Lecture 29

Question 1

What is the Nephron?

Answer 1

the microscopic functional unit of the kidney, responsible for urine formation.

Question 2

What are the different types of nephron?

Answer 2

Cortical nephrons which is the most common, found mainly in the cortex. Juxtamedullary
nephrons which extend deep into the medulla and are important for the formation of concentrated urine.

Question 3

What are the functions of the nephron?

Answer 3

• Selectively filter blood
• Return to blood anything to
be kept
• Carry waste away for
storage & expulsion

Question 4

What is the nephron composed of?

Answer 4

A glomerular capsule
Renal Tubules
A collecting duct

Question 5

What is each nephron associated with?

Answer 5

A glomerulus and peritubular capillaries.

Question 6

Structure of Glomerular capillaries?

Answer 6

Thin walled single layer of fenestrated endothelial cells.

Question 7

Features of Glomerular capillaries?

Answer 7

Specialised for filtration
Fed and drained by arterioles
blood pressure is tightly regulated

Question 8

Features of peritubular capillaries?

Answer 8

Specialised for absorption
Wrap around renal tubules
Receives filtered blood from glomerulus via efferent
arterioles
Receives reabsorbed filtrate from nephron
Some non-filtered solutes that need to be excreted can pass from here into nephron

Question 9

What are Vasa Recta?

Answer 9

Extensions that follow loops of Henle deep into the medulla
Only found with juxtamedullary
nephrons

Question 10

What is a renal corpuscle?

Answer 10

Glomerulus enclosed by the Glomerular
capsule
Where capillary and nephron meet
Site of filtration barrier

Question 11

What are the layers of the Glomerular capsule?

Answer 11

Outer parietal layer of simple squamous epithelial cells and inner visceral layer of podocytes.

Question 12

What is the capsular space?

Answer 12

Space between the parietal and visceral layer that receives filtrate.

Question 13

Features of podocytes?

Answer 13

Surround glomerular capillaires
Very branched and very specialised epithelium
Branch from intertwining pedicels
Filtration slits form between pedicels
Filtered blood goes through these slits and enter capsular space.

Question 14

What is the filtration barrier?

Answer 14

blood-urine barrier/glomerular capsular membrane

Lies between blood and capsular space

Question 15

Role of filtration barrier?

Answer 15

Allows free passage of water and small molecules
• Restricts passage of most proteins
• RBCs are not filtered into nephron

Question 16

What are the layers of the filtration barrier?

Answer 16

– Fenestrated endothelium of glomerular capillary
– Fused basement membrane
– Filtration slits between the pedicels of the podocytes

Question 17

What happens after filtration?

Answer 17

Urine is excreted.
The remainder of filtered fluid is reabsorbed
What wasn’t filtered is secreted into the nephron.

Question 18

Purpose of the Proximal convoluted Tubule

Answer 18

Bulk reabsorption.

Question 19

Structure of the Proximal convoluted Tubule?

Answer 19

Cuboidal epithelial cells
Dense microvilli (brush border) on luminal membrane
Highly folded basolateral membrane
Many mitochondria for active transport
Leaky epithelium

Question 20

Where is the nephron loop located?

Answer 20

Loops down into the medulla.(Length is important in

production of dilute/concentrated urine) Surrounded by vasa recta (juxtamedullary nephrons only)

Question 21

Structure of the nephron loop?

Answer 21

! Thick descending limb
! Similar to PCT structure
! Thin descending limb
! Simple squamous epithelium
! Thin ascending limb
! Simple squamous epithelium
! Thick ascending limb
! Similar to DCT structure

Question 22

How is the Distal convoluted tubule different from the PCT?

Answer 22

For fine tuning… cuboidal epithelium but thinner than PCT.

Question 23

Structure of DCT?

Answer 23

! Few microvilli =no brush border
! Fewer mitochondria
! Reabsorption influenced mainly by Aldosterone

Question 24

ROle of the collecting duct?

Answer 24

Fine tuning.

Filtrate from several DCT drain into collecting duct which empty at papilla.

Question 25

Structure of Collecting duct?

Answer 25

! Wall of simple
cuboidal epithelium
! Principal cells
! Reabsorption
! Intercalated cells
! Acid/Base balance

Question 26

What influences reabsorption?

Answer 26

ADH and Aldosterone

Question 27

What is the Juxtaglomerular apparatu?

Answer 27

A specialised zone in every nephron, Located where DCT lies against afferent arteriole

Question 28

What specialized cells does the JGA contain?

Answer 28

DCT:
Macula densa cells.
Chemoreceptors. Detect sodium levels

Afferent arteriole:
Juxtaglomerular cells.
Mechanoreceptors. Detect
blood pressure

Question 29

Function of JGA?

Answer 29

Controls glomerular filtration rate, ensuring system working at full capacity and Stabilises blood pressure