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Introduction
A tissue is a collection of cells which share common origin, similar basic structures and perform the same function in an organism.Tissue is a biological organizational level between cells and an organ. A tissue is a collection of cells and extracellular matrix from the exact origin.
The word ‘tissue’ comes from the French word ‘tissu’, the past participle of the verb tisser, which means ‘to weave.’
Histology is the branch of Biology that deals with the study of tissues. In the case of disease or histopathology also tissues are studied. In 1801, Xavier Bichat introduced the term ‘tissue’.He is also known as ‘The Father of Histology.’
When different types of tissues come together to perform a particular function then an organ is formed. Hence, an organ comprises different types of tissues.
Types of Tissues
In animals there are different types of tissues. These vary in structure, composition and function.There are four basic types of tissues in animals:
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nerve tissue
- Epithelial Tissue : It is one of the four primary forms of body tissue.It covers external surfaces of all body organs as well as the entire external body. It also lines the cavity of all hollow organs of the body. There are varieties of epithelial tissue based on the diverse forms and types.Chiefly epithelial tissue is divided into two categories
- Simple epithelial tissue
- Compound epithelial tissue
Simple epithelial tissue is of single cell thickness while compound epithelial tissue is multi cell thick.
Few type of simple epithelial tissues are explained below-
| Example of Epithelial Tissue | Characteristics |
| (1) Simple Squamous Epithelium | Surface-lining tissues made up of a single layer of irregular cells or squamous cells. The nucleus of squamous cells is spherical, and it is big, thin, and flat. These can be found everywhere, from capillaries to lungs’ alveoli to kidney nephrons, etc. Functions –
|
| (2) Pseudostratified columnar epithelium | Column-like cells of varying heights give the impression of many layered arrangement though are single layered in any epithelial lining.Because the cells are not the same size and all do not reach the tissue’s apical surface.Thus is named pseudostratified columnar epithelium (stratified epithelium is many layered).Based on a cellular organelle engaged in motility and sensory activity, these tissues can be categorized as ciliated or non-ciliated. This type of epithelium lines your upper respiratory tract and is characterized by a large number of cilia. Functions – Present in areas where it is necessary to generate mucus to catch foreign materials and sweep them away with the help of cilia or movements of substances.For example vas deferens and epididymis, where the epithelia have a dual function of secretion and absorption. |
| (3) Simple cuboidal epithelium | It is found in glandular (secreting) tissue and kidney tubules. |
| (4) Simple columnar epithelium: | This form of the epithelium has apical cilia or microvilli and is often specialized for absorption. Your stomach and intestines are lined with these cells. |
Goblet Cells– Many of the cells in simple epithelial tissue turn into pitcher-like called goblet cells.These are mucus-secreting unicellular glands. They also have short basal cells with apical surfaces that do not reach the lumen.
2. Connective tissue : It is a collection of cells which lie in a ground substance called matrix.Extracellular fibers, an amorphous matrix called ground material, and stationary and migratory cells make up all connective tissue forms.
In the human body this tissue helps to maintain the shape of the body organs.It offers support to the internal organs by binding them to the body wall and preventing the dislocation of internal organs. Examples of connective tissue are bone, ligaments, tendons, cartilage,areolar and adipose tissue .
A brief description of adipose tissue is given below:
It is also known as fatty tissue, primarily made up of fat cells (adipocytes), which are specialized to generate and contain vast globules of fat and are surrounded by a structural network of fibers.
It is mostly found beneath the skin, although it can also be found in deposits between muscles, the intestines, and their membrane folds, around the heart, and elsewhere. It’s also found in the marrow of the bones.
3. Muscular Tissue– This tissue is composed of a special type of protein which is contractile in nature. Muscle tissue is divided into three categories-
- Voluntary muscles
- Involuntary muscles
- Cardiac muscles
Voluntary muscles work according to our will and are present in limbs, abdomen.etc. Involuntary muscles do not work according to our will and are found in all visceral organs. Cardiac muscles are found only in the heart and can work tirelessly.
It is generally attached to the same nerve bundles and works as a single unit—the muscle contracts in response to a nerve impulse from the brain or another external stimulus.
4. Nerve Tissue- Despite the complexity of the nervous system, nerve tissue has only two types of cells. The neuron is the actual nerve cell. Neuroglia, often known as glial cells, is the other cell type. This tissue is found in the organs of the nervous system of our body like brain and spinal cord.
Conclusion
Tissue provides structural and mechanical support and demonstrates division of labor.
Study of tissues is helpful in disease diagnosis and classification. Tissue is significant because it aids in the study of illness progression, the determination of prognosis, and the identification of the most effective treatments for various diseases. It has made a substantial contribution to the medical industry’s advancement.
