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Connective tissues
 

Connective tissues

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    Connective tissues Connective tissues Presentation Transcript

    • Connective Tissues
    • Connective Tissues
      Responsible for providing and maintaining form in the body
    • Histogenesis
      Mesodermal in origin
    • General Characteristics
      Are made up of fewer cells that are set far apart
      They are supported by abundant intercellular substance
      They also contain connective tissue fibers
      The different contents of intercellular substance, CT cells and fibers account for the difference in appearance of the various connective tissues
    • General Functions
      Provide a matrix that serves to connect and bind the cells and organs
      Give mechanical support to the body
      Storage of fat and certain minerals like calcium in the bones
      Exchange of metabolites between blood and tissues
      Significant role in the repair and healing of wounds
      For protection against infection
    • Classification
      I. Connective Tissue Proper
      Loose connective Tissue
      Dense connective tissue – regular & irregular
      II. Connective Tissue with special properties
      Adipose CT
      Elastic CT
      Hematopoietic CT(lymphatic and myeloid)
      Mucous CT
      III. Suporting Connective Tissue
      Cartilage
      Bone
    • Composition of Connective Tissues
      Connective tissue cells
      Connective tissue fibers
      Intercellular or Ground substance
      Blood vessels – except in Mucous CT and in cartilage
    • Connective Tissue cells
      Fixed or permanent
      Wandering cells
      Are immigrant cells usually from blood or bone marrow. Some retain their original characteristics and may take up permanent residence there:
      1. mast cells
      2. plasma cells
      3. pigment cells
      4. blood leukocytes
      Are native to the tissue in which they are found:
      1. undifferentiated mesenchymal cells
      2. fibroblasts
      3. macrophages
      4. fat cells
    • Fixed Connective Tissue Cells
    • Undifferentiated Mesenchymal cells
      Precursor of most cells indigenous to CT including fibroblasts and adipose cells
      Adventitial cells remain undiifferentiated in adult CT and constitute a reserve population of stem cells
      Perivascular cells, often located along the walls of blood vessels
      Are difficult to distinguish from active fibroblasts – recognition come not with the microscope but from numerous observations of their responses to certain stimuli
      Pluripotential cells, capable of differentiation either into the usual cell types or into other cell types such as smooth muscle cells
    • Fibroblasts
      Predominant CT cells
      Considered to be responsible for the formation of the fibers and are also thought to elaborate most, if not all, of the amourpous ground substance
      Are large, flat branching cells which appear fusiform or spindle shaped in profile
      Classified as:
      lamellar or pyriform-shaped (youngest)
      Spindle or fusiform (intermediate in age)
      Stellate or star-shaped (mature)
    • Fibroblasts
    • Macrophages
      As numerous as fibroblasts in loose CT
      Often termed histiocytes, are most abundant in richly vascularized areas
      May either be:
      Fixed or resting (attached to the fibers of the matrix)
      Free, wandering (derived from the immigration of monocytes from the blood)
      Capable of ameboid movement – very irregular in outline with pseudopodia extending in numerous directions
    • Macrophages
      Act as scavengers, (motility and phagocytic activity) engulfing extravasated blood cells, dead cells, bacteria and foreign bodies
    • Fat cells
      Fully differentiated cells and are incapable of mitotic division
      Signet-ring appearance – cytoplasm is so thinned that it appears as a narrow rim around the edge of a single large lipid droplet with the nucleus fused to one side of the cell membrane
      Types:
      Yellow or white – found in most of the bulk of the human body
      Brown fat cells – concerned with heat production, particularly important in newborn and young animals
    • Fat cells
    • Wandering Connective Tissue Cells
    • Mast cells
      Round to oval CT cells whose cytoplasm is filled with basophilic granules
      The rather small and spherical nucleus is centrally situated and is frequently obscured by the cytoplasmic granules
      Produce an anticoagulant similar if not identical to heparin
      Produce histamine in allergic response to some foreign proteins
    • Mast cells
      Also elaborate serotonin, a vasoconstrictor
      Are only seen along the course of small blood vessels
    • Plasma cells
      Spherical cells with rounded or irregular nuclei generally eccentrically located , whose chromatin materials exhibit a characteristic “checker-board”, “clock-faced”, “cart-wheel” appearance
      Has an important function in resistance to disease and known as the: principal producer of antibodies
    • Plasma Cells
    • Pigment cells
      Resemble the fibroblast but whose cytoplasm contains pigment granules that never invade the nucleus
      Types:
      Dermal chromatophore– found in the dermis of the skin, retina, choroid and iris of eyeball
      Epidermal melanocytes, found in common mole and are responsible for the manufacture of melanin granules
    • Blood Leukocytes
    • Lymphocytes
      Smallest, with rounded nucleus which occupies most of the cytoplasm
      Concerned with antibody production
    • Eosinophils
      Have bilobed nucleus with spherical, darkly staining acidophilic granules
      Found abundant in lactating breasts, respiratory and alimentary tracts, and in certain allergic reactions
    • Neutrophils
      First line of defense, seen in regions of acute inflammation
      Have a segmented nucleus (3-5 lobes) having fine granules which are purple or violet in color
    • Monocytes
      Largest, they have a kidney-shaped nucleus and are considered as the phagocytes of the blood
    • Connective tissue cells
    • Ground Substance
    • Ground substance
      Colorless, transparent and homogenous
      Fills the space between cells and fibers of the CT
      It is viscous and acts as lubricant and also as a barrier to the penetration of the tissues by foreign particles
      Formed mainly by two classes of components:
      Glycosaminoglycans
      Structural glycoproteins
    • Connective Tissue Fibers
      Collagen formed by the protein collagen,
      Reticular most abundant protein of the body
      Elastic – composed mainly of the protein elastin
    • Collagen fibers
      Most numerous fiber in CT
      Fibers are colorless stands, but when present in great numbers, they cause the tissue in which it lie to be white
      Are inelastic and have a tensile strength greater than steel
      Imparts a unique combination of flexibility and strength to the tissues in which it lies
    • Collagen fibers
      Consists of closely packed thick fibrils with an average diameter of 75 nm
      In many parts of the body, are organized in parallel array forming collagen bundles
      In H & E sections, large or small bundles of fibrils or individual fibrils exhibit acidophilic staining properties
    • Types of Collages fibers
      Collagen type I
      Most abundant and has a widespread distribution (90% of the collagen in the body)
      Found in the dermis of the skin, tendons, bone, teeth and virtually all CT
      Collagen type II
      Present mainly in hyaline and elastic cartilage
      Only very thin fibrils are formed
    • Types of collagen fibers
      Collagen type III
      Often found in association with type I and is probably the major collagenous components of reticular fibers
      Can copolymerize with other types of collagen
      Collagen type IV
      Is the major collagen type in basal lamina
      Does not form fibrils or fibers
      Collagen type V
      Present in fetal membranes and blood vessels and in small amounts in other tissues
    • Reticular fibers
      Are extremely thin, with a diameter between 0.5 and 2 μm
      Not visible in hematoxylin and eosin stains but can be easily stained black by impregnation with silver salts
      Argyrophilic fibers – affinity to silver salts
      During embryogenesis, inflammatory processes, and wound healing, most connective tissues have an abundance of reticular fibers, but these are subsequently replaced by regular collagen fibers
    • Reticular fibers
      Particularly abundant in smooth muscles, endoneurium, and the framework of hematopoietic organs (e.g. spleen, lymph nodes, red bone marrow) and constitute a network around the cells of parenchymal organs (e.g. liver, kidney, endocrine glands)
    • Elastic fibers
      Consists of an albuminoid protein called elastin
      Range in diameter from 0.1 to 10 µm
      Histologically contains few charged amino acids so it stains poorly with standard ionic dyes
      Special stains such as Verhoeff’s stain and Weigert’sResorcin-fushsin stain are used in light microscope
      Are extremely pliable and elastic
      Can be stretched to 150% of their length without breaking and then return to their original length
    • Elastic fibers
      Found where their mechanical properties are necessary to allow tissues to stretch or expand and then return to their original shape, e.g. in arterial walls, interalveolar septa, bronchi and brionchioles of the lungs, vocal ligaments and ligamentaflava of the vertebral column