Loose or Areolar Connective Tissue

The animal tissues are basically of four types which are as follows

1.  Epithelial tissue contributes to the free surface of the body.
2. Connective tissue links other tissue and organs together. 
3. Muscular tissue makes muscles of the body.
4. Nervous tissue helps in coordination of the body.

So, the connective tissue works as a binding material in the body. 

Connective Tissue

The mesodermally driven connective tissue is present extensively in the body of higher animals. A web of fibers is observed in a jelly-like medium while observing a connective tissue through a microscope. The matrix consists of fibroblast cells that secrete fibers and macrophages which engulf foreign particles entering inside the body. The connective tissue fibers are of three types:

• Collagenous fibers which provide strength and flexibility to the body.
• Reticular fibers which provide a supporting network in many situations. These fibers do not appear in bundles and have uneven thickness. Reticular fibers are found in the spleen, bone marrow, and in the liver where they provide a supporting network.
• Elastic fibres provide the necessary elasticity to a tissue. These fibres are made from elastin protein which is further formed of smaller units called tropoelastin.

Types of Connective Tissue

 Based on structure, the connective tissue is classified into three categories: 

1. Loose connective tissue,
2. Dense connective tissue and 
3. Specialised connective tissue.

• Loose connective tissue is of two types: adipose connective tissue and areolar connective tissue.
•  Dense regular and dense irregular connective tissue are the two divisions of dense connective tissue.
• Specialised connective tissue consists of blood, bone, and cartilage respectively.

What is Loose or Areolar connective tissue?

Loose connective tissue is classified into two types which are 

• The adipose tissue is located in the skin layers and mainly stores fats.
• The areolar tissue is also found below the skin. It consists of loosely arranged collagen fibres that appear to enclose large substances and abundant ground substances. The spaces are called areolae and for this reason this tissue is called Areolar tissue.

The loose connective tissue mainly consists of collagen fibres, fibroblast cells, macrophages, and mast cells in its structure.

Macrophages: These cells of the loose connective tissue are also regarded as histiocytes. Macrophages eliminate foreign harmful substances which enter the body by the process of phagocytosis. It also plays a major part in immunological mechanisms.

Mast Cell: These are small and round cells and possess granules in their cytoplasm. Mast cells release histamine when an allergic reaction occurs.

Fibroblast: The cells are found in a majority of areolar tissue and are mainly involved in the production of collagen fibres. They also produce reticular and elastic fibres. Fibroblast actively functions to repair wounds.

Collagen fibres: Each collagen fibre collectively appears in bundles of several collagen fibres which can be straight or wavy. These fibres possess a considerable amount of elasticity. Each collagen fibre is made of a protein called collagen. The collagen protein is made up of tropocollagen molecules.

Functions

• Connective tissue serves to hold together, and support, different elements within an organ. 
• The areolar connective tissue binds various layers of hollow viscera.
•  It forms a framework that supports the cellular elements of various organs like the spleen and lymph nodes. 
• The loose nature of areolar tissue facilitates movement between structures connected through it.
•  It also provides elasticity to muscles. 
• It also provides a defence to the body through its macrophages.

Conclusion

The connective tissue is widely distributed in the body. Adipose and areolar are the two main loose connective tissues. The adipose tissue stores fat and the areolar tissue provides the necessary support framework. The areolar tissue consists of many types of cells in its structure which provide a specific function to the areolar tissue. Mast cells and macrophages provide protection to the tissue whereas the fibroblast and collagen fibres help in building up new fibres in the tissue.