Understanding Connective Tissue: Functions and Structures

1. Warm-Up What type of connective tissue is shown below? 1. 2. Adipose Tissue (Loose Connective Tissue) Cartilage 3. 4. Bone Blood

2. Chapter 4 Tissue: The Living Fabric

3. Part II: Connective Tissue

4. Connective Tissue • Most abundant and widely distributed tissue • Main classes: • Connective tissue proper (loose & dense) • Cartilage • Bone • Blood • Functions: • Binding and support • Protection • Insulation • Transport substances

5. General Features Not very cellular compared to the other types of tissue Does not occur on body surfaces Has a nerve supply, except cartilage Variations in blood supply Avascular (no blood) – cartilage Poorly vascular – tendons, ligaments Most others are vascular Connective Tissue

6. Two basic elements: cells and an extracellular matrix • Cells • -blasts : form the extracellular matrix • -cytes : maintain the extracellular matrix • -clasts : break down the extracellular matrix

7. Extracellular matrix • Produced by cells, secreted to exterior • Ground substance: “glue” - fills space between cells & fibers • water + adhesion proteins + polysaccharides • Fibers: provide support • Collagen - strength • Elastic – stretch • Reticular – fine network, “skeleton” of organs

8. Loose Connective Tissue Proper • Universal packing material • Subclasses: areolar, adipose, reticular • Structure: softer, fewer fibers, gel-like matrix • Functions: • Cushion & protect organs (areolar, adipose (fat)) • Store nutrients (adipose (fat)) • Internal framework (reticular) • Fight infection (areolar) • Cells: fibroblasts, adipocytes (fat cells) • Locations: under skin, lymph nodes, hips, behind eyeballs

12. Dense Connective Tissue Proper • Subclasses: dense regular, dense irregular, elastic • Structure: mainly tightly packed (dense) collagen fibers • Functions: • Elastic • Resist tension • Cells: fibroblasts • Locations: tendons (muscle-bone), ligaments (bone-bone), lower layers of skin, aorta (elastic)

14. Dense Irregular Connective Tissue The matrix has little ground substance and few fibroblasts; packed with bundles of irregularly arranged collagen fibers Found in the dermis of the skin Function: Provides strength and support of organs

15. Elastic Connective Tissue Extracellular matrix is packed with parallel elastic fibers; few fibroblasts and consists of very little ground substance. Found in the aorta Function: allows tissue to be stretched and then regain its original size and shape

16. Cartilage • Subclasses: hyaline, elastic, fibrocartilage • Structure: flexible, no nerves or blood • Functions: • Support • Compression • Reduces friction in joints • Matrix: Lacuna – little spaces that house the cells; ground substance is flexible • Cells: chondroblasts, chondrocytes • Locations: larynx, joints, tip of nose, ear, intervertebral discs, rib-breastbone, knee joint

18. Bone • Osseous tissue • Subclasses: compact, spongy • Structure: hard, calcified matrix; blood vessels • Functions: • support & protect • Store calcium • Blood cell formation (red marrow) • Lipid (fat) storage (yellow marrow)

19. Bone • Matrix: Lacuna and Canaliculi – little canals that connect the Central Canal to lacuna to transport nutrients, oxygen etc. to cells. • Cells: osteoblasts, osteocytes • Locations: bones (skeleton)

21. Blood • Structure: fluid within blood vessels, fibers only present during clotting • Functions: • Transport vehicle (nutrients, wastes, gases, hormones) • Cells: white blood cells (leukocytes), red blood cells (erythrocytes), platelets • Locations: blood vessels