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Internal Anatomy of an Insect

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Diagram of the Insect Digestive System
Internal Anatomy of an Insect

Insect digestive system.

Illustration courtesy of Piotr Jaworski (Creative Commons license), modified by Debbie Hadley

The insect digestive system is a closed system, with one long enclosed tube (alimentary canal) running lengthwise through the body. The alimentary canal is a one way street – food enters the mouth and gets processed as it travels toward the anus. Each of the three sections of the alimentary canal performs a different process of digestion.

The salivary glands (30) produce saliva, which travels through salivary tubes into the mouth. Saliva mixes with food and begins the process of breaking it down.

The first section of the alimentary canal is the foregut (27) or stomodaeum. In the foregut, initial breakdown of large food particles occurs, mostly by saliva. The foregut includes the Buccal cavity, the esophagus, and the crop, which stores food before it passes to the midgut.

Once food leaves the crop, it passes to the midgut (13) or mesenteron. The midgut is where digestion really happens, through enzymatic action. Microscopic projections from the midgut wall, called microvilli, increase surface area and allow for maximum absorption of nutrients.

In the hindgut (16) or proctodaeum, undigested food particles join uric acid from Malphigian tubules to form fecal pellets. The rectum absorbs most of the water in this waste matter, and the dry pellet is then eliminated through the anus (17).

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