Biology · Excretory Products and Their Elimination · NEET
Yes, the lungs are accessory excretory organs. NCERT clearly says the lungs remove large amounts of CO2 (approximately 200 mL/minute) and also significant quantities of water every day. So breathing out also removes a waste gas (CO2) and water vapour, which counts as excretion.
The liver secretes bile which contains bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs. Bilirubin and biliverdin are the bile pigments (waste from broken-down haemoglobin). Most of these substances finally pass out along with the digestive wastes (in faeces), not through urine.
Both. The primary function of sweat is to cool the body surface, but NCERT says it also helps remove wastes. Sweat is a watery fluid containing NaCl, small amounts of urea and lactic acid. So its main job is cooling, but it also has a minor excretory role.
Sweat is a watery secretion from sweat glands containing NaCl, urea and lactic acid, and its main job is cooling. Sebum is an oily secretion from sebaceous glands containing sterols, hydrocarbons and waxes, and it gives a protective oily covering to the skin. Both are ways the skin eliminates certain substances.
Yes. NCERT ends the topic with a note that small amounts of nitrogenous wastes can also be eliminated through saliva. NEET has used this line as a fact-check, so remember: saliva can carry small amounts of nitrogenous waste.
The skin (through sweat) removes only small amounts of urea, plus NaCl and lactic acid. The kidney is the main organ for removing urea. So skin has a minor, helping role, while the kidney does the major work.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The lungs, liver and skin help in the elimination of excretory wastes besides the kidneys.
The lungs remove CO2 at approximately 200 mL per minute, along with significant quantities of water every day.
Bilirubin and biliverdin are the bile pigments. Bile also carries cholesterol, degraded steroid hormones, vitamins and drugs, which mostly pass out with digestive wastes.
Sweat is a watery fluid containing NaCl, small amounts of urea and lactic acid. Its main function is cooling the body, but it also helps remove some wastes.
Sebaceous glands eliminate sterols, hydrocarbons and waxes through sebum. Sebum also provides a protective oily covering for the skin.
Yes, small amounts of nitrogenous wastes can be eliminated through saliva too, as noted in NCERT.
