Histology Guide virtual histology laboratory

Chapter 3 - Connective Tissue

Connective tissue supports and protects organ. It has three primary components: fibers, extracellular matrix and cells. The proportion of these elements is the basis of which the connective tissues are classified.

This chapter examines the basic types of connective tissue, while subsequent chapters examine specialized connective tissues such as cartilage, bone and blood.

Connective tissue fibers provide general support for other tissues. Three types of fibers occur in connective tissue: collagen, elastic and reticular.

Collagen is the most abundant structural protein in connective tissues.

EM 296 Collagen Fibers

EM 297 Elastic Fibers

EM 283 Dense Irregular Connective Tissue


Although connective tissue has fewer cells than most tissues, the cells found in connective tissue are extremely important. Fibroblasts and adipocytes do not leave connective tissue.


Fibroblasts are widely distributed within connective tissue and synthesize the components of the extracellular matrix. They are also capable of differentiating into other types of connective tissue cells

EM 006 Fibroblast

EM 109 Fibroblast


Adipocytes (or fat cells) are specialized for the synthesis and storage of lipids. They may occur singly but are more often found in clusters within loose connective tissue.

EM 107 Adipose Tissue


Neutrophils, eosinophils, basophils, lymphocytes, and monocytes are immune cells that migrate from blood into connective tissue.


Eosinophils are involved in many inflammatory processes, including parasitic infections, alleregic diseases, and asthma.

EM 161 Eosinophil

Mast Cell

Mast cells are widely distributed in connective tissue. The release molecules that dilate blood vessels allowing the recruitment of more immune cells to an infection.

EM 014 Mast Cell

EM 108 Mast Cells

EM 110 Mast Cell

Mast cells undergo rapid degranulation during an anaphylactic reaction.

EM 118 Mast Cell


Lymophocytes develop the ability to recognize and respond to antigens. Their number increases dramatically at sites of inflammation.

EM 199 Lymphocyte

Plasma Cell

Plasma cells produce large quantities antibodies against specific antigens. They are widely distributed in connective tissue, especially in the gastrointestinal tract

EM 105 Plasma Cell

EM 114 Plasma Cell


Macrophages are avidly phagocytic cells that engulf and digest microbes, cellular debris and foreign substances.

EM 103 Macrophage

EM 016 Macrophage

EM 111 Macrophage

Mast Cell / Plasma Cells / Eosinophils

Example of multiple types of immune cells in connective tissue.

EM 132 Smooth Muscle Cell