Secretion

A few substances (e.g., organic acids,

organic bases, K+) are secreted from peritubular capillary blood into tubular fluid for excreting substances in the urine.

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#Id: 5571

#Unit 7. System Physiology – Animal

In juxtamedullary nephrons with longer loops and thin ascending limbs, the osmotic gradient is spread over a greater distance and the osmolality at the tip of the loop is greater.

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#Id: 5572

#Unit 7. System Physiology – Animal

Recirculation of Urea from the Collecting Duct to the Loop of Henle Contributes to Hyperosmotic Renal medullary interstitium and formation of concentrated urine

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#Id: 5573

#Unit 7. System Physiology – Animal

The recirculation of urea helps to trap urea in the renal medulla and contributes to the hyperosmolarity of the renal medulla.

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#Unit 7. System Physiology – Animal

There are four isoforms of the transport protein:  UT-A in the kidneys (UT-A1 to UT-A4) UT-B in the erythrocytes & descending limbs of the vasa recta 

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#Id: 5575

#Unit 7. System Physiology – Animal

Urea transporters UT-A1 and UT-A3 facilitate diffusion of urea out of the medullary collecting ducts while UT-A2 facilitates urea diffusion into the thin descending loop of Henle.

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#Id: 5576

#Unit 7. System Physiology – Animal

The vasa recta do not create the medullary hyperosmolarity,but they do prevent it from being dissipated