4-2-07 - Varicose veins dilated swollen painful veins...

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-1Blood vessels Structure permits blood flow. Molecular exchange between blood and tissues. 3 layers: Ÿ Tunica externa: loose connective Ÿ Tunica media: smooth muscle Ÿ Tunica interna: simple squamous Ÿ Arteries Ÿ Large (elastic): elastic fibers in tunica media (changes in diameter) Ÿ Medium (muscular): less elastic fibers and more smooth muscle in tunica media (fairly constant diameter) Ÿ Ÿ Veins Ÿ Large: Thickest layers (compared to other veins) Ÿ Medium: tunica media thin Ÿ Venule: no tunica media BP in veins too low to overcome gravity: they prevent backward flow away from the heart
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Unformatted text preview: Varicose veins: dilated, swollen, painful veins. Impairing valve function, standing, inactivity. Capillaries: Continuous (complete endothelial tissue). Fenestrated (perforated endothelial lining) Blood-brain barrier: prevents all but most vital molecules from entering the brain. Hepatic portal system: Ÿ Portal = connecting two capillary beds (digestive organs, sinusoids of liver) Ÿ nutrient rich, deoxygenated blood (processing, storage)...
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