Excretory System in Humans: 20 MCQs with answers

Excretion

Excretion is defined as the removal of waste materials produced in the cells of living organisms.

Stomach

The organs for waste removal in the human body are the lungs, kidneys, and sweat glands. The stomach is part of the digestive system.

Lungs

Carbon dioxide is a gaseous waste produced during respiration and is expelled by the lungs during exhalation.

Urine

Urea and other unwanted salts dissolve in water to form a yellowish liquid waste called urine.

Urea

Urea is the major waste product of our body. It goes into the blood and makes it impure if not removed.

Ureters

Ureters are the narrow tubes from the inner side of each kidney that carry urine from the kidneys to the bladder.

Bladder

The bladder is a muscular bag-like structure situated in the lower abdomen that stores urine.

Nephrons

Each kidney has millions of microscopic filtering units called nephrons, which are its functional units.

Bowman's capsule

The nephron has a cup-shaped bag at its upper end called Bowman's capsule.

True

Urea is the major waste product of the human body; if urea and other wastes are not removed from the blood constantly, the person will soon die.

Urine

Urine contains 2.5% urea, 2.5% other waste salts, and 95% water.

Urinary tubule

Useful substances like glucose, amino acids, and most water are reabsorbed into the blood through blood capillaries surrounding the urinary tubule.

Both A and R are true, and R correctly explains A.

The kidneys filter urea and other wastes from the blood. Since urea makes blood impure and its constant removal is essential for life, the reason correctly explains why kidneys are essential.

Drinking water and keeping hygiene help prevent UTIs

The chapter states that drinking lots of water and keeping hygiene also help to prevent UTIs.

It converts toxic ammonia into less toxic urea

The liver converts toxic ammonia into less toxic urea, which is then passed to the kidneys for excretion. It also produces bile pigments from haemoglobin of dead RBCs.

Can lodge in the ureter, bladder, or urethra and block urine flow

A larger stone can get lodged anywhere in the ureter, bladder, or urethra, causing severe pain and blocking the flow of urine.

Filtration of blood in the glomerulus

The first step in urine formation is **filtration**, where impure blood enters the glomerulus and is filtered, allowing substances like urea and excess water to pass into Bowman's capsule.

False, as lungs and sweat glands also play significant roles.

The statement is **false** because while the kidneys are crucial for filtering blood and removing nitrogenous wastes, the **lungs** and **sweat glands** also excrete waste products like carbon dioxide and sweat, respectively.

The kidneys are likely not removing urea efficiently.

High levels of urea in the blood indicate that the **kidneys are likely not removing urea efficiently**, suggesting a potential impairment in kidney function.

Medications to manage pain

While medications can help manage pain, they do not address the underlying issue of stone formation. **Increasing water intake** and following a special diet are more effective in preventing future kidney stones.