Question

From an evolutionary point of view, which of the following tissues are the first to be formed in the course of evolution?

• A. Epithelial tissues
• B. Neural tissues
• C. Muscle tissues
• D. Connective tissues

Answer 1

The correct option is A Epithelial tissues

Epithelial tissues are also called epithelium. They are the first tissues to be formed during the course of evolution. They are the first to be formed in an embryo. These are large sheet of cells covering or lining all body surfaces. These cells sit on a basement membrane. They have a free surface. They are found in the conjunctiva of the eye. They form the lining of the hollow organs- inner lining of alimentary canal, inner lining of blood vessels, inner lining of respiratory system, inner lining of excretory system, inner lining of reproductive system, etc. It grows on other tissues. They have 3 surfaces- apical (towards the free surface), lateral and basal (towards the basement membrane). Cilia might be present on the apical surface- ciliated epithelium. They have a compact cell arrangement with little intercellular space and substances. These are generally avascular- no blood vessels are found. They receive oxygen and nutrients via diffusion.
Neural tissues contain special excitable cells called neurons which are the structural and functional unit of the nervous system. They carry impulses and are incapable of division as they lack centrioles. Neuroglial cells constitute the rest of the nervous system which do not carry impulses and are mainly protective and supportive in nature. They also provide nutrition and have the ability to divide.
Each muscle is made up of many long, cylindrical fibres arranged in parallel arrays. Actin (thin filament) and myosin (thick filament) are called myofilaments which together constitute the myofibrils. Myofibrils constitute to make muscle fibres which constitute to form muscle fasciculus which in turn form the muscle. They help in the movement of the body.
Connective tissues are the most abundant tissues in the body. They are present throughout the body. They are generally vascular (exception is cartilage which are avascular. Blood vessels don’t penetrate deep into cartilage). They link and support other tissues of the body.