- 2 general types: CT Proper and CT Supportive.
- CT Proper classified on the basis of intercellular material (types, arrangement and
density of fibers). Intercellular material contains a variety of fibers embedded in a
semi-fluid ground substance (amorphous intercellular substance). Fibers + ground substance = Matrix.

1) Fibers (protein composition)

2. Ground Substance (Intercellular Material)

1) Undifferentiated Mesenchymal Cells = embryonic, some persist in adult as
precursors to other CT cells; stellate with elongated nuclei and coarse chromatin
2) Fibroblasts = responsible for production of fibers and ground substance

3) Fat Cells = found in areolar (loose) and adipose CT - not capable of mitotic
division as adult cell 2 Types:
a) White Fat = most common, serves as storage tissue for lipid (energy reserve)

b) Brown Fat = occurs only in mammals; relatively scarce, found in anterior regions of
body (e.g., between scapulas) in neonates, hibernators and cold-adapted mammals.
4) Macrophages = phagocytic cells forming from monocyte (=histiocyte)
5) Mast Cells = large, rather round cells with basophilic granules in cytoplasm
and central pale nucleus; similar to basophil, but may arise from several sources
not just bone marrow

6) Chromophores = (e.g., Melanoblast/cyte --- brown/black)

7) Plasma Cells = rare in most CT, more common in lymph nodules and
reticular CT of blood-forming organs

8) WBCs - most common types in CT are lymphocytes and eosinophils

1) Mesenchyme = embryonic, mesenchymal stellate cells in semi-fluid matrix;
enables cells to move about easily
2) Mucous = transient tissue appearing in normal development of CT and as
Wharton's Jelly of umbilical cord

3) Areolar (Loose Irregular) = very common, serves connective and supportive
4) Adipose - 2 Types:
a) White Fat = aggregations of unilocular fat cells, each cell surrounded by a web of
reticular fibers

b) Brown Fat (BAT) = aggregations of smaller multilocular fat cells

5) Reticular = composed of reticular fibers and reticular stellate cells
(appearance like mesenchyme with reticular fibers)

6) Dense Irregular = like a densely packed areolar CT with little ground substance

7) Dense Regular = fibers are densely packed and lie parallel to each other,
provides great tensile strength; found in tendons, ligaments, aponeuroses (flat sheets
connecting muscle to bone), some organ capsules

1. Collagen fibers = primary tendon bundles (covered by areolar CT = endotendineum)
2. Primary bundle grouped into fascicles (covered by dense CT = peritendineum)
3. Fascicle grouped into tendon (covered by dense CT = epitendineum)
4. Fibrocytes (inactive) occur in longitudinal rows between collagen fibers, in c.s.
fibrocytes appear stellate ("winged fibroblasts")

8) Elastic = coarse parallel elastic fibers bound together by a small amount of delicate
CT with fibroblasts, collagen fibers

9) Lamellated = condensation of dense irregular CT around blood vessels, nerves and
gland ducts

To Lecture 8