Renal structure

Question 1

Draw the structure of the kidney

Answer 1

Cortex, Medulla, papilla, cortex

Question 2

What does each nephron consist of?

Answer 2

a renal corpuscle and a renal tubule

Question 3

Name the two types of nephron and their differences

Answer 3

1) Cortical nephron.
Renal corpudcle is further into the cortex.
Henle’s loops do not extend deep into the medulla (sometime they do not have them)
2) Juxtamedullary - about 15% of all nephrons
Renal corpuscle sits near the medullally-cortical junction.
Henle’s loops extend deep into the medulla. (These are responsible for the reabsorption of water by generating an osmotic gradient)
Also have long capillaries that loop deeply into medulla

Question 4

What is the renal tubule?

Answer 4

A narrow hollow cylinder made of a single layer of epithelial cells resting on basement membrane. These epithelial cells differ in structure and function along the tubule.

Question 5

Name the different sections of the nephron

Answer 5

1. Renal corpuscle -glomerus -bowman’s space
2. Proximal tubule - proximal convoluted tubule, proximal straight tubule
3. Loop of Henle
   - Descending limb
   - Thin segment of ascending limb
   - Thick segment of ascending limb
4. Distal convoluted tube
5. Collecting duct tubule
   - Cortical collecting duct
   - Medullary collecting duct

Question 6

What constitutes a renal corpuscle?

Answer 6

Bowman’s capsule and glomerulus

Question 7

How much plasma filters into Bowman’s capsule from the glomerulus?

• 30%
• 70%
• 20%
• 90%

Answer 7

About 20%, the remaining blood leaves via the efferent arterioles

Question 8

Name the 3 layers of the filtration barrier separating Bowman’s space from the glomerulus

Answer 8

1. Single-celled capillary endothelium of glomerulus
2. Non-cellular proteinaceous layer of basement membrane
3. Single-celled epithelia of Bowman’s capsule. These are called podocytes.

Question 9

Name the 2 sets of capillaries

Answer 9

1. Glomerular capillaries

2. Peritubular capillaries (along length of tubular)

Question 10

Name the 2 sets of arterioles

Answer 10

1. Afferent arterioles
2. Efferent arterioles
   Blood enters glomerulus through afferent arteriole and leaves via efferent arterioles

Question 11

What is the macula densa?

Answer 11

A patch of cells on ascending limb of each loop of henle

Question 12

Where are the juxtaglomerular cells located?

Answer 12

On the wall of the afferent arteriole, these are secrete renin into the blood

Question 13

What is the juxtaglomerular apparatus?

Answer 13

The combination of macula densa and juxtaglomerular cells

Question 14

What are the two processes of reabsorption in the tubules

Answer 14

1. Diffusion across tight junctions

2. Mediated transport (often coupled to Na+)

Question 15

What are the three muscles of the bladder?
Are they smooth/skeletal muscle?
Does parasym or sym cause contraction?

Answer 15

1. Detrusor muscle
   -Smooth muscle
   -Parasym (rest and digest = stimulated during urination)
2. Internal urethral sphincter
   -Smooth muscle
   -Sympathetic (Fight or flight = stimulated during filling)
3. External urethral sphincter
   -Skeletal muscle
   Stimulated during filling

Question 16

Explain the process of micturition.

From the filling of the bladder to the opening on both spincters.

Answer 16

1. As the bladder fills with urine the pressure increases
2. This stimulates stretch receptors in the bladder wall
3. The afferent neurons from these receptors enter the spinal cord and stimulate parasympathetic neurons
4. This causes the detrusor muscle to contract
5. The change in bladder shape pulls the internal urethral sphincter to open
6. Simultaneously the afferent input from the stretch receptors reflexively inhibits the sympathetic neurons to the external urethral spincter causing to relax and open
7. Both spincters are now open and the contraction of the detrusor muscle can now proudce urination