The excretory system

 The excretory organs are: 

  1. Lungs
  2. Skin
  3. Kidney


The lungs are found in the chest area. There are two lungs involved in breathing. As oxygen is used up in the body, carbon dioxide into the blood.

The carbon dioxide is passed out of the blood into the lungs. the lungs eliminate carbon dioxide from the body through the trachea or windpipe.

Human skin

This is the outer body covering the surface of the body. The skin has two layers; the outer layer called the epidermis and the inner layer called the dermis. the dermis is under the epidermis. The skin acts as a protective covering around the body. 

The skin excretes sweat. Sweat contains water, salts and small quantities of urea. The epidermis contains small pores through which sweat leaves the body. The dermis contains sweat glands that produce sweat.

As sweat leaves the body, it absorbs heat from the skin giving the body a cooling effect. 



The Kidney is dark red in colour. They are shaped like beans. There are two kidneys in human beings and they are found at the back of the abdomen about the waist level.

The kidneys excrete urea, other nitrogenous waste, salts and excess water from the blood. As these waste material travel from the kidney, they combine to form urine.

The urine flows out of the kidney through the ureter into the urinary bladder. The bladder acts as a temporary store for urine. When it gets full, one feels the urge to pass out urine a process called urination.

Urine flows from the bladder into the urethra and out of the body.


KCPE Topical Questions

Standard 8

Excretory system

Which one of the following organs is correctly matched with one of its functions?



A.    Heart

Regulating body temperature

B.    Skin

Removing salts

C.    Kidney

Removing sugar

B.    Gall bladder     

Storing urine