Connective Tissue(C.T.) The mesodermal ………………. to mesenchymal tissue(undifferentiated mesenchymal cells&hemogenous intercellular substance of proteins The mesenchymal tissue are differentiated in the embryo into 1-connective tissue C.T. 2-vascular tissue 3-smooth muscle

 The connective tissue formed of  A-C.T. cells  B-C.T. fibers  C-C.T.matrix

Types of C.T.  According to the nature of intercellular matrix  we have 3 types of connective tissue  1-C.T. proper( soft matrix)  2-cartilage (rubbery matrix)  3-Boney ( solid matrix)

1-Connective tissue proper  It is called connective because is support,binds&connection various tissue and organs

The C.T. is formed of  1-C.T. cells  2-C.T.fibers  3-Soft matrix or ground substance

Types of connective tissue proper  The cells &C.T. fibers are present in the  soft C.T.

6 (Six)Types of C.T. Proper  1-areolar C.T.  2-yellow elastic C.T.  3-Mucoid C.T.  4-White collagen C.T.  5-Adipose C.T.  6-Reticular C.T.

Types of Connective tissue cells  1-Fixed C.T. cells as  2-Free C.T.Cells

1-Fixed C.T. cells as:  1-fibroblast,  2-fixed macrophages,  3-fat cells,  4-mesenchymal cells,  5-pericyte cells,  6-endothelial cells  7-reticular cells

Fibroblast&Fibrocytes Cells  -develop from mesenchymal cells&pericytes  -It is very numerous in areolar C.T.  -basophilic cytoplasm  -The cytoplasm is rich in RNA,ER,GA,Mitochondria  -fibroblast can divide  -Fibroblast can changes into myofibroblast

Function of Fibroblast  - Form collagen,elastin&reticulin substances in order to form C.T.fibers  -Form the mucoprotein of the C.T. matrix  increase number during healing of wounds  Fibroblast change into myofibroblast which close wounds

Fibrocytes === mature fibroblasts  - Small spidle shaped cells with dense nuclei  - Acidophilic cytoplasm  -can not divide

LM of fibroblasts (arrows)

SEM of fibroblasts

2-Fixed macrophages or histocytes cells  -dervied from blood monocytes  - more present in the damaged C.T.  -have irregular cell membrane  -cytoplasma is not clear-rich in lysosomes  -the nucleus is small,kidney shape  -Histiocytes cells can be stained with vital stain as trypan blue

Function:  -Defence mechanism of the body  -can engulf(eat)foreign bodies,bacteria and old blood cells  -can clean wound from foreign bodies&debris  -can transport antigens  -macrophage………multinucleatd gint cells…..enclose large foreign bodies in order to destroy them

3-Adipose cell or fat cells or adipocytes  -derived from mesenchymal cells  - flat peripheral nucleus  -there are 2 types of fat cells  1-unilocular white fat cells  2-multilocular brown fat cells  -Fat cells can not divide  Stained :  orange with sudan III,black sudan black

Function  -brown fat responsible for energy reservoir&heat production  -white fat cells release energy during starvation  - support organs as kidney  -they act as heat insulator

4-The Mesenchymal Cells(UMC)  -embryonic branched cells called(UMC)  -has large oval nucleus&basophilic cytoplasma  -present in the embryonic tissue  Function:  Can differentiate into other types of C.T.

5-The Pericyte cells  -pale branched cells(peri= around)  -present immediate external to the endothelium of blood vessels capillaries&small venules  -persistent in adult life

Function:  Give rise to both fibroblast&smooth muscle cells  -role in the process of healing of connective tissue  -modified to form myoepithelial cells which can contract

6-The Endothelial Cells  Present in the surface of blood capillaries&blood vessels  -develop from the embryonic mesenchymal cells

Function:  1-synthesise collagen(type 4 collagen)  2-can form the basal lamina of the endothelium  3-divide rapidly.. give rise..endothelial cells of lung capillaries to secret angiotensin converting enzyme

7- Reticular Cells  -present in mainly in the reticular C.T.  -modified fibroblast which are specialized to secrete reticular fibres  -reticular cells are found in the stroma of bone marrow,lymph nodes,spleen,liver,pancreas

Function:  Supportive&phagocytic cells  -form the stroma of glands&bone marrow  -removal cellular debris from the lymphatic tissue

2-Free C.T. Cells  1-Mast Cells  2-Plasma Cells  3-Free Macrophages,  4-Blood Leucocytes  5-Melanophore Cells

1-Mast Cells 2-Histamine secretory mast cells  Present under mucosa of respiratory &digestive tract  Histamine…………….contract smooth muscle  Dilated blood vessels capillaries  Increased the capillary permeability

 -Small cells,round,irregular in shape  -present in groups blood vessels  Types of mast cells  1-Heprin secretory mast cells  Present in the C.T. of skin,secret heprin which is an anticoagulant

TEM of a Mast Cell

LCT – M = mast cell; P = plasma cells; F = fibroblasts; Eo = eosinophils, N = neutrophils

Function:  -Secrete heparin or histamine  (paracrine cells)  -release chemical mediators as immediate hypersensitivity  Factors which may cause of anaphylactic shock

2-Plasma Cells  Present  peritoneum, submucosa of digestive  respiratory tract,  lymph nodes&spleen  -originate from plasmablast cells which develop from B-lymphocytes  -small&round with hemogenous basophilic cytoplasm

Function:  -secrete specific antibodies against organisms&foreign bodies antibodies circulate in the blood termed(humoral antibodies)&processes is called humoral immunity  -Can not divide  -Have no phagocytic activity

3-Free Macrophages  -derived from blood monocytes after their migration to C.T.  -their cytoplasma is rich in lysosomes&RER  -they have oval eccentric nuclei

Function:  -Immun system of the body  -they are highly phagocytic cells  -secrete collagenase&elastasa enzymes&lysozome  -kill certain viruses through secretion of interferon

4-Bolood Leukocytes  Appear normaly in the C.T.of the following body organs  -Eosinophils&basophils  Found in C.T. of respiratory intestinal&female genital tract  -they increase in allergic condition

 -Lymphocytes&monocytes  Present in many organs  -increased in number in chronic infections  -Neutrophils:  -They migrate from blood vessels of C.T.  -where acute infection is present in order to phagocytose microorganism

5-Melanophore pigment cells  -They are C.T.macrophages which phagocytose melanin Pigments are formed by the melanocytes  -melanophores are branched cells with small round nuclei  -melanophore are rich in melanin pigments

Function:  -They carry melanin pigments

Types of C.T.Fibers  There are three(3) types of C.T.  1-white collagennous fibers  2-yellow elastic fibers  3-reticular fibers

1-White Collagenous Fibers  Shape:  colourless wavy branching bundles,the fibers run paralled to each other  Charcter:  soft,strong&flexible but not elastic fibers

 Structures:  formed of protein known as(collagen)which can be digested by pepsin&trypsin enzymes  Staining:  collagenous fibers are acidophilic,stain pink with eosin,red in van-Gison&blue with Mallory stain

Types of collagen  There are five(5) types of collagen  1-Type I collagen:  Present:  losse C.T.,White fibro-cartilage,bone&teeth this type is formed by fibroblast,osteoblast,odontoblast  2-Type II collagen:  hyaline&elastic cartilage&formed by chondroblast

 3-Type III collagen:  skin,smooth muscle&reticular fibers formed by fibroblast&by smooth muscle cells  4-Type IV  collagen: basement membrane of epithelial tissue&lenes of eye,It formed by fibroblast&by endothelial cells  5-Type V collagen:  in placenta,it is formed by fibroblast

2-Elastin fibers  Shape:  fine,straight branching fibers  Carachter:  the fibers branched&anastomose with each other  They run singly&not in bundles  Appear yellow in fresh state

 Structures:  formed of protein known as elastin which is resistant to chemical and to boiling  Can digested by the pancreatic elastase enzyme  Staining:  brown with orcein,black with verhoeff and yellow with van-Gison

Orecin Stain for Elastin – purple “ribbon candy”

3-Reticular Fibers  Shape:  they are thin,branched anastomose to form anetwork or reticulum  Strucures:  -formed of protein known as collagen type III  -Staining: Black with silver

Sliver Stain for Reticular Fibers

PAS stain of epithelial basement membranes (BM)

TEM of collagen fibers with 64 nm periodicity

TEM of extracellular collagen fibers (Cl)

Masson’s Trichrome Stain – blue = collagen

Areolar Tissue Pink = collagen Purple = elastin

TEM of a Plasma Cell

LCT – M = mast cell; P = plasma cells; F = fibroblasts; Eo = eosinophils, N = neutrophils

TEM of a Macrophage