Urinary System Flashcards
What are the two main functions of the kidneys?
- Maintain electrolyte homeostasis
2. Maintain water homeostasis (BP)
Name three endocrine functions of the kidney.
- Make EPO
- Renin
- Vitamin D (1,25-hydroxycholecalciferol)
Where does blood enter the kidneys?
At the hilum
Name the arterial arrangement of the kidneys, starting at the renal artery.
Renal artery –> segmental artery –> interlobar artery –> arcuate artery –> interlobular artery –> glomerulus
Which artery types are found at the cortex-medullary boundary?
Arcuate arteries.
What do the efferent arterioles that leave the glomeruli become?
Either peritubular capillaries (if in the cortex) or medullary vasa recta.
What is a renal corpuscle?
Glomerulus + Bowman’s capsule
What is a nephron?
Renal corpuscle (glomerulus + Bowman’s capsule) + convoluted tubules.
What is a uriniferous tubule?
Nephron + collecting duct.
Can renal corpuscles be found in the renal medulla?
Nope
What cells arise from the inner layer (viscera) of Bowman’s capsule?
Podocytes.
What are the spaces called between the podocyte processes?
Filtration slits.
What makes up the filtration barrier?
Filtration slits + glomerular basement membrane
What cells synthesize the glomerular basement membrane?
Podocytes and endothelial cells.
How large can a molecule be and pass through the glomerular filtration barrier?
Up to 70 kDa
What is the composition of the glomerular basement membrane?
Type IV collagen, laminin, proteoglycans
What are mesangial cells? Where are they found?
Supporting cells found in the endothelial basal lamina of the glomerulus that perform physical support, repair, phagocytosis, and BP monitoring.
What happens to the filtrate in the PCT?
Resorption of sugars, AAs, salts.
What is found on the apical surface of PCT cells?
Enzyme-rich brush border (microvilli)
What is found on the basal surface of PCT cells?
Mitochondria-rich basal infoldings to pump ions into the interstitium.
What cell type is found in the DCT? Do they have apical specializations? Do they have a lot of mitochondria?
Low cuboidal with diminished brush border. Fewer mt than PCT cells so they are clearer.
Which portion of the nephron is sensitive to aldosterone?
The DCT. It causes increased Na+ resorption to increase BP.
What happens in the descending loop of Henle?
Water leaks out of the loop and into the interstitium.
What happens in the ascending loop of Henle?
Na+ is pumped into interstitium. Impermeable to water.
What are medullary rays?
Clumps of collecting ducts in the center of renal lobules.
Are collecting duct cells permeable to water?
Only in the presence of ADH.
What two cell types are found in the CD and what do they do?
- Intercalated cells. Subtypes: alpha can excrete H+ and beta can excrete HCO3- to maintain pH.
- Light cells respond to ADH to permit H2O movement down the conc. gradient.
-Each type has a cilium for mechanosensitivity.
What are ducts of Bellini aka papillary ducts?
When collecting ducts join = papillary ducts
What cells make up the juxtaglomerular apparatus and what do they do?
- Juxtaglomerular cells monitor BP and can release renin.
2. Macula densa cells monitor blood chemistry.
What structures form the juxtaglomerular apparatus?
Where the renal corpuscle, DCT, and afferent arteriole all come into close contact in the cortex.
What type of cells are JG cells?
Smooth muscle.
Describe the renin/angiotensin pathway.
Low BP –> renin –> cleaves angiotensinogen –> angiotensin I –> angiotensin I cleavage by ACE from the lungs or endothelial cells –> angiotensin II (vasoconstrictor) –> aldosterone release from adrenal –> DCT increases sodium resorption
How do macula densa cells participate in renin release?
They sense low sodium in the DCT and tell JG cells to make renin.
What are calyces?
Where the urine is dumped from the papillary ducts of the renal pyramids.
What type of epithelium is found in the calyces, ureter, and urinary bladder?
Transitional epithelium
Describe the muscle layers of the ureter.
2, sometimes 3 layers.
Inner is LONGITUDINAL
Outer is CIRCULAR
3rd (outermost) layer when present: LONGITUDINAL
Describe the bladder wall.
Transitional epithelium, mucosal wall with unorganized layers of smooth muscle, no distinct muscularis mucosae.
What type of epithelium is in the tubules? Collecting duct?
Simple cuboidal in tubules.
Simple columnar in collecting duct.
Do peritubular capillary cells make EPO?
Yes
