Describe in brief how urine is produced in the human body.

The production of urine occurs in three major steps; they are as follows: Ultrafiltration: The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. High pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultrafiltration. During ultrafiltration almost all the liquid part of the blood comes out of the glomerulus and passes into the funnel-shaped cavity of the Bowman's capsule. The fluid entering the renal tubule is called the glomerular filtrate. The glomerular filtrate consists of water, urea, salts, glucose and other plasma solutes. Reabsorption: The glomerular filtrate entering the renal tubule is not urine. It is an extremely dilute solution containing a lot of useful materials including glucose and some salts such as those of sodium. As the filtrate passes down the tubule, much of the water is reabsorbed together with the useful substances. Tubular secretion: Certain substances like potassium (K+) in the normal course, are passed into the forming urine in the distal convoluted tubule. This passage involves the activity of the cells of the tubular wall, and hence it is called tubular secretion. The filtrate left after reabsorption and tubular secretion is called urine.

Name the organs that form the excretory system in human beings.

Excretory system in humans: The process of removal of waste mainly the nitrogenous waste from the body is called excretion. Organs that are concerned with the formation, storage and elimination of waste products constitute the excretory system. The organs that form the excretory system in human beings are as follows: A pair of Kidneys: These are the primary excretory organs eliminating nitrogenous wastes (chiefly urea) from the blood and throwing it out in the form of urine. A pair of Ureters: These narrow tubes carry urine from the kidneys to the bladder. Urinary bladder: The bladder's walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. Urethra: It is the tube that allows urine to pass out of the body.