1. Chapter 4
Tissues
Muse 2430 lecture #3
5/14/12

2. 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

3. 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

4. A little embryology

5. Cell Junctions
Contact points between the plasma membranes of tissue cells
5 most common types:
Tight junctions
Adherens junctions
Desmosomes
Hemidesmosomes
Gap junctions

6. 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

7. 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

8. Epithelial Tissues Epithelia Glands
Layers of cells covering internal or external surfaces
Glands
Structures that produce secretions

9. Epithelial Tissues Characteristics of Epithelia
Cellularity (cell junctions)
Polarity (apical and basal surfaces)
Attachment (basal lamina)
Avascularity
Regeneration

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

11. Epithelial Tissues Functions of Epithelial Tissue
Provide physical protection
Control permeability
Provide sensation
Produce specialized secretions (glandular epithelium)

12. 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

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

14. Epithelial Tissues Intercellular Connections Support and communication
CAMs (cell adhesion molecules):
transmembrane proteins
Intercellular cement:
proteoglycans
Hyaluronan (hyaluronic acid):
glycosaminoglycans

15. Epithelial Tissues Intercellular Connections Cell junctions
Form bonds with other cells or extracellular material:
occluding (tight) junctions
gap junctions
macula adherens (desmosomes)
Intercellular Connections

16. 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

17. 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

18. 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

19. Epithelial Tissues
Figure 4–2 Intercellular Connections

20. Epithelial Tissues
Figure 4–2 Intercellular Connections

21. Epithelial Tissues
Figure 4–2 Intercellular Connections

22. Epithelial Tissues
Figure 4–2 Intercellular Connections

23. Epithelial Tissues Epithelial Maintenance and Repair
Epithelia are replaced by division of germinative cells (stem cells)
Near basal lamina

24. 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

25. Classification of Epithelia

26. Classification of Epithelia

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

28. Classification of Epithelia
Figure 4–3 Squamous Epithelia.

29. Classification of Epithelia
Squamous Epithelia
Stratified squamous epithelium
Protects against attacks
Keratin protein adds strength and water resistance

30. Classification of Epithelia
Figure 4–3 Squamous Epithelia.

31. Classification of Epithelia
Cuboidal Epithelia
Simple cuboidal epithelium
Secretion and absorption
Stratified cuboidal epithelia
Sweat ducts and mammary ducts

32. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.

33. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.

34. 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)

35. Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.

36. Classification of Epithelia
Columnar Epithelia
Simple columnar epithelium
Absorption and secretion
Pseudostratified columnar epithelium
Cilia movement
Stratified columnar epithelium
Protection

37. Classification of Epithelia
Figure 4–5 Columnar Epithelia.

38. Classification of Epithelia
Figure 4–5 Columnar Epithelia.

39. Classification of Epithelia
Figure 4–5 Columnar Epithelia.

40. 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

41. 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

42. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.

43. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.

44. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.

45. Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.

46. Classification of Epithelia
Glandular Epithelia
Types of secretions
Serous glands:
watery secretions
Mucous glands:
secrete mucins
Mixed exocrine glands:
both serous and mucous

47. 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

48. 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)

49. Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.

50. Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.

51. 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

52. 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

53. Connective Tissues Classification of Connective Tissues
Connective tissue proper
Connect and protect
Fluid connective tissues
Transport
Supportive connective tissues
Structural strength

54. 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

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

56. 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

57. 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.

58. 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

59. 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

60. 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

61. 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

62. Connective Tissues Connective Tissue Fibers Elastic fibers
Contain elastin
Branched and wavy
Return to original length after stretching
For example, elastic ligaments of vertebrae

63. Connective Tissues Ground Substance Is clear, colorless, and viscous
Fills spaces between cells and slows pathogen movement

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

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

66. 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

67. Connective Tissues
Figure 4–9 Connective Tissues in Embryos.

68. Connective Tissues [INSERT FIG. 4.9b]
Figure 4–9 Connective Tissues in Embryos.

69. Connective Tissues Loose Connective Tissues
The packing materials of the body
Three types in adults
Areolar
Adipose
Reticular

70. 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)

71. 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

72. 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

73. 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

74. Connective Tissues
Figure 4–10 Adipose and Reticular Tissues.

75. Connective Tissues
Figure 4–10 Adipose and Reticular Tissues.

76. Connective Tissues 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

77. Connective Tissues 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

78. Connective Tissues
Figure 4–11 Dense Connective Tissues.

79. Connective Tissues 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)

80. Connective Tissues
Figure 4–11 Dense Connective Tissues.

81. Connective Tissues Elastic Tissue Made of elastic fibers
For example, elastic ligaments of spinal vertebrae

82. Connective Tissues
Figure 4–11 Dense Connective Tissues.

83. Connective Tissues 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

84. Connective Tissues Fluid Elements of Fluid Connective Tissues
Extracellular
Plasma
Interstitial fluid
Lymph

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

86. Connective Tissues Lymph Extracellular fluid
Collected from interstitial space
Monitored by immune system
Transported by lymphoid (lymphatic) system
Returned to venous system

87. Connective Tissues Fluid Tissue Transport Systems
Cardiovascular system (blood)
Arteries
Capillaries
Veins
Lymphoid (lymphatic) system (lymph)
Lymphatic vessels

88. 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

89. Supportive Connective Tissues
Cartilage Matrix
Proteoglycans derived from chondroitin sulfates
Ground substance proteins
Chondrocytes (cartilage cells) surrounded by lacunae (chambers)

90. Supportive Connective Tissues
Cartilage Structure
No blood vessels:
Chondrocytes produce antiangiogenesis factor
Perichondrium:
Outer, fibrous layer (for strength)
Inner, cellular layer (for growth and maintenance)

91. Supportive Connective Tissues
Figure 4–13 The Growth of Cartilage.

92. Supportive Connective Tissues
Figure 4–13 The Growth of Cartilage.

93. 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

94. Supportive Connective Tissues
Figure 4–14 The Types of Cartilage.

95. Supportive Connective Tissues
Figure 4–14 The Types of Cartilage.

96. Supportive Connective Tissues
Figure 4–14 The Types of Cartilage.

97. 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

98. Supportive Connective Tissues
Figure 4–15 Bone.

99. Supportive Connective Tissues

100. Membranes Membranes Are physical barriers
That line or cover portions of the body
Consist of
An epithelium
Supported by connective tissues

101. Membranes Four Types of Membranes Mucous membranes Serous membranes
Cutaneous membrane
Synovial membranes

102. 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

103. 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

104. 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

105. Membranes
Figure 4–16 Membranes.

106. 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

107. Membranes
Figure 4–16 Membranes.

108. 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

109. Internal Framework of the Body
Three Types of Fasciae
Superficial fascia
Deep fascia
Subserous fascia

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

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

112. 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)

113. Muscle Tissue Skeletal Muscle Cells Are long and thin
Are usually called muscle fibers
Do not divide
New fibers are produced by stem cells (myosatellite cells)

114. Muscle Tissue
Figure 4–18 Muscle Tissue.

115. Muscle Tissue Cardiac muscle cells Smooth muscle cells
Are called cardiocytes
Form branching networks connected at intercalated discs
Are regulated by pacemaker cells
Smooth muscle cells
Are small and tapered
Can divide and regenerate

116. Muscle Tissue
Figure 4–18 Muscle Tissue.

117. Muscle Tissue
Figure 4–18 Muscle Tissue.

118. Neural Tissue Also called nervous or nerve tissue
Specialized for conducting electrical impulses
Rapidly senses internal or external environment
Processes information and controls responses

119. Neural Tissue
Neural tissue is concentrated in the central nervous system
Brain
Spinal cord

120. Neural Tissue Two Kinds of Neural Cells Neurons Neuroglia Nerve cells
Perform electrical communication
Neuroglia
Supporting cells
Repair and supply nutrients to neurons

121. 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

122. Neural Tissue
Figure 4–19 Neural Tissue.

123. Tissue Injuries and Repair
Tissues respond to injuries to maintain homeostasis
Cells restore homeostasis with two processes
Inflammation
Regeneration

124. 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

125. Tissue Injuries and Repair
Inflammatory Response
Can be triggered by
Trauma (physical injury)
Infection (the presence of harmful pathogens)

126. Tissue Injuries and Repair
The Process of Inflammation
Damaged cells release chemical signals into the surrounding interstitial fluid
Prostaglandins
Proteins
Potassium ions
As cells break down
Lysosomes release enzymes
That destroy the injured cell
And attack surrounding tissues
Tissue destruction is called necrosis

127. Tissue Injuries and Repair
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

128. Tissue Injuries and Repair
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
Plasma diffuses into the area
Causing swelling and pain
Phagocytic white blood cells
Clean up the area

129. Tissue Injuries and Repair
Figure 4–20 An Introduction to Inflammation.

130. Tissue Injuries and Repair
Regeneration
When the injury or infection is cleaned up
Healing (regeneration) begins

131. 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)

132. 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

133. 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

134. Aging and Tissue Aging and Cancer Incidence
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