Connective Tissue: Do you know your bone and cartilage is made up of what kind of tissue? They are made up of a specialised tissue called connective tissue. In a multicellular animal, there are four different kinds of tissues based on their structure and functions, i.e., epithelial tissue, connective tissue, muscular tissue and nervous tissue. Connective tissues are most abundant and widely distributed in the body of complex animals that surround many organs.

Connective Tissue Definition

Connective Tissue is defined as a group of tissues that help in binding and supporting other tissues or organs of the body.

Connective Tissues Components or Cells

The connective tissues are made up of the following three components:

1. Matrix

a) It is a clear and viscous substance whose consistency varies from liquid (e.g., blood) to semisolid (e.g., cartilage) and solid (e.g., bone) form.

2. Cells Embedded in the Matrix

a) The cells of connective tissues are of different types which are responsible for secreting the matrix and other substances.
b) It includes fibroblasts, adipose cells, plasma cells, mast cells, mesenchymal cells, macrophages, chromatophores and reticular cells.

3. Fibres

a) In all connective tissues except blood, the cells secrete fibres made up of structural proteins called collagen or elastin.
b) They provide strength, elasticity and flexibility to the tissues.
C) These are non-living products of the cells, which are of three types, i.e., collagen (white fibres), elastic fibres (yellow fibres) and reticular fibres.

Fig: Components of Connective Tissues

Connective Tissues Types

The connective tissues are mainly of the following three types:
1. Loose Connective Tissues
2. Dense Connective Tissues
3. Specialised Connective Tissues

1. Loose Connective Tissues

This tissue has cells and fibres loosely arranged in a semifluid ground substance.
These tissues are of the following two types:

a) Areolar Tissue

i. It is found under the epithelial tissue of the skin, visceral organs like the stomach, trachea and the walls of the blood vessels, etc.
ii. It is made up of glycoproteins that contain two kinds of fibres.
iii. The different cells include fibrocytes, macrophages and mast cells.
Function: It provides tensile strength and protects various organs from mechanical injuries. It also provides rapid diffusion of the materials and migration of wandering cells towards the infected and injured areas.

b) Adipose Tissue

i. It is a modified areolar tissue whose matrix contains a large number of adipose cells with fibrocytes and macrophages.
ii. The cells of this tissue are specialised to store fats.
iii. This tissue is found in the subcutaneous region, around the heart, kidneys, eyeballs, etc.
Functions: It mainly stores fat in the form of oil droplets. It forms a shock-absorbing cushion around the eyeballs and kidneys also. It also helps in the production of blood corpuscles

2. Dense Connective Tissues

Fibres and fibroblasts are found compactly packed in the dense connective tissues.
This tissue is of the following two types:

a) Dense Regular Connective Tissue

i. In this tissue, the collagen fibres are present in rows between many parallel bundles of fibres.
ii. It is of further two types, i.e., white fibrous connective tissue (includes tendons and sheets) and yellow elastic connective tissue (includes ligaments and sheets).
Functions: The tendons join the skeletal muscles with the bones, and the ligaments join bones to bones. The fibres allow the stretching of various organs, especially the joints present in between the bones.

 b) Dense Irregular Connective Tissue

i. In this tissue, the fibroblasts and collagen fibres are oriented in different patterns.
ii. This tissue is present in the skin.
Functions: The fibres provide strength to the skin by making it resistant to wear and tear.

Fig: (a) Dense Regular Connective Tissue, (b) Dense Irregular Connective Tissue

3. Specialised Connective Tissues

This tissue is of the following types:

a) Skeletal Tissues

i) These tissues form the endoskeleton of the vertebrates that form a rigid framework that supports the body.
ii) It also protects the vital organs and helps in locomotion.
iii) There are two types of skeletal tissues:
Cartilage: It is a tough, semi-transparent, elastic and flexible tissue formed up of cartilage cells called chondrocytes. It is present in the tip of the nose, outer ear joint, between adjacent bones of the vertebral column, limbs and hand in adults.
Bone: It is a hard and rigid connective tissue rich in calcium salts and collagen fibres. It is made up of bone cells called osteocytes. It interacts with the skeletal muscles to bring about movements.

b) Vascular Tissues

i) These are motile connective tissues consisting of the fluid matrix (without fibres) and cells.
ii) It helps in the transport of materials from one place to another.
iii) It is of the following two kinds:
Blood: It is a mobile, watery fluid with a slightly salty taste composed of plasma (fluid) and blood corpuscles (RBC, WBC and platelets). It is bright red in colour when oxygenated and purple when deoxygenated. It circulates within the blood vessels of higher animals. It helps in the transport of substances, provides immunity to the body, maintains the pH and conducts heat to skin for dissipation, etc.
Lymph: It is a mobile connective tissue consisting of lymph plasma (fluid) and lymph corpuscles (cells). It is pale yellow in colour, and its plasma is without the plasma proteins. It is present in the vessels called lymph vessels. It provides immunity to the body, helps in the absorption of fats, maintains the blood volume and keeps the tissue cells moist, etc.

Fig: Specialised Connective Tissues: (a) Cartilage, (b) Bone, (C) Blood

c) Reticular Connective Tissues

i) This tissue consists of star-shaped reticular cells whose protoplasmic process joins to form a cellular network.
ii)The reticular cells consist of reticular fibres made up of reticulin protein.
iii)This tissue is found in the liver, spleen, lymph nodes, thymus, tonsils, bone marrow and lamina propria of the gut wall.
Function: This tissue provides strength and support to many organs. It also helps to bind together the cells of smooth muscles. The reticular cells are phagocytic and form the defence mechanism of the body.

d) Pigmented Connective Tissues

i) The irregular pigmented cells (chromatophores or melanophores) contain yellowish-brown, black or blue melanin pigment granules.
ii) This tissue is present in the choroid, ciliary body and iris of the eye and dermis of the human skin.
Function: It provides colour to the structures.

e) Mucoid Connective Tissues

i) This tissue contains a jelly-like substance called Wharton’s jelly and some delicate collagen fibres and primitive type of fibroblasts.
ii) This tissue occurs as embryonic connective tissue in the foetus and vitreous chamber of the eye.
Function: It is involved in the secretion of ground substance and fibres.

Fig: Types of Connective Tissues

Connective Tissue Functions

The connective tissue performs the following functions:
1. It mainly joins one tissue to another in the organs.
2. The adipose tissue stores fat.
3. The cartilage and bones form a supporting framework for the body.
4. Blood and lymph carry materials from one part of the body to another.
5. The cells of connective tissue protect and cleanse the body.
6. The adipose tissue acts as a shock absorber around some organs, such as eyeballs and kidneys.
7. The adipose tissue acts as packing material in various organs,
8. Bone marrow forms a source of blood corpuscles.
9. The collagen fibres help in the repair of injured tissues.

Do you Know?

The term connective tissue was introduced by J.P. Muller in \(1830.\)

Summary

Thus, connective tissue forms one of the four basic types of animal tissues found in the animal body. It is found everywhere in between other tissues in the body, including the nervous system. So, it helps in connecting the tissues and organs. Since it helps in linking and supporting other tissues and organs of the body, it is named connective tissue.

Frequently Asked Questions (FAQs) on Connective Tissue

Q.1. What are the three types of connective tissues?
Ans: The three types of connective tissues are as follows:
a. Loose Connective Tissues
b. Dense Connective Tissues
c. Specialised Connective Tissues

Q.2. What is connective tissue and its function?
Ans: Connective Tissue is defined as a group of tissues that help in binding and supporting other tissues or organs of the body.
Function: It helps in linking and supporting other tissues and organs of the body.

Q.3. What are the common connective tissue disorders?
Ans: The common connective tissue disorders include Rheumatoid Arthritis, Scleroderma, Lupus, Dermatomyositis, etc.

Q.4. What is the Fibromyalgia condition in connective tissue?
Ans: Fibromyalgia condition is characterised by fatigue, sleep, memory and mood issues. The symptoms of this disorder include widespread muscle pain and tenderness.

Q.5. What does connective tissue disorder do to your body?
Ans: Connective tissue disorder can cause harm to the various types of proteins and the surrounding areas in our body like collagen found in the tendons, ligaments, skin, cartilage and blood vessels.

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