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Exercise 6 Classification of Tissues What is a tissue? Group of cells Similar structure & function 4 Major Tissue Types Epithelial Connective Muscle Nervous Epithelial Tissues Cover surfaces Simple or stratified? Simple = 1 layer of cells attached to basement membrane Stratified = 2 or more layers Named by “shape” of top layer (apical layer), not bottom (basal layer) Epithelial Tissues Shapes of Epithelial Cells Squamous Simple squamous Cuboidal Flattened Cubelike Columnar Column-shaped Stratified squamous Simple cuboidal Stratified cuboidal Simple columnar Stratified columnar Epithelial Tissues Simple squamous epithelium Epithelial Tissues Simple cuboidal epithelium Fig 4-4 Epithelial Tissues Simple columnar epithelium Epithelial Tissues Pseudostratified columnar epithelium Actually simple columnar: nuclei are at different levels so there appears to be more than one layer Fig 4-5 Epithelial Tissues Stratified squamous epithelium Epithelial Tissues Stratified cuboidal epithelium Epithelial Tissues Stratified columnar epithelium Fig 4-5 Epithelial Tissues Transitional epithelium Stratified squamous epithelium formed of rounded cells that can slide over one another, allowing the organ to stretch: urinary system only Fig 4-4 CONNECTIVE TISSUES Embryonic connective tissue mesenchyme Loose connective tissue Areolar, adipose, reticular Dense connective tissue Dense irregular, dense regular Supportive connective tissue Hyaline, elastic, fibrocartilages; bone Fluid connective tissue Blood, lymph CONNECTIVE TISSUES Differing proportions of cells & fibers to “matrix” Matrix noncellular, nonliving material between connective tissue cells Different proportions strength of tissue Classification of Connective Tissues Fig. 4-8 Many cell types Distinct cell types Less diverse cell types Syrupy ground substance Watery matrix More fibrous matrix Embryonic Connective Tissue Mesenchyme Many star-shaped stem cells Gives rise to all other connective tissues Not present in adults Fig. 4-10 Loose Connective Tissue: Areolar Adipose Connective Tissue Adipose connective tissue (fat) Insulation for the body’s tissues Food storage Little matrix Fig. 4-11 Reticular Connective Tissue Reticular connective tissue Reticular fibers form a soft internal skeleton for support Dense Irregular Collagenous Connective Tissue Dense Irregular Elastic Connective Tissue Dense Regular Collagenous Connective Tissue Dense regular connective tissue Fibers in one direction Tendons, ligaments of body’s joints Fig. 4-12 Dense Regular Elastic Connective Tissue Hyaline Cartilage Connective Tissue Elastic Cartilage Connective Tissue Elastic Cartilage Maintains shape, but flexible Many elastic fibers Fibrocartilage Connective Tissue Fibrocartilage Strength, shock absorption Dense network of collagen fibers Osseous Connective Tissue Osseous Connective Tissue (Bone) Support, protection Blood Connective Tissue Lymph Connective Tissue Lymph Fluid of the lymphatic system Like plasma without the big proteins Immune defense MUSCLE TISSUES Skeletal Cardiac Smooth Skeletal Muscle Tissue Cardiac Muscle Tissue Only in the heart Striated tissue Under involuntary control Branching, uninucleate cells with intercalated discs Smooth Muscle Tissue Found in the walls of hollow organs (digestive, urinary tracts; blood vessels) 2 layers at right angles for contraction/dilation of the organ cavity Not striated tissue Uninucleate, spindle-shaped cells Muscle type Cells striations Voluntary? Cardiac branched Uninucleate Intercalated discs yes no Skeletal Long fibers multinucleate yes yes Smooth Spindle shaped 1 nucleus no no NERVOUS TISSUE Brain, spinal cord, nerves 2 basic cell types: Neuroglia cells Protect, support, insulate neurons Neurons Receive stimuli & conduct nerve impulses