PHS 3507 Chapter Notes - Chapter 21: Colloid, Cardiac Muscle, Natriuretic Peptide
25 Oct 2017
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Document Summary
Capillaries: smallest blood vessels, responsible for material exchange between blood and interstitial fluid. Internal elastic membrane (elastic fibers in outer margin of arteries. Concentric sheets of smooth muscle in loose connective tissue. External elastic membrane separates t. media from t. externa. Scattered myosin fibers: myosin fibers have more head per filament. Dense bodies transmit contractions from cell to cell. Functions over a wide range of lengths (plasticity). Rhythmic cycles of activity controlled by pacesetter cells. Modified by neural, hormonal or chemical factors. Elasticity allows arteries to absorb pressure generated by the heart. Contractility changes the arterial diameter, controlled by sympathetic innervation. Tunica media (many elastic fibers, few muscle cells) Elasticity distributes pulse force: muscular arteries (distribution arteries) Material diffuses between blood ad interstitial fluid. Found in all tissues except for epithelia and cartilage. Permit diffusion of water, small solutes and soluble materials. Specialized continuous capillaries have very restricted permeability (e. g. blood brain barrier).
