Dr.Manal OthmanAnatomyDepartment

CMMS,AGU

GENERAL HISTOLOGY3. Connective

Tissues

Biology-232

Connective Tissue

§ Supportsandconnectstissuesandorgans.

Connective Tissue (C.T.)

Cells ExtracellularMatrix

Fibers GroundSubstance

Collagen Elastic Reticular

EXTRACELLULAR MATRIX

� Extracellular matrix is mainly composed of fibrillar proteins (CT fibers) and glycosaminoglycans.� The 3 Fibrillar componenets:

1. Collagen (tensile support)

2. Elastic (stretchable fiber)

3. Reticular (fibers) = Type III collagen (stroma of some organs)

Connective Tissue Cells1) Fibroblast/Fibrocyte – synthesize the fibers and extracellular

matrix. Permanent resident.

2) Adipocyte – stores fat (energy), Permanent resident.

3) Mast Cell –Filled with basophilic granules, inflammatory mediators

4) Macrophage (histiocytes)– derived from blood monocytes, phagocytosis and defense

Connective Tissue Cells5) Plasma cells arise from lymphocytes, present more

in loose CT, resp, and GIT. Immunologic

6) Leukocytes: neutrophils (microphages) Defense against bacterial invasion, eosinophils and basophils (defense and allergy). Immunologic

7) Lymphocytes: either large or small.Immunologic

Fibroblasts

• Synthesize collagen, elastin, proteoglycans, glycosaminoglycans, & multi-adhesive glycoproteins

• Most common cells in the CT & responsible for synthesis of extra-cellular matrix components

• Stages of the fibroblast activity:> Active – fibroblast> Quiescent – fibrocyte

Fibroblasts

Macrophages / Mononuclear Phagocyte System

• Derived from bloodprecursor cells monocytes

• Mature in CT • Act as defense elements (lysosomal

enzyme activity) & antigen-presenting cells

• Distributed throughout the body, • Kupffer cells, Microglial cells, Dust

cells, Osteoclast

Mast cells • Are oval to round CT cells, • Small, spherical nucleus, centrally

located• Cytoplasm filled with basophilic

secretory granules which contain histamine, heparin, & serotonin

• Principal function: inflammatory response

• present more in skin, respiratory and GIT

• Surface of mast cells has receptors for IgE

• Increase in allergic reaction

Plasma Cells• Are large ovoid cells

with basophilic cytoplasm due to RER

• Nucleus is spherical and eccentrically placed and contains compact coarse heterochromatin alternating with lighter areas of approximately equal size (clock face appearance).

• Responsible for antibody formation.

AdiposeCells

• AreCTcellsthatarespecializedforstorageoffatsorfortheproductionofheat

• AlsocalledFatcells• Signet-ringcells

Fibers of CT1) Collagen fibers: tough, thick, fibrous, proteins, do not

branch, most abundant fibers. There are many types of collagen:

Type I: dermis of skin, tendons, boneType II: hyaline cartilage, and elastic cartilage, Type III: the reticular fibers, Type IV: the basal lamina of the basement membranes.Type V: associated with type I and in placentaType VII: basal lamina

Fibers of CT2) Elastic fibers: thin small branching, contain protein elastin. Stretchable, responsible for elastic recoil, present in lung, bladder, skin, big blood vessels.

3) Reticular fibers: type III collagen, delicate framework in lymph nodes, spleen, bone marrow, lung, liver. Visible if the tissue is stained with silver stain.

C.T.Proper SpecialC.T.

Loose Dense

Regular Irregular

AdiposetissueElastictissueReticularSupportingtissue(Cartilage&Bone)MucousBlood

Connective Tissue

Loose CT

Loose CT

Dense C.T. (Regular)

Ex: In Tendons

Collagen fibers

Nuclei of fibroblasts

Dense C.T. (Irregular)

Ex: In Skin

Elastic CT

Eg: Regular in ligament in the back of neck andIrregular in wall

of large arteries as aorta

Reticular CT

Ex: In Liver, lung spleen, lymph node

Adipose CT

Mucoid CT

Site: In Umbilical cord

CARTILAGE• Specialized form of supportive C.T. in which the

extra cellular matrix is firm and contains collagen.• Cartilage cells are called chondrocytes.

• 3 types of cartilage identified by the types of fibers in the extra cellular matrix:

1.Hyaline (typeIIcollagen);commonest(articular,costal,trachea).

Chondrocytes

2.Elastic (elasticfibers,typeIIcollagen),ear,epiglottis.

Chondrocytes

3.Fibrocartilage(typeIcollagen)intervertebraldiscs.

Chondrocytes

BONEo Specialized supportive C.T. in which the extracellular matrix is calcified (very hard).o3 Bone cells are: Osteoblast (bone forming), osteocyte and osteoclast (bone remoddeling).

Compact

Spongy

2 types of adult bone: Compact and spongy (Cancellous).

Compact Bone Cancellous Bone

BLOOD• Considered as a special type of C. T. in which the

extra cellular matrix is fluid (plasma).

• The blood cells suspended in the plasma are:1. Erythrocytes (R.B.Cs) – transport O22. Leukocytes (W.B.Cs) – defenses against infection3. Platelets – promote coagulation (clotting)

w Erythrocytes are non nucleated biconcave disks containing O2–carrying protein (Hemoglobin).

w Leukocytes containing granules (Granulocytes) are the neutrophils, eosinophils and basophils.

w Leukocytes which do not have granules (Agranulocytes) are the lymphocytes and monocytes.

w Platelets (thrombocytes) are non nucleated, disk like cell fragments of the (Megakaryocytes of the bone marrow).

Blood Film

White Blood Cells

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