Animal tissues are grouped under four main categories: epithelial, connective, muscular and nervous tissues.
Thin protective layer (or layers) of cells.
Generally located on the outer surface of the body, on the surface of the internal organs and the lining of the body cavities.
There are three distinct types of epithelial tissues namely Squamous, Cuboidal, Columnar Epithelium.
The muscular tissue consists of long, narrow cells called muscle fibres. Muscle fibres are the muscle cells. They are so named because of their long fibre like shape. Muscles bring about movement of body parts and locomotion in organisms.
Types of Muscular Tissue
In human beings, three types of muscles are present - Striated muscles, Unstriated muscles and Cardiac muscles.
(a) Striated muscle (b) Unstraited muscle (c) cardiac muscle
Connective tissue, as the name suggests, connects organs. Basically, connective tissue has matrix, connective tissue cells and connective tissue fibres. Example of connective tissue are areolar tissue, adipose tissue, cartilage, bone and blood.
Functions of Connective Tissue
It binds different structures with one another, e.g. Tendons bind bone to a muscle; ligaments connect bones.
It forms a supporting framework. e.g. cartilage and bones in the body.
Adipose connective tissue helps in storage of fats. It also forms shock-proof; cushions around kidneys, ovaries and eyeballs.
Blood is also a connective tissue.
Nervous tissue consists of nerve cells or neurons. A bundle of nerve fibres or axons of nerve cells forms nerves. A nerve cell or neuron is a structural and functional unit of the nervous system. A typical nerve cell consists of the following parts:
Cell body or cyton has a prominent nucleus and cytoplasm, cell organelles like mitochondria, golgi-bodies, etc. are also present in the cytoplasm.
Several thread like extensions called dendrons arise from the cell body. One of them is long and called axon. The axon may be or may not be covered by myelin sheath or medullary sheath. This sheath is constricted at intervals which are known as nodes of Ranvier.
The space between axon endings of one nerve cell and the cell body or cyton of another nerve cell is the synapse.