Digestive tract of flatworms - SS2 Biology Lesson Note

Flatworms, also known as Platyhelminthes, possess a simple digestive system that reflects their relatively simple body structure. Their digestive tract consists of a mouth, pharynx, and a branched gastrovascular cavity.

The mouth of a flatworm serves as the entry point for food. It is located on the ventral side of the body and is usually surrounded by sensory structures that aid in locating prey. Flatworms have a muscular pharynx that extends from the mouth and acts as a sucking organ. The pharynx can be everted or extended outwards to capture and engulf food.

Once the food is ingested through the mouth, it enters the gastrovascular cavity. This cavity is a branching network of interconnected canals that extends throughout the body of the flatworm. It serves both as a digestive chamber and a circulatory system. Nutrients are absorbed directly into the body cells from the gastrovascular cavity through diffusion.

Digestion within the gastrovascular cavity of flatworms is mainly extracellular. Gland cells lining the cavity secrete enzymes that break down the food into smaller molecules. These enzymes facilitate the digestion of proteins, carbohydrates, and fats.

As the food is broken down, nutrients are absorbed across the cells lining the gastrovascular cavity and transported to the various body cells through diffusion. The waste products resulting from digestion, such as undigested food particles and metabolic byproducts, are eliminated from the body through specialized excretory structures called flame cells or protonephridia.

Digestive tract of a flatworm (dsip.weebly.com)

Overall, the digestive system of flatworms is relatively simple, reflecting their relatively simple body organization. The gastrovascular cavity functions both in digestion and nutrient distribution throughout the body, highlighting the efficiency of these animals' basic digestive processes.