Urinary System

Question 1

What are the three basic functions of the kidney and urinary tract?

Answer 1

1) Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
2) Excrete toxic metabolic waste products (mainly urea and creatinine) 1 and 2 achieved by production, storage and voiding of urine
3) Act as an endocrine gland, producing renin and erythropoietin

Question 2

Basic Kidney Structure

• Capsule

Answer 2

• Thin but strong. Dense collagen fibres.

Question 3

Calyces

• Pelvis

Answer 3

• Pelvis expands from ureter to form calyces

Question 4

What is this?

Answer 4

Nephron

Question 5

Renal Papilla

Answer 5

Question 6

Nephron

What is it?

What is it composed of?

Answer 6

The basic functional unit of the kidney.

Composed of the renal corpuscle and renal tubes

Question 7

Renal Corpuscle

Formed from

Answer 7

A tuft of capillaries (glomerulus) and the cup of simple squamous epithelium at the blind end of the nephron, which the capillaries invaginate into (bowmans capsule)

Question 8

Renal Corpuscle

Vascular supply

Answer 8

Supplied by an afferent arteriole and drained by an efferent arteriole

Question 9

Renal Corpuscle

Podocytes

Answer 9

Specialised epithelium lying on top of glomelular capillaries. Have interdigitating cell processes which form filtration slits, and form one of the two cell layers separating the blood from the glomelular filtrate. The other layer is capillary endothelium

Question 10

Renal Corpuscle

Basal lamina

Answer 10

Between the two layers separating glomelular filtrate and blood. Thicker than usual and made up of a feltwork of GAG’s

Question 11

Renal Corpuscle

Mesangial cells

Answer 11

Sit within space between endothelial cells and the basal lamina which surrounds the entire complex, and eats the stuff which gets stuck in the pores. Also control filatration rate.

Question 12

Proximal Convoluted Tubule (PCT)

Role

Microvili

Answer 12

Reabsorbtion of water, proteins, amino acids, carbohydrates and glucose. Most stuff is put out of the body but the good stuff brought back in from glomelular filtrate.

Are the hallmark of proximal convoluted tubules

Question 13

Loop of Henle

Function

Answer 13

Creates a hypertonic environment in the medulla by changing the extratubular environment

Question 14

Loop of Henle - Vasa Recta

• Why have it?

Answer 14

Blood vessels moving normally to the medulla would flush away all the salts, destroying the osmotic gradient. This has been solved by loops of blood vessels (vasa recta) dipping into the medulla and returning to the cortex.

This means that the salt will go back into the area around the loop of henle on the way back up

Question 15

What happens in the medulla?

Answer 15

Permeabilities change in the loop of henle as it dives down and comes back up.Thin limb goes down and thick goes up. Thick is not permeable to water but thin is permeable to almost everything.This means there is a very high osmotic pressure created in the medulla.

Question 16

Structures in the medulla

Answer 16

Thick limb has lots of mitochondria

Question 17

Distal Convoluted Tubule

Function

Answer 17

Acid-base and water balance (absorption of water, Na, and bicarbonate, excretion of K and H ions. Fine tunes the acid-base and water balance in the system.

Question 18

Collecting duct

Answer 18

Urine dripped off from the end of it and into the calyx. Controlled reabsorption of water under the control of ADH.ADH can cause the duct to vary the permeability to water, meaning that you can regulate the amount of water being put out.

Question 19

Juxtaglomerular Apparatus

Macula densa

Answer 19

On the side of the DCT nearest the afferent arteriole, the cells of the DCT are taller. Function believed to be in sensing sodium content in the DCT.

Question 20

Juxtaglomerular Apparatus

Juxtaglomerular cells

Answer 20

Modified smooth mucscle cells in wall of the afferent arteriole. These cells contain/excrete renin, initiating the renin-angiotensis system

Question 21

Juxtaglomerular Apparatus

Extraglomerular mesangial cells/lacis cells

Answer 21

Modified mesangial cells which extend outside the renal corpuscle. They contact the macula densa and are continuous with the mesangial cells inside the renal corpuscle. They are thought to function in signalling that alters glomerular filtration, but the exact function is unknown.

Question 22

Urothelium (transitional epithelium)

Answer 22

Lining of the conducting parts of the urinary tract. Stratified and found in 3-6 cell layers. Umbrella domed cells at the surface. This gives a very highly impermeable and inflexible membrane. Layers of smooth muscle below the epithelium.

Question 23

What is this?

Answer 23

Urinary bladder

Question 24

What is this?

Answer 24

Renal papilla

Question 25

What is this?

Answer 25

Renal corpuscle

Question 26

What is this?

Answer 26

Proximal convoluted tubules

Question 27

What is this?

Answer 27

Structures in the medulla

Question 28

What is this?

Answer 28

Distal convoluted tubules

Question 29

What is this?

Answer 29

Collecting ducts

Question 30

What is this?

Answer 30

Transitional epithelium

Question 31

Basic Kidney Structure

• Major regions

Answer 31

• Cortex and medulla

Question 32

Basic Kidney Structure

• Medulla

Answer 32

• Divided into layers. Medullary pyramids (10-18/kidney) pointing towards hilum (papillae) ending on the minor calyces

Question 33

Calyces

• Urine

Answer 33

• Drips off from papilla into minor calyx

Question 34

Calyces

• Medullary rays

Answer 34

• Stripes heading away from medullary pyramids and into cortex

Question 35

Distal Convoluted Tubule

Defining features

Answer 35

Lack of microvili and no big hairy brush border like the proximal