Connective Tissue

1. Connective Tissue

2. Connective Tissue • Include tissues such as bone, fat, and blood. • Very different in appearance and function. • Found everywhere in the body, it is the most abundant and widely distributed of the tissue types. • Well vascularized (except tendons, ligaments, and cartilage) • All connective tissue have three basic components.

3. Three basic components • Specialized cells • Extracellular protein fibers • A fluid known as the ground substance • The extracellular fibers and ground substance constitute the matrix that surrounds the cell. The extracellular matrix typically accounts for most of the volume of connective tissue.

4. Funtions of Connective Tissue • Establishing a structural framework for the body. • Transporting fluids and dissolved materials throughout the body. • Protecting delicate organs. • Supporting, surrounding, and interconnecting other tissue types. • Storing energy reserves. • Defending the body from invading microorganisms.

5. Classification of Connective Tissue • Connective tissue proper • Fluid connective tissue • Supporting connective tissue

6. Connective Tissue Proper • Connective tissue with many types of cells and extracellular fibers in a syrupy ground substance. • Differ in number of cell types they contain and the relative properties and proportions of fibers and ground substance • Divided into two categories based on the relative number of fibers, cells, and ground substance. • Loose connective tissue • Dense connective tissue • Adipose tissue and tendons help comprise connective tissue proper.

8. Connective Tissue Proper: Cell Population • Fibroblasts – most abundant permanent resident, they are the only cell that are always present in every connective tissue proper. • Macrophages – engulf pathogens or damaged cells that enter the tissue. • Adipocytes • Mesenchymal Cells – stem cells that respond to local injury by producing daughter cells that become fibroblasts, macrophages or other type of connective tissue cell.

9. Melanocytes – synthesize and store the brown pigment melanin. • Mast Cells – small, mobile, found near blood cells and contain histamine and heparin which are released after injury or infection. • Lymphocytes – migrate throughout the body, may develop into plasma cells. • Microphages – phagocytic blood cells.

10. Connective Tissue Fibers • Collagen Fibers – long, straight, and unbranched. Most common fibers in connective tissue proper. Flexible and stronger than steel when pulled from either end. Tendons and ligaments are made of collagen fibers. • Reticular Fibers – thinner than collagen fibers and form a branching interwoven framework that is tough, flexible and can withstand forces applied from many different directions. • Elastic Fibers – contain the protein elastin, fibers are branched and wavy. After stretching they will return to their original length. Relatively rare but have important functions.

11. Loose Connective Tissue • Also known as areolar tissue. • Is the “Packing Material” of the body. • It fills space between organs, provides cushioning, supports epithelia, blood vessels and nerves, as well as providing a route for the diffusion of materials. • The least specialized connective tissue in the body, has an open framework, can distort without damage. • Two types of loose connective tissue.

12. Adipose Tissue • Adipose tissue provides padding, cushions shock, acts as an insulator, serves as packing or filler around structures. • Common under the skin of the groin, buttock, sides, and breasts. Fills in the bony sockets behind the eye, surrounds the kidney, and dominates extensive areas of loose connective tissue in the pericardial and abdominal cavities.

13. Reticular Tissue • Found in organs such as the spleen and liver. • Creates a three dimensional network, stroma, that supports the functional cells of these organs. • This fibrous framework is also found in lymph nodes and bone marrow.

14. Dense Connective Tissue • Often called collagenous tissues because collagen fibers are the dominant type. • Two types of dense connective tissue in the body: • Dense regular – collagenous fibers are arranged parallel to each other, packed tightly, and aligned with forces applied to the tissue. • Dense irregular – form an interwoven framework and do not show any consistent pattern. These tissues provide strength and support to areas open to stresses from many directions.

15. Fluid Connective Tissue • Distinctive population of cells. • Suspended in a watery matrix that contains dissolved proteins. • Two fluid connective tissues • Blood • Lymph

16. Blood • Contains blood cells and fragments known collectively as formed elements. • Red blood cells (erythrocyte) make up almost half the volume of blood. • Plasma, the watery ground substance, contains white blood cells and leukocytes. • Also contains platelets that function in the clotting response that seals breaks in the the endothelial lining.

17. Lymph • Forms as interstitial fluid and enters small passageways, lymphatics, that return it to the cardiovascular system. • Cells of the immune system monitor the composition of lymph and respond to signs of injury and infection. • 99% of the cells in lymph are lymphocytes (the rest are macr & microphages).

18. Supporting Connective Tissue • Less diverse cell population than connective tissue proper and a matrix that contains tightly packed fibers. • Two types of supporting connective tissue • Bone • Cartilage

19. Cartilage • The matrix of cartilage is gel like whose characteristics vary depending on the predominant fiber type. • Cartilage cells are known as chondrocytes and they are the only cells found in the matrix. • Avascular – all nutrient and waste product exchange must occur by diffusion through the matrix.

20. Cartilage grows by two mechanisms: • Interstitial growth • Appositional growth • Three major types of cartilage: • Hyaline Cartilage – most common type. • Elastic Cartilage – extremely resilient and flexible. • Fibrocartilage – little ground substance, dominated by collagen fibers.

21. Hyaline Cartilage • Location – between tips of ribs and bones of sternum; covering one surfaces at synovial joints; supporting larynx, trachea, and bronchi; forming part of nasal septum. • Functions – provides stiff but somewhat flexible support; reduces friction between bony surfaces.

22. Elastic Cartilage • Location – tip of nose; epiglottis. • Function – provides support but tolerates distortion without damage and returns to original shape.

23. Fibrocartilage • Location – pads within knee joints; between pubic bones of pelvis; intervertebral discs. • Function – resists compression; prevents bone-to-bone contact; limits relative movement.

24. Bone • The matrix of bone is said to be calcified because it contains mineral deposits, primarily calcium salts. This is what gives bone its rigidity. • Ground substance is very small. One third of the bone matrix is made of collagen fibers. • The minerals are organized around the collagen fibers resulting in a strong, flexible combination resistant to shattering. • Can compete with the best steel reinforced concrete.