1. Emmanuel E.Siddig University of Khartoum- FMLS

2. TISSUES Tissue is group of cells working together for a specific function Types of tissue : 1. Epithelial Tissue 2. Connective Tissue 3. Muscle Tissue 4. Nervous Tissue

3. Objectives Describe the general features of connective tissues. Describe the structure, location, and function of the various types of connective tissues.

4. Connective tissues are one of the most abundant and widely distributed tissues in the body. Function: 1. They bind together 2. Support 3. strengthen other body tissues 4. protect and insulate internal organs 5. compartmentalize structures such as skeletal muscles 6. serve as the major transport system within the body (blood) 7. stored energy, reserves (adipose, or fat, tissue) 8. and are the main source of immune responses.

5. General Features of Connective Tissues Connective tissues consist of two basic elements: 1. extracellular matrix 2. Cellular elements

6. Extracellular matrix is the material located between its widely spaced cells. The extracellular matrix consists of protein fibers and ground substance the material between the cells and the fibers. The extracellular fibers are secreted by the connective tissue cells and account for many of the functional properties of the tissue in addition to controlling the surrounding watery environment via specific proteoglycan molecule

7. Connective Tissue Cells Fibroblasts : are large, flat cells with branching processes. They are present in all the general connective tissues, and usually are the most numerous. Fibroblasts migrate through the connective tissues, secreting the fibers and certain components of the ground substance of the extracellular matrix

9. Macrophages Develop from monocytes, a type of white blood cell. Macrophages have an irregular shape with short branching projections and are capable of engulfing bacteria and cellular debris by phagocytosis. Fixed macrophages reside in a particular tissue; examples include alveolar macrophages in the lungs or splenic macrophages in the spleen.

10. Plasma cells : are small cells that develop from a type of white blood cell called a B lymphocyte. Plasma cells secrete antibodies, proteins that attack or neutralize foreign substances in the body. Mast cells: are abundant alongside the blood vessels that supply connective tissue. They produce histamine, a chemical that dilates small blood vessels as part of the inflammatory response, the body’s reaction to injury or infection. In addition, researchers have recently discovered that mast cells can bind to, ingest, and kill bacteria.

11. Adipocytes also called fat cells or adipose cells, are connective tissue cells that store triglycerides (fats). They are found deep to the skin and around organs such as the heart and kidneys. White blood cell

13. Connective Tissue Extracellular Matrix Each type of connective tissue has unique properties, based on the specific extracellular materials between the cells. The extracellular matrix consists of two major components: (1) the ground substance and (2) the fibers.

14. Ground substances: is the component of a connective tissue between the cells and fibers. The ground substance may be fluid, semifluid, gelatinous, or calcified. It supports cells, binds them together, stores water, and provides a medium for exchange of substances between the blood and cells. It plays an active role in how tissues develop, migrate, proliferate, and change shape, and in how they carry out their metabolic functions. Assignment component of the ground substances??

15. Fibers Three types of fibers are embedded in the extracellular matrix between the cells: collagen fibers, elastic fibers, and reticular fibers. They function to strengthen and support connective. 1. Collagen fiber. 2. Reticular fiber. 3. Elastic fiber.

16. - Collagen fiber: are very strong and resist pulling forces (tension), allows tissue flexibility. The properties of different types of collagen fibers vary from tissue to tissue. Collagen fibers often occur in parallel bundles. The bundle arrangement adds great tensile strength to the tissue. Chemically: collagen fibers consist of the protein collagen, which is the most abundant protein in your body, representing about 25% of the total. Collagen fibers are found in most types of connective tissues, especially bone, cartilage, tendons (which attach muscle to bone), and ligaments (which attach bone to bone).

17. Collagen types „ Collagen type I - 90% of all collagen. Forms bone, tendons, skin. Made by fibroblasts, osteoblasts, odontoblasts. „ Collagen type II – found in cartilage. Made by chondroblasts. Forms fibrils, not fibers. „ Collagen type III – component of reticular fibers in lymphoid organs. „ Collagen type IV – made by endothelial and epithelial cells

20. Elastic fibers which are smaller in diameter than collagen fibers, branch and join together to form a fibrous network within a connective tissue. An elastic fiber consists of molecules of the protein elastin surrounded by a glycoprotein named fibrillin, which adds strength and stability. Because of their unique molecular structure, elastic fibers are strong but can be stretched up to 150% of their relaxed length without breaking. Equally important, elastic fibers have the ability to return to their original shape after being stretched, a property called elasticity. Elastic fibers are plentiful in skin, blood vessel walls, and lung tissue.

22. Reticular fibers consisting of collagen arranged in fine bundles with a coating of glycoprotein, provide support in the walls of blood vessels and form a network around the cells in some tissues, such as areolar connective tissue, adipose tissue, nerve fibers, and smooth muscle tissue. Produced by fibroblasts, reticular fibers are much thinner than collagen fibers and form branching networks. Like collagen fibers, reticular fibers provide support and strength.

24. Classification of Connective Tissues I. Embryonic connective tissues A. Mesenchyme B. Mucous connective tissue II. Mature connective tissues A. Loose connective tissues 1. Areolar connective tissue 2. Adipose tissue 3. Reticular connective tissue B. Dense connective tissues 1. Dense regular connective tissue 2. Dense irregular connective tissue 3. Elastic connective tissue

25. C. Cartilage 1. Hyaline cartilage 2. Fibrocartilage 3. Elastic cartilage D. Bone tissue E. Liquid connective tissue 1. Blood tissue 2. Lymph

26. Embryonic Connective Tissues A. MESENCHYME Description Irregularly shaped mesenchymal cells embedded in semifluid ground substance that contains delicate reticular fibers. Location Almost exclusively under skin and along developing bones of embryo; some in adult connective tissue, especially along blood vessels. Function Forms almost all other types of connective tissue.

28. B. MUCOUS CONNECTIVE TISSUE Description: Widely scattered fibroblasts embedded in viscous, jellylike ground substance that contains fine collagen fibers. Location: Umbilical cord of fetus. Function: Support.

30. Mature Connective Tissues: Loose Connective Tissues A. AREOLAR CONNECTIVE TISSUE Description: One of the most widely distributed connective tissues; consists of fibers (collagen, elastic, reticular) arranged randomly and several kinds of cells (fibroblasts, macrophages, plasma cells, adipocytes, mast cells, and a few white blood cells) embedded in semifluid ground substance Location: In and around nearly every body structure (thus, called “packing material” of the body): in subcutaneous layer deep to skin, nerves, and body organs. Function: Strength, elasticity, support.

32. B. ADIPOSE TISSUE Location: Wherever areolar connective tissue is located: subcutaneous layer deep to skin, around heart and kidneys, yellow bone marrow, padding around joints and behind eyeball in eye socket. Function Reduces heat loss through skin; serves as an energy reserve; supports and protects organs. In newborns, BAT generates heat to maintain proper body temperature.

34. C. RETICULAR CONNECTIVE TISSUE Description Fine interlacing network of reticular fibers (thin form of collagen fiber) and reticular cells. Location Stroma (supporting framework) of liver, spleen, lymph nodes; red bone marrow; reticular lamina of basement membrane; around blood vessels and muscles. Function Forms stroma of organs; binds smooth muscle tissue cells; filters and removes worn-out blood cells in spleen and microbes in lymph nodes.

36. D. DENSE REGULAR CONNECTIVE TISSUE Description Shiny white extracellular matrix; mainly collagen fibers regularly arranged in bundles with fibroblasts in rows between bundles. Location Forms tendons (attach muscle to bone), most ligaments (attach bone to bone or muscle to bone). Function Provides strong attachment between various structures. Tissue structure withstands pulling (tension) along long axis of fibers.

38. E. DENSE IRREGULAR CONNECTIVE TISSUE Description Collagen fibers; usually irregularly arranged with a few fibroblasts. Location Often occurs in sheets, such as fasciae (tissue beneath skin and around muscles and other organs), reticular (deeper) region of dermis of skin, kidneys, liver, testes, lymph nodes; also in heart valves. Function Provides tensile (pulling) strength in many directions.

40. F. ELASTIC CONNECTIVE TISSUE Description Predominantly elastic fibers with fibroblasts between fibers; unstained tissue is yellowish. Location Lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal cords, suspensory ligaments of penis, some ligaments between vertebrae. Function Allows stretching of various organs; is strong and can recoil to original shape after being stretched.

42. Cartilage A. HYALINE CARTILAGE Description Hyaline cartilage contains a resilient gel as ground substance and appears in the body as a bluish- white, shiny substance prominent chondrocytes are found in lacunae surrounded by perichondrium (exceptions: articular cartilage in joints and cartilage of epiphyseal plates, where bones lengthen during growth). Location Most abundant cartilage in body; at ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, embryonic and fetal skeleton. Function Provides smooth surfaces for movement at joints, flexibility, and support; weakest type of cartilage.

44. B. FIBROCARTILAGE Description Chondrocytes scattered among clearly visible thick bundles of collagen fibers within extracellular matrix; lacks perichondrium. Location Pubic symphysis (where hip bones join anteriorly), intervertebral discs. Function Support and joining structures together. Strength and rigidity make it the strongest type of cartilage.

46. C. ELASTIC CARTILAGE Description Chondrocytes in threadlike network of elastic fibers within extracellular matrix; perichondrium present. Location Lid on top of larynx (epiglottis), part of external ear (auricle). Function Provides strength and elasticity; maintains shape of certain structures.

48. Test Your Self

54. References: Books - Wheather’s Functional histology Fifth edition. - DiFiore's Atlas of Histology with Functional Correlations Online links: - Pathpedia.com

55. Thank you