Digestive System Questions & MCQ — Practice with Answers

What is digestion

Digestion is the process of breaking down food into smaller substances called nutrients that the body can absorb and use. Food must be broken down because the particles are too large to pass through the walls of the small intestine into the blood. Without digestion, our body cannot get the energy and materials it needs to grow and repair itself.

Organs of the digestive system

Food passes through a series of organs in a specific order. The digestive system consists of the mouth, oesophagus (food tube), stomach, small intestine, and large intestine. Each organ plays a different role in breaking down food or absorbing nutrients. The correct order is important — food always moves in one direction from the mouth to the large intestine.

Digestion in the mouth

Digestion begins in the mouth. The teeth break food into smaller pieces by chewing — this is physical digestion. Saliva is produced by glands in the mouth and helps to moisten the food, making it easier to swallow. Saliva also contains substances that begin to break down starch in the food. The tongue helps to mix the food with saliva and pushes it to the back of the mouth for swallowing.

Absorption in the small intestine

The small intestine is where most absorption takes place. By the time food reaches the small intestine, it has been broken down into very small nutrient particles. The inner wall of the small intestine is lined with tiny finger-like projections called villi. Villi increase the surface area for absorption, allowing digested nutrients to pass through the intestinal wall and into the blood. The blood then carries these nutrients to all parts of the body.

Role of the large intestine

After nutrients are absorbed in the small intestine, the remaining undigested material passes into the large intestine. The main role of the large intestine is to absorb water from the undigested material. Once water is removed, the remaining waste becomes more solid and is eventually passed out of the body as faeces. The large intestine does not digest food — it only absorbs water and forms waste for removal.

“Digestion only happens in the stomach.” Digestion actually begins in the mouth, where teeth break food into smaller pieces and saliva starts to break down starch. The stomach continues digestion, and the small intestine completes it. Three organs are involved in digestion — not just the stomach.

“The stomach is the most important organ for digestion.” While the stomach plays a role in breaking down food, the small intestine is where most digestion is completed and where nearly all absorption of nutrients takes place. Without the small intestine, the body would not be able to absorb the nutrients it needs.

“Absorption happens in the stomach.” Absorption of digested nutrients mainly occurs in the small intestine, not the stomach. The small intestine is lined with villi that provide a large surface area to absorb nutrients into the blood. The stomach's main job is to break down food further, not to absorb nutrients.

“The large intestine digests food.” The large intestine does not digest food. By the time undigested material reaches the large intestine, digestion and nutrient absorption are already complete. The large intestine's role is to absorb water from the remaining waste and form faeces for removal from the body.