Digestive System of Earthworm
The earthworm’s digestive system is made up of the alimentary canal and accessory digestive glands. Which looks like “a tube within a tube”.
Alimentary Canal
It is a straight long tube that runs from the first segment to the last segment of the body. It consists of the following parts-
Buccal Cavity
The buccal cavity is present in segments 1st to 3rd.
Pharynx
It is located in the 4th segment.
Oesophagus
The esophagus is present in the 5th-7th segments.
Gizzard
It is present in the 8th segment. It is an organ made of muscles and covered with cuticles, which perform the function of grinding food.
Stomach
In the 9th to 14th segments, there is a tubular stomach.
Intestine
It starts from the 15th segment and extends till the last segment.
The intestine of an earthworm is divided into the following parts-
Pre-Typhlosole Region
From the 15th to the 26th segment there is a pre-typhlosole region. It contains small villi.
Typhlosole Region
Typhlosolw region starts from the 27th segment and extends to the 23-25th segment in front of the anus. Typhlosole is a large villus. It increases the effective area of absorption in the intestine.
Post-Typhlosole Region
It is also called the rectum. It is present in the last 23-25 segments and opens outwards through the anus.
Accessory Digestive Glands
The following glands are present in the digestive system of earthworms which secretion helps in digestion of food-
Pharyngeal Gland
On the dorsal side of the pharynx, the pharyngeal or salivary gland is present, which is made up of chromophil cells. It produces mucin for lubrication of food, and also produces some proteolytic enzymes, which digest certain proteins.
Calciferous Glands
Calciferous glands are present in the stomach, which produce calcium carbonate (CaCO3) to neutralize humic acid present in the humus of soil.
Intestinal Caecae
On the 26th segment, a small and cone-shaped pair of intestinal caeca emerges from the intestine. It secretes an amylolytic enzyme, which digests starch. Other enzymes are also secreted such as lipase, cellulose invertase, etc.
In the intestine, chloragogen cells are also present, which take part in the excretory functions and act as the liver of humans.
Lymph Glands
These are white soft bodies, which are found on one side of the dorsal vessel from the 26th segment, and grow in successive segments. These glands produce phagocyte cells of coelomic fluid.
Digestive System of Earthworm
Organ and Segment
- Buccal Cavity 1-3
- Pharynx 4
- Oesophagus 5-7
- Gizzard 8
- Stomach 9-14
- Intestine 15 – Last
- Intestinal Caecae 26
- Typhlosole Region 27 – 22/23
Read also – Cell wall and Cell Membrane Structure and Function
External link – https://www.youtube.com/channel/UCReNpLfZfk_JHo9TVSCdlWA/
