Question

The function of typhlosole found in the of earthworm is to
A.Secrete digestive juice
B.Regulate the blood flow
C.Emulsify the food
D.Increase absorptive surface for digested food.

Answer 1

Earthworm is studied under Phylum Annelida of Kingdom Animalia. There are about 500 species of earthworms out of which 13 are found in India. Earthworm is a terrestrial animal of glistening deep brown or reddish-brown colour. They are found in wet soil containing rich organic matter, i.e., humus.
They usually live in burrows found in the upper layer of the soil.

Complete answer:
The stomach of earthworm leads into a wide thin-walled intestine which runs from the 15th segment to the last segment where it opens to the outside by means of anus.
In the 26th segment, the intestine gives off a pair of short, conical lateral outgrowths, the intestinal caeca which extend forward to 3 or 4 segments.
The characteristic feature of the intestine between 26 to 95 segments is the presence of an internal median fold of dorsal wall called "Typhlosole". These increase the effective area of digestion and absorption in the intestine.

Now let us find solution from given options:
1.Secrete digestive juice: In gizzard, food is grinded or pulverised thoroughly. Then in the stomach, calciferous glands neutralise humic acid present in it. Intestine is the principal site of digestion. Intestinal wall consists of glandular cells which secrete digestive juice containing digestive enzymes

2.Regulate the blood flow: In segment numbers 4, 5, 6 ,lying above pharyngeal mass, are found small, red-coloured, follicular bodies called blood glands. They are considered to produce blood corpuscles and haemoglobin.

3.Emulsify the food: Intestinal wall is made up of glandular cells which secrete digestive juice containing digestive enzymes which break down complex food into small absorbable units. These simpler molecules are absorbed through absorptive cells of intestinal epithelium, from here nutrients are passed to blood capillaries in the intestinal wall and are utilised inside the body.

4.Increase absorptive surface for digested food: An internal median fold of the dorsal wall that is usually termed as typhlosole is present in the intestine on segment number 26. This increases the effective area of absorption in the intestine. Typhlosole is a dorsal flap of the intestine that runs along most of its length, effectively forming a tube within a tube, and thereby increasing the absorption area by that of its inner surface.

Hence, the correct answer is option (D)

Note: It is to be noted that typhlosoles also showed its presence in bivalve molluscs like snails, lampreys, and echinoderms as for example starfish. Typhlosole in general is involved in increasing the surface area of absorption. The most important feature of the intestine between 26 to 95 segments is the presence of an internal median fold of dorsal wall called "Typhlosole".