7. Insect digestive and excretory systems

7. Insect digestive and excretory systems


Although all insects have common
structures in their digestive systems, these structures can be highly variable
between species based on the diversity of foods that insects eat. We will use
the grasshopper to illustrate the basic principle for these common structures. the insect digestive system is divided into three main sections: the foregut, the midgut and the hind gut. The foregut is comprised of the mouth
for ingesting food, the pharynx and esophagus for transporting food and the crop where food is stored prior to digestion and absorption. If the food is
solid it moves from the crop into a muscular proventriculus where it may be
further ground before passing through the stomadeal valve into the midgut. The midgut is the region for the digestion of food and the absorption of nutrients. Finger-like projections called gastric caeca occur at the junction of
the midgut and proventriculis and serve as major structures for nutrient
absorption. Unabsorbed food particles pass through the proctodeal valve into the hindgut. At the junction of the midgut and hindgut are a group of long, thread-like tubules that flex about in the hemolymph. These tubules are called Malpighian tubules, and they are the insect excretory system. Malpighian tubules filter the hemolymph and form a urine containing water, salts,
small metabolites, the nitrogenous waste products and any toxic chemicals that are present. Undigested food from the midgut along with the Malpighian tubule urine are passed into the hindgut. Special cells in the rectum selectively
re-absorb the water, salts and small metabolites, and the remaining waste
products are excreted. By selectively taking all water, salts, and small molecules into the Malpighian tubules, then selectively re-absorbing the
water, salts and metabolites in the hindgut, the insect can rid its body of waste and any unanticipated toxic chemicals, while maintaining a normal metabolite and water balance.

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19 thoughts on “7. Insect digestive and excretory systems

  1. Excelent video. I already finished a book about insect's digestion and this video summarizes it perfectly.

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