2. 4 The Tissue Level of Organization C h a p t e r
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris

3. 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
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4. 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
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5. Epithelial Tissues Epithelia Glands
Layers of cells covering internal or external surfaces
Glands
Structures that produce secretions
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6. Epithelial Tissues Characteristics of Epithelia
Cellularity (cell junctions)
Polarity (apical and basal surfaces)
Attachment (basal lamina)
Avascularity
Regeneration
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7. Epithelial Tissues Figure 4–1 The Polarity of Epithelial Cells.
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8. Epithelial Tissues Functions of Epithelial Tissue
Provide physical protection
Control permeability
Provide sensation
Produce specialized secretions (glandular epithelium)
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9. 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
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10. Epithelial Tissues Maintaining the Integrity of Epithelia
Intercellular connections
Attachment to basal lamina
Epithelial maintenance and repair
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11. Epithelial Tissues Intercellular Connections Support and communication
CAMs (cell adhesion molecules):
transmembrane proteins
Intercellular cement:
proteoglycans
Hyaluronan (hyaluronic acid):
glycosaminoglycans
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12. Epithelial Tissues Intercellular Connections Cell junctions
Form bonds with other cells or extracellular material:
occluding (tight) junctions
gap junctions
macula adherens (desmosomes)
Intercellular Connections
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13. Epithelial Tissues Cell Junctions
Occluding (Tight) junctions—between two plasma membranes
Adhesion belt attaches to terminal web
Prevents passage of water and solutes
Isolates wastes in the lumen
Gap junctions—allow rapid communication
Held together by channel proteins (junctional proteins, connexons)
Allow ions to pass
Coordinate contractions in heart muscle
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14. Epithelial Tissues Cell Junctions Macula adherens (Desmosomes)
CAMs, dense areas, and intercellular cement
Spot desmosomes
tie cells together
allow bending and twisting
Hemidesmosomes
attach cells to the basal lamina
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15. Epithelial Tissues Attachment to the Basal Lamina
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
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16. Epithelial Tissues Figure 4–2 Intercellular Connections
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17. Epithelial Tissues Figure 4–2 Intercellular Connections
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18. Epithelial Tissues Figure 4–2 Intercellular Connections
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19. Epithelial Tissues Figure 4–2 Intercellular Connections
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20. Epithelial Tissues Epithelial Maintenance and Repair
Epithelia are replaced by division of germinative cells (stem cells)
Near basal lamina
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21. 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
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22. Classification of Epithelia
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23. Classification of Epithelia
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24. Classification of Epithelia
Squamous Epithelia
Simple squamous epithelium
Absorption and diffusion
Mesothelium
Lines body cavities
Endothelium
Lines heart and blood vessels
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25. Classification of Epithelia
Figure 4–3 Squamous Epithelia.
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26. Classification of Epithelia
Squamous Epithelia
Stratified squamous epithelium
Protects against attacks
Keratin protein adds strength and water resistance
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27. Classification of Epithelia
Figure 4–3 Squamous Epithelia.
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28. Classification of Epithelia
Cuboidal Epithelia
Simple cuboidal epithelium
Secretion and absorption
Stratified cuboidal epithelia
Sweat ducts and mammary ducts
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29. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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30. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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31. 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)
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32. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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33. Classification of Epithelia
Columnar Epithelia
Simple columnar epithelium
Absorption and secretion
Pseudostratified columnar epithelium
Cilia movement
Stratified columnar epithelium
Protection
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34. Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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35. Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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36. Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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37. Classification of Epithelia
Glandular Epithelia
Endocrine glands
Release hormones:
into interstitial fluid
no ducts
Exocrine glands
Produce secretions:
onto epithelial surfaces
through ducts
Mechanisms of Glandular Secretion
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38. 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 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
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39. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.
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40. Classification of Epithelia
Figure 4–6a Modes of Glandular Secretion.
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41. Classification of Epithelia
Figure 4–6b Modes of Glandular Secretion.
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42. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.
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43. Classification of Epithelia
Glandular Epithelia
Types of secretions
Serous glands:
watery secretions
Mucous glands:
secrete mucins
Mixed exocrine glands:
both serous and mucous
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44. 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
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45. 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)
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46. Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.
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47. Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.
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48. 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
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49. 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
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50. Connective Tissues Classification of Connective Tissues
Connective tissue proper
Connect and protect
Fluid connective tissues
Transport
Supportive connective tissues
Structural strength
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51. Connective Tissues 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
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52. Connective Tissues Nine Cell Types of Connective Tissue Proper
Fibroblasts
Fibrocytes
Macrophages
Adipocytes
Mesenchymal cells
Melanocytes
Mast cells
Lymphocytes
Microphages
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53. 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:
maintain the fibers of connective tissue proper
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54. 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.
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55. 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
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56. 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
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57. 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
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58. 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
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59. Connective Tissues Connective Tissue Fibers Elastic fibers
Contain elastin
Branched and wavy
Return to original length after stretching
For example, elastic ligaments of vertebrae
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60. Connective Tissues Ground Substance Is clear, colorless, and viscous
Fills spaces between cells and slows pathogen movement
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61. Connective Tissues
Figure 4–8 The Cells and Fibers of Connective Tissue Proper.
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62. Connective Tissues
Figure 4–8 The Cells and Fibers of Connective Tissue Proper.
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63. 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
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64. Connective Tissues Figure 4–9 Connective Tissues in Embryos.
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65. Connective Tissues Figure 4–9 Connective Tissues in Embryos.
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66. Connective Tissues Loose Connective Tissues
The packing materials of the body
Three types in adults
Areolar
Adipose
Reticular
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67. 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)
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68. 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
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69. 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
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70. 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
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71. Connective Tissues Figure 4–10 Adipose and Reticular Tissues.
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