Urinary system part 1 Flashcards
what is the urinary system responsible for
water and electrolyte homeostasis, osmoregulation, and acid-based balance
what is the primary secretory function of the urinary system
excretion of toxic and metabolic waste products, especially urea and creatinine
what is creatinine
nitrogen containing compounds from metabolism of proteins
what is urea
primary nitrogenous waste products in mammals, SOLUBLE
which is soluble: urea or uric acid
urea
what does BUN stand for and what does it include
blood urea nitrogen- includes urea, creatinine, uric acid, ammonia
what is the kidney responsible for
metabolism and excretion of various drugs
what do kidneys synthesize and how does it contribute to their function
renin and maintain a normal BP via renin- angiotensin- aldosterone system
what produces erythropoietin and what does it do
produced by kidney, stimulates RBC production
what converts vitamin D from its inactive to active form
liver and kidney
describe the kidney
retroperitoneal organs with fibrous connective tissue capsule
where do blood vessels and ureters enter/exit the kidney
at the hilus
what is each kidney supplied by and what does it branch into
renal artery which branches to form interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles to glomeruli
what does the cortex contain
mostly renal corpuscles and convoluted tubules
what does the medulla contain
mostly loops of henle, collecting tubules, collecting ducts
describe the transitional epithelium unique to urinary tract
varying number of layers- stratified, cuboidal to polygonal with scalloped outline “umbrella cells”
what does the highly distensible nature of the transitional epithelium allow for
changing urine volumes
what is the functional unit of the kidney
the nephron
what is the nephron embryologically derived from
nephrogenic blastema- part of the developing urogenital ridge
what are the 3 major types of nephrons
-cortical or subcapsular
- juxtamedullary
-intermediate
where are cortical nephrons located and describe their loops of henle
located in outer rim of cortex and have short loops of henle
where are juxtamedullary neprhons located and describe their loops of henle
located adjacent to medulla, have long loops of henle
where are intermediate nephrons located and describe their loops of henle
in middle of cortex, have intermediate length loops of henle
what are the two major components to a nephron
renal corpuscle and renal tubule
what does the renal corpuscle do
filter blood plasma
what does the renal tubule do
collects filtrate
what are the 2 components of the renal corpuscle
bowman’s capsule and glomerulus
describe the capsule epithelium
single layer of squamous epithelial cells resting on basement membrane
what is another term for the capsule epithelium
parietal layer
what does the parietal layer form
hollow, dilated end of proximal convoluted tubule, surrounding glomerulus
what does the parietal layer continue onto glomerulus as
visceral layer
what are podocytes
highly modified cells of visceral layer
where is Bowman’s space
between visceral and parietal layer
what does Bowman’s space do
collects glomerular filtrate and empties into renal tubule
what is the glomerulus
network of densely packed, anastomosing, fenestrated capillaries
what is the glomerulus supplied by
afferent and efferent arterioles
what does blood plasma become after it passes through several cell layers
filtrate
what is filtrate
water and small molecular weight molecules filtered from blood into Bowman’s space
what does the first layer of the glomerulus consist of
capillary endothelial cells of glomerulus and glomerular basement membrane
why is the luminal surface of capillary endothelium negatively charged
due to surface layer of glycoprotein podocalyxin
what does podocalyxin do
sets up negatively charged barrier, prevents loss of anions, large protein molecules
what does the glomerular basement membrane act as
physical barrier and ion selective filter
what is the subpodocyte space
space between capillary basement membrane and second layer of cells
what do podocytes surround
glomerular capillaries that possess cytoplasmic extensions known as foot processes
what do long primary foot processes give off
secondary foot processes called pedicels
what are the spaces between processes called
filtration slits
what do filtration slits contain
slit diaphragms made of nephrin
what do slit diaphragms do
act as additional barrier and restrict passage of large macromolecules, proteins, negatively charged molecules and blood cells
what is the function of podocytes
phagocytic and can remove trapped macromolecules
what is resultant glomerular ultrafiltrate passed to
renal tubule
what are the 4 distinct zones of the renal tubule
-PCT
-loop of henle
- DCT
- collecting tubule/duct
what is the renal tubule lined by
simple, cuboidal epithelium
what is the primary function of renal tubule
selective resorption of water, inorganic ions, and large molecules from glomerular filtrate and concentration of waste products
where is the PCT located
in the cortex only
what happens in the PCT
primary site of water resorption (also Na and Cl, and proteins, AAs, and sugars)
what is the water resorption in the PCT facilitated by
aquaporins
what are aquaporins
integral proteins forming specialzied pores or channels for transport of H2O in brush border of epithelial cells
describe the epithelium in the PCT
simple cuboidal epithelium with apical microvilli
what are the 4 parts of the loop of henle
-pars recta (thick descending limb)
- thin descending limb
- thin ascending limb
- thick ascending limb
where is the loop of henle located
bulk of loop extends into medulla
describe the length of thin limbs in juxtamedullary nephrons and cortical nephrons
long in juxtamedullary nephrons and short in cortical nephrons
describe the epithelium of the thin limb and thick limb
thin limb has simple squamous epithelium and thick limb has simple cuboidal epithelium
describe the epithelium of the pars recta
brush border of apical microvilli
what is the loop of henle surrounded by
vasa recta
what is the function of the countercurrent multiplier
functions to genreate high osmotic pressure in ECF of renal medulla via Na-K pumps in thick ascending limb of loop of Henle
how is the cortico-medullary interstitial gradient formed
higher extracellular Na in medulla combined with water resorption by PCT in cortex
what does the cortico-medullary interstitial gradient produce
counter current multiplier system of urine concentration
what does the counter current multiplier system of urine concentration result in
production of hypertonic urine
what is the DCT
a continuation of thick ascending limb of loop of henle
where is the DCT located
in the cortex
describe the epithelium of the DCT
simple cuboidal epithelium with short apical microvilli but lacks distinct brush border
what is the function of the DCT
responsible for active resorption of Na and Ca coupled with secretion of H and K ions
what 2 cell types is the DCT controlled by
principal cells and intercalated cells
what do principal cells do
resorb Na and water, secrete K
what do intercalated cells do
resorb K and secrete H
what hormone controls the DCT
aldosterone
what is the collecting tubule
terminal portion of the nephron
what do several collecting tubules converge to form
collecting duct
what are collecting tubules visible as
medullary rays
what epithelium lines collecting tubules
thick, simple cuboidal to columbar epithelium
where do the collecting tubules converge
at renal papilla
what is the function of collecting tubules
Na resorption, maintenance of acid-base balance, K secretion and resorption
what cells do collecting tubules contain
principal and intercalated cells
are the epithelial cells of the collecting duct permeable to water
no, however in presence of ADH collecting tubules become permeable and will resorb water
what secretes ADH
posterior pituitary
what 3 things work together to form counter current exchange mechanism to concentrate urine
loop of henle, collecting tubule, and vasa recta
what is the difference between PCT and DCT
PCT are twice as long and much more convoluted
what are most tubules in cortex
PCT
describe the appearance of PCT and DCT in cross section
round with cuboidal epithelium with or without brush border
describe the difference in appearance of DCT and PCT
- DCT are more oval to elongate with thinner, flatter but still cuboidal epithlium
- DCT lighter staining cytoplasm, nuclei are more prominent
what is mostly seen in the medulla
mostly loop of henle, fewer collecting tubules, and occasional collecting ducts and surrounding blood vessels
how do you identify loop of henle in cross section
smallest tubules with squamous to cuboidal epithelium
how do you identify collecting tubules in cross section
medium sized
how do you identify collecting ducts in cross section
largest, with simple cuboidal epithelium
