Question

Archenteron cavity is found in
A. Blastula
B. Gastrula
C. Morula
D. Planula

Answer 1

The blastula is a hollow sphere of cells, or blastomeres, formed during embryo formation by repetitive cleavage of a fertilized egg. The blastula cells form an epithelial (covering) layer called the blastoderm, which encloses a fluid-filled cavity called the blastocoel. Embryonic development starts with a sperm fertilizing an egg cell to form a zygote, and then undergoes several cleavages to form a morula, a ball of cells.

Complete answer:
Option A: Blastula is a hollow sphere of cells, or blastomeres, formed during embryo formation by repetitive cleavage of a fertilized egg. The blastula cells form an epithelial (covering) layer called the blastoderm, which encloses a fluid-filled cavity called the blastocoel. As a result, option A is incorrect.

Option B: The gastrula cavity is the archenteron cavity, which is created by cell invagination. Gastrula is the stage at which morphogenetic movements and germ layer development occur. As a result, this is the right choice.

Option C: The cells on the outside and inside differentiate into trophoblast (outside) and inner cell mass (inside) progenitors, respectively. By the successful transport of sodium ions from trophoblast cells and osmosis of water, a cavity forms within the morula (early stage of blastocoel). As a result, this is the incorrect alternative.

Option D: There is no such thing as a planula point. As a result, alternative D is also wrong.

The archenteron, or digestive tunnel, is the rudimentary intestine that develops during gastrulation in the developing embryo. At the gastrula stage of development, it is the central cavity inside an embryo. Hence the correct answer is option B.

Note: The gastrula is trilaminate in triploblastic species ("three-layered"). These three germ layers are referred to as the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer) (inner layer). The gastrula is composed of only ectoderm and endoderm in diploblastic species such as Cnidaria and Ctenophora. The two layers are also known as the hypoblast and epiblast, respectively.