Blood Vessels

Blood Vessels

Humaira NazirNES Instructor

ARTERIESCharacteristics Very Thick, Muscular Walls Very High Blood PressureCarries Oxygenated Blood (With 1 Exception)Examples Coronary, Aorta, Carotid, FemoralFunction Carry Blood away from the heart

VEINSCharacteristicsThinner wall with less muscleLarge-diameter lumens, which offer little resistance to flowHave Valves (WHY ?)Blood pressure is much lower than in arteriesCarries Deoxygenated Blood (1 Exception)Examples Vena Cava, Jugular, Function After blood moves through the arteries it enters larger blood vessels called veins, which carry blood back to the heart.VeinSmallest veins called venulesDiameters from 8 100 m Venules join to form veins

VEINS VS. ARTERIES

CAPILLARIESCharacteristics:Very smallWalls are only one cell thickDiffusion takes placeMost abundantFound near muscle cells, organs, etc.

FunctionWhere material (oxygen, nutrients, carbon dioxide) is exchanged between blood and cells.Normal Capillary

CAPILLARIES

Functions Of Blood VesselsArteries - Carry blood away from heart. Arterioles - Small arteries that deliver blood to capillaries.Capillaries Thin walled vessels allow for exchange between blood and tissue cells. Venules - Collect and drain blood into veins.Veins - Return blood to heart.

Structure Of Blood Vessels(Artery & Vein)Composed of three layers

1. Tunica Intima = Is the inner layer of arteries and veins, composed of simple squamous epithelium

2. Tunica media = Is the middle layer of the walls of arteries and veins. It is composed of smooth muscle and elastic fibers. -Contraction vasoconstriction-Relaxation vasodilatation

3.Tunica Externa = Is the strong outer covering of arteries and veins. It is composed of connective tissue as well as collagen and elastic fibres. These fibres allow the arteries and veins to stretch and prevent overexpansion due to the pressure that is exerted on the walls by blood flow.

Normal Coronary Artery

Medium size Vein

Vein valve

Structural DifferencesArteries VeinsThick muscular wall Small lumenMore elastic and collagen fibersValves in pulmonary artery and Aorta onlyBlood moves in pulsesBlood flows rapidly

Thin muscular wallLarge lumen little elastic tissue

Valves throughout all veins

No pulsesBlood flow slowly

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