renal tubule

Nephron

Nephron s microscopic structural and functional unit of kidney.

Nephron accomplishes initial filteration of blood, selective reabsorption back into blood of filtered substances that are useful to the body and the secretion of unwanted substances.

Nephron composed of -

1. Renal corpuscle

2. Renal tubule

1. Renal corpuscle or Malpighian corpuscle

Part of nephron where fluid is filtered, it is made up of glomerulus and glomerular capsule or Bowman's capsule.

2. Renal tubule

Part into which filtered fluid passes.

Renal tubule composed of -

1. Proximal convoluted tubule

2. Loop if Henle

3. Distal convoluted tubules

Continuing from glomerular capsule, remainder of the nephron is about 3cm long.

. Renal tubules

Part of nephron that leads away from glomerulus.

Renal tubules has 3 main section-

1. PCT

2. Medullary loop

3. DCT

4. Collecting duct

1. Proximal convoluted tubules (PCT)

PCT is portion attached to glomerular capsule. (Highly coiled)

It lie in cortex of kidney.

14mm long and 60 micrometer in diameter.

Brush border of microvilli on apical surface increase the surface area for reabsorption and secretion.

PCT is site for reabsorption of many substances filtered from blood such as -

Water, glucose, electrolytes, some amino acids and polypeptides.

About 65% water and upto 100% of some solute that pass through endothelial capsular membrane return to blood stream from PCT.

2. Loop of Henle 

U shaped

After passing through PCT - glomerular filtrate enter straightened portion of excretory tubules called loop of Henle.

Loop of Henle is continuation of PCT. 

It connect proximal convoluted tubules and distal convoluted tubules.

Major function bis active reabsorption of sodium and chloride and

Passive diffusion of water resulting in urinary concentration.

3. DCT

Irregularly shaped

DCT is highly coiled portion of  kidney nephron between loop of Henle and collecting tubule.

Reabsorption of HCO3-

Selective secretion of H+ and potassium ion and NH3 to maintain the PH and Na+/k+  balance in blood.

4. Collecting duct

This is a long duct extends from cortex of kidney to the inner parts of medulla.

Large amount of water could be reabsorbed from this region to produce concentrated urine.

Collecting tube unit forming larger duct

Papillary duct

Minor calyx

Major calyx

Renal pelvis

Urine drain into ureters

After collecting duct glomerular filtrate is called urine.