Human body has 4 different types of tissues.
Tissue in simple terms is a bunch of similar cells.
They are formed by a combination of same cells so have same function in body.
Certain type of tissue has same function in almost all of the higher animals.
These tissues together form the organs in the body.
Tissues serve many purposes in the body. They appear to be differentiated in-order to carry these special physiological functions.
Based on their physical structure and function, tissues of the body are differentiated as
Types of tissues
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue.
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Epithelial tissue: This tissue is an upper most tissue covering all the organs or body. This tissue based on need is of different types as simple epithelium, squamous epithelium, columnar epithelium etc.
This is further classified as
- Simple epithelium
- Stratified epithelium.
Simple epithelium is one which has a single layer of epithelial cells. It is present at sites where filtration or diffusion of substances is necessary. It is found in the nephron of kidney for filtration of blood, for diffusion of oxygen from lungs to blood. This type of single layer of epithelium is so thin and offers least resistance for transfer of molecules from one side to another.
Based on the shape of cells in this layer, it is further differentiated as simple squamous epithelium, simple cuboidal epithelium and simple columnar epithelium.
Stratified epithelium is a multi layered epithelium. This is differentiated based on the upper most layer and also the shape of cells in bottom layers.
The upper layer cells might be keratinised, dehydrated to protect from heat, microbes, wear and tear, chemicals etc. This type of layer is seen in skin.
In most other types of stratified epithelium, the upper layer is non-keratinised.
Based on the shape of lower layer cells, the epithelium is again differentiated as stratified squamous epithelium, stratified cuboidal epithelium, columnar stratified epithelium and psuedostratified columnar epithelium.
There is another type called transitional epithelium. This type of tissue is present in urinary bladder. The Cells are cuboidal or columnar in relaxed state. But when there is load, they stretch and become flat to accommodate the substance (urine).
There is one more type of epithelium i.e. is glandular epithelium which are present in glands.
Types of simple epithelium tissues:
- Simple squamous epithelium: As the name indicates, this is a single layer of squamous shaped epithelium cells.
2. Simple cuboidal epithelium has single layer of cuboid shaped cells.
3. Simple columnar epithelium has single layer of long column shaped cells
Types of Stratified epithelium tissues:
- Stratified squamous epithelium has squamous shaped cells arranged in multiple layers.
2. Stratified cuboidal epithelium has cuboidal cells in multiple layers
3. Stratified columnar epithelium with column shaped cells in layers
4. Psuedo-stratified columnar epithelium: Single layer of columnar shaped cells arranged in such a way to give false impression of multiplayer.
Connective tissue: This tissues as the name indicates, is in connecting position in between tissues. This is many types like adipose tissues, reticular tissue etc.
This connective tissue is divided as
- Loose connective tissue. (Areolar tissue, adipose tissue)
- Dense connective tissue.
- Cartilage tissue
- Bone tissue
- Liquid connective tissue (examples of tissue is blood, W.B.C’s, lymph)
Muscular tissue: As the name indicates, this tissues makes muscles of the body. This tissue is of 3 types as
a) Skeletal muscle tissue
b) Cardiac tissue
C) Smooth muscle tissue
Striated muscles are present attached to skeletal system, especially long bones. They also have bands or striation along the length. They are voluntary i.e. they are under the control of our will. They help in movement from one place to another.
Cardiac muscles are present in the heart. They like skeletal muscles have striations in them. But the difference is, they have branches. This muscle helps to pump blood by the heart.
Smooth muscles are spindle or cone shaped in structure. They help in contraction and relaxation of man organs like lungs, stomach, uterus etc.
They help in movement, contraction and other physiological activities. They are involuntary in nature. They are controlled by brain.
Nervous tissue: This tissue is mostly present in the entire nervous system including brain and spinal cord. It has two types of tissue as nervous cell and neuroglia.
The nerve cells are the longest cells in the body. They can be up to few meters. They transmit impulses from brain to other body parts and vice-verse. This tissue controls the whole body by conduction of impulses across the body. The tissue operates by use of bio-molecular chemical substances called as neurotransmitters.
Neuroglial tissue is a binding tissue around the neurons. It helps to protect the nerve cell from damage. Unlike other cells, these cells does not multiply. They are formed during birth and last till death. If there is any damage to them in between, it can lead to loss of their function for ever.
Reference: Principles of Anatomy and Physiology.