Tissues a group of similar cells that perform a common function 4 Primary Tissues Epithelial covering Connective support Muscle movement Nervous control Epithelial Tissue Characteristics exhibit polarity lower attached basal surface upper free apical surface apical surface may have cilia or microvilli Microvilli are minute finger like projections of the plasma membrane of the epithelial cells They are Avascular lack blood vessels Supported directly by a Basement membrane double layered superior basal lamina abutting the epithelial tissue and a deeper reticular lamina abutting the underlying connective tissue Connective tissue underlies supports all epithelial tissues connective tissue is vascular and provides nutrients to the overlying avascular epithelial tissues by diffusing through the basement membrane They have a high regenerative capacity undergo cell division so far as they receive nutrients and substances from the underlying connective tissue They are innervated 2 Main Classes Membranous covering and lining Simple 1 layer of cells Stratified at least 2 layers of cells Glandular form the glands that secrete products in the body Endocrine Glands secrete their products directly into ECF Exocrine Glands secrete their product onto body s surfaces Unicellular Goblet cells are the only unicellular glands within membranous epithelia secrete Mucin Mucin Water Mucus Multicellular Structural Classification 2 parts Duct system simple glands unbranched compound glands branched Shape of the secretory portion of the gland Tubular forms tubes Alveolar Acinar forms flask like sacs Tubuloalveolar forms both Functional Classification Mode of Secretion Apocrine apex of the secretory cell pinches off to release accumulated products Merocrine secretory cell undergoes exocytosis to release products Holocrine secretory cell ruptures to release its accumulated products 3 Major Types Based on Shape Squamous cells flattened scale like cells with flattened disc shaped spindle shaped nuclei Cuboidal cells Cube like or box like cells with centrally placed spherical nuclei Columnar cells Tall column shaped cells with elongated nuclei placed closer to the base of the cells Other Classification of Epithelia Stratified columnar at least 2 layers apical cells are columnar shaped location ducts of glands pharynx and part of male urethra function secretion protection Stratified cuboidal at least 2 layers apical cells are cuboidal cells location lining ducts of glands such as the salivary glands and sweat glands function secretion protection Characteristics of Connective Tissues 1 They all have a common origin all connective tissues are derived from the embryonic tissue called MESENCHYME 2 They exhibit different degree of vascularity from being avascular to poorly vascular to highly vascular 3 Composed of 2 parts Nonliving portion and the living portion i Nonliving portion Extracellular matrix Ground substance and the fibers Ground substance composed of interstitial fluid cell adhesion molecules and proteoglycans Fibers 3 types Collagen fibers white fibers Elastic fibers yellow fibers Reticular fibers ii Living portion Cells that are derived from mesenchyme and they produce the connective tissue Fibroblasts produce connective tissue proper Chondroblasts produce cartilage Osteoblasts produce bone tissue hematopoietic stem cells produce blood cells Elastic Connective Tissue dense regular CT with high content of elastic fibers function exhibit the stretch recoil properties location Ligamenta flava which connects adjacent vertebrae Cartilage Produced by Chondroblasts Has a semi solid ground substance 3 types of Cartilage Hyaline cartilage embryonic cartilage epiphyseal plates articular cartilage costal cartilage Elastic cartilage epiglottis pinna Fibrocartilage intervertebral discs pubic symphysis menisci Bone osseous Tissue Living portion osteoblasts produce bone tissue Solid matrix Nonliving portion ECM Organic matrix osteoid ground substance fibers Inorganic matrix hydroxyapatites calcium phosphate crystals Keratinized stratified squamous epithelium areolar and dense irregular connective tissue Membranes as Simple Organs Cutaneous membrane Skin Mucous membrane or Nonkeratinized stratified squamous epithelium areolar CT columnar epithelium areolar CT areolar CT in mucous membrane is specifically referred to as LAMINA PROPRIA Serous membrane Simple squamous epithelium areolar CT simple squamous epithelium in serous membrane is specifically referred to as the MESOTHELIUM Synovial membrane dense irregular CT areolar CT
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