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urinary system consists of what
kidneys, ureters, urinary bladder, urethra
urinary system does what
regulates water balance, electrolyte balance, acid-base balance, rids body of waste of metabolism, foreign chemicals, drugs, and food additives, and serves a s a minor endocrince organ and produces renin and erythropoietin
where are kidneys located
between the levels of the 12th thoracic and the 3rd lumbar vertabrae
hilus
concave medial surface of kidney
renal cortex
outer portion of kidney which contains capillary tufts and convoluted tubules
renall medulla
inner portion of kidney and contains renal pyramids and renal columns
acute renal failure
sudden loss of kidney function, usually associated with shcok or intense renal vasoconstriction, that lasts from a few days to many weeks
cystitis
inflammation of the urinary bladder
hematuria
blood in the urine
hemodialysis
method of clearing waste products from the blood in which blood passes by the semipermeable membrane of the artificial kidney and waste products are removed by diffusion
nocturia
night urination
oliguria
urinary volumes less than 500ml/day
polyuria
excessive urine output
uremia
retention of urinary constituents in the blood, owing to kidney dysfunction
Nephron and parts
functional unit of the kidney, consisting of the glomerulus, glomerular capsule (Bowman's capsule), the proximal convoluted tubule, the nephron loop (loop of Henle), the distal convoluted tubule, and the collecting duct
how many nephrons/kidney
over 1 million nephrons per kidney
glomerulus
consists of a network of about 50 capillaries. The capillary endothelium lining the glomerulus has many circular fenestrations, or pores, which are larger and more numerous than anywhere else in body.
permeability of glomerulus
100-1000X more permeable than typical capillaries
glomerular capsule (Bowman's capsule)
double-walled cuplike structure composed of squamous epithelium. Outer layer is continuous w/ the proximal tubule. Inner layer is composed of podocytes that are closely associated with the glomerular capillaries
proximal convoluted tubule
single layer of cuboidal cells containing microvilli (as a brush border) that greatly increase the surface are. Terminates in the first portion of the nephron loop, called the descending limb of the nephron loop
nephron loop
has descending and ascending thin limbs and an ascending thick portion. Thin segments are lined w/ flat squmous cells that lack microvilli, as do the cuboidal cells that compose the thick segment, which runs between the afferent and efferent arterioles
distal convoluted tubule
begins at the macula densa, a mass of specialized epithelial cells of the tubule wass, located next to the afferent arteriole. Shorter and less microvilli than the proximal confoluted tubule. last part of nephron and empties into the collecting duct
3 major fxns of nephron
glomerular filtration, tubular reabsorption, tubular secretion
glomerular filtrate
portion of the blood plasma that enters the capsule. amounts to about 180L/day=45 gallons/day
mechanisms that cause such large amounts of glomerular filtrate
1)high hydrostatic pressure of the blood (45 to 60 mmHg) in the glomerulus 2)large numbers of pores, which are larger than most pores in blood capillaries
substances in blood that are in glomerular filtrate and those that aren't
in filtrate water, electrolytes, glucose, amino acids, urea, hormones, vitamins; not in plasma proteins, RBC's, WBC's and platelets because they're too big
presence of RBC's or protein in the urine indicates what?
hydrostatic pressure in the glomerular capillaries is excessively high or that there is a defect in the glomerular membrane
glomerular filtration rate (GFR)
about 120 ml/minute, 7.5 L/hour, 180 L/day
regulation of GFR
via vasoconstriction and vasodilation of afferent arterioles results from both extrinsic (sympatheti nerves) and intrinsic (locally produced chemicals) mechanisms
Measurement of GFR
measure excretion and plasma concentration of a substance that is freely filtered into Bowman's capsule and is not secreted or reabsorbed by tubules. measure amount of substance in urine per unit time
inulin
a polymer of fructose (extracted from plants). since it is not produced by the body and not secreted or reabsorbed it is used to measure the GFR
GFR equation
((urine volume (ml/min))(inulin conc. in urine (mg/ml)))/(inulin conc. in plasma (mg/ml))
tubular reabsorption
transfer of fluid and solutes out of the lumen of the nephron through the interstitial space and into the pertitubular capillaries
% of filtrate reabsorbed from the renal tubules
99%
% of water reabsorbed by tubular reabsorption
99%
% of sodium reabsorbed by tubular reabsorption
99.5%
% of glucose reabsorbed by tubular reabsorption
100%
% of urea reabsorbed by tubular reabsorption
50%
% of phenol reabsorbed by tubular reabsorption
0%
tubular reabsorption occurs throughout the "blank", but primarily in the "blank" portion
renal tubules, proximal convoluted
trans-epithelial transport
transport of substances by tubular reabsorption
% of reabsorbed material that is reabsorbed through the proximal convoluted tubule
80%
% of reabsorbed material that is reabsorbed through the nephron loop
6%
% of reabsorbed material that is reabsorbed through the distal convoluted tubule
9%
% of reabsorbed material that is reabsorbed through the collecting duct
4%
parts of reabsorption physiology that are under ADH control
distal convoluted tubule and collecting duct
two ways substances are reabsorped by the nephron
diffusion (H2O and urea) and active transport (glucose)
aldosterone
regulates the reabsorption of Na+ in the distal and collecting duct (renin-angiotensin-aldosterone system)
where is glucose reabsorbed?
proximal tubule
normal glucose concentration in blood
100mg/100ml
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