Tissue: Definition, Types, and Examples

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Tissue Definition

Tissues are collections of cells with a similar structure that work together to execute a certain task. The term tissue is derived from an old French verb that means “to weave.” Animal tissues are divided into four categories: connective, muscular, nerve, and epithelial.

There are three types of tissues in plants: vascular, ground, and epidermal. Organs in the body, such as the brain and heart, are made up of groups of tissues.

Types of Animal Tissue

i. Connective Tissue

Connective tissue is a type of tissue that links or divides groupings of other tissues. It is situated between all of the body’s other tissues and organs.

Cells and ground material, a gel that surrounds cells, make up connective tissue. Except for lymph and blood, most connective tissue comprises fibres, which are long, narrow proteins.

Collagenous fibres link bones to tissues; elastic fibres allow organs like the lungs to move; and reticular fibres give cells physical support. Oxygen can also pass from blood arteries into cells through connective tissue.

A connective tissue disease affects around one out of every ten people. Sarcomas, Marfan syndrome, lupus, and scurvy, a Vitamin C shortage that causes weak connective tissue, are all connective tissue diseases.

ii. Muscle Tissue

All of the muscles in the body are made up of muscle tissue, and the specific nature of the tissue is what permits muscles to contract. Skeletal muscle, cardiac muscle, and smooth muscle are the three kinds of muscular tissue.

Skeletal muscle permits the body to move by anchoring tendons to bones. The heart contains cardiac muscle, which contracts to pump blood.

Smooth muscle may be found in the intestines, where it aids in the movement of food through the digestive tract, as well as other organs such as blood vessels, the uterus, and the bladder.

Skeletal and cardiac muscles are striated, which means they have sarcomeres (muscle tissue units) that are organised in a regular manner. Sarcomeres do not exist in smooth muscle.

A muscle tissue disease such as Duchenne muscular dystrophy is one example. It’s a hereditary condition in which muscles atrophy over time. As muscles atrophy, they shorten, resulting in scoliosis and immobile joints.

Because the gene that causes the disease is on the X chromosome, most people who have it are men (of which males have only one).

iii. Nervous Tissue

The brain, spinal cord, and peripheral nerves are all components of the nervous system and contain nerve tissue. It is made up of nerve cells called neurons and cells called neuroglia that assist in nerve impulse travel.

Gray matter and white matter in the brain, and nerves and ganglia in the peripheral nervous system, are the four kinds of nervous tissue. The primary distinction between grey and white matter is that grey matter neurons have unmyelinated axons, whereas white matter neurons have myelinated axons.

Myelin is a fatty white substance that insulates neurons and is essential for nerve activity. The destruction of nerve tissue causes the symptoms of Alzheimer’s disease, such as memory loss, mood changes, and disorientation.

Amyotrophic Lateral Sclerosis (ALS) is another illness in which nerve tissue degenerates over time, resulting in the loss of higher brain functions.

Multiple sclerosis, in which the immune system attacks and destroys nerve tissue, Huntington’s disease, in which an abnormal protein causes neuron death, and Parkinson’s disease, in which the part of the brain that controls movement is impaired because not enough dopamine is produced, are among the other nervous tissue disorders.

iv. Epithelial Tissue

The epithelium, or epithelial tissue, covers the surfaces of organs such as the skin, the trachea, the reproductive tract, and the inner lining of the digestive tract.

It helps protect organs by forming a barrier, as well as absorbing water and nutrients, eliminating waste, and secreting enzymes or hormones. All of the glands in the body are made up of epithelial ingrowths.

Eczema and psoriasis, both of which produce rashes, are examples of epithelial tissue disorders. A carcinoma is a malignancy that originates from epithelial tissue.

Asthma, which is characterised by inflammation of the airways and shortness of breath, is also caused by epithelial cells in the airways.

Types of Plant Tissue
i. Vascular Tissue

Plants use vascular tissues to transfer chemicals from one area of the plant to another. Xylem and phloem are the two kinds of vascular tissue. Phloem carries organic molecules that the plant utilises as food, mainly sucrose, whereas xylem transports water and certain soluble minerals.

Long and thin vascular tissues create cylinders through which nutrients are carried like pipes. Two types of meristems, which are tissues that contain undifferentiated cells that are employed throughout a plant’s growth, are also associated with vascular tissue.

The cork cambium and the vascular cambium are meristems that accompany vascular tissue. The growth of the plant’s vascular tissues is linked to these meristems.

ii. Ground Tissue

All cells that aren’t vascular or dermal make up ground tissue (having to do with the epidermis; see below). Ground tissue is divided into three types: parenchyma, collenchyma, and sclerenchyma.

Photosynthesis, storage of carbohydrates, lipids, oils, proteins, and water, and healing of injured tissue are all activities performed by parenchyma cells, which make up the “filler” tissue of plants.

The plant’s structural support is provided by collenchyma tissue, which is made up of long cells with unusually thick walls. Plants that thrive in windy environments have thicker collenchyma tissue walls.

Sclerenchyma is a type of supporting tissue made up of dead cells. Fibres and sclereids are two kinds of sclerenchyma. Sclereids are star-shaped cells with strong cell walls, whereas fibres are long, thin cells. Fabrics made from Sclerenchyma fibres consists hemp and flax.

iii. Epidermal Tissue

The epidermis is a single layer of cells that protects the roots, stems, leaves, and flowers of a plant. (In human anatomy, the word epidermis also refers to skin.) It protects the plant from water loss, controls carbon dioxide and oxygen exchange, and collects water and nutrients from the soil through its roots.

Stomata are holes in the epidermis of a plant’s stems and leaves that allow carbon dioxide, water vapour, and oxygen to pass through.

The plant cuticle, which is mostly cutin, a waxy material that protects epidermal cells from water loss, is itself coated by epidermal cells. To preserve water, plants in deserts and other dry environments develop thick cuticles.

Tissue FAQ

Tissues are made up of groupings of cells, which are the basic biological unit of living organisms.

A self-contained collection of tissues that performs a specific function in the body is referred to as an organ.

A sarcomere is a striated muscular tissue unit that includes the actin and myosin filaments.

Meristem is an area of undifferentiated plant tissue located at the ends of roots and offshoots of stems where new plant development occurs.

Tissue Citations
  • Pericytes, mesenchymal stem cells and their contributions to tissue repair. Pharmacol Ther . 2015 Jul;151:107-20.
  • Tissue regulatory T cells. Immunology . 2020 Sep;161(1):4-17.
  • The colors of adipose tissue. Gac Med Mex . 2020;156(2):142-149.
  • Insulin effects in muscle and adipose tissue. Diabetes Res Clin Pract . 2011 Aug;93 Suppl 1:S52-9.
  • Inter-tissue communication in cancer cachexia. Nat Rev Endocrinol . 2018 Dec;15(1):9-20.
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