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Structure and Function of Animal Tissues

When we chew food, we can feel the movement of jaws activated by muscle tissue. Blood is circulated by connective tissue. Each system is activated by its specific tissues. Basically, all living organisms are composed of several distinct tissues. These may be classified into broad categories.


Types of Tissues
There are four types of tissues:

  • epithelial
  • connective
  • muscular and
  • nervous

a) Epithelial : -
Epithelial tissue consists of cells that cover the internal and external surfaces of the body. The presence of a cell secretion called the basement membrane.

It functions to protect and allow the secretion and absorption of substances out of and into the body.

The shape of the cells that make-up epithelial tissues are

(i) Squamous: Cells very thin, much wider than they are thick.
Simple Squamous Epithelium: Air sacs of respiratory and lining of blood vessels, heart and lymphatic tubes.
Stratified Squamous Epithelium: present in skin, vagina, esophagus, mouth.

(ii) Cuboidal: It forms the lining layer of microtubules in kidney, duct glands and ovary

(iii) Columnar: These cells can be arranged as a single layer called simple or into multiple layers called stratified or pseudo stratified. Epithelial cells may hold cilia or microvilli and can form glands that secrete their product into ducts or directly into the blood.

b) Connective : -
Connective tissue consists of cells dispersed in a non-cellular matrix of several types.
It functions to bind other tissue types and the organs together, provides support and protection, produces blood cells, and stores fat.
Cell Matrix composed of two regions

Ground Substance

  • Liquid (sol), Gel, Gum or solid


  • Non-elastic (= white fibers or collagen)
  • Elastic (= yellow fibers)


The types of connective tissue

(i) Loose Fibrous: Gel like ground with both elastic and non-elastic fibers running though the ground in many directions.

(ii) Dense Fibrous: Nuclei and fibers arranged in parallel rows.
proteins matrix forms tendons and ligaments.

(iii) Adipose: store fat globules. It contains large vacuoles and lipids.

(iv) Reticular: matrix has reticular (collagen fibres) and gives support to the lymphoid organs

(v) Cartilage: Cells are found in the lacunae within the matrix.

Fibers may be elastic or non-elastic, or a form of non-elastic called reticular (where the non-elastic fibers are very thin)

(vi) Bone - rigid, mineralized matrix

(vii) Blood - plasma matrix containing erythrocytes, leukocytes, and thrombocytes


c) Muscular Tissue
Muscular tissue consists of cells called muscle fibers.
Muscle fibers contain filaments of the proteins actin and myosin, which allow the cell to contract and relax to produce movement.


The types of muscular tissue

(i) Skeletal or Voluntary Muscle : Multi-nucleate, striated cells. Contraction of skeletal muscle fibers is under voluntary control. It is attached to bones via tendons.


(ii) Smooth or Involuntary Muscle : Single nucleus, spindle shaped cells, not striated. Contraction of smooth muscle fibers is involuntary. It is located in many internal organs and blood vessels.

(iii) Cardiac Muscle : Striated, branched cells. Contraction of cardiac muscle fibers is involuntary. It is located in the heart wall.


Smooth Muscle

Skeletal Muscle

Cardiac Muscle

d) Nervous Tissue
Nervous tissue consists of cells called neurons and neuroglea located in the brain, spinal cord, and nerves. Its function is to produce and conduct nervous impulses. These nervous impulses may be sensory (internal and external stimuli), integrative (within the brain and spinal cord), and motor (to muscles and glands).


Structure of  a Typical Neuron


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