Biology 325 Lab 1 Histology Fall 2004 Lab notes Histology I Introduction tissue group of cells that are closely associated similar in structure and function and perform a common or related function four primary tissues epithelial tissue connective tissue muscle tissue nervous tissue II Epithelial tissue cell layers are arranged in sheets A General comments epithelial tissues form the membranes and the glands of the body 1 Membranes covering and lining epithelium sheets of cells that cover external surfaces or line internal surfaces functions include protection absorption filtration excretion secretion 2 Glands composed of cells mostly specialized for secretion can be unicellular or multicellular multicellular glands originally develop as downgrowths of epithelial membranes into underlying connective tissue secretions can be mucous or aqueous B Distinctive characteristics of epithelial tissue 1 Cellularity cells lie close together little to no intercellular material 2 Specialized contacts cells fit together to form a continuous sheet adjacent cells are bound together at many points by lateral contacts 3 Polarity surface specialization microvilli cilia distinctive apical top and basal surfaces bottom 4 Basement membrane border between the epithelium and connective tissue below it present 5 Innervated but avascular therefore metabolism depends on diffusion of nutrients from blood vessels in connective tissue below 6 Regeneration has a high capacity to regenerate renew itself C Classification of epithelium by number of cell layers present and by shape of the superficial cell layers 1 Number of cell layers a Simple epithelium single layer of cells important in filtration and absorption b Stratified epithelium two or more cell layers important for protection in high abrasion areas Biology 325 Lab 1 Histology Fall 2004 Lab notes c Pseudostratified epithelium all cells contact basement membrane not all cells reach the surface nuclei at different levels important in secretion and protection 2 Shape a Squamous flattened cells with flattened nuclei b Cuboidal cube like cells with spherical nuclei c Columnar column shaped rectangular cells with oval nuclei D Types of epithelium 1 Simple Epithelium a Simple squamous epithelium single layer of flattened cells located in air sacs of lungs lining inside of blood vessels function involves permitting easy passage of materials by simple diffusion where protection not critical b Simple cuboidal epithelium single layer of cube like cells located in kidney tubules secretory portions of small glands functions in secretion and absorption c Simple columnar epithelium single layer of tall cells located lining most of the digestive tract stomach to anus ciliated variety found lining portions of respiratory tract uterine tubes and regions of uterus functions in secretion of mucous and enzymes and absorption 2 Stratified epithelium a Stratified squamous epithelium thick membrane composed of several layers of cells where basal cells are cuboidal or columnar and metabolically active and surface cells are squamous and often dead forms top layer of skin the epidermis functions in protection b Stratified cuboidal epithelium two layers of cube like cells ducts of sweat salivary mammary glands c Stratified columnar epithelium rare sheet several cell layers thick basal cell usually cuboidal and superficial cells elongated d Transitional epithelium resembles both stratified squamous or stratified cuboidal depending on the degree of stretch or distension of organ in question urinary bladder Biology 325 Lab 1 Histology Fall 2004 Lab notes III Glandular epithelium a gland is composed of one or more cells that make and secrete a particular product secretion is an aqueous fluid that contains proteins there are two types based on the route of secretion exocrine glands more abundant salivary and sweat glands pass secretions to the surface through a duct thus components include secretory units and ducts endocrine glands no connection to the surface secretions go directly to the blood stream hormone secretion thus highly vascularized also classified on basis of type of secretion mode of secretion cell numbers making up gland duct secretory unit structure IV Connective tissue found everywhere in the body most abundant and widely distributed of primary tissues amount of connective tissue varies greatly from organ to organ A General comments subdivided into connective tissue proper cartilage bone and blood functions in support protection insulation transportation connective tissue is able to bear weight withstand tension and endure trauma common characteristics of all connective tissue common origin all arise from mesenchyme wide degrees of vascularity cartilage is avascular dense connective tissue is poorly vascularized and areolar loose connective tissue is well vascularized CT composed predominantly of ECM therefore CT is able to bear weight withstand tension and endure trauma B Structural elements of connective tissue in any type of connective tissue there are three types of elements ground substance cells and fibers the type of connective tissue depends on the type s of cell s that predominate the tissue the types of fibers present and the composition of the ground substance 1 Ground substance everything between fibers and cells unstructured material that fills in the space between cells composed mainly of water and proteins in solution produced by cells of connective tissue functions as a medium through which nutrients and other substances can diffuse between the capillaries and cells Biology 325 Lab 1 Histology Fall 2004 Lab notes 2 Fibers provide support made up of groups of fibrous proteins intertwined with one another produced by cells of connective tissue three major types of fibers collagen elastin reticular fibers collagen is extremely tough gives tissue great strength elastin gives tissue recoil ability elasticity 3 Cells each major type of connective tissue has a fundamental cell type each major type of connective tissue has a fundamental cell type that exists in immature blast and mature cyte forms fibroblasts in connective tissue proper chondroblasts in cartilage osteoblasts in bone a Fundamental cell type immature cell actively mitotic cells secrete ground substance produce the extra cellular matrix ECM mature cell less active maintain the ECM can revert to the active state for repair and regeneration of the matrix b Connective tissue is also the home to an