1. Tissues
Cells work together in functionally related groups called tissues
Tissue – a group of closely associated cells that perform related functions and are similar in structure

2. Four Basic Tissue Types and Basic Functions
Epithelial tissue – covering
Connective tissue – support
Muscle tissue – movement
Nervous tissue – control

3. Covers a body surface or lines a body cavity Forms most glands
Epithelial Tissue
Covers a body surface or lines a body cavity
Forms most glands
Functions of epithelium
Protection
Absorption, secretion, and ion transport
Filtration
Forms slippery surfaces

4. Special Characteristics of Epithelia
Cellularity
Specialized contacts
Polarity
Support by connective tissue
Avascular but innervated
Regeneration

5. Special Characteristics of Epithelia
Figure 4.1

6. Classifications of Epithelia
Figure 4.2

7. Classifications of Epithelia
First name of tissue indicates number of cell layers
Simple – one layer of cells
Stratified – more than one layer of cells
Last name of tissue describes shape of cells
Squamous – cells wider than tall (plate-like)
Cuboidal – cells are as wide as tall, like cubes
Columnar – cells are taller than they are wide, like columns

8. Simple Squamous Epithelium
Description – single layer of flat cells with disc-shaped nuclei
Special types
Endothelium (inner covering) – slick lining of hollow organs
Mesothelium (middle covering)
Lines peritoneal, pleural, and pericardial cavities
Covers visceral organs of those cavities

9. Simple Squamous Epithelium
Function
Passage of materials by passive diffusion and filtration
Secretes lubricating substances in serosae
Location
Renal corpuscles
Alveoli of lungs
Lining of heart, blood and lymphatic vessels
Lining of ventral body cavity (serosae)

10. Simple Squamous Epithelium
Figure 4.3a

11. Simple Cuboidal Epithelium
Description – single layer of cube-like cells with large, spherical central nuclei
Function – secretion and absorption
Location – kidney tubules, secretory portions of small glands, ovary surface

12. Simple Cuboidal Epithelium
Figure 4.3b

13. Simple Columnar Epithelium
Description – single layer of column-shaped (rectangular) cells with oval nuclei
Some bear cilia at their apical surface
May contain goblet cells
Function
Absorption; secretion of mucus, enzymes, and other substances
Ciliated type propels mucus or reproductive cells by ciliary action

14. Simple Columnar Epithelium
Location
Non-ciliated form
Lines digestive tract, gallbladder, ducts of some glands
Ciliated form
Lines small bronchi, uterine tubes, and uterus

15. Simple Columnar Epithelium
Figure 4.3c

16. Pseudostratified Columnar Epithelium
Description
All cells originate at basement membrane
Only tall cells reach the apical surface
May contain goblet cells and bear cilia
Nuclei lie at varying heights within cells
Gives false impression of stratification

17. Pseudostratified Columnar Epithelium
Function – secretion of mucus; propulsion of mucus by cilia
Locations
Non-ciliated type
Ducts of male reproductive tubes
Ducts of large glands
Ciliated variety
Lines trachea and most of upper respiratory tract

18. Pseudostratified Ciliated Columnar Epithelium
Figure 4.3d

19. Stratified Epithelia
Contain two or more layers of cells
Regenerate from below
Major role is protection
Are named according to the shape of cells at apical layer

20. Stratified Squamous Epithelium
Description
Many layers of cells – squamous in shape
Deeper layers of cells appear cuboidal or columnar
Thickest epithelial tissue – adapted for protection

21. Stratified Squamous Epithelium
Specific types
Keratinized – contain the protective protein keratin
Surface cells are dead and full of keratin
Non-keratinized – forms moist lining of body openings

22. Stratified Squamous Epithelium
Function – Protects underlying tissues in areas subject to abrasion
Location
Keratinized – forms epidermis
Non-keratinized – forms lining of esophagus, mouth, and vagina

23. Stratified Squamous Epithelium
Figure 4.3e

24. Stratified Cuboidal Epithelium
Description – generally two layers of cube-shaped cells
Function – protection
Location
Forms largest ducts of sweat glands
Forms ducts of mammary glands and salivary glands

25. Stratified Cuboidal Epithelium
Figure 4.3f

26. Stratified Columnar Epithelium
Description – several layers; basal cells usually cuboidal; superficial cells elongated
Function – protection and secretion
Location
Rare tissue type
Found in male urethra and large ducts of some glands

27. Stratified Columnar Epithelium
Figure 4.3g

28. Transitional Epithelium
Description
Basal cells usually cuboidal or columnar
Superficial cells dome-shaped or squamous
Function – stretches and permits distension of urinary bladder
Location
Lines ureters, urinary bladder and part of urethra

29. Transitional Epithelium
Figure 4.3h

30. Ducts carry products of exocrine glands to epithelial surface
Include the following diverse glands
Mucus-secreting glands
Sweat and oil glands
Salivary glands
Liver and pancreas

31. Unicellular Exocrine Glands (The Goblet Cell)
Goblet cells produce mucin
Mucin + water  mucus
Protects and lubricates many internal body surfaces (small intestine)

32. Goblet Cells
Figure 4.5

33. Multicellular Exocrine Glands
Have two basic parts
Epithelium-walled duct
Secretory unit

34. Multicellular Exocrine Glands
Classified by structure of duct
Simple
Compound
Categorized by secretory unit
Tubular
Alveolar
Tubuloalveolar

35. Types of Multicellular Exocrine Glands
Figure 4.6

36. Endocrine Glands
Ductless glands
Secrete substances directly into bloodstream
Produce molecules called hormones

37. Lateral Surface Features – Cell Junctions
Factors holding epithelial cells together
Adhesion proteins link plasma membranes of adjacent cells
Contours of adjacent cell membranes
Special cell junctions

38. Tight Junction
Figure 4.7a

39. Lateral Surface Features – Cell Junctions
Tight junctions (zona occludens) – close off intercellular space
Found at apical region of most epithelial types
Some proteins in plasma membrane of adjacent cells are fused
Prevent molecules from passing between cells of epithelial tissue

40. Desmosome
Figure 4.7b

41. Lateral Surface Features – Cell Junctions
Desmosomes – two disc-like plaques connected across intercellular space
Plaques of adjoining cells are joined by proteins called cadherins
Proteins interdigitate into extracellular space
Intermediate filaments insert into plaques from cytoplasmic side

42. Gap Junction
Figure 4.7c

43. Lateral Surface Features – Cell Junctions
Gap junctions – passageway between two adjacent cells
Let small molecules move directly between neighboring cells
Cells are connected by hollow cylinders of protein

44. Basal Feature: The Basal Lamina
 Non-cellular supporting sheet between the epithelium and the connective tissue deep to it
 Consists of proteins secreted by the epithelial cells
 Functions:
 Acts as a selective filter, determining which molecules from capillaries enter the epithelium
 Acts as scaffolding along which regenerating epithelial cells can migrate
 Basal lamina and reticular layers of the underlying connective tissue deep to it form the basement membrane

45. Most diverse and abundant tissue Main classes
Connective Tissue
Most diverse and abundant tissue
Main classes
Connective tissue proper
Cartilage
Bone tissue
Blood
Cells separated by large amount of extracellular matrix
Common embryonic origin – mesenchyme

46. Classes of Connective Tissue
Figure 4.9

47. Major Functions of Connective Tissue
Support and binding of other tissues
Holding body fluids
Defending body against infection
Storing nutrients as fat

48. Connective Tissue Proper
Two main subclasses
Loose connective tissue
Dense connective tissue

49. Areolar Connective Tissue – A Model Connective Tissue
Underlies epithelial tissue
Surrounds small nerves and blood vessels
Has structures and functions shared by other connective tissues
Borders all other tissues in the body
Fibers provide support
Three types of protein fibers in extracellular matrix
Collagen fibers
Reticular fibers
Elastic fibers
Fibroblasts produce these fibers

50. Areolar Connective Tissue
Description
Gel-like matrix with all three fiber types
Cells – fibroblasts, macrophages, mast cells, white blood cells
Function
Wraps and cushions organs
Holds and conveys tissue fluid
Important role in inflammation

51. Areolar Connective Tissue
Location
Widely distributed under epithelia
Packages organs
Surrounds capillaries

52. Areolar Connective Tissue
Figure 4.12b

53. Adipose Tissue Description Closely packed adipocytes
Have nucleus pushed to one side by fat droplet

54. Adipose Tissue Function Location Provides reserve food fuel
Insulates against heat loss
Supports and protects organs
Location
Under skin
Around kidneys
Behind eyeballs, within abdomen and in breasts

55. Adipose Tissue
Figure 4.12c

56. Reticular Connective Tissue
Description – network of reticular fibers in loose ground substance
Function – form a soft, internal skeleton (stroma) – supports other cell types
Location – lymphoid organs
Lymph nodes, bone marrow, and spleen

57. Reticular Connective Tissue
Figure 4.12d

58. Dense Connective Tissue
Dense irregular connective tissue
Dense regular connective tissue

59. Dense Irregular Connective Tissue
Description
Primarily irregularly arranged collagen fibers
Some elastic fibers and fibroblasts

60. Dense Irregular Connective Tissue
Function
Withstands tension
Provides structural strength
Location
Dermis of skin
Submucosa of digestive tract
Fibrous capsules of joints and organs

61. Dense Irregular Connective Tissue
Figure 4.12e

62. Dense Regular Connective Tissue
Description
Primarily parallel collagen fibers
Fibroblasts and some elastic fibers
Poorly vascularized

63. Dense Regular Connective Tissue
Function
Attaches muscle to bone
Attaches bone to bone
Withstands great stress in one direction
Location
Tendons and ligaments
Aponeuroses
Fascia around muscles

64. Dense Regular Connective Tissue
Figure 4.12f

65. Other Connective Tissues
Cartilage
Bone
Blood

66. Cartilage
Firm, flexible tissue
Contains no blood vessels or nerves
Matrix contains up to 80% water
Cell type – chondrocyte

67. Types of Cartilage
Hyaline cartilage
Elastic cartilage
Fibrocartilage

68. Hyaline Cartilage Description
Imperceptible collagen fibers (hyaline = glassy)
Chodroblasts produce matrix
Chondrocytes lie in lacunae

69. Hyaline Cartilage Function Supports and reinforces Resilient cushion
Resists repetitive stress

70. Hyaline Cartilage Location Fetal skeleton Ends of long bones
Costal cartilage of ribs
Cartilages of nose, trachea, and larynx

71. Hyaline Cartilage
Figure 4.12g

72. Elastic Cartilage Description Similar to hyaline cartilage
More elastic fibers in matrix

73. Elastic Cartilage Function Location Maintains shape of structure
Allows great flexibility
Location
Supports external ear
Epiglottis

74. Elastic Cartilage
Figure 4.12h

75. Fibrocartilage Description Function
Matrix similar, but less firm than hyaline cartilage
Thick collagen fibers predominate
Function
Tensile strength and ability to absorb compressive shock

76. Fibrocartilage Location Intervertebral discs Pubic symphysis
Discs of knee joint

77. Fibrocartilage
Figure 4.12i

78. Bone Tissue Description
Calcified matrix containing many collagen fibers
Osteoblasts – secrete collagen fibers and matrix
Osteocytes – mature bone cells in lacunae
Very well vascularized

79. Bone Tissue Function Location Supports and protects organs
Provides levers and attachment site for muscles
Stores calcium and other minerals
Stores fat
Marrow is site for blood cell formation
Location
Bones

80. Bone Tissue
Figure 4.12j

81. Blood Tissue
An atypical connective tissue
Develops from mesenchyme
Consists of cells surrounded by nonliving matrix

82. Blood Tissue
Description – red and white blood cells in a fluid matrix
Function – transport of respiratory gases, nutrients, and wastes
Location – within blood vessels

83. Blood Tissue
Figure 4.12k

84. Covering and Lining Membranes
Combine epithelial tissues and connective tissues
Cover broad areas within body
Consist of epithelial sheet plus underlying connective tissue

85. Three Types of Membranes
Cutaneous membrane – skin
Mucous membrane
Lines hollow organs that open to surface of body
An epithelial sheet underlain with layer of lamina propria

86. Three Types of Membranes
Serous membrane – slippery membranes
Simple squamous epithelium lying on areolar connective tissue
Line closed cavities
Pleural, peritoneal, and pericardial cavities

87. Covering and Lining Membranes
Figure 4.13a, b

88. Covering and Lining Membranes
Figure 4.13c

89. Muscle Tissue
Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue

90. Skeletal Muscle Tissue
Description
Long, cylindrical cells
Multinucleate
Obvious striations

91. Skeletal Muscle Tissue
Function
Voluntary movement
Manipulation of environment
Facial expression
Location
Skeletal muscles attached to bones (occasionally to skin)

92. Skeletal Muscle Tissue
Figure 4.14a

93. Cardiac Muscle Tissue Description Branching cells, striated
Generally uninucleate
Cells interdigitate at intercalated discs

94. Cardiac Muscle Tissue Function Location
Contracts to propel blood into circulatory system
Location
Occurs in walls of heart

95. Cardiac Muscle Tissue
Figure 4.14b

96. Smooth Muscle Tissue Description
Spindle-shaped cells with central nuclei
Arranged closely to form sheets
No striations

97. Smooth Muscle Tissue Function Location
Propels substances along internal passageways
Involuntary control
Location
Mostly walls of hollow organs

98. Smooth Muscle Tissue
Figure 4.14c

99. Nervous Tissue Description
Main components are brain, spinal cord, and nerves
Contains two types of cells
Neurons – excitatory cells
Supporting cells (neuroglial cells)

100. Nervous Tissue Function Location
Transmit electrical signals from sensory receptors to effectors
Location
Brain, spinal cord, and nerves

101. Nervous Tissue
Figure 4.15

102. Tissue Response to Injury
Inflammatory response – non-specific, local response
Limits damage to injury site
Immune response – takes longer to develop and very specific
Destroys particular microorganisms at site of infection

103. Acute inflammation – heat, redness, swelling, and pain
Chemicals signal nearby blood vessels to dilate
Histamine increases permeability of capillaries

104. Edema – accumulation of fluid
Inflammation
Edema – accumulation of fluid
Helps dilute toxins secreted by bacteria
Brings oxygen and nutrients from blood
Brings antibodies from blood to fight infection

105. Repair
Regeneration – replacement of destroyed tissue with same type of tissue
Fibrosis – proliferation of scar tissue
Organization – clot is replaced by granulation tissue

106. Tissue Repair of a Skin Wound
Figure 4.16a

107. Tissue Repair of a Skin Wound
Figure 4.16b

108. Tissue Repair of a Skin Wound
Figure 4.16c

109. The Tissues Throughout Life
At the end of second month of development:
Primary tissue types have appeared
Major organs are in place
Adulthood
Only a few tissues regenerate
Many tissues still retain populations of stem cells

110. The Tissues Throughout Life
With increasing age:
Epithelia thin
Collagen decreases
Bones, muscles, and nervous tissue begin to atrophy
Poor nutrition and poor circulation – poor health of tissues