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. INTERCELLULAR JUNCTIONS
Neighboring cells within a multicellular organism often adhere, interact, and communicate through intracellular junctions
Tight junctions
Desmosomes
Gap junctions

6. INTERCELLULAR JUNCTIONS

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

8. 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

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

10. 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

11. GLANDULAR EPITHELIA
A gland consists of one or more cells that produce and secrete a product (secretion)
Secretion: verb and noun
Endocrine vs. exocrine
Unicellular vs. multicellular

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 Multicellular Glands: Structural Classification Simple
Compound
Tubular
Alveolar (acinar)
Tubuloalveolar

15. 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

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

17. 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

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

19. TYPES OF CONNECTIVE TISSUE
Connective Tissue Proper
Two subclasses
Loose connective tissue
Areolar
Adipose
Reticular
Dense connective tissue
Dense regular
Dense irregular
Elastic

20. TYPES OF CONNECTIVE TISSUE
Cartilage
Three varieties
Hyaline cartilage
Elastic cartilage
Fibrocartilage

21. TYPES OF CONNECTIVE TISSUE
Bone (Osseous Tissue)
Matrix similar to cartilage
More abundant collagen fibers
Inorganic calcium salts
Rocklike hardness
Ability to support & protect

22. TYPES OF CONNECTIVE TISSUE
Bone (Osseous Tissue)
Osteoblasts produce organic portion of matrix
Bone salts then deposited on & between fibers
Osteoblasts  osteocytes
Osteocytes reside in lacunae within the matrix
Vascular

23. TYPES OF CONNECTIVE TISSUE
Blood
Very atypical connective tissue
Does NOT connect things
Provides NO mechanical support
Why is it considered connective tissue?
Derived from mesenchyme

24. TYPES OF CONNECTIVE TISSUE
Blood
Various types of cells
Blood plasma is fluid matrix
Plasma proteins are “fibers”
Various functions
Transportation
Protection

25. MEMBRANES Continuous multiple sheets comprised of
Epithelium
Underlying layer of connective tissue
Three types of covering and lining membranes
Cutaneous
Mucous
Serous
These membranes are multicellular structures, and are quite different from the plasma membrane of a cell

26. CUTANEOUS MEMBRANES a.k.a., “Skin” Organ system Consists of
Keratinized stratified squamous epithelium
“Epidermis”
Thick layer of dense irregular connective tissue
“Dermis”
Dry membrane

27. MUCOUS MEMBRANES a.k.a., “Mucosae” Line body cavities open to exterior
e.g., digestive, respiratory, & urogenital tracts
“Wet” membranes
Bathed in secretions or urine
Often adapted for absorption and secretion
Many secrete mucus
Not all (urinary)

28. SEROUS MEMBRANES a.k.a., “Serosae”
Moist membranes found in closed ventral body cavities
Consist of
Simple squamous epithelium (mesothelium)
Thin layer of loose connective (areolar) tissue
Name based on location
Pleura of lungs
Pericardium of heart
Peritoneum of abdominopelvic cavity

29. SEROUS MEMBRANES Produce serous fluid
Blood filtrate + hyaluronic acid secreted by mesothelium
Lubricates facing surfaces of parietal and visceral layers

30. 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

31. 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

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

33. 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

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

35. 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

36. 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

37. TISSUE REPAIR Injured cells release growth factors
Stimulate cells to divide and migrate
Two major tissue repair means:
Regeneration
Replacement of destroyed tissue with same type of tissue
Fibrosis
Replacement with fibrous connective tissue (scar tissue)
Type of repair dependent upon
Type of tissue damaged
Severity of injury

38. TISSUE REPAIR Inflammation
Injured cells, macrophages, and mast cells release inflammatory chemicals
Dilation and increased permeability of capillaries
Plasma and leukocytes enter injured area
Plasma proteins form clot
Halts blood loss
Isolates injured area
Prevents spread of microbes
Forms scab

39. TISSUE REPAIR Organization Blood clot replaced by granulation tissue
Capillaries
Proliferating fibroblasts
Produce growth factors, collagen fibers
Pull margins of wound together
Macrophages
Digest clot
Granulation tissue ultimately becomes scar tissue

40. TISSUE REPAIR Permanent Repair Surface epithelium begins to regenerate
Grows under scab
Scab ultimately detaches
Epithelium fully regenerated
Fibrous material beneath epithelium matures and contracts
Scar tissue beneath epithelium
Scar may be visible or not

41. TISSUE REPAIR
The regenerative capacity of different tissues varies widely
Some tissues regenerate extremely well
e.g., Epithelial, bone, areolar connective tissue, blood-forming tissue
Some tissues have a moderate regenerative capacity
e.g., Smooth muscle, dense regular connective tissue
Some tissues have a weak regenerative capacity
e.g., Skeletal muscle, cartilage
Some tissues have a virtually no functional regenerative capacity
e.g., Cardiac muscle, nervous tissue

42. TISSUE REPAIR
In non-regenerative tissue and severe wounds, damaged tissue is replaced by fibrosis
Resulting scar tissue is strong, but lacks flexibility, elasticity, and function of normal tissue