Histology Final

Front 1

Urinary System Components

Back 1

- kidneys
- ureters
- urethra

Front 2

Urinary System Function

Back 2

- 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)

Front 3

Kidney Structure

Back 3

- 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)

Front 4

Nephron

Back 4

- 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

Front 5

Nephron Function

Back 5

- 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

Front 6

Renal Corpuscle

Back 6

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

Front 7

Glomerulus- visceral layer

Back 7

- 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

Front 8

Glomerulus- podocyte filtration barrier

Back 8

*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)

Front 9

Mesangial cells

Back 9

*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

Front 10

Parietal Layer

Back 10

-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

Front 11

Proximal Convoluted Tubule

Back 11

- 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

Front 12

Three Nephron Types

Back 12

- 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.

Front 13

Loop of Henle

Back 13

- 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

Front 14

Thin Descending v. Ascending Loops

Back 14

Descending:
- isosmotic filtrate
- water permeable
- no active transport

Ascending:
- hypoosmotic filtrate
- water impermeable
- Cl diffusion (Na and K follow)

Front 15

Thick Ascending Loop

Back 15

- 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

Front 16

Distal Convoluted Tubule

Back 16

- 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

Front 17

Juxtaglomerular Apparatus

Back 17

- 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.

Front 18

Collecting tubules and ducts

Back 18

*Cuboidal/columnar
*Selectively water permeable
*minimal lateral interdigitation

- it is more of a passive transport here

Front 19

Urothelium

Back 19

*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)

Front 20

Underlying layers

Back 20

*Lamina propria
- dense collagenous

*NO muscularis mucosa
*NO submucosa

*Muscularis:
- longitudinal
- circular

Front 21

Ureter

Back 21

*Transitional epithelium
*Smooth muscle
- inner longitudinal
- middle circular layer
- outer longitudinal (varies)
*adventitia

Front 22

Urinary Bladder

Back 22

*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)