Tissues

The UPSC mains GS-3 paper syllabus has various subjects like Economics, Science and Technology. Science and technology in UPSC is mostly concerned with current Affairs. but it is necessary to understand the basics of science. After the studies of Cells, the next important topic in Biology is Tissues, This article will give the details of Various types of Tissues

TOPICS

• What are tissues?
• Epithelial tissue
• Connective tissue
• Muscular tissue
• Nervous tissue.

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WHAT ARE TISSUES?

Tissues are groups of cells that have a similar structure and act together to perform a specific function. The word tissue comes from a form of an old French verb meaning “to weave”. There are four different types of tissues in animals: connective, muscle, nervous, and epithelial. In plants, tissues are divided into three types: vascular, ground, and epidermal. Groups of tissues make up organs in the body such as the brain and heart.

TYPES OF TISSUES

EPITHETICAL TISSUE:

It is a tissue that is made up of tightly packed cells. Without much materials with in these cells. The reasons for the tightly packed cells are to act as a barrier against mechanical injury, invading micro- rganisms and fluid loss. We can define epithetical tissue by considering two points in mind one is the number of cells layers and two the shape of the cells.

 On the basis of cell layers

•  When an epitheliumhas a single layer of cells it is called a simple epithelium.
• Where as a multiple tier of cells are known as stratified epithelium.

On the basis of simple shape of cells:

• Cuboidal : its occurrence is in kidney tubules, salivery glands, inner lining of the cheek. Its main function is to give mechanical strength.
• Columnar : its occurrence is in sweat gland, tear gland, salivary gland its main function is to gives mechanical strength concerned with secretions.
• Squamous : when it forms a living as that of blood vessels, it is called endothelium. Its main function is to protect the underlying parts from injury, entry of germs, etc.

CONNECTIVE TISSUE:

Connective tissue : its main function is to bind and support other tissues. They have sparse populations of cells scattered through an extra cellular matrix. This extra cellular matrix is a web of fibers that is  woven in a homogeneous ground substance they can be liquid, solid, or jelly like. There are a few types of connective tissue.

1. Areolar tissue : It fills spaces inside organs found around muscles, blood vessels and nerves. Its main function is to joins skin to muscles, support internal organs, help in the repair of tissues.Where as tendon’s main function is to connect muscles to bones and ligament is connects bones to each other.
2. Adipose tissue : its occurrence is below skin, between internal organs and in the yellow bone Marrow. Its main function is to storage of fat and to conserve heat.
3. Skeletal tissue : Bone & Courtilage cartilage occurrences is in nose pic, epigotis and in intervertebral disc of mammals. Its main function is to provide support and flexibility to body part. Where as bone protects internal delicate organs provides attachments for muscles, bone marrow makes blood cells.
4. Fluid tissue : Blood & Lymph blood transport O2 nutrients, hormones to tissues and organs. Where as leucocytes fight diseases and platelets help in cloting of blood. Lymph transport nutrients into the heart and it also forms the defense system of the body.

MUSCULAR TISSUE:

It is specialized for an ability to contract muscle cells. These are elongated and referred to as muscle fibers. When a stimulates is received at one end of a muscle cell, a wave of excitation is conducted through the entire cell so that all parts contract in harmony. There were three types of muscle cells: skeletal, cardiac, and smooth muscles.

1. Skeletal muscle : It attached primarily to bones. Its main function is to provide the force for locomotion and all other voluntary movements of the body.
2. Cardiac muscle : It occurs only in the heart. The contraction and relaxation of the heart muscles help to pump the blood and distribute it to the various parts of the body.
3. Smooth muscles : It can be found in stomach, intestines, and blood vessels these muscles cause slow and prolonged contractions which are involuntary.

 

NERVOUS TISSUE:

Nervous tissue : This tissue is specialized with a capability to conduct electrical impulses and convey information from one area of the body to another. Most of the nervous tissue (98%) is located in the central nervous system. The brain and spinal cord. There are two types of nervous tissue neurons and neuroglia.

• Neurons
• Neuroglia

Neurons: it actually transmit the impulses, receptor nerve ending of neurons react to various kind of stimuli and can transmit waves of excitation from the farthest point in the body to the central nervous system. You will read all the details in Chapter Four.

Important facts regarding tissues

• Muscles contain special protein called contractile protein. Which contract and relax to cause movement.
• Fat storing adipose tissue is found below the skin and between internal organs.
• Two bones are connected to each other by a tissue called ligament. This tissue is very elastic.
• The skin, the living of the mouth, the living blood vessels, kidney tubules are allmade up of epithelial tissue.
• Voluntary muscles and cardiac muscles are richly supplied with water where as involuntarymuscles are poorly supplied with blood.
• Muscles tissue is composed of differtiated cells containing contractile protein.

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