CONNECTIVE TISSUE
Origin of connective tissue cells
LOOSE CONNECTIVE TISSUE
• Characterized by loosely arranged fibers and an
abundance of cells
• The primary location is :
• beneath those epithelia that cover the body
surfaces and line the internal surfaces of the
body
• In association with the epithelium of glands
• surrounds the small vessels
Loose connective tissue (scheme)
Light micrograph of loose C.T.
Connective tissue cells can be categorized as
fixed and wandering
Fixed cell population
- Fibroblasts
- Myofibroblasts
- Macrophages
- Mast cells
- Adipose cells
- Reticular cells
- Undifferentiated
stem cells
Wandering cell population
- Lymphocytes
- Plasma cells
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
E.M. of fibroblast portion with the
adjusting collagen fibers
E.M. of a macrophage surrounded
with collagen fibers
L.M. of macrophages in liver (von
Kupffer cells)
Specific names of different location
macrophages (macrophage system)
•
•
•
•
•
•
•
•
•
•
Monocytes (blood)
Macrophages-histiocytes (connective tissue)
Dust cells (lung alveoli)
Kupffer cells (liver)
Langerhans cells (skin)
Hofbauer cells (placenta)
Osteoclasts (bone)
Microglia (brain)
Dendritic cells (lymphoid organs)
Microfold (M) cells (intestine)
E.M. of a mast cell
Physiologically active substances
secreted by mast cells
E.M. of adipocytes on different
stages of maturation
Plasma cell schematic
representation
NON-CELLULAR COMPONENTS OF
CONNECTIVE TISSUE
Fibers
• Collagen fibers – forms the most abundant fibers of
connective tissue
• Reticular fibers – provide a supporting framework for
the cellular constituents of lymphoid organs mostly
• Elastic fibers – provide tissues with the ability to
respond to stretch and distension
Ground substance – consists largely of highly hydrated
proteoglycans, of hyaluronic acid, and GAG
(chodroitin-sulphate, heparan-sulphate, dermatansulphate, keratan-sulphate)
CLASSIFICATION OF CONNECTIVE TISSUES
EMBRYONIC CONNECTIVE TISSUE
• Mesenchyme
• Mucous (Wharton’s jelly)
CONNECTIVE TISSUE PROPER
• Loose (Areolar)
• Dense
- Irregular
- Regular
SPECIALIZED CONNECTIVE TISSUE
• Adipose (unilocular & multilocular)
• Reticular
• Cartilage
• Bone
• Blood
DENSE CONNECTIVE TISSUE
• DENSE IRREGULAR CONNECTIVE TISSUE is
characterized by an abundance of fibers and few
cells. It forms the reticular or deep layer of the
dermis
• DENSE REGULAR CONNECTIVE TISSUE is
characterized by ordered and densely packed
arrays of fibers and cells. It is the main functional
component of tendons, ligaments, aponevroses
L.M. of a tendon, cross section