Question

Exit through large intestine is regulated by______
A) Sphincter muscle
B) Osmosis
C) Concentration gradient
D) Both A and B

Answer 1

Hint: Large intestine is the last part of the digestive tract. It absorbs water and vitamins and converts the waste into faeces which is removed from the body. this process of removal of waste or faeces is called egestion or defecation.

Complete answer:
To answer this question, we will look at the structure of the large intestine.
The large intestine has the following four parts-
i) Caecum- It is the first part of the large intestine. The food that has not been absorbed by the small intestine is passed to the caecum through the ileocecal valve. The caecum extends into the appendix which is a vestigial organ.
ii) Colon- It is the longest portion of the large intestine. It absorbs the remaining water and minerals from the digested food and converts them into faeces. It is further divided into-
a) Ascending colon
b) Transverse colon
c) Descending colon
iii) Rectum- Distally, the large intestine opens into the rectum, which receives the faeces from the colon and stores it until it is evacuated.
iv) Anal canal and anus- The anal canal is the terminal part of the gastrointestinal tract which opens to the outside through the anus. The anal sphincter is wrapped around the anal canal and regulates the release of faeces. The diagram below shows the structure of the large intestine.

Let also look into the other given options:
B) Osmosis is the movement of water molecules from the region of higher concentration to the region of lower across a semipermeable membrane.
C) Concentration gradient- Concentration gradient takes place when the concentration of one side is greater than the other. It is the driving force for several processes like osmosis, diffusion.

We can say that the large intestine opens to the outside through the anus which is regulated by the anal sphincter which means the exit of faeces through the large intestine is regulated by a sphincter muscle.

Hence, the correct answer is option ‘A’.

Note: Disorders of large intestine-
Constipation- Painful and infrequent elimination of faeces. Caused due to dehydration.
Lactose intolerance- The intestine is unable to digest lactose present in food. It causes cramps, bloating etc.