Question

Epithelial tissue originated from
A. Ectoderm
B. Endoderm
C. Mesoderm
D. All of the above

Answer 1

Hint:-Epithelial tissue is composed of cells that form protective sheets that cover the body surfaces, organs, and glands. Based on its location epithelial tissue is classified into- lining epithelium and glandular epithelium. Apart from protecting the body surfaces, glands, and organs; this tissue takes part in the absorption, secretion, and diffusion of certain molecules.

Complete Answer:-During human embryonic development after fertilization, the zygote undergoes mitotic divisions to form morula, blastula, and then gastrula. The gastrulation is the stage where the blastula undergoes mitotic division to form gastrula. Gastrula has three germ layers- ectoderm (external layer), mesoderm (middle layer), and endoderm (innermost layer).
All, except a select few multicellular organisms, are triploblastic (have all three germ layers). These three germ layers will develop into different organs, tissues, and all the other components of the body. The endoderm is the first layer that is formed from the embryonic disc. This germ layer forms the epithelial lining of the intestines, trachea, lungs, liver, gallbladder, vagina, prostate, etc.
Mesoderm is the second germ layer that is formed. The caudal end of the embryonic disc gives rise to the mesoderm. Mesoderm differentiates to form the organs of the excretory system, circulatory system, etc. Along with that it also forms the dermis of the skin, the lining of some internal organs, and also forms connective tissues.
The remaining cells of the embryonic disc differentiate and enclose the other two layers to form the ectoderm. The ectoderm forms the external structures of the body such as skin, hair follicles, the enamel of the tooth, the epidermal layer of sweat glands, cornea, external ear, etc. Epithelial tissue is formed by all three germ layers.

The correct option is (D).

Note:- Organisms such as cnidaria, ctenophores only have ectoderm and endoderm. These organisms are diploblastic. The differentiation of cells that occurs during embryonic development to form the germ layer and later on the tissues and organs is called morphogenetic movement. This movement is basically the change in the form of the cells and tissues.