Do you know what an accessory organ is? The accessory organ is the organ that helps or assists the main or primary organs in their functions. An accessory organ can lead a role of accessory for one function and at the same time lead as primary or main organ for some other function. Our body produces different types of waste products through metabolic activities. Principal metabolic wastes, namely nitrogenous wastes, are removed by the primary or major excretory organs, i.e., kidneys. But certain metabolic wastes cannot be removed by kidneys, like those of carbon dioxide, certain salts, etc. So, which organ will remove these wastes? There comes the role of accessory excretory organs. One of the accessory excretory organs is the lung. Lungs play a major role in respiration but assist the excretory system with their function of excretion.

What is an Excretory Organ?

Excretory organ refers to the organ that removes the waste products of metabolism from the body. Kidneys are the primary or major excretory organs in the human body.

CLEAR YOUR CONCEPTUAL DOUBTS ON ACCESSORY EXCRETORY ORGANS

What do you mean by Accessory Excretory Organs?

Some organs act as excretory organs besides their normal functions. Those organs are called accessory excretory organs. Lungs, liver, skin, and intestine are the accessory excretory organs that remove certain metabolic wastes like urea, ammonia, carbon dioxide, inorganic ions, etc., from the body.

Fig: Accessory Excretory Organs

Different Accessory Excretory Organs in Humans

In addition to kidneys, skin, liver, lungs, and the large intestine are the accessory excretory organs.

1. Skin– It is the largest external organ of the human body. It is one of the accessory excretory organs as skin also helps in eliminating certain excretory products from the body. The sweat glands and sebaceous glands are present in the skin that can eliminate certain substances through secretions. The sweat gland secretes sweat.

Sweat consists of water, some inorganic salts, mainly sodium chloride, and some traces of urea and glucose. Salt loss during sweating does not cause much problem because, with salt, water is also excreted out from sweat. It is advised to take saltwater after heavy exercise because taking plain water may cause electrolyte imbalance leading to muscle cramps.
Skin also contains sebaceous glands. This gland secretes sebum that contains some sterols, fatty acids, and hydrocarbons. This oily sebum secretion is protective in nature.

Fig: Skin

Study About Excretory System

2. Lungs– This organ is involved in respiration which involves the exchange of gases. While exchanging gas, elimination of carbon dioxide gas takes place, which is produced during cellular respiration and is not required by the body and has to be eliminated out of the body during exhalation. With carbon dioxide, water is also formed as a waste product during respiration which is eliminated as water vapor during this. Lungs remove approximately 200 mL/minute carbon dioxide and about 400 ml of water per day.

Fig: Lungs

3. Liver– Excess amino acid of proteins is deaminated by the liver, which forms ammonia. By the process of the Urea cycle, highly toxic ammonia is converted to less toxic urea in the liver. Urea is less toxic than ammonia. It is then removed by the kidneys.
The hemoglobin from the worn-out RBCs is broken down by the liver leading to the formation of bilirubin and biliverdin, which are then excreted through feces.
The liver also excretes cholesterol, steroid hormones, certain vitamins, and drugs via bile.
If the liver is infected or damaged, then it is not able to remove bile pigments which get accumulated in the blood and cause jaundice.

Fig: Liver

4. Large Intestine– Inorganic ions, such as calcium, magnesium, and iron, are transferred from blood to the cavity of the colon by the epithelial cells of the colon for removal with faeces.

Fig: Large Intestine

Chemical	Source	Organ of Excretion
Bile pigments	Hb breakdown in the liver	Liver to intestines (out of the body through feces)
CO2	Breakdown of glucose in cells	Lungs
Inorganic ions	Food and water	Kidneys, Large Intestine & salivary glands
Urea	Derived from ammonia	Kidneys & skin
Water	Food and water, breakdown of glucose	Kidneys, skin & lungs

Learn About Lymphoid Organs

Importance of Accessory Excretory Organs

1. These organs help in removing waste products of the body along with the Kidney.
2. Regulates the pH and the osmotic pressure of the body.
3. Maintains the homeostasis of the body.

Summary

From the above discussion, we came to know that in excretion, not only kidneys are involved, but there are some other organs too which contribute to the excretion. Those organs are called accessory excretory organs. Although that contribution is less, it is important. The liver, lungs, skin, and large intestine are the accessory excretory organs. The liver removes bile pigments and urea from the body. Lungs are involved in the removal of carbon dioxide, water, and heat. Skin removes urea, water, and salt from the body. These excretions are important as it helps in removing waste products of the body, maintaining homeostasis, etc.

PRACTICE QUESTIONS RELATED TO ACCESSORY EXCRETORY ORGANS

Frequently Asked Questions (FAQs) on Accessory Excretory Organs

Q.1. Why is the liver known as an accessory excretory organ of our body?
Ans: The liver helps in removing bile pigments, cholesterol, and certain drugs from the body.

Q.2. Is Kidney an accessory excretory organ?
Ans: No, the kidney is not an accessory excretory organ, but it is a main excretory organ.

Q.3. Are lungs an excretory organ?
Ans: Yes, lungs are accessory excretory organs.

Q.4. What is the largest excretory organ in our body?
Ans: Skin is the largest excretory organ in our body.

Q.5. Do lungs excrete water?
Ans: Yes, lungs excrete water.

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