Connective tissue originates from mesoderm and supports the body's structures. It consists of cells, fibers, and a ground substance. There are several types of connective tissue cells including mesenchymal cells, fibroblasts, fibrocytes, reticular cells, endothelial cells, pericytes, fat cells, and fixed macrophages. Connective tissue performs important functions such as structural support, metabolism, defense, tissue repair, and energy storage.

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2. CONNECTIVE TISSUE
 It originates from the mesoderm
 Support the body and its structures like tissues
and organs
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CONNECTIVE TISSUE

3. General characters
It consists of
 CELLS
 FIBERS
 MATRIX ( Ground substances)
CONNECTIVE TISSUE
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4. CONNECTIVE TISSUE
Types:
1. Connective tissue proper
2. CT Special types Like ,
 Bone
 Cartilage
 Blood
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5. CONNECTIVE TISSUE
Function
1- Structural support
2- Metabolic function
3- Defensive function
4- Tissue repair
5- Special function as energy storage in adipose tissue, blood cell
formation
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6. CONNECTIVE TISSUE
CT Cells a- Fixed ,
b- Free
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7. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 7

8. CONNECTIVE TISSUE
Free cells
 Plasma cells
 Mast cells
 Pigment cells
Leucocytes
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9. CONNECTIVE TISSUE
CT fibers
1.Collagen fibers
2.Reticular fibers
3.Elastic fibers
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10. CONNECTIVE TISSUE
CT Ground substance(Matrix):
May be
 Liquid as in Blood
 Gelatinous like areolar CT
 Rubbery as in Cartilage
 Hard as in Bone
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11. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 11

12. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
It is called Embryonic stem cell, remains undifferentiated in
adult CT
 Light Microscopy (L/M) small cell with long cytoplasmic
processes, fainty basophilic cytoplasm
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13. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
 Elecron Microscopy (E/M) (cell making protein)
Cytoplasm contains Golgi apparatus, rough endoplasmic reticulum,
mitochondria, ribosomes
Function: Stem cell for most of CT cells.
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15. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 15

16. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
Fibroblast : is the most common cell in the CT
LM: fusiform or stellate with long process cell, pale stained
nucleus with Basophilic cytoplasm
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17. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
Fibroblast : is the most common cell in the CT
EM: Euchromatic Nucleus, prominent nucleolus
Cytoplasm has the protein secreting organelles (Golgi
apperatus, rough endoplasmic reticulum,
mitochondria, ribosomes)
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18. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
Fibroblast : is the most common cell in the CT
Function:
 Growth, repair of the CT
 Synthesis,secretion, maintains the extracellular matrix as fibers and ground
substance.
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19. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 19

20. CONNECTIVE TISSUE
Fibrocytes
It is considered as inactive form of the fibroblast
LM: small fusiform , deep basophilic nucleus,
acidophilic cytoplasm
EM: the cytoplasm contains few organelles
FUNCTION: tissue repair
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21. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 21

22. CONNECTIVE TISSUE
LM:
 stellate cell with long and thin cytoplasmic processes,
 rounded nucleus,
 fainty basophilic cytoplasm
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Reticular cells

23. CONNECTIVE TISSUE
Reticular cells
 EM: (cell making protein)
Cytoplasm contains Golgi apperatus, rough endoplasmic reticulum,
mitochondria, ribosomes
FUNCTION:
 stroma formation,
 reticular fibers synthesis
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24. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 24

25. CONNECTIVE TISSUE
Endothelial cells
 It is a simple squamous epithelium
 Lines the interior surface of the circulatory system
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26. CONNECTIVE TISSUE
Endothelial cells
LM:
Shape : flat cell ,
Nucleus : flat nucleus,
Cytoplasm: thin cytoplasm
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27. CONNECTIVE TISSUE
Endothelial cells
EM: the cytoplasm contains few organelles
FUNCTION:
o facilitate the exchange of the substances across the
vascular wall,
o Produce type 4 collagen fibers.
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28. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 28

29. CONNECTIVE TISSUE
Pericytes
 It is partially surrounds the endothelial cells of capillaries and
small venules
 It is a perivascular cell with multifunctions .
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30. CONNECTIVE TISSUE
Pericytes
LM:
Shape: has long processes and share in Gap junctions with
the endothelial cells
Nucleus: Flat
Cytoplasm: Thin
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31. CONNECTIVE TISSUE
Pericytes
EM: the cytoplasm contains myofilaments
FUNCTION: It can be differentiate into
 Fibroblast in healing ,
 Macrophage if needed,
 Smooth muscle during the development of the new blood vessels.
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32. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 32

33. CONNECTIVE TISSUE
Adipose cell
There are two types
A.Unilocular adipose cell
B.Multilocular adipose cell
Function:
Storage and release of fat
Plays an important role in energy homeostasis
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34. CONNECTIVE TISSUE
LM:
Shape : Large spherical cell
Nucleus : flat and displaced , cytoplasm shows a single lipid droplet
in a signet ring appearance
Special stain: Sudan Black, osmium tetraoxide black
EM: the cytoplasm contains few organelles
Unilocular Adipose cell
It forms the white adipose tissue
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35. CONNECTIVE TISSUE
Multilocular adipose cell
It forms the brown adipose tissue
LM:
Shape : small polygonal cell
Nucleus : eccentric rounded nucleus
Cytoplasm: strongly acidophilic in H&E stain.
EM: the cytoplasm contains mitochondria, smooth endoplasmic
reticulum.
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36. CONNECTIVE TISSUE
Fixed cells are relatively stable
Include: ( ME-RE-PER-END, 4F)
1. Mesenchymal cells
2. Fibroblasts
3. Fibrocytes
4. Reticular cells
5. Endothelial cells
6. Pericytes
7. Fat cells
8. Fixed macrophages Dr. M.Attia 36

37. CONNECTIVE TISSUE
Fixed macrophages
Originate from the blood monocytes
Types:
A. Fixed macrophages setteled in CT
B. Free macrophages travel between Ct and Blood
Macrophages are distributed in most organs and tissues and form
mononuclear phagocytic system
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38. CONNECTIVE TISSUE
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39. CONNECTIVE TISSUE
Fixed macrophages
LM:
Shape : irregular
Nucleus : large eccentric nucleus
Cytoplasm: acidophilic in H&E stain.
Special stains: Vital stains ( Trypan blue or Indian Ink)
EM: the cytoplasm contains mitochondria, rough endoplasmic
reticulum, lysosomes, phagosomes, residual bodiesDr. M.Attia 39

40. CONNECTIVE TISSUE
Fixed macrophages
Function
1- Tissue cleaning by removing debris, dead cells, foreign
substances.
2. Defensive function
3. Immunological function
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