Tissues are group of cells which are similar in structure and performs a particular function.
Animals are multicellular organism (organism which have more than one cell), animals have billions of cell. This cells are grouped to perform a unique function and this group is called as tissues. And this tissues are grouped and creates an organ. Animals possess different organs and thus have different types of tissues.
Types of animal tissue:
Epithelial tissue is the covering tissue. It covers most organs and cavities within the body. It also forms a barrier to keep different body system separate. Epithelial tissue are tightly packed and forms a continuous sheet. They don’t have any intercellular spaces only a small amount of cementing material is present between them. The skin, the lining of the mouth, the lining of blood vessels and kidney tubule all are made of epithelial tissue. Obviously anything entering or leaving must have to cross at least one layer of epithelial tissue. As a result permeability of epithelia plays an important role in exchanging of material. On the basis of their structure and function different types of epithelial tissues are present.
Squamous epithelial cell: This are extremely thin and flat and form a delicate lining. The oesophagus, lining of the mouth are covered by it. the skin which protects the body is also made of squamous epithelial.
Cuboidal epithelium: It is a cube shaped epithelial cell which forms the lining of kidney tubules and ducts of salivary glands in order to provide them mechanical strength.
Columnar epithelium: This are tall epithelial cells which are present in the inner lining of the intestine. They have a hair like projection on their outer surfaces called as cilia. These cilia can move and their movement pushes the mucus forward to clear it.
Connective tissue maintains the form of the body and its organs. It provides support and connection between organs. The cells of connective tissue are loosely spaced and embedded in an intercellular matrix. The matrix may be like jelly, fluid, dense or rigid. Blood is a type of connective tissue. It has a fluid matrix called plasma in which RBC’s, WBC’s and platelets are suspended. Blood flows and transports gases, digested food, hormones and waste material to different parts of the body. Bone is another example of connective tissue. It forms the framework that supports the body. It also anchors the muscles and supports the main organs of the body. Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
Muscular tissue is responsible for the movement in our body. Muscles contain special proteins called contractile proteins which contracts and relax to cause movement. On the basis of their control muscle tissue can be classified into three types: smooth, cardiac and skeletal muscle tissue.
Smooth Muscle: Smooth muscles are involuntary muscles because we cannot start them or stop them by our will. This muscle activities are self controlled and need no attention. These are found in the iris of the eye, in ureters, and in the bronchi of the lungs. This cells are long with pointed ends and uninucleate.
Cardiac Muscle: This involuntary muscles were present in the heart. It shows rhythmic contraction and relaxation throughout the life. This are cylindrical, branched and uninucleate.
Skeletal Muscle: Skeletal muscles are voluntary muscles which we can move by conscious will. The cells of this tissue are long, cylindrical, unbranched and multinucleate. This muscle shows alternate light and dark bands on its surface or striation and as a result they are also called as striated muscles.
Nervous tissue is highly specialized in receiving and conducting impulses from one place to another within the body. The brain, spinal cord and nerves all are composed of the nervous tissue. The cells of this tissue are called neurons.
A neuron consists of a cell body with a nucleus and cytoplasm from which long thin branches arises. Usually each neuron has a long part called the axon, and many short branched parts called dendrites.