The urinary system involves the filtration of unwanted substances from the blood and excreting them through urine. Following are the steps of formation of urine: filtration glomerular, reabsorption in tubular, tubular secretion, and conservation of water (Chez et al., 1964). All the processes guarantee that only excessive water is excreted out of the body.
Glomerular Filtration:
Every single kidney comprises about million-minute structures known as nephrons. Every nephron contains a glomerulus, which is the place for the filtration of blood. The glomerulus contains a web of capillaries which is bordered by a small cup-like structure known as capsule glomerular. When blood moves from the glomerulus, the pressure of blood pushes the solutes and water from the capillaries. This separation in the glomerular begins the formation of urine.
Tubular Reabsorption
The glomerulus is responsible for the filtration of tiny solutes and water out of the blood. The rest contains excess but it also contains elements that the body requires such as amino acids, glucose, etc. The rest exits the glomerulus and enters the canal in the nephron called the renal tubule. Some useful elements are absorbed again through the tube wall.
Tubular Secretion
The filtrate from the glomerulus enters the renal tubule. Water and nutrients are absorbed again here into the capillaries. Waste from the capillaries passes into the renal tubule like ions and hydrogen ions. The process is generally known as secretion. The excreted ions combine together with the rest and become urine. This urine then flows from the nephron tubule into the duct known as the tubule duct. Then it moves down the bladder.
Water Conservation
The kidney’s nephron processes blood and creates urine through the filtration process. The constituent of urine is water about 95% and waste material about 5%. All the wastes including nitrogenous waste excreted in the urine including uric acid and ammonia. Other ions like potassium, sodium, calcium, and hydrogen are also eliminated.
References
Chez, R. A., Smith, F. G., & Hutchinson, D. L. (1964). Renal function in the intrauterine primate fetus: I. Experimental technique; rate of formation and chemical composition of urine. American Journal of Obstetrics & Gynecology, 90(1), 128-131.
Picken, L. E. R. J. (1937). The mechanism of urine formation in invertebrates: II. The excretory mechanism in certain Mollusca. Journal of Experimental Biology, 14(1), 20-34.
