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INTRODUCTION TO CARDIOVASCULAR SYSTEM

COMPONENTSBlood

Heart

Blood vesselsGENERAL ORGANIZATIONCells 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.What Does Cardiovascular System do?Circulates blood throughout entire body forTransport of oxygen to cellsTransport of CO2 away from cellsTransport of nutrients (glucose) to cellsMovement of immune system components (cells, antibodies)Transport of endocrine gland secretionsredistributes and disperses heatmaintaining tissue turgidity due to pulse pressureBloodBlood

Complex mixture of cells, water, and various proteins and sugars.

Blood cellsErythrocytesLeucocytesThrombocytes

Plasma

6How does it do it?Heart is main motor pumpArteries and veins are main tubesArteries Away from HeartVeins to HeartDiffusion 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.

HeartHeart

Layers of the Heart

Chambers of the heartFunctions

Apex

Apex beatBlood vessels Arteries Veins capillaries Arteries and veins are named primarily according to their anatomical position

Large arteries such as the thoracic aorta, subclavian etc are accompanied by a single vein which drains the same territory.

Other arteries -usually flanked by two veins, satellite veins (venae comitantes), 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 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.

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

Large artery(1) Tunica intima - Endothelium -Sub endothelial tissue- -Internal elastic lamina poorly defined

(2)Tunica media Thickest layer - many laminae of elastic fibres -Few smooth muscle cell & collagen fibre outer most- external elastic lamina(3)Tunica adventitia -Fibro elastic tissue -Vasa vasorum +nt Large arteryExamplesAorta,Carotid arterySubclavian artery

Muscular arteryTunica intima - Endothelium -Sub endothelial tissue very less - internal elastic laminawell defined and wavy

Tunica adventitia -As thick as tunica media - external elastic lamina -Fibro elastic tissue (longitudinal) -Vasa vasorum +ntTunica media -Thick layer - many circular laminae of smooth muscle fibres - few elastic fibres & collagen fibreSmall artery & ArteriolesSmall artery-Terminal part of muscular arteries5-6 layer of smooth muscleDiameter of wall/lumen ratio is 1:2Lumen more than 0.1 mm

Arterioles- 2-4layer of smooth muscle cells layersInternal elastic lamina absentLumen less than 0.1 mm-Muscular arterioles-100micron to 50 micron -Terminal arterioles-50 to 10micron Metarterioles Larry M. Frolich, Ph.D.,Human AnatomyCapillariesThe capillary wall is formed by an endothelium and its basal lamina, plus a few isolated pericytesMicroscopically -one cell layer thickminimal barrier between blood and tissuesEntire 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 deformation4-8 m in diameter

in intestinal mucosae, endocrine glands, choroid plexus etcin the brain, skin, muscles, lung etcFenestrated capillaries occur in renal glomeruli, where they lack a diaphragmSinusoidsare expanded capillarieslarge 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

VenulesVenule (postcapillary venule). - When two or more capillaries converge, the resulting vessel is larger (10-30 m) are tubes of endothelial cells surrounded by basal lamina, the larger vessels have delicate adventitia. Pericytes support the walls. endothelium is relatively permeableare sites of leukocyte migrationMuscular venules -acquire musculature when about 50 mMuscular venules converge to produce veins Venules and veins are capacitance vesselsVeinsthin 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 vesselsPressure- about 5 mmHg, decreases in larger veins, approaching zero close to the heartMost veins have valves (semilunar) to prevent reflux of bloodmay give a 'knotted' appearance to the distended veinsIn 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.

Why are valves found in veins but not in arteries?

Do all veins have valvesArtery/Vein differencesArteries (aa.)Veins (vv.)Direction of flowBlood Away from HeartBlood to HeartPressureHigherLowerWallsTHICKER: Tunica media thicker than tunica externaTHINNER: Tunica externa thicker than tunica mediaLumenSmallerLargerValvesNo valvesValves

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 cellsCapacitance 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

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

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.Lymphatics Vascular shunts and anastomosesCommunications between the arterial and venous systems without intervening capillariesfound 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.

In the newborn child- few arteriovenous anastomoses, 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 Arterial anastomosesArteries can be joined to each other by an anastomosis-actual- potential

An end-to-end anastomosis occurs when two arteries communicate directly

Anastomosis by convergence occurs when two arteries converge and merge

A transverse anastomosis occurs when a short arterial vessel links two large arteries transversely

End artery ?

Circulation of bloodAdult circulationFetal circulationPortal circulation

Fetal circulationAdult Circulation

Portal circulationTHANK YOU