Cells are the fundamental unit of life. When a group of cells teams up to perform a specialized function, the group of cells is called a ‘Tissue’. All cells in a tissue are of similar shape and size, working in tandem to accomplish their designated function.
Types of Tissues in the Human Body–
In the human body, cells are organised into four different types of tissues. These are-
- Epithelial tissue
- Muscular tissue
- Nervous tissue
- Connective tissue
Epithelial tissue consists of tightly packed cells, which form a protective covering running throughout the body as part of the skin, or as lining inside all the organs of the body, including the kidneys, intestines, stomach, oesophagus, trachea, etc.
Epithelial tissues consist of cells of different shapes, depending on their location and function. They can be flattened, to form squamous epithelium, cubical, to form cuboidal epithelium or columnar, to form columnar epithelium.
Functions of epithelium-
- It protects the internal parts of the body from injury, dehydration or entry of bacteria.
- When lining the stomach wall, it performs the function of secretin of digestive juices.
- The epithelium in the skin helps in the removal of waste in the form of sweat.
- As lining of the intestines, the epithelial tissue helps in the absorption of nutrients from the digested food.
Muscular tissue consists of elongated cells which together bring about movement in the body or its parts. These cells exhibit the property of contraction and relaxation, which helps in the movement of the muscles.
Muscular tissue is found in every part of the body where movement is involved. Even the rhythmic expansion and contraction of the heart, the contraction and expansion of the stomach and intestines during digestion, the contraction and relaxation of the urinary bladder during excretion, is brought about by muscular tissue.
Muscular tissues are of three types, depending on their functions and location- voluntary muscles, attached to the skeleton, which are striated; involuntary muscles, found in the internal organs, which are non-striated or smooth muscles; cardiac muscles, found in the heart.
Functions of Muscular Tissue-
- Voluntary or skeletal muscular tissue helps in the movement of various body parts, to perform functions such as running, jumping, writing etc.
- Involuntary muscular tissue helps in the contraction and relaxation of organs, thus helping in breathing, digestion, etc.
- Cardiac muscular tissue helps in the contraction and expansion of the heart, thus helping in pumping blood to the entire body.
Nervous tissue consists of a group of specialised cells called nerve cells or neurons. These cells are found in the brain and the spinal cord. Each nerve cell consists of three parts-
- Cell body or cyton
- Dendrites, which are short branch like structures that arise from the cell body
- Axon, which is a tubular structure with fine terminal nerve endings.
Functions of the Nervous Tissue-
- Nerve cells are joined end to end forming long nerve fibres.
- Nerve fibres conduct messages throughout the body.
Connective tissues are found throughout the body. They consist of cells suspended in a solid, liquid or jelly-like material, known as matrix. Connective tissues support or connect other tissues.
Depending on their functions, structures and locations, connective tissues can be divided into the following three types-
- Connective Tissue Proper- these consist of-
- Areolar tissue- which binds the skin with underlying parts
- Adipose tissue- which stores fat and keeps the body warm.
- Tendon- tough, non-elastic tissues which connect muscles to bone
- Ligament- strong, elastic tissues which connect one bone to another bone