Chapter 4 Tissues Muse 2430 lecture #2 1/14/13

The Cell Cycle

Stem and Progenitor Cells

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

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 (cont’d) 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 Glands 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 4–1 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

Cell Junctions Contact points between the plasma membranes of tissue cells 5 most common types: Tight junctions Adherens junctions Desmosomes Hemidesmosomes Gap junctions

Epithelial Tissues Cell Junctions Occluding (Tight) junctions—between two plasma membranes Adhesion belt attaches to terminal web Prevents passage of water and solutes Isolates wastes in the lumen Gap junctions—allow 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 4–2 Intercellular Connections

Epithelial Tissues Figure 4–2 Intercellular Connections

Epithelial Tissues Figure 4–2 Intercellular Connections

Epithelial Tissues Figure 4–2 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 4–3 Squamous Epithelia.

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

Classification of Epithelia Figure 4–3 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 4–4 Cuboidal Epithelia.

Classification of Epithelia Figure 4–4 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 4–4 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 4–5 Columnar Epithelia.

Classification of Epithelia Figure 4–5 Columnar Epithelia.

Classification of Epithelia Figure 4–5 Columnar Epithelia.

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 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 4–6 Modes of Glandular Secretion.

Classification of Epithelia Figure 4–6 Modes of Glandular Secretion.

Classification of Epithelia Figure 4–6 Modes of Glandular Secretion.

Classification of Epithelia Figure 4–6 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 4–7 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: 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 4–8 The Cells and Fibers of Connective Tissue Proper.

Connective Tissues Figure 4–8 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 4–9 Connective Tissues in Embryos.

Connective Tissues [INSERT FIG. 4.9b] Figure 4–9 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 4–10 Adipose and Reticular Tissues.

Connective Tissues Figure 4–10 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 4–11 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 4–11 Dense Connective Tissues.

Connective Tissues Elastic Tissue Made of elastic fibers For example, elastic ligaments of spinal vertebrae

Connective Tissues Figure 4–11 Dense 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: Peritoneum: Pericardium: Lines pleural cavities Covers lungs Peritoneum: Lines peritoneal cavity Covers abdominal organs Pericardium: Lines pericardial cavity Covers heart

Membranes Figure 4–16 Membranes.

Membranes Cutaneous membrane Synovial membranes 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 4–16 Membranes.

Neural Tissue Figure 4–19 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 tissue’s 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)