Introduction
• Connective tissue forms a framework upon
which epithelial tissue rests and within
which nerve tissue and muscle tissue are
embedded.
• Blood vessels and nerves travel through
connective tissue.
Introduction
Main functions of C.T.;
• provide a matrix that connects and binds other
tissues and cells in organs.
• Gives metabolic support to cells as the medium
for diffusion of nutrients and waste products.
Introduction
Structurally, connective tissue is formed by three
classes of components:
• Cells
• Extracellular matrix (ECM), which consist of
ground substance.
• Fibers (collagen, reticular and elastic fibers).
• Unlike the other tissue types (epithelium, muscle,
and nerve), which consist mainly of cells.
A. Ground substance:
The ground substance is transparent material with the
property of a semifluid gel and high water content
stabilized by glycosaminoglycans, proteoglycans, and
glycoproteins. It surrounds the cells and fibers.
• In bone the ground substance includes minerals.
• In blood, the ground substance is fluid (plasma).
B. Fibers:
There are three types of connective tissue fibers:
l. Co/fagen fibers.
Are most abundant and found in almost all types of
connective tissue. They exhibit great strength and are
found in areas where strong support is needed.
Fibroblast
'
”
Elastic fiber
Areolar (loose) connective tissue.
B. Fibers:
2. Elastic there:
Are thin and small, exhibit branching, and have less
strength than the collagen fibers. They exhibit elasticity,
and when stretched, return to their original size without
deformation. They are found in the walls of large arteries,
and elastic cartilage.
Elastic fibers
A: Transverse section of ligament. B: Longitudinal section of ligament.
B. Fibers:
3. Reticufar fibers:
Are thin and form a delicate net-like framework in the
' liver, lymph nodes, spleen, hemopoietic organs, and
other organs. These fibers are normally not visible in
organs unless they are stained with silver.
Reticular connective tissue.
C. Connective tissue cells:
Connective tissue consists of individual cells scattered
within an extracellular matrix. Unlike cells of
epithelial tissue, connective tissue cells are not
directly attached to one another, and cells are
normally separated from one another by varying
amounts of extracellular matrix.
• The most common connective tissue cells are:
(Fibroblasts, macrophages, mesenchymal cell, mast
cells, plasma cells, adipose cells, pigment cells and
reticular cells).
f- Fibroblast:
Fibroblasts are the most common cells in C.T.; the active
fibroblast has an abundant and irregularly branched
cytoplasm. Its nucleus is ovoid, large, and pale-staining,
with fine chromatin and a prominent nucleolus. They
are responsible for the synthesis of extracellular matrix
components, and play's a critical role in wound healing.
F IBROBLAST
2- Macrophages:
In the electron microscope, macrophages are characterized by
an irregular surface. The nucleus is small but stained darker
than the nucleus of the fibroblast and eccentric.
Because of their capacity for locomotion and phagocytosis,
the main function of macrophages is in the defense of the
organism. They engulf; cellular remains, altered
intercellular substance, microorganisms and inert
particles that inter the body.
Macrophages cells
3- ñ4ast cells:
A mast cell is a resident cell of connective tissue that contains
many granules rich ân histamine and heparin. They are seen
either single or grouped along small blood vessels. The cells
are usually ovoid, with small centrally placed nucleus and
cytoplasm filled with fine, closely packed granules.
4- Plasma cells:
Plasma cells also called plasma B cells, are white blood cells
that originate in the lymphoid organs as B lymphocytes and
secrete large quantities of proteins called antibodies in response
to presence of antigens.
They are large, ovoid with relatively large, spherical and
eccentric nucleus. The nucleus characterized by radially
arranged chromatin near the nuclear membrane in a manner very
similar to the cartwheel or o'clock face appearance. There are
few plasma cells in most connective tissues.
S-Adipose ce/is:
