Animal Tissues:
In multicellular organisms, a group of similar cells with intercellular substances perform a specific function, such as an aggregation of cells is called tissue. Animal Tissues are groups of animal cells of similar origin and performing similar functions.
Types of Animal Tissues:
Animal Tissues are of four different types:
1. Epithelial Tissue: The tissue forms the outer and inner covering of our body and its different organs. The covering must vary according to its location and function. If the epithelial tissues are made up of a single cell layer, they are called the simple epithelium, if they are multilayered they are called the stratified epithelium. The cells of the simple epithelium may be flat, scaly, squamous, cubical having similar length, breadth, and thickness, and columnar, having column-like cells, with greater height than their breadth. Some cells may be ciliated and some are glandular, capable of secretion.
2. Connective Tissue: Connective Tissue consists of two basic elements:
i. Extracellular matrix: The matrix consists of protein fibers and ground substance. The extracellular fiber is secreted by connective tissue cells. The connective tissues usually have a rich blood supply.
ii. Cells of connective tissue: The cells include fibroblasts, macrophages, plasma cells, mast cells, adipocytes, white blood cells, etc.
3. Muscular Tissue: Muscular tissues consist of elongated cells walled muscle fibers or myocytes that can use ATP to generate force. Based on their location and function, muscular tissue is classified into three types:
i. Skeletal Muscle: These fibers are long cylindrical, and striated with multi-nucleated cells.
ii. Smooth Muscle: These fibers are without striation and with spindle-shaped cells containing a single central nucleus.
iii. Cardiac Muscle: These fibers are branched, striated, and usually with one centrally located nucleus.
4. Nervous Tissue: Nervous Tissue is composed of (i) Neurones (nerve cells) which consist of the cell body and processes extending from the cell body. and (ii) Neuroglia which don’t generate or conduct nerve impulses but have other important supporting functions.