Urinary System

Question 1

3 functions of 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
3 - act as an endocrine gland, producing renin and erythropoietin

Question 2

What is the kidney capsule continuous with?

What is it made from?

Answer 2

Connective tissue lining the renal sinus

Dense collagen fibres

Question 3

What are medullary rays?

Answer 3

Collections of collecting ducts and the straight segments of convoluted tubules.
Found in the cortex.

Question 4

4 properties of the nephron

Answer 4

1 - basic functional unit of the kidney
2 - composed of renal corpuscle and renal tubules
3 - each human kidney contains 600,000-1million nephrons
4 - total length of a nephron approx 45-65mm

Question 5

Principle role of the renal corpuscle

Answer 5

Production and collection of glomerular filtrate

Question 6

What is the renal corpuscle formed from?

Answer 6

Tuft of capillaries called the glomerulus and the cup of simple squamous epithelium (Bowman’s capsule) at the blind end of the nephron which

Question 7

What is the glomerulus supplied and drained by?

Answer 7

Supplied - afferent arteriole

Drained - efferent arteriole

Question 8

What are podocytes?

Answer 8

Specialised epithelial cells which lie on top of the glomerular capillaries

Question 9

What separates the blood from the glomerular filtrate?

Answer 9

Two cell layers:

• capillary endothelium
• specialised epithelium

Question 10

What is between the two cell layers separating the blood from glomerular filtrate?

Answer 10

Thicker than usual basal lamina made of a feltwork of GAGs

Question 11

What is the mesangium?

Answer 11

A connective tissue core made from scattered mesangial cells.
Functions:
- support
- removal of debris

Question 12

What are the 3 components of the glomerular filter?

Answer 12

1 - fenestrated endothelium of the capillary wall
2 - thick basement membrane
3 - filtration slits between pedicels

Question 13

Principal role of proximal convoluted tubule

Answer 13

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

Question 14

What is quantitiy of products are reabsorbed in the proximal convoluted tubule?

Answer 14

70% of sodium by active transport
70% of water by diffusion
almost ALL glucose and amino acids by cotransport

Question 15

Principle role of the loop of henle

Answer 15

Creation of hypertonic environment in the medulla

Question 16

What is the Vasa Recta?

Answer 16

Thin loops of blood vessels that dip down into the medulla from above then return to the cortex.
(stop salts being carried away in the interstitial environment and maintains high osmotic gradient)

Question 17

What structures are found in the outer medulla?

Answer 17

Collecting ducts
Blood vessels of vasa recta
Thin limb of loop of henle
Proximal and Distal straight tubules

Question 18

Principle role of the distal convoluted tubule

Answer 18

Acid-base and water balance
Absorption of water, Na and bicarbonate
Excretion of K and H ions

Question 19

What does aldosterone hormone do?

Answer 19

Controls the reapsorption of sodium in the DCT

Question 20

Where is it secreted and what controls the secretion of aldosterone?

Answer 20

Secreted by the adrenal cortex

Controlled by the renin-angiotensin system

Question 21

What does aldosterone hormone secretion result in?

Answer 21

Greater reabsorption of sodium and water retention, therefore increases blood pressure.

Question 22

What is the principal role of the collecting duct?

Answer 22

To control reabsorption of water under the control of ADH

Question 23

How does ADH affect the permeability of collecting ducts?

Answer 23

ADH from the posterior pituitary increases permeability to water.
In presence of ADH, permeability is high during the passage through the medulla.
Due to the high salt content in the surrounding tissue, the water passes out through the lumen and CONCENTRATED urine results.

Question 24

What is the juxtaglomerular apparatus?

Answer 24

Specialised region formed when the distal convoluted tubule passes adjacent to the vascular pole of the SAME renal corpuscle that forms part of its own nephron.

Question 25

What are the 3 components of the juxtaglomerular apparatus?

Answer 25

1 - macula densa
2 - juxtaglomerular cells
3 - extraglomerular mesangial cells (lacis cells)

Question 26

Describe the macula densa and its function.

Answer 26

On the side of the distal convoluted tubule nearest the afferent arteriole, where the cells are taller, more crowded and their nuclei are intensely stained.
Believed to sense sodium content of fluid in DCT.

Question 27

Describe the juxtoglomerular cells and their function.

Answer 27

Modified smooth muscle cells in wall of afferent arteriole.

Contain/excrete renin, initiating the renin-angiotensin system.

Question 28

Describe the extraglomerular mesangial cells and their function.

Answer 28

Modified mesangial cells extending outside the renal corpuscle. Contact macula densa and are continuous with mesangial cells inside renal corpuscle.
Alters glomerular filtration.

Question 29

What happens to urine after its produced?

Answer 29

Produced in the renal papilla and is collected into the minor calyx.
Flows into the major calyx, ureter and then to the bladder.
During voiding it flows into the urethra and exits the body.

Question 30

What is transitional epithelium?

Answer 30

Special epithelium lining most conducting parts of urinary tract.

Question 31

Properties of transitional epithelium.

Answer 31

Stratified
Found in 3-6 cell layers
Cells at luminal surface are domed = umbrella cells
Facing lumen, have special, thickened and inflexible membrane

Question 32

What 2 facts describe the special structure of transitional epithelium?

Answer 32

The variability of thickness of cells represent different states of distension.
The special surface structures provide a highly impermeable barrier.

Question 33

Describe the lining of the ureter.

Answer 33

Transitional epithelium backed by a basal lamina of connective tissue then covered by an inner longitudinal and outer circular layer of smooth muscle surrounded by adventitia.

Near the bladder: 3 layers of smooth muscle as another outer longitudinal layer is present.

Question 34

What do the 3 layers of smooth muscle in the ureter form?

Answer 34

Detrusor Muscle

Internal urethral sphincter

Question 35

What lines the female urethra?

Answer 35

Initially lined by transitional epithelium, which becomes stratified squamous as it nears the surface of the body just posterior to clitoris.

Question 36

What does the middle of the female urethra contain?

Answer 36

Includes a sphincter of striated skeletal muscle - the voluntary sphincter.