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types of vessels and fxn
- 1. arteries: carry blood away from the heart
- 2. arterioles: very abundant, become metarterioles prior to cap
- 3. capillaries: site of exchange
- 4. venues: thinner walls than arterioles
- 5. veins: carry blood TO the heart
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3 layers or tunics
- Tunica interna (intima)
- Tunica media
- Tunica externa
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Muscular Arteries
- Tunica media has MORE smooth muscle & fewer elastic fibers
- THICK walls
- capable of large vasodilation & vasoconstriction
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Capillaries
- Smallest blood vessels
- fxn to exchange b/w blood & interstitial fluid
- LACK tunica media & externa: substances pass thru 1 layer of epithelial cells & basement membrane
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Veins
- Not as distinct structural changes as arteries
- same 3 layers as in arteries BUT NOT designed to withstand HIGH pressure (thinner walls)
- Valves: fold on tunica interna to form cusp & PREVENT backflow
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Capillary EXCHANGE
- 3 methods of movement b/w blood & interstitial fluid & body cells
- 1. Diffusion: O2 move down the conc. gradient to body cells, CO2 goes vice versa. Can cross capillary walls thru Intracellular clefts or thru epithelial cells
- 2. Transcytosis: small quantities. Important for lipid insoluble molecules as its the only way for them to cross
- 3. Bulk flow: passive process, salt & ions move together, involved in reabsorption from interstate to cap. Important for regulation of volumes of blood & interstit fluid
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CIRCULATION time
Takes 1 min @ REST for 1 drop of blood to flow from RA back to the RA
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blood brain barrier
tight junctions which LIMIT diffusion
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Circulation
- Important diff b/w pulmonary & systemic circulation in autoreg response
- Systemic blood vessels dilate in response to LOW O2 levels (ACTING to INCREASE O2 delivery)
- Walls of PULMONARY blood vessels CONSTRICT when LOW O2 to ENSURE most blood flows to more ventilated areas of LUNGS
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