BISC 101 Lecture Notes - Lecture 18: Hypertension, Extracellular Fluid, Lymphatic System
14 Mar 2016
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Document Summary
Open circulatory system found in arthropods, most molluscs. Hemolymph: circulatory fluid, actively pumped around body. Not confined to blood vessels, it flows into open sinuses. Directly bathes tissues and organs directly (interstitial fluid) 1 or more (tubular) hearts + incomplete blood vessels. Body movement contribute to pumping and return of blood to heart. Low pressure system = slow o2 delivery but low cost. Confined to blood vessels so separate from interstitial fluid which bathes tissues. 1 (or more) hearts pump blood in closed series of blood vessels infiltrating tissues (as capillaries) High blood pressure increases effectiveness, and regulation, of o2 delivery in larger, more active, animals- but high cost. Capillaries: small and thin walled (1 cell thick); can be fenestrated (holes) Arteries: tough, thick-walled, elastic; recoil maintains blood pressure in capillaries when heart relaxes. Veins: thinner with valves to prevent backflow during low pressure return of blood to heart; compliant for storage of blood.
