Histology and embryology

Question 1

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

Answer 1

• maintain water and electrolyte homeostasis, body fluid osmolarity and acid base balance
• excrete toxic metabolic waste products (mainly urea and creatinine)
• act as an endocrine gland, producing renin and erythropoietin

Question 2

What is the hilum of the kidney?

Answer 2

• site of entry of renal artery

- exit of renal vein and ureter

Question 3

What is considered a lobe of the kidney?

Answer 3

Each medullary pyramid and its associated cortical tissue

Question 4

Name the two layers of the capsule

Answer 4

• outer fibrous layer

- inner cellular layer

Question 5

The glomeruli is only present within what?

Answer 5

The cortex

Question 6

What is the basic functional unit of the kidney?

Answer 6

The nephron

Question 7

The nephron is composed of what?

Answer 7

The renal corpuscle and renal tubules

Question 8

What is the principle role of the renal corpuscle?

Answer 8

The production and collection of glomerular filtrate

Question 9

What is the principle role of the proximal convulated tubule?

Answer 9

Reabsorption of water, proteins, amino acids, carbohydrates and glucose

Question 10

What is the principle role of the loop of henle?

Answer 10

The creation of hyperosmotic environment in medulla

Question 11

What is the principle role of the distal convulated tubule?

Answer 11

Acid-base and water balance (absorption of water, Na and bicarbonate, excretion of K and H ions)

Question 12

The renal corpuscle is formed from what?

Answer 12

Formed from a tuft of capillaries called the glomerulus and the cup of simple squamous epithelium at the blind end of the nephron which the capillaries invaginate into (called the bowmans capsule)

Question 13

Describe the two cell layers which separate the blood from the glomerular filtrate

Answer 13

• the capillary endothelium and a specialised epithelium which lies on top of the glomerular capillaries
• these epithelial cells are called podocytes
• the endothelium is fenestrated with pores 70-90nm in diameter, and the podocytes have interdigitating cell processes forming filtration slits about 25nm wide
• between these two layers is a thicker than usual (0.3 micrometres rather than 0.05) basal lamina

Question 14

Scattered mesangial cells produce what?

Answer 14

• produce a connective tissue core called the mesangium

- these cells have several functions, including support and removal of debris

Question 15

Name the three components of the glomerular filter

Answer 15

• the fenestrated endothelium of the capillary wall
• the thick basement membrane (shared by endothelium and podocyte)
• the filtration slits between pedicles

Question 16

Describe the histology of a proximal convulated tubule cell

Answer 16

• simple cuboidal cells
• very florid apical brush border which increases surface area
• interdigitations of basal membranes which increases surface area

Question 17

The medulla is made up of what?

Answer 17

• parallel tubules
• the loops of henle
• the collecting ducts
• as well as a looping vascular network

Question 18

Describe the portions of the loop of henle

Answer 18

• initial portion is a thick descending limb
• thin descending limb (hair pin turn)
• thin ascending limb
• then ascending limb (straight portion of the distal tubule which then becomes the distal convulated tubule)

Question 19

The thick limbs are lined by what?

Answer 19

Simple cuboidal epithelium

Question 20

The thin limbs are lined by what?

Answer 20

Simple squamous epithelium

Question 21

Reabsorption of Na+ in the distal convulated tubule is controlled by what?

Answer 21

Aldosterone

Question 22

What is the role of the collecting tubules and collecting ducts?

Answer 22

Reabsorption of water under the control of ADH

Question 23

What increases the permeability of the collecting duct to water?

Answer 23

ADH (vasopressin)

Question 24

Describe the flow of urine

Answer 24

• the urine produced at the renal papilla is collected into the minor calyx
• flows into major calyx
• then ureter
• and then into the bladder - during voiding it flows into the urethra and exits the body

Question 25

The lumen of the ureter is lined by what?

Answer 25

Transitional epithelium, which is backed by a lamina propria of connective tissue and combined these form the mucosa