Nephron-Active secretion

Creatinine and some urea are secreted from the capillary network of the proximal tubule. These substances mix with the glomerular filtrate and are carried in the urine. Hydrogen ions, potassium ions, ammonium ions, serotonin, choline, histamine etc. are secreted from the distal tubule. All these substances mix with the filtrate and become urine.

Function, Importance of Nephron

1. Filtration: The glomerulus of the nephron filters water, salt, sugar, urea, uric acid, creatinine, hormones, metal ions etc. from the blood. These filtrates are called glomerular filtrates. Glomerular filtrate accumulates in the capsular space.
2. Reabsorption: Proximal tubule reabsorbs water, glucose, sodium bicarbonate, chloride, calcium, sodium chloride and distal tubule reabsorbs potassium, urea, uric acid, phosphate etc.
3. Active secretion: Creatinine and some urea are secreted from the capillary network of the proximal tubule. These substances mix with the glomerular filtrate and are carried in the urine. Hydrogen ions, potassium ions, ammonium ions, serotonin, choline, histamine etc. are secreted from the distal tubule. All these substances mix with the filtrate and become urine.
4. Creation of new substances: Inorganic phosphate, ammonia, hippuric acid etc. are created in epithelial cells. All these substances mix with other substances and become urine.
5. Acid production: Nephron produces different types of acid in the human body. The main acids produced by the nephron are sulfuric acid and lactic acid.
6. pH control: Nephron regulates pH in the body by storing alkaline substances and excreting acidic substances.
7. Controlling sodium levels: Sodium is an important buffer in our body. Nephrons regulate sodium levels in the human body.
8. Control of urine concentration: When the nephron tubules absorb water from the glomerular filtrate, the urine thickens. Again, if water is not absorbed from the glomerular filtrate, the urine becomes diluted.
9. Regulation of ion level: Kidney regulates the level of sodium, potassium, chloride etc. ions in the body.
10. Regulation of Osmosis: It regulates the osmotic pressure of blood and cells.

Distal convoluted tubule

The part from the loop of Henley to the collecting duct is called distal convoluted tubule. Its length is 5 mm and diameter is 22.5 μ. It is surrounded by peritubule capillary or epithelial cells. It is located in the cortex. The next part of the distal patchy duct is called the collecting duct. Several collecting ducts join to form the Duct of Bellini.

Loop of henle

The U-shaped tube extending from the proximal convoluted tubule to the distal convoluted tubule is called loop of Henle. This is called nephron leakage. It is located in the medulla and cortex. Its length is 11 mm and diameter is 20 μm. It consists of two parts. Descending limb and Ascending limb. The descending arm extends from the end of the proximal tubule to the medulla and the ascending arm is located in the cortex region. It is called loop of Henle after German medical scientist Friedrich Henle.

Proximal convoluted tubule

The tubule associated with Bowman’s capsule is called proximal convoluted tubule. Its length is about 14 cm and diameter is 57-60μ. These peritubules are covered by epithelial cells with capillaries or brush borders. At one end of the cells are numerous microscopic finger-like projections or microvilli. It is located in the cortex. This duct carries the filtrate from the glomerulus to the loop of Henley. The proximal tubule reabsorbs water, sodium ions, potassium, amino acids, glucose, chloride, peptide creatine and bicarbonate ions from the glomerular filtrate.

Renal tubule-anatomy, structure

Renal tubules are long, cylindrical patchy tubules that extend from the base of Bowman’s capsule to the ends of the collecting ducts. Each renal tubule is approximately 3 cm in length and has an average diameter of 60 micrometers. It consists of three parts. These are-
(i) Proximal convoluted tubule: The tubule associated with Bowman’s capsule is called proximal convoluted tubule. Its length is about 14 cm and diameter is 57-60μ. These peritubules are covered by epithelial cells with capillaries or brush borders. At one end of the cells are numerous microscopic finger-like projections or microvilli. It is located in the cortex. This duct carries the filtrate from the glomerulus to the loop of Henley. The proximal tubule reabsorbs water, sodium ions, potassium, amino acids, glucose, chloride, peptide creatine and bicarbonate ions from the glomerular filtrate.
(ii) Loop of henle: The U-shaped tube extending from the proximal convoluted tubule to the distal convoluted tubule is called loop of Henle. This is called nephron leakage. It is located in the medulla and cortex. Its length is 11 mm and diameter is 20 μm. It consists of two parts. Descending limb and Ascending limb. The descending arm extends from the end of the proximal tubule to the medulla and the ascending arm is located in the cortex region. It is called loop of Henle after German medical scientist Friedrich Henle.
(iii) Distal convoluted tubule: The part from the loop of Henley to the collecting duct is called distal convoluted tubule. Its length is 5 mm and diameter is 22.5 μ. It is surrounded by peritubule capillary or epithelial cells. It is located in the cortex. The next part of the distal patchy duct is called the collecting duct. Several collecting ducts join to form the Duct of Bellini.