Download Tissues: The Living Fabric

Tissues: The Living Fabric
 To optimize functions, body cells are organized into tissues
 Four basic tissue types exist in humans
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Epithelial tissue
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Connective tissue
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Muscle tissue
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Nervous tissue
 Epithelial tissue
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Lining and covering epithelium
 Cover internal or external surfaces (all exposed body surfaces)
 Located on the skin, GIT, respiratory tract
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Glandular epithelium
 Specialized secretory structures
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Functions
 Protection, absorption, filtration, excretion and secretion
 Special Characteristics of Epithelium
 Specialized contacts
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Cells are held closely together forming continuous sheets
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Adjacent cells are tightly bound to each other via specialized contacts (desmosomes and
tight junctions)
 Polarity
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An apical surface and a basal surface is present in all epithelia
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The apical surface is exposed to the body exterior or cavity of an internal organ
 Bears cilia or microvilli
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The basal surface is attached to the underlying tissue
 Supported by connective tissue
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Epithelial tissue sheets rest on an underlying layer of connective tissue that also provides
support
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The basal lamina of the epithelial tissue and the reticular lamina of the connective tissue
join together to form a basement membrane
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The basement membrane is the interface between the epithelial tissue and the connective
tissue
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Special Characteristics of Epithelium
 Avascularity
 Epithelia do not contain blood vessels but is innervated
 Nutrients are obtained from the exposed or underlying surface
 Regeneration
 Epithelial cells are exposed to damage
 They have the ability to regenerate and replace the cells that slough off the
surface
Classification of Epithelia
 Shape
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Squamous
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Cuboidal
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Columnar
 Degree of layering
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Simple
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Stratified
 Simple epithelia
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Consist of a single cell layer
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Line surfaces used for exchange
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Located in the GIT, respiratory tract, inner surface of blood vessels and heart chambers
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Classification of Epithelia
 Stratified epithelia
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Several layer of cells (additional protection)
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Different cell layers may have different cell types
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Epithelia is named with respect to the cells of the apical layer
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Found on the surface of the skin and the lining of the mouth
Simple Squamous Epithelia
 Description
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Flat thin cells with very little cytoplasm shaped like fried egg
 Location
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Found lining the alveoli and blood vessels (endothelium), lymph vessels, and ventral
body cavity (mesothelium)
 Function
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Passage of materials by diffusion and filtration in areas where protection is not a priority
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Secretes lubricating substances in serosae
 Simple Cuboidal Epithelium
 Description
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Single layer of cubelike cells with large spherical centrally placed nuclei
 Function
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Secretion and absorption
 Location
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Kidney tubules
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Surface of the ovary
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Ducts and secretory parts of small glands
Simple Columnar Epithelium
 Description
 Single layer of tall cells with round nuclei
 Apical surfaces may contain microvilli
 Tissue may contain goblet cells (mucus- secreting cells)
 Function
 Absorption, secretion
 Location
 GIT (from stomach to anal canal)
 Pseudostratified Columnar Epithelium
 Description
 Single layer of cell with differing heights (false stratification)
 May contain goblet cells and bear cilia
 Function
 Secretion (primarily mucus)
 Mucus propulsion by ciliary action
 Location
 Nasal cavity, trachea and bronchi
 Stratified Squamous Epithelia
 Description
 Several call layers
 Basal cells are cuboidal or columnar
 Surface cells are squamous
 Keratinized type has the protein keratin that helps in preventing water loss
 Function
 Provides protection to underlying areas subject to abrasion
 Location
Nonkeratinized type
Esophageal lining, mouth, vagina
Keratinized
Epidermis of the skin
Transitional Epithelium
 Description
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Basal cells are cuboidal or columnar
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Surface cells are dome-shaped or squamouslike depending on the degree of stretch of the
organ
 Function
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Allows distention of urinary organs
 Location
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Ureters, bladder and parts of urethra
 Glandular Epithelia
 Glands make and secrete watery substances referred to as secretions
 Two types exist
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Endocrine (ductless) glands
 Release secretions directly into the blood stream or lymph
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Exocrine glands (glands have ducts)
 Release secretions onto body surface or into body cavities
 Classification of Exocrine Glands
 Unicellular
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Goblet cell
 Multicellular
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Have a secretory portion (acinus) and duct
 Structurally classified as simple (straight duct) or compound (branched
duct)
 Classified based on secretory units as tubular (tube-shaped acinus), alveolar
(flasklike acinus), and tubuloalveolar if both are present.
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Figure 4.4b Goblet cell (unicellular exocrine gland).
 Multicellular
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Classified based on secretory mode as:
 Merocrine – secretes by exocytosis
 Holocrine - secretory cells rupture to release secretion
 Apocrine – apical portion of secretory cell ruptures to release secretion
 Connective Tissue
 Most abundant and widely distributed tissue type.
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Four classes exist.
 Common characteristics
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Common origin
 Develop from embryonic tissue called mesenchyme
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Degree of vascularity
 May be avascular, mildly vascularized or richly vascularized
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Extracellular matrix
 Non-living material surrounding cells
 Composed of ground substance (IF, cell adhesion molecules, and proteoglycans)
and fibers
 Connective Tissue Cells
 Adipocytes – Store fat
 Macrophages – Phagocytes
 Fibroblasts - Produce fiber
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“-blast” = actively mitotic immature cell
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“-cyte” = mature cell
 WBCs – Immune cells
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Plasma cells – Produce antibodies
 Mast cells – Produce histamine and heparin
 Connective Tissue Fibers
 Three types of fibers exist
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Collagen fibers (white fibers)
 Most abundant and provides high tensile strength
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Found in tendons and ligaments
Reticular fibers
 Network of short, highly branched, collagenous fibers
 Used to support organs
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Elastic fibers
 Long, thin, elastin fibers that stretch
 Types of Connective Tissue

Connective tissue proper (excludes bone, cartilage and blood)
 Two subclasses exist
 Lose connective tissue
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(Areolar tissue)

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Found throughout the body acting as packing material between tissues
Adipose tissue
 Stores fat
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Reticular tissue
 Found in the lymphatic system where it provides support to the cells of the
immune system
 Dense connective tissue
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Dense regular
 Includes tendons and ligaments
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Dense irregular
 Found in skin, joint capsule and surrounding various organs

Cartilage
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Properties are intermediate between dense connective tissue and bone
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Primary cells are chondrocytes
 Hyaline cartilage
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Most common
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Matrix has closely packed collagen fibers for strength and flexibility
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Found between ribs and the sternum, trachea and articular surfaces of most joints
 Elastic cartilage
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Contains lots of elastic fibers
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Found in the outer ear, epiglottis and larynx
 Fibrocartilage
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Densely packed with collagen
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Very tough
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Found between the vertebrae (intervertebral discs) and between the pubic bones (pubic
symphysis)
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Covering and Lining Membranes
 Membranes are formed by epithelial and connective tissues
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Cutaneous membranes
 Skin
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Mucous membranes (mucosae)
 GIT, respiratory, reproductive, urinary tracts
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Serous membranes
 Pleura, peritoneum and pericardium
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Synovial membranes
 Joints
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Note that synovial membranes are NOT epithelial membranes and are
solely made up of connective tissue
 Tissue Repair
 Tissue injury results in body damage and increased susceptibility to pathogenic invasion
 Tissue injury stimulates two major body responses
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Inflammatory response
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Immune response
 Tissue Response
 Inflammatory response
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Remove harmful agents
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Prevent further injury
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Restore tissue health
 Immune response
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Specific and deadly attacks against invading pathogens
 Steps of tissue repair
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Inflammation
 Chemicals (histamines) are released from damaged tissue and they cause
capillaries to dilate and leak
 Fluid enters injury site with more chemicals (clotting factors and antibodies)
 WBCs enter site of injury
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Organization
 New capillaries proliferate and restore proper blood flow to injured tissue
 Clot is replaced by granulation tissue
 Debris is phagocytized
 Fibroblasts produce collagen fibers to help strengthen injured tissue
 Epithelia regenerate
 Regeneration and fibrosis
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Scab detaches
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Regeneration is replacement of damaged tissue with new tissue
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Fibrosis is the proliferation of connective tissue to form scar
 Fibrosis may occur depending on the type and severity of the injury
 Epithelial tissue and bone tissue are good at regenerating without fibrosis
 Dense regular connective tissue and cartilage have considerably less regenerative
properties
 Cardiac tissue and nervous tissue have essentially no functional regenerative
capacity
Name the tissue
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Amorphous matrix that appears glassy
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Multiple layers of cells stacked in layers with the topmost layer consisting of flat cell
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Allow stretching of the organ in which it is found
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Can resist tensile strain or stress from multiple directions
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Posses cilia and goblet cells
 How does the structure of each tissue relate to its function?
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Simple squamous epithelium
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Dense regular connective tissue
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Stratified squamous epithelium (keratinized type)
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Simple columnar epithelium
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Fibrocartilage
 What is the level of structural organization?
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Collagen
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Elastin
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Lymphocytes
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Adipocytes
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Chondroblast
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Fibrocyte