Railway Science (Biology – Excretory System)

Rhinoplasty: Surgery performed on the nose. Transplantation: Transfer organs from one body to another. Angiography: A type of X-ray used to check blood vessels. Cheiloplasty- Lip surgery.

Urine is light yellow in color, slightly acidic with the composition of water (95%), urea (2.5%), and other waste(2.5%).

The excretory system of human beings consists of the following organs - kidneys, ureters, bladder and a urethra. Decomposition of unused food proteins in the liver produces urea as waste.
This urea goes into blood. The function of kidneys is to filter the blood to remove urea. Each kidney contains thousands of tiny filters called nephrons. The liquid left in the kidneys is a yellowish liquid called urine which contains urea, other waste salts and excess water.
The urine formed in kidneys goes into the bladder through the tubes called ureters. Urine is stored in the bladder. The urine collected in the bladder is passed out from the body at regular intervals through the opening at the end of a tube called urethra.

(Ureter)- The ureters are bilateral thin (3 to 4 mm) tubular structures that connect the kidneys to the urinary bladder, transporting urine from the renal pelvis into the bladder. The pelvis works as a funnel, collecting urine as it flows into the ureter. The kidneys are two bean-shaped organs that filter blood. It is a part of the urinary system. It controls the acid-base balance (pH balance) of blood.

The gaseous wastes, oxygen, carbon dioxide, and water vapor are removed through the stomata of leaves and lenticels of stems and some of it is in the leaves and bark of trees. When the leaves and bark are shed, the wastes are eliminated. Raphides, tannins, resins, gum, rubber, and essential oils are some excretory products.

It is the net movement of water across a semipermeable membrane. Hemodialysis is a process by which wastes from the body are removed by using an artificial kidney.
A series of tubes, made up of semipermeable membrane are placed in a dialysis solution to remove the wastes and purified blood is pumped back into the body.
The dialysis fluid contains all the constituents of plasma except urea. Thus, urea gets removed from the blood by diffusion. Enzyme secreted by the kidney is part of a physiological system that regulates blood pressure.

Hemodialysis is a process by which wastes from the body are removed by using an artificial kidney. A series of tubes, made up of semipermeable membrane are placed in a dialysis solution to remove the wastes and purified blood is pumped back into the body. The dialysis fluid contains all the constituents of plasma except urea. Thus, urea gets removed from the blood by diffusion.

Excretion: The process where metabolic wastes are eliminated from an organism. In humans, this function is performed through the kidneys, lungs and skin. In animals, the main excretory products are Ammonia, Carbon Dioxide, Urea, Uric Acid, Guanine, and Creatine.
Modes of excretion in animals: Ammonotelism (Type of excretion-ammonia), Ureotelism (Type of excretion-urea), Uricotelism (Type of excretion- uric acid), Aminotelism (Type of excretion- amino acids), Guanotelism (Type of excretion - guanine).

As blood flows into each nephron, it enters a cluster of tiny blood vessels—the glomerulus. The thin walls of the glomerulus allow smaller molecules, wastes, and fluid—mostly water—to pass into the tubule.
Larger molecules, such as proteins and blood cells, stay in the blood vessel. Bowman's capsule: The part of the nephron in the human kidney; Carries out the function of ultra-filtration by allowing the water molecules and small molecules of other substances to pass through its selectively permeable wall; It thus forms glomerular filtrate.

Urine formation in the human body is mainly carried out in three phases: Glomerular filtration, Reabsorption and Secretion.
Glomerular filtration: Occurs in the glomerulus where blood is filtered; Blood is filtered in such a way that all the constituents of the plasma reach the Bowman’s capsule, except proteins.
Therefore, this process is known as ultrafiltration. Reabsorption: Around 99 per cent of the filtrate obtained is reabsorbed by the renal tubules.
Secretion: Tubular cells secrete substances like hydrogen ions, potassium ions, etc into the filtrate; Through this process, the ionic, acid-base and the balance of other body fluids are maintained;
The secreted ions combine with the filtrate and form urine. The urine passes out of the nephron tubule into a collecting duct.