Biol 2430 Anatomy and Physiology
Lect #2Muse9/14/11
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 of cells • 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
Cancertumors 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
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
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
• Fibroblasts
• Fibrocytes
• Macrophages
• Adipocytes
• Mesenchymal cells
• Melanocytes
• Mast cells
• Lymphocytes
• Microphages
Nine Cell Types of Connective Tissue Proper
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
Figure 4–14 The Types of Cartilage.
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.
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