Title Unit 8_Transport in Mammals_UPDATED_ PDF 2023.pdf ✅

30/01/2023, 08:27 Unit 8_Transport in Mammals_UPDATED_2023.docx - Google Docs https://docs.google.com/document/d/1AmR0Q72TGx50SJ2BFdgWofIesH3JkStZ/edit 1/279 ASL Biology_9700 Unit 8: Transport in Mammals Mohammad Hussham Arshad, MD Transport in Mammals With Mohammad Hussham Arshad, MD Syllabus – For June 2022
30/01/2023, 08:27 Unit 8_Transport in Mammals_UPDATED_2023.docx - Google Docs https://docs.google.com/document/d/1AmR0Q72TGx50SJ2BFdgWofIesH3JkStZ/edit 2/279 ASL Biology_9700 Unit 8: Transport in Mammals Mohammad Hussham Arshad, MD
30/01/2023, 08:27 Unit 8_Transport in Mammals_UPDATED_2023.docx - Google Docs https://docs.google.com/document/d/1AmR0Q72TGx50SJ2BFdgWofIesH3JkStZ/edit 3/279 ASL Biology_9700 Unit 8: Transport in Mammals Mohammad Hussham Arshad, MD
30/01/2023, 08:27 Unit 8_Transport in Mammals_UPDATED_2023.docx - Google Docs https://docs.google.com/document/d/1AmR0Q72TGx50SJ2BFdgWofIesH3JkStZ/edit 4/279 ASL Biology_9700 Unit 8: Transport in Mammals Mohammad Hussham Arshad, MD Arteries, Capillaries and Veins STRUCTURE: The walls of arteries and veins have three layers or tunics: • An outer fibrous layer (tunica adventitia or externa) of connective tissue containing collagen fibres. • A middle layer (tunica media) of circularly arranged smooth muscle and elastic fibres. • An inner layer (tunica intima), consisting of a specialized simple squamous epithelium, often called the endothelium, that lines all blood vessels. The basement membrane, a subendothelial layer composed of connective tissue, supports the endothelium. Structure Function Arteries- have thick muscular walls, the elastin in the wall allows them to stretch and recoil. Smooth muscle and collagen fibres add strength to the wall. Transports blood away from the heart; Have to be thick to cope with the high pressure with which the blood is pumped into it; Carries oxygenated blood except pulmonary artery. Capillaries- are tiny and they build up a network of small vessels in almost every organ of our body. Their walls are thin, only 1-cell thick allowing exchange between the capillary and surrounding tissues. Supply tissues with nutrients; Removes waste from surrounding cells; Exchanges oxygen, carbon dioxide, water and salts between blood and surrounding tissues. Veins- have thin walls, consists of three layers that are thinner and less elastic when compared with arteries. Contain valves to prevent backflow of blood. Transports blood towards the heart; Carries deoxygenated blood except pulmonary vein; Blood pressure is low as it is reduced by the bloods long journey from the heart.