Describe the structure and functioning of nephrons
Terms used and their contextual meaning
Absorption/absorbed: Taken back into the body through the vascular system.
Secretion: excreted into the kidney.
There is a network of fine capillaries called glomerulus and long-tube like structure called nephrons. Glomerulus filter out the waste products and nephrons receives this waste and excrete it out.
Nephrons are the structural and functional unit of the kidney. It has a cup-shaped Bowman’s capsule, Proximal Convoluted Tubule (PCT), Loop of Henle), Thick ascending limb, Distal Convoluted Tubule (DCT).
Functions:
Bowman’s capsule: It is the central filtering part of the nephron. The glomerulus is coiled inside this capsule, and waste materials secrete into the nephron from here. Mineral ions, glucose, amino acid, water, etc are also excreted here. But later parts of nephron absorb them and bring back to the vascular system.
Glucose here is absorbed completely and is never secreted out.
Proximal Convoluted Tubule (PCT): PCT has only absorption role. Things which are needed by the body like Glucose, Amino acids, Water, Mineral ions are absorbed back to the system. It also absorbs bicarbonate ions to maintain the alkaline PH of blood.
Loop of Henle: PCT opens into the thin descending limb and thin ascending lib. They are collectively called loop of Henle. Descending limb is permeable to water only. As a result, water is absorbed here and Hypertonic urine form here.
Ascending limb is permeable to cations only. Here cations are absorbed. As a result, the solution becomes isotonic here.
Distal Convoluted Tubule (DCT): DCT also has only absorption role. But here it is hormone controlled.
Aldosterone works on PCT and absorbs Sodium and water.
Parathormone from thyroid increases calcium absorption.
DCT opens into collecting duct. Collecting duct is the final stage of urine formation. Here water is absorbed, and rest is eliminated out.
(Photo credit Wikimedia Commons)
Next: Methods used by plants to get rid of excretory products.
See also: How are water and mineral transported in plants?
