CONNECTIVE TISSUE





Connective tissue is found in some form in every part of the human body. It plays a major role in supporting all tissues.





Connective tissue is the only tissue in the human body that is not primarily made up of cells.

Connective tissue is comprised of a non-living substance, called the ground substance made up of

organic and inorganic substances in which cells and protein fibers are embedded.


The makeup of the ground substance greatly contributes to the physical properties of a connective tissue.

Connective tissue contains a variety of cells.


A primary cell of most connective tissue includes the fibroblast. Fibroblasts produce collagen, elastic, and reticular fibers.


Collagen is a very strong protein fiber. Typically when the term “fibrous” is used to describe a collagen-rich tissue. Reticular fibers are modified collagen fibers.

Elastic fibers are made of a protein called elastin. These fibers have elasticity, meaning they can be stretched and then return to it’s resting length when the stretch is relieved.






Common Functions of Connective Tissue


Support and connect other tissue

(tendons, ligaments)


Protection

(fibrous capsules, bone, immune tissue)


Transport

(blood)


Energy storage

(adipose tissue)


Cushioning (adipose tissue)


Thermal insulation

(adipose tissue)







Membranes — Simple Organs





Remember, the definition of an organ is two or more usually four) tissues grouped together to perform a common function. Membranes are simple organs because they comprise two tissues—epithelial and connective.





Types of Membranes


Cutaneous Membrane

The skin is a cutaneous membrane. It is composed of the epidermis (epithelial tissue) and the dermis (connective tissue). It is a dry membrane.

Mucous Membrane

Mucous membranes line cavities that are open to the external environment (ocular, nasal, digestive, respiratory). Mucous membranes are moist membranes


Serous Membrane

Serous membranes line cavities that are closed to the external environment (ventral, dorsal). They line the wall of the cavity and then fold on itself and covers the external surfaces of the organs in the cavity.

Tissue Repair


Damaged tissue is repaired via fibrosis or regeneration.


Epithelial tissue heals via a regenerative process, meaning that damaged tissue is replaced with the same tissue.

Connective tissue heals via a fibrotic process, meaning that damaged tissue is replaced by a proliferation of collagen fibers, forming scar tissue.

The overwhelming majority of tissue repair in the body is via the fibrotic process.