Excretion - 2 (Class X)

The cup-shaped part of nephron which receives the glomerular filtrate is called Bowman’s capsule.

The blood in kidneys is filtered by nephrons, the functional units of the kidney. Each nephron begins in a renal corpuscle, which is composed of a glomerulus enclosed in a Bowman's capsule.

Several collecting ducts unite to form larger ducts that empty urine into a calyx at the tip of the renal pyramid. 

Along with the removal of waste, kidneys also maintain constant blood pressure. One of the major roles of the kidneys is maintaining the proper levels of electrolytes (such as sodium and potassium) in the body. The amount of electrolytes in the body influences the amount of fluid in the body. When electrolyte levels are high, the body retains more water, which in turn increases the volume of the blood. More blood volume results in higher blood pressure. Thus, the kidneys maintain blood pressure by indirectly controlling the amount of blood in the body. 

 Excess water is excreted from plants through the stomata in leaves.  Plants can get rid of excess water by transpiration and guttation.

In kidneys, glucose is mainly absorbed in proximal convoluted tubule.

Resins and gums are the excretory products of plants. In the different parts of the plant body, crystals of some chemical substances are set aside, for example calcium carbonate crystals in the leaf of fig, calcium oxalate crystals in the leaf of colocasia. These excretory materials do not harm the plant. Saprophytic plants such as Mucor, Rhizopus and Penictllium excrete their wastes through diffusion.

Only creatinine and uric acid are the organic substances present in urine.

Heart is not an excretory organ. 

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions occurring in many animals. Organisms that cannot easily and quickly remove ammonia usually have to convert it to some other substance, like urea or uric acid, which are much less toxic. Insufficiency of the urea cycle occurs in some genetic disorders (inborn errors of metabolism), and in liver failure. The result of liver failure is accumulation of nitrogenous waste, mainly ammonia, which leads to hepatic encephalopathy.

As the ureters pass obliquely through the bladder wall, their openings get shut due to compression of the contracting bladder muscles to prevent the backward flow of urine.

Waste products can be stored in leaves that fall off. Other waste products are stored as resins, gums, raphides and tannins, especially in old xylem. 

Typical brush border of cells is seen in proximal convoluted tubules. The microvilli greatly increase the luminal surface area of the cells, presumably facilitating their resorptive function as well as putative flow sensing within the lumen.

Plants get rid of oxygen through their stomatal pores. Air enters the plant through these openings, and contains carbon dioxide and oxygen, which are used in photosynthesis and respiration, respectively.

In public urinals, the urine gives a pungent smell due to the conversion of urea into ammonia by bacteria.