2. Animal tissue
• The animal cells are grouped together to form animal
tissues. These tissues vary in their structure, function,
and origin. The animal tissues are divided into epithelial,
connective, muscular and nervous tissues. Let us have a
glimpse of each type of animal tissue in detail.
5. Epithelial Tissue
• Epithelial tissues form the protective covering and inner lining of the
body and organs. These tissues were the first to evolve during evolution
and were first formed during Embriyo development. They develop from
the ectoderm, mesoderm and endoderm of the embryo.
Characteristics of Epithelial Tissues
Following are the important characteristics of epithelial tissues:
1.These can be single-layered or multi-layered.
2.The tissues have the power to regenerate.
3.These are held together by gap junctions, tight junctions, zonula
adheren, desmosomes, or interdigitation.
4.The plasma membrane of these cells is specialized into flagella, cilia,
and microvilli.
6. Classification of Epithelial Tissues
Classification Function
Sensory epithelium To perceive stimuli
Glandular epithelium Secretes chemicals
Pigmented epithelium Imparts colour in retina
Absorptive epithelium For absorption
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7. Connective Tissue
• Connective tissues develop from the mesodermal cells of the embryo.
they support and bind other tissues in the body. These are made up of
three components:
• Intercellular Matrix: It is made up of mucopolysaccharide, specifically
hyaluronic acid.
• Cells: The major cells include fibroblasts, adipocytes, plasma cells and
mast cells.
• Fibres: Connective tissues are made up of three types of fibres,
namely, collagen fibre, elastic fibre, reticular fibre.
8. The connective tissues perform the
following functions:
1.They attach organs and tissues together.
2.They store fat in the form of adipose tissues.
3.They help in repairing tissues.
4.They prevent the organs from mechanical shocks.
5.The organs also help in defence.
9. Classification of Connective Tissues
Classification Function
Connective Tissue Proper Provides support and protection to
the body
Vascular Tissue Transport of materials in the body
Skeletal Tissue It supports the body and gives it
proper shape and form
10. Muscular Tissue
• The muscular tissue develops from the mesoderm of the embryo. It is
classified into three types:
• Cardiac
• Smooth
• Skeletal
11. Muscular tissue performs the following
functions:
1.It helps in movement and locomotion.
2.It supports the bones and other structures.
3.It is responsible for peristalsis and parturition.
12. Classification of Muscular Tissue
Classification Function
Cardiac It helps in blood circulation and keeps the heart
pumping
Smooth These help in peristalsis and other involuntary
functions of the body.
Skeletal Provide support, help in movement and maintain
homeostasis
13. Nervous Tissue
• Nervous tissue makes up the peripheral and the central nervous system.
It develops from the ectoderm of the embryo. It possesses the ability
to initiate and transmit the nerve impulse. Its main components include:
• Neurons – These are the structural and functional unit of nervous
system. It comprises an axon, cell body and dendrites.
• Neuroglia – These are special cells found in the brain and spinal cord.
They provide support to the neurons and fibres.
• Neurosecretory Cells – These function as endocrine organs. They
release chemical from the axons direcly into blood.