[Biology Class Notes] on Role of Other Organs in Excretion Pdf for Exam

The liver is the largest and the busiest organ of the body. It performs a number of functions including the formation of urea. This area is actually excreted by the kidney in the form of urine. The process by which liver forms urea is called an Ornithine cycle. Through this process, more toxic waste ammonia is converted into less toxic urea. The liver also removes bile pigments like biliverdin and bilirubin from the body. These bile pigments are the breakdown products of the hemoglobin of the dead RBCs. The liver also removes excess cholesterol, vitamins to an extent. Thus the liver plays an important role in excretion.

Order of toxicity of nitrogenous waste –

uric acid < urea < ammonia

A Brief on What is Excretion

In order to understand what are the roles of different organs in excretion, we must first know what is excretion. 

Excretion is a biological process by which the body removes unwanted substances which are present in excess and the metabolic wastes produced during various biochemical reactions from itself. 

In the human body, excretion is performed, by the excretory system. This excretory system in addition to the removal of wastes also helps in maintaining the osmoregulation of our body in order to maintain homeostasis.

There are two types of organs involved in excretion. These are –

• Accessory organs 

• Necessary organs

Role of Kidney in Excretion

A pair of kidneys, a pair of ureters, a urinary bladder, and urethra forms the urinary system and are the necessary organs of excretion.  Kidneys are bean-shaped the d structures present near the dorsal body wall between the 11th and 12th  thoracic vertebra and 1st and 2nd  lumbar vertebra. The function of the kidney is to remove the nitrogenous waste urea, from the body in the form of urine. Nephron is the structural and functional unit of the kidney.

Other Excretory Organs of the Body

There are organs other than the kidney which performs the role of excretion and such organs are called the accessory organs of excretion. They are meant to perform some other function of the body and in addition to those functions, they perform excretion also. 

Liver, Lungs, Skin are some of the accessory organs of excretion.

Role of Lungs in Excretion

It is already mentioned that excretion refers to the removal of unwanted substances that are undesirable and are present in excess amounts in the body. Lungs perform the function of removing the carbon dioxide from the body which is a gaseous waste.

All the cells of our body are constantly involved in metabolic reactions. Due to this certain wastes like carbon dioxide are continuously formed and are collectively brought to the lungs through blood and are released out by the expiration process. Thus lungs play an important role in excretion.

Role of Skin in Excretion

Glands of skin (soft epidermal derivatives of skin) are also involved in excretion. There are different glands present in the skin. The following are some glands involved in the excretion process.

These are simple coiled tubular glands. They maintain the temperature of the body by releasing sweat which causes a cooling effect. Sweat has a small amount of urea in addition to the extra water thus in a way sweat glands are also involved in excretion.

These are the glands that are played in the hair follicle and their secretion is called sebum, which is not a watery secretion. Some of the lipid wastes are released in sebum from these glands of the skin.

Importance of Other Excretory Organs

These glands are present in the buccal cavity. There are 3 salivary glands present at different places in the mouth. Together they all release a secretion called ‘saliva’.This saliva has water, mucous, and also a little amount of urea in it. So salivary glands are also excretory to an extent.

They are also known as lacrimal glands and are found in the eyes. Their secretions are called tears which are watery and absorb amounts of urea waste in it. Thus tear glands also help in the removal of the waste.