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Difficulty: HardAnimal Nutrition and Digestive System

In the alimentary canal of the cockroach (*Periplaneta americana*), specialized anatomical regions carry out distinct physiological processes during nutrition. Which of the following statements correctly describes the function of a named section of this digestive system?

  1. Hepatic caeca secrete digestive enzymes into the midgut to facilitate extracellular chemical digestion.Answer
  2. B
    The gizzard secretes saprophytic digestive enzymes externally to dissolve solid organic matter prior to ingestion.
  3. C
    Malpighian tubules absorb digested fatty acids and amino acids from the midgut into the haemolymph.
  4. D
    Low environmental temperatures permanently denature digestive enzymes stored in the crop, preventing carbohydrate hydrolysis.

Answer

Hepatic caeca secrete digestive enzymes into the midgut to facilitate extracellular chemical digestion.
In the cockroach, six to eight finger-like projections called hepatic (gastric) caeca are present at the junction of the gizzard and the midgut. These caeca secrete digestive enzymes into the mesenteron (midgut), where the chemical hydrolysis of carbohydrates, proteins, and fats takes place extracellularly.

Step-by-Step Solution

1
Analyze the structural organization of the insect (cockroach) digestive tract.
The digestive tract is divided into foregut (stomodaeum), midgut (mesenteron), and hindgut (proctodaeum).
Understanding regional specialization is required to evaluate each functional claim.
2
Evaluate the physiological function of the hepatic (gastric) caeca.
Six to eight blind-ended hepatic caeca are situated at the junction of the foregut and midgut. They secrete digestive juice containing enzymes into the midgut.
This confirms that chemical digestion in the midgut relies on secretions from the hepatic caeca.
3
Differentiate digestive function from excretory function and enzyme temperature kinetics.
Malpighian tubules handle excretion, gizzards grind food mechanically inside the body, and low temperatures cause reversible inactivation rather than denaturation.
This rules out all incorrect alternatives based on biological principles.

Key Concept

Insect digestive system anatomy and physiological modifications in animal nutrition
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Topics

Animal Nutrition and Digestive System

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