2. Functional Histology of the Urinary Tract

Question 1

What is the gross anatomy of the kidney?

Answer 1

It is surrounded by a fibrous capsule and is organised into two layers - the outer cortex and inner medulla.

Question 2

What does the renal cortex contain?

Answer 2

Renal corpuscles and medulla tubules.

Question 3

What is the renal blood supply?

Answer 3

From the renal artery which is a branch off the abdominal aorta.

Question 4

What are the main components of the nephron?

Answer 4

Renal corpuscle (glomerulus and Bowman’s capsule), proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

Question 5

What are the two poles of the renal corpuscle?

Answer 5

Vascular pole and urinary pole.

Question 6

What is the vascular pole of the renal corpuscle?

Answer 6

Afferent/efferent arterioles, glomerulus.

Question 7

What is the urinary pole of the renal corpuscle?

Answer 7

Bowman’s capsule.

Question 8

What is the renal tubule derived from?

Answer 8

Ureteric bud.

Question 9

Briefly, describe how the Bowman’s capsule develops.

Answer 9

Renal tubule derived from ureteric bud which envelops the growing glomerulus, resulting in a double-layered cover - Bowman’s capsule.

Question 10

What makes up the filtration barrier in the kidney?

Answer 10

Capillary endothelium, visceral layer of Bowman’s capsule - podocytes.

Question 11

What makes the capillary endothelium in the kidneys so leaky?

Answer 11

They are fenestrated and the podocytes invest in it, making filtration slits.

Question 12

What does the parietal layer of the Bowman’s capsule make up?

Answer 12

A funnel to collect ultrafiltrate to drain into the PCT and urinary pole.

Question 13

Where does reabsorption begin in the kidneys?

Answer 13

Proximal convoluted tubule.

Question 14

What lines the proximal convoluted tubule?

Answer 14

Simple cuboidal epithelium with a pronounced brush border membrane.

Question 15

What are the four parts of the loop of Henle?

Answer 15

Pars recta, thin descending limb, thin ascending limb, thick ascending limb.

Question 16

What lines the thin limb of the loop of Henle?

Answer 16

Simple squamous epithelium.

Question 17

How does the thin limb of the loop of Henle appear histologically?

Answer 17

It looks like a small capillary but without any red blood cells, also no brush border.

Question 18

Where is the thick ascending limp of the loop of Henle best seen?

Answer 18

In the medulla, interspersed with thin limbs, vasa recta, and collecting duct.

Question 19

What lines the thick ascending limb?

Answer 19

Simple cuboidal epithelium.

Question 20

How can the thick ascending limb be differentiated from the proximal convoluted tubule?

Answer 20

It has no brush border.

Question 21

What does the distal convoluted tubule contain lots of?

Answer 21

Mitochondria.

Question 22

How does the distal convoluted tubule differ from the proximal convoluted tubule?

Answer 22

It has no brush border and a larger lumen.

Question 23

What does the juxtaglomerular apparatus consist of?

Answer 23

Macula densa, juxtaglomerular cells, and extraglomerula mesangial cells.

Question 24

How do macula densa cells of the juxtaglomerula apparatus appear histologically?

Answer 24

They are the dense staining region of the distal convoluted tubule.

Question 25

What are the juxtaglomerular cells?

Answer 25

Cells of afferent arteriole of the glomerulus.

Question 26

What is the collecting duct a continuation of?

Answer 26

The distal convoluted tubule.

Question 27

How does the histological appearance of the collecting duct differ from the thick limbs of Henle’s loop?

Answer 27

Similar but the lumen is larger and tends to be more irregular than circular.

Question 28

What forms the renal pyramids?

Answer 28

Progressively larger ducts merging together and emptying at the renal papilla.

Question 29

What is the ureter?

Answer 29

A tube running from the renal pelvis to the bladder.

Question 30

How many layers of muscle does the ureter have?

Answer 30

Two, but a third appears in the lower third.

Question 31

What lines the ureter?

Answer 31

Transitional epithelium.

Question 32

How many layers of muscle does the bladder have?

Answer 32

Three, like the lower ureter.

Question 33

What lines the urinary bladder?

Answer 33

Transitional epithelia, surrounded by an outer adventitia.

Question 34

What is urothelium?

Answer 34

Stratified epithelium on the surface of the bladder that makes it impermeable.