4 The Tissue Level of Organization.

4 The Tissue Level of Organization

An Introduction to Tissues
Learning Outcomes 4-1 Identify the four major types of tissues in the body and describe their roles. 4-2 Discuss the types and functions of epithelial tissue. 4-3 Describe the relationship between form and function for each type of epithelium.

Learning Outcomes 4-4 Compare the structures and functions of the various types of connective tissues. 4-5 Describe how cartilage and bone function as a supporting connective tissue. 4-6 Explain how epithelial and connective tissues combine to form four types of tissue membranes, and specify the functions of each. 4-7 Describe how connective tissue establishes the framework of the body.

Learning Outcomes Describe the three types of muscle tissue and the special structural features of each type. Discuss the basic structure and role of neural tissue 4-10 Describe how injuries affect the tissues of the body. 4-11 Describe how aging affects the tissues of the body.

Structures with discrete structural and functional properties Tissues in combination form organs, such as the heart or liver Organs can be grouped into 11 organ systems

4-1 Four Types of Tissue Tissue
Are collections of cells and cell products that perform specific, limited functions Four types of tissue Epithelial tissue Connective tissue Muscle tissue Neural tissue

4-1 Four Types of Tissue Epithelial Tissue Connective Tissue
Covers exposed surfaces Lines internal passageways Forms glands Connective Tissue Fills internal spaces Supports other tissues Transports materials Stores energy

4-1 Four Types of Tissue Muscle Tissue Neural 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

4-2 Epithelial Tissue Epithelia Glands
Layers of cells covering internal or external surfaces Glands Structures that produce secretions

4-2 Epithelial Tissue Characteristics of Epithelia
Cellularity (cell junctions) Polarity (apical and basal surfaces) Attachment (basement membrane or basal lamina) Avascularity Regeneration

Figure 4-1 The Polarity of Epithelial Cells
Cilia Microvilli Apical surface Golgi apparatus Nucleus Mitochondria Basement membrane Basolateral surfaces 11

4-2 Epithelial Tissue Functions of Epithelial Tissue
Provide Physical Protection Control Permeability Provide Sensation Produce Specialized Secretions (glandular epithelium)

4-2 Epithelial Tissue Specializations of Epithelial Cells Polarity
Move fluids over the epithelium (protection) Move fluids through the epithelium (permeability) Produce secretions (protection and messengers) Polarity Apical surfaces Microvilli increase absorption or secretion Cilia (ciliated epithelium) move fluid Basolateral surfaces

4-2 Epithelial Tissue Maintaining the Integrity of Epithelia
Intercellular connections Attachment to the basement membrane Epithelial maintenance and repair

4-2 Epithelial Tissue Intercellular Connections
Support and communication CAMs (cell adhesion molecules) Transmembrane proteins Intercellular cement Proteoglycans Hyaluronan (hyaluronic acid) Glycosaminoglycans

4-2 Epithelial Tissue Intercellular Connections Cell junctions
Form bonds with other cells or extracellular material Tight junctions Gap junctions Desmosomes

4-2 Epithelial Tissue Tight Junctions Between two plasma membranes
Adhesion belt attaches to terminal web Prevents passage of water and solutes Isolates wastes in the lumen

4-2 Epithelial Tissue Gap Junctions Allow rapid communication
Are held together by channel proteins (junctional proteins, connexons) Allow ions to pass Coordinate contractions in heart muscle

4-2 Epithelial Tissue Desmosomes
CAMs, dense areas, and intercellular cement Spot desmosomes Tie cells together Allow bending and twisting Hemidesmosomes Attach cells to the basal lamina

4-2 Epithelial Tissue Attachment to the Basement Membrane
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

Figure 4-2 Cell Junctions
Interlocking junctional proteins Tight junction Tight junction Adhesion belt Terminal web Spot desmosome Adhesion belt Gap junctions Hemidesmosome Embedded proteins (connexons) Intermediate filaments Clear layer Basement membrane Dense layer Dense area Cell adhesion molecules (CAMs) Proteoglycans 21

Figure 4-2a Cell Junctions
Tight junction Adhesion belt Terminal web Spot desmosome Gap junctions Hemidesmosome This is a diagrammatic view of an epithelial cell, showing the major types of intercellular connections. 22

Figure 4-2b Cell Junctions
Interlocking junctional proteins Tight junction Terminal web Adhesion belt A tight junction is formed by the fusion of the outer layers of two plasma membranes. Tight junctions prevent the diffusion of fluids and solutes between the cells. A continuous adhesion belt lies deep to the tight junction. This belt is tied to the microfilaments of the terminal web. 23

Figure 4-2c Cell Junctions
Embedded proteins (connexons) Gap junctions permit the free diffusion of ions and small molecules between two cells. 24

Figure 4-2d Cell Junctions
Intermediate filaments Cell adhesion molecules (CAMs) Dense area Proteoglycans A spot desmosome ties adjacent cells together. 25

Figure 4-2e Cell Junctions
Clear layer Basement membrane Dense layer Hemidesmosomes attach a cell to extracellular structures, such as the protein fibers in the basement membrane. 26

4-2 Epithelial Tissue Epithelial Maintenance and Repair
Epithelia are replaced by division of germinative cells (stem cells) Near basement membrane

4-3 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

Table 4-1 Classifying Epithelia
29

Table 4-1 Classifying Epithelia
30

Squamous Epithelia Simple squamous epithelium Absorption and diffusion Mesothelium Lines body cavities Endothelium Lines heart and blood vessels

Figure 4-3a Squamous Epithelia
Simple Squamous Epithelium LOCATIONS: Mesothelia lining ventral body cavities; endothelia lining heart and blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs FUNCTIONS: Reduces friction; controls vessel permeability; performs absorption and secretion Cytoplasm Nucleus Connective tissue LM  238 Lining of peritoneal cavity 32

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

Figure 4-3b Squamous Epithelia
Stratified Squamous Epithelium LOCATIONS: Surface of skin; lining of mouth, throat, esophagus, rectum, anus, and vagina FUNCTIONS: Provides physical protection against abrasion, pathogens, and chemical attack Squamous superficial cells Stem cells Basement membrane Connective tissue Surface of tongue LM  310 34

Cuboidal Epithelia Simple cuboidal epithelium Secretion and absorption Stratified cuboidal epithelia Sweat ducts and mammary ducts

Figure 4-4a Cuboidal and Transitional Epithelia
Simple Cuboidal Epithelium LOCATIONS: Glands; ducts; portions of kidney tubules; thyroid gland Connective tissue FUNCTIONS: Limited protection, secretion, absorption Nucleus Cuboidal cells Basement membrane Kidney tubule LM  650 36

Figure 4-4b Cuboidal and Transitional Epithelia
Stratified Cuboidal Epithelium LOCATIONS: Lining of some ducts (rare) FUNCTIONS: Protection, secretion, absorption Lumen of duct Stratified cuboidal cells Basement membrane Nuclei Connective tissue Sweat gland duct LM  500 37

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)

Figure 4-4c Cuboidal and Transitional Epithelia
Transitional Epithelium LOCATIONS: Urinary bladder; renal pelvis; ureters FUNCTIONS: Permits expansion and recoil after stretching Epithelium (relaxed) Basement membrane Connective tissue and smooth muscle layers Empty bladder LM  400 Epithelium (stretched) Basement membrane LM  400 Connective tissue and smooth muscle layers Full bladder LM  400 Urinary bladder 39

Columnar Epithelia Simple columnar epithelium Absorption and secretion Pseudostratified columnar epithelium Cilia movement Stratified columnar epithelium Protection

Figure 4-5a Columnar Epithelia
Simple Columnar Epithelium LOCATIONS: Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys Microvilli Cytoplasm FUNCTIONS: Protection, secretion, absorption Nucleus Basement membrane Loose connective tissue Intestinal lining LM  350 41

Figure 4-5b Columnar Epithelia
Pseudostratified Ciliated Columnar Epithelium LOCATIONS: Lining of nasal cavity, trachea, and bronchi; portions of male reproductive tract Cilia Cytoplasm FUNCTIONS: Protection, secretion, move mucus with cilia Nuclei Basement membrane Loose connective tissue Trachea LM  350 42

Figure 4-5c Columnar Epithelia
Stratified Columnar Epithelium LOCATIONS: Small areas of the pharynx, epiglottis, anus, mammary glands, salivary gland ducts, and urethra Loose connective tissue Deeper basal cells FUNCTION: Protection Superficial columnar cells Lumen Lumen Cytoplasm Nuclei Basement membrane Salivary gland duct LM  175 43

Glandular Epithelia Endocrine glands Release hormones Into interstitial fluid No ducts Exocrine glands Produce secretions Onto epithelial surfaces Through ducts

Glandular Epithelia Modes of Secretion Merocrine secretion Apocrine secretion Holocrine secretion

Merocrine Secretion Produced in Golgi apparatus Released by vesicles (exocytosis) For example, sweat glands Apocrine Secretion Released by shedding cytoplasm For example, mammary glands

Holocrine Secretion Released by cells bursting, killing gland cells Gland cells replaced by stem cells For example, sebaceous glands

Figure 4-6 Modes of Glandular Secretion
Secretory vesicle Golgi apparatus Nucleus TEM  3039 Salivary gland Breaks down Mammary gland Golgi apparatus Secretion Regrowth Hair Sebaceous gland Cells burst, releasing cytoplasmic contents Hair follicle Cells produce secretion, increasing in size Cell division replaces lost cells Stem cell 48

Figure 4-6a Modes of Glandular Secretion
Secretory vesicle Salivary gland Golgi apparatus Nucleus Mammary gland TEM  3039 Merocrine. In merocrine secretion, secretory vesicles are discharged at the apical surface of the gland cell by exocytosis. Hair Sebaceous gland Hair follicle 49

Figure 4-6b Modes of Glandular Secretion
Salivary gland Breaks down Mammary gland Golgi apparatus Secretion Regrowth Apocrine. Apocrine secretion involves the loss of apical cytoplasm. Inclusions, secretory vesicles, and other cytoplasmic components are shed in the process. The gland cell then undergoes growth and repair before it releases additional secretions. Hair Sebaceous gland Hair follicle 50

Figure 4-6c Modes of Glandular Secretion
Salivary gland Cells burst, releasing cytoplasmic contents Mammary gland Cells produce secretion, increasing in size Cell division replaces lost cells Stem cell Hair Holocrine. Holocrine secretion occurs as superficial gland cells burst. Continued secretion involves the replacement of these cells through the mitotic division of underlying stem cells. Sebaceous gland Hair follicle 51

Glandular Epithelia Types of Secretions Serous glands Watery secretions Mucous glands Secrete mucins Mixed exocrine glands Both serous and mucous

Glandular Epithelia Gland Structure Unicellular glands Mucous (goblet) cells are the only unicellular exocrine glands Scattered among epithelia For example, in intestinal lining

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)

Figure 4-7 A Structural Classification of Exocrine Glands
SIMPLE GLANDS Duct Gland cells SIMPLE TUBULAR SIMPLE COILED TUBULAR SIMPLE BRANCHED TUBULAR Examples: Examples: Examples: • Intestinal glands • Merocrine sweat • Gastric glands glands • Mucous glands of esophagus, tongue, duodenum SIMPLE ALVEOLAR (ACINAR) SIMPLE BRANCHED ALVEOLAR Examples: Examples: • Not found in adult; a • Sebaceous (oil) stage in development of simple branched glands glands 55

Figure 4-7 A Structural Classification of Exocrine Glands
COMPOUND GLANDS COMPOUND TUBULAR COMPOUND ALVEOLAR (ACINAR) COMPOUND TUBULOALVEOLAR Examples: Examples: Examples: • Mucous glands (in mouth) • Mammary glands • Salivary glands • Bulbo-urethral glands (in • Glands of respiratory male reproductive system) passages • Testes (seminiferous tubules) • Pancreas 56

4-4 Connective Tissue Characteristics of Connective Tissue
Specialized cells Solid extracellular protein fibers Fluid extracellular ground substance The Extracellular Components of Connective Tissue (Fibers and Ground Substance) Make up the matrix Majority of tissue volume Determines specialized function

4-4 Connective Tissue Functions of Connective Tissue
Establishing a structural framework for the body Transporting fluids and dissolved materials Protecting delicate organs Supporting, surrounding, and interconnecting other types of tissue Storing energy reserves, especially in the form of triglycerides Defending the body from invading microorganisms

4-4 Connective Tissue Classification of Connective Tissues
Connective tissue proper Connect and protect Fluid connective tissues Transport Supporting connective tissues Structural strength

4-4 Connective Tissue Categories of Connective Tissue Proper
Loose connective tissue More ground substance, fewer fibers For example, fat (adipose tissue) Dense connective tissue More fibers, less ground substance For example, tendons

Connective Tissue Proper Cell Populations
Fibroblasts Fibrocytes Adipocytes Mesenchymal cells Macrophages Mast cells Lymphocytes Microphages Melanocytes

4-4 Connective Tissue Fibroblasts Fibrocytes
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

4-4 Connective Tissue Adipocytes Mesenchymal Cells 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.

4-4 Connective Tissue Macrophages
Large, amoeba-like cells of the immune system Eat pathogens and damaged cells Fixed macrophages stay in tissue Free macrophages migrate

4-4 Connective Tissue Mast Cells
Stimulate inflammation after injury or infection Release histamine and heparin Basophils are leukocytes (white blood cells) that also contain histamine and heparin

4-4 Connective Tissue Lymphocytes
Specialized immune cells in lymphatic (lymphoid) system For example, lymphocytes may develop into plasma cells (plasmocytes) that produce antibodies

4-4 Connective Tissue Microphages Melanocytes Phagocytic blood cells
Respond to signals from macrophages and mast cells For example, neutrophils and eosinophils Melanocytes Synthesize and store the brown pigment melanin

4-4 Connective Tissue Connective Tissue Fibers Collagen fibers
Reticular fibers Elastic fibers

4-4 Connective Tissue 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

4-4 Connective Tissue 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

4-4 Connective Tissue Elastic Fibers Contain elastin Branched and wavy
Return to original length after stretching For example, elastic ligaments of vertebrae

4-4 Connective Tissue Ground Substance
Is clear, colorless, and viscous Fills spaces between cells and slows pathogen movement

Figure 4-8 The Cells and Fibers of Connective Tissue Proper
Reticular fibers Mast cell Melanocyte Elastic fibers Fixed macrophage Plasma cell Free macrophage Collagen fibers Blood in vessel Fibroblast Adipocytes (fat cells) Mesenchymal cell Ground substance Lymphocyte 73

Figure 4-8 The Cells and Fibers of Connective Tissue Proper
Elastic fibers Collagen fibers Fibroblast Free macrophage Connective tissue proper LM  502 74

4-4 Connective Tissue 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

Figure 4-9a Connective Tissues in Embryos
Mesenchymal cells Mesenchyme LM  136 This is the first connective tissue to appear in an embryo. 76

Figure 4-9b Connective Tissues in Embryos
Mesenchymal cells Blood vessel Mucous connective tissue (Wharton’s jelly) LM  136 This sample was taken from the umbilical cord of a fetus. 77

4-4 Connective Tissue Loose Connective Tissues
The “packing materials” of the body Three types in adults Areolar Adipose Reticular

4-4 Connective Tissue Areolar Tissue Least specialized Open framework
Viscous ground substance Elastic fibers Holds blood vessels and capillary beds For example, under skin (subcutaneous layer)

4-4 Connective Tissue Adipose Tissue
Contains many adipocytes (fat cells) 2 types of adipose tissue White fat Brown fat

4-4 Connective Tissue White fat Brown 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 breakdown accelerates, releasing energy Absorbs energy from surrounding tissues

4-4 Connective Tissue 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

4-4 Connective Tissue Reticular Tissue Provides support
Complex, three-dimensional network Supportive fibers (stroma) Support functional cells (parenchyma) Reticular organs Spleen, liver, lymph nodes, and bone marrow

Figure 4-10a Adipose and Reticular Tissues
Adipose Tissue LOCATIONS: Deep to the skin, especially at sides, buttocks, breasts; padding around eyes and kidneys FUNCTIONS: Provides padding and cushions shocks; insulates (reduces heat loss); stores energy Adipocytes (white adipose cells) LM  300 Adipose tissue 84

Figure 4-10b Adipose and Reticular Tissues
LOCATIONS: Liver, kidney, spleen, lymph nodes, and bone marrow FUNCTIONS: Provides supporting framework Reticular fibers Reticular tissue from liver LM  375 Reticular Tissue 85

4-4 Connective Tissue 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

4-4 Connective Tissue 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

Figure 4-11a Dense Connective Tissues
Dense Regular Connective Tissue LOCATIONS: Between skeletal muscles and skeleton (tendons and aponeuroses); between bones or stabilizing positions of internal organs (ligaments); covering skeletal muscles; deep fasciae Collagen fibers FUNCTIONS: Provides firm attachment; conducts pull of muscles; reduces friction between muscles; stabilizes relative positions of bones Fibroblast nuclei Tendon LM  440 88

4-4 Connective Tissue 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)

Figure 4-11b Dense Connective Tissues
Dense Irregular Connective Tissue LOCATIONS: Capsules of visceral organs; periostea and perichondria; nerve and muscle sheaths; dermis FUNCTIONS: Provides strength to resist forces applied from many directions; helps prevent overexpansion of organs such as the urinary bladder Collagen fiber bundles Deep dermis LM  111 90

4-4 Connective Tissue Elastic Tissue Made of elastic fibers
For example, elastic ligaments of spinal vertebrae

Figure 4-11c Dense Connective Tissues
Elastic Tissue LOCATIONS: Between vertebrae of the spinal column (ligamentum flavum and ligamentum nuchae); ligaments supporting penis; ligaments supporting transitional epithelia; in blood vessel walls Elastic fibers FUNCTIONS: Stabilizes positions of vertebrae and penis; cushions shocks; permits expansion and contraction of organs Fibroblast nuclei Elastic ligament LM  887 92

4-4 Connective Tissue 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

4-4 Connective Tissue Fluid Elements of Connective Tissues
Extracellular Plasma Interstitial fluid Lymph

Figure 4-12 Formed Elements of the Blood
Red blood cells Red blood cells, or erythrocytes (e-RITH-ro-sıts), are responsible for the transport of oxygen (and, to a lesser degree, of carbon dioxide) in the blood. Red blood cells account for roughly half the volume of whole blood and give blood its color. 95

White blood cells White blood cells, or leukocytes (LOO-ko-sıts; leuko-, white), help defend the body from infection and disease. Neutrophil Basophil Eosinophil Monocytes are phagocytes similar to the free macrophages in other tissues. Lymphocytes are un- common in the blood but they are the domi- nant cell type in lymph, the second type of fluid connective tissue. Eosinophils and neutrophils are phagocytes. Ba- sophils promote inflammation much like mast cells in other connective tissues. 96

Platelets Platelets are membrane-enclosed packets of cytoplasm that function in blood clotting. These cell fragments are involved in the clotting response that seals leaks in damaged or broken blood vessels. 97

4-4 Connective Tissue Lymph Extracellular fluid
Collected from interstitial space Monitored by immune system Transported by lymphatic (lymphoid) system Returned to venous system

4-4 Connective Tissue Fluid Tissue Transport Systems
Cardiovascular system (blood) Arteries Capillaries Veins Lymphatic (lymphoid) system (lymph) Lymphatic vessels

4-5 Supporting 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

Cartilage Matrix Proteoglycans derived from chondroitin sulfates Ground substance proteins Chondrocytes (cartilage cells) surrounded by lacunae (chambers)

Cartilage Structure No blood vessels Chondrocytes produce antiangiogenesis factor Perichondrium Outer, fibrous layer (for strength) Inner, cellular layer (for growth and maintenance)

Figure 4-13a The Growth of Cartilage
Matrix New matrix Chondrocyte Lacuna Chondrocyte undergoes division within a lacuna surrounded by cartilage matrix. As daughter cells secrete additional matrix, they move apart, expanding the cartilage from within. Interstitial growth 103

Figure 4-13b The Growth of Cartilage
Fibroblast Dividing stem cell Perichondrium New matrix Chondroblasts Immature chondrocyte Older matrix Mature chondrocyte Cells in the cellular layer of the perichondrium differentiate into chondroblasts. These immature chondroblasts secrete new matrix. As the matrix enlarges, more chondroblasts are incorporated; they are replaced by divisions of stem cells in the perichondrium. Appositional growth 104

Types of Cartilage Hyaline cartilage Elastic cartilage Fibrocartilage (fibrous 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

Fibrocartilage (Fibrous Cartilage) Limits movement Prevents bone-to-bone contact Pads knee joints Found between pubic bones and intervertebral discs

Figure 4-14a Types of Cartilage
Hyaline Cartilage LOCATIONS: Between tips of ribs and bones of sternum; covering bone surfaces at synovial joints; supporting larynx (voice box), trachea, and bronchi; forming part of nasal septum FUNCTIONS: Provides stiff but somewhat flexible support; reduces friction between bony surfaces Chondrocytes in lacunae Matrix LM  500 Hyaline cartilage 108

Figure 4-14b Types of Cartilage
Elastic Cartilage LOCATIONS: Auricle of external ear; epiglottis; auditory canal; cuneiform cartilages of larynx FUNCTIONS: Provides support, but tolerates distortion without damage and returns to original shape Chondrocyte in lacuna Elastic fibers in matrix LM  358 Elastic cartilage 109

Figure 4-14c Types of Cartilage
Fibrocartilage LOCATIONS: Pads within knee joint; between pubic bones of pelvis; intervertebral discs FUNCTIONS: Resists compression; prevents bone- to-bone contact; limits movement Chondrocytes in lacunae Fibrous matrix LM  400 Fibrocartilage 110

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

Figure 4-15 Bone 112 LM  375 Fibrous layer Canaliculi Periosteum
Cellular layer Osteocytes in lacunae Matrix Osteon Central canal Blood vessels Osteon LM  375 112

Table 4-2 A Comparison of Cartilage and Bone
113

4-6 Membranes Membranes Physical barriers
Line or cover portions of the body Consist of: An epithelium Supported by connective tissue

4-6 Membranes Four Types of Membranes Mucous membranes
Serous membranes Cutaneous membrane Synovial membranes

4-6 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

Figure 4-16a Membranes Mucous secretion Epithelium Lamina propria (areolar tissue) Mucous membranes are coated with the secretions of mucous glands. These membranes line the digestive, respiratory, urinary, and reproductive tracts. 117

4-6 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

4-6 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

Figure 4-16b Membranes Transudate Mesothelium Areolar tissue Serous membranes line the ventral body cavities (the peritoneal, pleural, and pericardial cavities). 120

4-6 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

The cutaneous membrane, or skin, covers the outer surface of the body.
Figure 4-16c Membranes Epithelium Areolar tissue Dense irregular connective tissue The cutaneous membrane, or skin, covers the outer surface of the body. 122

Figure 4-16d Membranes Articular (hyaline) tissue Synovial fluid Capsule Capillary Adipocytes Areolar tissue Synovial membrane Epithelium Bone Synovial membranes line joint cavities and produce the fluid within the joint. 123

4-7 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 = fascia The body’s framework of connective tissue Layers and wrappings that support or surround organs

4-7 Internal Framework of the Body
Three Types of Fasciae Superficial fascia Deep fascia Subserous fascia

Connective Tissue Framework of Body
Figure The Fasciae Body wall Connective Tissue Framework of Body Body cavity Superficial Fascia • Between skin and underlying organs • Areolar tissue and adipose tissue • Also known as subcutaneous layer or hypodermis Skin Deep Fascia • Forms a strong, fibrous internal framework • Dense connective tissue • Bound to capsules, tendons, and ligaments Subserous Fascia • Between serous membranes and deep fascia • Areolar tissue Rib Serous membrane Cutaneous membrane 126

4-8 Muscle Tissue Muscle Tissue Specialized for contraction
Produces all body movement Three types of muscle tissue Skeletal muscle tissue Large body muscles responsible for movement Cardiac muscle tissue Found only in the heart Smooth muscle tissue Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive, and reproductive tracts)

4-8 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)

4-8 Muscle Tissue Skeletal Muscle Cells Long and thin
Usually called muscle fibers Do not divide New fibers are produced by stem cells (myosatellite cells)

Figure 4-18a Muscle Tissue
Skeletal Muscle Tissue Cells are long, cylindrical, striated, and multinucleate. LOCATIONS: Combined with connective tissues and neural tissue in skeletal muscles Nuclei FUNCTIONS: Moves or stabilizes the position of the skeleton; guards entrances and exits to the digestive, respiratory, and urinary tracts; generates heat; protects internal organs Muscle fiber Striations LM  180 Skeletal muscle 130

4-8 Muscle Tissue Cardiac Muscle Cells Smooth Muscle Cells
Called cardiocytes Form branching networks connected at intercalated discs Regulated by pacemaker cells Smooth Muscle Cells Small and tapered Can divide and regenerate

Figure 4-18b Muscle Tissue
Cardiac Muscle Tissue Cells are short, branched, and striated, usually with a single nucleus; cells are interconnected by intercalated discs. Nucleus Cardiac muscle cells LOCATION: Heart FUNCTIONS: Circulates blood; maintains blood (hydrostatic) pressure Intercalated discs Striations LM  450 Cardiac muscle 132

Figure 4-18c Muscle Tissue
Smooth Muscle Tissue Cells are short, spindle-shaped, and nonstriated, with a single, central nucleus. LOCATIONS: Found in the walls of blood vessels and in digestive, respiratory, urinary, and reproductive organs Nucleus FUNCTIONS: Moves food, urine, and reproductive tract secretions; controls diameter of respiratory passageways; regulates diameter of blood vessels Smooth muscle cell Smooth muscle LM  235 133

4-9 Neural 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 is concentrated in the central nervous system Brain Spinal cord

4-9 Neural Tissue Two Types of Neural Cells Neurons Neuroglia
Nerve cells Perform electrical communication Neuroglia Supporting cells Repair and supply nutrients to neurons

4-9 Neural Tissue Cell Parts of a Neuron Cell body Dendrites
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

NEUROGLIA (supporting cells)
Figure Neural Tissue NEURONS NEUROGLIA (supporting cells) Nuclei of neuroglia • Maintain physical structure of tissues Cell body • Repair tissue framework after injury • Perform phagocytosis • Provide nutrients to neurons • Regulate the composition of the Axon interstitial fluid surrounding neurons Dendrites Nucleolus Nucleus of neuron LM  600 Dendrites (contacted by other neurons) Axon (conducts information to other cells) Microfibrils and microtubules Mitochondrion Nucleolus Nucleus Contact with other cells Cell body (contains nucleus and major organelles) A representative neuron (sizes and shapes vary widely) 137

Nuclei of neuroglia Cell body Axon Dendrites Nucleolus
Figure Neural Tissue Nuclei of neuroglia Cell body Axon Dendrites Nucleolus Nucleus of neuron LM  600 138

NEUROGLIA (supporting cells)
Figure Neural Tissue NEUROGLIA (supporting cells) • Maintain physical structure of tissues • Repair tissue framework after injury • Perform phagocytosis • Provide nutrients to neurons • Regulate the composition of the interstitial fluid surrounding neurons 139

Dendrites (contacted by other neurons)
Figure Neural Tissue Dendrites (contacted by other neurons) Axon (conducts information to other cells) Microfibrils and microtubules Mitochondrion Nucleolus Nucleus Contact with other cells Cell body (contains nucleus and major organelles) A representative neuron (sizes and shapes vary widely) 140

4-10 Tissue Injuries and Repair
Tissues Respond to Injuries To maintain homeostasis Cells restore homeostasis with two processes Inflammation Regeneration

Inflammation = Inflammatory Response The tissue’s first response to injury Signs and symptoms of the inflammatory response include: Swelling Redness Heat Pain

Inflammatory Response Can be triggered by: Trauma (physical injury) Infection (the presence of harmful pathogens)

The Process of Inflammation Damaged cells release chemical signals into the surrounding interstitial fluid Prostaglandins Proteins Potassium ions

The Process of Inflammation As cells break down: Lysosomes release enzymes that destroy the injured cell and attack surrounding tissues Tissue destruction is called necrosis

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

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

The Process of Inflammation Plasma diffuses into the area Causes swelling and pain Phagocytic white blood cells Clean up the area

Regeneration When the injury or infection is cleaned up Healing (regeneration) begins The Process of Regeneration Fibrocytes move into necrotic area Lay down collagen fibers To bind the area together (scar tissue)

The Process of Regeneration 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)

Mast Cell Activation Exposure to Pathogens and Toxins Mast cell
Figure Tissue Repair Mast Cell Activation When an injury damages connective tissue, mast cells release a variety of chemicals. This process, called mast cell activation, stimulates inflammation. Mast cell stimulates Exposure to Pathogens and Toxins Injured tissue contains an abnormal concentration of pathogens, toxins, waste products, and the chemicals from injured cells. When a tissue is injured, a general defense mechanism is activated. 151

INFLAMMATION Mast Cell Activation Increased Blood Flow
Figure Tissue Repair Mast Cell Activation When an injury damages connective tissue, mast cells release a variety of chemicals. This process, called mast cell activation, stimulates inflammation. Mast cell Histamine Heparin Prostaglandins INFLAMMATION Inflammation produces several familiar indications of injury, including swelling, redness, warmth, and pain. Inflammation may also result from the presence of pathogens, such as harmful bacteria, within the tissues; the presence of these pathogens constitutes an infection. Increased Blood Flow Increased Vessel Permeability Pain In response to the released chemicals, blood vessels dilate, increasing blood flow through the damaged tissue. Vessel dilation is accompanied by an increase in the permeability of the capillary walls. Plasma now diffuses into the injured tissue, so the area becomes swollen. The abnormal conditions within the tissue and the chemicals released by mast cells stimulate nerve endings that produce the sensation of pain. PAIN 152

Inflammation Subsides
Figure Tissue Repair Increased Local Temperature Increased Oxygen and Nutrients Increased Phagocytosis Removal of Toxins and Wastes The increased blood flow and permeability causes the tissue to become warm and red. Vessel dilation, increased blood flow, and increased vessel permeability result in enhanced delivery of oxygen and nutrients. Phagocytes in the tissue are activated, and they begin engulfing tissue debris and pathogens. Enhanced circulation carries away toxins and waste products, distributing them to the kidneys for excretion, or to the liver for inactivation. O2 Toxins and wastes Regeneration Regeneration is the repair that occurs after the damaged tissue has been stabilized and the inflammation has subsided. Fibroblasts move into the area, laying down a collagenous framework known as scar tissue. Over time, scar tissue is usually “remodeled” and gradually assumes a more normal appearance. Inflammation Subsides Over a period of hours to days, the cleanup process generally succeeds in eliminating the inflammatory stimuli. 153

Normal tissue conditions restored
Figure Tissue Repair Normal tissue conditions restored Regeneration Regeneration is the repair that occurs after the damaged tissue has been stabilized and the inflammation has subsided. Fibroblasts move into the area, laying down a collagenous framework known as scar tissue. Over time, scar tissue is usually “remodeled” and gradually assumes a more normal appearance. Inhibits mast cell activation 154

4-11 Aging and Tissue Aging and Tissue Structure
Speed and efficiency of tissue repair decrease with age, due to: Slower rate of energy consumption (metabolism) Hormonal alterations Reduced physical activity

4-11 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

4-11 Aging and Tissue Aging and Cancer Incidence
Cancer rates increase with age 25% of all people in the United States develop cancer Cancer is the #2 cause of death in the United States Environmental chemicals and cigarette smoke cause cancer

4 The Tissue Level of Organization.

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4 The Tissue Level of Organization.

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