Loop of Henle and Vasa Recta notes

What structures make up a nephron?

Glomerulus, Bowman's Capsule, Proximal Convoluted Tubule (PCT), Loop of Henle, Distal Convoluted Tubule (DCT)

How many nephrons are in both kidneys combined?

About 2.4 million

What happens in the descending limb of the Loop of Henle?

Water leaves via aquaporins due to increasing interstitial osmolality; solutes stay inside (impermeable to solutes)

What happens in the ascending limb of the Loop of Henle?

Solutes (Na⁺, K⁺, Cl⁻) are actively reabsorbed; water remains (impermeable to water)

What transporter moves solutes out of the ascending limb?

Na⁺/K⁺/2Cl⁻ co-transporter

What is the osmolality of filtrate at the top of the ascending limb?

~200 mOsm/kg (hypotonic)

What is the Countercurrent Multiplier system?

A process in the Loop of Henle where opposite flow directions help establish a concentration gradient in the medulla

Define high osmolality.

High solutes, low water — hypertonic

Define low osmolality.

Low solutes, high water — hypotonic

Define isotonic.

Equal amounts of solutes and water

What is the vasa recta?

A slow-moving peritubular capillary system in the medulla that acts as a countercurrent exchanger

What happens in the descending limb of the vasa recta?

NaCl is absorbed, and water leaves due to high medullary osmolality

What happens in the ascending limb of the vasa recta?

NaCl diffuses out, and water re-enters as osmolality decreases

What is the significance of the vasa recta’s countercurrent exchange?

Maintains medullary gradient by preventing rapid NaCl washout; delivers oxygen and nutrients to deep kidney tissues