5.4 Functional Anatomy of the Nephron and its Blood Supply

Question 1

Renal Functions

Answer 1

1. Regulate body fluid volume and osmolarity, electrolyte balance and acid-base balance
2. Remove metabolic wastes ad foreign substances
3. Endocrine

Question 2

Renal corpuscle circulation

Answer 2

Afferent arteriole
glomerular capillaries
efferent arterioles
peritubular capillaries

Question 3

Parts and function of nephron

Answer 3

1. Renal corpuscle: filtration of blood

2. Renal tubule: reabsorption and secretion

Question 4

What are the parts of the Cortical nephrons

Answer 4

• short loops of henle to the border of outer and inner medulla
• Short thin descending limb
• No thick ascending limb

Question 5

Juxtamedullary nephrons

Answer 5

• Corpuscles located near corticomedullary junction
• Long loops of henle with thin limbs reaching inner medulla
• Accompanied by hair-pin shaped vasa recta

Question 6

Filtration barrier layers

Answer 6

1. Endothelial cells of capillaries - fenestrations
2. Glomerular basement membrane
3. Podocytes

Question 7

Structure and Function of Endothelial cells of capillaries

Answer 7

Contain fenestrations which only stop blood cells from passing through

Question 8

Layers and function of Glomerular basement membrane

Answer 8

Lamina rara interna, lamina densa, lamina rara externa
Located between the endothelial cells and podocyte foot processes
Restricts solutes > 1 kDa

Question 9

what are Podocytes

Answer 9

Foot processes interdigitate with the basement membrane, with filtration slits between them. Negatively charged glycoproteins cover the podocytes and filtration slits which favours filtration of positively charged molecules

Question 10

Structure and function of Mesangial cells

Answer 10

Located between the capillaries and adhere to the endothelial cells. Enveloped by the basement membrane.
Functions: contract to regulate glomerular blood flow, remove molecules trapped in basement membrane and to support the glomerulus

Question 11

Gomerular (Bowmans) capsule layers

Answer 11

1. Visceral layer: podocytes attach to capillaries with pedicles
2. Parietal layer: squamous epithelium
3. Urinary space

Question 12

Renal corpuscle

Answer 12

Bowmans capsule + glomerulus

Question 13

Macula densa function

Answer 13

Act as local feedback, contact between the thick ascending limb and the glomerulus.
Increasinf NaCl and fluid at macula densa leads to release of paracrine agents (ATP) leading to contraction of afferent arterioles and a decrease in filtration rate

Question 14

Juxtaglomerular (granular) cells

Answer 14

Modified smooth muscle cells of afferent arterioles that are the site of production, storage and release of renin

Question 15

How does a decrease in BP act on Juxtaglomerular cells

Answer 15

Decrease BP leads to activation of barorecepors on afferent arterioles, the JG cells secrete renin which will cleave circulating angiotensinogen which prevents the angiotensin 1 being converted into ANG2 leading to an increase in BP and increased aldosterone release

Question 16

Proximal convoluted tubule

Location, microscopic structure

Answer 16

Located in renal cortex
Simple cuboidal epithelium
Brush border with microvilli and a huge number of mitochondria

Question 17

Distal convoluted tubule

Location, microscopic structure

Answer 17

Located in renal cortex
Simple cuboidal epithelium
No microvilli or brush border
abundant mitochondria near base

Question 18

Loop of henle

Location, microscopic structure

Answer 18

Located mainly in the renal medulla
Cuboidal epithelium (thick limbs)
Squamous epithelium (thin limbs)
Wide lumen

Question 19

Functions of specific parts of renal tubule - proximal and distal convoluted and loop of henle

Answer 19

PCT: resorption of the bulk of the filtered fluid back into circulation

Loop of Henle: creating osmotic gradients in the medulla by pumping NaCl into the interstitium of the medulla to concentrate urine

DCT: only absorbs small amount of filtrate but is the site or fine control of salt and water reabsorption in response to hormones

Question 20

What is the function of the fenestrations of endothelial cells?

Answer 20

ensure that the formed blood cells cant pass through - first layer of filtration

Question 21

In which part of the convoluted tubules would you find a brushborder with microvilli?

Answer 21

Proximal