Nephrons are the microscopic structural and functional units of the kidney, crucial for the process of filtering blood, removing waste, and regulating fluid and electrolyte balance.
Each kidney contains about 1 million nephrons. A nephron is composed of two main parts: the renal corpuscle and the renal tubule.
Renal Corpuscle
The renal corpuscle is the initial filtering component of the nephron and is located in the renal cortex. It consists of two main structures:
1. Glomerulus:
A cluster of capillaries where blood filtration begins, separating water and small solutes from larger molecules.
2. Bowman's Capsule:
Encases the glomerulus, with an inner layer (podocytes) and an outer layer, collecting the filtrate to pass it to the renal tubule.
Renal Tubule
The renal tubule is a long, coiled tube that converts the filtrate from the Bowman's capsule into urine by reabsorption and secretion. It is divided into several segments:
1. Proximal Convoluted Tubule (PCT):
Reabsorbs water, sodium, glucose, and nutrients from the filtrate.
2. Loop of Henle:
Extends into the medulla, with descending and ascending limbs to concentrate urine by regulating water and salt levels.
3. Distal Convoluted Tubule (DCT):
Further adjusts ion balance and pH, playing a key role in regulating potassium, sodium, and calcium.
4. Collecting Duct:
Receives processed filtrate from multiple DCTs, fine-tuning water reabsorption and determining urine's final concentration and volume.