Mammalian kidney

Mammalian Kidney

The mammalian kidney is a vital organ in mammals responsible for filtering waste products from the blood and excreting them, along with water, as urine. This complex organ plays a crucial role in the homeostatic regulation of various bodily functions, including electrolyte balance, blood pressure regulation, and the maintenance of acid-base balance.

Structure

The mammalian kidney is bean-shaped and located retroperitoneally on either side of the vertebral column. Each kidney is composed of three main sections: the outer cortex, the middle medulla, and the renal pelvis. The functional unit of the kidney is the nephron, of which there are approximately one million in each kidney. Nephrons are responsible for the filtration of blood and generation of urine.

Cortex

The renal cortex contains the renal corpuscles, which include the glomerulus and Bowman's capsule, and the proximal and distal convoluted tubules. The cortex is where the filtration of blood begins.

Medulla

The renal medulla consists of the loops of Henle and the collecting ducts. It is in the medulla where urine concentration occurs, allowing for the reabsorption of water and critical ions back into the bloodstream.

Renal Pelvis

The renal pelvis is a funnel-shaped structure that collects the urine produced in the kidney and channels it into the ureter, leading to the bladder.

Function

The primary function of the mammalian kidney is to remove waste products and excess substances from the blood through the production of urine. This process involves filtration, reabsorption, secretion, and excretion.

Filtration

Blood enters the kidney through the renal artery, which branches into smaller arterioles feeding into the glomeruli. Here, filtration occurs as blood pressure forces water and solutes out of the blood and into the Bowman's capsule, forming the filtrate.

Reabsorption and Secretion

As the filtrate passes through the nephron, essential nutrients and water are reabsorbed back into the bloodstream, while waste products and excess ions are secreted into the filtrate.

Excretion

The final urine, containing waste products and excess ions, flows into the collecting ducts, through the renal pelvis, and down the ureters to be stored in the bladder until excretion through the urethra.

Regulation

The kidney's function is closely regulated by various hormones, including antidiuretic hormone (ADH), aldosterone, and atrial natriuretic peptide (ANP), which adjust the kidney's absorption of water and electrolytes to maintain homeostasis.

Diseases

Kidney diseases, such as chronic kidney disease (CKD) and acute kidney injury (AKI), can significantly impair the kidney's ability to function properly. These conditions can lead to a buildup of waste products in the blood, electrolyte imbalances, and hypertension.

Conclusion

The mammalian kidney is a critical organ for maintaining the body's internal environment. Its complex structure and function enable the efficient removal of waste products, regulation of blood pressure, and balance of electrolytes and fluids within the body.