Connective Tissue ANSC 590 Animal Growth and Development Karey L. McPhee Sept. 2, 2008

Textbook Definition A primary tissue type involved in providing structural support for tissues and organs. Framework in all organisms in which other systems are placed

Connective Tissue: Varies greatly in its physical and functional characteristics Has a rich, extensive extracellular matrix that contains relatively few active cells

Connective Tissue Proper Extracellular substance Ranges from semi-solid, glue-like substance to a rigid, amorphous material Includes: Ground Substance: viscous solution imbedded with proteinaceous fibers Fixed cells and Wandering cells Example: Blood vs. Bone and Cartilage

Cell Types Macrophages Small cells capable of movement (ameboid) Consume damaged cells and foreign substances Abundant at sites of injury

Cell Types Mast Cells Move freely w/in connective tissues Wandering cells histamines Primarily responsible for release of histamines Convey inflammation response

Cell Types Fibroblasts Fixed cells “anchored” into connective tissue Produce fibrous structures that reinforce amorphous structure

Ground Substance Fluid-like structure of connective tissue proper proteoglycans Consists of soluble proteoglycans Most prominent proteoglycans: Chondroitin Sulfates and Hyaluronic Acid  C.S. is abundant in tendons and cartilage  H.A. is very viscous and found in joints  Crucial part of synovial fluid (lubrication)

Primary Reinforcement Proteins Collagenous Fibers Reticular Fibers Elastic Fibers

Collagen Fibers Collagen: most abundant protein found in animals 20-30% of protein in the body Alpha Chain Primary sequence (polypeptide) is called Alpha Chain Relatively inelastic Coils into left-handed helix, but entire molecule is not helical Helical portions provide stability for the molecule Non-helical portions help align molecule with other Alpha Chains Procollagen Secreted from precursor molecule (from fibroblast): Procollagen

Collagen Fibers cont. Pentafibrils Ultimate structure: Pentafibrils Arranged in staggard formation Yields highly organized fibers occurring outside the cell Pentafibril strength is relatively low Tensile strength comes from cross-linkages between collagen molecules Many types of collagen fibers (11 listed in text)

Reticular Fibers Formation is similar to collagen fibers, except they do not form large bundles of fibers Very small and delicate Combined with abundant ground substance and randomly arranged creates loose type of connective tissue Parenchyma Parenchyma: surrounds many organs

Elastin Differs greatly from collagen in functional properties Contains two unique amino acids Desmosine Isodesmosine Capable of being stretched to nearly 2x their length tropoelastin Secreted from precursor molecule: tropoelastin Abundant in compliant tissues Blood vessels Ligaments Lungs Skin