Earthworm Digestive System

You may have seen earthworms often, but have you ever wondered how their miniscule bodies can digest the food that they devour? Earthworm digestive system is complex and comprises of several distinct parts, each serving a purpose of its own.

Understanding how an earthworm digestive system functions are crucial, especially if you are about to sit for the NEET. Listed below are the various parts and functionalities that drive an earthworm’s digestion. Note these functionalities in detail since this is one of the crucial chapters for your NEET!

Different Parts of the Digestive System

The alimentary canal of earthworm is divided into eight distinct parts, namely – 

  • Mouth

  • Buccal cavity

  • Pharynx

  • Oesophagus

  • Gizzard

  • Stomach

  • Intestine

  • Anus

Refer to the earthworm digestive system diagram given below to derive a better idea about its structure and divisions.

Segment-wise Division of Alimentary Canal

Refer to this table below to understand how many segments each of these portions occupy.

Alimentary Canal Parts

Number of Segments

Mouth

First segment

Buccal Cavity

Middle of 3rd segment

Pharynx

Between 3rd and 4th segment

Oesophagus

From 5th to 7th segment

Gizzard

Generally, 8th-9th. May only occupy 8th segment

Stomach

9th segment to 14th segment

Intestine

From 15th segment to the second last segment

Anus

Last segment

Studying Each Part of Earthworm Digestive System

Apart from understanding the segment division, you should also be able to recall the functionality of each part. 

  1. Mouth

The first segment, also known as peristomium, is present in an earthworm’s first segment. The prostomium is a part of this mouth, which helps earthworms dig and procure food. Needless to say, this ingestion of food takes place using its mouth. 

  1. Buccal Chamber

The buccal cavity is present on the second and third segments of an earthworm’s body. Muscular strands of the buccal cavity allow it to be protruded from its mouth. The primary function of this cavity is to hold all food particles while it is being ingested.

  1. Pharynx

Pharynx is a pear-shaped muscular structure present just adjacent to this buccal cavity. A groove separates this pharynx from the buccal chamber. Pharynx includes muscle, tissues, blood vessels and salivary glands. 

These salivary glands are unicellular and termed as chlormophil. Chlormophil cells are responsible for saliva secretion. Saliva helps in breaking down proteins into amino acids. Additionally, mucin enzyme assists in making the food soft, further aiding in the digestive procedure.

  1. Oesophagus

The main function of the oesophagus is to transfer the food from the pharynx to the gizzard. There are no glands present in this portion, making this tube-like structure only suitable for the passage of food.

  1. Gizzard

A gizzard is a highly muscular part of the alimentary canal, characterised by its cuticles and chitinous teeth. The teeth are responsible for crushing or grinding food particles. You can say that this portion is similar to the teeth in human beings.

  1. Stomach

After breaking down the food, the gizzard transfers it to the highly vascular, thin-walled stomach. Calciferous glands in this section produce lime carbonate. This compound is essential for neutralising the humic acid. Additionally, the glandular cells secrete special enzymes, breaking down proteins effectively.

  1. Intestine

The intestine is a portion that connects the stomach with the anus. It is a thin-walled segment, which is further divided into three parts – 

  • Pre-Typhlosolar Region – This part comprises of villi but lacks typhlosole.

  • Typhlosolar Region – In this middle section, typhlosole and villi co-exist. The highly vascular section effectively increases the intestinal surface area.

  • Post-Typhlosolar Region – It is the section that precedes the anus segment. Both villi and typhlosole are absent in this region.

  1. Anus

The last segment of the alimentary canal is a small round opening, known as anus. This part is responsible for the excretion of undigested food in the form of worm casting.

These eight sections are the primary divisions of an earthworm digestive system. Nonetheless, you should also study the physiology of such a digestive process.  

True or False

Q) Typhlosolar region in the earthworm intestine includes typhlosole but lacks villi.

Ans. False. Typhlosolar region is characterised by the presence of both villi and typhlosole. 

Digestion Physiology

  • The buccal cavity protrudes from the mouth to draw food inside. 

  • This food enters the pharynx through this cavity.

  • Salivary glands produce saliva, which softens the food and breaks proteins into amino acids.

  • Next, this food passes into the gizzard, undergoing grinding or crushing.

  • After it is adequately broken down, this food passes into the stomach, where it undergoes neutralisation using the calcification procedure. Furthermore, a proteolytic process ensures complete digestion of proteins.

  • Next, when this food travels to the intestine, the caeca produce amylase, ensuring the conversion of starch into glucose.

  • Villi inside the intestines absorb the digested food, while any undigested waste travels to the anus for excretion.

Theoretical Study to Ensure Success!

Ensure you do not neglect studying about the earthworm digestive system in detail. It can help you in your pursuit of better marks. Remember that no topic is unimportant, especially for those preparing for competitive examinations like NEET. 

Whether you are learning about earthworm gizzard or earthworm oesophagus, make sure you also take periodic breaks from your lessons. Stick to a balanced diet and ensure you acquire enough sleep each night. With enough dedication and smart learning, you too can achieve your lifelong dreams. 

Best of luck!

FAQ (Frequently Asked Questions)

1. What is Typhlosole Earthworm?

Ans. Typhlosole refers to any internal fold in the intestine or its inner wall. In earthworms, this typhlosole forms a dorsal flap, which is almost like a tube within a tube. The primary function of this typhlosole is increasing the surface area for digestion in an earthworm’s intestine.

2. What is the Function of Gizzard?

Ans. Gizzard includes teeth like protrusions and cuticles, which aid in grinding food particles. Before reaching the earthworm’s stomach, all food particles pass through this segment, which aids in digestion when it moves on to its stomach.

3. Which Segments Does the Stomach Occupy in Earthworms?

Ans. The stomach extends from the 9th segment to the 14th segment in an earthworm.