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Transcript
Tissues: Living Communities Chapter 4 Introduction • Since cells are differentiated, they have lost ability to perform all metabolic functions required to sustain life as an isolated entity. • Cells exist in cooperative communities in multicellular organisms • Cells of similar type and function cluster together to form tissues. Classification of Tissues • Epithelial tissue • Covers and lines • Connective tissue • Provides support • Muscle tissue • Enables movement • Nervous tissue • Controls work Classification continued • Most organs contain all 4 tissue types. • The study of microscopic structures of tissues and organs is called histology or microscopic anatomy. • What is gross anatomy? Epithelial Tissue • Composed of sheets of cells that cover and line other tissues. • Bladder, mouth, blood vessels, thorax, etc. • Have an exposed surface that affords access to the surrounding environment or to the inner openings of chambers and ducts. • Acts as interface layer that separates and defines the beginning and ending of different types of tissues. Epithelial functions • • • • Acts as protection for underlying tissues Filter of biochemical substances May be absorptive May play an important role in sensory input • Secretion and excretion of biochemical substances • Epithelia that do this are called glandular epithelia • Individual glandular epithelia are goblet cells. Characteristics of Epithelia • Organized into tightly packed groups that form sheets of tissue. • Can be composed of single layer or multiple layers depending on location. • Epithelial cells share the following characteristics: • Polar - Each epithelial cell has an apical surface and a basal surface • Apical surface faces the lumen or body cavity • Basal surface faces the underlying connective tissue • Lateral surfaces are connected to neighboring cells by junctional complexes • Epithelial cells are avascular • Most epithelial cells are innervated Epithelial Tissue: Cellular Attachments • Epithelial cells are held together in many ways • Between the cell membranes of adjacent cells are channels that carry nutrients to the cells and waste away • Junctional Complexes – specialized attachments between epithelial cells • 3 major types: • Desmosomes • Welded plaque • Tough, resist tension and stretching (like Velcro) • Skin, heart, uterus • Gap junctions • Cytoplasm continuous • Exchange ions, nutrients – quickly transmit signals through connexons • Cardiac, smooth muscles • Tight junctions • Nothing can penetrate • Prevent leakage Epithelial Cells: Basement Membrane • Foundation of epithelial cells • Meshwork of fibers that cements epithelial cell to underlying connective tissue (CT) • Also called basal lamina • Varies in thickness • Where might thickness vary? • Helps prevent cell from being torn off by intraluminal pressures • Acts as a partial barrier between epithelial cell and underlying CT – substances have to travel through basement membrane to get in and out of epithelial cells. Surface Specialization • Surfaces vary depending on location in body and function • May be smooth or contain microvilli-fingerlike projections, or cilia-hairs • If the cell contains microvilli, it is said to have a brush border. • Brush border helps to increase surface area, which aids in absorption. (can add up to 20 times of surface area). • Skin may have keratin-waterproof substance • Keratin may accumulate as cell matures and moves from basal layer to superficial layer of integument. Classifications of Epithelia • Characterized by 3 characteristics • Number of layers of cells • Single layer is called simple • Found in protected parts of body because provide minimal protection to underlying structures • More than one layer is called stratified. • Thicker and stronger and are on parts of body that are subjected to mechanical or chemical stress. • Shape of cells • Based on shape that is on exposed or luminal surface • Squamous, cuboidal, and columnar • Presence of surface specializations • Keratinized, ciliated, etc. Simple Squamous Epithelium • Fragile and thin • Found lining surfaces involved in the passage of either gas or liquid (lining of lungs, kidneys) • Flat and smooth • Mesothelium – lining of chest (pleura), abdomen (peritoneum), and pericardium • Endothelium – lining of blood vessels Simple Cuboidal Epithelium • Single layer of cube-shaped cells • Round, dark-staining nuclei aligned in a single row • Occurs in areas of the body where secretion and absorption take place • Surface of ovaries, glands, lining of ducts of liver, kidneys, pancreas Simple Columnar Epithelium • Elongated and closely packed together - thicker • Nuclei aligned in a row at the base of the cell near the basement membrane • Line the GI tract from stomach to rectum • absorptive cell- apical surface is blanketed by dense microvilli that maximize absorption by increasing surface contact with nutrient-filled lumen. • goblet cell- manufacture and store mucus for lubrication • Found in many excretory ducts Stratified Squamous Epithelium • Multilayered • Occur in areas of the body subject to mechanical and chemical stresses • Mouth, esophagus, vagina, rectum • Continually being worn away or sheared off • Replaced by cells from a deeper layer Stratified Cuboidal Epithelium • Usually two layers of cuboidal cells • Found primarily along large excretory ducts • Salivary glands, mammary glands, sweat glands Stratified Columnar Epithelium • Found only in select parts of the respiratory, digestive, reproductive systems and along some excretory ducts • Rare • Function in secretion and protection Pseudostratified Columnar Epithelium • “False” stratified – truly simple • Cell nuclei are found at different levels across the length of the tissue • Some cells do not reach luminal surface but all attach to basement membrane. • Usually ciliated • Found in respiratory tract and in portions of male reproductive tract • trachea Transitional Epithelium • Stratified epithelium • basal layer of cuboidal or columnar cells • superficial layer of cuboidal or squamous cells • Ability to stretch - found in areas where changes in volume occur • Bladder, ureters, urethra • As epithelia stretches, layers often thin depending on how much volume is present • Also form a leak-proof barrier Glandular Epithelia • • • Gland- a cell or group of cells that have ability to manufacture and discharge a secretion. Secretions- specialized protein molecules that are produced in the RER, packaged by the golgi and discharged from the cell. Glands can be organized by factors: • Presence or absence of ducts • Endocrine vs. Exocrine • Number of cells that compose them • Unicellular vs multicellular • Shape of secreting ducts • Simple or compound • Complexity of glandular structure • Tubular, acinar, tubuloacinar • Type of secretion made • Mucoid or serous • Manner in which secretion is stored and discharged • Merocrine, apocrine, or holocrine Endocrine Glands • No ducts • Blood stream delivers secretions to entire body • Secrete hormones • Regulate body functions (growth, maturity, sex cycle) • Part of Endocrine System Exocrine Glands • Contain ducts (except for Goblet cells) • Have local effect • Salivary • Pancreas, liver (digestive enzymes) • Musk (scent) • Sweat • Anal (scent glands) Unicellular Exocrine Gland: Goblet Cell • Ductless • Opens into GI, respiratory tracts, conjunctiva • Composed of modified columnar epithelial cell • Secretes mucin: mixed with water → mucus Multicellular Exocrine Glands • Contains: • 1) secretory unit • Secretory unit usually surrounded by connective tissue rich in blood vessels and nerve fibers • 2) a duct • May be surrounded by myoepithelial cells that assist with the discharge of secretions into the glandular duct Classification of Multicellular Exocrine Glands: Shape • Based on shape and number of tubes Classification of Exocrine Glands: Manner of secretion • Merocrine • glands package their secretions and release them via exocytosis as they are manufactured • Majority of glands • (ex: pancreas, sweat, salivary) • Apocrine • glands store their secretions and then release the top part (apex) of the cell into the duct system • (ex: mammary, some sweat) • Holocrine • glands store their secretions and then release the entire contents of the cell • (ex: sebaceous) Classification of Exocrine Glands:Type of Secretions Produced Type of secretion produced • Serous secretions • Watery • Contain a high concentration of enzymes • Pancreatic secretion • Mucous secretions • Thick, viscous • Mucus membranes (GI, resp) • Composed of glycoproteins • Mixed exocrine glands contain both mucous and serous components Connective Tissue • • • • • Found everywhere in the body and represents most abundant tissue by weight. Some systems are almost exclusively composed of connective tissue • Skeletal, integumentary • Appearance varies. Is derived from mesoderm, and composed of nonliving extracellular matrix- matrix surrounds and separates the cells providing important structural and nutritional support to epithelial cells. Is combination of extracellular fibers and ground substance. Form and function may be different. • Reserve for energy • Protection • Provides framework of structural support Is vascularized. • Level of vascularity varies among connective tissue type. Connective Tissue Components • All connective tissue is composed of distinct components • 1. Extracellular fibers • Collagenous • Reticular • Elastic • 2. Ground substance • 3. Cells • Fixed cells • Fibroblasts • Adipocytes (fat cells) • Reticular cells • Wandering cells • Mast cells • Leukocytes (white blood cells) • Macrophages (fixed and wandering) Connective Tissue Components Connective Tissue Components: Ground Substance • An amorphous, homogenous material that ranges from liquid to gel to solid. • Composed of glycoproteins called glycosaminolglycans (GAGs) • Is medium through which cells exchange nutrients and waste with the bloodstream. • Acts as shock absorbing cushion and helps to protect underlying delicate cells. • Serves as obstacle for invading microorganisms. Fibers of Connective Tissue • Collagenous: • Strong and thick. • Composed of collagen. • Organized into bundles • Found in tendons and ligaments that are continuously being pulled and stretched. • Sometimes called white fibers • Density and arrangement can vary. • Loose to dense. Fibers of Connective Tissue • Reticular: • Composed of collagen, but are not thick • Thin and delicate and branched into complicated networks. • Form support for around other cellular organs like endocrine glands. • Elastic: • Composed primarily of elastin. • Are branched to form networks • Lack tensile strength of collagenous fibers. • Can stretch and contract. • Found in vocal cords, lungs, blood vessles. • May be referred to as yellow fibers. Major Cell Types of Connective Tissue • Fixed Cells: • Remain in the connective tissue • Fibroblast: secrete fibers and ground substance of particular matrix. • Can reproduce and are metabolically active. • Called based on location • Chondroblast, osteoblast, etc. • As mature, cells are less active and are called –cytes. Can revert back though if more matrix is needed. • Chondrocyte, osteocyte, fibrocyte • Fixed cells continued. • Adipose cells/Adipocytes: • Found throughout connective tissue • Form adipose tissue. • Filled with lipid or fat. • Reticular Cells: • Form net-like connections through cells • Involved in immune response and manufacture of reticular fibers. • Transient or Wandering Cells • Move in and out of connective tissue as needed. • Leukoctyes: white blood cells • Found in blood and move into connective tissue during periods of infection. • Important in immune function. • Mast cells: carry histamine and heparin which initiate inflammatory response when released into tissue • Usually found near blood stream where can mount response. • Wandering cells continued.. • Macrophages: phagocytotic scavengers that may be either fixed or transient in connective tissue. • Engulf microbes, dead cells and debris • What digests the cell? • Given different names depending on locatons • Kupffer cells, microglial cells, histiocytes. Types of Connective Tissue • Categorized as: • Loose • Areolar • Adipose • Reticular • Dense • Regular • Dense irregular • Elastic Areolar Tissue • Most common type of connective tissue • Found everywhere in body • Acts to support and cushion organs and other delicate structures. • Moderately elastic but tears easily compared to other connective tissue. • Has “open” spaces • Filling of spaces during trauma is called edema • Pitting edema- when tissue leaves pits in tissue after being compressed. • Viscous ground substance Adipose Tissue • • • • Commonly known as fat. Part of areolar tissue in which adipocytes dominate. Highly vascularized Cells expand based on amount of lipid being stored. • Important energy store. • May be classified as: • White: • Found throughout body • Brown: • Found in newborns and hibernating animals • Specialized form plays role in temperature regulation Reticular Connective Tissue • Resembles areolar connective tissue but only contains reticular fibers • Found in limited sites of body Dense Regular Connective Tissue • Tightly paced, parallel collagen fibers • Tremendous tensile strength in one direction. • Makes up tendons and ligaments Dense Irregular Connective Tissue • Collagen fibers in thicker bundles than those in regular connective tissue. • Can withstand force from many different directions. • Found in dermis and fibrous coverings. • Forms tough capsule of joints. Elastic Connective Tissue • High concentration of elastic fibers that is extremely flexible. • Found in few regions of body. • Stomach, large airways, bladder, etc. Specialized Connective Tissues • Cartilage • Hyaline Cartilage • Elastic Cartilage • Fibrocartilage • Bone • Blood Cartilage • Tough, specialized connective tissue. • May be called gristle. • More rigid than dense connective tissue, more flexible than bone. • Does not contain nerves. • Can take a great deal of compression. • Composed of cells (chondrocytes) and matrix. • 3 types of cartilage: • Hyaline cartilage • Elastic Cartilage • Fibrocartilage Types of Cartilage • Hyaline Cartilage • Most common type of cartilage found in body. • Found as articular cartilage at end of long bones and joints and connects ribs to the sternum. • Most rigid type of cartilage. • Elastic Cartilage • Similar to hyaline cartilage but contains elastic fibers • Can withstand repeated bending. • Found in pinnae Types of cartilage continued • Fibrocartilage • Found merged with hyaline cartilage and dense connective tissue. • Found between vertebrae and spine Bone • Also called osseous connective tissue • Hardest and most rigid type of connective tissue • Is well vascularized • Provides protection. • Structure • Ground matrix - osteoid – calcium phosphate and collagen fibers • Haversian canals – channels in bone that carry blood supply and nerves • Periosteum – fibrous membrane that covers the bone Blood • Most atypical type of connective tissue. • Composed of specialized cells: • Erythrocytes (red blood cells) • Leukocytes (white blood cells) • Thrombocytes (platelets) Membranes • Epithelial and connective tissue may be linked to form membranes. • Are thin, protective layers that line body cavities, separate organs and cover surfaces. • Four common epithelial membranes are: • Mucous • Serous • Cutaneous • Synovial Mucous Membranes • Always found lining organs that have connection to outside environment. • Esophagus, mouth, colon, etc. • Produces protective and lubricating mucous • Play role in monitoring and controlling what enters into body and form barrier. • How are mucous membranes important to us? • CRT • Are very absorptive • Buprenex Serous Membranes • Also called Serosa • Line walls and cover organs that fill closed body cavities • Characterized by continous sheet that is doubled over to form two layers with a narrow space. • Remember parietal vs. visceral? • Fluid is thin and watery (a transudate). • Large amount of fluid is called effusion. • Fluid in abdomen is termed ascites. • Adhesions are connections between parietal and visceral layers. Cutaneous Membranes • The integument • What else is this called? • Perpetually exposed to environment. • Composed of keratinized stratified squamous epithelium called epidermis • Epidermis is attached to underlying Dermis. Synovial Membranes • Line the cavities of joints • Contain no epithelium • Manufacture synovial fluid that fills the joint spaces and reduces friction and abrasion at the ends of bones. Muscle Tissue • Uniquely designed for contraction. • Composed of myosin and actin • Three types of muscle tissue: • Skeletal • Smooth • Cardiac Skeletal Muscle • Large and numerous cells • Usually controlled by conscience thought therefore is voluntary. • Are striated or striped • Held together by loose connective tissue. Smooth Muscle • Composed of small spindle-shape cells that lack striation or bands and appear smooth. • Can not be consciously controlled. • Found in walls of hollow organs Cardiac Muscle • Possesses ability to contract even when neural input has been altered. • Exists only in the heart. • Completely involuntary. • Cells are smooth and only contain one nucleus • Branches to form complex network. • Are striated and connected to other cells via an intercalated disk • Contract at set rate. Nervous Tissue • • • Neural tissue is designed to send and receive electrical and chemical signals. Found in brain, spinal cord, and peripheral nerves Composed of two cell types • Neurons • Longest cells in body. • Composed of three parts • Cell body (perikaryon) • Cytoplasmic extensions (dendrites) • Long single extension (axon) • Forms connections with many other tissues • Sensitive to electrical and chemical changes • Neuroglial cells • Found in greater numbers than neurons • Do not transmit impulses • Are supportive to the neurons Tissue Healing and Repair • Body’s initial response to injury is inflammation. • Repair includes organization of granulation tissue and regeneration of lost tissue or formation of scar tissue • Inflammation: • Area generally becomes swollen, red and hot. • Sometimes is decreased function in that part. • This isolates area to prevent further damage • Inflammation is not same as infection. Steps in the Process of Inflammation • 1. Inflammation begins and then vasodilation. Blood flow and oxygen and nutrient supply is increased to area. • 2. Swelling occurs • 3. Clot formation takes place • 4. Debris is removed by phagocytic cells • 5. Histamine and Heparin help to reduce swelling and heat. Organization: The formation of Granulation Tissue • New tissue is formed called granulation tissue • Composed of collagen fibers that has been manufactured by fibroblasts. • If granulation tissue becomes too thick, will be called proud flesh. • Granulation tissue is slowly replaced by fibrous scar tissue • Helps to pull wound closed. • Is less flexible than normal tissue Proud Flesh Classifications of Wound Healing • First intention: • Wound edges are held closed • Usually by sutures • Skin forms a primary union without formation of granulation tissue or significant scarring • Second Intention: • Edges of wound separated • Granulation tissue forms to close gap; scarring results • Third Intention: • Contaminated wound left open until contamination is reduced and inflammation subsides; later closed by first intention; also called delayed primary closure • http://www.youtube.com/watch?v=CjTQy6 WJFOs • http://www.youtube.com/watch?v=6wFIVnl eDgk&feature=related