1. TISSUES

2. STRUCTURAL ORGANIZATION
Life is characterized by hierarchical orders of organization
Atoms
Molecules
Organelles
Cells
Tissues
Organs
Organ systems
Organism
(Population)
(Community)
(Ecosystem)

3. STRUCTURAL ORGANIZATION
The cell is the lowest level of organization that can live independently as an organism
Paramecium
Amoeba

4. STRUCTURAL ORGANIZATION
In multicellular organisms, specialized cells are grouped into tissues
A tissue is a group of cells similar in structure and performing a common function
Organs are comprised of combinations of various tissues
Organ systems include multiple organs working together

5. TISSUE TYPES Four major tissue types Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue

6. EPITHELIAL TISSUE
Sheets of cells covering body surfaces or lining body cavities
Form boundaries between different environments
e.g., Epidermis of skin separates inside and outside of body
e.g., Epithelium lining urinary bladder separates underlying cells from urine

7. EPITHELIAL TISSUE Many diverse functions Protection Absorption
Filtration
Excretion
Secretion
Sensory reception

8. EPITHELIUM CHARACTERISTICS
Cellularity
Little extracellular material
Specialized contacts
Tight junctions & desmosomes
Polarity
Basal and apical surfaces
Supported by connective tissue
Avascular
Nourished from below
Innervated
Regeneration
Rapid cell division at basal surface

9. CLASSIFICATION OF EPITHELIA
Cell layers
Simple epithelia
Single cell layer
Facilitates absorption and filtration
Stratified epithelia
Two or more cell layers
Common in high-abrasion areas
e.g., Skin surface, mouth

10. CLASSIFICATION OF EPITHELIA
Cell shape
All epithelia have six sides
Cells vary in height
Three common shapes
Squamous cells
Cuboidal cells
Columnar cells
Shape of nucleus conforms to shape of cell

11. CLASSIFICATION OF EPITHELIA
Cell layers & cell shape
Two names
First name indicates cell layers
Second name indicates cell shape
e.g., Simple squamous epithelium
e.g., Stratified cuboidal epithelium

12. ENDOCRINE GLANDS “Ductless glands” Produce hormones
(Ducts are eventually lost)
Produce hormones
Secreted directly into extracellular space via exocytosis
Many (but not all) are epithelial derivatives
More information in their own chapter

13. EXOCRINE GLANDS More numerous than endocrine glands
Secrete into body cavities or onto body surfaces
(i.e., Not into extracellular space)
Unicellular glands via exocytosis
Multicellular glands via ducts
Diverse
e.g., Mucous, sweat, oil, and salivary glands, etc.

14. EXOCRINE GLANDS Unicellular Gland: Goblet cell Shaped like a goblet
Present in columnar epithelia of intestinal and respiratory tracts
Produce mucin
Mucin + water  mucus
Protects and lubricates

15. EXOCRINE GLANDS Multicellular Glands: Structural Classification Simple
Compound
Tubular
Alveolar (acinar)
Tubuloalveolar

16. CONNECTIVE TISSUE Found everywhere in the body Four main classes
Most widely distributed primary tissue
Four main classes
Connective tissue proper
Cartilage
Bone tissue
Blood

17. CONNECTIVE TISSUE Major functions
Binding and support
Protection
Insulation
Transportation
Which of these functions are accomplished by bone and cartilage? Fat? Blood?

18. CONNECTIVE TISSUE Common Characteristics Common origin
All connective tissues arise from mesenchyme (an embryonic tissue)
Degrees of vascularity
Avascular
poorly vascular
highly vascular
Extracellular matrix
Largely composed of non-living extracellular matrix

19. CONNECTIVE TISSUE Three main structural elements Ground substance
Fibers
Cells
Ground substance + fibers = matrix

20. FIBERS Three types of fibers provide support Collagen fibers
“White” fibers
Strongest and most abundant
Tensile strength > steel
Elastic fibers
“Yellow fibers”
Long, thin, branching fibers
Contain the protein elastin
Can stretch and recoil
Reticular fibers
Fine collagenous fibers
Networks surround and support soft tissue of organs

21. CELLS Connective tissue is a home for many other cell types Fat cells
Leukocytes
Macrophages
Mast cells
These last three types of cells will be dealt with in great detail in the blood chapter
Macrophages and mast cells will be dealt with in some detail now

22. NERVOUS TISSUE Main component of the nervous system
Brain, spinal cord, and nerves
Regulates and controls body functions
Two main cell types
Neurons
Generate and conduct nerve impulses
Supporting cells
Non-conducting cells that support, insulate, and protect neurons

23. MUSCLE TISSUE Highly cellular Well vascularized
Responsible for most types of body movement
Possess myofilaments
Actin and myosin
Three types
Skeletal muscle
Cardiac muscle
Smooth muscle

24. SKELETAL MUSCLE Skeletal muscle cells a.k.a., “Muscle fibers”
Long, cylindrical cells
Multinucleate
Striated
Voluntary

25. SKELETAL MUSCLE Forms organs called skeletal muscles
Packaged by sheets of connective tissue
Attached to bones of skeleton
Contract to pull on bones or skin
Movement results

26. CARDIAC MUSCLE Found only in the wall of the heart
Contractions propel blood through blood vessels
Cardiac muscle cells
“Myocytes”
Striated
Uninucleate
Branching
Involuntary

27. SMOOTH MUSCLE Found mainly in walls of hollow organs
e.g., Intestines, esophagus, blood vessels, etc.
Contractions squeeze substances through these organs
No visible striations
Smooth muscle cells
Spindle shaped
Uninucleate
Involuntary

28. BODY DEFENSES
Mechanical barriers are the body’s first line of defense against injury and infection
Skin and mucous membranes
Respiratory cilia
Acids secreted into stomach and from skin
Tissue injury breaches this first line of defense
Stimulates inflammatory and immune responses
Second and third lines of defense, respectively
Tissue is ultimately repaired