Physiology of the Urinary System

Posted by e-Medical PPT Wednesday, July 27, 2011
Functions of Nephron Structures
Glomerulus

The site for blood filtration
operates as a nonspecific filter; in that, it will remove both useful and non-useful material
the product of the glomerulus is called filtrate
Proximal Convoluted Tubule (PCT)
A thick, constantly actively segment of the nephron that reabsorbs most of the useful substances of the filtrate: sodium (65%), water (65%), bicarbonate (90%), chloride (50%), glucose (nearly 100%!), etc.
The primary site for secretion (elimination) of drugs, waste and hydrogen ions
Decending Limb of the Loop of Henle
A part of the counter current multiplier
freely permeable to water and relatively impermeable to solutes (salt particles)
receives filtrate from the PCT, allows water to be absorbed and sends “salty”filtrate on the the next segment. “Saves water and passes the salt”
Ascending Limb of the Loop of Henle
a part of the counter current multiplier
impermeable to water and actively transports (reabsorbs) salt (NaCl) to the interstitial fluid of the pyramids in the medulla. “Saves salt and passes the water.”
the passing filtrate becomes dilute and the interstitium becomes hyperosmotic
Distal Convoluted Tubule (DCT)
receives dilute fluid from the ascending limb of the Loop of Henle
Variably active portion of the nephron
When aldosterone hormone is present, sodium is reabsorbed and potassium is secreted. Water and chloride follow the sodium.
Collecting Duct
receives fluid from the DCT
variably active portion of the Nephron
when antidiuretic hormone (ADH) is present, this duct will become porous to water. Water from the collecting duct fluid then moves by osmosis into the “salty” (hyperosmotic) interstitium of the medulla.
The last segment to save water for the body
Peritubular Capillaries
transport reabsorbed materials from the PCT and DCT into kidney veins and eventually back into the general circulation
help complete the conservation process (reabsorption) that takes place in the kidney

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