The Digestive System of Hirudinaria | Leech | Diagram

---

Hirudinaria is a genus of medicinal leeches that belong to the phylum Annelida. These leeches are hermaphroditic and possess a complex digestive system adapted for their blood-feeding lifestyle. In this article, we will learn about the digestive system of Hirudinaria.

Diagram of The Digestive System

---

The Digestive System of Hirudinaria

The digestive system of Hirudinaria or leech is described below in two parts: the alimentary canal and food, feeding, and digestion mechanism.

Alimentary Canal of Leech

• The alimentary canal of the leech is complete.
• It is a straight tube.
• The alimentary canal starts from the mouth and ends at the anus.
• It is divided into the buccal cavity, pharynx, oesophagus, crop, stomach, intestine, and rectum.

1. Pre-Oral Chamber and Mouth

• • • The pre-oral chamber is a cup-like depression.
    • The pre-oral chamber is located at the ventral side of the oral sucker or anterior sucker.
    • The mouth is located on the roof of the pre-oral chamber.
    • The roof of the pre-oral chamber is formed by a membrane-like structure called the velum.
    • The mouth is a triradiate opening, located at the center of the velum.

2. Buccal Cavity

• • • The mouth leads into the buccal cavity.
    • It is a short chamber behind the velum.
    • Three crescentic jaws are present.
    • One jaw is mid-dorsal and the other two jaws are ventro-lateral in position.
    • Each jaw bears minute teeth or denticles in a single row.
    • The number of teeth is 103-128 on the median jaw and 85-115 on each lateral jaw.
    • Each jaw contains numerous openings of salivary glands.
    • Jaws produce the triradiate bite or Y-shaped wound in the skin of the host.

---

3. Pharynx

• • • The buccal cavity leads into the pharynx.
    • The pharynx of leech is highly muscular.
    • It is an oval sac extending from the 5th-8th segments.
    • Its inner surface bears longitudinal folds.
    • Externally, it is surrounded by salivary glands.
    • Secretion of these glands contains hirudin or anticoagulin.
    • The hirudin or anticoagulin prevents the coagulation of blood while the leech is feeding.

4. Oesophagus

• • • The pharynx leads into the oesophagus.
    • It is a short and narrow tube.
    • It has a very narrow lumen and a much folded epithelial lining.

5. Crop

• • • The oesophagus leads into the crop.
    • It is the largest portion of the alimentary canal.
    • It extends from the 9th to the 18th segment.
    • The crop is capable of great dilation to store an enormous quantity of blood.

6. Stomach

• • • The last chamber of the crop leads into a funnel-shaped tube.
    • The tube leads into a small heart-shaped stomach.
    • The stomach is present in the 19th segment.
    • The mucous lining of the stomach is thrown into anastomosing transverse folds.

---

7. Intestine

• • • The stomach leads into the intestine.
    • It is a thin-walled, straight, and narrow tube.
    • It extends from the 20th to the 22nd segments.
    • Its inner lining is thrown into numerous spiral folds and villi-like processes which increase its absorptive surface.

8. Rectum

• • • The intestine is followed by the rectum.
    • It is a somewhat dilated and thin-walled tube.
    • It extends from the 23rd to the 26th segments.
    • It opens to the exterior through the anus.
    • The anus is present mid-dorsally on the 26th segment.

————-THE END————–

Read More:

1. External Morphology of Hirudinaria granulosa | Leech | Diagram
2. General Characters of All Phylum of The Invertebrates.

---