Human Kidney Structure and Functions

Structure

• The kidneys are two bean-shaped organs located in the lower back on either side of the spine
• Each kidney is about 4-5 inches long and 2-3 inches wide
• The kidneys are protected by the rib cage and are surrounded by a layer of fat

Functions

• Filtration: Kidneys filter waste and excess fluids from the blood
• Regulation of electrolytes: Kidneys regulate levels of electrolytes such as sodium, potassium, and calcium
• Regulation of acid-base balance: Kidneys help maintain the body's acid-base balance by regulating the levels of acid and base in the blood
• Production of hormones: Kidneys produce hormones that help regulate blood pressure, produce red blood cells, and maintain strong bones
• Waste removal: Kidneys remove waste products from the blood and excrete them in the urine

Nephrons

• The functional units of the kidney are called nephrons
• Each kidney contains about 1 million nephrons
• Nephrons consist of:
  • Glomerulus: a cluster of capillaries that filter the blood
  • ** Bowman's capsule**: a double-layered sac that surrounds the glomerulus
  • Proximal convoluted tubule: a tube where reabsorption of nutrients and water takes place
  • Loop of Henle: a U-shaped tube where further reabsorption and secretion occur
  • Distal convoluted tubule: a tube where final reabsorption and secretion occur
  • Collecting duct: a tube that collects urine and transports it to the renal pelvis

Blood Supply

• Kidneys receive about 20-25% of the total blood volume
• Blood enters the kidney through the renal artery and leaves through the renal vein

Urine Formation

• The process of urine formation involves:
  1. Filtration: blood is filtered in the glomerulus
  2. Reabsorption: nutrients and water are reabsorbed in the proximal convoluted tubule
  3. Secretion: waste products are secreted into the tubule
  4. Urine concentration: urine is concentrated in the loop of Henle and distal convoluted tubule
  5. Urine collection: urine is collected in the renal pelvis and transported to the bladder through the ureters

Kidney Structure

• Kidneys are located in the lower back on either side of the spine
• Each kidney is approximately 4-5 inches long and 2-3 inches wide
• Kidneys are protected by the rib cage and surrounded by a layer of fat

Kidney Functions

• Filter waste and excess fluids from the blood
• Regulate levels of electrolytes such as sodium, potassium, and calcium
• Maintain the body's acid-base balance by regulating acid and base levels in the blood
• Produce hormones that regulate blood pressure, produce red blood cells, and maintain strong bones
• Remove waste products from the blood and excrete them in the urine

Nephrons

• Functional units of the kidney
• Each kidney contains approximately 1 million nephrons
• Nephrons consist of:
  • Glomerulus: a cluster of capillaries that filter the blood
  • Bowman's capsule: a double-layered sac that surrounds the glomerulus
  • Proximal convoluted tubule: a tube where reabsorption of nutrients and water takes place
  • Loop of Henle: a U-shaped tube where further reabsorption and secretion occur
  • Distal convoluted tubule: a tube where final reabsorption and secretion occur
  • Collecting duct: a tube that collects urine and transports it to the renal pelvis

Blood Supply

• Kidneys receive approximately 20-25% of the total blood volume
• Blood enters the kidney through the renal artery and leaves through the renal vein

Urine Formation

• Involves filtration, reabsorption, secretion, urine concentration, and urine collection
• Blood is filtered in the glomerulus
• Nutrients and water are reabsorbed in the proximal convoluted tubule
• Waste products are secreted into the tubule
• Urine is concentrated in the loop of Henle and distal convoluted tubule
• Urine is collected in the renal pelvis and transported to the bladder through the ureters