1. Tissues Introduction Epithelial Tissue Classification Glands

2. Cell Specialization Multicellularity requires a division of labor
Cells look and function differently (specialize) in different parts of the body (ex. bone cell vs. nerve cell)
Cells specialize into types of tissues, then form organs.

3. Histology
Study of tissues (groups of cells that are similar in structure and function)
4 Tissue Types

4. 1. Connective Tissue Support Connect layers of tissue to each other
Bone, ligaments, fat
(we will study these in great detail in class later…)

5. 2. Nervous Tissue Control Brain, nerves, spinal cord
Highly specialized cells that generate and conduct nerve impulses

6. 3. Muscular Tissue Movement Highly vascular
Contraction involves myosin protein filament and cytoskeleton microfilament, actin
2 categories:
Striated muscle tissue (voluntary or partly voluntary control)
Smooth muscle tissue (involuntary)

7. 3. Muscular Tissue Striated Muscle Ex. Skeletal Ex. Cardiac
Attached to skeletal bones
Long, cylindrical multi-nucleated cells
Visible striations
Voluntary control
Ex. Cardiac
Also striated, but uni-nucleated
Branching cells fit tightly with special junctions called intercalated discs

8. 3. Muscular Tissue Smooth muscle No striations Spindle shaped
One central nucleus
Involuntary muscle
Ex. digestive system

9. 4. Epithelial Tissue
Interface tissue that forms boundaries between environments and lines surfaces
“epithe-” means “laid on”
Coverings and Protection (ex. skin)
Excretion & Secretion (ex. glands)
Filtration (ex. kidneys)
Absorption (ex. digestive system)

10. Identifying Characteristics of Epithelial Tisues
1. Tight fitting sheets
Regardless of cell shape or number of layers

11. Identifying Characteristics
LUMEN
2. Apical-Basal Polarity
Apical Surface = top surface that borders an “open” space called LUMEN
Basal Surface = bottom surface that borders underlying supportive connective tissue
Connective Tissue

12. Identifying Characteristics
LUMEN
Apical Surface
Often w/ microvilli (brush border)
Increases SA in areas that need to absorb or secrete
Some with cilia to move substances along lumen
Connective Tissue

13. Identifying Characteristics
LUMEN
Basal Surface
Has adhesive sheet of glyco-proteins secreted by epithelial cells called the basal lamina
Connective Tissue beneath secretes collagen, creating the Reticular Lamina.
Basal Lamina + Reticular Lamina = Basement Membrane (defines the epithelial boundary)
LUMEN
Connective Tissue

14. Identifying Characteristics
3. Avascular (a = without)
Lacks blood vessels
Nourished by connective tissue
But Innervated
w/ nerve fibers
4. Regeneration and repair quickly

15. Classification of Epithelial Tissue: Cell Shape
Cross-section
Squamous – flat, like a fried egg, or scale-like
Cuboidal – cubes, large spherical central nuclei
Columnar – columns, long oval nuclei, usually near basal surface

16. Classification of Epithelial Tissue Cell Layers
Stratified (many layers)
Thick
Protective role, subject to wear and tear
Regenerate from basal surface to replace apical surface cells that rub off or die
Cells differ in shape at apical and basal surface. (named for apical surface)
Simple (one layer)
Thin: limited, no protection
Sparse cytoplasm
Found where rapid diffusion is a priority (ex. kidneys, lungs)

17. Pseudo-stratified Shapes vary in height
false
Shapes vary in height
Nuclei at different levels – appear stratified, but aren’t.
All cells reach basement membrane; only a few reach the surface

18. Simple Squamous Epithelium
One layer
Flat
Function and Location
Areas of high diffusion rates:
gasses (ex lungs)
nutrients and waste exchange (blood vessels and surrounding cells)
filtrates (kidneys)
Makes lubricating fluid in lining of body cavities (ex. serous membranes)

19. Simple Squamous Epithelium (Top View) – cells fit like tiled floor

20. Simple Squamous Epithelium (side view/cross section)
– cells look like fried egg
LUMEN
Figure 4.2

21. Kidney
LUMEN
Nucleus of squamous cell

23. Simple Cuboidal Epithelium
One layer
Cubed
Function and Location
Secretion and Absorption
Covers walls of SMALL ducts, glands, kidney tubules, ovaries

25. Cuboidal Cell
Spherical, large nuclei
LUMEN
Basement membrane
Apical surface

26. Basal surface
Spherical, large nuclei
LUMEN
Apical surface

28. Simple Columnar Epithelium
One layer
columns
Function and Location
Absorption & Secretion (ex. digestive tract)
When in open to body cavities – called mucous membranes
Special Features
Often w/ microvilli on apical surface (brush border)
Goblet cells, single cell glands, produce protective mucus.

32. Basal surface
Apical surface
LUMEN

33. Pseudostratified Epithelium
Function
Absorption
Secretion of mucus by goblet cells
Cilia (larger than microvilli) sweep mucus
Location
Respiratory Linings & Reproductive tract

34. LUMEN

35. LUMEN
Cilia
Basement Membrane
Multilevel nuclei

36. Stratified Squamous Epithelium
Multi-layer (thick!)
Flat (only cells on apical surface)
Structure
Cells often cuboidal or columnar below apical squamous layer
Function and Location
Protection
Keratin (protein) is accumulated in older cells near the surface – waterproofs and toughens skin
Location
Skin (keratinized), mouth & throat

39. Dense-Irregular Connective Tissue
keratin
Squamous
Cuboidal
Columnar
Basement Membrane
Dense-Irregular Connective Tissue

40. Transitional Epithelium
Structure
Multi-layer
Basal surface cells are cuboidal or columnar
Apical surface cells vary: changes shape to accommodate for change in volume due to stretching
Function
Allows stretching
Location
Urinary bladder, ureters & urethra

41. Figure 4.10

43. Nervous Tissue

44. Muscular Tissue

45. Glands Cells that secrete or export a product.
Secretion = protein, lipids, hormones, steroids, acids
Endocrine glands (internally secreting)
No duct, release secretion into blood vessels
Often hormones
Thyroid, adrenal and pituitary glands
Exocrine glands (externally secreting)
Contain ducts, empty onto epithelial surface
Sweat, Oil glands, Salivary glands, Mammary glands.

46. Shapes of Exocrine glands
Branching
Simple – single, unbranched duct
Compound – branched.
Shape: tubular or alveolar
Tubular – shaped like a tube
Alveolar – shaped like flasks or sacs
Tubuloalveolar – has both tubes and sacs in gland

47. Modes of Secretion Merocrine Holocrine Released by exocytosis
Gland is not altered (Ex: Sweat glands and salivary glands)
Holocrine
Gland ruptures and releases secretion and dead cells as well.
Sebaceous (ex. oil glands on the face)