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INTRODUCTION TO CARDIOVASCULAR SYSTEM

INTRODUCTION TO CARDIOVASCULAR SYSTEM. COMPONENTS. Blood Heart Blood vessels. GENERAL ORGANIZATION. Cells of peripheral blood, suspended in plasma, circulate through the body in the blood vascular system.

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INTRODUCTION TO CARDIOVASCULAR SYSTEM

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  1. INTRODUCTION TO CARDIOVASCULAR SYSTEM

  2. COMPONENTS • Blood • Heart • Blood vessels

  3. GENERAL ORGANIZATION • Cells of peripheral blood, suspended in plasma, circulate through the body in the blood vascular system. • lymphatic system returns interstitial fluid from peripheral tissues returns to blood vascular system • also provides a channel for the migration of leukocytes • absorption of certain nutrients from the gut.

  4. What Does Cardiovascular System do? • Circulates blood throughout entire body for • Transport of oxygen to cells • Transport of CO2 away from cells • Transport of nutrients (glucose) to cells • Movement of immune system components (cells, antibodies) • Transport of endocrine gland secretions • redistributes and disperses heat • maintaining tissue turgidity due to pulse pressure

  5. Blood

  6. Blood • Complex mixture of cells, water, and various proteins and sugars. • Blood cells • Erythrocytes • Leucocytes • Thrombocytes • Plasma

  7. How does it do it? • Heart is main motor pump • Arteries and veins are main tubes • Arteries Away from Heart • Veins to Heart • Diffusion happens in capillaries (oxygen, CO2, glucose diffuse in or out of blood) • each loop is a closed system of tubes, so that blood per se does not usually leave the circulation.

  8. Heart

  9. Heart

  10. Layers of the Heart

  11. Chambers of the heart • Functions • Apex • Apex beat

  12. Blood vessels Arteries Veins capillaries

  13. Large arteries such as the thoracic aorta, subclavian etc are accompanied by a single vein which drains the same territory. Arteries and veins are named primarily according to their anatomical position

  14. Other arteries -usually flanked by two veins, satellite veins (venaecomitantes), which lie on either side, and have numerous cross-connections: the whole is enclosed in a single connective tissue sheath. Close association between the larger arteries and veins in the limbs allows the counterflow exchange of heat to take place

  15. Vascular tree shows modifications from centre to the periphery • The arteries increase in number by repeated bifurcation in both the systemic and the pulmonary circulation. • The arteries also decrease in diameter • The walls of arteries decrease in thickness towards the periphery • Venules which return blood from the periphery, converge on each other forming a progressively smaller number of veins of increasingly larger size. • Eventually, only the two largest veins, the superior and inferior vena cava, open into the heart from the systemic circulation.

  16. The main vessels branch into smaller vessels that collectively always have a greater cross sectional area than the parent vessels.

  17. General features of vessel walls • irrespective of size, have walls consisting of three layers (exception capillaries & venules) • Tunica intima(innermost) -endothelium, lines the entire vascular tree. • Tunica media (middle) -made of muscle tissue, elastic fibres and collagen -thickest in arteries, absent in capillaries and comparatively thin in veins. • Tunica adventitia (outer coat) consists of connective tissue, nerves and vessel capillaries. • links the vessels to the surrounding tissues

  18. (1) Tunica intima - Endothelium -Sub endothelial tissue- -Internal elastic lamina poorly defined Large artery (2)Tunica mediaThickest layer - many laminae of elastic fibres -Few smooth muscle cell & collagen fibre outer most- external elastic lamina (3)Tunica adventitia -Fibro elastic tissue -Vasavasorum +nt

  19. Large artery • Examples • Aorta, • Carotid artery • Subclavianartery

  20. Muscular artery Tunica intima - Endothelium -Sub endothelial tissue very less - internal elastic lamina well defined and wavy • Tunica media -Thick layer - many circular laminae of smooth muscle fibres - few elastic fibres & collagen fibre • Tunica adventitia -As thick as tunica media - external elastic lamina -Fibro elastic tissue (longitudinal) -Vasavasorum +nt

  21. Small artery & Arterioles Smallartery- Terminal part of muscular arteries 5-6 layer of smooth muscle Diameter of wall/lumen ratio is 1:2 Lumen more than 0.1 mm • Arterioles- • 2-4layer of smooth muscle cells layers • Internal elastic lamina absent • Lumen less than 0.1 mm • -Musculararterioles-100micron to 50 micron • -Terminalarterioles-50 to 10micron • Metarterioles

  22. Larry M. Frolich, Ph.D.,Human Anatomy Capillaries • The capillary wall is formed by an endothelium and its basal lamina, plus a few isolated pericytes • Microscopically -one cell layer thick • minimal barrier between blood and tissues • Entire goal of C-V system is to get blood into capillaries where diffusion takes place • Lumen just enough to admit passage of single blood cells, usually with considerable deformation 4-8 μm in diameter

  23. in the brain, skin, muscles, lung etc in intestinal mucosae, endocrine glands, choroid plexus etc Fenestrated capillaries occur in renal glomeruli, where they lack a diaphragm

  24. Sinusoids • are expanded capillaries • large and irregular in shape. • have true discontinuities in their walls (gaps between endothelial cells) • Sinusoids occur in large numbers in the liver (where a basal lamina is completely absent), spleen, bone marrow and suprarenal medulla

  25. Venules • Venule (postcapillaryvenule). - When two or more capillaries converge, the resulting vessel is larger (10-30 μm) • are tubes of endothelial cells surrounded by basal lamina, the larger vessels have delicate adventitia. Pericytes support the walls. • endothelium is relatively permeable • are sites of leukocyte migration • Muscular venules-acquire musculature when about 50 μm • Muscular venules converge to produce veins • Venules and veins are capacitance vessels

  26. Veins • thin wall, a large capacitance, less muscle tissue. • wall thicker in veins of the leg than in the arm. • structural plan of wall-similar to other vessels • Pressure- about 5 mmHg, decreases in larger veins, approaching zero close to the heart • Most veins have valves (semilunar)to prevent reflux of blood • may give a 'knotted' appearance to the distended veins • In the limbs, especially the legs where venous return is against gravity, valves are of great importance to venous flow towards the heart • Valves are absent in veins of the thorax and abdomen.

  27. Why are valves found in veins but not in arteries? Do all veins have valves

  28. Artery/Vein differences

  29. Subdivisions of vessels Functionally - three main classes of vessel • Conducting vessels (large arteries) • Distributing vessels (small arteries) • Resistance vessels (arteries, but mainly arterioles), • Exchange vessels (capillaries, sinusoids and small venules) Their walls allow exchange between blood and the interstitial tissue fluid which surrounds all cells • Capacitance vessels (Larger venules & veins). This part of the vascular bed contains the greatest proportion of blood high capacitance of these vessels is due to the distensibility (compliance) of their walls

  30. Structurally - Arteries can also be divided functionally into • Elastic – large arteries- eg. aorta, common carotid, subclavian etc. • Muscular – Medium sized arteries supplying individual organs, limbs etc eg. Renal, testicular, radial etc. • Arterioles – larger arterioles, terminal arterioles and meta-arterioles. Microvascular bed is formed by – • Arterioles, • Capillaries • and venules

  31. Lymphatics • lymphatic vessels provide a parallel circulatory system • Originate as blind-ended endothelial tubes which collect excess fluid from the interstitial spaces between cells and conduct it as lymph. Lymph is returned to the blood vascular system via lymphatic vessels which converge on the large veins in the root of the neck.

  32. Vascular shunts and anastomoses Communications between the arterial and venous systems without intervening capillaries • found in many regions of the body – • skin of the nose, lips and ears, nasal and alimentary mucosae, erectile tissue, tongue, thyroid gland and sympathetic ganglia.

  33. In the newborn child- few arteriovenousanastomoses, but they develop rapidly during the early years. • In old age they atrophy, sclerose and diminish in number. • Functions - regulation of temperature - regulation of regional blood flow - regulation of blood pressure

  34. Arterial anastomoses • Arteries can be joined to each other by an anastomosis -actual - potential • An end-to-end anastomosis occurs when two arteries communicate directly

  35. Anastomosis by convergenceoccurs when two arteries converge and merge • A transverse anastomosis occurs when a short arterial vessel links two large arteries transversely • End artery ?

  36. Circulation of blood Adult circulation Fetal circulation Portal circulation

  37. Fetal circulation

  38. Adult Circulation

  39. Portal circulation

  40. THANK YOU

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