1. C ONNECTIVE T ISSUE C HAPTER 3

2. C ONNECTIVE T ISSUE Connective Tissue – Connect body parts. It is found everywhere in the body. It is the most abundant and wide distributed of the tissue types.

3. C OMMON C HARACTERISTICS OF C ONNECTIVE T ISSUE 1. Variation of blood supply – Most connective tissues are well vascularized, but there are exceptions. – Tendons and ligaments have poor blood supply and cartilages are avascular. Therefore, these structures heal very slowly. 2. Extracellular matrix – Connective tissues are made up of many different types of cells plus varying amounts of a nonliving substance found outside the cells, called the extracellular matrix.

4. E XTRACELLULAR M ATRIX The extracellular matrix has two main elements: 1. A structureless ground substance 2. Fibers

5. G ROUND S UBSTANCE OF THE E XTRACELLULAR M ATRIX Composed of: 1. Mostly water 2. Some adhesion proteins Serve as glue that allows the cells to attach themselves to the matrix fibers embedded in the matrix. 3. Large, charged polysaccharide molecules. Trap water as they intertwine. As the abundance of these polysaccharide molecules increases, they cause the matrix to vary from fluid to gel-like to firm to rock-hard.

6. F IBERS OF THE E XTRACELLULAR M ATRIX Various types and amounts of fibers are deposited in the matrix depending on the connective tissue type and include: 1. Collagen fibers (white) 2. Elastic fibers (yellow) 3. Reticular fibers (fine collagen)

7. C ONNECTIVE T ISSUE V ARIATION All connective tissue consists of living cells surrounded by a matrix. Their major differences reflect fiber type and the number of fibers in the matrix. At one extreme, fat tissue is composed mostly of cells, and the matrix is soft. At the opposite extreme, bone and cartilage have very few cells and large amounts of hard matrix, which makes them extremely strong.

8. C ONNECTIVE T ISSUE F UNCTIONS 1. Protecting 2. Supporting 3. Binding together other body tissues 4. Serve as a water reservoir (less known function) Ground substance has the ability to absorb large amounts of water.

9. T YPES OF C ONNECTIVE T ISSUE 1. Bone 2. Cartilage 3. Dense Connective Tissue 4. Loose Connective Tissue 5. Blood

10. B ONE Bone – Composed of bone cells sitting in cavities called lacunae and surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers. Also called osseous tissue. Because of its rocklike hardness, bone has an exceptional ability to protect and support other body organs.

11. C ARTILAGE Less hard and more flexible than bone. It is found only in a few places in the body.

12. T HREE T YPES OF C ARTILAGE : 1. Hyaline Cartilage – Has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance. – Forms the supporting structures of the larynx (voice box), attaches the ribs to the breastbone, and covers the ends of bones where they form joints. – The skeleton of a fetus is made of hyaline cartilage, but by the time the baby is born most of that cartilage has been replaced by bone. – Most abundant and widespread in the body.

13. T HREE T YPES OF C ARTILAGE 2. Fibrocartilage – Highly compressible Forms the cushionlike disks between the vertebrae of the spinal column. 3. Elastic Cartilage – Very elastic Found where structure with elasticity is desired such as the external ear.

14. D ENSE C ONNECTIVE T ISSUE Has collagen fibers as its main matrix element. Crowded between the collagen fibers are rows of fibroblasts that manufacture the fibers. Also called dense fibrous tissue. Forms strong, ropelike structures. Examples: 1. Tendons: Attach skeletal muscles to bones. 2. Ligaments: Connect bones to bones. More stretchy and contain more elastic fibers than tendons. 3. Also makes up the lower layers of the skin (dermis) where it is arranged in sheets.

15. D ENSE REGULAR VS IRREGULAR

16. L OOSE C ONNECTIVE T ISSUE Softer and have more cells and fewer fibers than any other connective tissue type except blood. 3 types: 1. Areolar Tissue 2. Adipose Tissue 3. Reticular Tissue

17. A REOLAR T ISSUE Areolar Tissue – Soft, pliable “cobwebby” tissue that cushions and protects the body organs it wraps. Most widely distributed connective tissue variety in the body. Functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper position.

18. A REOLAR T ISSUE Because of its loose and fluid nature, areolar connective tissue provides a reservoir of water and salts for the surrounding tissues. – All body cells obtain their nutrients from areolar CT and release their wastes into this “tissue fluid.” – When a body region is inflamed, the areolar tissue in the area soaks up the excess fluid like a sponge and the area swells and becomes puffy, a condition known as edema. Many phagocytes wander through this area scavenging for bacteria, dead cells, and other debris, which they destroy.

19. A DIPOSE T ISSUE Adipose Tissue – Commonly called fat; areolar tissue in which fat cells predominate. – A droplet of stored oil occupies most of the fat cell’s volume and compresses the nucleus, displacing it to one side.

20. A DIPOSE T ISSUE Functions: 1. Adipose tissue forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from extremes of both heat and cold. 2. Protects some organs individually. Fat cushions the kidneys and eyeball sockets. 3. Fat deposits in the body (hips and breasts), where fat is stored and available for fuel if needed.

21. R ETICULAR C ONNECTIVE T ISSUE Reticular Connective Tissue Type of loose irregular connective tissue. Has a network of reticular fibers. Reticular fibers are synthesized by fibroblasts called reticular cells. Forms a soft skeleton or internal supporting framework (stroma) to support the lymphocytes in lymphoid organs (lymph nodes, red bone marrow, and spleen).

22. B LOOD Blood – Vascular tissue Consists of blood cells, surrounded by a nonliving, fluid matrix called blood plasma. The fibers of blood are soluble protein molecules that become visible only during blood clotting. Blood is quite atypical as connective tissues go. Blood is the transport vehicle for the cardiovascular system. Carries nutrients, wastes, respiratory gases, and many other substances throughout the body.