Kidney Function and Anatomy

The kidneys perform several essential functions: 1. **Filtration**: They filter waste products, excess substances, and toxins from the blood, forming urine. 2. **Regulation of Blood Pressure**: By controlling blood volume and releasing the enzyme renin, they help regulate blood pressure. 3. **Electrolyte Balance**: They maintain the balance of electrolytes like sodium, potassium, and calcium. 4. **Acid-Base Balance**: They help maintain the pH of the blood by excreting hydrogen ions and reabsorbing bicarbonate. 5. **Hormone Production**: They produce hormones such as erythropoietin, which stimulates red blood cell production.

The kidneys are bean-shaped organs located in the lower back, surrounded by a protective layer of fat. Each kidney has several key parts: 1. **Cortex**: The outer layer containing nephrons, the functional units of the kidney. 2. **Medulla**: The inner region composed of renal pyramids that contain collecting ducts. 3. **Renal Pelvis**: A funnel-shaped structure that collects urine from the medulla and leads to the ureter. 4. **Nephrons**: Each kidney contains approximately a million nephrons, which include a renal corpuscle (glomerulus and Bowman's capsule) and tubules (proximal and distal convoluted tubules, and loop of Henle).

Nephrons are the functional units of the kidney and play a crucial role in urine formation through three main processes: 1. **Filtration**: Blood enters the glomerulus, where water, ions, and small molecules are filtered through the glomerular membrane into Bowman’s capsule, forming filtrate. 2. **Reabsorption**: As the filtrate passes through the renal tubules, essential substances like glucose, certain ions, and water are reabsorbed into the bloodstream. 3. **Secretion**: Additional waste products and toxins are secreted from the blood into the tubules. The remaining filtrate, now urine, is collected in the renal pelvis.