Role of other Organs in Excretion

Accessory Excretory Organs

Kidneys are the main excretory organs, but the body also uses other organs to remove wastes. These are called accessory excretory organs.

Different organs remove different types of wastes:

Lungs → CO₂ + water vapour
Liver → bile pigments + drugs/toxins + cholesterol + urea formation
Skin → sweat (water + salts) + tiny urea; sebum (waxes/sterols)
Saliva → small nitrogenous wastes

1. Lungs (The Gas Exhaust)

The Trash: Carbon Dioxide ( $CO_2$ ) and Water vapor.
The Rate: Our lungs pump out a massive 200 ml of $CO_2$ every minute.
Think about it: That's like emptying a small soda can of gas every 60 seconds!

2. Liver (The Chemical Factory)

Status: The Largest Gland in the human body.
The Trash: The liver filters the blood and dumps waste into Bile.
- Waste List: Bilirubin, Biliverdin (from dead RBCs), Cholesterol, degraded Steroid hormones, Vitamins, and Drugs.
The Exit: These substances travel with the bile into the intestine and are eventually pooped out (Digestive Wastes).

3. Skin (The Surface Cleaner)

The skin has two types of glands that help remove waste while doing other jobs.

A. Sweat Glands (The Air Conditioner) 💧

The Fluid: Sweat (Watery fluid).
Ingredients: Mostly NaCl (Salt), but also small amounts of Urea and Lactic Acid.
Main Job: Cooling the body (Evaporation).
Side Job: Excretion of the wastes listed above.

B. Sebaceous Glands (The Oiler) 🛢️

The Fluid: Sebum (Oily/Waxy substance).
Ingredients: Sterols, Hydrocarbons, and Waxes.
Main Job: Providing a protective oily covering for the skin.
Side Job: Eliminating these specific hydrocarbon wastes.

4. Saliva

Even your spit helps! Small amounts of nitrogenous wastes are eliminated through saliva.

Lungs Stats: Remember 200 ml/min. (A standard juice box size of $CO_2$ ).
The Liver's Dump Truck: The Liver dumps trash into Bile, not urine.
Sweat vs. Sebum:
- Sweat = Watery + Salty + Urea (Cooling).
- Sebum = Oily + Waxy + Sterols (Protection).
Saliva: It's not just for digestion; it's a minor trash chute too!

💡 Questions and Answers

Q1. How much Carbon Dioxide do our lungs get rid of?

Answer: A significant amount! Approximately 200 ml every minute, along with some water vapor.

Q2. Besides cooling us down, what waste does sweat remove?

Answer: Sweat helps flush out NaCl (Salt), small amounts of Urea, and Lactic Acid.

Q3. Which gland excretes oily substances like waxes?

Answer: The Sebaceous glands. They produce Sebum, which carries out Sterols, Hydrocarbons, and Waxes.

Q4. Which is the largest gland in the body, and how does it help in excretion?

Answer: The Liver is the largest gland. It breaks down toxic substances (drugs, hormones, cholesterol) and dumps them into the bile to be eliminated with feces.

Q5: Can saliva help in excretion?