Question

what is excretion? how does it work

Answer 1

Answer:

Excretion is the process of removing wastes and excess water from the body. Recall that carbon dioxide travels through the blood and is transferred to the lungs where it is exhaled. In the large intestine, the remains of food are turned into solid waste for excretion.

Explanation:

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Answer 2

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What is excretion? How does is work.

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Nitrogenous waste material generated due to metabolic activities are harmful and thus, should be removed from the body. Unicellular organisms remove these wastes by simple diffusion from the body surface into the surroundings whereas, in case of multicellular organisms removal of waste is performed by specialized organs.

The process by which harmful metabolic watse products are eliminated form the body is called excretion.

$\maltese$ Mechanism of Excretion»

The waste materials along with blood is brought to the kidneys by renal arteries. Blood is filtered out from the blood capillaries(glomerulus) into Bowman's capsule.

When filtrate passes through the tubular part of the nephron useful products like glucose, amino acids, $\underline{\rm{Na^+,Cl^-,K^+}}$ ions and a large amount of water are selectively reabsorbed into blood capillaries and are transferred into blood circulation.The amount of water reabsorbed depends on how much excess water is there in the body and on how much of dissolved waste is present to be excreted.

$\Large\dashrightarrow$ All nephrons open into collecting tubules, which open into collecting duct, which further lead into renal pelvis. Urine pásses from the pelvis into the ureter, which takes it to the urinary bladder and leaves the bladder during micturition(urination) via the membranous such called urethra. Urine is stored in urinary bladder until the pressure of the expanded bladder leads to the urge to páss it our through urethra. The bladder is muscular and under nervous control. As a result, we can usually control the urge to urinate.

$\Large\dashrightarrow$ Urine is pale yellow in colour(due to urochrome). It is acidic (pH 6.0) and composed of 96% water, 2.5% organic substances and 1.5% inorganic substances.

$\Large\dashrightarrow$ Urine contains 2% urea, small amounts of creatinine, ammonia, oxalic acid and phenolic acid.

$\Large\dashrightarrow$ On an average, an adult produces about 1.5 litre of urine per day.

$\Large\dashrightarrow$ Normally, in a healthy adult, the infiltrate in kidneys is about 180L daily. However, the volume of urine actually excreted out is only 1-2L per day, because the remaining filtrate is reabsorbed in the kidney tubules(vasa recta)

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To understand the mechanism of excretion, first you've to thoroughly go through the components of excretory organs in humans, and ‘nephrons’

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