Tissues - University of Michigan

Chapter 4 Tissues Muse 2430 lecture #3 5/14/12 What is a Tissue? A tissue is a group of cells 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 Development of Tissues

Tissues of the body develop from three primary germ layers: Ectoderm, Endoderm, and Mesoderm Epithelial tissues develop from all three germ layers All connective tissue and most muscle tissues drive from mesoderm Nervous tissue develops from ectoderm

A little embryology Cell Junctions Contact points between the plasma membranes of tissue cells 5 most common types: Tight junctions Adherens junctions

Desmosomes Hemidesmosomes Gap junctions Four Types of Tissues Tissues are collections of cells and cell products that perform specific, limited functions Types of tissue

Epithelial tissue Covers exposed surfaces Lines internal passageways Forms glands Four Types of Tissues Types of Tissue (contd) Connective tissue Fills internal spaces

Supports other tissues Transports materials Stores energy 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 Epithelia Layers of cells covering internal or external surfaces Glands Structures that produce secretions

Epithelial Tissues Characteristics of Epithelia Cellularity (cell junctions) Polarity (apical and basal surfaces) Attachment (basal lamina) Avascularity Regeneration

Epithelial Tissues Figure 41 The Polarity of Epithelial Cells. Epithelial Tissues Functions of Epithelial Tissue Provide physical protection Control permeability Provide sensation

Produce specialized secretions (glandular epithelium) Epithelial Tissues Specializations of Epithelial Cells Move fluids over the epithelium (protection) Move fluids through the epithelium (permeability) Produce secretions (protection and messengers)

Free Surface and Attached Surface Polarity Apical surfaces: microvilli increase absorption or secretion cilia (ciliated epithelium) move fluid Basolateral surfaces Epithelial Tissues

Maintaining the Integrity of Epithelia Intercellular connections Attachment to basal lamina Epithelial maintenance and repair Epithelial Tissues Intercellular Connections Support and communication CAMs (cell adhesion molecules):

transmembrane proteins Intercellular cement: proteoglycans Hyaluronan (hyaluronic acid): glycosaminoglycans Epithelial Tissues

Intercellular Connections Cell junctions Form bonds with other cells or extracellular material: occluding (tight) junctions gap junctions macula adherens (desmosomes) Intercellular Connections

Epithelial Tissues Cell Junctions Occluding (Tight) junctionsbetween two plasma membranes Adhesion belt attaches to terminal web Prevents passage of water and solutes Isolates wastes in the lumen Gap junctionsallow rapid communication

Held together by channel proteins (junctional proteins, connexons) Allow ions to pass Coordinate contractions in heart muscle Epithelial Tissues Cell Junctions Macula adherens (Desmosomes) CAMs, dense areas, and intercellular

cement Spot desmosomes tie cells together allow bending and twisting Hemidesmosomes attach cells to the basal lamina Epithelial Tissues

Attachment to the Basal Lamina Clear layer (Lamina lucida) Thin layer Secreted by epithelia Barrier to proteins Dense layer (Lamina densa) Thick fibers Produced by connective tissue

Strength and filtration Epithelial Tissues Figure 42 Intercellular Connections Epithelial Tissues Figure 42 Intercellular Connections

Epithelial Tissues Figure 42 Intercellular Connections Epithelial Tissues Figure 42 Intercellular Connections

Epithelial Tissues Epithelial Maintenance and Repair Epithelia are replaced by division of germinative cells (stem cells) Near basal lamina Classification of Epithelia Singular epithelium; plural epithelia Classes of Epithelia

Based on shape Squamous epithelia: thin and flat Cuboidal epithelia: square shaped Columnar epithelia: tall, slender rectangles Based on layers Simple epithelium: single layer of cells Stratified epithelium: several layers of cells

Classification of Epithelia Classification of Epithelia Classification of Epithelia Squamous Epithelia Simple squamous epithelium Absorption and diffusion

Mesothelium Lines body cavities Endothelium Lines heart and blood vessels Classification of Epithelia Figure 43 Squamous Epithelia.

Classification of Epithelia Squamous Epithelia Stratified squamous epithelium Protects against attacks Keratin protein adds strength and water resistance Classification of Epithelia

Figure 43 Squamous Epithelia. Classification of Epithelia Cuboidal Epithelia Simple cuboidal epithelium Secretion and absorption Stratified cuboidal epithelia Sweat ducts and mammary ducts

Classification of Epithelia Figure 44 Cuboidal Epithelia. Classification of Epithelia Figure 44 Cuboidal Epithelia.

Classification of Epithelia Transitional Epithelium Tolerates repeated cycles of stretching and recoiling and returns to its previous shape without damage Appearance changes as stretching occurs Situated in regions of the urinary system (e.g. urinary bladder) Classification of Epithelia

Figure 44 Cuboidal Epithelia. Classification of Epithelia Columnar Epithelia Simple columnar epithelium Absorption and secretion Pseudostratified columnar epithelium

Cilia movement Stratified columnar epithelium Protection Classification of Epithelia Figure 45 Columnar Epithelia.

Classification of Epithelia Figure 45 Columnar Epithelia. Classification of Epithelia Figure 45 Columnar Epithelia. Classification of Epithelia

Glandular Epithelia Endocrine glands Release hormones: into interstitial fluid no ducts Exocrine glands Produce secretions: onto epithelial surfaces

through ducts Mechanisms of Glandular Secretion Classification of Epithelia Modes of Secretion in Glandular Epithelia Merocrine secretion Is produced in Golgi apparatus Is released by vesicles (exocytosis) For example, sweat glands

Apocrine secretion Is produced in Golgi apparatus Is released by shedding cytoplasm For example, mammary gland Holocrine secretion Is released by cells bursting, killing gland cells Gland cells replaced by stem cells

For example, sebaceous gland Classification of Epithelia Figure 46 Modes of Glandular Secretion. Classification of Epithelia Figure 46 Modes of Glandular Secretion.

Classification of Epithelia Figure 46 Modes of Glandular Secretion. Classification of Epithelia Figure 46 Modes of Glandular Secretion.

Classification of Epithelia Glandular Epithelia Types of secretions Serous glands: watery secretions Mucous glands: secrete mucins

Mixed exocrine glands: both serous and mucous Classification of Epithelia Glandular Epithelia Gland structure Unicellular glands Mucous (goblet) cells are the only unicellular exocrine glands:

scattered among epithelia for example, in intestinal lining Classification of Epithelia Glandular Epithelia Gland structure Multicellular glands: structure of the duct: simple (undivided)

compound (divided) shape of secretory portion of the gland: tubular (tube shaped) alveolar or acinar (blind pockets) relationship between ducts and glandular areas: branched (several secretory areas sharing one duct) Classification of Epithelia

Figure 47 A Structural Classification of Exocrine Glands. Classification of Epithelia Figure 47 A Structural Classification of Exocrine Glands. Connective Tissues Connect epithelium to the rest of the body (basal lamina)

Provide structure (bone) Store energy (fat) Transport materials (blood) Have no contact with environment Connective Tissues Characteristics of Connective Tissues Specialized cells Solid extracellular protein fibers

Fluid extracellular ground substance The extracellular components of connective tissues (fibers and ground substance) make up the matrix Majority of tissue volume Determines specialized function Connective Tissues

Classification of Connective Tissues Connective tissue proper Connect and protect Fluid connective tissues Transport Supportive connective tissues Structural strength

Connective Tissues Categories of Connective Tissue Proper Loose connective tissue More ground substance, less fibers For example, fat (adipose tissue) Dense connective tissue More fibers, less ground substance

For example, tendons Connective Tissues Nine Cell Types of Connective Tissue Proper

Fibroblasts Fibrocytes Macrophages Adipocytes Mesenchymal cells

Melanocytes Mast cells Lymphocytes Microphages Connective Tissues

Connective Tissue Proper Cells Fibroblasts The most abundant cell type: found in all connective tissue proper secrete proteins and hyaluronan (cellular cement) Fibrocytes The second most abundant cell type: found in all connective tissue proper

maintain the fibers of connective tissue proper Connective Tissues Connective Tissue Proper Cells Macrophages Large, amoeba-like cells of the immune system: eat pathogens and damaged cells fixed macrophages stay in tissue free macrophages migrate

Adipocytes Fat cells: each cell stores a single, large fat droplet Mesenchymal Cells Stem cells that respond to injury or infection: differentiate into fibroblasts, macrophages, etc.

Connective Tissues Connective Tissue Proper Cells Melanocytes Synthesize and store the brown pigment melanin Mast Cells Stimulate inflammation after injury or infection: release histamine and heparin

Basophils are leukocytes (white blood cells) that also contain histamine and heparin Connective Tissues Connective Tissue Proper Cells Lymphocytes Specialized immune cells in lymphoid (lymphatic) system: For example, lymphocytes may develop into plasma cells (plasmocytes) that produce antibodies

Microphages Phagocytic blood cells: respond to signals from macrophages and mast cells For example, neutrophils and eosinophils Connective Tissues Connective Tissue Fibers 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 Connective Tissues Connective Tissue Fibers 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 Connective Tissues Connective Tissue Fibers

Elastic fibers Contain elastin Branched and wavy Return to original length after stretching For example, elastic ligaments of vertebrae Connective Tissues Ground Substance Is clear, colorless, and viscous

Fills spaces between cells and slows pathogen movement Connective Tissues Figure 48 The Cells and Fibers of Connective Tissue Proper. Connective Tissues

Figure 48 The Cells and Fibers of Connective Tissue Proper. Connective Tissues Embryonic Connective Tissues Are not found in adults Mesenchyme (embryonic stem cells) The first connective tissue in embryos Mucous connective tissue

Loose embryonic connective tissue Connective Tissues Figure 49 Connective Tissues in Embryos. Connective Tissues [INSERT FIG. 4.9b]

Figure 49 Connective Tissues in Embryos. Connective Tissues Loose Connective Tissues The packing materials of the body Three types in adults Areolar Adipose

Reticular Connective Tissues Areolar Tissue Least specialized Open framework Viscous ground substance Elastic fibers Holds blood vessels and capillary beds

For example, under skin (subcutaneous layer) Connective Tissues Adipose Tissue Contains many adipocytes (fat cells) Types of adipose tissue White fat:

most common stores fat absorbs shocks slows heat loss (insulation) Brown fat:

more vascularized adipocytes have many mitochondria when stimulated by nervous system, fat break down accelerates, releasing energy absorbs energy from surrounding tissues Connective Tissues Adipose Tissue Adipose cells

Adipocytes in adults do not divide: expand to store fat shrink as fats are released Mesenchymal cells divide and differentiate: to produce more fat cells when more storage is needed

Connective Tissues Reticular Tissue Provides support Complex, three-dimensional network Supportive fibers (stroma) Support functional cells (parenchyma) Reticular organs Spleen, liver, lymph nodes, and bone marrow

Connective Tissues Figure 410 Adipose and Reticular Tissues. Connective Tissues Figure 410 Adipose and Reticular Tissues.

Connective Tissues Dense Connective Tissues Connective tissues proper, tightly packed with high numbers of collagen or elastic fibers Dense regular connective tissue Dense irregular connective tissue Elastic tissue Connective Tissues

Dense Regular Connective Tissue Tightly packed, parallel collagen fibers Tendons attach muscles to bones Ligaments connect bone to bone and stabilize organs Aponeuroses attach in sheets to large, flat muscles Connective Tissues

Figure 411 Dense Connective Tissues. Connective Tissues Dense Irregular Connective Tissue Interwoven networks of collagen fibers Layered in skin Around cartilages (perichondrium) Around bones (periosteum)

Form capsules around some organs (e.g., liver, kidneys) Connective Tissues Figure 411 Dense Connective Tissues. Connective Tissues Elastic Tissue

Made of elastic fibers For example, elastic ligaments of spinal vertebrae Connective Tissues Figure 411 Dense Connective Tissues. Connective Tissues Fluid Connective Tissues

Blood and lymph Watery matrix of dissolved proteins Carry specific cell types (formed elements) Formed elements of blood red blood cells (erythrocytes) white blood cells (leukocytes) platelets Connective Tissues

Fluid Elements of Fluid Connective Tissues Extracellular Plasma Interstitial fluid Lymph Connective Tissues

Figure 412 Formed Elements of the Blood. Connective Tissues Lymph Extracellular fluid Collected from interstitial space Monitored by immune system Transported by lymphoid (lymphatic) system Returned to venous system

Connective Tissues Fluid Tissue Transport Systems Cardiovascular system (blood) Arteries Capillaries Veins Lymphoid (lymphatic) system (lymph)

Lymphatic vessels Supportive Connective Tissues Support soft tissues and body weight Cartilage Gel-type ground substance For shock absorption and protection Bone

Calcified (made rigid by calcium salts, minerals) For weight support Supportive Connective Tissues Cartilage Matrix Proteoglycans derived from chondroitin sulfates Ground substance proteins Chondrocytes (cartilage cells) surrounded by

lacunae (chambers) Supportive Connective Tissues Cartilage Structure No blood vessels: Chondrocytes produce antiangiogenesis factor Perichondrium: Outer, fibrous layer (for strength) Inner, cellular layer (for growth and maintenance)

Supportive Connective Tissues Figure 413 The Growth of Cartilage. Supportive Connective Tissues Figure 413 The Growth of Cartilage.

Supportive Connective Tissues Types of Cartilage Hyaline cartilage Stiff, flexible support Reduces friction between bones Found in synovial joints, rib tips, sternum, and trachea Elastic cartilage Supportive but bends easily

Found in external ear and epiglottis Fibrous cartilage (fibrocartilage) Limits movement

Prevents bone-to-bone contact Pads knee joints Found between pubic bones and intervertebral discs Supportive Connective Tissues Figure 414 The Types of Cartilage. Supportive Connective Tissues

Figure 414 The Types of Cartilage. Supportive Connective Tissues Figure 414 The Types of Cartilage. Supportive Connective Tissues Bone or osseous tissue

Strong (calcified: calcium salt deposits) Resists shattering (flexible collagen fibers) Bone cells or osteocytes Arranged around central canals within matrix Small channels through matrix (canaliculi) access blood supply Periosteum

Covers bone surfaces Fibrous layer Cellular layer Supportive Connective Tissues Figure 415 Bone. Supportive Connective Tissues

Membranes Membranes Are physical barriers That line or cover portions of the body Consist of An epithelium Supported by connective tissues

Membranes Four Types of Membranes Mucous membranes Serous membranes Cutaneous membrane Synovial membranes Membranes Mucous membranes (mucosae)

Line passageways that have external connections In digestive, respiratory, urinary, and reproductive tracts Epithelial surfaces must be moist To reduce friction To facilitate absorption and excretion Lamina propria Is areolar tissue

Membranes Serous Membranes Line cavities not open to the outside Are thin but strong Have fluid transudate to reduce friction Have a parietal portion covering the cavity Have a visceral portion (serosa) covering the organs

Membranes Three Serous Membranes Pleura: Lines pleural cavities Covers lungs Peritoneum: Lines peritoneal cavity

Covers abdominal organs Pericardium: Lines pericardial cavity Covers heart Membranes Figure 416 Membranes.

Membranes Cutaneous membrane Is skin, surface of the body Thick, waterproof, and dry Synovial membranes Line moving, articulating joint cavities Produce synovial fluid (lubricant)

Protect the ends of bones Lack a true epithelium Membranes Figure 416 Membranes. Internal Framework of the Body Connective tissues

Provide strength and stability Maintain positions of internal organs Provide routes for blood vessels, lymphatic vessels, and nerves Fasciae Singular form is fascia The bodys framework of connective tissue Layers and wrappings that support or surround organs

Internal Framework of the Body Three Types of Fasciae Superficial fascia Deep fascia Subserous fascia Internal Framework of the Body

Figure 417 The Fasciae. Muscle Tissue Specialized for contraction Produces all body movement Three types of muscle tissue Skeletal muscle Large body muscles responsible for movement

Cardiac muscle Found only in the heart Smooth muscle Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive, and reproductive tracts) 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) Muscle cells can be controlled involuntarily (automatically)

Muscle Tissue Skeletal Muscle Cells Are long and thin Are usually called muscle fibers Do not divide New fibers are produced by stem cells (myosatellite cells) Muscle Tissue

Figure 418 Muscle Tissue. Muscle Tissue Cardiac muscle cells Are called cardiocytes Form branching networks connected at intercalated discs Are regulated by pacemaker cells

Smooth muscle cells Are small and tapered Can divide and regenerate Muscle Tissue Figure 418 Muscle Tissue.

Muscle Tissue Figure 418 Muscle 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 Neural tissue is concentrated in the central nervous system Brain Spinal cord

Neural Tissue Two Kinds of Neural Cells Neurons Nerve cells Perform electrical communication Neuroglia Supporting cells Repair and supply nutrients to neurons

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 Neural Tissue Figure 419 Neural Tissue.

Tissue Injuries and Repair Tissues respond to injuries to maintain homeostasis Cells restore homeostasis with two processes Inflammation Regeneration Tissue Injuries and Repair Inflammation = inflammatory response

The tissues first response to injury Signs and symptoms of the inflammatory response include Swelling Redness Heat Pain

Tissue Injuries and Repair Inflammatory Response Can be triggered by Trauma (physical injury) Infection (the presence of harmful pathogens) Tissue Injuries and Repair The Process of Inflammation Damaged cells release chemical signals into the

surrounding interstitial fluid Prostaglandins Proteins Potassium ions As cells break down Lysosomes release enzymes That destroy the injured cell And attack surrounding tissues

Tissue destruction is called necrosis Tissue Injuries and Repair The Process of Inflammation Necrotic tissues and cellular debris (pus) accumulate in the wound Abscess: pus trapped in an enclosed area

Injury stimulates mast cells to release Histamine Heparin Prostaglandins Tissue Injuries and Repair The Process of Inflammation Dilation of blood vessels Increases blood circulation in the area

Causes warmth and redness Brings more nutrients and oxygen to the area Removes wastes Plasma diffuses into the area Causing swelling and pain Phagocytic white blood cells Clean up the area

Tissue Injuries and Repair Figure 420 An Introduction to Inflammation. Tissue Injuries and Repair Regeneration When the injury or infection is cleaned up Healing (regeneration) begins

Tissue Injuries and Repair The Process of Regeneration Fibrocytes move into necrotic area Lay down collagen fibers To bind the area together (scar tissue) New cells migrate into area Or are produced by mesenchymal stem cells

Not all tissues can regenerate Epithelia and connective tissues regenerate well Cardiac cells and neurons do not regenerate (or regenerate poorly) Aging and Tissue Aging and Tissue Structure Speed and efficiency of tissue repair

decreases with age, due to Slower rate of energy consumption (metabolism) Hormonal alterations Reduced physical activity Aging and Tissue Effects of Aging Chemical and structural tissue changes Thinning epithelia and connective tissues

Increased bruising and bone brittleness Joint pain and broken bones Cardiovascular disease Mental deterioration Aging and Tissue Aging and Cancer Incidence Cancer rates increase with age 1 in 4 people in the United States develops cancer

Cancer is the #2 cause of death in the United States Environmental chemicals and cigarette smoke cause cancer