Structure & Function of the Renal and Urologic Systems Flashcards
endocrine function of the kidneys
secrete renin to regulate blood pressure
secrete erythropoietin to produce new erythrocytes
secretes 1,25-dihydroxyvitamin D3: metabolism of calcium
the kidneys also perform _______
gluconeogenesis: synthesis of glucose from amino acids
what is the functional unit of the kidney and urine forming unit of the kidney?
nephron
3 types of nephrons
superficial cortical nephrons
midcortical nephrons
juxtamedullary nephrons
superficial cortical nephrons
make up 85% of all nephrons, which extend partially into the medulla
internet says: shorter, mostly in cortex of kidney, and produce “standard” urine
midcortical nephrons
have short or long loops
internet says: Midcortical nephrons with glomerulus in the mid cortex and short loops that bend in the outer medulla (10%). Other mid cortical nephrons have loops of intermediate length that bend at various points in the inner medulla
juxtamedullary nephrons - what process are they important for?
lie close to and extend deep into the medulla and are important for the process of CONCENTRATING URINE; SECRETE RENIN
glomerulus
tuft of capillaries
bowman glomerular capsule
Bowman space - space inside Bowman capsule
circular space b/w visceral and parietal epithelium
mesangial cells
secrete mesangial matrix; lie b/w and support the glomerular capillaries
SOME CONTRACT SIMILAR TO SMOOTH MUSCLE CELLS TO REGULATE GLOMERULAR CAPILLARY BLOOD FLOW
have phagocytic properties and release inflammatory cytokines and growth factors
parts of the renal corpuscle
glomerulus, Bowman glomerular capsule, mesangial cells
glomerular endothelial cells synthesize what? what do these things regulate?
synthesize nitric oxide (a vasodilator) and synthesize endothelin-1 (a vasoconstrictor)
both of which regulate glomerular blood flow
visceral epithelium of the Bowman capsule is composed of cells called? What do these cells do?
podocytes - foot-like processes
form an elaborate network of intracellular clefts called filtration slits; MODULATE FILTRATION
Process of filtration w/i kidneys
plasma filtrate from glomerulus passes through the glomerular membrane into the Bowman space to form the primary urine
the glomerulus is supplied by _____ and drained by ______
supplied by the afferent arteriole, and drained by the efferent arteriole
Juxtaglomerular apparatus (JGA) consists of
juxtaglomerular cells, macula densa
juxtaglomerular cells are located where and do what?
located around the afferent arteriole where the afferent arteriole enters the glomerulus
control renal blood flow (RBF), glomerular filtration, and renin secretion occurs at this site
macula densa - what does it do and where is it located?
portion of the distal convoluted tubule with SPECIALIZED SODIUM AND CHLORIDE-SENSING CELLS is located b/w the afferent and efferent arterioles
from internet: The macula densa participates in the regulation of renin release from juxtaglomerular granular cells. Renin secretion depends on NaCl delivery to and reabsorption by the macula densa cells at the end of the TAL.
parts of renal tubules
proximal tubule, loop of Henle, distal tubule, collecting duct
proximal tubule - main thing done here?
lined with microvilli to increase surface area and enhance reabsorption
*tubular transport slide - ACTIVE REABSORPTION OF SODIUM (MAJORITY), secretion of hydrogen foreign substances, isotonic fluid
loop of henle - main things?
transport solute and water, contributing to the hypertonic state of the renal medulla
Tubular transport slide:
- CONCENTRATION OF URINE
- Descending loop: WATER REABSORPTION, sodium diffuses in
- Ascending loop: SODIUM REABSORBED (BY ACTIVE TRANSPORT), water stays in
- Urea secretion in thin segment
distal tubule
adjusts acid-base balance by excreting acid into the urine and forming new bicarbonate ions
collecting duct
contains principal cells that resorb sodium and water and excrete potassium and intercalated cells that secrete hydrogen or bicarbonate and potassium
*on tubular transport slide it says collecting ducts:
reabsorption of sodium, and water only with ADH
-reabsorption or secretion of sodium, potassium, hydrogen
-Final concentration
*tubular secretion = transfer of substances from the peri-tubular capillaries to the tubular lumen (don’t think this is what secretion means in this scenario)
bladder bag components
detrusor muscle and trigone
detrusor muscle
smooth muscle in bladder
trigone
smooth triangular area lying b/w the opening of the 2 ureters and urethra
urethra - what does it contain and how long M vs. F?
internal sphincter - smooth muscle located at junction of bladder and urethra
external sphincter - striated skeletal muscle under voluntary control
b/w 3-4 cm long in females
b/w 18-20 cm long in males
the detrusor muscle is the smooth muscle in the bladder- how does it contract?
contracts with parasympathetic fibers (autonomic NS)
skeletal motor neurons in the pudental nerve (somatic) of the urethra control what?
external urethral sphincter
glomerular filtration rate (GFR)
filtration of plasma into the Bowman space per unit of time
takes 20% of RBF (120 to 140mL/min)
GFR directly related to what?
Directly related to the perfusion pressure in the glomerular capillaries
If mean arterial pressure decreases or vascular resistance increases, then the RBF and GFR do what?
decrease (both RBF and GFR decrease)
myogenic mechanism (stretch) - as systemic pressure declines, glomerular perfusion _______
glomerular perfusion increases
stretch on the afferent arteriolar smooth muscle decreases, and the arteriole relaxes - therefore delivering more blood to the glomerulus
an increase in systemic pressure _______ glomerular perfusion
decreases
*causes the arteriole smooth muscle to contract, thereby decreasing blood flow to the glomerulus
tubuloglomerular feedback (sodium chloride content) - when sodium filtration increases, GFR _____ and macula densa cells do what?
GFR decreases and macula densa cells stimulate afferent arteriolar vasoconstriction
- when sodium filtration decreases, the opposite occurs – GFR increases
- fluid from the blood enters the nephron by filtration
SNS neural regulation
vasoconstriction occurs (diminishes GFR) regulate size of afferent and efferent arterioles, thus renal blood flow
baroreceptor reflex neural regulation
vasoconstriction of afferent arterioles with activation of a1-adrenoreceptors
decreases glomerular perfusion and GFR
exercise and change in body position - neural regulation
activate renal sympathetic neurons, causes mild vasoconstriction
(GFR decreases during exercise)
severe hypoxia - neural regulation
stimulation of chemoreceptors - decreases RBF by means of sympathetic stimulation
RAAS does what?
increases systemic arterial pressure, and increases sodium reabsorption
*renin: enzyme is formed and stored in afferent arterioles of the juxtaglomerular apparatus
nephron filtration
movement of protein-free plasma across the glomerular membrane (hydrostatic pressure) - from blood to nephron is what internet said
tubular reabsorption
movement of fluid and solutes from tubular lumen to the peritubular capillaries
tubular secretion
transfer of substances from the peritubular capillaries to the tubular lumen
excretion
elimination of a substance in the final urine
tubular transport - proximal tubule what does it do?
active reabsorption of sodium (majority) and secretion of hydrogen foreign substances - isotonic fluid
loop of henle - what does it do?
CONCENTRATION OF URINE
descending loop - WATER REABSORPTION, sodium diffuses in
ascending loop - SODIUM REABSORBED (BY ACTIVE TRANSPORT), water stays in
urea secretion in thin segment
distal tubule - what does it do? type of fluid - iso, hypo, hyper?
reabsorption of sodium, and water only with ADH, bicarbonate
secretion of potassium, urea, hydrogen, and some drugs
isotonic or hypotonic
collecting ducts - what do they do?
reabsorption of water only with ADH; reabsorption or secretion of sodium, potassium, hydrogen; final concentration
when GFR spontaneously decreases or increases - renal tubules and, PRIMARILY THE _____, automatically adjust what?
primarily the proximal tubules, automatically adjust their rate of reabsorption of sodium and water to balance the change in GFR
*constant fraction of filtered sodium and water is reabsorbed from the proximal tubule
