Biol 2430 Anatomy and Physiology Lect 2 Muse

Biol 2430 Anatomy and Physiology Lect #2 Muse 9/14/11

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

Stem and Progenitor Cells Stem cell • can divide to form two new stem cells • self-renewal • can divide to form a stem cell and a progenitor cell • totipotent – can give rise to every cell type • pluripotent – can give rise to a restricted number of cell types Progenitor cell • committed cell • can divide to become any of a restricted number • pluripotent

Stem and Progenitor Cells

Control of Cell Division • cell division capacities vary greatly among cell types • skin and blood cells divide often and continually • neuron cells divide a specific number of times then cease • chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock • cells divide to provide a more favorable surface area to volume relationship • growth factors and hormones stimulate cell division • hormones stimulate mitosis of smooth muscle cells in uterus • epidermal growth factor stimulates growth of new skin

Cancer tumors are the consequence of a loss of cell cycle control Traditional control of growth is lost: cells become independent of growth factors. cells lose contact inhibition in many cases cells become immortal

Telomeres cap the ends of chromosomes Chromosomes tagged with anti-telomerase antibodies

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 – 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 • Functions of Epithelial Tissue – Provide physical protection – Control permeability – Provide sensation – Produce specialized secretions (glandular epithelium)

Epithelial Tissues Figure 4– 1 The Polarity of Epithelial Cells.

Epithelial Tissues • Maintaining the Integrity of Epithelia – Intercellular connections – Attachment to basal lamina – Epithelial maintenance and repair

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– 4 Cuboidal 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 • 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 • Glandular Epithelia – Endocrine glands • Release hormones: – into interstitial fluid – no ducts – Exocrine glands • Produce secretions: – onto epithelial surfaces – through ducts

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 Nine Cell Types of Connective Tissue Proper • • • Fibroblasts Fibrocytes Macrophages Adipocytes Mesenchymal cells • • Melanocytes Mast cells Lymphocytes Microphages

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 – 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 • 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 Figure 4– 8 The Cells and Fibers of Connective Tissue Proper.

Connective Tissues Figure 4– 12 Formed Elements of the Blood.

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 Figure 4– 13 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 4– 14 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 4– 15 Bone.

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 4– 16 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 body’s framework of connective tissue • Layers and wrappings that support or surround organs

Internal Framework of the Body Figure 4– 17 The Fasciae.

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)

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