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Nephron (Reabsorption (3 mechanisms for re-absorption (Active Transport…
Nephron
Reabsorption
3 mechanisms for re-absorption
Diffusion
movement of solutes across membrane from high concentration to low
Active Transport
aid in transporting ions across membranes with pumps
some pumps require use of ATP
Osmosis
water moves towards higher concentration of solutes
water moves because solutes cannot diffuse across membrane
most re-absorption occurs in proximal convoluted tubule
most nutrients re-absorbed, sugar re-absorbed transcellularly
most proteins absorbed via pinocytosis & cell-mediated endocytosis
Na absorbed in PCT
via active transport with Na/K pumps & Na pumps with help of ATP
regulated by Aldosterone and ANP in DCT
Excretion
parasympathetic innervation of bladder
stimulates micturition
sympathetic innervation of bladder
inhibits micturition
storage reflex
urine excreted via ureters into bladder then urethra
micturition reflex
Filtration
occurs in glomerular capsule
three forces coincide with filtration
Blood Colloid Osmotic Pressure OPg
pressure pushing back against HPg
osmotic pressure done by solutes
draws water back into glomerulus
Capsular Hydrostatic Presssure HPc
pushes against HPg
tries to prevent more fluid movement
pressure already present in capsule because of filtrate
Glomerular Hydrostatic Pressure HPg
normal BP carried throughout body
pushes water & small enough solutes into capsule
blood being filtered enters capsule via afferent arterioles and leaving via efferent arterioles
solutes small enough to pass through fenestrated membranes
proteins and erythrocytes will not filter
filtrate must go through specialized 3 layer membrane
endothelium innermost fenestrated layer
porous middle layer
visceral layer composed of podocytes
Secretion