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22 Cards in this Set

  • Front
  • Back
Urinary System Components
- kidneys
- ureters
- urethra
Urinary System Function
- filtration
- active absorption
- passive absorption
- secretion:
erythropoietin (glycoprotein hormone that regulates blood oxygen concentration)
renin (an enzyme involved in control of blood pressure and blood volume)
Kidney Structure
- hilum (major blood vessels coming in here, ureter coming out here)
- capsule (of CT surrounding it)
- renal pelvis- the expanded funnel-shaped organ of the ureter thru which the renal vessels and nerves pass. (major and minor calyx)
- cortex (outer)
-medulla (inner)
Nephron
- its the functional unit of the kidney
Components:
*renal corpuscle (glomerulus + bowman's capsule)
*proximal convoluted tubule (from bowman's capsule)
*loop of henle (in medulla)
*distal convoluted tubule (connects to collecting tubule)
*collecting tubule and ducts
Nephron Function
- both active and passive transport take place (bicarb is passively transported while NaCl, nutrients and H+ have active reabsorption)
- descending loop of henle pulls out more water (so substance becomes more concentrated. The loop is impermeable to salt (hyperosmotic))
- ascending loop of henle- NaCl is pulled out
- animals in the desert have longer loops of henle to retain more H2O
Renal Corpuscle
Consists of:
* Glomerulus- a tuft of capillaries (in loops)

*Bowman's Capsule- a double-layered epithelial cup
- Visceral (immediately surrounds capsule)
- Parietal (outer layer)

*Vascular Pole- the site where the afferent and efferent arterioles penetrate and exit from the parietal layer of the Bowman's Capsule

*Urinary Pole- opposite from the vascular pole on the renal corpuscle; this is where the proximal convoluted tubule begins
Glomerulus- visceral layer
- endothelium capillaries (fenestrated capillaries)
- continuous basal lamina
- podocytes present (have lots of feet and primary and secondary processes)
- filtration slits- where things can get thru (~25 nm wide); in between secondary processes
Glomerulus- podocyte filtration barrier
*Lamina rara- anionically charged (keeps cations from passing through a barrier)

*Lamina densa- thicker layer with collagen and laminin associated (acts as a physical barrier)
Mesangial cells
*Contractile cells (so they may play a role in regulating glomerular blood flow)
*Receptors
- vasoconstrictor
- vasodilator
*Cleans GBM (glomerulus basement membrane)
*Other Functions:
- structural support
- ECM
- Disposal
Parietal Layer
-simple squamous cells
- it is the outside layer of the bowman's capsule
- when there's a transition to simple cuboidal that means that it is turning into the proximal tubule
Proximal Convoluted Tubule
- recovers glucose and amino acids
- the proximal convoluted tubule is the initial and major site of reabsorption
- 85% of NaCl and H2O is recovered here
- all of these are recovered by active transport
- apical surface
- lateral plicae (folds on the sides and base also)
- basal striations (consisting of elongate mitochondria concentrated in the basal processes and orientated vertically to the basal surface
- canaliculi- small depressions from the plasma membrane downward
Three Nephron Types
- Cortical Nephrons- have their renal corpuscle located in the outer part of the cortex. They have short loops of henle that extend only into the outer medulla.

- Juxtamedullary nephrons- their renal corpuscles occur in proximity to the base of a medullary pyramid. They have long loops of henle.

- Midcortical nephrons- have their renal corpuscles in the midregion of the cortex. Their loops of henle are of intermediate length.
Loop of Henle
- thick portion- cells are cuboidal in shape
- thin portion- cells are stratified squamous
- so there is a change in cell type throughout the loop of henle
Thin Descending v. Ascending Loops
Descending:
- isosmotic filtrate
- water permeable
- no active transport

Ascending:
- hypoosmotic filtrate
- water impermeable
- Cl diffusion (Na and K follow)
Thick Ascending Loop
- simple cuboidal cells
- continuation of distal convoluted tubule (?)
- active transport of salt out of fluid
- there is a significant movement of ions without the movement of water through the wall of the thick ascending loop, resulting in separation of water from its solutes
Distal Convoluted Tubule
- simple cuboidal epithelium

*Varies from proximal convoluted tubule (because not as much exchange occurs here):
- no brush border
- no apical canaliculi
- smaller cell size

*Functions:
- reabsorption of Na and secretion of K
- reabsorption of bicarbonate ion
- conversion of ammonia to ammonium ions
Juxtaglomerular Apparatus
- it includes the macula densa, the juxtaglomerular cells, and the extraglomerular mesangial cells

*Macula densa- in wall of distal tubule (they are a collection of columnar cells that help sense the ion balance and regulate it)

*Juxtaglomerular cells- surround afferent arterioles; they are modified smooth muscle cells that regulate amount of blood flow

*Renin-angiotensin-aldosterone system- regulation of ion balance in the body (plays an important role in sodium homeostasis and renal hemodynamics); the aldosterone (end product) acts on collecting ducts to increase reabsorption of Na and concomitant reabsorption of water, thereby raising blood volume and pressure.
Collecting tubules and ducts
*Cuboidal/columnar
*Selectively water permeable
*minimal lateral interdigitation

- it is more of a passive transport here
Urothelium
*transitional epithelium (stratified, impermeable to salts and water. Become thicker as the tube goes down. Can expand and contract in size (does this by pockets)
*Plaques- linked to actin cytoskeleton (they are areas that appear to be more rigit and thicker than the rest of the apical plasma membrane)
Underlying layers
*Lamina propria
- dense collagenous

*NO muscularis mucosa
*NO submucosa

*Muscularis:
- longitudinal
- circular
Ureter
*Transitional epithelium
*Smooth muscle
- inner longitudinal
- middle circular layer
- outer longitudinal (varies)
*adventitia
Urinary Bladder
*Transitional epithelium

*Detrusor muscle (allow bladder to contract; in walls of bladder)

*Internal urethral sphincter (a ringlike arrangement of muscle around the opening of the urethra)