Role of Kidneys in Maintaining Body Homeostasis Quiz

Biology of Excretion, Kidney Composition, and Functions

The Role of Kidneys in Maintaining Body Homeostasis

Kidneys are critical organs that play a pivotal role in maintaining the balance of water, electrolytes, and waste products within our bodies. They filter blood to remove excess nutrients, acids, and toxins, while preserving essential elements to ensure optimal bodily function. This process is essential to regulate the body's acid-base balance, blood pressure, electrolyte levels, and osmotic pressure.

Urine Formation and Excretory System Organs

Urine is produced as a byproduct of blood filtration and is then transported for excretion. The excretory system, including the kidneys, ureters, urinary bladder, and urethra, collaborates to filter blood and expel waste products. The filtration process begins with the glomerulus, a complex network of capillaries that filter blood at a pressure of approximately 60mmHg.

Functions of the Kidney

1. Filtration: Blood is filtered at a rate of about 200 liters per day to produce urine. The filtrate contains water, essential electrolytes, and urea but excludes larger molecules, blood cells, and proteins.

2. Reabsorption: Tubules of the nephrons selectively reabsorb essential nutrients and water while removing waste products. This vital process maintains the body's balance of water, electrolytes, and glucose.

3. Secretion: The renal tubules secrete hydrogen ions, potassium ions, and ammonia to help maintain acid-base balance and remove excess substances from the blood.

4. Regulation of Blood Pressure: Renin, a hormone produced by the kidneys, regulates blood pressure. As the blood flow to the kidneys decreases, renin is secreted to increase angiotensin, which constricts blood vessels and promotes aldosterone release. Aldosterone then increases sodium and water reabsorption by the kidneys, leading to increased blood volume and consequently, blood pressure.

5. Production of Erythropoietin and Vitamin D Activation: The kidneys produce erythropoietin, a hormone that stimulates red blood cell production. They also convert vitamin D to its active form, calcitriol, which promotes calcium absorption and supports bone mineralization.

Kidney Structure

The kidneys are bean-shaped organs that are roughly the size of a fist. They consist of three layers, with an outer renal fascia, a perirenal fat capsule, and an inner renal capsule. Each kidney contains around 1 million nephrons, the functional units of the kidney that consist of renal corpuscles, renal tubules, and associated capillary networks.

The kidneys are divided into renal cortex and renal medulla. The cortex contains the nephrons and is responsible for filtration and reabsorption. The medulla is composed of pyramid-shaped lobules, which contain collecting ducts and loop of Henle. The loop of Henle plays a vital role in concentrating urine and regulating water reabsorption.

The Role of the Ureters and Urinary Bladder

Ureters transport urine from the kidneys to the urinary bladder. The bladder stores urine until it is expelled from the body through the urethra. The urethra differs in males and females, as it is shorter and wider in males and has a longer, more tortuous passage in females.

Conclusion

The kidneys play a critical role in maintaining the balance of water, electrolytes, and waste products in the body. They filter blood, reabsorb nutrients and water, and secrete waste products to produce urine. Understanding the functions and structures of the kidneys is essential to appreciate their importance in maintaining our health and wellbeing.