A fibroblast is a type of cell which is responsible for making connective tissue. Fibroblasts play a critical role in making up the large majority of the bulk of an organism, and they can be found in huge numbers all over the body. These cells can differentiate into cells responsible for producing several different kinds of connective tissue, including chondroblasts, which are responsible for making collagen, and osteoblasts, which make bone.
Fibroblasts have two different stages. When the cell is actively dividing and making connective tissue, it is known as a fibroblast. When it goes dormant, it becomes a fibrocyte. Fibrocytes change shape, becoming more cylindrical over time, which makes them easy to identify, and they can be seen along the margins of many types of connective tissue.
These cells arise from mesenchymal stem cells, stem cells which are capable of differentiating into several different kinds of cells as they are needed. These cells are present from birth in the body, and they can be seen at varying levels of activity depending on age, physical condition, and other factors. The body is constantly developing more fibroblasts in response to emerging conditions and various issues, ranging from growth spurts to broken bones.
Fibroblasts help to maintain the structural integrity of the body, by constantly reinforcing the connective tissues so that their density and condition is maintained. As cells die and are absorbed, fibroblasts make more to address the change. Fibroblasts are also involved in the production of the ground substance, a non-cellular component of the extracellular matrix which includes a variety of proteins and other compounds.
A fibroblast can also play a role in tissue repair. When someone is cut, for example, fibroblasts are part of the body's response team, acting to repair the wound while other cells prevent infection. One could think of fibroblasts as a construction crew which is designed to be highly skilled and very flexible so that it can respond quickly to emerging problems. The body can also produce more fibroblasts as needed.
When someone develops a disorder which inhibits the production or function of fibroblasts, it can become quite problematic. The connective tissue is critically important, and it can become degraded or lost over time, leading to muscle weakness and a variety of other symptoms. Doctors can sometimes identify such disorders by looking at a fibroblast under the microscope, or culturing a fibroblast sample from a patient to look for abnormalities.