The Tissue Level of Organization

Transcription

1 PowerPoint Lecture Slides prepared by Meg Flemming Austin Community College C H A P T E R 4 The Tissue Level of Organization

2 Chapter 4 Learning Outcomes Identify the body's four basic types of tissues and describe their roles. Describe the characteristics and functions of epithelial cells. Describe the relationship between form and function for each type of epithelium. Compare the structures and functions of the various types of connective tissues.

3 Chapter 4 Learning Outcomes Explain how epithelial and connective tissues combine to form four types of tissue membranes, and specify the functions of each. Describe the three types of muscle tissue and the special structural features of each. Discuss the basic structure and role of neural tissue. Explain how injuries affect the tissues of the body. Describe how aging affects the tissues of the body.

4 Tissues (4-1) Collections of cells and cell products that perform specific, limited functions Histology The study of tissues Four types of tissues 1. Epithelial 2. Connective 3. Muscle 4. Neural

5 Figure 4-1 An Orientation to the Tissues of the Body. CELLS That secrete and regulate Combine to form EXTRACELLULAR MATERIAL AND FLUIDS EPITHELIAL TISSUE Covers exposed surfaces Lines internal passageways and chambers Produces glandular secretions TISSUES with special functions Combine to form ORGANS with multiple functions Interact in ORGAN SYSTEMS Chapters 5 20 CONNECTIVE TISSUE Fills internal spaces Provides structural support Stores energy MUSCLE TISSUE Contracts to produce active movement NEURAL TISSUE Conducts electrical Impulses Carries information

6 Checkpoint (4-1) 1. Define histology. 2. List the four basic types of tissues in the body.

7 Epithelial Tissue (4-2) Covers body surfaces Lines cavities Lines tubular structures Serves essential functions

8 Characteristics of Epithelial Tissue (4-2) Cellularity (cell junctions) Polarity (apical and basal surfaces) Attachment Avascularity Regeneration

9 Functions of Epithelia (4-2) Provide physical protection Control permeability Provide sensation Produce specialized secretions (glandular epithelium) Exocrine glands Endocrine glands

10 Intercellular Connections (4-2) Support and communication Cell adhesion molecules (CAMs) Transmembrane proteins Intercellular cement Proteoglycans

11 Three Common Cell Junctions (4-2) 1. Tight junctions 2. Gap junctions 3. Desmosomes Form bonds with other cells or extracellular material

12 Figure 4-2a Cell Junctions. Tight junction Adhesion belt Spot desmosome Gap junctions This is a Diagrammatic view of an epithelial cell, showing the major types of Intercellular connections. Hemidesmosome

13 Figure 4-2b Cell Junctions. Interlocking junctional proteins Tight junction Tight junction Adhesion belt Spot desmosome Adhesion belt Gap junctions Hemidesmosome 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 deep to the tight junction is tied to the microfilaments of the cytoskeleton.

14 Figure 4-2c Cell Junctions. Tight junction Adhesion belt Spot desmosome Gap junctions Hemidesmosome Embedded proteins (connexons) Gap junctions permit the free diffusion of ions and small molecules between two cells.

15 Figure 4-2d-e Cell Junctions. Gap junctions Hemidesmosome Tight junction Adhesion belt Spot desmosome Gap junctions Tight junction Adhesion belt Spot desmosome Hemidesmosome Intermediate filaments Dense area Proteoglycans Cell adhesion molecules (CAMs) A spot desmosome ties adjacent cells together. Basement membrane Hemidesmosomes attach a cell to extracellular structures, such as the protein fibers in the basement membrane.

16 The Epithelial Surface (4-2) Apical surface is exposed Basal surface is connected to deeper connective tissue with basement membrane

17 Figure 4-3 The Surfaces of Epithelial Cells. Cilia Microvilli Apical surface Golgi apparatus Nucleus Mitochondria Basement membrane

18 Epithelial Renewal and Repair (4-2) Epithelia are replaced by mitosis Cell division of stem cells (germinative cells) Occurs near basement membrane

19 Checkpoint (4-2) 3. List five important characteristics of epithelial tissue. 4. Identify four essential functions of epithelial tissue. 5. Identify the three main types of epithelial cell junctions. 6. What physiological functions are enhanced by the presence of microvilli or cilia on epithelial cells?

20 Classification of Epithelia (4-3) Combines a cell shape with the number of layers of cells Example: Simple (one layer) cuboidal (square shape)

21 Cell Layers and Cell Shapes (4-3) Classification is based on layers Simple epithelium: single layer of cells Stratified epithelium: several layers of cells Classification is based on shape Squamous epithelia: thin and flat Cuboidal epithelia: square shaped Columnar epithelia: tall, slender rectangles

22 Table 4-1 Classifying Epithelia

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

24 Figure 4-4b Simple Epithelia. Simple Cuboidal Epithelium LOCATIONS: Glands; ducts; portions of kidney tubules; thyroid gland FUNCTIONS: Limited protection, secretion, absorption Connective tissue Nucleus Cuboidal cells Basement membrane Kidney tubule LM x 650

25 Figure 4-4c Simple Epithelia. Simple Columnar Epithelium LOCATIONS: Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys FUNCTIONS: Protection, secretion, absorption Microvilli Cytoplasm Nucleus Intestinal lining Basement membrane Connective tissue LM x 350

26 Figure 4-5a Stratified 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 Surface of tongue tissue LM x 310

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

28 Figure 4-5c Stratified Epithelia. Transitional Epithelium LOCATIONS: Urinary bladder; renal pelvis; ureters FUNCTIONS: Permits expansion and recoil after stretching Empty bladder Epithelium (relaxed) Basement membrane Connective tissue and smooth muscle layers LM x 400 Epithelium (stretched) Basement membrane Connective tissue and Full bladder smooth muscle layers Urinary bladder LM x 400

29 Glandular Epithelia (4-3) Endocrine glands Release hormones: Into interstitial fluid and plasma No ducts Exocrine glands Produce secretions: Onto epithelial surfaces Through ducts

30 Glandular Secretion (4-3) Merocrine secretion Produced in Golgi apparatus Released by vesicles (exocytosis) Example: sweat glands Apocrine secretion Produced in Golgi apparatus Released by shedding cytoplasm Example: mammary glands

31 Glandular Secretion (4-3) Holocrine secretion Released by cells bursting, killing gland cells Gland cells replaced by stem cells Example: sebaceous glands

32 Figure 4-6 Mechanisms of Glandular Secretion. Secretory vesicle Golgi apparatus Nucleus Salivary gland TEM x 3039 Merocrine. In merocrine secretion, the contents of secretory vesicles are discharged at the apical surface of the gland cell by exocytosis. Mammary gland Breaks down Golgi apparatus Secretion Regrowth Hair Sebaceous gland Hair follicle 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. Cells burst, releasing cytoplasmic contents Cells produce secretion, increasing in size Cell division replaces lost cells Stem cell 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.

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

34 Figure 4-6b Mechanisms of Glandular Secretion. Salivary gland Mammary gland Breaks down Golgi apparatus Secretion Regrowth Hair 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. Sebaceous gland Hair follicle

35 Figure 4-6c Mechanisms of Glandular Secretion. Salivary gland Mammary gland Hair Sebaceous gland Hair follicle Cells burst, releasing cytoplasmic contents Cells produce secretion, increasing in size Cell division replaces lost cells Stem cell 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.

36 Types of Secretion (4-3) Serous glands Watery secretions Mucous glands Secrete mucins Mixed exocrine glands Both serous and mucous

37 Table 4-2 A Classification of Exocrine Glands

38 Checkpoint (4-3) 7. Identify the three cell shapes characteristic of epithelial cells. 8. Using a light microscope, you examine a tissue and see a simple squamous epithelium on the outer surface. Can this be a sample of skin surface? 9. Name the two primary types of glandular epithelia.

39 Checkpoint (4-3) 10.The secretory cells of sebaceous glands fill with secretions and then rupture, releasing their contents. Which mechanism of secretion occurs in sebaceous glands? 11.Which type of gland releases its secretions directly into the extracellular fluid?

40 Connective Tissue (4-4) Provides a protective structural framework for other tissue types Three basic components 1. Specialized cells 2. Solid extracellular protein fibers 3. Fluid extracellular ground substance

41 Characteristics of Connective Tissue (4-4) The extracellular components of connective tissues (fibers and ground substance) make up the matrix Majority of tissue volume Determines specialized function

42 Functions of Connective Tissue (4-4) Support and protection Transportation of materials Storage of energy reserves Defense of the body

43 Figure 4-7 Major Types of Connective Tissue. CONNECTIVE TISSUES CONNECTIVE TISSUE PROPER FLUID CONNECTIVE TISSUES SUPPORTING CONNECTIVE TISSUES LOOSE DENSE BLOOD LYMPH CARTILAGE BONE Fibers create loose, open framework Fibers densely packed Flows within cardiovascular system Flows within lymphatic system Solid, rubbery matrix Solid, crystalline matrix

44 Three Major Types of Connective Tissue (4-4) 1. Connective tissue proper 2. Fluid connective tissues 3. Supporting connective tissues

45 Cells of Connective Tissue Proper (4-4) Fibroblasts Most abundant cells in connective tissue proper Produce connective tissue fibers and ground substance Macrophages Scattered throughout the matrix Phagocytize damaged cells or pathogens that enter the tissue Release chemicals that mobilize the immune system

46 Cells of Connective Tissue Proper (4-4) Fat cells (adipocytes) Permanent residents Number of fat cells vary Mast cells Small, mobile cells often found near blood vessels Cytoplasm is packed with vesicles Filled with chemicals that are released to begin body's defensive activities after an injury or infection

47 Three Basic Types of Connective Tissue Fibers (4-4) 1. Collagen fibers Long, straight, unbranched Strong, but flexible Most common 2. Elastic fibers Branched and wavy After stretching, they will return to their original length Contain the protein elastin

48 Three Basic Types of Connective Tissue Fibers (4-4) 3. Reticular fibers Made of same protein subunits as collagen fibers, but arranged differently Thinner than collagen fibers Form branching, interwoven framework in various organs Least common

49 Ground Substance (4-4) Clear, colorless, and viscous Fills spaces between cells and slows pathogen movement

50 Types of Connective Tissue Proper (4-4) Loose connective tissue "Packing materials" of the body More ground substance, fewer fibers Example: fat (adipose tissue) Dense connective tissue Tough, strong, and durable More fibers, less ground substance Example: tendons

51 Figure 4-8 Cells and Fibers of Connective Tissue Proper. Reticular fibers Fixed macrophage Antibody producing cell Blood in vessel Mast cell Elastic fibers Free macrophage Collagen fibers Fibroblast Stem cell Adipocytes (fat cells) Ground substance White blood cell

52 Figure 4-9a Loose Connective Tissues. Areolar Tissue LOCATIONS: Beneath dermis of skin, digestive tract, respiratory and urinary tracts; between muscles; around blood vessels, nerves, and around joints FUNCTIONS: Cushions organs; provides support but permits independent movement; phagocytic cells provide defense against pathogens Mast cell Areolar tissue Collagen fibers Fat cell Fibroblasts Elastic fibers Macrophage LM x 400

53 Figure 4-9b Loose Connective 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 Adipose tissue Adipocytes LM x 300

54 Figure 4-9c Loose Connective Tissues. Reticular Tissue LOCATIONS: Liver, kidney, spleen, lymph nodes, and bone marrow FUNCTIONS: Provides supporting framework Reticular fibers Reticular tissue from liver Reticular tissue LM x 375

55 Figure 4-10a 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 FUNCTIONS: Provides firm attachment; conducts pull of muscles; reduces friction between muscles; stabilizes relative positions of bones Collagen fibers Fibroblast nuclei Tendon LM x 440

56 Figure 4-10b Dense Connective Tissues. Dense Irregular Connective Tissue LOCATIONS: Capsules of visceral organs; periostea and perichondria; nerve and muscle sheaths; deep dermis of the skin 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 x 111

57 Fluid Connective Tissues (4-4) Blood and lymph Watery matrix of dissolved proteins Carry specific cell types (formed elements) Formed elements of blood Red blood cells White blood cells Platelets

58 Supporting Connective Tissues (4-4) Cartilage Gel-type ground substance For shock absorption and protection Bone Calcified (made rigid by calcium salts, minerals) For weight support

59 Cartilage (4-4) Cartilage matrix Proteoglycans derived from chondroitin sulfates Ground substance proteins Chondrocytes (cartilage cells) Surrounded by lacunae (chambers)

60 Cartilage Structure (4-4) Avascular Chondrocytes found in pockets called lacunae Perichondrium Outer, fibrous layer (for strength) Inner, cellular layer (for growth and maintenance)

61 Three Major Types of Cartilage (4-4) 1. Hyaline cartilage Stiff, flexible support Reduces friction between bones Found in synovial joints, rib tips, sternum, and trachea 2. Elastic cartilage Supportive but bends easily Found in external ear and epiglottis 3. Fibrocartilage Limits movement Prevents bone-to-bone contact Pads knee joints Found between pubic bones and intervertebral discs

62 Figure 4-11a 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 Hyaline cartilage Chondrocytes in lacunae Matrix LM x 500

63 Figure 4-11b 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 Elastic cartilage Chondrocyte In lacuna Elastic fibers in matrix LM x 358

64 Figure 4-11c 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 Fibrocartilage Chondrocytes in lacunae Fibrous matrix LM x 400

65 Bone (4-4) Or osseous tissue Strong (hard calcium compounds) Resists shattering (flexible collagen fibers) Bone cells or osteocytes Arranged around central canals within matrix Small channels through matrix (canaliculi) access blood supply

66 Periosteum (4-4) Covers bone surfaces Fibrous layer Cellular layer

67 Figure 4-12 Bone. Osteon Canaliculi Lacunae (contain osteocytes) Matrix Central canal Fibrous layer Cellular layer Periosteum Blood vessels Osteon LM x 375

68 Table 4-3 A Comparison of Cartilage and Bone

69 Checkpoint (4-4) 12.Identify several functions of connective tissues. 13.List the three types of connective tissues. 14.Which type of connective tissue contains primarily triglycerides? 15.Lack of vitamin C in the diet interferes with the ability of fibroblasts to produce collagen. What effect might this interference have on connective tissue? 16.Which two types of connective tissue have a fluid matrix?

70 Checkpoint (4-4) 17. Identify the two types of supporting connective tissue. 18. Why does cartilage heal slower than bone?

71 Tissue Membranes (4-5) Membranes Are physical barriers Line or cover portions of the body Consist of: An epithelium Supported by connective tissues

72 Four Types of Tissue Membranes (4-5) 1. Mucous membranes 2. Serous membranes 3. Cutaneous membrane 4. Synovial membranes

73 Figure 4-13 Tissue Membranes. Mucous membranes are coated with the secretions of mucous glands. These membranes line the digestive, respiratory, urinary, and reproductive tracts. Mucous secretion Epithelium Lamina propria (areolar tissue) Serous membranes line the ventral body cavities (the peritoneal, pleural, and pericardial cavities). Serous fluid Epithelium Areolar tissue The cutaneous membrane, or skin, covers the outer surface of the body. Synovial membranes line joint cavities and produce the fluid within the joint. Epithelium Areolar tissue Dense irregular connective tissue Articular (hyaline) cartilage Synovial fluid Capsule Capillary Adipocytes Areolar tissue Epithelium Synovial membrane Bone

74 Mucous Membranes (4-5) Also known as 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 Made of areolar tissue

75 Figure 4-13a Tissue Membranes. Mucous membranes are coated with the secretions of mucous glands. These membranes line the digestive, respiratory, urinary, and reproductive tracts. Mucous secretion Epithelium Lamina propria (areolar tissue)

76 Serous Membranes (4-5) 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

77 Three Serous Membranes (4-5) 1. Pleura Lines pleural cavities Covers lungs 2. Peritoneum Lines peritoneal cavity Covers abdominal organs 3. Pericardium Lines pericardial cavity Covers heart

78 Figure 4-13b Tissue Membranes. Serous membranes line the ventral body cavities (the peritoneal, pleural, and pericardial cavities). Serous fluid Epithelium Areolar tissue

79 The Cutaneous Membrane (4-5) Is skin Covers the surface of the body Thick, waterproof, and dry

80 Figure 4-13c Tissue Membranes. The cutaneous membrane, or skin, covers the outer surface of the body. Epithelium Areolar tissue Dense irregular connective tissue

81 Synovial Membranes (4-5) Line moving, articulating joint cavities Produce synovial fluid (lubricant) Protect the ends of bones Lack a true epithelium

82 Figure 4-13d Tissue Membranes. Synovial membranes line joint cavities and produce the fluid within the joint. Articular (hyaline) cartilage Synovial fluid Capsule Capillary Adipocytes Areolar tissue Epithelium Synovial membrane Bone

83 Checkpoint (4-5) 19. Identify the four types of tissue membranes found in the body. 20. How does a plasma (cell) membrane differ from a tissue membrane? 21. What is the function of fluids produced by serous membranes? 22. The lining of the nasal cavity is normally moist, contains numerous mucous cells, and rests on a layer of areolar tissue. Which type of membrane is this?

84 Three Types of Muscle Tissue (4-6) 1. Skeletal muscle tissue Large body muscles responsible for movement 2. Cardiac muscle tissue Found only in the heart 3. Smooth muscle tissue Found in walls of blood vessels Found around hollow organs such as the urinary bladder Around the respiratory, digestive, and reproductive tracts

85 Functions of Muscle Tissue (4-6) Specialized for contraction Produces all body movement

86 Figure 4-14a Muscle Tissue. Skeletal Muscle Tissue Cells are long, cylindrical, striated, and multinucleate. LOCATIONS: Combined with connective tissues and neural tissue in skeletal muscles 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 Skeletal muscle Nuclei Muscle fiber Striations LM x 180

87 Figure 4-14b Muscle Tissue. Cardiac Muscle Tissue Cells are short, branched, and striated, usually with a single nucleus; cells are interconnected by intercalated discs. LOCATION: Heart FUNCTIONS: Circulates blood; maintains blood (hydrostatic) pressure Nucleus Cardiac muscle cells Intercalated discs Striations Cardiac muscle LM x 450

88 Figure 4-14c 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 FUNCTIONS: Moves food, urine, and reproductive tract secretions; controls diameter of respiratory passageways; regulates diameter of blood vessels Smooth muscle Nucleus Smooth muscle cell LM x 235

89 Checkpoint (4-6) 23. Identify the three types of muscle tissue in the body. 24. Voluntary control is restricted to which type of muscle tissue? 25. Which type of muscle tissue has small, tapering cells with single nuclei and no obvious striations?

90 Neural Tissue (4-7) Also called nervous or nerve tissue Specialized for conducting electrical impulses Rapidly senses internal or external environment Processes information and controls responses

91 Neural Tissue (4-7) Concentrated in the central nervous system Brain Spinal cord

92 Two Kinds of Neural Cells (4-7) 1. Neurons Nerve cells Perform electrical communication 2. Neuroglia Supporting cells Repair and supply nutrients to neurons

93 Cell Parts of a Neuron (4-7) Cell body 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

94 Figure 4-15 Neural Tissue. Brain Nuclei of neuroglia Cell body Axon terminals Spinal cord Cell body Nucleus of neuron Axon Dendrites Axon Neuron LM x 600 Photomicrograph of neuron cell body

95 Checkpoint (4-7) 26. A tissue contains irregularly shaped cells with many projections, including some several centimeters long. These are probably which type of cell? 27. Why are both skeletal muscle cells and axons also called fibers?

96 Tissue Injuries and Repair (4-8) Tissues respond to injuries to maintain homeostasis Cells restore homeostasis with two processes 1. Inflammation 2. Regeneration

97 Inflammation (4-8) Inflammatory response The tissue's first response to injury Signs and symptoms include: Swelling Heat Redness Pain

98 Inflammatory Response (4-8) Can be triggered by: Trauma (physical injury) Infection (the presence of harmful pathogens)

99 Checkpoint (4-8) 28. Identify the two phases in the response to tissue injury. 29. What signs and symptoms are associated with inflammation? 30. What is fibrosis?

100 Aging Tissue (4-9) With age: Rate of tissue repair declines Cancer rates increase

101 Aging and Tissue Structure (4-9) Speed and efficiency of tissue repair decrease with age due to: Slower rate of energy consumption (metabolism) Hormonal alterations Reduced physical activity

102 Aging and Cancer Incidence (4-9) Cancer rates increase with age 1 in 4 people in the United States develops cancer Cancer is the #2 cause of death in the United States Environmental chemicals and cigarette smoke cause cancer

103 Checkpoint (4-9) 31.Identify some age-related factors that affect tissue repair and structure.