Formation of urine by the nephrons of kidneys:
The process of urine formation occurs in the nephrons. The process of urine formation occurs through the following steps;
It is the first step in urine formation and occurs when the blood enters the glomerulus. The capillaries of the glomerulus offer resistance to the flow of the blood and thus the blood pressure is setup. Due to this glomerular blood pressure water and dissolved slats glucose drugs urea and uric acid moves from the glomerulus to the inside of the Bowman’s capsule. The process by which the fluid is separated from the blood in the glomerulus is called the glomerular filtration process and the filtered substances are called glomerular filtrate, in glomerular filtration process large molecules, blood and platelets are unable to pass through the capillary walls.
Re-absorption of water and nutrients such as glucose, amino acids, and some salts like NaCl which are useful to the body occurs from the proximal tubule into the blood, this is selective re-absorption because excess of salts, urea and uric acid are not absorbed. Water is reabsorbed along the whole length of the nephron especially in the loop of Henle.
It is the mechanism by which substances are removed from the blood and are directly added to the tubular fluids. Hydrogen ion, ammonium and drugs such as penicillin are some of the substances that move from the blood into the distal tubule of nephron. Secretions keep the blood from becoming acidic.
Effects of hormones on the working kidneys:
Hormones are the chemical produced by the endocrine glands of the body. They enter the blood stream which carries them to the site of action to regulate functions of the body. As we know that kidneys contains many nephrons each consisting of proximal portion and distal portion. The proximal portion of the nephron is responsible for the re-absorption of the most of glucose from the filtrate. This function is under the indirect control of hormone insulin. Insulin is the hormone of pancreas secreted by the Islet of Langerhans. Insulin reduces the level of glucose in the blood.
The distal portion of the nephron is responsible or the re-absorption of water. This function is controlled by the hormone known as ADH secreted by the pituitary gland. Dehydration of the body by heavy sweating stimulates the pituitary gland to produce ADH which increases the re-absorption of water. On the other hand if the blood starts to become too dilute after drinking large quantity of water the secretion of this hormone is stopped and distal portion of the nephron thus fails to absorb water and the urine is more watery.
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