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30 Cards in this Set

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Urea
Carrier of excess Nitrogen from protein breakdown, since Nitrogen in form of ammonia is toxic.
1. Skin consists of
2. Skinis controlled by
1. ions, water, & urea
2. not controlled by amount of waste that needs to be excreted, but by temperature and level of sympathetic nervous system activity.
1. What is kidney?
2. What do kidneys excrete?
1. A sensitive regulator that must keep concentration @ optimal levels. Variation greater than 15% is fatal due to dysfunction of cells.
2. Urea, Na+, bicarbonate, & water.
Function of the kidneys
Homeostatic role: consistancy of physiological variables.
1. excrete hydrophilic wastes
2. maintenance of constant solute concentration, pH, and fluid volume.
**constant fluid volume important for blood pressure & cardiac output.
3 steps in kidney role
1. filtration
2. selective reabsorption
3. concentration/dilution
Filtration
high blood/filtration pressure @ glomerulus. Cells & proteins remain in blood, water & small waste products go into renal tubule.
*filtrate --> urine
Selective reabsorption
takes back useful items (glucose, water, a.a.) at proximal tubule, close to Bowman's capsule.
*Not regulated, the rate should be constant.
Concentration/dilution
conc/dil of urine @ distal tubule, close to collecting duct. Regulated by ADH (fluid volume) and aldosterone (Na+)
Where blood enters and returns in the circulatory system
blood enters renal artery (lower portion of aorta). Purified blood returns by large renal vein (inferior vena cava)
The passage of urine.
collecting duct --> papillae (tips of pyramid where urine leaves medulla) --> calyx (gaps between pyramids) --> renal pelvis (basin-like area inside kidney) --> ureter --> bladder
2 things nephron consists of.
1. Renal tubule: receives filtrate at one end, empties to collecting duct.
2. Blood vessels that carry arterial blood to tubule and filtered blood from tubule.
The path blood travels in nephron
Afferent arteriole --> glomerulus --> glomerular basement membrane --> Bowman's capsule --> proximal tubule --> Loop of Henle (descending limp) --> Loop of Henle (ascending limp) --> distal tubule --> collecting duct
What happens to large molecules in afferent arteriole?
they can't pass thru glomerulus, thus not filtered. They flow to efferent arterioles.
Proximal convoluted tubule
Near Bowman's capsule where selective reabsorption occurs. Chooses what to absorb, but the amount is not regulated.
Most filtered water, glucose, & a.a. are reabsorbed here.
Distal convoluted tubule
Near collecting duct where appropriate urine volume and osmolarity adjustments are made. Controlled by 2 hormones: ADH and aldosterone.
ADH (Antidiuretic hormone)
released by [posterior pituitary],
1. Prevents diuresis (waterloss in urine) by increasing water reabsorption.
2. Ultimately makes distal tubule permeable to water (w/o ADH, water impermeable).
1. When is ADH secreted?
2. What is its result?
1. secreted as plasma volume decreases and/or osmolarity increases.
2. result: concentrated urine and dilute blood.
How does osmolarity affect water flow?
Water flows out of the tuble because renal medulla has a very high osmolarity, which causes water to exit the tubule by osmosis.
Aldosterone
Released by [adrenal cortex] when blood pressure is low. Causes increased reabsorption of Na+ by distal nephron.
What is the result of Aldosterone secretion?
Increased plasma osmolarity: increase in thirst and water retention, thus increased blood pressure and volume.
How are ADH and Aldosterone related?
Aldosterone causes Na+ reabsorption, which increases plasma osmolarity. Then ADH causes water reabsorption.
What parts of nephron are located in renal cortex (outer layer of kidney)?
Bowman's capsule and proximal/distal convoluted tubule.
1. Describe Loop of Henle
2. Name 3 types of limbs of Loop of Henle.
1. Dips down into renal medulla (inner part of kidney)
2. Descending limb, thin ascending limb, & thick ascending limb.
Function of the three limbs of Loop of Henle
1. Descending: permeable to H2O, but not to ions. Water exits and filtrate becomes concentrated.
2. Thin ascending: not permeable to H2O, but loses ions from high-osmolarity filtrate.
3. Thick ascending: transports salt out of filtrate by active transport. Medulla becomes very salty, thus sucking out water from collecting duct by osmosis. That's why urine has higher osmolarity than plasma.
Describe Vasa Recta and compare it to Loop of Henle
blood vessels wrapped around Loop of Henle. Flows in countercurrent direction of filtrate inside Loop of Henle, making it easier to pick up water and other molecules.
Juxtaglomerular apparatus (JGA)
Specialized contact point between juxtaglomerular (JG) cells in afferent arteriole and macula densa in distal tubule.
Juxtaglomerular (JG) cells
When there's a decrease in blood pressure, secretes renin (enzyme) that ultimately catalyzes Angiotensin II, which increases blood pressure & stimulates a release of aldosterone.
2 functions of macula densa
When filtrate osmolarity decreases, it
1. stimulates JG cells to release renin, thus increasing blood pressure.
2. causes dilation of afferent arteriole, thus increase in blood flow
plasma pH and its relation to urine
1. when plasma pH is high, HCO3- (basic) is excreted as urine.
2. when pH is low, H+ (acidic) is excreted.
Carbonic anhydrase
An enxyme that catalyzes conversion of CO2 into H2CO3, that splits into HCO3- and H+.
**renal pH adjustment is very slow. Very fast in lung.