Animal tissues

Tissue concept

            The body of an animal is made up of several kinds of cells. A group of cells that are similar in structure and origin, performing the same function is called tissue.

Types of tissues

                       There are several kinds of tissues in animals. they are 1. Epithelial tissue

2. Muscular tissue 

3. Nervous tissue 

4. Bone tissue 

5. Blood tissue

6. Reproductive tissue 

1. Epithelial tissue

            Epithelial tissue forms the covering of the body. It also lines the various cavities. Based upon their shape, function and arrangement, it is divided into six types namely, 1) Columnar epithelium  2) ciliated epithelium 3) Squamous epithelium 4) cuboidal epithelium 5) Glandular epithelium 6) Germinal epithelium.

2. Muscular tissue 

            The muscle cells, which are long and fibre like, are called muscle fibres. They possess the property of contraction and relaxation. There are three types of muscular tissues, namely a) Striped muscles c) Unstriped muscles and c) Cardiac muscles.

a. Striped muscles 

           Striped muscle cells are long and cylindrical. These muscles lie attached to the hand and leg bones. They help in movement.

b. Unstriped muscles 

        Unstriped muscle cells are small, spindle shaped with tapering

ends. They occur in the wall of the alimentary canal, blood vessels and urinary bladder.

c. Cardiac muscles 

       Cardiac muscle cells are short and branched. They have nucleus and number of stripes in the cytoplasm. The wall of heart is made up of cardiac muscle.

3. Nervous tissue 

       The nervous tissue is made up of neurons or nerve cells. These

are long and fibre like. They are also called as nerve fibres. Each nerve cell consists of a large cell body or cyton containing a distinct nucleus and branched processes called Derdrons or Dendrites. One of these processes is long and unbranched and is called axon. Brain and spinal cord are made up of nerve cells.

4. Bone tissue

           Bone tissue is strong and rigid and made up of a number of bone cells. The cross section of bone shows certain longitudinal canals called Haversian canals. Inside these canals, lie blood vessels and nerves. Surrounding each haversian canal there are many bone cells. Each bone cell lies in a space called lacuna. All the bone cells are connected with each other and with the haversian canals by narrow channels called canaliculi. The bone cells obtain  oxygen and food materials and get rid of waste materials through these canaliculi.

5. Blood tissue 

           Blood is the only tissue in the fluid form. Blood consists of a fluid matrix called plasma and solid components called the corpuscles. The blood cells are of three types. They are Red blood cells White blood cells and Platelets.

Plasma

       It is a clear, transparent, straw coloured fluid. It consists of 90% of water and 10% of dissolved substances like proteins, carbohydrates, salts, hormones, enzymes and antibodies.

         Red blood cells are circular, biconcave and disc shaped without any nuclei. They contain a pigment called hemoglobin. It gives red colour to the blood. They play an important role in the transportation of oxygen and carbon dioxide.

              White blood cells are irregular in shape, with a nucleus. They are colourless and exhibit amoeboid movement. They fight against the pathogen.

                 Platelets are small and colourless. They do not contain any nucleus. They plan important role in the clotting of blood.

6. Reproductive tissue 

          Testis is the male reproductive organ. It produces the sperms. The ovary is the female reproductive organ. it produces the ova. 

           The sperms are very active and motile. The ova contain the reserve food materials called yolk. They are non motile.