Digestive system of earthworm

Question 1

Alimentary canal :

Answer 1

• Alimentary canal of earthworm is complete straight, tubular structure which extends from mouth to anus.

Question 1

Parts of alimentary canal are?

Answer 1

1. Mouth
2. Buccal Cavity
3. Pharynx
4. Oesophagus
5. Gizzard
6. Stomach
7. Intestine
8. Anus

Question 2

1) Mouth :

Answer 2

On the ventral side of first segment, just below the prostomium, there is a circular aperture called mouth.

Question 3

2) Buccal Cavity (1st to 3rd= 3) :

Answer 3

Mouth leads to a small cavity called buccal cavity which extends to 3rd segment. The cavity is supported by special muscles called protractor and retractor muscles. Protractor muscles are responsible for pushing or extending structures forward whereas retractor muscles pull structures back to their original position.

Question 4

3) Pharynx (3rd to 4th = 1) :

Answer 4

It is a pear shaped structure that lies in 4th segment, in which buccal cavity opens and extends to 6th segment. It is highly vascular and glandular. There is a mass of glandular cells called pharyngeal mass which produces mucus and digestive enzymes. Due to presence of protractor and retractor muscles, pharynx acts as protractor and retractor muscles.

Question 5

4) Oesophagus (5th to 7th =2 ) :

Answer 5

Pharynx opens to a small, narrow and straight tube called oesophagus which conducts food from pharynx to gizzard.

Question 6

5) Gizzard (8th) :

Answer 6

Prominent, hard, thick walled oval shaped structure which grinds the food into small particles.

Question 7

6) Stomach ( 9th to 14th =6 )

Answer 7

Small straight highly vascular, glandular, tubular structure where chemical reactions and digestions take place. Both ends are sphinctered. It secretes proteolytic enzyme which helps in protein digestion. Calciferous glands in stomach help to remove excess calcium and carbonate from food.

Question 8

7) Intestine ( 15th to last )

Answer 8

The part from 15th to 26th segment is internally folded, highly vascular and glandular cells. There are two conical outgrowths in the 26th segment called caeca which extend to 22nd segment. Behind the 26th segment, there is highly infolded and vascular region called typhlosole which increases the area and absorption.

Question 9

8) Anus

Answer 9

Lies at the terminal part from where food is ejected out in the form of castings.