Connective Tissues

1. Connective Tissues

2. Connective Tissue • Found everywhere in the body • Most abundant and widely distributed of the primary tissues Major functions: • Binding and support (bone and cartilage) • Protection (bone and cartilage) • Insulation (fat) • Transportation of substances (blood)

3. 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)

4. Connective Tissue Prosper • Sub-divisions: 1. Loose connective tissues (areolar, adipose, and reticular) 2. Dense connective tissues (dense regular, dense irregular, and elastic) *Except for blood, all mature connective tissues belong to this class

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

6. Connective Tissue Proper: Loose Figure 4.8b

7. Connective Tissue Proper: Loose • 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 Adipose connective tissue (“white fat”)

8. Connective Tissue Proper: Loose Figure 4.8c

9. 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

10. Connective Tissue Proper: Loose Figure 4.8d

11. 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

12. Connective Tissue Proper: Dense Regular Figure 4.8e

13. Connective Tissue Proper: Dense • 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)

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

15. 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

16. 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

17. 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

18. Connective Tissue: Hyaline Cartilage Figure 4.8g

19. 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)

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

21. Connective Tissue: Cartilage Fibrocartilage: • 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)

22. Connective Tissue: Fibrocartilage • 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 Figure 4.8i

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

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

26. Connective Tissue: Blood Blood or vascular tissue: • 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)

27. Connective Tissue: Blood Figure 4.8k

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

29. Nervous Tissue Figure 4.10