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Overview of Tissues Learning Objectives Identify the four primary tissues Compare and contrast primary tissue structure and function Identify examples of epithelial and connective tissue and where they are located Compare and contrast the structure and function of epithelial and connective tissue types Identify the three types of epithelial membranes Histology The science that deals with the study of tissues. Hist – tissue ology – study of Types of Tissue Epithelial Connective Muscle Nervous Overview of Epithelial Tissue Covering and Lining Epithelium Covers body surfaces Lines body cavities, hollow organs and ducts Glandular Forms glands Epi – on top thelium - covering General Features of Epithelium Consists of packed cells with little extracellular material between them Cells are arranged in continuous sheets, in either single or multiple layers Have a free surface and a basal surface – Lumen – the hollow space in an organ or tube Are avascular : a- without vascular- blood vessels Have nerve supply High capacity for renewal by cell division Functions of Epithelium Protection Secretion Absorption Excretion Sensory reception Generation of gametes Types of Epithelial Tissue Covering and Lining Epithelium Classification by shape Squamous - flat Cuboidal – cubes or hexagons Columnar – tall, rectangular and cylindrical Transitional – range in shape from flat to columnar and often change shape Classification by Arrangement of Layers Simple – single layer in areas of diffusion, osmosis, filtration, secretion and absorption Stratified – two or more layers used for protecting underlying tissues Pseudostratified columnar – contains one layer, appears to have several layers but not all cells reach the surface, ciliated or secrete mucous Simple Squamous Epithelium Single layer, flat cells, central nucleus Lines the heart, blood vessels, lymphatic vessels, alveoli, glomerular capsules, and forms the epithelial layer of serous membranes Function: filtration, diffusion, osmosis, secretion in serous membranes Simple Cuboidal Epithelium Single layer, cube shaped, central nucleus Lines the tubes and smaller ducts of the kidneys Function: secretion and absorption Noncilialted Simple Columnar Epithelium Single layer, nonciliated, rectangular, cylindrical cells, nucleus at base, contain goblet cells, some have microvilli Goblet cells make and secrete mucus Lines GI, respiratory, reproductive and urinary tracts Function: secretion and absorption Ciliated Simple Columnar Epithelium Single layer, ciliated, rectangular, cylindrical cells, nucleus at base, some goblet cells Lines portions of trachea and upper respiratory tract, Fallopian tubes, uterus, some paranasal sinuses and central canal of the spinal cord Function: moves mucus and other substances Stratified Squamous Epithelium Several layers, cuboidal or columnar deep, squamous superficial, basal cells replace surface cells Keratinized epidermis, nonkeratinized lines the mouth, esophagus, vagina and tongue Function: protection Stratified Cuboidal Epithelium Two or more layers, superficial cells cubeshaped Ducts of adult sweat glands and part of male urethra Function: protection and limited secretion and absorption Stratified Columnar Epithelium Several layers, irregularly shaped cells, columnar cells superficial Lines part of urethra and large excretory ducts Function: protection and secretion Transitional Epithelium Variable cell shapes, superficial cells squamous when stretched, cuboidal when relaxed Lines urinary bladder and portions of ureters and urethra Function: permits organs to stretch without rupturing Pseudostratified Columnar Epithelium Not true stratified tissue, cells at different layers, all cells attached to basement membrane, only some reach surface Ciliated lines airways of most of the upper respiratory tract (trachea) Function: secretion and movement of mucus Glandular Epithelium Endocrine – ductless glands Pituitary, thyroid, and adrenal glands Exocrine – glands with ducts Sweat and salivary glands Connective Tissue General Features Two basic elements: cells and a matrix Does not occur on body surfaces Has a nerve supply, except cartilage Usually highly vascular except cartilage (avascular) and tendons Various tissue types confer a variety of functions Two Major Types Embryonic – found in the embryo and fetus Mature – present in newborns to adults Connective Tissue Cells Fibroblasts Macrophages Plasma Cells Mast Cells Adipocytes Leukocytes Connective Tissue Matrix Ground substance Fibers Connective Tissue Fibers Collagen Elastic Reticular Embryonic Connective Tissue Mesenchyme – tissue from which mature connective tissue will arise Mucous Connective Tissue – found primarily in the umbilical cord of the fetus Mature Connective Tissue Loose Connective Tissue Dense Connective Tissue Cartilage Bone Blood Lymph Loose Connective Tissue Areolar Connective Tissue Adipose Tissue Reticular Connective Tissue Areolar Connective Tissue Fibers and several kinds of cells embedded in a semifluid ground substance Subcutaneous layer deep to skin, superficial part of dermis, mucous membranes, around blood vessels, nerves and body organs Function: strength, elasticity, and support
