2. Connective Tissue Found everywhere in the body; most abundant and widely distributed of the primary tissues The dense layer of the basement membrane of all epithelial tissues is created by connective tissue Connective tissue connects the epithelium to the rest of the body Vary widely in appearance and function, but they all share three basic components; specialized cells, fibers, and ground substance Never exposed to the outside environment

3. Functions of Connective Tissue  Establish a framework for the body  Transport fluids and materials  Protect organs  Support, surround, and interconnect other types of tissue  Store energy reserves  Defend the body from invading microorganisms

4. Structural Elements of Connective Tissue Ground substance – unstructured material that fills the space between cells and contains the fibers Fibers – provide support (collagen, elastic, or reticular) Cells – fibroblasts (connective tissue proper), chondroblasts (cartilage), osteoblasts (bone), hematopoietic stem cells (produces blood cells), and accessory cells (mast cells = cluster along blood vessels that detect foreign microorganisms; macrophages = “eat” foreign materials) Fibers and ground substance together constitute the matrix which surrounds the cells

5. Classification of Connective Tissues Classified on the basis of their physical properties Three general categories: 1.Connective tissue proper – includes tissues with many types of cells and fibers in a ground substance a.Loose connective tissues b.Dense connective tissues 2. Fluid connective tissues – blood and lymph 3. Supporting connective tissues – less diverse cell population and more densely packed fibers a.Cartilage b.Bone

6. Connective Tissue Prosper Sub-divisions: 1. Loose connective tissues (areolar, adipose, and reticular) 2. Dense connective tissues (dense regular, dense irregular, and elastic) *

7. Connective Tissue Proper: Loose Areolar connective tissue (little space) MMost widely distributed connective tissue SSupports and binds other tissues HHolds body fluids DDefends against infection SStores nutrients FFunctions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper positions.

8. Connective Tissue Proper: Loose Figure 4.8b

9. Connective Tissue Proper: Loose Adipose connective tissue (“white fat”) 90% of tissue’s mass is made of fat cells Cells are packed closely together Richly vascularized (high metabolic activity) Abundant (approx. 18% of an average person’s body weight) Acts as a shock absorber Provides insulation Stores energy Prevents heat loss from body

10. Connective Tissue Proper: Loose Figure 4.8c

11. Connective Tissue Proper: Loose Reticular connective tissue The only fibers in its matrix are reticular fibers (reticular cells are scattered along) Limited to certain sites Forms a stroma (internal framework) that supports many blood cells in lymph nodes, spleen, and bone marrow

12. Connective Tissue Proper: Loose Figure 4.8d

13. Connective Tissue Proper: Dense Dense Regular: Parallel collagen fibers with a few elastic fibers Provides great resistance to tension Attaches muscles to bone or to other muscles, and bone to bone Tendons – attach skeletal muscles to bone Ligaments – connect bones to bones at joints Aponeuroses – sheet like tendons; attach muscles to other muscles or bones

14. Connective Tissue Proper: Dense Regular Figure 4.8e

15. Dense Irregular: Irregularly arranged collagen fibers with some elastic fibers Forms sheets in body areas where tension is exerted from many different directions Found in the dermis (skin), digestive tract, fibrous joint capsules, and the fibrous coverings that surround some organs (kidneys, bones, cartilages, muscles, and nerves) Connective Tissue Proper: Dense

16. Connective Tissue Proper: Dense Irregular Figure 4.8f Connective Tissue Proper: Dense Irregular

17. Connective Tissue Proper: Dense Elastic: High proportion of elastic fibers Allows recoil of tissue following stretching, maintains blood flow through arteries and recoil of lungs following inspiration Found in walls of large arteries, walls of bronchial tubes and some ligaments of the vertebral column

18. Connective Tissue: Cartilage Stands up to both tension and compression Tough, but flexible Lacks nerve fibers Avascular Receives nutrients by diffusion from blood vessels located in the connective tissue membrane surrounding it

19. Connective Tissue: Cartilage Hyaline cartilage: – Made up of Collagen fibers Most abundant form of cartilage in the body Covers the ends of long bones (articular cartilage) Supports the tip of the nose, connects the ribs to the sternum, and supports most of the respiratory system passages Most of the embryonic skeleton is formed of hyaline cartilage before bone is formed

20. Connective Tissue: Hyaline Cartilage Figure 4.8g

21. Connective Tissue: Cartilage Elastic Cartilage: Similar to hyaline cartilage but with more elastic fibers Found where strength and “stretchability” are needed Forms the external ear and the epiglottis (flap that covers the opening to the respiratory passageway when we swallow)

22. Connective Tissue: Elastic Cartilage Figure 4.8h Similar to hyaline cartilage but with more elastic fibers Maintains shape and structure while allowing flexibility Supports external ear (pinna) and the epiglottis

23. Connective Tissue: Cartilage Structural intermediate between hyaline cartilage and dense regular connective tissues Compressible and resists tension well Found where strong support and the ability to withstand heavy pressure are required Intervertebral discs & spongy cartilage of the knee (menisci) Fibrocartilage:

24. Connective Tissue: Fibrocartilage Figure 4.8i Matrix similar to hyaline cartilage but less firm with thick collagen fibers Provides tensile strength and absorbs compression shock Found in intervertebral discs, the pubic symphysis, and in discs of the knee joint

25. Connective Tissue: Bone Supports and protects body structures Rocklike hardness Provide cavities for fat storage and synthesis of blood cells Well supplied by invading blood vessels Bone (Osseous Tissue):

26. Connective Tissue: Bone (Osseous Tissue) Figure 4.8j

27. Connective Tissue: Blood Fluid within blood vessels Most atypical connective tissue (does not connect things or give mechanical support) Functions as the transport vehicle for the cardiovascular system (carries nutrients, wastes, and respiratory gases) Blood or vascular tissue:

28. Connective Tissue: Blood Figure 4.8k

29. Connective Tissue: Nervous Tissue Main component of the nervous system (brain, spinal cord, and nerves) Regulates and controls body functions

30. Nervous Tissue Figure 4.10