Download Adipose Cells

It connects between the different types of
tissues and organs, carrying their blood and
nerve supply.
It is derived mainly from the mesoderm.
It has connective tissue proper and specialized
connective tissue (blood, cartilage and bone).
It is composed of cell and extra-cellular matrix
which consists of ground substance and fibers.
According to the amount and role of these three
components (cells, fibers and ground
substance), there are many types of connective
tissue.
Functions of
Connective Tissue
 Support.
 Medium for exchange.
 Defense and protection.
 Storage of fat.
Connective
tissue
Cells
Matrix
Fibers
Ground
substance
Ground substance
Amorphous gel-like material composed of
glycosaminoglycans, proteoglycans and
glycoproteins.
Glycosaminoglycans are of two types:
– Sulfated such as: keratin sulfate, heparin
sulfate and chondroitin sulfate.
– Non-sulfated such as: hyaluronic acid.
Proteoglycans are responsible for the gel
state of the extra-cellular matrix.
Glycoproteins such as: fibronectin,
chondronectin and osteonectin.
Connective Tissue
Fibers
 Collagen fibers.
 Reticular fibers.
 Elastic fibers.
Collagen Fibers
Tough, firm, inelastic fibers which resists
the tensile forces upon the tissues.
Most common fibers in connective tissue.
Formed of branching bundles of strong
flexible collagen fibers.
It is formed of tropocollagen units running
parallel and overlapping each other.
This tropocollagen unit is formed of 3
polypeptide chains rich in proline, glycine,
hydroxyproline and hydroxylysine.
Vitamin C is important in collagen synthesis.
Collagen Fibers
Are synthesized mainly by fibroblasts.
Chondroblasts, osteoblasts and smooth
muscle fibers also synthesize collagen.
There are many types of collagen fibers
(depending on their amino acid sequence):
– Type I: in connective tissue, bone, dentine.
– Type II: in hyaline and elastic fibers.
– Type III (reticular fibers): lymphatic system,
spleen, skin and vessels.
– Type IV: in basal lamina.
– Type V: with type I and placenta.
– Type VI: in basal lamina.
Reticular Fibers
Thin collagen fibers arranged in
framework instead of bundles.
Synthesized by the fibroblasts.
They form the reticular network
of some organs such as lymph
nodes and bone marrow.
They present also in basement
membrane.
Elastic Fibers
Slender, long and branching fibers in loose
connective tissue, but coarse bundles in
elastic ligaments.
Formed by the fibroblasts and smooth
muscle cells.
Composed of protein elsatin and can be
stretched to one and half times its original
length.
It is present in large arteries, larynx and
trachea, ligamentum flavum and framework
of the spleen.
Connective
Tissue
Cells
Fixed
(permanent)
Transient
(free)
Fixed Cells
1. Fibroblasts.
2. Adipose cells.
3. Pericytes.
4. Mast cells.
5. Fixed macrophages
(histiocytes).
Transient Cells
1. Plasma cells.
2. Lymphocytes.
3. Neutrophils.
4. Eosinophils.
5. Basophils.
6. Monocytes.
7. Transient macrophages.
Fibroblasts
 They are derived from the




undifferentiated mesenchymal cells.
They synthesize the extra-cellular matrix.
They occur either in active state or
inactive state (fibrocytes).
Present nearby the collagen fibers.
Elongated fusiform cells with pale
staining cytoplasm and large granular,
ovoid nucleus.
Adipose Cells
 They are derived from
undifferentiated mesenchymal cell.
 They synthesize, store and release
fat.
 They are two types of adipose cells:
 Unilocular fat cells: from white
adipose tissue.
 Multilocular fat cell: from brown
adipose tissue.
Pericytes
 They surround the endothelial cell of
capillaries.
 They are derived from
undifferentiated mesenchymal cell.
 After injury they may differentiate to
form endothelial cell and smooth
muscle cells.
Mast cells
 They are derived from precursors in
bone marrow.
 Found near blood vessels and body
surfaces (dermis of skin and
digestive and respiratory tract).
 They are large ovoid cell with central
spherical nucleus.
 Their cytoplasm have large
metachromatic granules containing
heparin, histamine and many other
mediators.
Macrophages
 They may be fixed or transient.
 They are active phagocytes removing
cell debris and protecting the body
against foreign invaders.
 They are derived from monocytes
(transient) or from UDMC (histiocytes).
 Highly motile, irregular in shape with
pseudopodia.
 Have dark nucleus and basophilic
cytoplasm containing numerous
lysosomes, vacuoles and residual
bodies.
Plasma Cells
 They are derived from B-lymphocytes.
 Large ovoid cells with eccentrically
placed nucleus.
 Its cytoplasm is intensely basophilic
(RER).
 Its nucleus has the characteristic “clockface” or “radial spoke” appearance.
 They present in areas of chronic
inflammation and foreign bodies, where
they manufacture and secrete
antibodies.
Classification of C.T.
1. Embryonic C.T.:
1. Mesenchymal
2. Mucous
(mucoid)
2. Specialized C.T.:
1. Cartilage.
2. Bone.
3. Blood.
3. Mature C.T. proper:
1. Loose areolar
2. Dense
1. Dense regular
2. Dense irregular
1.Collagenous
2.Elastic
3. Reticular
4. Adipose
Mucous C.T.
 Present in the umbilical cord and
subdermal C.T. of the embryo.
 Loose amorphous C.T. with a jelly-like
matrix containing hyaluronic acid and
little amounts of collagen types I and III
and fibroblasts.
 This type of C.T. is called Wharton’s
jelly.
Loose areolar C.T.
 Contains abundant ground substance
and tissue fluid, nearly all type of C.T.
cells and less amounts of fibers.
 Located in subcutaneous tissue, lamina
propria of gastrointestinal & respiratory
tracts, around blood vessels & organs
and under serous membranes.
 In inflammatory condition it swells
because of increased extra-cellular fluid
(Edema).
Dense regular C.T.
 Contains abundant amounts of fibers with
less cells and ground substances.
 Has tightly packed coarse collagen bundles
arranged in parallel fashion to form cordlike cylinders (tendons & ligaments) or
sheets (aponeurosis).
 Fibroblasts are arranged between the
collagen fibers so they appears elongated
with their dash-like elongated nuclei.
 It is also called white fibrous C.T.
Dense irregular C.T.
 Contains abundant amounts of fibers with
less cells and ground substances.
 Has tightly packed coarse collagen bundles
arranged randomly in all directions, with
few elastic fibers.
 Fibroblasts and other less cells are
arranged between the collagen fibers.
 They are found in dermis of skin, capsule
of organs, sheaths around nerves and dura
mater.
Elastic C.T.
 Composed mainly of elastic fibers with
little amounts of collagen fibers and
few cells and ground substance.
 The elastic fibers are arranged in
sheaths or fenestrated lamellae.
 They are present in the wall of large
arteries, ligamentum flavum, trachea
and larynx, and suspensory ligament
of penis.
Reticular C.T.
 Composed mainly of type III collagen
fibers in a form of network or mesh,
fibroblasts and macrophages.
 It forms the architectural framework
of liver sinusoids, bone marrow,
lymph nodes, spleen, smooth
muscles, islet of Langerhans and
adipose tissues.
Adipose C.T.
 Loose C.T. very rich in adipocytes.
 Two types of adipose C.T.
 Unilocular (white fat) C.T.: its fat cells
are of unilocular type, present in
subcutaneous tissue, around organs
and blood vessels.
 Multilocular (brown fat) C.T., present in
infants and hibernating animals, cells
are rich in mitochondria, supply heat.
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