Q.Describe the role of liver, lungs and skin in excretion.

Besides the kidneys, the lungs, liver and skin all help clear wastes from the body.

• Lungs: they remove large amounts of carbon dioxide, about 200 mL every minute, and also release a good deal of water each day.
• Liver: the largest gland in the body, it excretes through the bile it secretes, which carries away bilirubin and biliverdin, cholesterol, broken-down steroid hormones, certain vitamins and drugs; most of these leave with the digestive wastes. …

It is easy to think of excretion as the kidney's job alone, but several other organs quietly share the task of ridding the body of unwanted substances. The lungs, the liver and the skin each remove particular kinds of waste.

The lungs. These are important excretory organs chiefly because of the gas they clear. They get rid of large amounts of carbon dioxide, removing roughly 200 mL of it every minute. Along with this gas they also release a significant quantity of water each day, so with every breath the body is losing both a waste gas and water.

The liver. As the largest gland in the body, the liver contributes to excretion through the bile it secretes. Bile is not only a digestive juice; it is also a vehicle for carrying wastes out of the body. Through it the liver disposes of a range of materials:

• bilirubin and biliverdin, the bile pigments,
• cholesterol,
• broken-down steroid hormones,
• certain vitamins, and
• drugs.

Most of these substances eventually leave the body together with the digestive wastes.

The skin. The skin helps in excretion through two kinds of glands. …

Method: Answering a "Role of Multiple Organs in One Function" Question

Questions that ask you to describe how several different organs each contribute to one shared function (here, excretion) are best answered organ by organ, each with the same three-part mini-structure, rather than as one continuous paragraph.

Steps

Step 1: List the organs named in the question, in the order given

Set up one short section per organ so nothing is missed — a question naming three organs is implicitly asking for three matched answers, and a missing organ is treated as an incomplete answer regardless of how good the other two are.

Step 2: For each organ, name the specific substance(s) it removes

Avoid vague statements like "the liver helps in excretion." State exactly what leaves through that organ — carbon dioxide and water for the lungs; bile pigments, cholesterol, degraded hormones, vitamins and drugs (via bile) for the liver; sodium chloride, urea and lactic acid (via sweat) plus sterols, hydrocarbons and waxes (via sebum) for the skin.

Step 3: Name the structure or secretion that carries the waste out

Tie each substance to the actual route: bile for the liver, exhaled air for the lungs, sweat and sebaceous glands for the skin. This is what turns a list of chemicals into an explanation of the organ's excretory role. …