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Tissues Chapter 4 Tissues Chapter 4
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Tissues Tissues are groups of cells and extracellular material that perform specific functions. The four tissue types, in varying combinations, form all of the structures of the human body. Histology - The study of tissues
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Four Basic Tissue Types Epithelial Connective Muscular Neural (nervous) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Epithelial Tissue (epithelium) Characteristics Cells closely packed & attached to each other Apical cells exposed to external environment or internal surface Cells attached to connective tissue at basement membrane Avascular - Lack blood vessels Regenerates easily - cells continually replaced
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Epithelial Tissue Glandular - secretory structures derived from epithelia Endocrine glands - Secretion of product (hormones) into interstitial fluid and blood. e.g. – thyroid, pituitary Exocrine glands - Secretion of product onto a body surface. e.g. – sebaceous (oil), sudoriferous (sweat) Covering & lining epithelium - an avascular layer of cells that lines internal or external surfaces & covers organs within cavities; - always bound to CT creating an “epithelial membrane” Subtypes of epithelial tissue -
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Epithelial Membranes Epithelial tissue bound to connective tissue Connection of tissues occurs at the basement membrane - noncellular meshwork anchors basal cells Basement membrane creates a semi- permeable junction for diffusion of O 2, nutrients & wastes Epithelial Membranes
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Epithelial membranes Types of epithelial membranes: Mucous membranes (mucosa) Serous membranes (serosa) Cutaneous membrane (skin)
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Mucous membranes (mucosa) Line body cavities that open to exterior environment Epithelial cells secrete mucus to moisten & protect surface Examples: digestive tract, respiratory passageway, urinary tract, reproductive passageways
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Serous membranes (serosa) Line internal body cavities & cover organs within the cavity Always have two layers – Parietal layer – lines cavity Visceral layer – covers organs within cavity Epithelial cells secrete serous fluid, a watery fluid that lubricates surface of membranes Example: pleura, pericardium, peritoneum
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Cutaneous membrane (a.k.a. skin) Covers & protects body surface from external environment Epithelial layer is epidermis Connective layer is dermis
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Simple - one layer of cells Stratified – more than one layer of cells Pseudostratified – looks like more than one layer but all cells contact basement membrane Cell shape Classifying covering & lining Epithelia : Number of layers Squamous - flat Cuboidal – cube-shaped Columnar - tall columns
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Columnar cells may be modified with microvilli cilia goblet cells Figure 4-3
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Epithelial Tissue Table 4-1
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Epithelial Tissue Simple Squamous Epithelium Figure 4-4(a)
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Epithelial Tissue Simple columnar epithelium
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Epithelial Tissue Stratified Squamous Epithelium Figure 4-5(c) 2 types: Keratinized Non-keratinized
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Epithelial Tissue Pseudostratified Ciliated Columnar Figure 4-5(a)
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Connective Tissue (CT) Characteristics: Cells differ depending on specific type of CT (e.g. mesenchymal, fibroblasts, chondrocytes, osteocytes) Cells usually widely spaced with intercellular matrix between Usually well vascularized (exception: cartilage) Usually do not regenerate easily Repair ability varies depending on type of CT
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Connective Tissues Components of Connective Tissues: Specialized cells Extracellular matrix Ground substance Varies in consistency from liquid to gel-like to solid, depending on specific CT Protein fibers Collagen – provides strength Elastic – provides elasticity, resiliency Reticular – provides support
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Connective Tissues Whereas in epithelial tissue, the cell shape & layers were important to determine the function of the tissue, in connective tissues, the matrix of the tissue most directly determines the functional qualities of the tissue.
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Classification of Connective Tissues Embryonic CT - Mesenchyme Connective tissue proper Loose Dense Supportive connective tissues Cartilage Bone (osseous) tissue Fluid connective tissues Blood Lymph
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Connective Tissues Major Types of Connective Tissue Figure 4-7 MESENCHYME
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Mesenchyme An embryonic CT with mesenchymal cells in a thick fluid ground substance with some collagen & reticular fibers. Mesenchyme is the precursor to all other forms of CT
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Connective Tissue “Proper” Most common type of cell present is the fibroblast, but these CT’s may also contain adipocytes, macrophages, & other WBCs. The cells are surrounded by a syrupy ground substance that contains hyaluronic acid. Fibers vary & may be arranged loosely or densely packed together.
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Connective Tissue Proper Depending on the arrangement of fibers, CT proper can be classified into: Loose CTs Areolar Adipose Dense CTs Dense regular (collagenous) Dense irregular
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Areolar Connective Tissue Figure 4-9(a)
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Adipose Connective Tissue Figure 4-9(b)
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Dense Regular Connective Tissue Figure 4-9(c)
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Dense Irregular Connective Tissue
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Supportive Connective Tissues Chondrocytes in lacunae of interstitial fluid within a firm gel-like ground substance of chondroitin sulfate Avascular Covered by a fibrous perichondrium Three types of cartilage Hyaline cartilage Elastic cartilage Fibrocartilage Cartilage
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Hyaline Cartilage Figure 4-10(a)
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Elastic Cartilage Figure 4-10(b)
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Fibrocartilage Figure 4-10(c)
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Supportive Connective Tissues Osteocytes in lacunae of interstitial fluid within a calcified matrix Matrix comprised of osteoid (mainly collagen) & calcium salts (mainly C a 3 (PO 4 ) 2 ) Because of the density of the matrix, osteocytes communicate & receive O 2 / nutrients across canaliculi Osseous tissue covered by fibrous periosteum Well vascularized tissue Bone (Osseous Tissue)
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Osseous (Bone) Tissue Bone tissue classified on the basis of the pattern (functional unit) of the matrix Two types of bone tissue – Spongy (cancellous) Dense (compact)
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Osseous Tissue Fig. 6-3 Spongy (cancellous) bone tissue: Matrix arranged in trabeculae pattern surrounding marrow spaces Marrow spaces of spongy bone contain red bone marrow
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Osseous (Bone) Tissue Compact (dense) bone tissue: Matrix forms osteons (Haversian systems) Osteons comprised of concentric lamellae (layers of matrix containing osteocytes) surrounding a central (Haversian) canal, which contains BVs Osteocytes interconnected by canaliculi which radiate out across lamellae BVs of central canals interconnect across perforating (Volkmann’s) canals
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Fluid (liquid) Connective Tissues Cells + a liquid ground substance Blood RBCs, WBCs, platelets + plasma Lymph Lymphocytes (WBCs) + lymph fluid
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Tissue Injuries and Repair Many different types of injuries can affect tissues – physical (e.g. cuts, bruises), thermal (e.g. burns), chemical, infections An injury usually harms multiple tissues simultaneously Tissues make coordinated response to restore homeostasis Two response processes Inflammation Repair (Regeneration)
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Tissue Injuries and Repair Inflammation (a.k.a. the inflammatory response) Homeostatic response designed to isolate the injured area & cleanup damaged tissue Cells within CTs known as mast cells release chemicals (histamine, heparin) which cause vasodilation & increased capillary permeability
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Tissue Injuries & Repair Vasodilation (resulting in increased blood flow) & increased capillary permeability lead to the 4 classic signs of inflammation: Warmth Redness Swelling Pain
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Tissue Injuries and Repair Repair (Regeneration) Response designed to repair/replace damaged tissues & restore function Fibroblasts (CT cells) in damaged area & lay down collagen fibers to create scar tissue (fibrous tissue)
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Tissue Injuries and Repair Degree of replacement to original tissue type depends on type of tissue Epithelial cells regenerate to replace the damaged epithelial tissues CT proper, bone tissues & smooth muscle heal fairly well Cartilage, neural tissue, skeletal & cardiac muscle tissues do not heal well at all
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