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					Connective Tissue
    Connective Tissue
   Include tissues such as bone, fat, and blood.
   Very different in appearance and function.
   Found everywhere in the body, it is the most
    abundant and widely distributed of the tissue
    types.
   Well vascularized (except tendons, ligaments,
    and cartilage)
   All connective tissue have three basic
    components.
Three basic components

   Specialized cells
   Extracellular protein fibers
   A fluid known as the ground substance
       The extracellular fibers and ground
        substance constitute the matrix that
        surrounds the cell. The extracellular
        matrix typically accounts for most of the
        volume of connective tissue.
Funtions of Connective Tissue
   Establishing a structural framework for the
    body.
   Transporting fluids and dissolved materials
    throughout the body.
   Protecting delicate organs.
   Supporting, surrounding, and
    interconnecting other tissue types.
   Storing energy reserves.
   Defending the body from invading
    microorganisms.
Classification of Connective
Tissue

   Connective tissue proper
   Fluid connective tissue
   Supporting connective tissue
Connective Tissue Proper
   Connective tissue with many types of cells and
    extracellular fibers in a syrupy ground substance.
   Differ in number of cell types they contain and the
    relative properties and proportions of fibers and
    ground substance
   Divided into two categories based on the relative
    number of fibers, cells, and ground substance.
       Loose connective tissue
       Dense connective tissue
   Adipose tissue and tendons help comprise
    connective tissue proper.
Connective Tissue Proper:
Cell Population
   Fibroblasts – most abundant permanent
    resident, they are the only cell that are
    always present in every connective tissue
    proper.
   Macrophages – engulf pathogens or
    damaged cells that enter the tissue.
   Adipocytes
   Mesenchymal Cells – stem cells that
    respond to local injury by producing
    daughter cells that become fibroblasts,
    macrophages or other type of connective
    tissue cell.
   Melanocytes – synthesize and store the
    brown pigment melanin.
   Mast Cells – small, mobile, found near blood
    cells and contain histamine and heparin
    which are released after injury or infection.
   Lymphocytes – migrate throughout the
    body, may develop into plasma cells.
   Microphages – phagocytic blood cells.
Connective Tissue Fibers
   Collagen Fibers – long, straight, and unbranched.
    Most common fibers in connective tissue proper.
    Flexible and stronger than steel when pulled from
    either end. Tendons and ligaments are made of
    collagen fibers.
   Reticular Fibers – thinner than collagen fibers and
    form a branching interwoven framework that is
    tough, flexible and can withstand forces applied
    from many different directions.
   Elastic Fibers – contain the protein elastin, fibers
    are branched and wavy. After stretching they will
    return to their original length. Relatively rare but
    have important functions.
Loose Connective Tissue
   Also known as areolar tissue.
   Is the “Packing Material” of the body.
   It fills space between organs, provides
    cushioning, supports epithelia, blood
    vessels and nerves, as well as providing a
    route for the diffusion of materials.
   The least specialized connective tissue in
    the body, has an open framework, can
    distort without damage.
   Two types of loose connective tissue.
Adipose Tissue

   Adipose tissue provides padding, cushions
    shock, acts as an insulator, serves as
    packing or filler around structures.
   Common under the skin of the groin,
    buttock, sides, and breasts. Fills in the bony
    sockets behind the eye, surrounds the
    kidney, and dominates extensive areas of
    loose connective tissue in the pericardial
    and abdominal cavities.
Reticular Tissue

   Found in organs such as the spleen
    and liver.
   Creates a three dimensional network,
    stroma, that supports the functional
    cells of these organs.
   This fibrous framework is also found in
    lymph nodes and bone marrow.
Dense Connective Tissue
   Often called collagenous tissues because
    collagen fibers are the dominant type.
   Two types of dense connective tissue in the
    body:
       Dense regular – collagenous fibers are arranged
        parallel to each other, packed tightly, and
        aligned with forces applied to the tissue.
       Dense irregular – form an interwoven framework
        and do not show any consistent pattern. These
        tissues provide strength and support to areas
        open to stresses from many directions.
Fluid Connective Tissue

   Distinctive population of cells.
   Suspended in a watery matrix that
    contains dissolved proteins.
   Two fluid connective tissues
       Blood
       Lymph
Blood
   Contains blood cells and fragments known
    collectively as formed elements.
   Red blood cells (erythrocyte) make up
    almost half the volume of blood.
   Plasma, the watery ground substance,
    contains white blood cells and leukocytes.
   Also contains platelets that function in the
    clotting response that seals breaks in the
    endothelial lining.
Lymph

   Forms as interstitial fluid and enters small
    passageways, lymphatics, that return it to
    the cardiovascular system.
   Cells of the immune system monitor the
    composition of lymph and respond to signs
    of injury and infection.
   99% of the cells in lymph are lymphocytes
    (the rest are macr & microphages).
Supporting Connective Tissue

   Less diverse cell population than
    connective tissue proper and a matrix
    that contains tightly packed fibers.
   Two types of supporting connective
    tissue
       Bone
       Cartilage
Cartilage

   The matrix of cartilage is gel like whose
    characteristics vary depending on the
    predominant fiber type.
   Cartilage cells are known as chondrocytes
    and they are the only cells found in the
    matrix.
   Avascular – all nutrient and waste product
    exchange must occur by diffusion through
    the matrix.
   Cartilage grows by two mechanisms:
       Interstitial growth
       Appositional growth
   Three major types of cartilage:
       Hyaline Cartilage – most common type.
       Elastic Cartilage – extremely resilient and
        flexible.
       Fibrocartilage – little ground substance,
        dominated by collagen fibers.
Hyaline Cartilage

   Location – between tips of ribs and
    bones of sternum; covering one
    surfaces at synovial joints; supporting
    larynx, trachea, and bronchi; forming
    part of nasal septum.
   Functions – provides stiff but
    somewhat flexible support; reduces
    friction between bony surfaces.
Elastic Cartilage

   Location – tip of nose; epiglottis.
   Function – provides support but
    tolerates distortion without damage
    and returns to original shape.
Fibrocartilage

   Location – pads within knee joints;
    between pubic bones of pelvis;
    intervertebral discs.
   Function – resists compression;
    prevents bone-to-bone contact; limits
    relative movement.
Bone
   The matrix of bone is said to be calcified
    because it contains mineral deposits,
    primarily calcium salts. This is what gives
    bone its rigidity.
   Ground substance is very small. One third of
    the bone matrix is made of collagen fibers.
   The minerals are organized around the
    collagen fibers resulting in a strong, flexible
    combination resistant to shattering.
   Can compete with the best steel reinforced
    concrete.

				
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