Part II – Connective Tissue

 Most abundant and widely distributed tissue  Main classes: 1.Connective tissue proper (loose & dense) 2.Cartilage 3.Bone 4.Blood  Functions: 1.Binding and support 2.Protection 3.Insulation 4.Transport substances

 Variation in Blood supply ◦ Vascular – connective tissue proper, blood, bone  Tendons & ligaments are poorly vascular  Cartilage is avascular  Do not appear on surface ◦ Unlike epithelial  Extracellular matrix ◦ secreted by cells that provides structural and biochemical support ◦ Ground substance: fills spaces, surrounds fibers, clear, colorless, and has the consistency of syrup  water + adhesion proteins + polysaccharides  Fibers ◦ provide support  Collagen - no branching; strength  Elastic – branched; provides stretch  Reticular – fine branched network, “skeleton” of organs

 Collagen ◦ As you get older, your body makes less collagen, and individual collagen fibers become increasingly cross-linked with each other.  stiff joints from less flexible tendons, or wrinkles due to loss of skin elasticity ◦ Plastic surgery? ◦ Put it through hydrolysis  gelatin

 Known as the universal packing material  Subclasses: areolar, adipose, reticular  Structure: softer, fewer fibers, gel-like matrix  Functions: ◦ Cushion & protect organs (areolar, fat) ◦ Store nutrients (fat) ◦ Internal framework of support (reticular) ◦ Fight infection (areolar)  Cellular makeup: fibroblasts, adipocytes (fat cells)  Locations: under skin, lymph nodes, hips, behind eyeballs

 Functions: Cushioning surrounding organs, connecting different tissues, and supporting blood vessels  Made up of: collagenous, elastic and reticular fibers and ground substance

 Functions: store energy in the form of fat, although it also cushions and insulates the body.  In mammals, two types of adipose tissue exist: ◦ white adipose tissue (WAT) ◦ brown adipose tissue (BAT).  Adipose tissue is primarily located beneath the skin, but is also found around internal organs.

 Named for the reticular fibers which are the main structural part of the tissue.  Cells that make the reticular fibers are fibroblasts called reticular cells.  Function: fibers form a soft internal skeleton that supports other tissues  Found: lymph organs, spleen, and bone marrow

 Poor circulation, build up of toxins, pressure on connective tissue  Hormones to blame?  90% of women have it  Why not seen in men as much? ◦ Women have less supportive connective tissue to keep fat cells in place.

 Tendons & ligaments  Subclasses: dense regular, dense irregular, elastic  Structure: mainly collagen fibers  Functions: ◦ Elastic ◦ Resist tension  Cells: fibroblasts  Locations: tendons (muscle-bone), ligaments (bone-bone), lower layers of skin.

RegularIrregular  Parallel fibers  Tears when stressed in the incorrect direction  Found: tendons, ligaments  Woven network of fibers  Can be stressed in many directions  Found: lower levels of skin ◦ 4/5 of all skin tissues are dense irregular

 Subclasses: hyaline, elastic, fibrocartilage  Structure: flexible, no nerves or blood  Functions: ◦ Support ◦ Compression  Cells: chondrocytes ◦ Create and maintain the cartilaginous matrix  Locations: larynx, joints, tip of nose, ear, intervertebral discs, rib-breastbone, knee joint.

 Resembles hyaline cartilage but it also has elastic fibers  Provides flexibility and support ◦ Found in the outer ear, epiglottis, larynx  Helps with joint movement, bone growth, strengthens respiratory tract  Found in bronchi, joint surface, larynx

 Densely packed collagen fibers ◦ fibers that are in wavy lines  Function: Support and protection  Found: bone joints, knee, backbone

 Osseous tissue  Subclasses: compact, spongy  Structure: hard, calcified matrix; blood vessels  Functions: ◦ support & protect ◦ Store calcium ◦ Blood cell formation (marrow)  Cells: osteoblasts, osteocytes ◦ Synthesize bone  Locations: bones

 Vascular tissue  Subclasses: blood cells, plasma  Structure: fluid within blood vessels, no fibers  Functions: ◦ Transport vehicle (nutrients, wastes, gases, hormones)  Cells: white blood cells (leukocytes), red blood cells (erythrocytes), platelets  Locations: blood vessels