Question

Body cavity lined by mesoderm is called as
A. Coelenteron
B. Pseudocoel
C. Coelom
D. Blastocoel

Answer 1

Hint: When the body cavity is completely lined with mesoderm, the body cavity is called a true coelom and the animals are called coelomates. When the coelom is not completely lined by mesoderm, the body cavity is called pseudocoelom and the animals are called pseudocoelomates.

Complete answer:
In the embryonic stage, three germs layers are found. A germ layer made up of many cells, they interact with each other during embryo development and contribute to the formation of all organs of the body. These three germ layers are: Ectoderm, Endoderm and Mesoderm. Ectoderm is the outermost layer, Endoderm is the innermost and mesoderm is present between these two layers. In some animals, only two layers are present: Ectoderm and Endoderm. These animals are called diplomatic animals. For example Cnidarians. Those animals in which all three layers are present are called trophoblastic animals. For example Chordata.

In most animals, body cavity forms from these three layers, which is lined by mesoderm epithelial cells. This body cavity is called coelom. On the basis of coelom, the animals are divided into three categories:
Acoelomates (No coelom),
Pseudocoelomates (false coelomates)
Coelomates (true coelomates).

We have four options: Coelenteron, Pseudocoel, Coelom, and Blastocoel.
- Coelenteron is the internal cavity of Cnidarians and mesoderm is absent in Cnidarians.
- Pseudocoel is the body cavity which is partially lined by mesoderm.
- Coelom is a body cavity which is completely lined with mesoderm.
- Blastocoel is the cavity within the blastula that forms during blastulation.

Hence, the correct answer is option (C).

Note: Coelom is a body cavity present between the somatic mesoderm and splanchnic mesoderm. In mammals, this body cavity subdivided into the pleural, pericardial, and peritoneal cavities, containing the thorax, heart, and abdomen, respectively.