Earthworm Digestive System Short Notes

Earthworm Digestive System Short Notes

In this article we will discuss about the earthworm digestive system

Earthworm Digestive System

  • Earthworm digestive system consists of the alimentary canal and the digestive glands
  • Alimentary canal is long and straight and runs between the first and last segment of the body
  • Alimentary canal that begins with a various parts i.e. Mouth and buccal chamber, pharynx, oesophagus, gizzard, stomach, and intestine.
  • Earthworm digestive system breaks down food into nutrients and they can then be absorbed into the bloodstream so the body can use them for energy, growth and repair

Alimentary Canal and Digestive Glands

Mouth 1
  • Present in peristomium overhung by prostomium
  • Food ingestion takes place through mouth
Buccal cavity 1-3
  • Mouth opens into buccal cavity
  • It helps in holding the food during ingestion
Pharynx 4
  • Buccal cavity leads into a wide opening called pharynx
  • Roof of pharynx contains pharyngeal glands containing chromophil cell. Secreting mucus and proteases
Oesophagus 5-7
  • Pharynx leads into a short thin walled narrow duct called oesophagus
  • It passes food to the gizzard
Gizzard 8-9
  • Oesophagus opens into an thick walled muscular organ called gizzard
  • It grinds the food into fine particle
Stomach 9-14
  • Wall of stomach contain calciferous glands
  • Calciferous glands secrete calcium and CO2
  • Calcium helps in neutralising humic acid in the humus
  • Glandular cells of the stomach secrete proteolytic enzymes
Intestine 15 – last
  • Stomach opens into long, wide and thin walled intestine
  • The intestine is divided into 3 parts:
    1. Pre-typhlosolar region: present from 15-26 segment. It contains villi. Short conical projection on the 25th segment, which is known as intestinal caeca and its secrete amylase enzyme
    2. Typhlosolar region: present after the 26th segment, typhlosole is the large internal median fold of the dorsal wall of the intestine. Typhlosole increase the area of absorption in the intestine
    3. Post-typhlosolar region: present in 36 segment and beyond. It stores faecal pallets and leads to the anus
Anus Last
  • Small round aperture present in the last segment.
  • Undigested food is excreted out through the anus
  • Earthworm faeces are called as casting
  • Casting improve the fertility of the soil

Physiology of Digestion in Earthworm

  • Mouth and the buccal cavity takes part in the ingestion
  • In pharynx saliva mixed with ingested food
  • Food then pass through oesophagus into gizzard
  • In gizzard grinding or crushing of food material takes place into fine state
  • Grinded food material enters into the stomach. Calcification process start.
  • Food then move into intestine.
  • Various enzymes present in the intestine act on food.
  • Typhlosole increases the absorption surface of the intestine
  • Undigested food is egested out through the anus
  • Earthworm faeces are called as casting

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