urinary system Flashcards
what are the functions of the kindeys?
-excretion of waste
-H2O balance (plasma volume)
-BP control (renin)
-acid-base balance
-blood cell production (erythropoietin)
-vitamin D action
where is the renal cortex vs medulla in relation to the kidneys?
cortex= outer
medulla= inner
what does the urinary system consist of?
-kidneys
-blood supply
-transport vessels (bladder, ureter, urethra)
what are the 2 types of nephrons?
a) corticol; shorter and 85%
b) juxtamedullary; longer and 15% osmotic gradient
what makes up the vascular component of the nephrons?
-renal artery
-afferent and efferent arteriole
-peritubular capillaries
-renal vein
-glomerulus
what are the parts of a nephron tubule?
bowmans capsule–> proximal tubule –> loop of Henle (ascending then descending limb) –> distal tubule –> collecting duct
what are the three basic renal processes?
-glomerular filtration (fluid to tubule)
-tubular reabsorption (tubule to blood)
-tubular secretion (blood to tubule)
**urine is a result of these 3 processes)
where does filtration, reabsorption, and secretion occur?
-filtration = Bowman’s capsule
-reabsorption/secretion = proximal/distal tubule and collecting ducts
-reabsorption also occurs in the loop of Henle through the osmotic gradient
what substances cannot be filtered by the glomerulus?
-RBC
-Proteins
-they are too big
what is the glomerulus and its 3 layers?
-tuft of capillaries that is fenestrated to make it more permeable; it is surrounded by the Bowman’s capsule
a) glomerular capillary wall
b) basement membrane
c) inner layer of Bowman’s capsule (podocytes around glomerulus tuft)
how much does the glomerulus filter?
-~160-180 L/day (~125 mL/min)
-moves electrolytes, water, and glucose into tubules
what are podocytes?
-can change shape to control filtration
-renal failure=large slits in podocytes that is allowing proteins and RBC’s in
what are the forces opposing glomerular filtration?
-plasma colloid osmotic pressure
-bowman’s capsule hydrostatic pressure
what are the forces favoring glomerular filtration?
-glomerular blood pressure
what does GFR depend on?
-glomerular filtration rate depends on net filtration pressure, the glomerular surface is for penetration, and the permeability of the glomerular membrane
-GFR will change if hydrostatic pressures change
how do arterioles control GFR?
-afferent arterioles constricting or efferent dilates= LOWER BFR
-afferent arterioles dilating or efferent constricts = HIGHER GFR
how does blood pressure affect GFR?
-a lower BP means lowered GFR and decreased retention of fluids
how can GFR be measured
-inulin can be used as it is not reabsorbed or secreted
-excretion=filtration
difference between trans-cellular and paracellular transport?
-trans-cellular can be active or passive
-paracellular is only passive as is the diffusion of water and ions
how does Na+ reabsorption work?
-an active process
-sodium-potassium ATPase pump in the basolateral membrane is essential for Na+ reabsorption (the pump creates Na+ gradients across membranes that facilitate the reabsorption)
-it also affects the reabsorption of other substances
what other substances also follow the reabsorption of Na+?
-water ; via the osmotic gradient created
-Cl- ; via the electrical gradient
-glucose ; by carriers
where does glucose reabsorption occur?
-occurs in the proximal tubule
-is sodium linked