IPHY Exam: March 15, 7:45 am Duane G1B30. Exchange of materials in capillaries Diffusion Bulk Flow Diffusion: When the blood reaches the capillaries, many nutrients, O2, and metabolic end products diffuse out/in (down concentration gradients) between the blood and cells. Cellular utilization or production of materials causes diffusion gradient to exist between blood and cells. Bulk Flow Plasma (minus most plasma proteins) is moved by bulk flow out of the capillaries, moving all water soluble materials to the cells, and then most of the water is restored back to the circulation, carrying wastes. Fig , p. 367 Forces: Capillary blood pressure (outward) Plasma colloid osmotic pressure (inward) beginning end BP = 37BP = 17COP = = 12 out = 8 in Lymph circulation picks up the rest unabsorbed water containing wastes, ions, etc from extracellular fluid space loose plasma proteins loose red blood cells cell debris pathogens cancer cells Lymph flow caused by: 1. Skeletal muscle contraction 2. Smooth muscle contraction in walls of lymph vessels 3. SNS stimulation to walls of lymph vessels Excretory System Roles: remove wastes balance body water content balance body ionic content balance acid-base balance Kidney also regulates RBC s and secretes renin as part of regulation of blood pressure Kidney: by regulating blood water, ionic and H+ content, can regulate extracellular fluid and cell water, ionic and H+ content Extracellular fluid blood Water, ions and H+ If blood water drops, increase blood ion content, and withdraw water from extracellular tissues, and then water would leave cell Plus, 1. adrenal gland (aldosterone) 2. hypothalamus and posterior lobe of the pituitary (vasopressin) 3. Heart atrium (atrial natriuretic factor) Fig. 14-3, p. 504 Glomerular filtration 55- ( ) = 10 mm Hg blood Bowman s Capsule 15 BP = 55 COP = 30 How glomerular filtration can be varied: Increased blood pressure 65- ( ) = 20 mm Hg blood Bowman s Capsule 15 BP = 65 COP = 30 How glomerular filtration can be varied: Dehydration 55- ( ) = 10 mm Hg blood Bowman s Capsule 15 BP = 55 COP = 35 Materials filtered into Bowman s capsule Water Ions glucose, amino acids wastes (NH3, urea, etc) a few plasma proteins everything else in plasma hopefully no cells