Cells in connective tissue

Types of cells found in connective tissue.

Fibroblasts. These are the least specialised of all the cells. They are mainly responsible for secreting the non-rigid extracellular matrix including the fibres: collagen, elastin or fibronectin.

Adipocytes. These are fat storing cells, which are thought to derive from fibroblastic like cells.

Macrophages, Mast cells and Plasma cells. These are all types of Immune cell.

The type of connective tissue shown in this photograph is is a type of loose connective tissue. Click here to find out more about the three different types of connective tissue.

It contains collagen fibres, fibroblasts and adipocytes (these cells are 'empty looking' as the process of making the stained section extracts the lipid from these cells).

It also contains plasma cells lymphocytes, macrophages and mast cells. The mast cells stain quite darkly, and look granular, as they have lots of secretory granules.

See if you can identify some of the cells, with the labels off.

Cells that are found in specialised forms of connective tissue:

Specialised connective tissue includes tendons and ligaments, Bone and Cartilage, haemopoetic tissue, blood and adipose tissue. Bone contains Osteocytes, and osteoblasts (osteo - bone) which secrete the type of extracellular matrix material (ECM) that makes up bone. Cartilage contains chondrocytes and chondroblasts (chondro - cartilage) which secrete the type of ECM found in cartilage, respectively. Blood vessels contain Endothelial cells, the simple squamous endothelium that lines the circulatory system, which are covered in the section on epithelia. Also present, just underneath the epithelium of blood capillaries, are cells called Pericytes - (perivascular cells - peri is greek for 'around), which can divide and provide a source of new fibroblasts, especially following tissue injury.

Finally, smooth muscle is commonly found in connective tissue. For example, in regions of connective tissue where there are glands, smooth muscle cells called myo-epithelial cells, which lie between epithelial cells and the basement membrane of ducts, are found.