Tissue The Tissue Level of Organization Chapter 3 Definition an aggregation of cells in which each cooperates with all others in the performance of a given function Examples of general functions Movement Protection Support Production of chemicals Epithelial Connective Muscular Nervous Principal Tissue Types Functions Coverings and linings Forms glands Characteristics Closely packed cells Basement membrane Nerves Avascular Cell growth and replacement by mitosis Classification Simple or stratified Squamous, cuboidal, columnar, or transitional Epithelial Tissue Squamous Epithelium Epithelia of Coverings and Linings Simple Squamous Epithelium Highly adapted to diffusion, osmosis, & filtration Stratified Squamous Epithelium Surface layer is flat Function - protection 1
Cuboidal Epithelium Simple cuboidal epithelium Lines glands and their ducts Function secretion and absorption Stratified Cuboidal epithelium Surface layer cube-shaped Function protection Columnar Epithelia Simple columnar epithelium Functions protection, absorption, secretion Pseudostratified columnar epithelium Appear stratified but all cells connect to the basal lamina Functions protection, secretion Glandular Epithelium Gland 1 or more cells Unicellular gland goblet cell Multicellular secretory sheets or groups of cells Serous Mucous Mixed Cytogenic Function secretion Types Exocrine to surface or ducts Endocrine to blood Transitional Epithelium Can be stretched Lines hollow structures that expand Function prevents rupture of organ http://www.mhhe.com/biosci/ap/histology_mh/stratepi.html Pseudostratified Columnar Epithelium Appear stratified but all cells connect to the basal lamina Functions protection, secretion Mechanisms of Glandular Secretion Merocrine Secretion is released by exocytosis Apocrine Residual name Mainly merocrine Secretion is released by pinching off of vesicles Holocrine Secretion is released by entire cell bursting 2
Connective Tissue Most abundant tissue Functions are varied Characteristics Specialized cells, widely scattered Rich blood supply Much matrix Extracellular fibers Ground substance Classification of Connective Tissues Embryonic Mesenchymal cells Adult connective tissues Embryonic Connective Tissues Cell Types Found in Connective Tissue Fibroblasts Secrete the molecules that form the matrix Ground substance Water and glycoproteins Fibers Fixed cells Fibrocytes Macrophages Big eaters May be fixed or wandering Additional Connective Tissue Cells Adipocytes Fixed fat cells Mesenchymal cells Fixed cells that can divide (mitosis) to replace damaged connective tissue Melanocytes Fixed cells that store melanin Lymphocytes Wandering immune system cells Mast cells Around blood vessels Wandering cells that produce histamine & heparin Connective Tissue Fibers Collagen fibers Most common type White Strong, ropelike Form ligaments, tendons Reticular fibers Thin Woven into rough, flexible network Elastic fibers Yellow Thin Stretch Contain elastin 3
Loose (Areolar) Connective Tissue Types of Connective Tissue Fibers not abundant Binds epithelia to deeper tissue Contains all 3 types of fibers Examples of locations Between skin and muscles Around digestive tract Around blood vessels Most of the volume is adipocytes Provides padding, slows heat loss, food reserve Wherever there is loose connective tissue Adipose Tissue Reticular fibers form a strong network Provides strength and support Lymphatic organs Forms the framework (stroma) of many organs Binds together cells of smooth muscle Reticular Tissue Dense Connective Tissue Types Dense Regular Connective Tissue Dense Irregular Connective Tissue Elastic Connective Tissue Dense Regular Connective Tissue Lots of collagen fibers in bundles Cells fibroblasts in rows between bundles Examples Tendons, ligaments 4
Dense Irregular Connective Tissue Random arrangement of fibers Resists stress Occurs in sheets Periosteum Perichondrium Fibrous capsules of some organs Dermis Elastic Tissue Lots of elastic fibers Fibroblasts in spaces between fibers Provides stretch and strength Cartilage Growth of Cartilage Dense network of collagenous fibers & elastic fibers in a gel-like substance Avascular Cells chondrocytes in lacunae Chondroblasts Perichondrium surrounds surface of cartilage Growth Interstitial growth Appositional growth Hyaline cartilage Fibrocartilage Elastic cartilage Types of Cartilage Most common Provides flexibility and support Ends of bones Trachea Larynx Embryonic skeleton Hyaline Cartilage 5
Visible collagenous fibers with scattered chondrocytes Provides strength and rigidity Intervertebral discs Symphysis pubis Fibrocartilage Threadlike network of elastic fibers with chondrocytes Provides strength and maintains shape Pinna Eustacian tube Elastic Cartilage Solid matrix Cells Osteocytes in lacunae Central canal (Haversian canal) Lamellae Osteon (Haversian system) Canaliculi Periosteum Bone Functions Transport medium Regulation Protection Composition Plasma fluid Formed elements cells & cell fragments Erythrocyte Leukocyte Thrombocyte Blood A Red Blood Cell SEM of RBCs 6
Epithelial layer + underlying connective tissue = epithelial membrane Types Mucous membrane Serous membrane Cutaneous membrane Synovial membrane Endothelium Membranes Fascia Fascia collective term for sheets of connective tissue Functions Provide strength and stability Maintain positions of internal organs Provide a route for the distribution of blood vessels, lymphatics, and nerves 3 types Types of Fascia Superficial Fascia Adipose tissue and loose connective tissue Immediately deep to the skin Deep Fascia Dense connective tissue Strong internal framework Subserous Fascia Loose connective tissue Between deep fascia and serous membranes Muscular Tissue Specialized cells Function - contraction 3 types Skeletal muscle Cardiac muscle Smooth muscle Skeletal Muscle Cardiac Muscle Connected to bones Striated Multinucleated Voluntary Found in the heart Striations Branched cells Intercalated discs Involuntary 7
Smooth Muscle Nervous Tissue Found in walls of internal organs Nonstriated Involuntary Specialized cells Function conduction of electrical impulses Cells Neurons Neurosoma Axon Dendrites Neuroglia 8