1. Chapter 4
Tissues
Muse 2430 lecture #2
1/14/13

2. The Cell Cycle

3. Stem and Progenitor Cells

4. 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

5. 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

6. A little embryology

7. 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

8. 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

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

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

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

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

13. 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

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

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

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

17. 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

18. 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

19. 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

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
Figure 4–2 Intercellular Connections

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

25. 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

26. Classification of Epithelia

27. Classification of Epithelia

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

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

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

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

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

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

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

35. 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)

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

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

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

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

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

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. 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

51. 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

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

53. 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

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

55. 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

56. 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.

57. 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

58. 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

59. 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

60. 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

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

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

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

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

65. 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

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

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

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

69. 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)

70. 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

71. 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

72. 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

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

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

75. 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

76. 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

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

78. 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)

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

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

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

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

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

84. 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

85. 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

86. 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

87. Membranes
Figure 4–16 Membranes.

88. 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

89. Membranes
Figure 4–16 Membranes.

90. Neural Tissue
Figure 4–19 Neural Tissue.

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

92. 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

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