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 (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
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 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.
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
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
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.
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:
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