Urinary System

Question 1

Metanephric Kidney

Answer 1

• mature kidney in humans
• paired structures
• filters blood
• Artery and vein enter into the kidney at the pelvis
• divides into calyces
• pyramids at the base of the calyx
• ureter exits the kidney

Question 2

The Renal Nephron

Answer 2

Renal Corpuscle
- glomerulus and capsule that filters blood

Proximal tubule
- convoluted tubule and a straight short duct

Loop of Henle
- Thick descending, thin descending, thin ascending and thick ascending duct

Distal Tubule
- thick ascending duct and thick convoluted tubule

Collecting duct

Question 3

Renal Corpuslce

Answer 3

Capsule is parietal layer around the outside

Inside is visceral component

• glomerulus
• consisting of highly branched capillaries
• surrounded by cells that facilitate the filtration of the blood

Question 4

Macula Densa

Answer 4

• highly compacted cells of distal convoluted tubule
• immediately adjacent to the arteriole that goes into the renal corpuslce
• cause juxtaglomerular cells to secrete renin causing an increase in blood flow and blood pressure of the arterioles feeding into the glomerulus

Feedback Loop
- the fluids have gone all the way through to the distal convoluted tubule, which give feedback on the efficiency of the filtration process to the blood vessels which are newly feeding into the renal corpuscle

Question 5

Glomerulus

Answer 5

• visceral component of the renal corpuscle
• capillaries are covered by epithelial branches of podocytes
• podocytes further branch to form pedicles (filtration slits)
• facilitates filtration of the blood through the structures into the urinary space
• forms primitive filtrate
• filtrate exits through the urinary pole

Question 6

Mesangial Cells

Answer 6

• play a role in cleaning up the basement membrane surrounding the capillaries
• with constant filtering, you get compounds that accumulate on the capillaries, clogging up the basement membrane

Question 7

Filtration Membrane

Answer 7

• Fenestrated capillary of kidney does not have a diaphragm
• Sometimes called pseudofenestrated
• Does have a very thick basement membrane which acts as filter of the blood

Podoctyes branch to form pedicles
- There is a slit diaphragm between adjacent pedicles of podocytes

• Filtrate enters into urinary space = Bowman’s space
• Filtrate contains water and very small compounds, many of which will be reabsorbed by tubular component of the nephron

Question 8

Reabsorption through the tubules

Answer 8

Proximal convoluted tubule
- reabsorbs most of the water and some ions

Descending Thick Tubule

• similar to proximal
• reabsorbs another 15% of water

Descending Thin
- Passively reabsorbs water

Ascending Thin
- Reabsorbs NaCl, but not water

Ascending Thick

• Responsive to aldosterone
• Reabsorbs Na

Distal Convoluted tubule

• responsive to aldosterone
• reabsorbs Na and water

Collecting Ducts

• responsive to vasopressin (ADH) from pituitary
• reabsorbs water back into the body

No water is absorbed on the ascending limb

Question 9

Vasa Recta

Answer 9

• extensive capillaries around the loop of henle

- important for reabsorbing most of the water and ions

Question 10

Cortex and Medulla

Answer 10

Cortex

• on the outer surface
• contains only renal corpuscles

Medulla

• only contains tubules
• no renal corpuscles in the medulla
• outer stripe
• Inner stripe
• Inner zone

Question 11

Outer Stripe

Answer 11

• contains only thick tubules
• Both ascending and descending
• contains collecting ducts
• proximal convoluted tubule has a prominent brush border

Question 12

Inner Stripe

Answer 12

• Ascending thick
• Descending thin (or ascending thin?)
• Collecting ducts

Question 13

Inner Zone

Answer 13

• A lot of collecting ducts

- Only thin tubules

Question 14

Renal Papilla

Answer 14

• all filtrate collects to the renal papilla which goes into calyces and then drain into the ureter

Question 15

Ureters

Answer 15

• lined by transitional epithelium = urothelium

Contains:

• transitional mucosa
• Lamina propria
• Muscularis
• Adventitia
• Binucleated cells

Question 16

Bladder

Answer 16

• continuation of ureters
• Transitional epithelium
• Epithelium is thrown into folds when empty
• When full, the epithelium will stretch out
• Also contains lamina propria
• 3 layers of muscle (inner, middle and outer)
• contains adventitia