nervivascularisthat control contractionof the smooth muscle in the vessel walls.

10. I. ARTERIESA. ELASTIC ARTERIES • This group includes the aorta and its largest main branches, the brachiocephalic, the common carotid, the subclavian, and the common illiac. • Functions : The elastic arteries absorb some of the pulse beat by the distention of the elastic tissue within their walls and make the blood flow less intermittent.

11. CLINICAL CORRELATION: ATHEROSCLEROSIS • Atherosclerotic lesions are the most common acquiredabnormality of blood vessels. • More than half of the annualdeaths in the United States are related to complicationsof atherosclerotic disease, which includes ischemicheart disease , myocardial infarction,stroke, and gangrene of the limbs. • Lesions develop primarilyin the tunica intima of large elastic arteries followingendothelial injury, which leads to endothelialdysfunction. • Factors that predispose to endothelial injuries include low-LDL cholesterol hyperlipidemia, hyperglycemia (in diabetes), hypertension, increased toxinlevels associated with cigarette smoking, and certain viraland bacterial infections caused by cytomegalovirus(C MV) or Chlamydia p neumoniae, respectively. • Alteredfunction of vascular endothelium leads to increased permeabilityto LDL cholesterol and increased adherence ofwhite blood cells to the endothelium. • Endothelial injury increasesthe production of reactive oxygen species such as O2 , H2O2, O H, and ONOO, which in turn oxidizeLDL in the tunica intima of the artery.

12. CLINICAL CORRELATION: ATHEROSCLEROSIS • In response to thisinjury, monocytes from the bloodstream enter the tunicaintima and differentiate into macrophages. • Macrophagesphagocytize oxidized LDL, slowly transforming themselvesinto foam cells with a characteristic spongy appearanceof the cytoplasm loaded with lipid-containing vesicles. • Foam cells and infiltrated T lymphocytes form the initialatherosclerotic lesion, or fatty streak. • This lesion undergoesfurther remodeling and growth into fibrofattyplaqueas smooth muscle cells migrate from the media and fibroblastsform a protective capsule of connective tissue. • A thick layer of fibrous connective tissue containingscattered smooth muscle cells, macrophages,foam cells, T lymphocytes, cholesterol crystals, and celldebris is known as an atheromatous plaque. • Progressionof the plaque is marked by accumulation of lipid and lossof integrity of the endothelium. • In advanced lesions, bloodstasis and clotting (thrombosis) may lead to occlusion ofthe vessel. • Other changes seen in advanced lesions includethinning of the tunica media, calcification of accumulatedextracellular lipids, and necrosis within the lesion. • Progression from simple to complicatedlesions can be found in some people as early as their 20sand in most individuals by age 50 or 60 years.

13. A. ELASTIC ARTERIES • Microscopy : • Tunica Intima : The tunica intima of elastic arteries relatively thick and consist of; • An endothelial lining with its basal lamina • A subendothelial layer of connective tissue (Loose Connective Tissue) • Internal Elastic Membrane (lamina)

14. A. ELASTIC ARTERIES • Microscopy : • Tunica Media : The tunica media is the thickest of the three layers of elastic artery and consist of; • Elastin in the form of fenestrated sheet or lamellae between the muscle layer. • Smooth Muscle cells arranged in layers • Collagen Fibers and Ground Substance

15. A. ELASTIC ARTERIES • Microscopy : • Tunica Adventitia: In elastic arteries, the tunica adventitia is a relatively thin connective tissue layer that is usually less than half the thickness of the tunica media. It consist of • Collagen Fibers • Elastic Fibers (not Lamellae) • Fibrobasts and Macrophages

16. B. MUSCULAR ARTERIES • This group includes all arteries of small and medium size • The walls of the muscular arteries are relatively thick, owing principally to the large amount muscle in the media. • Functions : They also called distrubuting arteries, since they distrubute blood to the various organs and regulate the volume of blood blood in response to varying functional demands.

17. B. MUSCULAR ARTERIES • Microscopy • Tunica Intimae: has tree definite layers; • Endothelium within thin basal lamina, • Subendothelial layer of delicate collagenous and elastic fibers, • And an internal elastic membrane that is prominent and an composed of closely interwoven elastic fibers.

18. B. MUSCULAR ARTERIES • Microscopy • The media consist almost exclusively of circularly smooth muscle cells. • There are small amounts of connective tissue, including collagenous, elastic and reticular fibres. • It contains collagenous and elastic fibres, mostly longitudinally arranged. • Elastic fibresare concentrated internally, where they commonly form a definite external elastic membrane.

19. C. ARTRIOLES • This vessels with a diameter of 100mm or less, have a tunica intima that consist of only endothelium and internal elastic membrane • The media is composed of one to five complete layers of smooth muscle and scattered elastic fibers. • The thin adventitia is a layer of loose connective tissue with longitudinally orriented collogenous and elastic fibers • No definite external elastic membrane is present. • Functions : They control the distrubution of blood the to capillary beds by vasodilatation and vasaconstriction. They are primer controllers of systemic blood pressure.

20. D. SPECIALIZED ARTERIES : • Certain arteries show pronounced structural deviation from the generalized plan. These variations reflect adoptions to special locations and functional demands. • Arteries of the lung have thin walls owing to a reduction in both muscle and elastic tissue. This reduces their resistance and thus is correlated with a lower blood pressure in the pulmonary circulation. • Arteries protected within the skull have thin wall and a well developedinternal elastic membrane. • The umblical arteries possess a media composed of two thick muscular layers, an inner longitidunal layer and an outer circular layer. • In the penile arteries, the intima is greatly thickened and contain many longitidunal muscle fibers. These groups of smooth muscle cells form the cores of intimal cushions that serve functionaly as valves.

21. II. CAPILLARIES • FUNCTIONS :Capillaries form blood vessel network that allow fluid containing gases, metabolites, and waste products to move through their thin walls. • MORPHOLOGY : They consist of a single layer of endothelial cells and their basal lamina. • The margin of endothelial cells are joined by tight junctions. • CLASSIFICATIONS : • Variation in the structure of the endothelial cell wall form the basis of a classification of capillaries into three major types. • CONNTINOUS TYPE • FENESTRATED • SINUSOIDAL (DISCONTINOUS)

22. CONTINOUS (Type I): • Type I capillaries are found in many tissues, including lung, muscle, skin and the central nervous system. • Characteristically, it contains fine filaments and numerous small vesicle along both the luminal and basal surfaces. • Functionally, they are involved two-way transport of fluid across the capillary wall. EM of different capillary endothelia. • A) continuous, endothelium in capillary. • B) fenestrated endothelium • C) continuous, thin endothelium of lung capillary. Note: basal lamina (1) under each one. Also pinocytotic vesicles (PV) and fenestrations (arrows).

23. II. CAPILLARIES (continue) 2. FENESTRATED (TypeII) : • Type II capillaries are found in the intestinal mucosa, many endocirne glands and the renalglomerulus. • Characteristically, it has pores (fenestrae) within attenuated endothelial cytoplasm.

24. 3. SINUSOIDAL • Sinusoidal capillaries or sinusoids, have luminal diameter much greater than that of normal capillaries. • The walls show wide gaps between endothelial cells. • The basal lamina is incomplete, and the endothelial cells are seperated from the paranchyma of organs only by a fine network of reticular fibers • Such capillaries are found inthe liver and in hemopoetic organs such as the bone marrow and spleen.

25. III.VEINS CLASSIFICATION : Venous blood vessels usually are classified into three groups: 1. Venules, the smallest venous branches. 2. Small to medium- sized veins 3. Large Veins GENERAL STRUCTURE : • Since blood within the veins is under much less pressure because of frictional losses than that within the arteries, veins accommodate a greater volume of blood. Hence, veins generally are larger in diameter than their corresponding arteries, and their walls are thinner, chiefly owing to a reduction in muscular and elastic components.

26. I. VENULES • Functions : • These venules participate in the interchange of metabolites between blood and tissues. • Structure : • Elastic fibers appear in the tunica intimae • Smooth muscle fibers are present between the intimae the outer fibrous sheet (adventitia). • In venules of 200 mm or more, the circular muscle fibers form a continuous layer (media), 1 to 3 cells thick • The adventitia is thick in comparison with the overall thinness of the wall and consist of longitudinally oriented collagenous fibers and scattered elastic fibers and fibroblast.

27. II. SMALL AND MEDIUM-SIZED VEINS • These include practically all the anatomically named veins and their principle branches, except the main trunks • STRUCTURE : • The tunica intimae is thin and consist of endothelium and a subendothelial layer. • In this type vein doesn’t form a distinct internal elastic membrane. • The media is thin also and is composed of small bundles of circularly arranged muscle fibers separated by collagenous and elastic fibers. • The Adventitia is well developed and the forms the bulk of the wall.

28. III. LARGE VEINS • The group includes the superior and inferior venae cava, the portal vein, and the main tributaries (branches) leading into these trunks. • The Intimae has the same structure as that of smaller veins, but it may be a little thicker. • The Media is poorly developed, and smooth muscle elements within it are much reduced or absent. • The Adventitia is the thickest of the three coats and contains many longitudinal muscle fibers, separated by collagenous fibers.

29. SPECIAL FUTURES OF CERTAİN VEINS • Some veins lack smooth muscle and thus are without a definite media. This group includes cerebral and meningeal veins, dural sinuses, and the veins of the retina, bones, penile erectile tissue, and the maternal components of the placenta. • Veins that are rich in smooth muscle include those of the gravid uterus and some mesenteric veins.

30. VENOUS VALVES • Many small and medium sized veins, particularly those of the lower limbs, possess valves that prevent retrograde blood flow. • Both surface of the valves are covered by endothelium

31. ARTERIOVENOUS ANASTOMOSES • In addition to capillary and sinusoidal connections between arteries and veins by arteriovenous anastamoses. • In the anastomoses most commonly between arterioles and venules. • Endothelium lies directly upon a specialized tunica media comprising a sphincter. • When the shunt is closed arterial blood passes into the regular capillary bed. • When the shunt is open, much of the blood bypasses the capillary bed and passes directly in to the vein.

32. THE HEART • The Inner Layer, or ENDOCHARDIUM • The Middle Layer, or MYOCARDIUM • The Outer Layer, or EPICARDIUM • CARDIAC SKELETON • CARDIAC VALVES • IMPUSE - CONDUCTING SYSTEM of the HEART

34. HEART • The heart lies obliquely, about two-thirds on the left side ofthe thoracic cavity, in the middle mediastinum. • The spaceenclosed between sternum, vertebral column, diaphragm,and lungs. • It is surrounded by a tough fibrous sac, the pericardium, • which also contains the beginnings and ends of the • great vessels entering and leaving the heart. • Through the pericardium,the heart is strongly attached to the diaphragm andneighboring organs that lie in the thoracic cavity.

35. HEART:A. ENDOCARDIUM • The Endocardium is analougous the tunica intima of blood vessels. • Endocardium is lined by ENDOTHELIUM. • Beneath the endothelium (inner subendochardial layer) there is a subendothelial layer of fine collogenous fiber, a layer of relativelydense connective tissue.

36. A. ENDOCARDIUM • Outer subendocardial layer of loose connective tissue that binds the endocardium to the myocardium. • Subendocardial layer contains blood vessels, nerves, branches of the impulse-conducting systems.

37. B. MYOCARDIUM: • Myocardium other name is Tunica Media composed of cardiac muscles • Ventricles is arranged in two layers Superficial and Deep. • The superficial fibers run a spiral course • The deep fibers generally follow a circular course around each ventricle

38. B. MYOCARDIUM: • The muscle sheets of atria and ventricles are atachhed by way of their intertisial connective tissue (endomysium) to the central structure of the heart. • This structer called CARDIAC SKELETON.

39. C. EPICARDIUM: • The Epicardium (Visceral Pericardium) is a serous membrane covered externally by a single layer of mesothelial cells • Beneath the mesothelium, there is a relatively thick layer of areolar or adipose tissue. • The subepicardial layer contains the coranary blood vessels and nerves.

40. D. CARDIAC SKELETON: • A fibrous skeleton that consists of four fibrous ringssurrounding the valve orifices, two fibrous trigonesconnectingthe rings, and the membranous part of the interventricularand interatrialsepta. • The fibrous rings arecomposed of dense irregular connective tissue. • They encirclethe base of the two arteries, leaving the heart (aortaand pulmonary trunk) and the openings between theatria and the ventricles (right and left atrioventricular[AV] orifices) . • These rings provide theattachment site for the leaflets of all four valves of theheart that allow blood flow in only one directionthrough the openings. • The membranous part of the interventricularseptum is devoid of cardiac muscle; • The fibrous skeleton provides independentattachmentsfor the atrial and ventricular myocardium. • It also acts as an electrical insulator bypreventing the free flow of electrical impulses between atria and ventricles.

41. D. CARDIAC SKELETON: • MAIN COMPONENTS: • The Interventricular Septum or fibrous portion of the interventricular septum • The Anuli Fibrosi or Fibrous Ring that surround origin of the aorta and pulmonary artery and the atrioventricular canals. • Intervalvular fibrosa (The Trigona Fibrosa), masses of fibrous tissue between the arteriel foramine and atrioventricular canals.

43. E. CARDIAC VALVES: • THE ATRIOVENTRICULAR VALVES: Between atria and ventricles • THE SEMILUNAR VALVES: Between the ventricles and aorta and pulmonary artery. • Cardiac valves are reduplications of endocardium containing a core of dense connective tissue continuous with that of the anulifibrosi. • Heart valves are composed of connective tissue with overlying endocardium. • The heart valves attach to the complex framework of dense irregularconnective tissue that forms the fibrous rings and surroundsthe orifices containing the valves.

44. E. CARDIAC VALVES: • Eachvalve is composed of three layers. • The fibrosaforms the core of the valve and contains fibrousextensions from the dense irregular connective tissueof the skeletal rings of the heart. • The spongiosais loose connective tissue located on theatrial or blood vessel side of each valve. • The spongiosa acts as ashock absorber to dampen vibrations associated with theclosing of the valve. • In the aortic and pulmonary valves,spongiosalocated on the blood vessel side is called arterialis. • It corresponds to the loose connective tissue locatedon the atrial side of the AV (tricuspid and mitral) valves,which is called the auricularis. • The ventricularisis immediately adjacent to the ventricularor atrial surface of each valve and is covered with endothelium.

45. E. CARDIAC VALVES: • In the AV valves, the ventriculariscontinues into the chordae tendineae, which are fibrous,threadlike cords also covered with endothelium • They extend from the free edge of the AVvalves to muscular projections from the wall of the ventricles,which are called papillary muscles. • Valve cusps are normally avascular.

46. F. IMPULSE CONDUCTING SYSTEM of the HEART:

47. F. IMPULSE CONDUCTING SYSTEM of the HEART: • The system of specialized cardiac muscle fibers; this system consist of PURKINJE’s FIBERS. • Purkinje’s Fibers conducts heart beat that has originated in the sinoatrial node, the rhythmic pacemaker of the heart. • Purkinje’s fibers have a larger diameter than ordinary cardiac muscle fibers and contain relatively more sarcoplasm. • Myofibrils are reduced in number and usually are limited to the periphery of fibers.

48. F. IMPULSE CONDUCTING SYSTEM of the HEART: • An impulse begins at the sinoatrial node, which consist of a dense network of small Purkinje’s Fibers that peripherally are in continuity with atrial cardiac muscle fibers. • The impulse spreads via the specialized conducting fibers to the atrioventricular node. A dense mass of fibers located in the median wall of right atrium. • The node continues into a common stem, the atrioventricular bundle (or bundle of His), which divides into two trunks that lie beneath the endocardium on either side of interventricular septum. • These trunks terminate in a system of Purkinje Fiber’s that connect with ordinary cardiac muscle fibers of the two ventricles. Inner surface of the heart, with pale, large Purkinje fibers lying in the subendocardial layer. Endocardium (or intima) is above. The beginning of the myocardium (media, cardiac muscle) is below

49. CORANARY VASCULATURE • A coronary vasculature that consists of two coronary arteriesand cardiac veins. • The right and left coronary arteriesprovide the arterial blood supply to the heart. • Theyoriginate from the initial part of the ascending aortanearthe aortic valves and circle the base of the heart, withbranches converging toward the apex of the heart. • Venousdrainage of the heart occurs via several cardiac veins, mostof which drain into the coronary sinus located on the posteriorsurfaceof the heart. • The coronary sinus drains intoright atrium.

50. CLINICAL CORRELATION: HYPERTENSION • Hypertension, or high blood pressure, occurs in about25% of the population and is defined by a sustained diastolicpressure greater than 90 mmHg or a sustained systolicpressure greater than 140 mmHg. • Hypertension is often associatedwith atherosclerotic vascular disease and with anincreased risk of cardiovascular disorders such as strokeand angina pectoris. • In most cases of hypertension, theluminal diameter of small muscular arteries and arterioles isreduced, which leads to increased vascular resistance. • Restrictionin the luminal size may also result from active contractionof smooth muscle in the vessel wall, an increase inthe amount of smooth muscle in the wall, or both.