Transcript Slide 1

Connective
Tissue
 Connective tissue may be defined as that
group of tissues predominantly composed of
extracellular or intercellular material (matrix),
secreted mainly by its cells, which are,
therefore, usually widely spaced.
 The extracellular matrix consists of fibers and
amorphous ground substance.
 So there are three elements of connective
tissue (cells, fibers and ground substance).
ALLAH Subhanahu develops connective tissue
from embryonic mesoderm and, in the
head region, largely from neural crest cells.
CLASSIFICATION
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Primitive or undifferentiated
connective tissue
Mesenchymal tissue
Intermediate or maturing
connective tissue
Mucoid tissue
Adult or Mature connective
tissue
 Mature Connective Tissue is
mainly of three types
 Soft,
 Hard and
 Fluid-like
 Soft Connective tissue is again of two
types
 Loose connective tissue
 Dense connective tissue
Classification of Loose
connective tissue
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Ordinary
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Areolar (Loose Areolar connective
tissue)
Cellular (Cellular connective tissue)
Vascular (Vascular connective tissue)
Special
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Adipose
Reticular
Lymphoid
Pigmented
Classification of Dense
connective tissue
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Irregular (Dense Irregular
connective tissue)
Regular (Dense Regular
connective tissue)
 White fibrous tissue
 Yellow elastic tissue
Hard (Skeletal connective
tissue)
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Cartilage
Bone
Hyaline
Non-Articular
Articular
Elastic
Fibrous
Compact
Spongy or Cancellous
 Fluid like
(Haemopoietic connective
tissue)
Bone marrow or Myeloid
tissue
Blood
 CLASSIFICATION OF CONNECTIVE TISSUE
 Primitive or undifferentiated connective tissue
Mesenchymal tissue
 Intermediate or maturing connective tissue
Mucoid tissue
 Adult or Mature connective tissue
 Mature Connective Tissue is mainly of three types
Soft, Hard and Fluid-like
 Soft Connective tissue is again of two types
 Loose connective tissue
 Dense connective tissue
 Classification of Loose connective tissue
 Ordinary
Areolar (Loose Areolar connective tissue)
 Cellular (Cellular connective tissue)
 Vascular (Vascular connective tissue)
 Special
Adipose
 Reticular
 Lymphoid
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Pigmented
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Classification of Dense connective tissue
Irregular (Dense Irregular connective tissue)
Regular (Dense Regular connective tissue)
White fibrous tissue
Yellow elastic tissue
Hard (Skeletal connective tissue)
Cartilage
Hyaline
Non-Articular
Articular
Elastic
Fibrous
Bone
Compact
Spongy or Canccllous
Fluid like (Haemopoietic connective tissue)
Bone marrow or Myeloid tissue
Blood
COMPONENTS OF
CONNECTIVE TISSUE
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There are three components of
connective tissue:
1. Cells
2. Fibers
3. Ground substance
Cells
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Mesenchymal cells
Fibroblasts
Macrophages
Plasma cells
Mast cells
Fat cells
Reticular cells
Lymphocytes
Pigment cells
Fibrocytes
Fibers
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Following types of fibers are
found in different types of
connective tissues.
1. Collagen fibers
2. Reticular fibers
3. Elastic fibers
Mesenchymal connective
tissue
 It is also called Mesenchymal connective
tissue or simply mesenchyme.
 In fact it is nothing but embryonic
mesoderm, may be extraembryonic or
intraembryonic mesoderm.
 It is typical unspecialized connective
tissue of early weeks of embryonic life.
 It is composed of mesenchymal cells
and matrix.
 Mesenchymal cells have branching processes.
 They often appear to join those of neighboring cells,
although they do not form a true syncytium.
 Ground substance is a coagulable fluid in the earliest
stages but later contains fine reticular fibers.
 So matrix consists of ground substance and fine
reticular fibers.
 The mesenchymal cells and reticular fibers are
gradually replaced by mature types of cells (e.g.
fibroblasts) and collagen fibers respectively as the
mesenchyme develops and differentiates into the adult
connective tissue.
Undifferentiated Mesenchymal
cells:
 They are small and stellate in shape,
usually located along the walls of
blood vessels, particularly capillaries,
where they are referred to as
perivascular or adventitial cells.
 They can differentiate into the usual
cell types found within loose
connective tissue or into smooth
muscle cells of blood vessels when
required.
Mucoid tissue
 It is also called mucoid or mucous
connective tissue.
 It is an intermediate type of
connective tissue, found chiefly as a
stage in the development of connective
tissue from mesenchyme to the adult
type.
 It also exists as Wharton's jelly,
which form the bulk of umbilical cord,
where it does not differentiate further.
 It consists of a copious matrix and large
stellate cells called fibroblasts.
 The matrix is largely made up of soft and
jelly like ground substance and a fine
meshwork of collagen fibers.
 Usually few fibers occur in typical mucoid
tissue, though at birth the umbilical cord
shows a considerable development of
perivascular collagen fibers.
 Fibroblasts have oval nuclei and branching
processes often appear to fuse with those of
neighboring cells. A few macrophages and
wandering lymphocytes are occasionally found.
 SITES:
In addition to umbilical cord, after birth, mucoid
tissue is still to be seen in the pulp of a
developing tooth. In the adult the vitreous body
of the eye and the nucleus pulposus of the
intervertebral disc are persistent forms of
mucoid tissue in which the fibers and cells ore
very few in number,
 Umbilical Cord
The two arteries and one vein (upper left)
of the umbilical cord are surrounded by a
large amount of connective tissue.
 The proportion of "ground
substance" is higher in this
tissue, and it is sometimes called
"Wharton's jelly".
 Umbilical Cord
A closer look shows the preponderance
of ground substance (largely
glycoproteins and proteoglycans) and
relatively few cells.
Loose connective tissues
 It is formed by direct differentiation of
mesenchyme.
 It is loosely arranged and fibroelastic.
 It binds other tissues, organs
and their components together.
 Owing to its flexibility, it allows a
considerable degree of mobility between
different structures and organs.
 It contains fibroblasts, macrophages,
reticular cells, plasma cells, mast
cells, and lymphocytes.
 Neutrophils and eosinophils are also
seen.
 Collagen fibers are most prominent.
 Elastic fibers form a continuous
branching network.
 Reticular fibers are present in the
loose connective tissue that borders
upon other structures.
 Loose connective tissue derives its name
from the fact that its fibers are loosely
arranged. The cells and fibers are
embedded in fluid like ground substance.
 SITES:
Loose connective tissue is
widely distributed in the body. In
fact it occupies any unoccupied
space in the body.
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Loose connective tissue is of
two types:
 Ordinary loose connective
tissue
 Special loose connective
tissue
 Ordinary loose connective tissue:
 There are three varieties of
ordinary loose connective tissue.
Areolar connective tissue:
 The name areolar is descriptive of the general
appearance produced by small spaces, which contain
only an amorphous ground substance, which is
usually not seen because it is washed off in routine
preparations. Here the most common cells are
fibroblasts and macrophages. Fat cells
(adipocytes) are seen in small groups,
particularly around blood vessels. Reticular
cells, plasma cells and mast, cells are also seen.
Lymphocytes are scattered throughout the areolar
tissue.
SITES:
 It forms all the superficial fascia and part of
the deep fascia e.g. cribriform fasia.
 It also forms Submucosa and mucosa
(lamina propria) of digestive, respiratory and
urogenital tracts.
 It also covers these tracts.
 Here it is in the forms of fibrosa or
subserous connective tissue.
 Fat free subcutaneous connective tissue as
in eyelids, penis, scrotum and labia is also
areolar connective tissue.
 It is found between and around
muscles, nerves and blood vessels,
particularly endomysium and
endoneurium.
 Similarly it is also found around and in
the tendons, aponeurosis and
ligaments.
 It is present underneath the
endothelium as subendothelial
connective tissue and forms the
adventitia of the blood vessels.
 It covers certain organs such as
pancreas, kidneys etc.
 It divides the organs and glands
into lobes and lobules and even
present within the lobules.
 Here it is called Interlobar,
interlobular and intralobular
connective tissue.
Cellular connective tissue:
 When the cellular component
increases the loose areolar
connective tissue becomes
cellular connective tissue.
 SITES:
 Cortex of the ovary
Vascular connective
tissue:
 When the blood vessels increase in a loose
areolar connective tissue, the tissue is given the
name vascular connective tissue.
 SITES:
 Medulla of the Ovary
 In fact in a loose connective tissue according to
the requirements ALLAH subhanahu Taala
increases the cellular element or vascular
element, human beings name it cellular
connective tissue or vascular connective tissue
accordingly.
CELLS OF
LOOSE
CONNECTIVE
TISSUE
Fibroblasts
 These are one of the two most
numerous cells of areolar connective
tissue, the other being macrophages
or Histiocytes. Fibroblasts, as their
name suggests, are considered to be
responsible for the formation of the
fibers and also are thought to
elaborate most, if not all, of the
amorphous component of the matrix
(principally glycosaminoglycans ).
 They are large, flat, branching cells,
which appear fusiform, or spindle
shaped in profile.
 The branching processes are slender.
In most histological preparations, the
outlines of the cells are indistinct.
 The nucleus is deeply stained with
basic dyes.
 It is oval or elongated with one or two
nucleoli and finely granular chromatin.
 In young fibroblasts, which are actively
engaged in protein synthesis the high
concentration of granular endoplasmic
reticulum.
 Mitochondria appear as slender rods and are
most numerous near the nucleus.
 Golgi apparatus is also present close to the
nucleus.
 Microtubules are also present and seem to be
required for translocation of secretary vesicles.
Fibrocytes
 The old and relatively inactive
fibroblasts are given the name
fibrocytes.
 Here the cytoplasm is sparse
and only weakly basophilic, the
endoplasmic reticulum is scanty.
 The nucleus is flattened and
heterochromatic (close-faced).
Macrophages
 ALLAH Subhanahu Taala has
placed important agents of
defense in the body called
macrophages.
 They are almost as numerous as
fibroblasts in loose connective
tissue and are more abundant in
richly vascularized areas.
 Generally they are irregular shaped cells with
processes, which usually are short and blunt.
 Occasionally they may exhibit long, slender branching
processes.
 They are relatively larger cells (15-20um in diameter).
Their nuclei are ovoid, usually indented and
heterochromatic.
 Nucleolus is present but not so conspicuous.
 The cytoplasm is mildly basophilic and typically has a
frothy appearance under the light microscope.
 Ultrastructurally, macrophages contain numerous
lysosomes, which digest ingested material.
Macrophage
 The macrophage is derived from the
blood-borne monocyte, which
migrates into tissue and differentiates into
this phagocytic cell.
 Here it is stained blue after gobbling up
trypan blue stain.
 Look for the irregular cell border and
numerous phagosomes.
 ALLAH Subhanahu Ta`ala has enabled
macrophages to multiply mitotically
to some extent, but he develops
them largely from haemopoeitic
stem cells in the bone marrow,
circulates in the blood as
monocytes before sending them
to their final extravascular sites
through the venule walls.
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There are two types of macrophages:
1. Stationary or fixed macrophages:
Attached to fibers of the matrix. They are
irregular with many filopodia.
2. Motile or nomadic macrophages:
Free with in the matrix. They are of
a more rounded and regular form.
 Macrophages are important
phagocytes, forming part of the
macrophage system. They are
also able to dispose of dead or
moribund cells prior to tissue
regeneration. Because of their
mobility and phagocytic activity,
they are able to act as
scavengers, engulfing
extravasated blood cells, dead
cells, bacteria, and foreign
bodies.
Fat cells
 There are two types of fat cells:
 Unilocular fat cells
 Multilocular fat cell.
Mast cells
 ALLAH Rab-ur-Ezzat has blessed us with very
important type of defense cells called
mast cells.
 They are widely distributed in loose connective
tissues and often preset in the fibrous capsules
of certain organs such as liver.
 They are characteristically numerous
in relations to blood vessels and
nerves.
 Mast cells are irregularly oval in
outline, about 12um in diameter, with
short pseudopodia, an indication of
their slow mobility.
 The nucleus is centrally placed and
relatively small.
 They are easily identified by large number of
prominent Cytoplasmic granules.
 Mast cells also contain a well developed Golgi
apparatus and scanty endoplasmic reticulum.
 The Cytoplasmic granules or vesicles are water
soluble and exhibit metachromasia (staining a color
different from the dye being used) with basic dyes
such as toludine blue, methyline blue, alcian blue and
azure A.
 These basic dyes instead of giving usual basic dyes
colors produce.
 The normal basic dyes usually stain blue
like colors. The acidic dyes stain red like colors.
 Instead of giving blue colors the basic dyes here give
purple red color to Cytoplasmic granules.
 This metachromatic response of these Cytoplasmic
granules.
 The granules also show a strongly positive reaction
with periodic acid-Schiff PAS).
 Electron micrographs show that a unit membrane
bound the granules and their average diameter is
0.5um.
 Thegranules usually contain dense osmiophilic
material, which may be finely granular, lamellar, or in
the form of membranous whorls; these variants may
coexist in the same vesicle, which may also present,
in places a crystalline substructure.
 For these reasons they have sometimes been termed
compound granules.
Mast Cells
 The numerous granules of the
mast cells take up the toluidine
blue stain and appear more
"purple" than other stained cells.
 Histamine released from the
mast cell plays a key role in
inflammation.
Plasma cells
 These cells are found frequently
in
 serous membranes and
 lymphoid tissue and
 are plentiful in sites of chronic
inflammations.
 ALLAH Subhanahu has made its
nucleus rounded and placed it
eccentrically in a basophilic
cytoplasm.
 The chromatin material is
arranged like the spokes of a
wheel or hours on the clock.
 So nucleus presents a cartwheel
or clock face appearance.
 There is a lighter stained area in
the cytoplasm close to the
nucleus containing Golgi
apparatus and centriole.
 ALLAH Subhanah has provided
these cells an extensive rough
endoplasrnic reticulum for the
production of antibodies.
 Occasionally acidophil inclusions
called Russell bodies are seen in
the cytoplasm.
Plasma Cells
 Plasma cells are easily
distinguished by their oval shape
and large, offset nucleus with
chromatin clumped in a
"clockface" pattern, and an
adjacent pale patch of clear
cytoplasm.
 Plasma cells are derived from Blymphocytes and secrete
antibodies.
Collagen fibers:
 These are found in all types of
connective tissue and consist of protein
collagen.
 In the fresh state, e.g. in tendons, they
appear white, and hence also are termed
“white” fibers.
 They are extremely tough and
tend to form bundles.
 Within a bundle, fibers are held
together by a small amount of
amorphous cement substance
(mucoprotein).
 Individual collagen fibers vary
from 1 to 12 um in diameter.
 The fibers are of indeterminate
length and have a straight or
wavy course.
 They are soft and flexible, relatively inelastic,
and have high tensile strength.
 They are transparent and homogeneous but
show a faint longitudinal striation.
 It is found under higher magnifications that they
are composed of smaller fibers held together by
amorphous material. These smaller fibers are
called fibrils. There diameter is 0.2 to 0.5 um.
These fibrils are aligned in a parallel direction,
giving the appearance of a longitudinal striation.
 Collagen is a protein, which stains with most
acid dyes. Hence the fibers are stained pink/red
with eosin, red by van Gieson’s picrofuchsin
and blue by aniline blue of Mallory’s connective
tissue.
 They are stained green or blue in Masson’s
trichrome stain depending upon the
modification used I.e. methylene blue or green.
 They are stained yellow or brown after silver
impregnation (Bielchowsky’s method).
 Collagen fivers give a week reaction to periodic
acid-Schiff (PAS) technique.
Collagen Fibers
 The Masson (trichrome) stain
leaves collagen green or blue.
 In the skin, Type 1 collagen
predominates, as shown by the
thick, wavy bundles.
 Electron micrographs show that each of the
collagen fibril is composed of still smaller fibrils
called microfibrils.
 The later are relatively uniform in diameter in
any given connective tissue e.g. in adult human
dermis, they are about 100 nm in diameter
throughout dermis: but vary in different
locations and in different stages of
development, ranging from about 20 to200 nm.
 Studies using autoradiography, electron
micrography and sophisticated biochemical
techniques have shown that collagen
microfibrils are composed of collagen
molecules called tropocollagen. Each molecule
is approximately 280 nm long and 1.5 nm wide.
Alignment of these macromolecules is end-toend, but not touching, and with the molecules in
adjacent rows arranged in parallel but
staggered about one-fourth of their length. This
gives rise to the 64-nm periodicity of collagen
commonly seen by electron microscopy.
Elastic Fibers
 Sheets of elastic fibers, called elastic
lamellae, are common in the aorta,
shown here.
 These lamellae give a distinctive
refractive appearance when you focus
through them.
Reticular Fibers
 Reticular fibers are composed of
type III collagen, and appear
black with a silver stain.
 In many organs and basement
membranes, they provide a
supportive framework.
Loose Connective Tissue
 Loose CT in the duodenum (see
the Brunner's glands?) is a
"space filler" that provides the
flexibility the GI tract needs.
 Many of the nuclei present are probably
fibroblasts, but other cell types common
in loose CT include plasma cells, mast
cells, and lymphocytes.
Loose Connective Tissue
 Loose CT is also found in the
mesentary (surrounding the
blood vessels and Pacinian
corpuscle), and in addition to the cell
types mentioned previously, loose CT
may include adiopocytes.
Dense Irregular CT
Tendon
 In cross section, collagen fibers make up
the pale pink background.
 The fine lines separate fiber bundles;
numerous fibroblast nuclei can be seen.
 Tendon
Longitudinal, wavy fibroblasts run along
the tendon. Recall that the collagen and
elastic fibers of the tendon are
extracellular.
 Tendon
Here the tendon has far fewer fibroblasts.
Notice the presence of skeletal muscle
marks the point of insertion.
 Tendon
Typically the tendon is characterized by
fibroblasts in regular, parallel
arrangements, as shown here.
 These are often described as "boxcars"
in a line (at least by railroad aficionados).
Look Alikes:
 Smooth Muscle, Skeletal Muscle, Nerve.