Transcript Lect.3.Connective ti..

Connective tissue
TYPES:
1-CT. proper.
2.Specialized CT (cartilage, bone and
blood).
Connective tissue proper
 Components of CT:
1-Cells.
2-Extracellular matrix (ground substances and fibers).
 Functions of CT:
a. Structural support
b. A medium for exchange.
c. Helps in defense & protection of the body.
d. A site for storage of fat.
Extracellular Matrix
I-Ground substance
It is a hydrated, amorphous material that is composed
of: Glycosaminoglycans, proteoglycans and adhesive
glycoproteins.
II-Fibers
Collagen fibers, are inelastic and possess great
tensile strength. Each fiber is composed of fine
subunits called tropocollagen molecule.
 Most of the fibers show axial periodicity by EM.
 There are six major collagen types:
Type I: in CT proper, bone, dentin.
 Type II: In hyaline and elastic cartilage.
 Type III: reticular fibers.( stroma of spleen &
lymph nodes)
Elastic fibers:
Structure of Elastic Fiber the fiber branch and
anastomose with each other they run singly and
not in bundles but forming a membrane.
Stretchable Fibers.
Collagen type I
CT.Cells
1.Fibroblasts
2.Adipose cells.
3.Pericytes.
4.Mast cells.
5.Macrophages.
6.Plasma cells.
7.leukocytes.
I- Fibroblasts
They are the most abundant CT. cells and derived from
undifferentiated mesenchymal cells.
 Types:
1- Active fibroblasts: are elongated, fusiform cells with darkstaining cytoplasm rich in RER with large ovoid nucleus
containing well-defined nucleolus.
2- Inactive fibroblasts (fibrocytes): are smaller and are more
ovoid with more acidophilic cytoplasm.
• Fibrobalsts are responsible for the synthesis of almost of
extracellular matrix.
• can close wound during injury.
II-Adipose cells (fat cells or adipocytes):
 They are derived from undifferentiated mesenchymal cells.
 They are fully differentiated and do not undergo cell division.
 There are 2 types:
A-Unilocular fat cells, form white adipose tissue: they are large cells, they
store fat as one droplet, which enlarge pushing the cytoplasm and the
nucleus peripherally against cell membrane (signet-ring appearance). They
have few mitochondria. The fat droplet is not bounded by a membrane.
Present in:
under the skin especially in females, it is more considered in the mammary
glands and gluteal region.
B-Multilocular adipocytes, form brown adipose tissue:
Are small cells with multiple fat droplets, central spherical nucleus and many
mitochondria.
Present In: new born.
* They function in the synthesis, storage and release of fat.
Adipocytes
III- Pericytes
 They surround capillaries and small venules.
 They have multiple processes that wrap around the
endothelium of blood capillaries and small venules.
Function:
1.Important in the healing of CT of blood vessles where ever
wound presents
2. give raise to smooth muscle cell
3. can modified for smooth muscle cells which can contract.
IV. Mast cells:
 Their cytoplasm is rich in membrane-bound
granules that stained metachromatically
with toluidine blue.
 The granules contain heparin, histamine.
Histamine causes vasodilatation and increase
permeability of blood vessels. It causes
bronchospasm and increase mucus
production.
Mast Cell
V- Macrophages
 Derived from blood monocytes after migrate from
blood from C.T.
 Some are fixed and others are transient .
 They are irregular in shape due to the present of
filopodia.
 They have branched cell with many process.
 Their cytoplasm Is basophilic, prominent RER, well
developed Golgi and an abundance of lysosomes.
 They derived from monocytes.
Macrophage
 VI- Plasma cells
 They are derived from B-lymphocytes after exposure
to an antigen.
 They secrete antibodies.
 They are large ovoid cells with
intensely basophilic cytoplasm that
is rich in RER and Golgi
(pale-staining region
adjacent to the nucleus
that has chromatin
radiating out from the
center (clock-face appearance).
VII- Leukocytes:
 They are white blood cells that circulate in blood
stream then migrate through capillaries to enter CT.
during inflammation, invasion by foreign elements
and immune response.
 In the present of infection.
Connective tissue proper
1- Loose (areolar CT):
 It fills in the spaces of the body just deep to the skin,
 The loose CT of mucous membranes is called lamina
propria.
 It is characterized by abundant
ground substance and tissue
fluid housing the fixed CT. cells,
undifferentiated cells and
collagen, reticular and elastic fibers.
Its ground substance loose.
2. Reticular CT:
Type III collagen is its major component.
Collagen forms mesh-like networks
It forms the framework of liver,
lymph nodes, spleen,
3. Adipose tissue:
It is divided into white (unilocular) adipose tissue and
brown (multilocular) adipose tissue. It is rich in blood
vessels.
Adipose CT.
4.
Dense CT:
It has many more fibers and fewer cells than
ordinary CT.It is formed of three types:
a. Dense irregular collagenous CT: it is formed of
randomly arranged collagen fibers, few ground
substances and fibroblasts scattering between
collagen fibers. It form the dermis of skin,
b. Dense regullar collagenous CT:
it is composed of coarse collagen bundles that
oriented into parallel sheets. It has few ground
substances and fibroblasts between collagen
bundles.Ex. Tendons.
Dense irregular CT. Dense regular CT
c. Dense regular elastic CT:
it has coarse branching elastic fibers and scattered
fibroblasts. Elastic fibers are arranged parallel to one
another and form either thin sheets or fenestrated
membranes as in large blood vessels (aorta).
Practical slides
Elastic connective tissue
Dense regular fibrous connective
tissue
Reticular connective tissue
(silver stain)
Adipose connective tissue
Loose (areolar connective tissue)