Question

The essential work of small intestine is
(i) Disgestion
(ii) Assimilation
(iii) Absorption of water
(iv) Digestion and absorption of nutrients​

Answer 1

The essential work of small intestine is

(i) Disgestion

(ii) Assimilation

(iii) Absorption of water

☑ (iv) Digestion and absorption of nutrients

Small Intestine - It is the site of complete significance carbohydrates, proteins and fats.

• It is the longest part of the alimentary canal.
• It is responsible for absorption of nutrients.
• About 90% of nutrients takes place in small intestine.

Digestion - The process of breaking down complex and huge molecules of food into simpler and smaller molecules is called digestion.

Absorption - The process by which digested food passes from the alimentary canal into the blood.

Assimilation - Assimilation is the final Stage of the process of digestion. The simple soluble food is absorbed and transported to the different parts of the body. Then it will be of help in the utilisation of energy , growth and repair.

Answer 2

Answer:

The essential work of small intestine is digestion and absorption of nutrients.

Explaination :

$\bullet\:\:$Digestion : The process during which the complex, non diffusible and non-absorbable food substances by the action of enzyme called digestion.

$\tiny{\underline{\boxed{\sf Complex +non-diffusible \:food \:substance \underset{digestion}{\xrightarrow{\text{enzyme}}}simple + diffusible\: substances}}}$

$\bullet\:\:$Absorption : The process of diffusion of digested food into blood and lymph is called absorption.

★ Small Intestine :

• The stomach leads into a long, tubular, muscular, glandular and vascular structure called small intestine.
• It is present in coiled form in the abdominal cavity. These coils are held together by connective tissue membrane called mesenteries.
• It is about 6 meters long and 2.5 cms broad tube, compactly coiled within abdominal cavity.
• It has following 3 regions: Duodenum, Jejunum, Ileum.

i. Duodenum:

• It is 'U' shaped and is about 25 cms long. The bile duct and the pancreatic duct open into the duodenum.

ii. Jejunum:

• It is about 2.5 metres long and narrower than the duodenum. It is situated in between duodenum and ileum.

iii. Ileum:

• It is about 3.5 metres long.
• It is a little bit broader than the jejunum.
• Histologically mucosa, the innermost layer of the small intestine is highly folded into numerous finger-like projections called villi.
• Each villus is lined by columnar epithelium cells.
• These cells have microvilli to increase the area of absorption.
• The core of each villus has loose connective tissue with a central lymph vessel called lacteal.
• It absorbs fat. There are a large number of capillaries in the core for absorption.

Function of small intestine : In small Intestine, digestion of food and absorption of food takes place.