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Body Tissues Levels of Structural Organization • Chemical – atoms combined to form molecules • Cellular – cells are made of molecules • Tissue – consists of similar types of cells • Organ – made up of different types of tissues • Organ system – consists of different organs that work closely together • Organismal – made up of the organ systems Levels of Structural Organization Smooth muscle cell Molecules 2 Cellular level Cells are made up of molecules. Atoms 1 Chemical level Atoms combine to form molecules. 3 Tissue level Tissues consist of similar types of cells. Smooth muscle tissue Heart Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Connective tissue 4 Organ level Organs are made up of different types of tissues. Blood vessel (organ) 6 Organismal level The human organism is made up of many organ systems. 5 Organ system level Organ systems consist of different organs that work together closely. Figure 1.1 Levels of Structural Organization Molecules Atoms 1 Chemical level Atoms combine to form molecules. Figure 1.1 Levels of Structural Organization Smooth muscle cell 2 Cellular level Cells are made up of molecules. Molecules Atoms 1 Chemical level Atoms combine to form molecules. Figure 1.1 Levels of Structural Organization Smooth muscle cell Molecules 2 Cellular level Cells are made up of molecules. Atoms 1 Chemical level Atoms combine to form molecules. 3 Tissue level Tissues consist of similar types of cells. Smooth muscle tissue Figure 1.1 Levels of Structural Organization Smooth muscle cell Molecules 2 Cellular level Cells are made up of molecules. Atoms 1 Chemical level Atoms combine to form molecules. 3 Tissue level Tissues consist of similar types of cells. Smooth muscle tissue Epithelial tissue Smooth muscle tissue Connective tissue Blood vessel (organ) 4 Organ level Organs are made up of different types of tissues. Figure 1.1 Levels of Structural Organization Smooth muscle cell Molecules 2 Cellular level Cells are made up of molecules. Atoms 1 Chemical level Atoms combine to form molecules. 3 Tissue level Tissues consist of similar types of cells. Smooth muscle tissue Heart Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Connective tissue 4 Organ level Organs are made up of different types of tissues. Blood vessel (organ) 5 Organ system level Organ systems consist of different organs that work together closely. Figure 1.1 Levels of Structural Organization Smooth muscle cell Molecules 2 Cellular level Cells are made up of molecules. Atoms 1 Chemical level Atoms combine to form molecules. 3 Tissue level Tissues consist of similar types of cells. Smooth muscle tissue Heart Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Connective tissue 4 Organ level Organs are made up of different types of tissues. Blood vessel (organ) 6 Organismal level The human organism is made up of many organ systems. 5 Organ system level Organ systems consist of different organs that work together closely. Figure 1.1 Body Tissues • Tissues – Groups of cells with similar structure and function – Four primary types • • • • Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue 4-1 Four Types of Tissue • Epithelial Tissue – Covers exposed surfaces – Lines internal passageways – Forms glands • Connective Tissue – Fills internal spaces – Supports other tissues – Transports materials – Stores energy 4-1 Four Types of Tissue • Muscle Tissue – Specialized for contraction – Skeletal muscle, heart muscle, and walls of hollow organs • Neural Tissue – Carries electrical signals from one part of the body to another Epithelial Tissues • Locations – Body coverings – Body linings – Glandular tissue • Functions – Protection – Absorption – Filtration – Secretion – Sensation Epithelium Characteristics • Cells fit closely together and often form sheets (cell junctions) • The apical surface is the free surface of the tissue • The lower surface of the epithelium rests on a basement membrane (basal lamina) • Avascular (no blood supply) • Regenerate easily if well nourished Cell Junctions • Tight junctions – So close that are sometimes impermeable • Adherens junctions – Transmembrane linker proteins • Desmosomes – Anchoring junctions – Filaments anchor to the opposite side • Gap junctions – Allow small molecules to move between cells Figure 4-2a Cell Junctions Tight junction Adhesion belt Terminal web Spot desmosome Gap junctions Hemidesmosome This is a diagrammatic view of an epithelial cell, showing the major types of intercellular connections. Figure 4-2b Cell Junctions Interlocking junctional proteins Tight junction Terminal web Adhesion belt A tight junction is formed by the fusion of the outer layers of two plasma membranes. Tight junctions prevent the diffusion of fluids and solutes between the cells. A continuous adhesion belt lies deep to the tight junction. This belt is tied to the microfilaments of the terminal web. Figure 4-2c Cell Junctions Embedded proteins (connexons) Gap junctions permit the free diffusion of ions and small molecules between two cells. Figure 4-2d Cell Junctions Intermediate filaments Cell adhesion molecules (CAMs) Dense area Proteoglycans A spot desmosome ties adjacent cells together. Figure 4-2e Cell Junctions Clear layer Dense layer Hemidesmosomes attach a cell to extracellular structures, such as the protein fibers in the basement membrane. Basement membrane Classification of Epithelia • Number of cell layers – Simple—one layer – Stratified—more than one layer Figure 3.17a Classification of Epithelia • Shape of cells – Squamous • flattened – Cuboidal • cube-shaped – Columnar • column-like Figure 3.17b Simple Epithelia • Simple squamous – Single layer of flat cells – Functions in Absorption and diffusion – Usually forms membranes • Lines body cavities (Mesothelium) • Lines hearts and capillaries (Endothelium) Lining of Artery Figure 4-3a Squamous Epithelia Simple Squamous Epithelium LOCATIONS: Mesothelia lining ventral body cavities; endothelia lining heart and blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs FUNCTIONS: Reduces friction; controls vessel permeability; performs absorption and secretion Cytoplasm Nucleus Connective tissue Lining of peritoneal cavity LM 238 Simple Epithelia • Simple cuboidal – Single layer of cube-like cells – Common in glands and their ducts – Forms walls of kidney tubules – Covers the ovaries – Functions in secretion and absorption Figure 4-4a Cuboidal and Transitional Epithelia Simple Cuboidal Epithelium LOCATIONS: Glands; ducts; portions of kidney tubules; thyroid gland Connective tissue FUNCTIONS: Limited protection, secretion, absorption Nucleus Cuboidal cells Basement membrane Kidney tubule LM 650 Simple Epithelia • Simple columnar – Single layer of tall cells – Often includes mucusproducing goblet cells – Lines digestive tract – Functions in absorption and secretion Figure 4-5a Columnar Epithelia Simple Columnar Epithelium LOCATIONS: Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys FUNCTIONS: Protection, secretion, absorption Microvilli Cytoplasm Nucleus Intestinal lining Basement membrane Loose connective tissue LM 350 Simple Epithelia • Pseudostratified columnar – Single layer, but some cells are shorter than others – Often looks like a double layer of cells – Sometimes ciliated, such as in the respiratory tract – May function in absorption or secretion – Cilia movement Figure 4-5b Columnar Epithelia Pseudostratified Ciliated Columnar Epithelium LOCATIONS: Lining of nasal cavity, trachea, and bronchi; portions of male reproductive tract Cilia Cytoplasm FUNCTIONS: Protection, secretion, move mucus with cilia Nuclei Basement membrane Trachea Loose connective tissue LM 350 Table 4-1 Classifying Epithelia Stratified Epithelia • Stratified squamous – Cells at the apical surface are flattened – Found as a protective covering where friction is common – Locations • Skin • Mouth • Esophagus Protects against attacks Keratin protein adds strength and water resistance Figure 4-3b Squamous Epithelia Stratified Squamous Epithelium LOCATIONS: Surface of skin; lining of mouth, throat, esophagus, rectum, anus, and vagina FUNCTIONS: Provides physical protection against abrasion, pathogens, and chemical attack Squamous superficial cells Stem cells Basement membrane Connective tissue Surface of tongue LM 310 Stratified Epithelia • Stratified cuboidal—two layers of cuboidal cells - Found in sweat ducts and mammary glands – Rare in human body – Found mainly in ducts of large glands LOCATIONS: Lining of some ducts (rare) FUNCTIONS: Protection, secretion, absorption Lumen of duct Stratified cuboidal cells Basement membrane Nuclei Connective tissue Stratified Epithelia • Stratified columnar—surface cells are columnar, cells underneath vary in size and shape – Rare in human body – Found mainly in ducts of large glands Stratified Columnar Epithelium LOCATIONS: Small areas of the pharynx, epiglottis, anus, mammary glands, salivary gland ducts, and urethra FUNCTION: Protection Loose connective tissue Deeper basal cells Superficial columnar cells Cytoplasm Nuclei Basement membrane Stratified Epithelia • Transitional epithelium – Shape of cells depends upon the amount of stretching – Lines organs of the urinary system Tolerates repeated cycles of stretching and recoiling and returns to its previous shape without damage Figure 4-4c Cuboidal and Transitional Epithelia Transitional Epithelium LOCATIONS: Urinary bladder; renal pelvis; ureters FUNCTIONS: Permits expansion and recoil after stretching Epithelium (relaxed) Basement membrane Empty bladder Connective tissue and smooth muscle layers LM 400 Epithelium (stretched) Full bladder Urinary bladder Basement membrane Connective tissue and smooth muscle layers LM 400 LM 400 Pap Smear (Papanicolaou Test) • Involves examining cells from the stratified squamous epithelium Glandular Epithelium • Gland – One or more cells responsible for secreting a particular product • Two major gland types – Endocrine gland • Ductless since secretions diffuse into blood vessels (interstitial fluid) • All secretions are hormones • RELEASE hormones – Exocrine gland • Secretions empty through ducts to the epithelial surface • Include sweat and oil glands • PRODUCE hormones Classification of glands • By where they release their product – Exocrine: external secretion onto body surfaces (skin) or into body cavities – Endocrine: secrete messenger molecules (hormones) which are carried by blood to target organs; “ductless” glands • By whether they are unicellular or multicellular Exocrine glands unicellular or multicellular Unicellular: goblet cell scattered within epithelial lining of intestines and respiratory tubes Product: mucin mucus is mucin & water Multicellular exocrine glands Gland Structure • Multicellular glands 1. Structure of the duct » Simple (undivided) » Compound (divided) 2. Shape of secretory portion of the gland » Tubular (tube shaped) » Alveolar or acinar (blind pockets) 3. Relationship between ducts and glandular areas » Branched (several secretory areas sharing one duct) Figure 4-7 A Structural Classification of Exocrine Glands SIMPLE GLANDS Duct Gland cells SIMPLE TUBULAR Examples: • Intestinal glands SIMPLE COILED TUBULAR Examples: • Merocrine sweat glands SIMPLE ALVEOLAR (ACINAR) Examples: • Not found in adult; a stage in development of simple branched glands SIMPLE BRANCHED TUBULAR Examples: • Gastric glands • Mucous glands of esophagus, tongue, duodenum SIMPLE BRANCHED ALVEOLAR Examples: • Sebaceous (oil) glands Figure 4-7 A Structural Classification of Exocrine Glands COMPOUND GLANDS COMPOUND TUBULAR Examples: • Mucous glands (in mouth) • Bulbo-urethral glands (in male reproductive system) • Testes (seminiferous tubules) COMPOUND ALVEOLAR (ACINAR) Examples: • Mammary glands COMPOUND TUBULOALVEOLAR Examples: • Salivary glands • Glands of respiratory passages • Pancreas Examples of exocrine gland products • • • • • • • Many types of mucus secreting glands Sweat glands of skin Oil glands of skin Salivary glands of mouth Liver (bile) Pancreas (digestive enzymes) Mammary glands (milk) Endocrine glands • Ductless glands • Release hormones into extracellular space – Hormones are messenger molecules • Hormones enter blood and travel to specific target organs Connective Tissue • Found everywhere in the body • Includes the most abundant and widely distributed tissues • Functions - Structural support - Fluid transport - protection of organs - binds tissues together - energy storage - defense against microbes Connective Tissue Characteristics • Specialized cells • Variations in blood supply – Some tissue types are well vascularized – Some have a poor blood supply or are avascular • Extracellular matrix – Non-living material that surrounds living cells\ – Makes up majority of tissue volume – Gives cells speciality Specialized Cells • Fibroblasts – (most abundant) secretes proteins • Fibrocytes – (2nd most abundant) – maintains tissue fiber • Adipocytes – fat cells • Mesenchymal cells – stem cells that respond to injury • Macrophages – large white blood cells (fixed or free) • Mast cells – stimulate inflammation after injury • Lymphocytes – specialized immune cells • Microphages – phagocytic blood cells • Melanocytes – cells that produce and store melanin (skin pigment) Extracellular Matrix • Two main elements – Ground substance—mostly water along with adhesion proteins and polysaccharide molecules – Fibers • Produced by the cells • Three types – Collagen (white) fibers – Elastic (yellow) fibers – Reticular fibers 4-4 Connective Tissue • Collagen Fibers – Most common fibers in connective tissue proper – Long, straight, and unbranched – Strong and flexible – Resist force in one direction – For example, tendons and ligaments 4-4 Connective Tissue • Reticular Fibers – Network of interwoven fibers (stroma) – Strong and flexible – Resist force in many directions – Stabilize functional cells (parenchyma) and structures – For example, sheaths around organs 4-4 Connective Tissue • Elastic Fibers – Contain elastin – Branched and wavy – Return to original length after stretching – For example, elastic ligaments of vertebrae 4-4 Connective Tissue • Ground Substance – Is clear, colorless, and viscous – Fills spaces between cells and slows pathogen movement Figure 4-8 The Cells and Fibers of Connective Tissue Proper Reticular fibers Melanocyte Fixed macrophage Plasma cell Mast cell Elastic fibers Free macrophage Collagen fibers Blood in vessel Fibroblast Adipocytes (fat cells) Mesenchymal cell Ground substance Lymphocyte 4-4 Connective Tissue • Categories of Connective Tissue Proper – Loose connective tissue • More ground substance, fewer fibers • For example, fat (adipose tissue) – Dense connective tissue • More fibers, less ground substance • For example, tendons Connective Tissue Types • Bone (osseous tissue) – Composed of • Bone cells in lacunae (cavities) • Hard matrix of calcium salts • Large numbers of collagen fibers – Used to protect and support the body Connective Tissue Types • Hyaline cartilage – Most common type of cartilage – Composed of • Abundant collagen fibers • Rubbery matrix – Locations • Larynx • Entire fetal skeleton prior to birth Connective Tissue Types • Elastic cartilage – Provides elasticity – Location • Supports the external ear • Fibrocartilage – Highly compressible – Location • Forms cushion-like discs between vertebrae Connective Tissue Types • Dense connective tissue (dense fibrous tissue) – Main matrix element is collagen fiber – Fibroblasts are cells that make fibers – Locations • Tendons—attach skeletal muscle to bone • Ligaments—attach bone to bone at joints • Dermis—lower layers of the skin Connective Tissue Types • Loose connective tissue types – Areolar tissue • Most widely distributed connective tissue • Soft, pliable tissue like “cobwebs” • Functions as a packing tissue • Contains all fiber types • Can soak up excess fluid (causes edema) Connective Tissue Types • Loose connective tissue types – Adipose tissue • Matrix is an areolar tissue in which fat globules predominate • Many cells contain large lipid deposits • Functions – Insulates the body – Protects some organs – Serves as a site of fuel storage Connective Tissue Types • Loose connective tissue types – Reticular connective tissue • Delicate network of interwoven fibers • Forms stroma (internal supporting network) of lymphoid organs – Lymph nodes – Spleen – Bone marrow Connective Tissue Types • Blood (vascular tissue) – Blood cells surrounded by fluid matrix called blood plasma – Fibers are visible during clotting – Functions as the transport vehicle for materials 4-8 Muscle Tissue • Muscle Tissue – Specialized for contraction – Produces all body movement – Three types of muscle tissue 1. Skeletal muscle tissue – Large body muscles responsible for movement 2. Cardiac muscle tissue – Found only in the heart 3. Smooth muscle tissue – Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive, and reproductive tracts) 4-8 Muscle Tissue • Classification of Muscle Cells – Striated (muscle cells with a banded appearance) – Nonstriated (not banded; smooth) – Muscle cells can have a single nucleus – Muscle cells can be multinucleate – Muscle cells can be controlled voluntarily (consciously) 4-8 Muscle Tissue • Skeletal Muscle Cells – Long and thin – Usually called muscle fibers – Do not divide – New fibers are produced by stem cells (myosatellite cells) Figure 4-18a Muscle Tissue Skeletal Muscle Tissue Cells are long, cylindrical, striated, and multinucleate. Nuclei LOCATIONS: Combined with connective tissues and neural tissue in skeletal muscles FUNCTIONS: Moves or stabilizes the position of the skeleton; guards entrances and exits to the digestive, respiratory, and urinary tracts; generates heat; protects internal organs Muscle fiber Striations Skeletal muscle LM 180 4-8 Muscle Tissue • Cardiac Muscle Cells – Called cardiocytes – Form branching networks connected at intercalated discs – Regulated by pacemaker cells • Smooth Muscle Cells – Small and tapered – Can divide and regenerate Figure 4-18b Muscle Tissue Cardiac Muscle Tissue Nucleus Cells are short, branched, and striated, usually with a single nucleus; cells are interconnected by intercalated discs. Cardiac muscle cells LOCATION: Heart FUNCTIONS: Circulates blood; maintains blood (hydrostatic) pressure Intercalated discs Striations Cardiac muscle LM 450 Figure 4-18c Muscle Tissue Smooth Muscle Tissue Cells are short, spindle-shaped, and nonstriated, with a single, central nucleus. LOCATIONS: Found in the walls of blood vessels and in digestive, respiratory, urinary, and reproductive organs Nucleus FUNCTIONS: Moves food, urine, and reproductive tract secretions; controls diameter of respiratory passageways; regulates diameter of blood vessels Smooth muscle cell Smooth muscle LM 235 4-9 Neural Tissue • Neural Tissue – Also called nervous or nerve tissue • Specialized for conducting electrical impulses • Rapidly senses internal or external environment • Processes information and controls responses – Neural tissue is concentrated in the central nervous system • Brain • Spinal cord 4-9 Neural Tissue • Two Types of Neural Cells 1. Neurons • Nerve cells • Perform electrical communication 2. Neuroglia • Supporting cells • Repair and supply nutrients to neurons 4-9 Neural Tissue • Cell Parts of a Neuron – Cell body • Contains the nucleus and nucleolus – Dendrites • Short branches extending from the cell body • Receive incoming signals – Axon (nerve fiber) • Long, thin extension of the cell body • Carries outgoing electrical signals to their destination Figure 4-19 Neural Tissue NEURONS NEUROGLIA (supporting cells) Nuclei of neuroglia Cell body Axon • Maintain physical structure of tissues • Repair tissue framework after injury • Perform phagocytosis • Provide nutrients to neurons • Regulate the composition of the interstitial fluid surrounding neurons Nucleolus Nucleus of neuron Dendrites LM 600 Dendrites (contacted by other neurons) Mitochondrion Nucleus Axon (conducts information to other cells) Microfibrils and microtubules Nucleolus Contact with other cells Cell body (contains nucleus and major organelles) A representative neuron (sizes and shapes vary widely) Figure 4-19 Neural Tissue Nuclei of neuroglia Cell body Axon Nucleolus Nucleus of neuron Dendrites LM 600 Figure 4-19 Neural Tissue NEUROGLIA (supporting cells) • Maintain physical structure of tissues • Repair tissue framework after injury • Perform phagocytosis • Provide nutrients to neurons • Regulate the composition of the interstitial fluid surrounding neurons Figure 4-19 Neural Tissue Dendrites (contacted by other neurons) Mitochondrion Nucleus Axon (conducts information to other cells) Microfibrils and microtubules Nucleolus Cell body (contains nucleus A representative neuron and major organelles) (sizes and shapes vary widely) Contact with other cells