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Lecture 9 - Biology 2A03 L9 Lecture 9 Circulation III...

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Biology 2A03 – L9 Lecture 9 – Circulation III Vascular System Inner radius Arteries 12mm 1. Low resistance 2. little pressure drop (little press drop from the pressure of heart) 3. can store some of the pressure generated by heart 4. acts a pressure reservoir Arterioles 15 um 1. Major site of resistance 2. controls blood flow patterns 3. helps regulate arterial blood pressure Capillaries 10 um 1. thin layer of endothelial cells 2. Exchange site of nutrients and metabolic biproducts with tissues Venuoles 10 um 1. Exchange (some) with tissues Veins 5 mm 1. Low resistance, thin walled, Distensible 2. adjusts blood return to heart 3. acts as a blood reserve (60% of blood volume) 1. All parts of the circulatory system have endothelium (inner layer) , all but capillaries have smooth muscle and connective (with varying degrees of elastin and collagen fibres) tissue (outer layer) 2. Capillaries situated very close to cells 1. making diffusion sufficient btw capillaries tissues 1. microtubules – arterioles, capillaries, venuoles 2. arteries have a lot of smooth muscle
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Biology 2A03 – L9 3. many arterioles branch off from one artery 4. thousands of capillary branch off arterioles, precapillary sphincters 5. veins – much less smooth muscle and have valves (which arteries do not have); valves allow unidirectional movement of blood Arteries 1. muscular, highly elastic – high elastin/collagen ratio in connective tissue 2. Compliance : ∆V moderate compliance to smooth out pressure fluxation from heart
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