eLFH - Renal Physiology Part 1

Question 1

Functions of the kidney (8 of them)

Answer 1

Excretion of metabolism waste products
Regulate water balance and electrolytes
Regulate arterial pressure
Regulate acid base balance
Secretion, metabolism and excretion of hormones (eg prostaglandin)
Erythropoietin production
1-25 dihydroxy-vitamin D3 production
Gluconeogenesis

Question 2

Diagram illustrating components of renal tubule

Answer 2

Question 3

Renal tubule microanatomy

Answer 3

Nephron is 1 cell thick

Basolateral membrane separates cells from peritubular capillaries

Tight junctions between tubular cells at the luminal membrane

Question 4

Volume of filtrate entering proximal tubules daily

Answer 4

180 L

Most is reabsorbed by renal tubules to avoid massive water and solute loss

Question 5

Processes by which substances are transported in the renal tubules

Answer 5

Diffusion

Osmosis

Primary and Secondary active transport

Question 6

Types of diffusion

Answer 6

Simple diffusion

Facilitated diffusion

Question 7

Facilitated diffusion definition

Answer 7

Requires interaction of a carrier protein

Shuttles the substance across the membrane

Question 8

Primary active transport in renal tubules

Answer 8

Energy consuming process

Na+/K+ ATPase pump transports 3 sodium ions out of tubular cell across the basolateral membrane into interstitial fluid, and 2 potassium ions into cell from interstitial fluid

Creates electrochemical gradient from tubular luminal fluid to tubular cell

Therefore Na+ moves from luminal fluid into tubular cell down its electrochemical gradient - this releases energy for secondary active transport

Question 9

Secondary active transport definition

Answer 9

Movement of 2 substances at the same time using a carrier protein

It uses the gradient created by primary active transport as an energy source and it can cotransport or counter-transport molecules

Question 10

How does reabsorption of water / solutes occur from transport perspective

Answer 10

Water / solutes move from luminal fluid to interstitial fluid either transcellular path or paracellular path (driven by concentration, osmotic or electrical gradients)

Move from interstitial fluid into peritubular capillary (mediated by hydrostatic and oncotic pressures)