Question

What is the basic difference between epithelial tissue and connective tissue? Why are they so different despite the fact that all tissues originate in embryos and an embryo arises from a single fertilised egg cell?

Answer 1

Hint: Epithelial tissues can be found all over the body. They cover all body surfaces, line body cavities and hollow organs, and make up the bulk of gland tissue. Protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception are just a few of the activities they undertake.

Complete answer:
Epithelial tissue lines the cavities and the surfaces of organs and blood arteries throughout the animal body, whereas connective tissue supports, links, and separates many types of tissues and organs.
Connective tissue has a lot of matrix between the cells, whereas epithelial tissue has essentially none.
Differential gene expression is used to achieve tissue differentiation.
An organ's epithelial tissues either protect, cover, or line it. They may produce secretory glands in a modified state, as seen in the stomach and small intestine walls. Epithelial tissues are made up of a certain type of cell that is organised in one or more layers. The tissue is supported by a thin non-cellular basement barrier that prevents blood vessels from penetrating the epithelium directly. The exposed side of the epithelium may be ciliated, as seen in the lining of the trachea, oviduct, and other similar structures.
As skeletal tissue, packaging material, and most importantly, blood, connective tissues give support. A connective tissue's matrix might be solid, like in bones, or jelly-like, like in adipose/areolar tissue, or liquid, like blood. Collagen, elastin, and other fibres may be present in the matrix. In connective tissue, large blood arteries transport oxygen. Two or more types of cells can coexist in a single connective tissue, such as RBCs, WBCs, and Platelets in blood.
All of the distinctions across tissues are due to genetic differences. It's worth noting that while all connective tissues start from embryonic mesoderm, epithelial tissues might come from any of the germ layers.
Diverse cells accomplish different structural and functional properties by keeping many genes turned off and only expressing specific genes through protein synthesis. As a result, keratin protein is exclusively found in the epithelium of the skin and nowhere else in the body. Only the main cells of the stomach epithelium release HCl. Similarly, only blood lymphocytes create antibodies, only fibroblasts secrete tissue matrix fibres, only chondroblasts secrete cartilage components, and so on.
Tissue differentiation occurs early in the embryonic life cycle.

Note:-
Other tissues and organs in the body rely on this tissue for support, protection, and structure. Cells, fibres, and a gel-like material make up connective tissue. Bone, cartilage, fat, blood, and lymphatic tissue are all examples of connective tissue. BLOOD: Because it is made up of blood cells surrounded by a nonliving fluid matrix called blood plasma, blood is considered a connective tissue. Blood fibres are soluble protein molecules that become visible after blood clotting, making it the most unusual connective tissue. It's present in the walls of blood vessels.