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
what is the tubular maximum vs the renal threshold?
-tubular maximum=point where all glucose carriers are full; excess stays in tubules
-renal threshold=blood glucose levels are high so glucose is seen in the urine (ie. diabetes mellitus)
how is urea reabsorbed?
-urea is small and diffusable
-passive process; trying to reach equilibrium
-50% absorbed
what are the 6 substances reabsorbed and by which method?
-sodium; pump
-Cl-; electrical gradient
-glucose; carrier-mediated
-urea; passive
-K+; secreted and reabsorbed
-water; osmotic gradient
what are the effects of aldosterone?
-controls the Na+/K+ATPasepump
-released if blood volume is low
-high levels of aldosterone = increased speed of pump and increase water and sodium reabsorption
(state of dehydration, decreased urine)
what is ANP?
-Atrial Natriuretic Peptide
-it works antagonistically to aldosterone and inhibits Na+ reabsorption
-secreted by atria with increased BP, Na+, and volume (stretch of atria)
what are 3 substances secreted and into where?
-active process
-molecules from extracellular fluid into tubule
-K+ (for pump, later reabsorbed)
-H+ (acid base balance)
-Large organics
what is the function of the collecting ducts?
-they are the site of water reabsorption
-it is controlled by ADH and used to concentrate the urine
-an osmotic gradient is needed (loop of Henle)
how is a concentrated zone created in the medulla?
-a zone of high solute concentration is created in the renal medulla by the selective reabsorption of salt and urea
what is the counter-current mechanism?
the descending loop of henle is permeable to water and imperable to salt
the ascending loop of henles is imperable to water and permeable to salt
-they work opposingly so the filtrate becomes concentrated at first then less concentrated
what is the vasa recta?
-vessel following the loop of Henle
-similar osmotic gradient in blood supply
how is water reabsorbed?
ADH causes the insertion of water pores into the apical membrane
how does ADH affect water reabsorption?
-anti-diuretic hormone
-controls the permeability of collecting duct and is released if blood osmolarity is too high
high vs. low ADH
-high= collecting duct is permeable to water, urine is concentrated and smaller volume; high blood osmolarity
-low= collecting duct is impermeable to water, urine is diluted and larger volumes
what occurs in dehydration?
-high ADH
-high aldosterone
-low ANP
-inc. water reabsorption; decreased (concentrated) urine
what occurs in water loading?
-decreased ADH
-decreased aldosterone
-increased ANP
-decreased water absorption; more volume and diluted urine
what is absorbed and secreted in the proximal tubule?
absorbed= Na, Cl, water, glucose, amino acids, urea, phosphate, electrolytes
secreted= H, organic ions
-K is BOTH secreted and reabsorbed
what is absorbed/reabsorbed in the distal tubule and what is it controlled by?
-Na/water reabsorption=controlled by aldosterone and ANP
-K secretion/reabsoprtion= controlled by aldosterone
-H secretion= controlled by acid-base balance
what is reabsorbed/secreted in the collecting ducts?
-water reabsorption (ADH control)
-H secretion
-urea reabsorption (related to loop of Henle)
what is renal clearance?
-the rate at which a solute disappears from the body
-it is a non-invasive way to measure GFR (inulin and creatinine)
what should glucose and inlunin clearance be?
-inulin clearance = GFR
-glucose clearance should be 0; because of 100% absorption
what is micturition?
-urination reflex
-autonomic control of sphincter and detrusor muscle
-CNS can over-ride or initiate
what are kidney stone?
-the crystallization of minerals is either the kidney, ureters, or bladder
-calcium, oxalates (spinach/beets), dehydration
what is a normal pH balance? what can an abnormal pH effect?
normal pH is 7.38-7.42
-abnormal pH can alter tertiary structures of proteins, and affect nervous system
what is acidosis vs alkalosis?
-acidosis= neurons become less excitable and CNS becomes depressed
-alkalosis= neurons are hyperexcitable
-pH disturbances occur with K+ disturbances
what are the 3 mechanisms by which pH homeostasis is maintained?
-buffers (combines with or releases H+)
-ventilation
-renal regulation (slowest; directly excreting or reabsorbing H+)
what are buffers?
-fastest response (occurs within seconds)
-it combines with H+ so it doesn’t affect pH
-phosphate
-protein (hemoglobin)
-bicarbonate
how is pH adjusted respiratorally?
pH is adjusted by changing the rate and depth of breathing
-response within minutes
how can respiration be corrected?
reflex pathway for respiratory compensation of metabolic acidosis
-increased breathing
what is renal compensation?
this is the slowest response (within hours)
-can retain or eliminate H+ or HCO3-
what is the body correction for acidosis?
-raise the body’s pH
-buffers bind to H+ and increase breathing
-CO2 and H+ increases (via carbonic acid)
-kidneys excrete H+ and keep bicarbonate
when do type A and B intercalated cells function?
Type A functions in acidosis (secrete H+, reabsorb bicarbonate)
Type B functions in alkalosis (secretes bicarbonate and reabsorbs H+)
what is the body’s correction for alkalosis?
to lower pH
-buffers release H+ and breathing slows down to retain CO2 and H+
-kidneys retain H+ and secretes bicarbonate
what is acute vs chronic renal failure?
acute = infection, toxic agents, inappropriate immune responses, obstruction of urine flow, insufficient renal blood supply
chronic = hypertension, diabetes, chronic exposure to toxins/drugs
what are the possible causes of renal failure?
-build-up of wastes to toxic levels (vomiting, diarrhea, cellular necrosis)
-osteoporosis (loss of calcium)
-edema (loss of proteins)
-anemia (loss of RBC’s)
-Na+ and K+ imbalance (will affect nerve and muscles)
-decreased BP (low BP; dizziness)
