1. The Connective Tissue
M. Soleimani , Ph.D

3. Connective tissue

4. Connective tissue functions:
Establishing a structural framework
Protecting delicate organs
Supporting, surrounding and interconnecting tissues
Transporting fluids and dissolved materials
Storing energy reserves
Defending the body from microorganisms

5. Connective Tissue Classification
Embryonic Connective Tissue
Connective Tissue Proper
Loose
Mesenchymal
Dense irregular
Dense
Dense regular
Mucous
Reticular
Adipose

6. A Classification of Connective Tissues

7. Connective Tissue Connective Tissue Composition
Fibers (collagen, elastic, reticular)
Cells (fibroblasts, immune, vascular)
Ground substance (glycosaminoglycans, proteoglycans, glycoproteins)

8. Connective tissues contain
Specialized cells
Matrix
Composed of extracellular protein fibers and a ground substance

9. CELLS OF AREOLAR LOOSE CONNECTIVE TISSUE
Resident Immigrant
Fibroblast Lymphocyte
Myofibroblast Neutrophil
*Adipose Cell Eosinophil
Plasma Cell Basophil
Mast Cell Monocyte
Macrophage
*not motile Red :derived from immigrant cells

10. Connective Tissue Cells
Fixed cells:
Mesenchymal cells
Fibroblasts
Macrophages
Mast cells
Adipose cells
Pericytes
Transient cells:
WBC of Blood
Plasma cells

11. FIBROBLAST
Derived from fibroblast mitosis and also from primitive mesenchymal precursor cell differentiation
Secretes collagen, all elastic fiber components,hyaluronic acid , proteoglycans etc. (i.e. most of the extracellular matrix)

12. ① fibroblast ---structure: LM:
large,flattened cell with processes- stellate in shaped
Large ovoid pale nucleus-contain more fine chromatin, with clear one-two nucleoli
Weakly basophilic cytoplasm-homogeneous

14. EM:
rich in RER,Golgi appatatus and free ribosome
---function: synthesize fibers and ground substance

15. Fibroblast

16. Fibroblast

17. Fibroblast

19. *fibrocyte: still state or inactive fibroblast
---structure:
spindle-shaped, small
N:small,dark stained
Acidophilic cytoplasma
EM: less organelles
---function: become into fibroblast for repairing

20. Macrophage, a long-lived defense cell
Derived from monocyte
Functions:
Phagocytosis
Pinocytosis
Bacterial killing
Viruses only sometimes killed by macrophage but usually they stimulate macrophage to secrete lymphocye activators (e.g. interferons) that result in viral destruction but macrophages can become viral reservoirs (e.g. HIV)
Antigen-presenting cell (i.e process & present to lymphocytes to stimulate lymphocyte function)

21. Macrophage Phagocytosis of cell debris and microorganisms
Presenting antigens to lymphocytes
RBC turnover in spleen
Two categories:
Resident and Elicited
Foreign body giant cells in response to excessively large materials form from many macrophages

22. ②macrophage ---structure: LM:
round or ovoid-irregular in shape when it have short blunt processes_pseudopodium
Small and dark nucleus
Acidophilic cytoplasm

24. EM: rich in a. lysosome b. Phagosome← phagocytosis and
pinosome ←pinocytosis
c.  Remnant
d.  Microfilament and microtubule

26. Macrophage
---function:
a.    Chemotaxis: chemotactic factor
b. phagocytosis:
Special phagocytosis: recognize Bacterium, virus and foreign cell
non special: carbon particles, dust and dead cells
*Phagosome(pinosome) + primary lysosome →secondary lysosome →remnants

27. c.  secretion: lysozyme, complement and interleukin-I (IL-1)and interferon(INF)
b.     antigen presenting function:
*capture antigen→processes→+ MHC II molecule (major histocompatibility complex molecules) →antigen-MHC II complexes→TLC

29. Micro Vacuum Cleaner!

30. Macrophage vs Ecoli

31. PLASMA CELLS
Not normally found in plasma
Derived from Type B lymphocytes that enter connective tissue
Synthesize and secrete by exocytosis specific antibodies (immunoglobulins) that bind to specific antigens (i.e. the molecules that provoked the plasma cell formation from B lymphocyte)
Antigen/antibody complex stimulate destruction of antigen (e.g. by stimulating phagocytosis or lysis of foreign cell source of that antigen)
Some plasma cells may be exception to definition of resident cell as being long-lived since some only live 2 weeks but evidently plasma cells can also live longer

32. Plasma Cell Differentiate from B - lymphocytes
Oval cell with basophilic cytoplasm, pale centrosome, clockface nucleus

33. plasma cell
---structure:
LM:
round or ovoid
Round eccentrically-located nucleus with more spot-liked heterochromatin
Basophilic cytoplasm

34. Plasma Cell

35. Plasma Cell
EM: rich in parallelly arranged RER, free ribosome and Golgi complex
---function: synthesize and secrete immunoglobulin, Ig-antibody

36. Plasma Cell

37. MAST CELLS
Secretory cells rich in large secrtory granules
Derived from bone marrow precursors
Synthesize and secrete by exocytosis a variety of substances stored in large secretory granules
Involved in inflammatory response
Secrete (in response to IgE)
Histamine (blood vessel permiablilty, smooth muscle
constriction); heparin; proteases; chemotactic factor for eosinophils.

38. Mast Cell

40. ④mast cell
---structure:
LM:
round and large cell
Small dark-stained nucleus
Basophilic secreting granules

41. Mast Cell

42. Basophilic secreting granules:
heparin:an anticoagulant
Histamine: cause cap. permeability↑, cap. leakage to form oedema and contraction of SM
Eosinophil chemotactic factor
Cytoplasm contain:
leukotriene- slow reaction
substance
---function: cause allergic
reaction

43. Mast Cell

44. ⑤fat cell
---structure:
large, round or polygonal
flattened ovoid nucleus located on one side of cell
thin layer of cytoplasm
a large lipid droplet
---function: synthesize and store fat

45. ⑥undifferentiated mesenchymal cell
---structure:similar to fibrocyto
---function:multidifferentiating potential
⑦leukocytes: neutrophil,acidophil and lymphocyte

47. Mesenchymal cell

48. The Extracellular Matrix
Structural Proteins
collagens
elastins
Cell Binding Proteins
Laminins
Fibronectins
Glycosaminoglycans (GAGs).
Hyaluronans
Chondroitin sulfates
Heparan sulfates (including heparin)
Keratan sulfates.
Proteoglycans.
GAGs bind to core proteins.
e.g. aggrecan in cartilage.

49. Fibers

50. Collagens 25% (by mass) of all protein in the body At least 25 types
19 (Types arranged in 7 broad classes:
Fibril-Forming Collagens w/ striated macrofibers: I, II, III, V, XI
Network-Forming Collagens: IV, VIII, X
Fibril-associated with interrupted triple helixes: IX, XII, XIV, XVI, XIX
Beaded Filament-Forming Collagen: VI
Collagen of Anchoring Fibrils: VII
Collagens with a Transmembrane Domain: XIII, XVII
Collagen Types XV and XVIII
At Least 33 Different Gene Products, arranged as Homo- or Hetero-trimers
Common structural elements:
collagen helix
Rich in (hydroxy)proline and (hydroxy)lysine
glycine at every 3rd residue
trimer in native structure

52. How is collagen made?
STEP 1: Synthesis of -chains of pre-procollagen on ribosomes and endoplasmic reticulum

53. How is collagen made?
STEP 2: Hydroxylation of proline residues to obtain hydroxyproline (an aminoacid unique to collagen).
a reaction that substitutes a hydroxyl group, OH, for a hydrogen atom, H, in the proline
the hydroxylation reaction secures the chains in the triple helix of collagen
hydroxylation is catalyzed by the enzyme prolyl-4-hydroxylase
Vitamin C is essential for enzyme action, scurvy! OH OH
Alpha-chain OH

54. How is collagen made?
STEP 3: Hydroxylation of lysine residues to obtain hydroxylysine
hydroxylysine is needed to permit the cross-linking of the triple helices into the fibers
the enzyme peptidyl proline hydroxylase is essential OH OH OH
Alpha-chain OH OH

55. How is collagen made?
STEP 4: Glycosylation of some hydroxlysine residues
glucose and galactose are added by enzymes galactosyl transferase and glycosyl transferase
may affect fibril size OH OH OH
Alpha-chain OH OH
Gal
Glu

56. How is collagen made?
STEP 5: Assembly of the three alpha chains to from procollagen
formation of disulphide bonds between parts of the polypeptide chains known as registration peptides at the C-terminal
three chains associate, align and the triple helix forms in a zipper-fashion giving procollagen
C-Terminal
N-Terminal s

57. Gly is crucial for forming collagen structure.

58. EXTRACELLULAR SPACE N-terminal protease
STEP 6: Secretion of procollagen molecules by exocytosis into the extra cellular space STEP 7: Cleavage of registration peptides in the extra cellular space, by procollagen peptidases. The resulting molecule is collagen (finally!)
EXTRACELLULAR SPACE
N-terminal protease

59. Assembly of collagen fibers begins in the ER and is completed outside the cell
Hydroxylation of Pro & Lys
glycoslyation of Lys
Cleavage of C and N terminal propeptides
makes collagen 1000x less soluble
=> Impt this occurs OUTSIDE of cell

60. The basic structural unit of collagen is a triple helix
Fibrils stabilized by novel Collagen and elastin
Pro/Lys X-links that are specific
for these proteins
Collagen fibrils form by lateral
interactions of triple helices

61. How is collagen made?
STEP 8: Self-assembly or polymerization of collagen molecules form collagen fibrils.
STEP 9: Cross-linkage between adjacent collagen molecules that stabilizes the fibrils.
= collagen molecule

62. Collagens form diverse structures
Types VI and IX are Fibril-Associated Collagens

63. Collagen Synthesis

65. ①collagenous fiber(white fiber)
LM:
1-20 um in diameter
Belt-liked wave and branch to form a network
Eosinophilic

66. EM: parallel-arranged fibrils
20-200nm in diameter
Have periodic cross striation at 64nm interval

67. Collagen
Fibroblast surrounded by collagen fibrils in the connective tissue of embryonic chick skin

69. ELASTIC FIBERS
Composed of:
Elastin
microfibrillar proteins (including fibrillin)
Components made by:
Fibroblasts
In blood vessels most by smooth muscle
In other tissues by cells of mesenchymal origin such as chondroblasts
Elastin precursor secreted:
Tropoelastin
Function:
Confers elasticity (allows recoil after stretching e.g.important in blood vessels)

71. ② elastic fiber (yellow fiber)
LM:
thinner and less, um
Slight red(HE), purple(aldehyde fuchsin) or brown(orcein)
Branch and form a network
EM:
core: elastin-low electron density
Peripheral: microfibril nm, electron dense ↑
fibrillin

74. ③reticular fiber LM: thin and less,0.2-1.0 um in diameter
Branch to form network
Argyrophilic fiber(silver impregnation method)
EM:
type III collagen
64nm cross striation
---distribution:
reticular tissue
connecting portion, e.g.reticular lamina

75. Extracellular matrix proteoglycans
Hyaluronan resists compression and facilitates cell migration

76. Cell-surface proteoglycans-The Syndecan Family of Single TM proteins

77. Many growth factors are sequestered and presented to cells by proteoglycans

78. ② glycoprotein: proteins
---fibronectin
cells←fibronectin→collagen ↓
proteoglycan
---laminin
---chondronectin
---function:
Connection
affect the differentiation and movement of cells

79. Structure of Laminin Trimer (~850 kD total MW)

80. ③ tissue fluid
tissue
artery → Tissue fluid → vein →blood steam
dehydration
oedema

82. Connective tissue proper
Classified as loose or dense
Loose
Embryonic mesenchyme, mucous connective tissues
Areolar tissue
Adipose tissue
Reticular tissue
Dense
Dense regular CT
Dense irregular CT

83. The Cells and Fibers of Connective Tissue Proper

84. Loose Connective Tissue— Areolar 400X
collagen
nuclei of cells
elastin
abundant ground substance

85. Connective Tissue in Embryos

86. Loose Connective Tissue— Mesenchyme 400X
nucleus of mesenchymal cell
vertebrate embryo

87. * Loose Connective Tissue— Mesenchyme 1000X
cells have irregular shapes
abundant ground substance
vertebrate embryo

88. Adipose and Reticular Tissues

89. Loose Connective Tissue— Adipose 100X
adipocytes

90. * Loose Connective Tissue— Adipose 400X
nucleus
cell membrane

91. Multilocular Adipose Tissue

92. Reticular Connective Tissue 400X
reticular fibers
spleen

93. * Reticular Connective Tissue 1000X
reticular fibers
spleen

94. Reticular Tissue (Collagen type III)

95. Dense Connective Tissues

96. fibroblast cell nuclei
Dense Regular Connective Tissue 400X
fibroblast cell nuclei
tendon with densely packed parallel collagen fibers

97. Dense Connective Tissues

98. Dense Irregular Connective Tissue 400X
non-parallel collagen fibers
dermis of skin (see slide 12)

99. Dense Connective Tissues

101. Membranes

102. Membranes are simple organs
Form a barrier
Composed of epithelium and connective tissue
Four types
Cutaneous
Synovial
Serous
Mucous

103. Membranes

104. Mucous membranes Line cavities that communicate with the exterior
Contain lamina propria

105. Serous membranes
Line sealed internal cavities
Form transudate

106. Cutaneous membrane
Covers the body surface
Synovial membrane
Incomplete lining within joint cavities

107. Tissue Injuries and Repairs
2 steps
Inflammation
Repair
Regeneration
Fibrosis