2.1.3

antriovenous anastomoses (shunt)

blood flows from artery to vein, shunts located in extremities (fingers, palms, toes, ears), most vulnerable to heat loss, shuns allow warm blood to bypass these surfaces, shunt reduces heat loss during cold exposure

transcytosis in capillary exchange

endothelial cells, endocytosis/pinocytosis -> transport -> exocytosis, important for movement of fatty acids, albumin, and some hormones ex. insulin, move from either blood to tissue fluid or vice versa

most common circulatory route

heart -> arteries -> arterioles -> capillaries -> venules -> veins -> heart

circumstances which affect capillary exchange

kidneys have high BP capillary networks (glomeruli, mostly filtration), lungs have low BP capillary networks (mostly resorption), most precapillary sphincters are closed at rest resulting in little to not filtration, capillary flow increases in metabolically active tissue therefore filtration predominates along length of capillary

heart attack (myocardial infarction)

long-term obstruction of coronary circulation causes death of cardiac cells in affected area, obstruction is often a fat deposit or blood clot, decrease in blood supply to a particular heart tissue for a long time

3 routes of chemical passage in capillary exchange

through endothelial cell plasma membrane via diffusion of transcytosis, through intercellular clefts via diffusion, through fenestrations or filtration pores via diffusion

arterial anastomoses

two arteries merge, alternate blood supply routes, found in coronary circulation and around joints, blockages here are more damaging than the blockage of a vein

capillary exchange

two-way movement of fluid is the basis of capillary exchange, involves a lot of water moving in and out of the blood, only occurs across capillary walls between blood and surrounding tissues, leaving circulation (electrolytes, o2, amino acids, lipids, organic nutrients, antibodies, hormones), entering circulation (co2, ammonia, metabolic wastes)

portal system

blood flows through two consecutive capillary networks before returning to the heart, important in connecting hypothalamus to anterior pituitary, exist in kidneys (how they reasorb and filter etc), between intestines and liver (cap bed in intestine leads to a cap bed in liver)

coronary circulation

blood vessels of the heart wall are coronary circulation, blood flowing through heart chambers is not available for heart tissue, coronary vessels deliver blood directly to heart tissue for exchange (disproportionate amount of blood)

solvent drag

chemicals dissolved in water are dragged along with water by bulk flow

colloid osmotic pressure (COP)

draws fluid into capillary by osmosis, oncotic pressure is net COP (same at both ends), more concentrated in blood than tissue fluid, proteins in plasma want to move out of capillary but cannot move out of blood therefore water moves in

diffusion in capillary exchange

most important mechanism of exchange, hydrophobic substances easily pass through membrane (lipids, co2, o2), hydrophillic substances must pass through channels, fenestrations, or intercellular clefts (glucose, electrolytes), proteins (RBC, WBC, platelets) are held back

venous anastomoses

one vein empties into another, alternate drainage of organs, more of these than arterial, most common

filtration and resorption in capillary exchange

opposing HP and OP, shift in fluid due to change in the difference between HP and OP, pressure change of capillary BP from arterial to venous end causes shift from filtration to reabsorption, capillaries resorb ~85% of fluid

angina pectoris

partial obstruction of coronary blood flow can cause chest pain, reversible ischemia (temp lack of blood flow to cardiac muscle)

anastomoses

point where 2 blood vessels meet

hydrostatic pressure

pressure due to compressed fluid including the pressure of water on itself, HP pushes out of blood and into tissue fluid, 2 kinds (BP, interstitial fluid - practically zero, stays static through capillary)

osmotic pressure

pressure due to diffusion of water from a concentration of low non-penetrating solutes to a concentration of high non-penetrating solutes, OP pushes into blood