2. TISSUES
Tissues are communities of cells working together to perform a function for the organism.
Remember at all times that we are still talking about CELLS!
Even though commonly we think of organs as heart, lungs, kidney etc. that other tissues are also called organs such as muscles, bones etc.

3. Four Basic Tissue Types and Basic Functions (VERY GENERAL CATEGORIES)
Epithelial tissue – covering - ectoderm
Connective tissue – support – mesoderm/endoderm
Muscle tissue – movement - mesoderm
Nervous tissue – control – ectoderm
These are embryological terms:
Ectoderm – outer layer – integument, nervous system
Mesoderm – muscles, bones, tendons, ligaments
Endoderm – inner layer – organs, digestive system

4. Embronic derivatives

5. Epithelial Tissue Covers the body surface and lines body cavities
Forms parts of most glands (organs are mainly epithelial and connective tissues with nerves and blood vessels serving the cells)
Avascular
Functions of epithelium
Protection – part of immune system
Absorption (intestine), secretion (glands), and ion transport (nephron tubules)
Filtration (capillaries)
Forms slippery surfaces (mucus membranes)
Glandular Epithelium (sweat, oil, wax, hormones, mucus)
Greatest capacity for regeneration (therefore is the origin of most cancers)

6. Simple Squamous
Endothelium – lines blood vessels, heart chambers and alveoli
This is very specialized to facilitate easy passage of materials in capillaries, alveoli and lining of blood vessels and chambers of the heart
Mesothelium – lines body cavities, serous membranes

7. Side view and single cell superior  inferior view

8. Stratified Epithelia Properties Contain two or more layers of cells
Regenerate from below (basal layer)
Major role is protection
Named according to shape of cells at apical layer

9. 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 from abrasion

10. Stratified Squamous Epithelium
Two types
Keratinized and nonkeratinized
Keratinized
Location – epidermis
Contains the protective protein keratin
Waterproof
Surface cells are dead and full of keratin
Nonkeratinized
Forms moist lining of body openings

11. Stratified Squamous
Designed for protection Found in areas where there may be mechanical and chemical stress such as the skin and digestive systems as well as the penis and vagina
The germinal layer looks cuboidal but the apical cells which are dead, are squamous in shape

12. Stratified Squamous Epithelium
Figure 4.3e

13. 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 are wider than tall (plate-like)
Cuboidal – cells are as wide as tall, like cubes
Columnar – cells are taller than they are wide, like columns

14. Simple Cuboidal & Simple Columnar
Usually for secretion and absorption
Cuboidal cells are found in glands, ducts and tubules
Stratified cuboial are found in glands such as the salivary, mammary and large sweat glands
Columnar – found in the digestive system, may have villi and microvilli
Stratified columnar – very rare. Found in male urethra
Pseudostratified columnar – found in respiratory system.
Have cilia to move foreign particles away from the lungs

15. Simple Cuboidal Epithelium
Figure 4.3b

16. Stratified Cuboidal Epithelium
Figure 4.3f

17. Simple Columnar Epithelium
Figure 4.3c

18. Pseudostratified Ciliated Columnar Epithelium
Figure 4.3d

19. Stratified Columnar Epithelium
Figure 4.3g

20. Transitional Epithelium
This is a specialized epithelium which allows expansion like a balloon
All cells have an attachment to the basement membrane
The apical surface looks like balloons
Lines bladder, ureters
With your partner, teach each other about the four epithelial types: Include where you would find them!
simple and stratified squamous
Cuboidal
Columnar – simple, pseudostratified
Transitional -

21. Transitional Epithelium
Figure 4.3h

22. EPITHELIUM AS GLANDS EXOCRINE GLANDS –with ducts
ENDOCRINE GLANDS – without ducts
Epithelial cells are very active cells and are highly mitotic, replacing themselves often. They also produce many products such as saliva, enzymes, mucus and hormones.

23. Exocrine Glands Goblet cells produce mucin Mucin + water  mucus
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
Goblet cells produce mucin
Mucin + water  mucus
Protects and lubricates many internal body surfaces
Goblet cells are a unicellular exocrine gland and are epithelial

24. Goblet Cells – a type of epithelial cell (Unicellular gland)
Figure 4.5

25. Endocrine Glands Endocrine glands are ductless glands
Secrete substances directly into extracellular space to be picked up by the bloodstream by diffusion
Produce molecules called hormones

26. Special Characteristics of Epithelia
1) Cellularity - cells separated by minimal extra cellular material 2) Specialized contacts - cells joined by specialized cell junctions 3) Polarity - cell regions of the apical surface differ from the basal surface

27. Special Characteristics of Epithelia
4) Support by connective tissue 5) Avascular but innervated - Epithelia receive nutrients from underlying connective tissue 6) Regeneration - Lost cells are quickly replaced by cell division

28. Basal Feature: The Basal Lamina
Noncellular supporting sheet between the ET and the CT deep to it
Consists of proteins secreted by ET cells

29. Basal Lamina
Damage to the basal lamina due to untreated diabetes may lead to kidney failure and blindness.

30. Special Contacts (Lateral Surface Features) – Cell Junctions
Think about the function of epithelial tissues and what characteristics it would have to have to perform that function.
Since exposure to digested food would be very dangerous if exposed to the contents of the abdominal cavity, the intestinal tissue needs to be a barrier.
Therefore, cells need to be tightly held together
Factors holding epithelial cells together
Adhesion proteins link plasma membranes of adjacent cells
Contours of adjacent cell membranes
(Like puzzle pieces)
Special cell junctions

31. A) Tight Junction
Tight junctions (zona occludens) – close off intercellular space
Figure 4.7a

32. B) Desmosome
Desmosomes – two disclike plaques connected across intercellular space
Figure 4.7b

33. C) Gap Junction Gap junctions – passageway between two adjacent cells
Figure 4.7c

34. D) Adherens Junctions Has linker proteins; Important for the skin
Zonula adherens

35. Basal Feature: The Basal Lamina
Functions
Acts as a selective filter, determining which molecules from capillaries enter the epithelium
Acts as scaffolding along which regenerating ET cells can migrate
Basal lamina and reticular layers of the underlying CT deep to it form the basement membrane

36. Epithelial Apical Surface Features
1) Microvilli – fingerlike extensions of plasma membrane
Abundant in ET of small intestine and kidney
Maximize surface area across which small molecules enter or leave
Act as stiff knobs that resist abrasion
2) Cilia – whiplike, highly motile extensions of apical surface membranes
Contains a core of nine pairs of microtubules encircling one middle pair
Each pair of microtubules – arranged in a doublet
Movement of cilia – in coordinated waves

37. Cilia – found in upper respiratory passageways
For information only
Figure 4.8

38. Classes of Connective Tissue
Most diverse and abundant tissue
Main classes
Connective tissue proper
Cartilage
Bone tissue
Blood and fat!
Cells separated by large amount of extracellular matrix
Common embryonic origin – mesenchyme
Extracellular matrix is composed of ground substance

39. Classes of Connective Tissue
Figure 4.9

40. Connective Tissue Proper
This cell type is the most diverse and abundant type of tissue
Has two subclasses
Loose connective tissue
Areolar, adipose, and reticular
Dense connective tissue
Dense irregular, dense regular, and elastic

41. Areolar Connective Tissue – A Model Connective Tissue
Underlies epithelial tissue
Surrounds small nerves and blood vessels
Has structures and functions shared by other CT
Borders all other tissues in the body
Is a “model” connective tissue – why?
It has all 3 fiber types: Reticular, elastic and collagen fibers

42. Major Functions of Connective Tissue
Structures within areolar CT and function
Support and binding of other tissues
Holding body fluids (interstitial fluid  lymph)
Defending body against infection
Storing nutrients as fat

43. Areolar Connective Tissue
Fibers provide support
Three types of protein fibers in extracellular matrix
Collagen fibers
Reticular fibers
Elastic fibers
Fibroblasts produce these fibers

44. Areolar Connective Tissue
Figure 4.12b

45. Areolar Connective Tissue
Tissue fluid (interstitial fluid)
Watery fluid occupying extracellular matrix
Tissue fluid derives from blood
Ground substance
Viscous, spongy part of extracellular matrix
Consists of sugar and protein molecules
Made and secreted by fibroblasts
The least specialized connective tissue in the adult body is loose areolar, which contains all the cells and fibers found in connective tissue proper.

46. Areolar Connective Tissue
Main battlefield in fight against infection
Defenders gather at infection sites
Macrophages
Plasma cells
Mast cells
White blood cells
Neutrophils, lymphocytes, and eosinophils

47. Adipose Tissue
Figure 4.12c

48. Reticular Connective Tissue
Figure 4.12d

49. Reticular Continued
Reticular tissue provides a supporting framework, forming the stroma (body, or substance) of the liver, spleen, bone marrow, and lymph nodes

50. Dense Connective Tissue
Dense irregular connective tissue
Dense regular connective tissue
Elastic connective tissue

51. Dense Irregular Connective Tissue
Figure 4.12e

52. Dense Regular Connective Tissue
Figure 4.12f

53. Elastic Connective Tissue
Figure 4.12g

54. Elastic Continued
often underlie transitional epithelia; and are also found in the walls of blood vessels and surrounding the respiratory passageways

55. Other Connective Tissues
Cartilage
Bone
Blood

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

57. Types of Cartilage
Hyaline cartilage
Elastic cartilage
Fibrocartilage

58. Hyaline Cartilage Fibers are not normally seen
collagen fibers (hyaline = glassy); Chodroblasts produce matrix; Chondrocytes lie in lacunae
Figure 4.12h

59. Elastic Cartilage
Figure 4.12i

60. Fibrocartilage
Figure 4.12j

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

62. Bone Tissue
Figure 4.12k

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

64. Blood Tissue
Figure 4.12l

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

66. Skeletal Muscle Tissue
Figure 4.14a

67. Cardiac Muscle Tissue
Figure 4.14b

68. Smooth Muscle Tissue
Figure 4.14c

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

70. Nervous Tissue
Figure 4.15

71. Neuroglial Cells regulate the composition of interstitial fluid
provide a supporting framework for neural tissue
provide nutrients to neurons
provide a supporting framework for neural tissue and provide nutrients to neurons

72. 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

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

74. 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

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

76. Covering and Lining Membranes
Figure 4.13a, b

77. Covering and Lining Membranes
Figure 4.13c

78. Name all cell junction types and what are their distinguishing features?
How many layers is pseudostratified epithelium?