Connective Tissue

1. Connective Tissue MamounKremli Al-Maarefa College

2. Objectives • What is connective tissue • Types of connective tissues • Functions of connective tissues • Relation of structure and function

3. Tissues • Four fundamental tissues are recognized: • Epithelial tissue • Connective tissue • Muscular tissue • Nervous tissue

4. Connective Tissue • Consists of two basic elements: • Cells, and • Extra-cellular matrix (abundant) (dominant part) • Fibers, and • Ground substance • liquid, gel, or solid • Function • Binds and/or supports other tissue

5. Connective Tissue • Connective tissue is clearly different from neighboring tissues

6. Connective Tissue • Connective tissue is clearly different from neighboring tissues

7. Connective Tissue • Connective tissue is clearly different from neighboring tissues

8. Connective Tissue Cells • Fibroblasts: • Secrete both fibers and ground substance of the matrix (wandering)

9. Connective Tissue Cells • Macrophages: • Phagocytes that develop from Monocytes (wandering or fixed)

10. Connective Tissue Cells • Plasma Cells: • Antibody secreting cells that develop from B-Lymphocytes (wandering)

11. Connective Tissue Cells • Mast Cells • Produce histamine that help dilate small blood vessels in reaction to injury (wandering)

12. Connective Tissue Cells • Adipocytes: • Fat cells that store triglycerides, support, protect and insulate (fixed)

13. Connective Tissue Cells

14. Fibroblasts • Active fibroblasts have extensions Extensions of fibroblasts (arrow-heads) are seen with the cell or alone, depending on section plane

15. Fibroblasts • Active fibroblasts have extensions Electrom micrograph of fibrocyte with cytoplasmic extensions interdigitating among collagen fibers, X 26,000

16. Matrix Fibers • Collagen Fibers • Elastic Fibers • Reticular Fibers

17. Matrix Fibers • Collagen Fibers: • Large fibers made of the protein collagen • The most abundant fibers • Promote tissue flexibility

18. Matrix Fibers • Elastic Fibers: • Intermediate fibers made of the protein Elastin • Branching fibers that allow for stretch and recoil picrosirius-stained collagen, elastic fibers are stained by Orcein Polarizing microscopy

19. Matrix Fibers • Reticular Fibers: • Small delicate, branched fibers • Have same chemical composition of Collagen • Forms structural framework for organs such as spleen and lymph nodes.

20. Matrix Fibers Collagen Elastin

21. Elastic and Collagen Fibers

22. Matrix Ground Substance • Hyaluronic Acid: • Complex combination of polysaccharides and proteins found in “true” or proper connective tissue • Chondroitin sulfate: • Jellylike ground substance of cartilage, bone, skin and blood vessels • Other ground Substances: • Dermatin sulfate, keratin sulfate, and adhesion proteins

23. Types of Connective Tissue • True (Proper) Connective Tissue • Loose Connective Tissue • Aereolar, Adipose, Reticular • Dense Connective Tissue • Supportive Connective Tissue • Cartilage • Bone • Liquid Connective Tissue • Blood

24. Loose Connective Tissue • Areolar tissue • Widely distributed under epithelia • Adipose tissue • Hypodermis, within abdomen, breasts • Reticular connective tissue • Lymphoid organs such as lymph nodes

25. Areolar Connective Tissue • Structure: • all 3 types of fibers • several types of cells • semi-fluid ground substance • Present in: • subcutaneous layer • mucous membranes • around blood vessels, nerves and organs • Function: • strength, support and elasticity

26. Adipose Connective Tissue: • Structure: • adipocytes; "signet ring" appearing fat cells. They store energy in the form of triglycerides (lipids) • Present in: • subcutaneous layer • around organs • yellow marrow of long bones • Function: • supports, protects and insulates • serves as an energy reserve

27. Adipose Connective Tissue

28. Reticular Connective Tissue • Structure: • fine interlacing reticular fibers • reticular cells • Present in: • liver, spleen and lymph nodes • Function: • forms the framework (stroma) of organs • binds together smooth muscle tissue cells

29. Reticular Connective Tissue • Structure: • fine interlacing reticular fibers • reticular cells • Present in: • liver, spleen and lymph nodes • Function: • forms the framework (stroma) of organs • binds together smooth muscle tissue cells

30. Reticular Connective Tissue

31. Reticular Connective Tissue Reticular Fibers Collagen Fibers Thyroid gland, Scanning electron microscopy, X 2500 Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy

32. Types of Connective Tissue • True (Proper) Connective Tissue • Loose Connective Tissue • Aereolar, Adipose, Reticular • Dense Connective Tissue • Supportive Connective Tissue • Cartilage • Bone • Liquid Connective Tissue • Blood

33. Dense Connective Tissue • Contains more numerous and thicker fibers and far fewer cells than loose CT • Types: • Dense regular connective tissue • Tendons and ligaments • Dense irregular connective tissue • Dermis of skin, submucosa of digestive tract

34. Dense Regular Connective Tissue • Structure: • bundles of collagen fibers and fibroblasts • Present in: • Tendons, • Ligaments • aponeuroses • Function: • provides strong attachment between various structures Tendon

35. Dense Regular Connective Tissue

36. Dense Irregular Connective Tissue • Structure: • randomly-arranged collagen fibers and • few fibroblasts • Present in: • fasciae, • dermis of skin • joint capsules • heart valves • Function: • provides strength

37. Dense Irregular Connective Tissue • Structure: • randomly-arranged collagen fibers and • few fibroblasts • Present in: • fasciae, • dermis of skin • joint capsules • heart valves • Function: • provides strength Eyelid, Azan stain Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy

38. Dense Irregular Connective Tissue • Structure: • randomly-arranged collagen fibers and • few fibroblasts • Present in: • fasciae, • dermis of skin • joint capsules • heart valves • Function: • provides strength Renal capsule, Scanning electron microscopy, X 5000 Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy

39. Types of Connective Tissue • True (Proper) Connective Tissue • Loose Connective Tissue • Aereolar, Adipose, Reticular • Dense Connective Tissue • Supportive Connective Tissue • Cartilage • Bone • Liquid Connective Tissue • Blood

40. Cartilage • Structure: • Jelly-like matrix (chondroitin sulfate) • collagen and elastic fibers • Chondrocytes (within spaces in the matrix called lacunae) • surrounded by a membrane (perichondrium) • has NO blood vessels or nerves except in the perichondrium • Function: • Collagen fibers provide strength • chondroitin sulfate provides resilience Hayaline Cartilage Perichondrium Perichondrium

41. Cartilage • Types: • Hyaline cartilage • Fibro-cartilage • Elastic cartilage

42. Hyaline Cartilage • Most abundant type • Structure: • Fine collagen fibers embedded in a gel-type matrix • Occasional chondrocytes inside lacunae • Present in: • embryonic skeleton • at the ends of long bones (joints) • in the nose and in respiratory structures • Function: • flexible, provides support • allows movement at joints

43. Hyaline Cartilage

44. Hyaline Cartilage • Covers articular surfaces

45. Fibrocartilage • Structure • bundles of collagen in the matrix that are usually more visible under microscopy • Present in: • Intervertebral discs, • Menisci of the knee, • Pubic Symphysis, • Tendon insertion on apophysealhayaline cartilage • Function: • Support and fusion • shock absorption

46. Fibrocartilage

47. Fibrocartilage Picrosirius-Hematoxilin stain of fibrocartilage, with abundant collagen fibers

48. Elastic Cartilage • Structure • Threadlike network of elastic fibers within the matrix • Present in: • external ear • auditory tubes • epiglottis • Function: • gives support, • maintains shape • allows flexibility

49. Elastic Cartilage Resorcin stain selectively staining the elastic fibers of elastic cartilage tissue Cells are not stained

50. Elastic Cartilage 1 Elastic fibers, 2 Cartilage Cells, 3 perichondrium Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy