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84 Cards in this Set
- Front
- Back
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What organs comprise the urinary system?
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- Kidneys
- ureters - urinary bladder - urethra |
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Identify the functions of the urinary system.
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- produce urine
- dispose of metabolic wastes - maintenance of proper electrolye conc. and acid-base balance in the blood/body fluids - produce/secrete renen (role in regulating aldosterone secretion, BP) - produce/secrete - erythropoietin - stimulates rbc production - metabolize vit D to its active form -- all of these are done by the kidney |
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Describe the location and external anatomy of a kidney.
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- T12-L4; right one is higher
- deep vertical fissure called hillum; ureters blood vessels, lymphatics and nerves enter at hilus - renal sinus = cavity inside where calix and renal pelvis are located - retroperitoneal organs |
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Identify and describe the 3 layers of tissue that surround the kidney.
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- renal capsule - deep; smooth fibrous layer; continuous w/outer layer of urital wall; protection; helps kidney keep its shape
- adipose capsule - hole it in place; cushoning - renal fascia - thin layer of dense irregular CT; holds adrenal gland in position against kidney |
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What is the primary neural innervation of the kidney? How does the nervous system help regulate renal function?
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- innervated by sympathetic nerve fivers and gnaglia; nerves form renal plexus; fibers follow branches of vascular system to individual nephrons
- vasomotor innervation aimed at regulating blood flow through kidney by adjusting arteriole diameters - most PNS in abdominopelvic cavity - vagus nerve |
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What are the two main parts of a nephron?
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- the renal corpuscle: made up of glomerulus and bowman's capsule
- the renal tubule and ducts: made up of 3 parts - the PCT, the LOH and the DCT |
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Name the vessels that carry blood into and out of a glomerulus.
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- afferent arteriole
- efferent arteriole (has low pressure that's good for reabsorption); vaso constrict and dilate so we can perform filtration |
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Describe the structure of the renal corpuscle.
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- Glomerulus - specialized cap bed b/w afferent and efferent arterioles
- Bowman's Capsule/glomerular capsule - double layered wall that forms a cup around glomerulus: 2 layers (parietal/outer is simple squamous ET; the visceral is the same, but modified into podocytes - they have cellular extensions that wrap around/adhere to the endothelial cells of the glomerular capillaries); space b/w the two is capsular space, filled w/ the filtered fluid |
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Identify the regions of the renal tubule and describe the basic histological characteristics of each.
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- PCT - cells are simple cuboidal ET, prominent brush border w/microvilli on luminal surface to increase surface area for reabsorption; cells have lots of mitochondria for ATP to fuel reabsorption pumps
- LOH - descending and ascending limbs; each has a thick segment and a thin segment; refers to diameter of wall not lumen (thin = squamous ET, thick = cuboidal or low columnar ET); descends into medulla DCT - most cells are cuboidal ET, few microfilli, some mitochondria; empties into collecting duct; 2 types of cells (principle - most numerous and have ADH and aldosterone receptors; intercalated - can secrete free H+ ions to remove excess ions from the body) very similar to collecting duct histologically |
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Trace the tubular system of a nephron from Bowman's capsule to the renal pelvis.
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- bowman's capsule
- PCT - LOH - DCT - collecting duct - papillary duct - minor calyx - major calyx - renal pelvis - ureter - urinary bladder |
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Trace the circulatory pathway of a kidney from the renal artery to the renal vein.
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- renal artery - segmental arteries - lobar arteries - interlobar arteries - arcuate arteries - interlobular arteries - afferent arteriole - glomerulus - efferent arteriole - peritubular capillaries - vasa recta - interlobular, arcuate, interlobar, renal veins, inferior vena cava
- |
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Describe the location and function of the peritubular capillaries and the vasa recta.
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- peritubular capillaries surround tubular portions of nephron in cortex; allow for reabsorption of substances
- vasa recta - surrounds loops of henle of juxtamedullary nephrons in medulla |
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Based on location and structure, what are the two types of nephrons?
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- cortical nephrons (85%) - corpuscle in outer part of cortex, LOH only dips short way into medulla; almost no thin portion in ascending LOH; surrounded by peritubular dap, delivers O2, picks up COx
- Juxtamedullary nephrons - renal corpuscle close the medulla; very long LOH; deep into medulla; LOH has longer thin segments; vasa recta exists here, can concentrate urine |
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Which type of nephron is most numerous? which type plays the most important role in regulating urine concentration? Which type performs most of the reabsorptive and secretory functions of the kidney?
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- cortical nephrons (85%)
- juxtamedullary nephrons - cortical nephrons |
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Describe the location and general function of the juxtaglomerular apparatus (JGA).
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- found where DCT lies against afferent arteriole of its own nephron
- wall of tubule and affferent arteriole are modified @ point of contact: wall of afferent art. has modified smooth muscle cells called juxtaglomerular cells that function as mechanoreceptors; they have large #s of renen-containing granules in their cytoplasm - cells of renal tubule in this spot are tall/crowded together forming macula densa - monitors Na and Cl conc. of filtrate in DCT (chemoreceptors); - regulatory functions - JG cells secrete renin to influence systemic arterial BP; source of erythopoeitin for rbc production - can regulate blood flow through glomerulus to affect how much filtrate we form |
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Where are the macula densa cells located? What is their function?
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- in the renal tubule; where the CDT lies against the afferent arteriole of its own nephron
- they monitor the Na and Cl conc of the filtrate in the DCT; chemoreceptors |
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Where are the juxtaglomerular (JG) cells located? What is their function?
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- in the wall of the afferent arteriole; where the CDT lies against the afferent arteriole of its own nephron
- they are modified smooth muscle cells - JG cells secrete renin to influence systemic arterial BP; source of erythopoeitin for rbc production - mechanoreceptors - can regulate blood flow through glomerulus to affect how much filtrate we form |
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Identify and define the three steps involved in urine formation.
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- Glomerular filtration - hydrostatic pressure in glomerulus forces H2O and solutes across membrane into the capsillar space
- tubular reabsorption - into the blood from the filtrate - tubular secretion - from the blood into the filtrate |
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Describe the filtration membrane.
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- 3 layers:
- Glumerular capillary endothelum (of the capillaries themselves) - has fenestrated walls w/gaps b/w simple squamous ET cells of cap wall; permeable to water, small solutes but stops formed elements and plasma proteins - Basement membrane/lamina densa - a glycoprotein matrix that has extracellular proteins to anchor the 2 cellular layer together; acts as barrier to certain solutes b/c of -ve chage on proteins in membrane - visceral membrane of the glomerular capsule - potocytes have cellular extensions; allow narros slits b/w little foot processes; another size barrier; create a slit mem. if a big mol. gets caught, the cells will phagocytize it - mesangial cells surround glomerular cap, then can contract and change diameter, decreasing the surface area/amt. of filtrate formed |
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How does the structure of the filtration membrane contribute to the process of glomerular filtration?
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- the fenestrations and slits only let smaller molecules out and not bigger ones like plasma proteins
- the basement membrane's -ve charge keeps certain proteins out - the potocytes can phagocytize any large cell (plasma protein) that manages to slip through - keeps pp out so that too much H2O doesn't follow them from the blood - helps distinguish which things are filtered |
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What factors promote glomerular filstration? What factors oppose glomerular filtration?
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NFP(net filtration press) = GHP -(BCOP + CHP)
Promote: Glomerular hydrostatic pressure (55 mmHg) Oppose: blood colloid osmotic pressure; capsular hydrostatic pressure (small b/c fluid drain off into tubule system quickly) |
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Why is net filtration pressure (NFP) so much higher in the glomerulus than in the systemic capillaries
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- filtration enhanced by:
- greater permeability of filtration membrane - glomerular cap. present a large surface area (same SA as skin!) - glomerular BP is higher than systemic cap - afferent arteriole constricts so that BP drops sharply across afferent arteriole; efferent arteriole has smaller diameter than afferent, creates resistance |
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How does NFP affect the glomerular filtration rate (GFR)?
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- GFR is the total volume of filtrate produced in the kidneys per min (appx 125 mL/min) of filtrate
NFP = net filtration pressure, it determines the rate of filtration (the forces that promote filtration minus those that oppose it) - directly proportional to NFP - so if any of the pressures are changed, NFP changes and GFR changes |
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What effect does a change in glomerular hydrostatic pressure have on GFR?
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- GFR is the total volume of filtrate per minute
- the glomerular hydrostatic pressure is the force that promotes filtration - since NFP is the forces that promote filtration - the forces that oppose it, increase in GHP will increase the NFP - NFP is directly proportional to the GFR, so the GFR will increase |
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What is the effect on GFR of vasoconstriction/vasocilation of the afferent arterioles? the efferent arterioles?
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- afferent: dilation increases GFR, constriction will decrease it, b/c it lets less blood in.
- Efferent - dilation decreases GFR (glomerular filtration rate), constriction increases GFR because the blood backs up and there is more glomerular hydrostatic pressure |
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What effect does a change in plasma colloid osmotic pressure have on GFR?
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- it is one of the forces that opposes filtration
- it is created by the plasma proteins; so it makes the water want to flow into/stay in the cap, rather than being filtered out - so if you increase the BCOP (blood colloid osmotic press), you wil decrease the NFP (net filtration pressure) and thus decrease the GFR |
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Describe the composition and osmolarity of glomerular filtrate.
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- exactly the same as the plasma, minus the plasma proteins
- 300 mOsm; it will be isotonic |
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To what does the term renal autoregulation refer?
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- the kidneys ability to maintain a relatively constant GFR (about 125 mL/min) despite changes in systemic arterial pressure
- involves intrinsic mechanisms to alter its own vascular resistance - involves 2 mechanisms: myogenic mechanism and tubuloglomerular feedback mechanism |
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Describe the myogenic mechanism and tell how it promotes a stable GFR.
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- increase in systemic BP causes stretch of the walls in the afferent arteriole
- afferent arteriole vasoconstricts to protect the glomeruli from high BP - related/similar to the general tendency of vascular smooth musc to contract when its stretched - keeps the glomerular hydrostatic pressure from increasing too much |
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Describe the roles of the macular densa and the JG cells in the tubuloglomerular feedback.
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- promotes constriction/dilation of afferent arteriole as needed to maintain GFR
- directed by macula densa cells - low filtrate flow/low osmolarity triggers the macular densa cells (mechanoreceptors) to vasodilate to increase NFP, which increases GFR; visa versa |
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What cells release renin?
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- JG cells of macula densa secrete renin in kidney when BP is too low
- catalyzes angiotensinogen to antiogensin I in the pulmonary cap of teh lungs angiotensin converting enzyme turns it into antiotensin II which is a powerful vasoconstrictor |
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Describe the steps in the reacton cascade triggered by renin.
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- the kidneys release renin which catalyzes angiotensinogen to antiogensin I
- in the pulmonary cap of teh lungs angiotensin converting enzyme turns it into antiotensin II which is a powerful vasoconstrictor - blood pressure increases |
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What is the end procuct of the renin-angiotensin cascade and what are its effects?
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- angiotensin II
- effects: -- inc systemic BP -- in kidney greatest effect is on efferent arteriole (may increase GFR if moderate amounts -- stimulates adrenal cortex to secrete aldosterone which goes to distal tubule and inc. Na reabsorption if ADH is present -- stimulates contraction of mesangial cells around glomerular cap. which decreases surface area and thus amt of filtrate formed |
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What factors trigger renin release?
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- dec. stretch of JG(juxtaglomerular) cells caused by < 80 mmHg of BP
- stimulation of JG cells by activated macula densa cells - stimulation of JG cells by sympathetic nerve fibers - stimulation of JG cells by AT II |
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What is the effect of angiotensin II on GFR?
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- increases the NFP, so it increases the GFR
- as there is more press in the capsule, more fluid will be forced out, of course |
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How is release of atrial natriuretic peptide (ANP) stimulate? What are the effects of ANP?
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- secreted by atrial cells when there is in. stretch of atria caused by excercise, inc BP, inc blood volume, etc
Effects: - increases GFR - mesangial cells relax so bigger surface area on filtration membrane - dec Na+ reabsorption - increased urine production/diuresis - inhibited secretion of ADH, aldosterone and renin (the vasoconstrictors and reabsorbers) |
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Under what conditions would hte sympathetic division of the ANS override renal autoregulation and decrease GFR?
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- promoted by norepinepherine and norepinepherine
- decreased blood blos to kidneys results in increased flow to heart, brain, skeletal muscle - helps us deal with cardiovascular distress - causes shut down of the kidney - here, the vasoconstriction of afferent arterioles predominates - requires high levels of sympathetic outflow to overide the normal autoregulation |
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What is renal clearance?
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- the volume of PLASMA that is cleared of a certain solute in a given amount of time, usually 1 min.
- typically reported in units of ml/min |
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Describe the myogenic mechanism and tell how it promotes a stable GFR.
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- increase in systemic BP causes stretch of the walls in the afferent arteriole
- afferent arteriole vasoconstricts to protect the glomeruli from high BP - related/similar to the general tendency of vascular smooth musc to contract when its stretched - keeps the glomerular hydrostatic pressure from increasing too much |
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Describe the roles of the macular densa and the JG cells in the tubuloglomerular feedback.
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- promotes constriction/dilation of afferent arteriole as needed to maintain GFR
- directed by macula densa cells - low filtrate flow/low osmolarity triggers the macular densa cells (mechanoreceptors) to vasodilate to increase NFP, which increases GFR; visa versa |
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What cells release renin?
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- JG cells of macula densa secrete renin in kidney when BP is too low
- catalyzes angiotensinogen to antiogensin I in the pulmonary cap of teh lungs angiotensin converting enzyme turns it into antiotensin II which is a powerful vasoconstrictor |
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Describe the steps in the reacton cascade triggered by renin.
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- the kidneys release renin which catalyzes angiotensinogen to antiogensin I
- in the pulmonary cap of teh lungs angiotensin converting enzyme turns it into antiotensin II which is a powerful vasoconstrictor - blood pressure increases |
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What is the end procuct of the renin-angiotensin cascade and what are its effects?
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- angiotensin II
- effects: -- inc systemic BP -- in kidney greatest effect is on efferent arteriole (may increase GFR if moderate amounts -- stimulates adrenal cortex to secrete aldosterone which goes to distal tubule and inc. Na reabsorption if ADH is present -- stimulates contraction of mesangial cells around glomerular cap. which decreases surface area and thus amt of filtrate formed |
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What characteristics of inulin and creatinine make them useful in detemining clearance ( and GFR)?
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- they are freely filtered, neither reabsorbed, secreted nor metabolized by the cells of teh nephron
- so they should represent the same 125 ml/min of plasma that is filtered; all of that plasma should be cleared |
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Why is plasma creatinine the more useful index for GFR in clinical situations?
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- we have to inject inulin
- creatinine is natural; it is a breakdown product of creatinine phosphate in skeletal muscle that is usu. produces at a relatively constant rate @ a level proportional to muscle mass |
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If you were provided measures of plasma creatinine, urinc conc of creatinine and urine volume, how would you calculate GFR?
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-when amount filtered = amount excreted
- amount filtered = GFR X plasma conc. of substance - amount excreted = urinc conc of substance X volume of urine excreted/min so, GFR = (plasma substance conc. X urine volume/min)/ plasma conc of inulin |
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What is the maximal clearance value in a normal kidney?
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- 125 ml/min
- the amount of plasma that is filtered/minute, so it's the max amount that can be cleared |
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Why is the clearance value for PAH an index of renal blood flow?
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- PAH is freely filtered, not reabsorbed and completely secreted
- so, all of the plasma that enters teh kidneys is completely cleared of PAH - 625ml/min of blood goes through kidney even though ony 125 is filtered - so 625 is the value for PAH |
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Why is the normal glucose clearance equal to 0 ml/min?
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- glucose is fully reabsorbed back into the blood
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Describe what happens during tubular reabsorption (ie, H2O and solutes move from ____ to ___).
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H2O and solutes move from the tubule lumen into the blood of teh peritubular capillaries or vasa recta
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Describe what happens during tubular secretion (ie, H2O and solutes move from ____ to ___).
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- materials moved from the blood into the filtrate
- allows unnecessary/unwanted materials to be removed from blood |
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Why is the active reabsorption of Na+ so important to the overall process of tubular reabsorption?
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- it is the reabsorption of Na that creates an electrical gradient that favors reabsorption of anions
- anions: bicarbonate (HCO3-), chlorate ion - also establishes osmotic gradient to reabsorb water |
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What is transport maximum Tm? What happens when a solute in the filtrate exceeds its renal threshold?
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- Tm = when the carriers for a solute are saturated, working at there fastest rate; this rate limit is the Tm (mg/min)
- if it exceeds it, then you will pee out that substance, like diabetics with glucose |
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Generally describe the reabsorption and secretion activities in the various regions of teh renal tubule
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- PCT:
-- reabsorbed: sodium, sets up e. chem, virtually all nutrients, Cations (K, Mg, Ca), anions (Cl, HCO3-), water, urea and lipid soluble solutes, small proteins via endocytosis (digested inside PCT cells into AAs, b/c we don't want the osmotic press they create in the filtrate); 65% of filtrate reabsorbed here -- secreted: H+ via Na/H antiporters, small amts of creatinine + urea, ammonium ion - LOH: -- reabsorbed: descending (water can leave thru aquaporin I's, impermeable to solutes); ascending (impermeable to water, Na/K/2Cl symporters reabsorb them actively; also Na/H antiporters, Ca and Mg are passively reabsorbed via paracellular route) -- secretion - none - DCT: -- reabsorption - Na and Cl via Na/Cl symporter, Ca, H2O) -- secreted - H+ can be... - Collecting ducts/late DCT reabsorb: HCO3, K, Na, Cl Secrete: H, HCO3, K |
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Where is the Na+/K+/2Cl- symporter located? why is this important?
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- in the apical membrane of the thick ascending limb
- mean means of Na entry at the luminal surface ot hte thick portion of the ascending limb - works via 2ndary active transport |
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Describe the cotransport process involved in the reabsoprtion of glucose.
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- it's a Na/Glucose cotransport system in the PCT
- it uses secondary active transport to get the energy |
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Describe the process by which bicarbonate ions are reabsorbed in the PCT. What role to Na+/H+ antiporters play in this process?
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- the Na/H transporters allow for the secondary active transport of bicarbonate
- 80% of the filtered bicarbonate is reabsorbed here - via paracellular diffusion driven by electrochemical gradient for Cl - the pump sets up the electrochemical gradient needed |
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What process is involved in water reabsorption?
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- osmosis
- aquaporin I is present in the PCT and parts of the LOH to make the tubule freely permeable to H2O - through aq I, obligatory water reabsorption occurs, where water has to follow the reabsorbed sollutes - aquaporin 2 expressed in DCT, facultative water reabsorption b/c it's affected by ADH levels |
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In what part of the tubule is the greatest amount of water reabsorbed? In what part of the tubule is water reabsorption regulated by ADH?
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- most is reabsorbed in the PCT - the distal part of the tubule - the end of the DCT and the collecting duct
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How does aldosterone help regulate reabsorption in the distal convoluted tubule?
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- aldosterone regulates teh principle cells; makes them reabsorb more sodium and secrete more potassium
- triggered by high K in plasma - it increases the number of Na leakage channels in teh apical surface for the to diffuse into the cell - virtually all of the K was reabsorbed in the PCt, so if the body has too many, we have to secrete it here - due to aldosterone's effects, there is virtually no urinary Na excretion (affects Na and K, not H2O... H2O can only follow if ADH is present) |
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What factors trigger aldosterone release?
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- dec blood volume or BP
- hyponatrimia - hyperkalemia - the Renin-angiotensin system |
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Describe the osmotic gradient in the interstitial fluid of the renal cortex and medulla.
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- the fluid is isotonic near the cortex and becomes more and more hypertonic as it gets closer to the medulla
- this gradient in fluid allows us to keep absorbing H2O in the decending LOH |
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How does the countercurrent mechanism help establish and maintain the renal osmotic gradient?
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- the decending loop is permeable to water; as it goes closer to the medulla, the interstitial fluid becomes more hypertonic, so it keeps drawing the water out of the tubules, even though the tubules themselves are becoming more concentrated
- then it becomes permeable to Na and Cl, so they flow out of the now very concentrated solution in the tubule; as it goes up, tubule= less conc, but so does the medulla, so Na + Cl keep flowing out till the osmotic gradient is the same at the top as when it came in, but w/much less h2o and na and cl |
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What role does the vasa recta play in maintaining the medullary osmotic gradient?
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- need to keep the more hypertonic area towards the cortex in order for the countercurrent mechanism to work
- the vasa recta is a low press cap bed w/permeable walls - can maintain rather than dilute osmo of interstitium - as a result, prevents salts from rapidly diffusing into the vessel and cleansing from the interstitial fluid - basically, because of the hairpin turn, it ballances it's diffusion effects out perfectly |
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How does urea recycling help to establish the medullary osmotic gradient and promote water reabsorption? In what segment of the tubule is urea reabsorbed?
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- urea diffuses out of the collecting ducts deep in the medulla - it helps build up about half of the osmolarity of the medullary interstitial fluid, which allows water to diffuse out of the decending limb. then it reabsorbs into the ascending
- it's deep in the medulla that this happens, b/c the collecting duct is permeable to urea so it can diffuse out, but not permeable to the other things, so the amount of other particles would stay the same in filtrate leaving the nephron |
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How does the medullary osmotic gradient promote the formation of a concentrated urine?
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- in the decending loop, water leaves the filtrate as the interstitial fluid becomes more and more hypertonic
- in the ascending limb, water can't come back in, so instead Na and Cl leave, in order to make the filtrate closer to the hypertonicity of the medullary osmotic gradient. |
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Compare the osmolarity/tonicity of the following solutions: body fluids (blood and interstitial fluid), glomerular filtrate, filtrate in teh PCT, filtrate at the deepest part of the LOH in juxtamedulary nephrons, filtrate in the DCT, urine @ beg of collecting tubule, urine @ end of collecting tubule.
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- body fluids - 300 - they are isotonic to the glomerular filtrate
- glomerular filtrate - isotonic to the body fluids - PCT - increasing as water leaves tubule, all the way up to 1200 - LOH - 1200, the most hypertonic? spot ever - DCT - gets less and less hypertonic till it's isotonic - beg of CT - hypotonic - 100 - end of CT - hypotonic - 100 it isn't permeable, so doesn't change (except to urea) |
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What is the effect of ADH on urine volume and concentration?
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- increases the aquaporin 2 channels in the distal tubule
- promotes water reabsorption into blood of peritubular cap., until the osmolarity of the filtrate - the osmolarity of hte interstitial fluid; depending on level of ADH secretion, urine conc may rise as high as 1200-1400 mOsms (the same as the interstitial fluid deep in the medulla) - less volume, more conc |
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Explain the physiologic mechanisms involved in maintaining homeostasis when the osmolarity of body fluids increases. What happens when the osmolarity decreases?
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too little water in body - ADH and aldosterone are secreted
- aldosterone makes the principle cells in the late DCT absorb more Na and secrete more K. - the ADH causes aquaporin 2 in the collecting duct to make it permeable to water, so it's reabsorbed, as the duct passes through the deep parts of the medulla - too much water? (high osmolarity) - those two are inhibited so the water will leave in the duct and be peed out |
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Describe the composition and pH of urine.
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- clear, pale, slight odor
- pH = 6 (4.5-8) - water (95%) - Solutes: nitrogenous wastes (urea, creatinine, uric acid), electrolytes, other substances (drugs, excess vitamins) - in decreasing conc order: urea, Na, K, phosphate and sulphate ions, creatinine, uric acid |
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What are the metabolic sources of urea, uric acid, and creatinine?
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urea - AA breakdown
creatinine - metabolite of creatine phosphate wich stores e. for ATP regeneration uric acid - nucleic acid breakdown |
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Trace the flow of urine from teh collecting tubules to the point where it leaves the body.
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- collecting tubules
- minor calyx - major calyx - renal pelvis - ureter - bladder - urethra |
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Describe the structure of the ureter
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- no valves @ ureter/bladder jct
weight of bladder as it fills compresses ureters @ this jct to prevent backflow of urine 3 tissue layers: Mucosa - deep one; continuous w/kidney pelvis and bladder; transitional ET w/underlying lamina propria; goblet cells that secrete mucus for protection Muscularis - smooth musc. (internal longitudinal and external circular layers); peristalsis to propel urine to bladder Adventitia - continuous w/fibrous renal capsule and peritoneum |
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How is urine propelled through the ureter to the urinary bladder?
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- 2 layers of smooth muscle (the internal longitudinal and external circular) layers of the middle mucsularis layer contract
- peristalsis |
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Describe the structure of the urinary bladder.
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- retroperitoneal
- 3 openings (2 ureters, 1 urethra; trigone is triangle shaped area b/w openings - 3 layers Mucosa - deep; transitional ET w/underlying lamina propria; rugae present when empty Muscularis - detrusor muscle; 3 sheets of smooth muscle tissue; contract during urination; internal urethral sphincter Adventitia - along inferior/poserior surface Serosa - on anterior surface the last 2 are the superficial layer |
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What is the detrusor muscle? What does it do?
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- found in the middle muscularis layer of the bladder
- composed of 3 sheets of smooth musc - contracts during urination to propell urine |
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Compare and contrast the male and female urethras
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Females: 3-4 cm; directly posterior to pubic symphysis; tightly bound to ant vaginal wall by fibrous CT; anterior to vaginal opening
Males - 20 cm; goes through prostate, urogenital diaphragm andpenis; subdivided into 3 regions (prostatic, membranous, penile); serves as conduit for semen as well as urine |
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Describe the micturation reflex.
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- bladder fills; more than 200 ml causes stimulation of stretch receptor s in wall
- impulses to micturation reflex center in sacral spinal cord - micturation reflex - PNS fibers from S2 and S3: rhythmic contractions of detrusor musc; inhibits contraction of internal urethral sphyncter; interneurons go to brain, decide to let the external urethral sphyncter relax or not - if not, reflex arc triggered atain when 200-300 more ml are in bladder |
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Obligatory water reabsorption
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- through aquaporin I in PCT and parts of LOH;
- if we reabsorb solutes, we HAVE to reabsorb H2O, it's automatic |
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Facultative water reabsorption
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- through aquaporin 2
- we can modify the amt that we absorb using ADH, to vary the number of aq2 that is expressed in the distal portions of the tubule |
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transcellular reabsorption
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- transport across luminal membrane
- diffusion through cytosol - transport across basolateral membrane - movement through interstitial fluid and into capillary |
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paracellular reabsorption
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- movement through leaky tight jct, particularly in the PCT
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erythropoietin
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Also called hematopoietin or hemopoietin, it is produced by the peritubular capillary endothelial cells in the kidney, and is the hormone that regulates red blood cell production.
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diuretic
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- elevates volume of urination
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