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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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Arteries
- Elastic Arteries: fxn as a pressure reservoir, LARGEST in diameter, but THIN walls
- Muscular Arteries: THICK walls, capable of large vasodilation & vasoconstriction
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Anastomoses
Union of the branches of 2 or more arteries supplying same area
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Capillaries
- Smallest blood vessels
- fxn to exchange b/w blood & interstitial fluid
- LACK tunica media & externa
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3 types of Capillaries
- Continuous: endothelial cell membrane
- Fenestrated: have pores
- Sinusoids: wider & QUICKEST AT EXCHANGE
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Portal vein
blood passes thru 2nd capillary bed
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Veins
same 3 layers as in arteries BUT NOT designed to withstand HIGH pressure (thinner walls)
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3 layers or tunics
- Tunica interna (intima)
- Tunica media
- Tunica externa
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Tunica interna
- inner lining in direct contact w/blood
- endothelium continuous with heart lining
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Tunica media
- muscular & connective tissue
- smooth muscle regulates diameter
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Tunica externa
- Elastic & Collagen fibers
- anchors vessels to surrounding tissue
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Location of largest portion of blood
in SYSTEMIC veins & venules
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Venoconstriction
the reduction of volume of blood in vein reservoirs to allow more blood to flow where needed
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Capillary EXCHANGE
- 3 methods of movement b/w blood & interstitial fluid
- 1. Diffusion: substances move down the conc. gradient to body cells
- 2. Transcytosis: pinocytosis (imp for lipid insoluble molecules as its the only way for them to cross)
- 3. Bulk flow: passive process, salt & ions move together
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blood brain barrier
tight junctions which LIMIT diffusion
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Sterling's Law
as much is reabsorbed as is filtered
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Cardiac OUtput
CO = Heart RATE (HR) X Stroke Volume (SV)
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Blood Pressure
how much blood is leaving the heart
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Vascular Resistance
- Opposition of blood flow due to FRICTION b/w blood & walls of vessels
- Depends on
- size of lumen
- blood viscosity
- vessel length
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If high blood viscosity
- This means HIGH resistance which can result in closing of blood flow
- this leads to stroke & hemorrhaging
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Skeletal muscle pump
- 2 mechanisms
- 1. skeletal muscle pump - pumps in 1 direction due to valves
- 2. respitory pump: due to presure change in thoracic & abdominal
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Velocity of blood
SLOWEST in capillaries
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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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Cardiovascular Center (CV)
- in medulla oblongata
- regulates heart rate (HR) & stroke volume (SV)
- Neurons REGULATE heart RATE (not rhythm, which is done by SA an AV node)
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3 types of Sensory Receptors
- Proprioceptors: monitor joint and muscle movement during physical activity
- Baroreceptors: monitor PRESSURE changes & stretch blood vessels
- Chemoreceptors: monitor concentration of chem in blood
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Hormonal Regulation OF BP
- Renin system: released when blood vol or flow DECREASES. RAISES BP by vasoconstriction & bringing ALDOSTERONE
- Epi & NorEpi: Released to INCREASE cardiac output by increasing rate & force of CONTRACTIONS
- ADH(Antidiuretic hormone): INCREASES BP
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