Question

Describe the structure and working method of excretory system of human.

Hint:

The kidneys play a key role in maintaining homeostasis by filtering blood and regulating water and electrolyte balance, while the bladder stores urine until it is excreted.

Answer 1

The excretory system in humans is responsible for the removal of waste products and excess substances from the body. It consists of various organs and structures that work together to maintain internal balance (homeostasis) by regulating the composition of body fluids.
Structure:
The primary organs involved in the excretory system are the kidneys, ureters, bladder, and urethra.
1. Kidneys: The kidneys are two bean-shaped organs located on either side of the spine, below the rib cage. They contain millions of microscopic structures called nephrons, which are responsible for filtering blood and removing waste.
- The nephron consists of a renal corpuscle (which includes the glomerulus and Bowman's capsule) and a renal tubule (comprising the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct).
- The kidneys filter the blood, removing waste products and excess substances like water, salts, and urea, which are converted into urine.
2. Ureters: Two narrow tubes that carry urine from the kidneys to the bladder. Each ureter is connected to a kidney and empties into the urinary bladder.
3. Bladder: The bladder is a hollow muscular organ that stores urine until it is excreted. It can expand to hold about 400-600 milliliters of urine.
4. Urethra: The urethra is a tube that connects the bladder to the outside of the body. It is responsible for the excretion of urine from the body during urination.
Working Method:
The excretory process involves the filtration of blood, reabsorption of water and essential nutrients, and the elimination of waste. The sequence of steps is as follows:
1. Filtration: Blood from the renal artery enters the kidneys and is filtered in the glomerulus. The pressure forces water, salts, glucose, amino acids, and urea into the Bowman's capsule, forming a filtrate.
2. Reabsorption: The filtrate moves into the renal tubule, where essential substances like glucose, amino acids, and most of the water are reabsorbed into the bloodstream. This process occurs in the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
3. Secretion: Additional waste products, such as hydrogen ions and potassium, are secreted into the renal tubule from the blood.
4. Excretion: The remaining waste (urine), consisting of urea, excess salts, and water, moves into the collecting duct and is then transported to the bladder through the ureters. Urine is stored in the bladder until it is excreted through the urethra during urination.
The excretory system also helps in regulating the body's fluid balance, electrolyte levels, and blood pressure by adjusting the volume and concentration of urine produced.