1. Connective Tissue
Dr. Ashraf Hussain

4. Connective Tissue
These tissues connect and support other tissues of the body

5. Connective Tissue Mechanical support
Medium for exchange of nutrients & waste products
Energy store and thermal insulation
Defensive functions
a) Barrier b) Engulf bacteria
c) Antibodies

7. Connective tissue
Connective tissue comprises a diverse group of cells embedded in a tissue-specific extracellular matrix
Different type of connective tissue are responsible for a variety of functions
Classification of connective tissue is based on the composition and organization of its cellular & extracellular components and on its functions

9. Structure of connective tissue
Cells
Intercellular substance or matrix

10. Matrix Amorphous ground substance
Thread like formed elements called fibers (collagen fibers, reticular fibers, elastic fibers)
Tissue fluid

11. Cellular component
interspersed in intercellular substance
different kinds of cells
Fibers – part of the “formed substance” of C.T.
embedded in ground substance
Matrix = ground substance + fibers

12. Connective tissue cells
Resident cell population
Fibroblasts
Macrophages
Adipose cells
Mast cells
Undifferentiated mesenchymal cells
Wondering cell population
Lymphocytes
Plasma cells
Neutrophils
Eosinophils
Basophils
Monocytes

13. Leucocytes in loose supporting tissue F-Fibroblasts, Er-Erythrocytes, N-Neurtrophils, Eo-Eosinophils, L-lymphocytes, P-Plasma cells, M-Macrophages

14. Connective tissue cells
Fibroblasts
Histiocytes (Macrophages)
Plasma cells
Mast cells
Fat cells

17. ADULT CONNECTIVE TISSUE COMPONENTS Connective Tissue Cells

18. Connective tissue cells
Fibroblasts
Most abundant
Appearance varies in relation to functional state
Produce connective tissue fibers & secrete ground substance

19. Mature Fibroblasts

20. Active fibroblasts

21. Histiocytes (Macrophages)
Abundant
Inactive and active histiocytes
Scavenger cells
Foreign body giant cells
Antigen presenting cells

22. Macrophage

23. Plasma cells
Generally rare but numerous at certain sites e.g., intestinal mucosa, lymphoid organs
Nucleus—cart wheel appearance
Production of antibodies

25. Mast cells Mast– well fed (German)
Abundant in loose connective tissue around blood vessels
Secrete Heparin ( anticoagulant)
& Histamine (vasodilator)

26. Mast Cells

27. Fat cells (adipocytes)
Form adipose tissue when accumulate together
Signet ring appearance

29. Blue dotted lines - Adipocytes
Orange Arrows - Fat droplet "space"
Green Arrow - Nuclei of Adipocyte

30. Connective tissue fibers
Long slender protein polymers which are found in differing proportions in various types of connective tissue
Predominant fiber type is responsible for conferring specific properties to the tissue

31. Connective tissue fibers
Collagen fibers --collagen
Reticular fibers --collagen
Elastic fiber elastin

32. Collagen Long molecule—tropocollagen
Three polypeptide chains intertwined together— triple helix
By now 19 varieties of collagen have been identified
Most important & best studied are I,II, III, IV &V.

33. Growth of molecular character of a collagen fibril

34. Collegen fibers are most abundant type of connective tissue fibers
Collagen fiber formation involves events that occur both within and outside the fibroblast

35. Collagen fibers Diameter (2-10 micrometer)
Run randomly in various directions
In many parts, collagen fibers lie parallel to each other forming bundles of various sizes
Flexible but inelastic (non-extensible)
Pink colour with H&E stain

36. Blue arrow - Collagen Bundle Green Arrow - Fibroblast nuclei

37. Reticular fibers
Reticular fibers provide a supporting framework for the cellular constituents of various tissues and organs
Reticular fibers are named for their arrangement in a mesh-like pattern or network

38. Reticular fibers Very thin branching fibers (rete—net)
Diameter (0.5 to 2 micrometer)
Coating of proteoglycans & glycoproteins– black colour with silver staining, red with PAS
Abundant in connective tissue around muscle fibers, nerve fibers, acini of glands, lymphoid organs & bone marrow

41. Elastic fibers
Highly elastic can stretch one and half time their original length
Diameter (0.2 to 1.0 mic.m)
Branch & rejoin to form loose network
Found in lungs, large arteries, ligamenta flava (connecting laminae of successive vertebrae)

44. Elastin fibres

45. Ground substance
Ground substace occupies the space between the cells and fibers
Ground substance consists largely of proteoglycans and hyaluronic acid
Proteoglycans and Glycosaminoglycans (GAG) are responsible for the physical properties of ground substance

46. Embryonic connective tissue
Develops from mesoderm & is known as Mesenchyme
Composed of star-shaped cells which lie in an abundant relatively homogeneous intercellular substance
Mucous tissue– Wharton’s jelly

47. Arrows = cells in mitosis; “C” = small blood vessels; Ground substance devoid of fibers; Cell processes extend into homogeneous ground substance

50. Disorders of connective tissue
Marfan syndrome - a genetic disease causing abnormal fibrillin
Scurvy - dietary deficiency in Vit.C leading to abnormal collagen.
Ehlers-danlos syndrome - a genetic disease causing progressive deterioration of collagens affecting different sites in the body such as joints, heart valves & arterial walls

51. Disorders of connective tissue
Osteogenesis imperfecta ( brittle bone disease) – insufficient production of good quality collagen to produce healthy, strong bones
Spontaneous pneumothorax – collapsed lungs, believed to be related to subtle abnormalities in connective tissue