CBSE
Class 10 Class 12
Animal tissues are of four types, viz. epithelial tissue, connective tissue, muscular tissue and nervous tissue.
The cells of a connective tissue are loosely scattered in matrix. The matrix can be a fluid, jelly-like, dense or rigid. The nature of matrix depends on the function a connective tissue serves. Following are the various connective tissues:
Areolar (Loose) Connective Tissue
Areolar tissue is found between skin and muscles, around blood vessels and nerves and in bone marrow. Areolar tissue fills the gap between tissues and provides support. It also helps in repair of tissues.
Dense connective tissue(Fibrous connective tissue)
It has thicker, denser fibres and fewer cells. The matrix is made up mostly of collagen fibres, with fibroblasts arranged in rows. This type of connective tissue forms tendons and ligaments, which attach muscle to bone and bone to bone, respectively.
Adipose Tissue
Adipose tissue is composed of fat globules. This tissue is found below the skin and beneath the organs. Adipose tissue provides insulation and works as a cushion.
Bone
Bone is mainly composed of osteoblasts. Bone makes the skeletal system. The skeletal system is responsible for providing a structural framework to the body. It provides protection to important organs and facilitates movements.
Cartilage
Cartilage is mainly composed of chondrioblasts. Cartilage is present at the ends of articulatory bones. Cartilage is also present in the external ear, bronchii, etc.
Blood
Blood is composed of blood cells, platelets and plasma. Blood plays an important role in the transportation of various substances in the body. It also helps in osmoregulation and temperature control.
The epithelial tissue forms the covering or lining of most of the organs. The cells of the epithelial tissue are tightly packed and form a continuous sheet. There is a small amount of cementing materials between the cells and no intercellular space is present. The permeability of the epithelial tissue plays a great role in the exchange of materials among various organs it also plays an important role in osmoregulation. All epithelial tissues are separated by the underlying tissue by an extracellular fibrous basement membrane. Epithelial tissues are of following types:
Muscular tissue is composed of muscle cells. Muscle cells are specialized cells which have the capability to contract and expand. Due to contraction and expansion, muscles facilitate various kinds of movements in the body. Muscular tissues are of three types:
Striated Muscles
The cells of striated muscles are in the form of long, unbranched fibres. Cells are multinucleate. Light and dark bands (striations) are present on muscle fibres; which gives the name striated muscles. Striated muscles are found in those organs where voluntary movement is possible, e.g. hands, legs, back, neck, etc.
Smooth Muscles
The cells of smooth muscles are spindle-shaped and each has one nucleus. Smooth muscle is found in those organs where involuntary movement is possible, e.g. alimentary canal.
Cardiac Muscles
The cells of cardiac muscles are in the form of branched fibres. Striations are present and cells are uninucleate. These are found in the heart. Cardiac muscles are capable continuous contraction and relaxation throughout the life.
All cells possess the ability to respond to stimuli. However, cells of the nervous tissue are highly specialised for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body. The brain, spinal cord and nerves are all composed of the nervous tissue. The cells of this tissue are called nerve cells or neurons. A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise.
Usually, each neuron has a single long part, called the axon, and many short, branched parts called dendrites. An individual nerve cell may be up to a metre long. Many nerve fibres bound together by connective tissue make up a nerve.
