The nephrons of the kidney (400X)

Nephrons are the functional units of the kidney and are found throughout the renal cortex and medulla. Each nephron consists of several components, including:

1. Renal Corpuscle: Located in the renal cortex and consists of Bowman's capsule and glomerulus. The glomerulus is a tuft of capillaries responsible for filtration, and Bowman's capsule surrounds and collects the filtrate. Single-layered squamous epithelium is found in the parietal layer of Bowman's capsule.
2. Proximal Convoluted Tubule (PCT): After the renal corpuscle, the filtrate enters the PCT for reabsorption of substances like glucose, amino acids, and ions.
3. Loop of Henle: It extends into the renal medulla and has a descending and ascending limb. It plays a role in concentrating urine by creating an osmotic gradient.Where the loop of Henle passes into the distal tubule, the tubule system passes between the supplying and efferent arteriole to its own glomerulus. It is the epithelial cells from the distal tubules that are in contact with the arterioles called the macula densa. The adjacent smooth muscle cells in the arteriole wall in this area are called juxtaglomular cells and can make and release renin.
4. Distal Convoluted Tubule (DCT): After the loop of Henle, the filtrate enters the DCT for further reabsorption and secretion of ions and acid-base balance.
5. Collecting Duct: Collecting ducts from multiple nephrons merge in the medulla, and they are responsible for the final concentration or dilution of urine based on the body's hydration status.

Renin is a protein-splitting enzyme that is produced by smooth muscle cells (juxtaglomular cells). In the blood, renin converts angiotensinogen to angiotensin 1. This is in turn converted to angiotensin 2 by another enzyme in the endothelial cells of the pulmonary circulation. Angiotensin 2 stimulates increased aldosterone synthesis from the zona glomerulosa in the adrenal cortex. Aldosterone regulates the kidneys' sodium reabsorption.

Atrial natriuretic peptide, which is hormone, is released from the heart's anterior chamber walls,  inhibits the reabsorption of sodium in the kidneys