BIOL 2420 Lecture Notes - Lecture 6: Osmotic Pressure, Endothelium, Transcytosis
15 Nov 2016
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Document Summary
Smallest, thinnest, most numerous vessels in the body: 5-10 m in diameter. Only one blood cell can pass at a time. Hold about 5% of total circulating blood volume at rest. Large surface area for exchange - about 6000m2: composed of a single layer of endothelial cells. Formed from collagen/glycoprotein mix: highly permeable to small, hydrophobic molecules. Two classes of capillaries: continuous capillaries. Sites of exchange for small, water soluble substances. Goes through the cell - endocytosis and exocytosis pairing. Located in the kidney, intestines, bone marrow, and liver. Bone marrow - site of blood cell production - need big gaps to allow those to pass. Bone marrow and liver have discontinuous capillaries. Movement of material across capillary walls is important for: Rapid diffusion of small solutes across capillary walls. Movement down partial pressure, electrochemical and concentration gradients. Some proteins are selectively transcytosed across endothelial cells. Transcytosis is a slow, energy requiring process.
