Question

Why does absorption of digested food occur mainly in this small intestine
A. digestion is completed in the small intestine.
B. Presence of villi
C. Wall of the intestine is richly supplied with blood vessels
D. All of the above

Answer 1

Hint: The stomach, and the small intestine, is a type of hollow tube about 20 feet long which runs from the stomach to the beginning of the large intestine. The food is broken by the small intestine from the stomach and it absorbs as many nutrients as possible from the food which we take. Post digestion, the digested food is passed into the large intestine from the small intestine.

Complete answer:
Digestive system: - It consists of following which are tabulated as follows:

Organ	Movement
Mouth	Chewing
Oesophagus	Peristalsis
Stomach	The upper muscle in the stomach and it relax to let the food relaxes for let the food enter, and the lower muscle mixes with the help of lower muscle food with digestive juice
Small intestine	Peristalsis
Pancreas	None
Liver	None
Large intestine	Peristalsis

Villi: -
The intestine villi are very small, it looks like finger-like projections and that extend into the lumen and the small intestine. Each of them is approximately 0.5-1.6 mm in length and it also has many microvilli projections from the enterocytes of its epithelium and they are collected from the brush border and the striated. They are very much smaller than any of the circular folds present in the intestine.

Blood vessels: -
They play a very important role in transport. They are a part of the circulatory system. They transport the absorbed and assimilated nutrients with the help of blood throughout the body. The important types of blood vessels are veins, arteries. Veins generally bring the blood away from towards the heart while arteries transport oxygenated blood away from the heart.

So, the correct answer is an option (D) All of the above.

Note:
The small intestine has four types of layers in that which are the outermost serosa, submucosa, muscular, and innermost mucosa. In the intestine, villi are found which increases the surface area for absorption. The rich supply of the blood vessels in the intestine facilitates the absorption, assimilation and transportation of the digested food.