Part II – Connective Tissue

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

 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 ◦ Most abundant protein in the body (25-35%) ◦ 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 Gelatin can come from the collagen in cow or pig bones, hides and connective tissues. Today, the gelatin in Jell-O is most likely to come from pigskin. Collagen doesn't dissolve in water in its natural form, so it must be modified to make gelatin. 1.Manufacturers grind the body parts and treat them with either a strong acid or a strong base to dissolve the collagen. 2.Then the pre-treated material is boiled. Controls at every step of the process ensure purity and safety. 3.During this process, the large collagen protein ends up being partially broken down; the resulting product is a gelatin solution. 4.That solution is chilled into a jelly-like material, cut and dried in a special chamber. At this point, the dried gelatin -- about 10% water -- is ground. If it's going to make Jell-O, it will be ground into a fine powder.

 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) – dominant fat type in the body, less mitochondria but biggest energy reserve ◦ brown adipose tissue (BAT) – iron containing mitochondria, burns calories for heat; mainly found in hibernating mammals and babies  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: ◦ Elasticity, strength ◦ 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 (dermis) of skin – arranged in sheets ◦ 4/5 of all skin tissues are dense irregular

 Lots of elastic fibers give “squiggly” appearance  Function: Allows stretching of organs  Found: lungs, around elastic arteries, and vocal cords

 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