Histology is the study of tissues. Tissues are groups of cells that are similar in structure and function. There are four tissue types associated with animals such as humans. They are:
Each of these tissue categories has distinctive cell shapes and functions.
Connective tissue is the most abundant and variable of the human tissues. It is designed for supporting, protecting, and binding the tissues of the body. Most CT's are well vascularized (except for tendons, ligaments, and cartilage). Connective tissues all consist of three elements: (1) CT cells, (2) matrix produced by the CT cells, and (3) fibers produced by the CT cells. There are many types of cells associated with CT, but the generic "CT precursor" is the fibroblast.
Matrix is produced by the CT cells, then released from the cells. It is noncellular and nonliving. It provides extracellular support for the CT cells that produced it. There are several types of fibers in CT. The three major types are collagen, elastic, and reticular.
NOTE:
(1) Areolar CT is a mixture of cells, various types of fibers and matrix.
(2) Areolar CT is often termed the "packing tissue" of the body because it fills up spaces between organs and provides cushioning. It also provides immediate physical support for the epithelia.
(3) Elastic fibers are labeled in this micrograph, but collagen fibers are not because they are the "pink blur" that fills the entire background of the micrograph. The dark ovals and circles scattered throughout the field of vision are nuclei of CT cells.
