Excretory System
Category : 10th Class
Excretory System
The main excretory organ of human is kidney and skin. Kidney is a bean shaped organ, which lies in the abdominal cavity one on each side of the vertebral column. Each of them is about 10 cm long and 150g in weight. It is enclosed in a thin, fibrous covering called the capsule. A renal artery brings blood into the kidney along with nitrogenous waste materials, which after filtration in the kidney leaves the kidney through a renal vein. The outer region of kidney is called cortex and inner region is called medulla. Each kidney is made up of numerous coiled excretory tubules, called nephrons. A nephron is the structural and functional unit of kidney. It performs three functions, such as, filtration, reabsorption and secretion. A nephron consists of a long tubules and the Malpighian corpuscle. The proximal end of the tubules consists of Bowman's capsule and the glomerulus.
Bowman's capsule is a double walled cup like structure, which surrounds the dense network of blood capillaries called the glomerulus. Some substance in the initial filtrate, such as glucose, amino acids, salts and a major amount of water are selectively reabsorbed as the urine flows along the tube. The amount
of water reabsorbed depends on how much excess water is there in the body and on how much of dissolved waste is there to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through urethra.
Artificial Kidney
Some time it is possible that kidney may be damaged due to infection, injuries and extreme blood pressure. This results in accumulation of toxic substance like urea in the blood, which can even lead to death of the individual. This can be treated by artificial methods using dialysis. It is a artificial kidney which purify the blood. It consists of long tube like structure made of cellophane suspended in a tank. It is partially permeable and therefore allows solutes to diffuse through.
Excrection in Plants
Plants do not have well developed excretory system to throw out the waste material, because of different physiology, as compared to the animals. The gaseous waste materials are excreted out through the small opening in leaves of the plant, called stomata. The other waste material are excreted in the form of fluid, called latex and resins. It is also removed by the methods of periodic shedding of leaves and bark of the stem. The fruits and the seeds, which grows in plants are also the waste material for the plants.
How many molecules of ATP are produced by the complete oxidation of one gram mole of glucose?
(a) 30
(b) 38
(c) 46
(d) 64
(e) None of these
Answer: (b)
The spherical shaped organ which helps in exchange of oxygen from blood is called:
(a) Bronchi
(b) Trachea
(c) Alveoli
(d) Epiglottis
(e) None of these
Answer: (c)
The end product of glycolysis is:
(a) Pyruvate
(b) ATP
(c) ADP
(d) Lactic Add
(e) None of these
Answer: (a)
Which types of respiration takes place in mitochondria?
(a) Anaerobic
(b) Aerobic
(c) Reduction
(d) All of these
(e) None of these
Answer: (b)
Which tissue helps in transportation of water and minerals in plants?
(a) Xylem
(b) Phloem
(c) Sieve Tube
(d) Parenchyma
(e) None of these
Answer (a)
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