1. Chapter 4 The Tissue Level of Organization
BIO 210 Lab
Instructor Dr. Rebecca Clarke

2. Tissue Histology = study of tissues
Tissue = group of cells that perform specific, limited functions

3. Composition of Tissues
Basic components
Cells
Matrix
Surrounds cells
Consists of
Ground substance
Protein fibers or proteins

4. 4 Major Groups of Tissues
Epithelial tissue
Connective tissue
Muscle tissue
Neural tissue

5. Epithelial Tissue Covers exposed surfaces Lines internal passageways
Forms glands

6. Connective Tissue Fills internal spaces Supports other tissues
Transports materials
Stores energy

7. Muscle Tissue
Specialized for contraction  movement

8. Neural Tissue
Carries electrical signals (nerve impulses) from one part of the body to another

9. Epithelial Tissue Includes Epithelia = layers of cells that cover
External/exposed surfaces (skin)
Internal surfaces that line internal passageways and cavities
Glands = cellular structures that produce secretions; are attached to or derived from epithelia

10. Classes of Epithelia Based on cell shape and layers Simple epithelium
single layer of cells
thin, fragile
Stratified epithelium
several layers of cells
tougher
Table 4–1

11. Simple Squamous Epithelium
Most delicate epithelium
Types of squamous epithelium
Simple squamous epithelium
absorption and diffusion
Mesothelium
lines body cavities
Endothelium
lines heart and blood vessels
Figure 4–3a

12. Stratified Squamous Epithelium
Multiple layers of cells from cube-shaped  flat cells (from BM to apical surface)
Located in areas that need protection from mechanical or chemical injury/stresses
keratinized – apical layers have keratin proteins  tough, water resistant body surface (skin)
nonkeratinized -- lining peritoneal cavity, mouth (buccal/cheek mucosa)
Figure 4–3b

13. Simple Cuboidal Epithelium
Rows of cube-shaped cells
Figure 4–4a

14. Stratified Cuboidal Epithelium
Layers of cube-shaped cells; rare
Figure 4–4b

15. Transitional Epithelium
Rounded cells in irregular layers.
Tolerates repeated cycles of stretching.
Figure 4–4c

16. Simple Columnar Epithelium
Figure 4–5a

17. Stratified Columnar Epithelium
Figure 4–5c

18. Pseudostratified Columnar Epithelium
Single layer of cells of varying shapes appear layered (pseudo-) but all contact BM
Usually have cilia
Figure 4–5b

19. Glandular Epithelia Endocrine and exocrine glands
Range from scattered cells to complex organs (glands)
Figure 4–6

20. Endocrine Glands Ductless glands
Release secretions (hormones) into interstitial fluid or blood
Regulate/coordinate activities of many tissues, organs, organ systems

21. Exocrine Glands Release secretions
onto epithelial surfaces, e.g., simplest = one-cell goblet cell (in respiratory and digestive tracts)
through ducts, e.g., sweat, digestive, lacrimal, mammary glands

22. What are the structures and functions of different types of connective tissues?

23. Characteristics of Connective Tissues
Fills internal spaces
Many diverse functions
Many highly-specialized cells
Much more matrix than cells

24. Components of Connective Tissue
Cells – highly varied, specialized populations
Matrix
Consists of
Ground substance
Fills spaces between cells and surrounds connective tissue fibers
Clear, colorless, amorphous substance; changes according to tissue
Viscous (“syrupy”) due to proteoglycans and glycoproteins
Protein fibers/proteins
Can be fluid, gel or solid, e.g., gelatin dessert
Determines specialized function

25. Classification of Connective Tissues
Connective tissue proper
Connects and protects
Loose and dense connective tissues
Fluid connective tissues
Transport systems
Blood and lymph
Supporting connective tissues
Structural strength
Cartilage and bone

26. Connective Tissue Proper
Figure 4–8

27. 8 Cell Types of Connective Tissue Proper
Mesenchymal cells
Fibroblasts
Phagocytes
Macrophages
Microphages
Mast cells
Adipocytes
Melanocytes
Lymphocytes

28. Mesenchymal Cells
Mesenchyme = first connective tissue in developing embryo (see text Fig 4-9)
Are connective tissue stem cells; give rise to all other connective tissue cells
e.g., Respond to local injury/infection by dividing  daughter cells that differentiate into other connective tissue cells, e.g., fibroblasts, macrophages, etc.

29. Fibroblasts “Fiber builder” Most abundant cell type
Found in all connective tissue proper
Secrete
polysaccharide (+ protein  proteoglycans  viscous ground substance)
protein subunits  large fibers

30. Phagocytes Phagocytes (“cell eaters”) Macrophages (“big eaters”)
Microphages (“little eaters”)

31. Macrophages Large, amoeba-like cells of the immune system
Eat pathogens and damaged cells; “garbage disposal” cells
Release chemicals that activate immune system  mobilizes body defenses
2 classes
fixed macrophages stay in tissue; frontline defense
free macrophages migrate through tissues; reinforcements

32. Microphages (NOT in Fig 4-8)
Phagocytic white blood cells (WBCs), i.e., neutrophils and eosinophils
Attracted to site of infection/injury by chemicals released by macrophages

33. Mast Cells Small mobile cells
Stimulate inflammation after injury or infection
Cytoplasm filled with granules that contain/release histamine and heparin
Basophils are mast cells carried by blood

34. Adipocytes Adipose or fat cells Store fat
Contain single, large lipid droplet; nucleus, other organelles, cytoplasm squeezed to side  class ring appearance
Number of cells varies with tissue, body region, individual

35. Melanocytes Synthesize, store melanin (brown pigment)  dark color
Common in skin epithelium
Determine skin, eye, hair color

36. Lymphocytes Specialized immune cells in lymphatic system
e.g., plasma cells that produce antibodies; one of body’s defense mechanisms
WBCs that leave bloodstream and migrate throughout body
Numbers increase with tissue damage

37. Protein Fibers Provide structural strength to connective tissues
3 types
Collagen
Reticular
Elastic

38. Collagen Fibers Most common fibers Large, long, straight, unbranched
Strong, flexible (like rope); very little stretch
Predominate in ligaments (connect bone to bone) and tendons (connect muscle to bone)

39. Reticular Fibers Same protein subunits as collagen but
Thinner, shorter
Arranged differently  branched network of interwoven fibers (stroma)
Strong, flexible
Stabilizes functional cells of organs (parenchyma), e.g., hepatic cells of liver
Stabilizes position of blood vessels, nerves, etc.
Connects epithelium to body

40. Elastic Fibers Contain protein elastin Branched and wavy
Return to original length after stretching
e.g., elastic ligaments of vertebrae

41. Categories of Connective Tissue Proper
Loose connective tissue
more ground substance, less fibers
e.g., fat (adipose tissue)
Dense connective tissue
more fibers, less ground substance
e.g., tendons

42. Loose Connective Tissue
Few soft fibers  loose, open framework; “packing materials” of body
Fills spaces between organs
Cushions, stabilizes cells
Supports epithelia, blood vessels, nerves

43. Loose Connective Tissue (cont.)
3 types
Areolar tissue
Adipose tissue
Reticular tissue

44. Areolar Tissue Least specialized Open framework of cells/fibers
Can distort, return to original shape because of elastic fibers
Most of volume is viscous ground substance
Highly vascular, e.g., subcutaneous layer under skin, common injection site
Fig 4-8

45. Adipose Tissue
Primarily adipocytes (adipose cells)
Figure 4–10a

46. 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

47. Reticular Tissue
Primarily reticular fibers
Figure 4–10b

48. Reticular Tissue Complex, 3-dimensional network
Supportive fibers (stroma)
support functional cells (parenchyma)
Reticular organs
spleen, liver, lymph nodes, and bone marrow

49. Dense Connective Tissues
Tightly packed with high numbers of collagen or elastic fibers
Many fibroblasts
Very strong tissues
Types of dense connective tissues
dense regular connective tissue
dense irregular connective tissue
elastic tissue

50. Dense Regular Connective Tissue
Tightly packed, parallel collagen fibers
Make up tendons, ligaments, aponeuroses
Figure 4–11a

51. Dense Regular Connective Tissues
Tendons - attach skeletal muscles to bones
Ligaments - connect bone to bone and stabilize organs
Aponeuroses - attach in sheets on large, flat muscles

52. Dense Irregular Connective Tissue
Strength in many directions
Figure 4–11b

53. Dense Irregular Connective Tissues
Interwoven meshwork of collagen fibers
layered in skin
around cartilages (perichondrium)
around bones (periosteum)
form capsules around some organs (e.g., liver, kidneys, spleen)

54. Elastic Tissue Made of elastic fibers
e.g., elastic ligaments of spinal vertebrae
Figure 4–11c

55. Fluid Connective Tissues
Blood and lymph
Cells suspended in fluid matrix = watery ground substance with dissolved proteins

56. Blood Formed Elements RBCs (erythrocytes) WBCs (leukocytes) Platelets
Transport O2 and CO2 in blood
One-half blood volume
99.9% of formed elements
WBCs (leukocytes)
Important components of immune system that protect body from infection and disease
cell types
monocytes (are phagocytes, macrophages)
lymphocytes
microphages (phagocytes)
- neutrophils
- eosinophils
basophils
platelets
membrane-enclosed packets of cytoplasm; cell fragments, not cells (acellular)
contain enzymes and special proteins
function in clotting response
Figure 4–12

57. Lymph Cells – 99% lymphocytes, rest are macrophages or microphages
Matrix = fluid from CVS exits at capillaries  interstitial fluid  enters lymphatic vessels (= lymph) that return it to CVS (recirculatory system)
Along way, cells of immune system monitor composition of lymph and respond to signs of injury or infection
Essential to homeostasis – eliminates local differences in nutrients, wastes, toxins, maintains blood volume, alerts immune system

58. Fluid Tissue Transport Systems
Cardiovascular system (blood)
arteries
capillaries
veins
Lymphatic system (lymph)
lymphatic vessels

59. Supporting Connective Tissues
Support soft tissues and body weight
Cartilage
for shock absorption and protection
Bone
for weight support

60. Supporting Connective Tissues
Characteristics
Provide strong framework that supports body
Cells – less diverse than CT
Matrix
Dense ground substance
Cartilage – rubbery, gel-like
Bone - calcified, crystalline, solid matrix
Many fibers

61. Cartilage Components Cells Matrix Protein fibers
Chondrocytes = only cells present
Occupy lacunae (small chambers)
Matrix
Ground substance = firm gel with…
Chondroitin sulfates (polysaccharide derivatives); form complexes with proteins  proteoglycans
Protein fibers
Type and number + proteoglycans determine physical properties

62. Cartilage Structure Avascular = no blood vessels Perichondrium
chondrocytes produce antiangiogenesis factor
Perichondrium
surrounds cartilage and separates it from tissue

63. Types of Cartilage Hyaline cartilage Elastic cartilage Fibrocartilage
translucent matrix
no prominent fibers
Elastic cartilage
tightly packed elastic fibers
Fibrocartilage
very dense collagen fibers

64. Hyaline Cartilage
Figure 4–14a

65. Hyaline Cartilage Most common
Matrix - contains closely packed collagen fibers  tough, flexible support
Reduces friction between bones
Examples
Connects ribs and sternum
Nasal cartilages
Cartilages that support respiratory passageways, e.g., trachea
Articular cartilages – cover bone surfaces within synovial joints, e.g., elbow, knee; reduce friction

66. Elastic Cartilage
Figure 4–14b

67. Elastic Cartilage
Many elastic fibers  resilient, flexible structures; supports but bends easily
Examples
auricle/pinna of outer ear
epiglottis (in larynx)
auditory tube (airway to middle ear)
small cartilages in larynx

68. Fibrocartilage
Figure 4–14c

69. Fibrocartilage Very little ground substance
Matrix dominated by densely interwoven collagen fibers  extremely durable, tough
Resists compression
Acts as shock absorber
Prevents bone-to-bone contact
Examples:
Intervertebral discs = pads between vertebrae
Between pubic bones
Pads knee joints

70. Bone Also called osseous tissue Osteocyte = bone cell Periosteum
Arranged around central canal
Small channels through matrix (canaliculi) access blood supply
Periosteum
covers bone surface
Helps attach bone to surrounding tissues, tendons, ligaments

71. Bone organization of osseous tissue (Fig 4-15)
1) osteon = basic histological unit of compact bone; consists of osteocytes (cells) organized around a central canal and separated by concentric lamellae
2) osteocytes occupy lacunae (= small chambers) organized around blood vessels
3) osteocytes connect with other osteocytes and blood vessels via cytoplasmic extensions that run through canaliculi = “little canals”, slender passageways in matrix;  branching network for exchange of materials between osteocytes and blood
4) periosteum
a) sheaths bone surface
b) has fibrous (outer) and cellular (inner) layers
c) helps attach bone to surrounding tissues, tendons, liga
Figure 4–15

72. Bone Ground Substance Very small amount of ground substance
2/3 of matrix is calcium salts (minerals) = hydroxyapatite
Calcium phosphate
Calcium carbonate
1/3 of matrix dominated by collagen fibers
Minerals organized around collagen fibers
 Remarkable properties of bone
Strong (calcified salts) + somewhat flexible structure (collagen fibers)
Highly resistant to shattering (like steel-reinforced concrete
mineralized matrix like concrete
collagen fibers equiv to steel reinforcing rods

73. Comparing Cartilage and Bone
Table 4–2

74. What are the structures and functions of the three types of muscle tissue?

75. Muscle Tissue Specialized for contraction; produces all body movement
Distinct organelles and processes
Multinuclear
Has many fibers; orderly appearance
under voluntary or involuntary control
One of two kinds of cells/tissues in body that stop replicating past stage of growth and development; (other is neural tissues/neurons)

76. 3 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)

77. Classification of Muscle Cells
Striated (muscle cells with a banded appearance)
or nonstriated (not banded)
Single nucleus
or multinucleate
Controlled voluntarily (consciously)
or involuntarily (automatically)

78. Skeletal Muscle
Striated, voluntary, multinucleated
Figure 4–18a

79. Skeletal Muscle Cells
Very long (some > 1 ft) and thin; called muscle fibers
Multinucleate; 100s of nuclei/cell
Cytoskeleton contains actin and myosin filaments
Filaments organized into repeating groups  striated/banded appearance
Contract when stimulated by nerves; provide voluntary control over muscle activities
Adjacent muscle fibers connected by collagen and elastic fibers that blend into attached tendon or aponeurosis; when contract, pull on attached bone, producing movement
Can’t divide; new muscle fibers produced through divisions of satellite (stem) cells; can partially repair after injury

80. Cardiac Muscle Tissue Striated, involuntary, single nucleus
Figure 4–18b

81. Cardiac Muscle Cells Cardiac muscle cell = cardiocyte
Smaller than skeletal muscle cell
Usually one centrally positioned nucleus
Actin and myosin filaments arranged in same way as in skeletal muscle;  striations
Cells form branching networks; connected at specialized regions = intercalated discs (like dovetail joints)
Ion movement through gap junctions helps coordinate contractions throughout heart
Rely on pacemaker cells to establish regular rate of contraction; neural stimulation not required
Involuntary muscle contractions
Very limited ability to repair

82. Smooth Muscle Tissue Nonstriated, involuntary, single nucleus
Figure 4–18c

83. Smooth Muscle Cells Smooth muscle cell
small, spindle-shaped cell, tapered ends
single oval nucleus
actin and myosin filaments organized differently from those of skeletal and cardiac muscles, no striations  “smooth” appearance
Nervous system does not provide voluntary control over contractions; hence, smooth muscle = involuntary muscle
Cells can divide and regenerate after injury
Location:
Walls of blood vessels
Around hollow organs, e.g., urinary bladder
In layers around respiratory, circulatory, digestive, reproductive tracts

84. What is the basic structure and role of neural tissue?

85. Neural (Nervous) Tissue
Specialized for conducting electrical impulses
Rapidly senses internal or external environment
Processes information and controls responses

86. Neural Tissue 98% concentrated in central nervous system (CNS)
brain
spinal cord
Remaining 2% in peripheral nervous system (PNS)

87. 2 Types of Neural Cells Neurons Neuroglia nerve cells
perform electrical communication
Neuroglia
support cells
repair and supply nutrients to neurons

88. Neuron D. cell characteristics/structures
1. large cell body with large nucleus and prominent nucleolus
2. branching processes extend from cell body = dendrites and 1 axon
a. dendrites receive incoming formation, usually from other neurons
b. axon (aka nerve fiber because very long and slender) carries info away from neuron to other cells
Figure 4–19

89. Cell Parts of a Neuron Cell body Dendrites
contains the nucleus and nucleolus
Dendrites
short branches extending from the cell body
receive incoming signals

90. Cell Parts of a Neuron Axon (nerve fiber)
long, thin extension of the cell body
carries outgoing electrical signals to their destination

91. Characteristics of Neurons
Longest cells in body – some > 1 meter
Cannot divide under normal circumstances so very limited ability to repair selves
One of only two kinds of cells/tissues in body that stop replicating after stage of growth and development (other is muscle tissue)

92. Neuroglia
Figure 4–19