Connective Tissue

Tissue refers to a group of cells with intracellular components to perform a particular function.

Tissues are mainly of four types-

  1. Epithelial tissue

  2. Muscular tissue

  3. Neural tissue

  4. Connective tissue 

Along with epithelial tissue, muscle tissue, and nervous tissue, connective tissue is one of the four essential forms of animal tissue. Here, you will study connective tissue definition, characteristics of connective tissue, and classification of connective tissue in detail.


What is Connective Tissue?

Connective tissues help and connect the body's various tissues and organs. Connective tissue develops from the inner lining of the embryo known as mesoderm.


Characteristics of Connective Tissue

Connective tissue consists of a few cells, known as collagen or elastin, present in the intercellular network of protein fibers secreted by the cells. A thin gel of polysaccharides, which together with fibers form a matrix or ground material, is also secreted by the cells. Connective tissues are flexible with high tensile strength. This property of connective tissue is due to the presence of fibers.

These fibers are of three types-

  • Collagen Fibers: 

Collagen fibers are the most common and are made up of collagen, a fibrous protein. Collagen fibers have high tensile strength  (comparative to steel).

  • Elastic Fibers: 

A network is shaped by elastic fibers and can be stretched like a rubber band. They are made up of elastin-protein. If the force is removed, they maintain their original shape and scale.

  • Reticulate Fibers: 

They are composed of glycoproteins and collagen. They are small and form a network that is fragile. They bind connective tissues to adjacent tissues.


Connective Tissue Cells Function

In various types of connective tissues, there are different kinds of cells present. They secrete various kinds of fibers and matrices. Fibroblasts or adipose cells are stationary and migrating cells are macrophages, mast cells, monocytes, and lymphocytes.

  • Fibroblasts: 

In developing tissues, fibroblasts are located and play a significant role in wound-healing. They are spindle-shaped between collagen fibers and are present. Tropocollagen and other compounds present in the matrix are secreted by them. 

  • Macrophages:

There are also macrophages known as scavenger cells. They wander around connective tissues, clean up debris, and phagocytose bacteria, and other antigens.


Different Types of Connective Tissue

There are three different types of connective tissue-


Loose Connective Tissue:

All over the body, loose connective tissues are present, where both support and elasticity are required. Blood vessels, muscles, and nerves all have a loose wrap of connective tissue. Along with adipose tissues, they form the subcutaneous layer underneath the skin, connecting muscles and other structures to the skin. In the semi-fluid matrix, the fibers and cells are loosely organized. As a filling, they are found among several organs and serve as a shock absorber and reservoir for salt and fluid.

  • Areolar tissue: It is located under the skin, protecting the epithelium. It includes fibers, fibroblasts, mast cells, and macrophages that are uniformly distributed. It protects the abdominal cavity's organs, fills the space between muscle fibers, and wraps around blood and lymph vessels. 

  • Adipose Tissue: They are present and store fat under the skin. It serves as a shock absorber and, in colder conditions, helps maintain body temperature. 

  • Connective reticular tissue: It is created by reticular fibers. The internal structure of organs such as the liver, lymph nodes, and spleen is supported.

Fibroblast cells and fibers are compactly packed within the thick connective tissue. Supporting and transmitting mechanical forces is their key role. They are far less flexible than connective tissue that is loose. They are classified into two groups on the basis of the arrangement of collagen fibers: 


Dense Normal Tissue:

  • Dense regular tissue:  The orientation of fibers in this type of tissue is regular. Between the parallel running bundles of fibers, the collagen fibers are present. The standard structure increases tensile strength and is resistant to stretching in the direction of fiber orientation. Tendons and ligaments are examples of thick normal tissue.

  • Tendons and Ligaments: Tendons bind bones to the muscles of the skeleton. Two bones are bound together by ligaments. 

  • Dense irregular tissue: There are several fibers that are irregularly or randomly oriented, like collagen. In all directions, the uneven arrangement gives uniform power. A mesh-like network can be created by fibers. In the dermis of the skin, this sort of tissue is present.

Specialised Connective Tissue:

Other than these, connective tissues help maintain proper posture and protect internal organs, such as cartilage and bone.  

Blood and lymph are connective fluid tissues that circulate throughout the body, aiding all organs in contact and communication. 

  • Cartilage: In the embryonic stages, cartilage is mainly present and acts as a supporting skeleton. Most of the cartilage in adults is replaced by bones, but some structures in adults still sustain it. In humans, there is cartilage in the external ear, nose, and hands between the bones of the vertebral column.

  • Blood: Blood is made up of different plasma cells. Red blood cells (RBCs), white blood cells (WBCs), and platelets are present in the blood. 

  1. RBCs have haemoglobin and oxygen for transport. 

  2. The WBCs form a mechanism of defense and protection against foreign antigens. 

  3. For blood clotting, platelets are essential. 

  4. For transport to various parts of the body, plasma includes proteins, water, hormones, salts, etc. 

  • Lymph: The lymph drains into the blood and transports absorbed fat into the blood that is unable to penetrate directly into the bloodstream. In the liquid matrix, the lymph has white blood cells. They help us get rid of waste materials and pollutants. They contain WBCs, which aid in infection-fighting.

Connective Tissue Disorders:

Connective tissue disorders can be caused by gene mutations or by defective genes that are inherited. Epidermolysis bullosa (EB) and Marfan syndrome are two hereditary diseases of connective tissue. 

  1. Marfan's syndrome is caused by faulty genes that manufacture fibrillin-1 protein. A very small and long body characterizes the disorder. The toes and fingers are spider-like. 

  2. Skin oversensitivity characterizes EB.

  3. Rheumatoid arthritis (RA) contributes to joint damage and deformities. RA is due to the synovium, the membrane between joints, being attacked by the immune system. 

  4. Scleroderma-It is characterized by connective tissue thickening and hardening. It may be localized, affecting only a portion of the skin, or systemic, affecting vital organs.

Conclusion

Connective tissue is the basic tissue of the body. It includes fat, cartilage, bone, and blood. It provides support, helps in filling the spaces between organs, protecting organs, and also helps in the transportation of materials around the body. So, go through the notes given here to learn the importance of connective tissue and other related concepts.

FAQs (Frequently Asked Questions)

Question: What are the Different Types of Connective Tissue?

Answer: Types of Connective Tissue-

  1. Areolar Connective Tissue.

  2. Adipose Tissue.

  3. Reticular Connective Tissue.

  4. Dense Regular Connective Tissue.

  5. Dense Irregular Tissue.

  6. Elastic Connective Tissue.

  7. Cartilage.

  8. Elastic Cartilage.

Question: What are the Examples of Connectives?

Answer: Examples of connectives include adipose, cartilage, bone, blood, and lymph.Jan 28, 2020