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Histology)Lecture)(4)) Connective))

Histology)Team)432)

Lecture'Objectives:' ) • Enumerate)the)general)characteristics)of)C.T.) • Classify)C.T.) • Classify)C.T.)proper)(C.T.P.)) • Describe)the)structure)(components))and)distribution)of) different)types)of)C.T.P.) • Discuss)clinical)applications)related)to)C.T.P.) Histology)lecture)(4)) Connective)Tissue) ! ! DEFINITION OF C.T: ! It is a basic type of tissue, of mesodermal origin, which provides structural & metabolic support for tissues &organs. ! !

Comparison:+The+Characteristics+of+C.T+&+Epithelial+Tissue+ #+ Connective+Tissue! Epithelial+Tissue! Distance+ Are formed of widely separated Adjacent cells are tightly joined. between+cells+ few cells.! ! Amount+of+ extracellular+ Abundant extracellular . Little intercellular space. matrix+ Presence+of+ most C.T. are vascular Avascular; because there is very vessels+ little space between the cells. Presence+of+ ------basement+ Rests on a . membrane+ Regeneration+ ------Regenerates quickly. ! Types of

! C.T. Proper . . . (C.T.P). !

! Loose!(Areolar)! C.T.! ! Dense!Collagenous! ! C.T.!

! Elastic!C.T.! COMPONENTS+OF+ C.T.P.+ ! Reticular!C.T.! !

2)+Extracellular+matrix+ ! Adipose!Tissue.! 1)+Cells+ (The+major+component+of+C.T.)+ !

Fibers.+

! Ground+substances+ !

1! ! Histology)lecture)(4)) Connective)Tissue) ! ! COMPONENTS+OF+ ! C.T.P.+

2)+Extracellular+matrix+ 1)+Cells+ (The+major+component+of+ C.T.)+

Ground+ .+ Fibers.+ substances+

Macrophages.+ +Fibers+ (Collagen+type+I):+ • NonBbranched!fibers,! arranged!in!bundles. • Acidophilic. Collagen+type+II+(in# Mast+cells.+ cartilage).+ !

Plasma+cells.+ Reticular+Fibers+ (collagen+type+III):+ • Form!a!network.! • Stained!black!with!silver. ! Adipose+cells+ Collagen+type+IV+ (,+ (in#basement# membranes)++ Fat+cells).++

Leucocytes.+ Elastic+Fibers:+ • Branched.! • Stained!brown!with!orcein.!

!

!

!

!

Collagen+Fibers+! (Collagen+type+I) ! Reticular+Fibers+ Elastic+Fibers+! ! (collagen+type+III) + ! ! ! !

2! ! Histology)lecture)(4)) Connective)Tissue) ! !

Cells+ L\M+ Function+ Under+LM+

(1) Fibroblasts+ • Flat!branched!cells! 1B Formation!of! ! (spindleBshaped)! !of! with!basophilic! extracellular! cytoplasm!(thus! matrix.! active).!! 2B!Healing!of! • They!can!divide.! wounds. • Old!fibroblasts!are! ! called!! (inactive).! ! (2)+ • Basophilic! Phagocytosis.! ! cytoplasm,!rich!in! ! lysosomes.! • Irregular!outlines. • They!can!divide.! • They!originate!from! monocytes. ! (3)+Mast+Cells • Cytoplasm!contains! Secrete!heparin!&! ! + numerous! .! cytoplasmic! ! granules.!! !

(4)+Plasma+ • Basophilic! Secretion!of! ! Cells+ cytoplasm!with!a! antibodies! negative!Golgi! (immunoglobulins).! image.! ! • Nucleus:!spherical,! eccentric!with!a! clockBface! appearance!of! chromatin.! • Derived!from!BB lymphocytes. !

3! ! Histology)lecture)(4)) Connective)Tissue) ! (5)+Adipose+ L/M+of+Unilocular+ • Storage!of!fat.!! ! Cells+ Adipose+Cells:! ! (Adipocytes,++ • Large!spherical,! Fat+ with!a!single!large!

Cells) fat!droplet.!!!!!!!! + • Thin!rim! (borderline)!of! cytoplasm!at!the! periphery.! • Nucleus:!flattened,! peripheral.!

!

B Loose!connective!tissue!→!most!common.! B Fibroblasts!are!rich!in!rough!endoplasmic!reticulum!and!ribosomes!in! order!to!form!the!basophilic!extracellular!matrix.! B Because!they!are!responsible!for!the!formation!of!antibodies,!which! are!proteins;!Plasma!cells!are!rich!in!rough!ER!and!ribosomes.!! B Adipose!cells!→!!rich!in!smooth!endoplasmic!reticulum!→!!form!lipids.! B Adipose!cells!appear!with!empty!cavities!under!the!microscope! because!one!of!the!steps!of!the!procedure!the!tissue!undergoes!during! the!preparation!of!the!slide!is!adding!xylene,!which!yields!to!the! dissolving!of!the!fat.!

! !

4! ! Histology)lecture)(4)) Connective)Tissue) ! !

Types+of+C.T.P+ L\M+ Sites+ Under+LM+ (1) Loose+ Contains!all!the!main! Subcutaneous!tissue.! ! (Areolar)+C.T.+ components!of!C.T.P.! + (no+predominant+ element+in+loose+ C.T.)+ !

(2) Dense+ Predominance!of! 1B!Dense+irregular:! ! Collagenous+ collagen+fibers+++ e.g.!!of!the! C.T. Fibroblasts.+(collagen! ,!capsule.! + bundles!separated!by! ! fibroblasts).+ ! 2B!Dense+regular:!! ! B!no!nuclei!present!in! e.g.!,! collagen!fibers,!only! . present!in!fibroblasts.!! !

(3) Elastic+C.T. Branching!elastic+ e.g.!Aorta.! ! + fibers+(or+ ! membranes)+++ Fibroblasts+(or+ smooth+muscle+ cells).!

(4) Reticular Reticular+fibers+++ !of!organs:! ! C.T. Reticular+cells! e.g.!liver,!lymph!node,! + (specialized! spleen.! fibroblasts).! ! !

5! ! Histology)lecture)(4)) Connective)Tissue) ! (5) Unilocular+ Is!formed!of!lobules!of! • Subcutaneous! ! Adipose+Tissue+ unilocular+adipose+ layers!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! (White+ cells.+ especially!in! Adipose+ + buttocks!&!hips.!

Tissue). + • Abdominal!wall. + Function:+ • Female!. Synthesis,!storage!&! • Around!the!kidney.! release!of!fat. ! !

! Clinical Applications:

Bronchial Asthma

Exposure!to!allergen!will!stimulate!mast!cells!in!the!,!which!leads!to!release! of!histamine!and!other!chemicals!that!lead!to!contraction!of!the!smooth!muscle! fibers!in!the!wall!of!the!bronchioles!(bronchospasm)!leading!to!dyspnea! (difficulty!in!breathing).

Obesity+!

1B!Hypertrophic+obesity:

It!results!from!the!accumulation!and!storage!of!fat!in!the!unilocular!fat!cells! (white!adipocytes).!These!cells!may!increase!in!size!up!to!four!times.

2B!Hypercellular+obesity:

It!results!from!an!increase!in!number!of!adipocytes,!which!may!be!attributed!to! increased!number!of!!precursors in!infancy.!

!

6! !