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Transcript
4 The Tissue Level of Organization Overview of Tissue Science Histology: The study of tissues Four Basic Tissue Types • • • • Epithelial Connective Muscular Neural Overview of Tissue Science Key Notes: Tissues are collections of cells and extracellular material that perform a specific but limited range of functions. The four tissue types, in varying combinations, form all of the structures of the human body. Overview of Tissues Epithelial Tissue - Includes epithelia & glands Epithelia: - layers of cells that cover internal and external surfaces Glands: - composed of secreting cells derived from epithelia Important Characteristics of Epithelia • Cells are closely packed together • A free(Apical) surface is exposed to the environment or to internal cavities • Cells are attached to a basement membrane • Lacks blood vessels(avascular) • Cells are continually replaced & regenerated Functions of Epithelia • Physical protection • Permeability control • Sensation trigger • Specialized secretions Gland Cells • Gland cells produce secretions Two Classes of Glandular Secretion: • Exocrine secretion- Secretion onto a body surface • Ex: digestive enzymes in digestive tract, perspiration on skin • Endocrine secretion- Secretion (of hormones) into neighboring tissues and blood • Ex: pancreas, thyroid, pituitary gland Intercellular Connections Epithelial cells are firmly attached to the basement membrane and to one another Epithelial cells are held together by CAMs(cell adhesion molecules) and a thin layer of intercellular cement Cell junctions: attachment sites between cells • Tight junctions- many attachments between cells using membrane proteins • Gap junctions- several attachments between cells using transport proteins • Desmosomes- attachment between cells using CAMs Intercellular Connections The Epithelial Surface The apical surface of epithelial cells has specialized structures Microvilli: Abundant on transport cells • Dramatically increase surface area • Found in intestinal lining, kidney tubules Cilia: • Beat in coordinated fashion • Move fluid along surface • Found in airways, oviduct The Surfaces of Epithelial Cells The Basement Membrane The basement membrane is an area between the epithelium and connective tissue - Provides strength and helps in resisting distortion - Prevents proteins & large molecules from entering the epithelium Classifying Epithelia Epithelium cells are classified by the # of layers and shape of cells • Number of layers • Simple (one cell thick) • Stratified (multiple cells thick) • Cell shape • Squamous (flat) • Cuboidal (cubic) • Columnar (tall columns) Epithelial Tissue Cell Layers Simple Epithelium: - a single layer of cells covering basement membrane - line internal compartments and passageways - found where secretion and absorption occurs Ex: lungs, digestive tract, urinary tract Cell Layers Stratified Epithelium: - provides greater protection from several layers of cells - found in areas of chemical and physical stress Ex: surface of skin, mouth, anus Epithelial Tissue Simple Squamous Epithelium Epithelial Tissue Simple Cuboidal Epithelium Epithelial Tissue Simple Columnar Epithelium Epithelial Tissue Pseudostratified Ciliated Columnar Epithelial Tissue Transitional Epithelium Epithelial Tissue Stratified Squamous Epithelium Glandular Epithelia Exocrine Glands: secrete products through ducts(tubes) onto an external or internal surface ex: salivary glands, mammary glands, sweat glands(sebaceous glands) Endocrine Glands: secrete hormones directly into the blood or tissue fluids ex: pituitary, thyroid Modes of Secretion: • Merocrine- secretion via exocytosis • Apocrine- shed a portion of the cell • Holocrine- burst of entire cell contents Mechanisms of Glandular Secretion Figure 4-6 Connective Tissues - Connective tissues are the most diverse tissue in the body in form and function Connective Tissues Components: • Specialized cells • Extracellular matrix(protein fibers) • Ground Substance Fluid Functions of Connective Tissue • • • • • • Structural framework Fluid and solute transport Physical protection Tissue interconnection Fat storage Microorganism defense Classifying Connective Tissues Connective Tissue Propertendons, ligaments, and fatty tissue Fluid Connective Tissuesblood & lymph Supporting Connective Tissuescartilage & bone Connective Tissues Major Types of Connective Tissue Connective Tissue Proper Components: Fibroblasts- produce and maintain connective tissue Macrophages- engulf damaged cells or pathogens in tissues Fat Cells(adipocytes)- store fluids & fatty acids Mast Cells- release chemicals to initiate the immune system after an injury or infection Connective Tissue Fibers Collagen fibers- long, straight, unbranched, strong & flexible Reticular fibers- thin fibers that form an interwoven framework in various organs Elastic fibers- contain elastin protein, are branched and waving, will return to their original length after stretching Cells and Fibers of Connective Tissue Proper Types of Connective Tissue Loose Connective Tissue: - least specialized type of connective tissue - forms a layer that separates the skin from underlying muscles - provides padding and allows for muscle movement Adipose Tissue(fat): - loose connective tissue containing large #’s of fat cells Dense Connective Tissue: - consists mostly of collagen fibers Tendons- cords of dense connective tissue connecting muscle to bone Ligaments- connect bone to bone, can stretch a little Connective Tissues Loose Connective Tissue Connective Tissues Adipose Tissue Connective Tissues Dense Connective Tissues Fluid Connective Tissues Blood: the watery matrix in blood is called plasma Plasma- contains RBC’s, WBC’s, platelets, proteins, carbs. & fats RBC’s- make up 50% of blood volume - carry oxygen from lungs to cells WBC’s- support the immune system Platelets- function in blood clotting Supporting Connective Tissue - Provides a framework that supports the rest of the body Cartilage: a firm gel containing embedded fibers Condrocytes- cells found in cartilage matrix * there are no blood vessels in cartilage Perichondrium- covering on outer surface of cartilage Cartilage Types of Cartilage: Hyaline Cartilage- found in joints Elastic Cartilage- ear Fibrocartilage- between vertebrae Connective Tissues Hyaline Cartilage Connective Tissues Elastic Cartilage Connective Tissues Fibrocartilage Bone (Osseous Tissue) Bone is composed of hard calcium deposits & collagen fibers Osteocytes- bone cells Canaliculi- canals in bone that transmit nutrients Periostenum- outer covering of bone Connective Tissues Bone Membranes Properties of Membranes • Barrier or interface that separate epithelial and connective tissue • Cover and protect organs Membranes Types of Membranes • Mucous • Lines cavities that connect to exterior • Mucus moistens surface • Examples: oral cavity, airways Serous • Line internal cavities • Watery fluid moistens surface • Example: peritoneal membrane Membranes Types of Membranes (continued) • Cutaneous • Covers body surface • Dry surface waterproofs the body • Example: the skin • Synovial • Lines joints • Secretes slippery synovial fluid • Lubricates joints • Examples: knee, elbow Membranes Muscle Tissue Properties of Muscle Tissue • Capable of contraction • Contraction involves interaction between filaments of actin and myosin found in the cytoskeleton of muscle cells • Three types of muscle tissue: • Skeletal muscle • Cardiac muscle • Smooth muscle Muscle Tissue Skeletal Muscle Tissue • Contains elongated cells (fibers) • Fibers tied together by loose connective tissue • Possesses microscopic striations • Contains many nuclei • Controlled by voluntary nervous system • Moves and stabilizes the skeleton Muscle Tissue Skeletal Muscle Tissue Muscle Tissue Cardiac Muscle Tissue • • • • • • • Only in heart Short, branched fibers Single nucleus Striated(striped) Involuntary contraction Blood circulation Blood pressure Muscle Tissue Cardiac Muscle Tissue Muscle Tissue Smooth Muscle Tissue • Short, tapering cells • No striations • Involuntary contraction • Blood vessels • Urinary bladder • Digestive organs • Uterus Muscle Tissue Smooth Muscle Tissue Neural Tissue Properties of Neural Tissue • Conduct electrical impulses • Transfer, process, and store information • Comprises neurons and neuroglia • Concentrated in the brain and spinal cord Neural Tissue Neurons • Dendrites • Information entry • Cell body • Information integration • Axon (nerve fibers) • Information transmission • Synaptic terminals • Information transfer Neural Tissue Neuroglia • • • • • Several types of neuroglia Provide physical support Maintain extracellular chemistry Supply nutrients Defend against infection Neural Tissue Tissue Injuries and Repair • An injury harms multiple tissues simultaneously • Tissues make coordinated response • Responses restore homeostasis • Two response types • Inflammation • Restoration Tissues and Aging Tissues Change with Age • • • • • Healing slows Epithelia become thinner Connective tissues become more fragile Bones weaken, become brittle Neuron and muscle fiber losses accumulate • Lifestyle interventions slow decline Tissues and Aging Aging and Cancer Incidence • Cancer risk rises with age • After heart disease, cancer second leading cause of death • Smoking linked to 40% of cancers • 75% caused by environment END OF CHAPTER 4 NOTES!!!
