Kidney Functions I, Filtration, Reabsorption and Secretion

Question 1

Functions of the kidney

Answer 1

Excretion of metabolites

Control of body fluid comp

• volume regulation
• osmoregulation
• pH regulation

Hormone release

Question 2

Location of the kidneys

Answer 2

T12-L3

R lower than L due to liver

Question 3

Name the parts of the nephrons

Answer 3

Renal corpuscle
PCT
PST (M)
Thin desc LOH (M)
Thin asc LOH (M)
Thick asc LOH (M)
Distal CT
CD (M)

Question 4

Name the 2 types of nephron

Answer 4

Cortical

• outer 2/3 in cortex
• short LOH

Juxtamedullary

• inner 1/3 in cortex
• long LOH

Question 5

Name the main structures in the renal corpuscle

Answer 5

Afferent arteriole surrounded by juxtaglomerular cells
Glomerulus in Bowmans capsule
Fenestrated capillaries, BM, podocytes form filtration barrier
Mesangial cells between afferent and efferent arterioles
Macula densa in DCT

Question 6

Name the structures that form the filtration barrier in the glomerulus
Describe their functions

Answer 6

Fenestrated capillary endothelium
-ve BM
Podocytes form filtration barrier
-nephrin anchored to podocytes by podocin allow solutes through

Question 7

Name and describe the functions of the main cells in the JGA

Answer 7

Juxtaglomerular cells
-Renin secreting in afferent arteriole walls

Mesangial cells

• Autoregulation of renal blood flow
• Between afferent, efferent arterioles

Macula densa

• Sensitive to [NaCl] in DCT
• Within ascending LOH

Question 8

Describe the blood supply of the kidney and the nephron

Answer 8

Arcuate arteries => interlobar arteries => afferent arterioles

Peritubular capillaries surround cortical regions

Vasa recta surround LOH in medulla

Question 9

Describe the 2 properties of the glomerular filtrate

Answer 9

Molecular size
-greater size => more likely to be excluded

Charge

• +ve => most likely to be filtered
• -ve => most likely to be excluded

Proteins and protein bound molecules excluded

Question 10

What can cause glomerular damage and what are the consequences

Answer 10

Infection/HTN

Proteinuria
Haemoglobinuria
Haematouria

Question 11

What is the glomerular filtration rate and what are the 3 ways of regulating it

What is the typical GFR

Answer 11

Volume of fluid filtered/min

Starling forces
-Balance between hydrostatic pressure => lumen and oncotic pressure => capillaries

SA of filtration barrier
-mesangial cells/SM contraction => decreased SA and pressure

Permeability
-fenestrated capillaries

GFR = 125ml/min

Question 12

How is the proximal tubule adapted for reabsorption

Answer 12

Brush border

Many mitochondria

Question 13

Describe how

• glucose
• AA
• PO4, SO4
• Urea, Cl, K
• HCO3
• Water is reabsorbed in the PT

Answer 13

Glucose
-SGLUT => GLUT2

AA

• Na contransport => FD
• larger polypeptides endocytose => degraded in lysosomes => FD

PO4, SO4
-Na contransport => FD

Urea, Cl, K
-Passive

HCO3
-CA in cell => H and HCO3
HCO3Cl exchange/ Na cotransport => blood
-NaH exchange => H secretion

Water

• Osmosis, follows movement of NA
• Used by CA

Question 14

Why is secretion important

Answer 14

Remove K, drugs and protein bound molecules

Question 15

Describe how

• organic cations
• organic anions are secreted into the PT

Name some examples of each organic molecule

Answer 15

Organic cations

• creatine, dopamine, morphine
• FD => H OC exchange (driven by NaH exchange)

Organic anions

• FA, PAH, bile salts, furosemide, penicilin
• OA DC exchange(driven by Na DC exchange) => AT out

Question 16

How does increased renal flow affect

• GFR?
• amount of reabsorption/secretion

Answer 16

GFR increases

Reabsorption decreases
Secretion increases