connective tissue contains cells, fibers and ground substance. cells include fibroblasts, undifferentiated mesenchymal cells, adipocytes and pigment cells also wandering cells. fibers include collagen, elastic, and reticular fibers.

1. CONNECTIVE TISSUE -I

2. • INTRODUCTION
• COMPONENTS
• FUNCTIONS
• CONNECTIVE TISSUE CELLS
• CONNECTIVE TISSUE FIBERS

3. INTRODUCTION
• Connective tissue are defined as those
composed predominantly of intercellular
material that is extracellular matrix which is
secreted by the connective tissue cells.
• The cells are therefore usually widely
seperated by their matrix, which is composed
of fibrous protein & a relatively amorphous
ground substance.

4. • The term connective is applied to a tissue that
fills the interstices between more specialised
elements.
• It is found in almost every part of the body
• It is conspicuous in some regions & scanty in
others

5. Connective Tissue
Cells Extracellular matrix
Fibres Ground substance
-Collagen
-Elastic
-Reticular
-Proteoglycans
-Glycoproteins
-Glycosaminoglycans
CONNECTIVE TISSUE COMPONENTS
Resident cells Wandering cells
-Fibroblasts
-Undifferentiated
mesenchymal cells
-Adipocytes
-Pigment cells
-Macrophages
-Mast cells
-Lymhocytes
-Plasma cells
-Other leukocytes

6. FUNCTIONS
• Connect, Bind, Support, Strengthen the
tissues
• Protects and insulates internal organs
• Major transport system
• Energy reserve and insulation against heat loss
• Repair as in wound healing
• Regeneration of tissues
• Defense of the body

7. CONNECTIVE TISSUE CELLS

8. CONNECTIVE TISSUE CELLS
RESIDENT CELLS WANDERING CELLS
•FIBROBLASTS
•UNDIFFERENTIATED -
MESENCHYMAL CELLS
•ADIPOCYTES
•PIGMENT CELLS
•MACROPHAGES
•MAST CELLS
•LYMPHOCYTES
•PLASMA CELLS
•NEUTROPHILS
•EOSINOPHILS
•BASOPHILS
•MONOCYTES

9. RESIDENT / INTRINSIC /
PERMANENT / FIXED
CELLS

10. 1.FIBROBLASTS
• Principal cell of connective tissue
• Synthesis of collagen, reticular & elastic fibers
& the complex carbohydrates of the ground
substance
• Reside in close proximity to collagen fibers so
called fixed cells

11. Appearance:
Surface view

12. Cross section

13. FIBROCYTES FIBROBLASTS

14. Inactive phase Active phase

15. E/M

16. RETICULOCYTE/ RETICULAR CELLS
• Fibroblasts secreting reticular fibers
• Reticular tissue: Fibrocellular network of
fibroblasts & delicate collagenous fibers
• Seen in liver, kidney, spleen & most lymphoid
tissues

17. Myofibroblasts
• H&E: bundles of actin filament with actin
motor proteins- nonmuscle myosin
• Expression of α- smooth muscle actin is
regulated by TGF-β1
• Fibronexus
• Mechanotransduction system

18. E/M

19. Role of myofibroblasts in wound repair
• Blood clot= fibrin+ blood cells
• 1-2 days: neutrophils & monocytes
• 3 days: macrophages replace neutrophils
• Role of fibroblasts & vascular endothelial cells
• 5 days: Granulation tissue bridges the incision
gap
• Fibroblats exert tractional forces on ECM

20. • Fibroblasts differentiate into myofibroblast
under the influence of TGF-β1 & mechanical
forces
• Myofibroblasts generate & maintain steady
contractile force shortening of connective
tissue fibers & wound closure
• 2nd week: Connective tissue scar

21. Abnormalities in wound repair
• Hypertrophic scar
• keloid
• Palmar fibromatosis
( Dupuytren’s disease)

22. 2. UNDIFFERENTIATED MESENCHYMAL
CELLS
(MESENCHYMAL STEM CELLS)
• Seen in Embryonic connective tissue
• Various elements of mature connective tissue
are derived from mesenchymal stem cells

23. • As more specialised cells are formed they lose
their ability to transform into other types.
Eg: fibroblasts

24. 3. ADIPOCYTES
(Lipocytes/ Fat cells)
• Differentiated from mesenchymal stem cells
• Central large fat globule(unilocular): Glycerol
esters of oleic, palmitic & stearic acids
• Store neutral fat, produce a variety of
hormones, inflammatory mediators & growth
factors
• Store chemical energy

25. H & E SUDAN III

26. FUNCTIONS:
• Control Energy balance & lipid homeostasis
• Endocrine role: Adipokine secretion
• Mobilization of fat is under nervous &
hormonal control
• No new adipose tissue is thought to form after
the immediate postnatal period

27. Brown fat:
• Multilocular adipose tissue
• Metabolize fatty acids & generate heat
• Uncouple cellular respiration via the
mitochondrial uncoupling protein (UCP1)
• PET scan: supraclavicular, in the neck & along
the spine
• Beige fat cell: Distinct type of thermogenic fat
cell, thought to be derived from precursor
cells in white fat

29. 4. PIGMENT CELLS
• Cells containing a brown pigment (usually
melanin) in their cytoplasm
• Sites:
→iris & choroid of eyeball
→epidermis of skin
• Cells of 2 types:
1. Melanocytes
2. Melanophores/ Chromatophores

30. MELANOCYTE
• Synthesize melanin
• Neural crest origin
MELANOPHORE/CHROMATOPHORE
• Engulf pigment released by
other cells
• Modified fibroblasts

31. • The fibroblasts & blood vessels within healing
wounds develop from mesenchymal stem cells
associated with the tunica adventitia of
venules

32. MIGRANT / WANDERING /
RELATED / FREE CELLS

33. MACROPHAGES
(TISSUE HISTIOCYTES/CLASMATOCYTES)
• Derived from monocytes & contain abundant
lysosomes
• Phagocytose Trypan blue, India ink & Lithium
carmine
• Lysosomes: Acid phosphatase activity
• L/M: evidence of phagocytic activity
• TEM: Surface exhibits numerous folds & finger
like projections

35. • Phagocytic, digestive & secretory functions
• Secretion: immune response, anaphylaxis &
inflammation
• Antigen presenting cells
MHC II interact with helper CD4 T
lymphocytes
• Arrive 24 hours after occurance of injury
• Mode of action: Phagocytosis & immune
response reactions

36. M1 Macrophages
(Classically activated macrophages)
• Promote inflammation, destruction of ECM &
apoptosis
• Elicit chronic inflammation & tissue injury
• Foreign body giant cells/ Langhans cells

37. M2 macrophages
(Alternatively activated macrophages)
• Activated by IL-4,5,10,13
• Anti- inflammatory, proliferative & angiogenic
• Resolution of inflammation & promote wound
repair
• Efficient at combating parasitic infections:
Schistosomiasis
• Involved in pathogenesis of allergy & asthma

38. Mononuclear phagocyte system
(MPS)
• Primarily derived from monocytes
• Phagocytose Trypan blue & India ink
• Cells become fixed in specific tissues & may
adopt a variety of morphologic appearances.
• Functions: phagocytosis, secretion of
lymphokines, antigen processing & antigen
presentation
• Exception: Microglia, Osteoclasts & Fibroblasts

39. MAST CELLS
• Develop in bone marrow & differentiate in
connective tissue
• 20-30µm in diameter
• Gluteraldehyde fixation toluidine blue 
Metachromatic staining of granules (heparin)
• The mast cell is related to the basophil that it
contain similar granules
• Cell surface: high affinity Fc receptors (Fc£RI)

40. • Granule components:
• Heparin, histamine, tryptase, superoxide
dismutase, aryl sulphatase, β-hexosaminidase
& chymase

41. METACHROMASIA
• When components of a cell or tissue stain in a
colour different from that of the dye used, the
staining is said to be metachromatic.

42. MAST CELLS
MCTC MAST CELLS/ CONNECTIVE
TISSUE MAST CELLS
MCT MAST CELLS/
MUCOSAL MAST CELLS
 TRYPTASE & CHYMASE TRYPTASE
 SKIN
INTESTINAL SUBMUCOSA
BREAST
AXILLARY LYMPH NODES
GRANULES: LATTICE-LIKE GRANULES: SCROLL LIKE
LUNGS
INTESTINAL MUCOSA

43. MCTC MAST CELLS
• In the vicinity of small blood vessels, hair
follicles, sebaceous glands & sweat glands & in
the capsules of organs
• Exception: central nervous system
• Exception: Spleen

44. BASOPHILS
• Develop & differentiate in bone marrow
• Share many features with mast cells:
basophilic secretory granules, similar
mediators & high affinity Fc receptors
• Don’t produce PGD2 & IL-5

45. LYMPHOCYTES
•Principally involved in
immune responses
•Thin rim of cytoplasm
& heterochromatic
nucleus

46. PLASMA CELLS
• Antibody producing cells derived from B
lymphocytes
• Prominent consituent in loose connective
tissue: GI & respiratory tracts
• short life span: 10-30 days
• H&E: cartwheel / analog clock face

49. •Produce large amounts
of only one type of
protein- a specific
antibody
•Produced antibodies are
discharged locally or
stored within the cell
•Antibodies stored within
the cell form inclusons
called Russell’s bodies

50. OTHER LEUKOCYTES
MONOCYTE NEUTROPHIL
EOSINOPHIL

51. CONNECTIVE TISSUE FIBERS

52. CONNECTIVE TISSUE FIBERS
• The most conspicuous components of
connective tissue are the fibers within it
• They provide strength & support to the
connective tissue
• 3 types:
Collagen
 Reticular
 Elastic

53. 1. COLLAGEN FIBERS
• Most abundant structural components of the
connective tissue
• 28 different types
• Seen in bundles
• Bundles may be straight or wavy
• Bundles often branch or anastomose with
adjacent bundles

54. PHYSICAL PROPERTIES
• Flexible & have high tensile
strength
• Pliable & can bend easily
• Birefringence
• Swell & become soft when
treated with weak acid/ alkali
• On boiling converted to
gelatin

55. COLLAGEN FIBRILS
• 8-12nm diameter
• Osmium staining:
65nm- banding pattern
• Collagen molecule/
Tropocollagen is the
subunit
AFM

56. Collagen molecule/ Tropocollagen
• 300nm long & 1.5nm thick
• Head to tail alignment in overlapping rows
• Covalent bonds between the collagen
molecules of adjacent rows gives tensile
strength
• Triple helix of 3 intertwined polypeptides
known as α chains

57. α chains
• Vary in size from 600-3000 aminoacids
• 42 types of α chains
• Encoded by different genes
• 29 types of collagen: Roman numerals I – XXIX
• Collagen molecule can be Homotrimeric /
Heterotrimeric

58. TYPE IV COLLAGEN
TYPE IV COLLAGEN
• Short filaments that form
sheets
• seen in basal lamina,
kidney glomeruli & lens
capsule
• Collagenopathy: Alport’s
syndrome

59. RETICULAR FIBERS
• Supporting framework-
liver, kidneys, bone marrow,
spleen & other lymphoid
organs
• Consist of collagen fibrils-
type III
• 65nm banding pattern
• 20nm diameter
• Exhibit branching pattern
• Do not form bundles

60. Staining properties
• H & E
• Periodic acid- Schiff
reaction(PAS)
• Silver staining procedures:
Gomori & Wilder
methods Argyrophilic

61. ELASTIC FIBERS
• Run singly, branch &
anastomose with each other
• Thinner than collagen
• But thick bunbles in
ligamentum flava &
ligamentum nuchae
• Interwoven with collagen
fibers

62. Staining properties
• H & E
• Orecin / Resorcin-fuchsin
• Aldehyde fuchsin
• Verhoeff’s method

63. • Produced by: fibroblasts, smooth muscle
cells,…
• Elastic property is related to its unusual
polypeptide backbone, which causes random
coiling
• Composed of
Central core of elastin
Fibrillin microfibrils

64. ELASTIN
• 70KDa
• Hydrophobic
• Desmosine &
Isodesmosine
• Encoded by one of the
largest genes:
28kilobases, less than
10% encodes elastin

65. THANK YOU