Chapter 19: Excretory Products and Their Elimination

When there is a fall in glomerular filtration rate (GFR), they activate the JG cells to release renin which gets converted to angiotensinogen in the blood to angiotensin I and further to angiotensin II. Angiotensin II is a powerful vasoconstrictor that increases GFR. Angiotensin II is also responsible for activating the adrenal cortex to release Aldosterone which causes reabsorption of Na+ and water from the distal parts of the tubule leading to an increase in blood pressure and GFR.

When there is a fall in glomerular filtration rate (GFR), they activate the JG cells to release renin which gets converted to angiotensinogen in the blood to angiotensin I and further to angiotensin II. Angiotensin II is a powerful vasoconstrictor that increases GFR. Angiotensin II is also responsible for activating the adrenal cortex to release Aldosterone which causes reabsorption of Na+ and water from the distal parts of the tubule leading to an increase in blood pressure and GFR.

Organisms which generally excrete ammonia as nitrogenous wastes are said to be ammonotelic in nature.

Excretion of urea requires a large amount of water which can only be provided by aquatic animals while on the other hand, terrestrial animals cannot afford to lose so much water. The terrestrial mammals or even amphibians mainly excrete nitrogenous wastes in form of urea and hence are known as ureotelic organisms

The glomerular filtrate is formed at the first step of the urine formation in the Bowman’s capsule while urine is formed at the end of the nephron.

The procedure advised for the correction of extreme renal failure is kidney transplantation. Donor compatibility is evaluated by blood tests that match the blood types and antigens.

The terrestrial mammals or even amphibians mainly excrete nitrogenous wastes in form of urea and hence are known as ureotelic organisms while reptiles, etc. excrete nitrogenous wastes in form of uric acid and hence are called uricotelic organisms. Thus this is how the conversion of ammonia to urea or uric acid has been the adaptation that the terrestrial organisms have gone through for conservation of water.

A haemodialysis unit is also called an artificial kidney because it is responsible for performing the same functions that a kidney functions.

Selective reabsorption is the process in which some molecules like glucose, ions and certain amino acids get reabsorbed from the filtrate as they pass through the neuron. ADH i.e. Antidiuretic hormone and ANF i.e. Atrial Natriuretic Factor are the hormones which monitor the function of the kidney. ADH functions as the facilitation of the reabsorption of water from DCT. The adrenal cortex is activated by Angiotensin II as a result of which aldosterone is released. Aldosterone, in turn, induces the DCT to absorb more ions and water. ANF regulates blood flow by causing vasodilation and increasing excretion of sodium.