Tissue.

• Tissues are groups of cells that work together to carry out a specific function.
• Epithelial tissue covers the body's surfaces, lines cavities, and forms glands.
• Meristematic: a region of plant tissue consisting of actively dividing cells forming new tissue.
• Meristematic tissue has a dense cytoplasm, thin cell wall, prominent nucleus, and no vacuole.
• Lateral meristematic tissue is found at the sides of the stem and is responsible for the growth in width of the stem.
• Intercalary meristematic tissue is found between nodes and helps the plant in branching.
• Apical meristematic tissue is found at the tips of shoots and roots and is responsible for the elongation of shoots and roots.
• Permanent tissue arises from meristematic tissue. They are made of dead cells and have definite shapes and sizes.
• The process in which meristematic tissue is converted to permanent tissue is known as differentiation.
• Parenchyma is a type of simple permanent tissue, that is found in the leaf, flower, fruit, and stem of the plants and helps in support and storage.
• Parenchyma tissue has living cells that are loosely packed together. It has a thin cell wall and intercellular space is present.
• Collenchyma is a type of simple permanent tissue, that is found in the branches and leaves of plants and helps in making the plant flexible.
• Sclerenchyma is a type of simple permanent tissue, that is found in the seed or nut of the plants and helps in giving mechanical support.
• Collenchyma tissue has living cells that are tightly packed together. It has a cell wall in which the corners are thick, and intercellular space is absent.
• Sclerenchyma tissue has dead cells that are tightly packed together. It has a thick cell wall and intercellular space is absent.
• When parenchyma contains chlorophyll and is able to photosynthesize, it is known as chlorenchyma.
• When parenchyma contains air cavities, it is known as aerenchyma
• Complex, vascular, or conducting permanent tissue are made up of more than one kind of cell.
• Xylem: the vascular tissue in plants that conducts water and dissolved nutrients upwards from the root and also helps to form the woody element in the stem.
• Phloem: the vascular tissue in plants that conducts sugars and other metabolic products downwards from the leaves.
• Xylem tissues are made of xylem parenchyma, xylem fiber, xylem vessel, and tracheids (conducting element).
• Phloem tissues are made of phloem parenchyma, phloem fiber, companion cell, and sieve tube (conducting element).
• Animal tissue is of four types; epithelial, connective, muscular, and nervous tissue.
• Simple squamous epithelial tissue is found in the lining of the mouth and oesophagus. Its cells are extremely thin and flat.
• The topmost part of the skin, the epidermis, is made of squamous epithelial tissue, but here the cells are stacked and thus the tissue is known as stratified squamous epithelial tissue. It protects the body from microorganisms and against water loss.
• Cuboidal epithelial tissue is found in the kidney, pancreas, and salivary glands. It provides mechanical support.
• Columnar epithelial tissue is found in the inner lining of the small intestine. It helps in absorption and secretion.