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Chapter 4 The Tissue Level of Organization Copyright 2009, John Wiley & Sons, Inc.
What is a Tissue? n A tissue is a group of cells q q n n n Common embryonic origin Function together to carry out specialized activities Hard (bone), semisolid (fat), or liquid (blood) Histology is the science that deals with the study of tissues. Pathologist specialized in laboratory studies of cells and tissue for diagnoses Copyright 2009, John Wiley & Sons, Inc.
4 Types of Tissues q q Epithelial n Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands Connective n Protects, supports, and binds organs. n Stores energy as fat, provides immunity Muscular n Generates the physical force needed to make body structures move and generate body heat Nervous n Detect changes in body and responds by generating nerve impulses Copyright 2009, John Wiley & Sons, Inc.
Development of Tissues n Tissues of the body develop from three primary germ layers: n Ectoderm, Endoderm, and Mesoderm q Epithelial tissues develop from all three germ layers q All connective tissue and most muscle tissues drive from mesoderm q Nervous tissue develops from ectoderm Copyright 2009, John Wiley & Sons, Inc.
Cell Junctions n Contact points between the plasma membranes of tissue cells q 5 most common types: n n n Tight junctions Adherens junctions Desmosomes Hemidesmosomes Gap junctions Copyright 2009, John Wiley & Sons, Inc.
Tight Junctions n Web-like strands of transmembrane proteins q q Fuse cells together Seal off passageways between adjacent cells n n Common in epithelial tissues of the stomach, intestines, and urinary bladder Help to retard the passage of substances between cells and leaking into the blood or surrounding tissues Copyright 2009, John Wiley & Sons, Inc.
Adherens Junctions n Dense layer of proteins called plaque q q Resist separation of cells during contractile activities Located inside of the plasma membrane attached to both membrane proteins and microfilaments of the cytoskeleton Transmembrane glycoproteins called cadherins insert into the plaque and join cells In epithelial cells, adhesion belts encircle the cell Copyright 2009, John Wiley & Sons, Inc.
Desmosomes n Contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together q q Desmosome plaque attaches to intermediate filaments that contain protein keratin Prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction Copyright 2009, John Wiley & Sons, Inc.
Hemidesmosomes n Resemble half of a desmosome q q q Do not link adjacent cells but anchor cells to the basement membrane Contains transmembrane glycoprotein integrin Integrins attach to intermediate filaments and the protein laminin present in the basement membrane Copyright 2009, John Wiley & Sons, Inc.
Gap Junctions n Connect neighboring cells via tiny fluid-filled tunnels called connexons q q Contain membrane proteins called connexins Plasma membranes of gap junctions are separated by a very narrow intercellular gap (space) n n Communication of cells within a tissue Ions, nutrients, waste, chemical and electrical signals travel through the connexons from one cell to another Copyright 2009, John Wiley & Sons, Inc.
Epithelial Tissues n Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers q q q n Closely packed and held tightly together Covering and lining of the body Free surface 3 major functions: q q q Selective barrier that regulates the movement of materials in and out of the body Secretory surfaces that release products onto the free surface Protective surfaces against the environment Copyright 2009, John Wiley & Sons, Inc.
General Features of Epithelial Cells n Surfaces of epithelial cells differ in structure and have specialized functions q Apical (free) surface n q Lateral surfaces n q Faces the body surface, body cavity, lumen, or duct Faces adjacent cells Basal surface n Opposite of apical layer and adhere to extracellular materials Copyright 2009, John Wiley & Sons, Inc.
General Features of Epithelial Cells n Basement membrane q q Thin double extracellular layer that serves as the point of attachment and support for overlying epithelial tissue Basal lamina n n q Closer to and secreted by the epithelial cells Contains laminin, collagen, glycoproteins, and proteoglycans Reticular lamina n n Closer to the underlying connective tissue Contains collagen secreted by the connective tissue cells Copyright 2009, John Wiley & Sons, Inc.
Epithelial Cells Copyright 2009, John Wiley & Sons, Inc.
Epithelial Tissues q q q n Own nerve supply Avascular or lacks its own blood supply Blood vessels in the connective tissue bring in nutrients and eliminate waste High rate of cell division for renew and repair Numerous roles in the body (i. e. protection and filtration) Covering and lining epithelium n n Outer covering of skin and some internal organs Glandular epithelium n Secreting portion of glands (thyroid, adrenal, and sweat glands) Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium n Normally classified according to: q q Arrangement of cells into layers Shapes of cells Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium n Arrangement of cells in layers q q Consist of one or more layers depending on function Simple epithelium n q Pseudostratified epithelium n n q Single layer of cells that function in diffusion, osmosis, filtration, secretion, or absorption Appear to have multiple layers because cell nuclei at different levels All cells do not reach the apical surface Stratified epithelium n Two or more layers of cells that protect underlying tissues in areas of wear and tear Copyright 2009, John Wiley & Sons, Inc.
Different Types of Covering and Lining Epithelium n Cells vary in shape depending on their function q Squamous n n q Thin cells, arranged like floor tiles Allows for rapid passage of substances Cuboidal n n n As tall as they are wide, shaped like cubes or hexagons May have microvilli Function in secretion or absorption Copyright 2009, John Wiley & Sons, Inc.
Different Types of Covering and Lining Epithelium q Columnar n n n q Much taller than they are wide, like columns May have cilia or microvilli Specialized function for secretion and absorption Transitional n n Cells change shape, transition for flat to cuboidal Organs such as urinary bladder stretch to larger size and collapse to a smaller size Copyright 2009, John Wiley & Sons, Inc.
Simple Epithelium q q Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium (nonciliated and ciliated) Pseudostratified columnar epithelium (nonciliated and cilated) Copyright 2009, John Wiley & Sons, Inc.
Simple squamous epithelium q Single layer of cells that resembles a tiled floor on the surface n q Nucleus is centrally located and appears flattened oval or sphere Found at sites for filtration or diffusion Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium n Endothelium q n Mesothelium q n The type of simple squamous that lines the heart, blood vessels, and lymphatic vessels The type of epithelial layer of serous membranes such as the pericardium, pleura, or peritoneum Unlike other epithelial tissue, Both are derived from embryonic mesoderm Copyright 2009, John Wiley & Sons, Inc.
Simple cuboidal epithelium q q Cuboidal shaped cells Cell nuclei round and centrally located Found in thyroid gland kidneys Functions in secretion and absorption Copyright 2009, John Wiley & Sons, Inc.
Simple columnar epithelium q q q Column shaped cells Oval nuclei at near base Nonciliated and ciliated Copyright 2009, John Wiley & Sons, Inc.
Nonciliated simple columnar epithelium q Contains columnar cells with microvilli at their apical surface and goblet cells q q Secreted mucus serves as lubricant for the lining of digestive, respiratory, reproductive and urinary tracts Also prevents the destruction of the stomach lining by acidic gastric juices Copyright 2009, John Wiley & Sons, Inc.
Ciliated simple columnar epithelium q Columnar epithelial cells with cilia at the apical surface n In respiratory tract, goblet cells are interspersed among ciliated columnar epithelia n Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing n Cilia also moves oocytes to the uterine tubes Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium n Pseudostratified columnar epithelium q q Appears to have several layers due to nuclei are various depths All cells are attached to the basement membrane in a single layer but some do not extend to the apical surface Ciliated cells secrete mucus and bear cilia Nonciliated cells lack cilia and goblet cells Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium Copyright 2009, John Wiley & Sons, Inc.
Stratified Epithelium n n Two or more layers of cells Specific kind of stratified epithelium depends on the shape of cells in the apical layer q q Stratified squamous epithelium Stratified cuboidal epithelium Stratified columunar epithelium Transitional epithelium Copyright 2009, John Wiley & Sons, Inc.
Stratified Squamous Epithelium q Several layers of cells that are flat in the apical layer n n q Keratinized form contain the fibrous protein keratin n q New cells are pushed up toward apical layer As cells move further from the blood supply they dehydrate, harden, and die Found in superficial layers of the skin Nonkeratinized form does not contain keratin n Found in mouth and esophagus Copyright 2009, John Wiley & Sons, Inc.
Stratified Cuboidal Epithelium q q q Fairly rare type of epithelium Apical layers are cuboidal Functions in protection Copyright 2009, John Wiley & Sons, Inc.
Stratified columnar epithelium q q Also very uncommon Columnar cells in apical layer only Basal layers has shorten, irregular shaped cells Functions in protection and secretion Copyright 2009, John Wiley & Sons, Inc.
Transitional Epithelium q q q Found only in the urinary system Variable appearance In relaxed state, cells appear cuboidal Upon stretching, cells become flattened and appear squamous Ideal for hollow structure subjected to expansion Copyright 2009, John Wiley & Sons, Inc.
Glandular Epithelium: Endocrine Glands q q Secretions, called hormones, diffuse directly into the bloodstream Function in maintaining homeostasis Copyright 2009, John Wiley & Sons, Inc.
Glandular Epithelium: Exocrine Glands q q Secrete products into ducts that empty onto the surfaces of epithelium Skin surface or lumen of a hollow organ Secretions of the exocrine gland include mucus, sweat, oil, earwax, saliva, and digestive enzymes Examples of glands include sudoriferous (sweat) glands Copyright 2009, John Wiley & Sons, Inc.
Structural Classification of Exocrine Glands n Multicellular glands are categorized according to two criteria: q q Ducts are branched or unbranched Shape of the secretory portion of the gland n n n Simple gland duct does not branch Compound gland duct branches Tubular glands have tubular secretory parts Acinar glands have rounded secretory parts Tubuloacinar glands have both tubular and rounded secretory parts Copyright 2009, John Wiley & Sons, Inc.
Structural Classification of Exocrine Glands Copyright 2009, John Wiley & Sons, Inc.
Functional Classification of Exocrine Glands SWEAT GLAND MAMMARY GLAND ZIT Copyright 2009, John Wiley & Sons, Inc.
Connective Tissue n n Most abundant and widely distributed tissues in the body Numerous functions q q q Binds tissues together Supports and strengthen tissue Protects and insulates internal organs Compartmentalize and transport Energy reserves and immune responses Copyright 2009, John Wiley & Sons, Inc.
Extracellular matrix of Connective Tissue n Extracellular matrix is the material located between the cells q n n Consist of protein fibers and ground substance Connective tissue is highly vascular Supplied with nerves q Exception is cartilage and tendon. Both have little or no blood supply and no nerves Copyright 2009, John Wiley & Sons, Inc.
Cells and Fibers in Connective Tissue Copyright 2009, John Wiley & Sons, Inc.
Connective Tissue Cells n n n Fibroblasts q Secrete fibers and components of ground substance Adipocytes (fat cells) q Store triglycerides (fat) Mast cells q Produce histamine White blood cells q Immune response q Neutrophil and Eosinophils Macrophages q Engulf bacteria and cellular debris by phagocytosis Plasma cells q Secrete antibodies Copyright 2009, John Wiley & Sons, Inc.
Connective Tissue Extracellular n Ground substance Matrix q Between cells and fibers n q q Fluid, semifluid, gelatinous, or calcified Functions to support and bind cells, store water, and allow exchange between blood and cells Complex combination of proteins and polysaccharides Fibers q q q Collagen fibers Elastic fibers Reticular fibers Copyright 2009, John Wiley & Sons, Inc.
Classification of Connective Tissues n Embryonic connective tissue q n Mesenchyme and mucous connective tissue Mature connective tissue q Loose connective tissue n q Dense connective tissue n q q Dense regular, dense irregular, and elastic Cartilage n q Areolar, adipose, and reticular Hyaline, fibrocartilage, and elastic cartilage Bone tissue Liquid connective tissue n Blood and lymph Copyright 2009, John Wiley & Sons, Inc.
Embryonic Connective Tissue q q Mesenchyme n Gives rise to all other connective tissues Mucous (Wharton’s Jelly) n Found in umbilical cord of the fetus Copyright 2009, John Wiley & Sons, Inc.
Loose Connective Tissue: Areolar Connective Tissue q q Most widely distributed in the body Contains several types of cells and all three fibers Copyright 2009, John Wiley & Sons, Inc.
Loose Connective Tissue: Adipose Tissue Contains adipocytes q q q Good for insulation and energy reserves White (common) and brown adipose tissue Copyright 2009, John Wiley & Sons, Inc.
Loose Connective Tissue: Reticular Connective Tissue q q Fine interlacing reticular fibers and cells Forms the stroma of liver, spleen, and lymph nodes Copyright 2009, John Wiley & Sons, Inc.
Dense Connective Tissue n Dense connective tissue q q n Contains numerous, thicker, and denser fibers Packed closely with fewer cells than loose connective tissue Dense regular connective tissue q q Bundles of collagen fibers are regularly arranged in parallel patterns for strength Tendons and most ligaments Copyright 2009, John Wiley & Sons, Inc.
Types of Mature Connective Tissue: Dense Irregular Collagen fibers are usually irregularly arranged Connective Tissue q q q Found where pulling forces are exerted in many directions Dermis of skin and heart Copyright 2009, John Wiley & Sons, Inc.
Dense Connective Tissue: Elastic Connective Tissue q q q Contain branching elastic fibers Strong and can recoil to original shape after stretching Lung tissue and arteries Copyright 2009, John Wiley & Sons, Inc.
Types of Mature Connective Tissue: Cartilage n Cartilage is a dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate q Chrondrocytes n q Pericondrium n n q Cartilage cells found in the spaces called lucunae Covering of dense irregular connective tissue that surrounds the cartilage Two layers: outer fibrous layer and inner cellular layer No blood vessels or nerves, except pericondrium Copyright 2009, John Wiley & Sons, Inc.
Hyaline cartilage q q q Most abundant cartilage in the body Surrounding by perichondrium (some exceptions like articular cartilage) Provide flexibility and support. Reduces friction Copyright 2009, John Wiley & Sons, Inc.
Fibrocartilage q q Chondrocytes are scattered among bundles of collagen fibers within the extracellular matrix Lack a perchondrium Strongest type of cartilage Found in intervertebral disc (between vertebrae) Copyright 2009, John Wiley & Sons, Inc.
Elastic Cartilage q q q Chrondrocytes are located within a threadlike network of elastic fibers Pericondrium is present Provides strength and elasticity Copyright 2009, John Wiley & Sons, Inc.
Repair and Growth of Cartilage n n n Cartilage grows slowly When injured or inflamed, repairs is slow due to its avascular nature. Two patterns of cartilage growth: q Interstitial growth n q Growth from within the tissue Appositional growth n Growth at the outer surface of the tissue Copyright 2009, John Wiley & Sons, Inc.
Bone tissue n n n Bones are organs composed of several different connective tissues: bone (osseous) tissue, periosteum, and endosteum. Compact or spongy Osteon or haversian system q Spongy bone lacks osteons. They have columns called trabeculae Copyright 2009, John Wiley & Sons, Inc.
Liquid Connective Tissue n Blood tissue q n Connective tissue with liquid extracellular matrix called blood plasma Lymph Copyright 2009, John Wiley & Sons, Inc.
Membranes Copyright 2009, John Wiley & Sons, Inc.
Epithelial Membranes n Mucous membranes (GOBLET CELLS) q q q Lines a body cavity that opens Directly to the exterior Epithelial layer is important for the body’s defense against pathogens Connective tissue layer is areolar connective tissue and is called lamina propria Copyright 2009, John Wiley & Sons, Inc.
Epithelial Membranes n Serous membranes or serosa q q Lines a body cavity that does not open directly to the exterior. Also covers the organs that lie within the cavity Consist of areolar connective tissue covered by mesothelium (simple squamous epithelium) that secrete a serous fluid for lubrication Copyright 2009, John Wiley & Sons, Inc.
Epithelial membranes: Mucous Membranes n n Membranes are flat sheets of pliable tissue that cover or line a part of the body Epithelial membranes are a combination of an epithelial layer and an underlying connective tissue layer q n Mucous, Serous, and Cutaneous membranes Synovial membranes q Lines joints and contains connective tissue but not epithelium Copyright 2009, John Wiley & Sons, Inc.
Muscular Tissue n Consists of elongated cells called muscle fibers or myocytes q q q Cells use ATP to generate force Several functions of muscle tissue Classified into 3 types: skeletal, cardiac, and smooth muscular tissue Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue q q Attached to bones of the skeleton Have striations Voluntary movement or contractions by conscious control Vary in length (up to 40 cm) and are roughly cylindrical in shape Copyright 2009, John Wiley & Sons, Inc.
Muscular Tissue n Cardiac muscle tissue q q q Have striations Involuntary movement or contraction is not consciously controlled Intercalated disc unique to cardiac muscle tissue Copyright 2009, John Wiley & Sons, Inc.
Smooth Muscle Tissue q Walls of hollow internal structures n q q Blood vessels, airways of lungs, stomach, and intestines Nonstriated Usually involuntary control Copyright 2009, John Wiley & Sons, Inc.
Nervous Tissue n Consists of two principle types of cells q Neurons or nerve cells q Neuroglia Copyright 2009, John Wiley & Sons, Inc.
Excitable Cells n n Neurons and muscle fibers Exhibit electrical excitability q q The ability to respond to certain stimuli by producing electrical signals such as action potentials Actions potentials propagate along a nerve or muscle plasma membrane to cause a response n n Release of neurotransmitters Muscle contraction Copyright 2009, John Wiley & Sons, Inc.
Tissue Repair: Restoring Homeostasis n When tissue damage is extensive both stroma and parenchymal cells are active in repair q q q n Fibroblast divide rapidly New collagen fibers are manufactured New blood capillaries supply materials for healing All of these process create an actively growing connective tissue called granulation tissue Copyright 2009, John Wiley & Sons, Inc.
Aging and Tissues n n n Tissue heal faster in young adults Surgery of a fetus normally leaves no scars Young tissues have a better nutritional state, blood supply, and higher metabolic rate Extracellular components also changes with age Changes in the body’s use of glucose, collagen, and elastic fibers contribute to the aging process Copyright 2009, John Wiley & Sons, Inc.
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