2. Connective Tissue Components Dr. Jack L. Haar
I. Introduction
A. Distribution and role
B. Embryonic origin
1. Mesoderm
2. Neural crest

3. B. Embryonic origin
1. Mesoderm
2. Neural crest

4. II. Components of C.T. : Ground Sub., Fibers, Cells
A. Ground substance
1. Functions
Gel-like matrix in which cells and fibers are embedded
Medium for passage of molecules and cells
Contains adhesive proteins for cell movement

5. 2. Components of ground substance
Glycosamineoglycans (GAGs)
Long,unbranched polysaccharides of disaccharide units
Negative charge results in hydration of molecules
Proteoglycans: GAGs attached to proteins Proteoglycan aggregate: many proteoglycans attached to hyaluronic acid….. which is a GAG.

6. 3. Structrual glycoproteins
Fibronectin and laminin

7. Tissue fluid – a filtrate of blood similar to plasma

8. B. Fibers:
1. Collagen
Tropocollage – basic collagen molecule is made of three alpha subunits in a triple helix. Subunits determine collagen type
Produced by fibroblasts and other matrix forming cells
Tropocollage is secreted by cells and assembled extracellularly

10. Types of Collagen
Collagen type I: found in dermis of skin, bone, tendon, dentin, fascia, sclera, organ capsules, fibrous cartilage;
Collagen type II: very thin fibrins found in hyaline and elastic cartilage;
Collagen type III: the major component of reticular fiber;
Collagen type IV: does not form fibrils or fibers; found in the basal lamina underlying epithelial cells.

11. 2. Elastic fibers Produced by fibroblasts or smooth muscle cells
Amorphous core of elastin in a sheath of microfibrils
Elastin has unique properties that give it elasticity
Found with collagen fibers in all loose c.t.
May form branching sheets with fenestrations

12. 3. Reticular fibers:
Collagen type III, non-banded, thin with an amorphous coating
Not visible with H&E staining; argyrophilic
Abundant in smooth muscle, endoneurium and framework of lymphoid organs and bone marrow
Prominent during embryogenesis, inflammatory process, wound healing.

13. 3. Reticular fibers

14. C. Connective Tissue Cells. Some are long term residents
C. Connective Tissue Cells Some are long term residents Others are motile and migrate from blood into the c.t Fibroblasts a. Active fibroblast
Nucleus is oval or spindle-shaped, very euchromatic, nucleoli
Cytoplasm not discernible at L/M level
E/M reveals abundant rER, and prominent Golgi
Function to produce and secrete c.t. fibers and ground substance

15. C. Connective Tissue Cells 1. Fibroblasts b. Inactive fibroblast
Nucleus very spindle-shaped, very heterochromatic
Cytoplasm not apparent with L/M; very thin with E/M
Low metabolic rate

17. 2. Monocytes. a. Large, round cell, 12-20 μm in diameter. b
2. Monocytes a. Large, round cell, μm in diameter b. Precursors of macrophages c. Are found in connective tissue and peripheral blood

18. Macrophage Phagocytosis Lysosomes and phagosomes in cytoplasm

19. 4. Lymphocytes. a. 6 to 7 μm in diameter. b. T and B lymphocytes exist
4. Lymphocytes a. 6 to 7 μm in diameter b. T and B lymphocytes exist c. Plasma cells from B lymphocytes

20. 5. Plasma cells Produce antibody

21. Mast cells Granules contain GAGs, histamine, heparin Become activated in allergic reactions

22. 7. Neutrophils. Nucleus with 3-5 lobes
7. Neutrophils Nucleus with 3-5 lobes Two types of granules, one with enzymes, one with non-enzyme proteins

23. Neutrophils are highly phagocytic
Neutrophils are highly phagocytic Responsible for cardinal signs of inflammation
Dolar
Calor
Tumor
Rubor

24. Eosinophils Bi-lobed nucleus Distinct eosinophilic granules which are lysosomes Phagocytic and increase in number with parasitic infections

25. Eos – Greek Goddess of the dawn

26. Adipose tissue development

27. 9. Adipocyte – yellow Cells synthesize and store lipid for nutrition and insulation Nucleus and cytoplasm are displaced by large lipid droplet May appear as small clusters of cells or large accumulations

28. 9. Adipocyte- Brown. Multiple droplets of lipid (multilocular)
9. Adipocyte- Brown Multiple droplets of lipid (multilocular) Central nucleus Used in thermoregulation

29. Blood Cells 1. Erythrocytes. a. Biconcave, 7. 5 μm in diameter. b
Blood Cells 1. Erythrocytes a. Biconcave, 7.5 μm in diameter b. Filled with hemoglobin c. Actin-containing cytoskeleton d. No cellular organelles e – 7.0 x 106 per μL of peripheral blood

30. Leukocytes – 6,000 to 10,000 per μL of peripheral blood
Neutrophils : % of WBC’s
Eosinophils: 5% of WBC’s
Lymphocytes: 20-50% of WBC’s
Monocytes: 1-5% of WBC’s
Basophils: 0.5% of WBC’s

31. D. Blood cells. 2. Leukocytes. e. Basophils. Least common of WBC’s
D. Blood cells Leukocytes e. Basophils Least common of WBC’s Granules contain heparin and histamine

32. 3. Platelets a. 2-4 x 105 per μL peripheral blood
Non-nucleated, disk-like cell fragment
Promotes blood clotting
Formed by megakaryocytes in bone marrow

33. Clot formation Platelets aggregate to stop bleeding;
Fibrinogen from platelets reacts with factors from blood plasma;
Fibrin forms a network of fibers trapping blood cells to form a clot.

34. Hematopoiesis
Mesoblastic: Blood cells form from mesenchymal cells in yolk sac and body stalk; Third week of gestation in humans
Hepatic: Blood cells form in liver, thymus, spleen; 8 weeks gestation
Myeloid: Blood cells form in the bone marrow at 12 weeks gestation

35. Theory of hematopoiesis. Pluripotential hematopoietic stem cells. a
Theory of hematopoiesis Pluripotential hematopoietic stem cells a. Arise from a single type of stem cell b. Proliferate to form either lymphoid or myeloid multipotential cells

36. Production/Differentiation of blood elements – Terminology. a
Production/Differentiation of blood elements – Terminology a. Lymphopoiesis b. Erythropoiesis c. Thrombopoiesis d. Monopoiesis e. Granulopoiesis

37. http://www. path. uiowa. edu/virtualslidebox/ Table of Contents
Table of Contents Supporting tissue Tendon #25 Dense regular CT Inactive fibroblast Adipocytes Integument Axilla-skin #78 Loose (areolar) CT Dense irrecular CT

38. I. Connective tissue categories

39. Features for classifying connective tissue Number and types of cells Number and type of fibers/ground substance Arrangement of fibers

40. Connective Tissue Proper Loose or Areolar
Connective Tissue Proper Loose or Areolar Large number and variety of cells Mostly collagen but elastic and reticular fibers present Collegen fibers smaller than 7μm diameter Ground substance is gelatinous Surrounds muscles and supports epithelia

41. Lamina propria Loose connective tissue supporting epithelia

42. Dense Irregular C.T. Bundles measure at least 7μm in diameter Some elastic and reticular fibers present Predominance of fibers compared to cells and ground substance Dermis of skin is good example

43. C. Dense Irregular C. T.

44. Dense Regular C.T. Collagen bundles in parallel rows Few cell numbers and little variety Little vascularity Tendons and ligaments are examples

45. Connective tissue with special properties A. Elastic C. T
Connective tissue with special properties A. Elastic C.T. Elastic fibers predominate arranged in sheets Produced by fibroblasts and smooth muscle cells Form the walls of large arteries

46. B. Reticular C. T. Collagen type III is predominant fiber
B. Reticular C.T. Collagen type III is predominant fiber Reticular cell produces fiber and wraps around fiber Forms framework of blood cell forming organs

47. Adipose C. T. 1. White adipose C. T
Adipose C.T. 1. White adipose C.T. Adipocytes predominate, storing fat as triglycerides Collagen fiber septa form lobules Reticular fibers form supporting framework Distribution

49. Adipose C. T. 2. Brown adipose C. T. Few C. T
Adipose C.T Brown adipose C.T. Few C.T. septa and a rich blood supply Brown multilocular fat cells predominate Found in newborns

50. D. Mucous (Mucoid) C.T.

51. Mucous (Mucoid) C.T. Primitive fibroblasts Abundant ground substance, primarily hyaluronic acid Limited fibers Found in umbilical cord, called Wharton’s jelly.

52. E. Blood

53. http://www. path. uiowa. edu/virtualslidebox/ Table of Contents
Table of Contents Supporting tissue Tendon #25 Dense regular CT Inactive fibroblast Adipocytes Integument Axilla-skin #78 Loose (areolar) CT Dense irrecular CT

54. http://www. path. uiowa. edu/virtualslidebox/ Table of Contents
Table of Contents Supporting tissue Areolar connective tissue Fat (adipose tissue)

55. Digital Histology Site at VCU