BILD 2, Professor Mel, Winter 2005 TA: Roman Fajardo ( firstname.lastname@example.org ) NOTE: To avoid possible confusion, this handout ONLY covers up to the material for midterm #1. The rest of the material from week 3 will be included in next week’s handout. Chapter 49: Circulatory Systems (pages 877-878, 882-884) Materials are exchanged in capillary beds by filtration, osmosis, and diffusion • In the process called filtration, water, ions, and small molecules leak out through fenestrations (tiny holes) in the capillaries o Large molecules (i.e. proteins) cannot fit through the fenestrations, so they stay in the capillaries o Large molecules create an osmotic potential, so water flows back into the capillaries • Blood pressure and osmotic potential balance to keep fluid constant in the capillaries (Fig. 49.12) o Blood pressure steadily decreases from artery to vein o Osmotic pressure increases as fluid leaves the capillaries Eventually, osmotic pressure is large enough to bring fluid back in
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