Tissues

The human body is a structural skeleton made up of bones that are covered with deep layers of skin. But, if we closely observe and go into the details, it also contains various cellular organizational levels between the cells and organs of the body, known as tissues. Tissues are made up of a group of specialized cells which perform particular functions. These tissues collectively form organs. The word tissue is derived from an old French verb, ‘tissu’, which means “to weave”. The study of tissues is known as ‘histology’ which deals with humans and animal-related tissue. Also, the study relating to diseases concerning tissues is known as ‘histopathology’.

Tissue and its Types

Classification of tissues can be done in two parts, first is animal tissues, and the second one is plant tissues. Both these types have their subtypes; that is, there are different types of animal and plant tissues as well.

Different Types of Animal Tissues

The function of animal tissues differs from organism to organism. There are four types of animal tissues-

1.     Connective Tissue

Connective tissues are those tissues that help in maintaining the form of the organism’s body as well as its organs. These tissues also provide internal support to the body. They help in holding the organs together. They also resist the entering of pathogens in the body. These tissues also help in the transportation of nutrients, hormones, gases, wastes from one part to another part of the body. There are various forms of connective tissues, such as bone ligaments, tendons, cartilage, etc. Connective tissues can be further divided into fibrous, fluid, and skeletal connective tissue.

The composition of all types of connective tissues is similar. They are mainly composed of extracellular fibers, amorphous matrix, and stationery as well as migrating cells. Skeleton in the human body is one example of connective tissue.

2.     Muscle Tissue

Muscle tissues, as the name suggests, helps in the movement of the body. They produce force and generate motion for the movement of the body as well as movement inside organs. There are three types of muscle tissues; mainly, they are skeletal, cardiac, and visceral or smooth muscle tissue. The main functions of muscle tissues include assisting various body movements such as running, lifting, jumping, picking, etc. They help in maintaining the position and postures of the body. They are associated with voluntary as well as involuntary movements. Involuntary muscle tissues play an important role in pumping blood and its regulation in arteries. It also helps in the inhaling and exhaling of air from the body.

3.     Nervous Tissue

The tissues that are mainly associated with the central nervous system are known as nervous tissue. They are mainly found in the brain and spinal cord. This tissue is responsible for the communication network inside the body. It plays an important part in the processing of information.

It is also responsible for the response to stimuli and transmits information inside the body. It plays an important role in managing emotions, reasoning skills, and memory of an organism. 

4.     Epithelial Tissue

These are the tissues that cover outer parts of the body organs such as the skin, the digestive tract’s inner lining, etc.

Epithelial tissues play a major role in an organism’s body. They perform various functions such as act as a sensory reception, helps in filtration and certain other metabolic activities as well. It also helps in various processes like diffusion and secretion. Epithelial tissues protect internal organs from pathogens as well. These tissues help in the secretion of various enzymes, mucus, hormones, and much more.

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Different Types of Plant Tissues

There are two criteria on which plant tissues have been classified. The first is based on the parts of plants, and the second is based on types of cells.

Based on parts of plants, plant tissues are:

• Epidermis Tissues – Outer surface of leaves are made up of these tissues.

• Vascular Tissues – They help in the transportation of nutrients and other fluids.

• Ground Tissues – These tissues assist in producing nutrients through the process of photosynthesis.

 Based on types of cells, plant tissues are classified as-

• Meristematic Tissues

This type of cell is made up of cells that keep on actively dividing themselves, which results in increasing the length as well as the thickness of the plant. Further, meristematic tissues can be divided on the basis of their position on the plant, their functions, their origin, and development.

Three types of meristematic tissues are Apical, Lateral, and Intercalary.

• Permanent Tissues

These tissues are a group of cells that are similar in several things, such as their origin, structures, and various functions. They help in the complete growth of plants. There are many functions of these tissues, such as they help in floating to aquatic plants. They also help in the storage of starch, fats, oils, and proteins. They are carriers of chloroplasts also.

Permanent tissues are further divided into simple, complex, and secret permanent tissues.

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