Blood Vessel Structure and Function PDF

Blood vessel structure and function Jo Sharp  Identify the layers of a blood vessel ① Learning Describe the structure and ② function of blood vessels objectives Discuss the facto...

Blood vessel structure and function Jo Sharp  Identify the layers of a blood vessel ① Learning Describe the structure and ② function of blood vessels objectives Discuss the factors that influence venous return  Blood vessels Iz Function of blood is transport, protection and 3 homeostasis Regulations Blood vessels essential to achieve this Closed system of tubes – blood away from the heart to the organs and returned back to the heart Pulmonary circulation – blood to the lungs Systemic circulation – blood to the rest of the body Blood vessels ① Artery ① ② ③ ⑤ ① Arterioles ⑪ ⑳ Capillaries ⑪ Venules ⑮ Veins  = Layers of 3 layers Tunica6 intima (interna): innermost layer called endothelium, thin flattened cells,[a basement - => membrane and internal elastic lamina, smooth to a blood # reduce friction, secrete locally acting chemical mediators ① t Tunica① media (middle): muscle and connective tissue Easte vessel · (elastin), accounts for the variation of the different 6vessels. Muscle arranged circularly to regulate the diameter of the blood vessel, controlled by SNS. External elastic lamina separates middle from out later ⑧ ② wall externa (adventitia): elastic and collagenJ Tunica So ①nerves and in larger vessels blood vessels (vasa fibres, vasorum), anchors the vessel to the surrounding tissue j -  Innermost layer smooth to reduce friction Muscle connective tissue Cross section Separates middle from outer layer of a typical blood vessel Structure and function of blood vessels Vessel Features Structure Function Arteries - Carry blood away from the heart under high pressure Tunica intima. Q Distribute blood to the major organs ② Elastic fibres enable vessels to stretch Usually contain oxygenated blood (except pulmonary artery) & Tunica media – large amount of -- Q smooth muscle and elastic fibres 15% blood volume ⑬ Muscular arteries can adjust blood flow Tunica externa thick and contains Elastic arteries: largest arteries i.e. aorta. Large diameter, walls Q ⑰ ⑤ fibroblasts, collagen and elastic fibres relatively thin arranged- longitudinally Muscular arteries: Tunica media smooth muscle and less elastin. A range of sizes, i.e femoral 0.5mm in diameter, continue to branch as distributing arteries i.e. brachial artery Anastamosis: union of branches of 2 or more arteries – alternative route for blood * Arterioles Deliver blood to the capillaries Tunica intima ① - Regulate blood flow to tissues and affect blood - - pressure - Approximately 400 million arterioles, range in size from 15um to Tunica media – smooth muscle and 300um. elastic fibres ⑫ Pre-capillary sphincter regulates the resistance 6 Terminal end of the arteriole, distal most muscle cell forms the O to blood flow pre-capillary sphincter Structure and function of blood vessels Vessel Features Structure Function Ga · Capillaries Microcirculation from capillaries to venules. Tunica intima but no tunica media or externa - Permit exchange of nutrients and waste between 37 blood and tissues 20 billion capillaries so a large surface area Fenestrated capillaries found in kidneys, small intestine, ② Cpores to allow larger ventricles of brain. They have small 5% of blood volume * molecules to pass through. Smallest blood vessel – diameter 5-10um ③ Sinusoids are found in the liver. They have large pores to Capillaries found near every cell in the body allow proteins to pass through. Sinusoids * Venules Collects blood from capillaries to veins Tunica intima Exchange of nutrients and waste Thin walls Tunica media little smooth muscle 10-50um in diameter Veins Returns blood- to the heart under - low pressure Tunica intima thinner that that in arteries Blood reservoir Sl sig Thin walls, Tunica media thin Valves – prevent back flow Size 0.5mm for small veins to 3cm in diameter for larger veins Tunica externa thickest layer containing collagen and elastic i.e. vena cava fibres Distensible Valves – thinO fold of tunica intima  Q Veins – low pressure system – needs assistance to return blood to the heart ② Skeletal muscle pump – walking – skeletal Venous ③ muscle contraction assists with pumping blood back to the heart – valves prevent back flow Respiratory muscle pump – alternating return compression and decompression of the veins. When breathing the diaphragm moves down, this reduces the pressure in the thorax which increases the pressure in the abdominal cavity, 25 compressing the veins, blood moved towards the heart  Looked at the 3 layers of a blood vessel Looked at different vessels linking structure and function Overview Venous return Useful table – 21.1 Distinguishing features of blood vessels (Chapter 21 inTortora’s Principles of Anatomy and Physiology)