1. Tissues -four primary tissue types: 1. Epithelial 2. Connective
3. Muscle
4. Neural

2. Epithelial Tissue = lining epithelium & glands
multiple functions of epithelial tissues:
protection - from dehydration, pathogens
synthesis – e.g. vitamin D
3. regulation - e.g. body temperature
4. excretion - e.g. waste
5. immune response
6. control of permeability – every substance must cross an epithelial membrane first
7. sensitivity – epithelial membranes are well-innervated
lining epithelium = line body surfaces and cavities
glandular epithelium = secretion

3. Epithelial characteristics
Cellularity
Polarity
Attachment
to each other
to connective tissue
Avascularity
Regeneration

4. Epithelial characteristics
1. Cellularity: composed almost entirely of cells held together by cell junctions
-very little extracellular matrix
2. Polarity: possesses an exposed surface the faces the exterior
of the body - apical face
-also has an attached base which is anchored to other tissues -
basal face
-the organelles are not uniformly
distributed

5. Epithelial characteristics Epithelial characteristics
3. Attachment: attached to underlying tissues via the basement membrane
-BM is produced by the basal surface of the cells & connective tissue
-the BM is comprised of two layers
a. closest to epithelial cell = basal lamina
(glycoproteins, laminin and actin)
-acts as a barrier to transport
b. furthest from the epithelial
cell = reticular lamina
-collagen IV bundles produced
by the underlying connective
tissue cells
-provides strength

6. Epithelial characteristics Epithelial characteristics
1. Tight junctions: lipid portions of PMs are bound together by interlocking membrane proteins
-very tight union - prevents passage of water and solutes between the two cells
3. Attachment: also form extensive connections between each other

7. 2. Desmosomes: comprised of
a. plaque of proteins inside the plasma membrane
-the plaque attaches to the intermediate filaments of the cytoskeleton (keratin)
b. cellular adhesion proteins/CAMs called cadherins

8. Epithelial characteristics Epithelial characteristics
3. Gap junctions: two cells held together by proteins called connexons
-connexons are channel proteins
-materials can freely move between the two cells
-passage of materials helps to coordinate the activities of the adjacent cells
e. g beating rhythm of cilia

9. Epithelial characteristics
4. Avascularity: do not contain blood vessels
-must obtain nutrients via diffusion or absorption
5. Regeneration: damaged cells are replaced through differentiation of stem cells located deep within the tissue
-rate of renewal depends on rate of cell death
-stem cells = germinative cells
-these cells are found closest to the basement membrane
-migrate towards the surface and differentiate into epithelial cells

10. Classification of Epithelia
catagorizing epithelial tissue types
A. # of layers
simple = 1 layer
stratified = multiple
**pseudo = 1 layer
B. Cell shape
columnar
cuboidal
squamous

11. Classification of Epithelia

12. Simple Squamous Epithelium
-tile-like cells - cells are thin, flat and irregular in shape = squamous
-simple squamous - most delicate tissue in the body
-found in protected regions where absorption occurs
-many types:
e.g. mesothelium - lines the abdomen
e.g. endothelium - lines heart chambers and vessels

13. Stratified Squamous Epithelium
-stratified squamous - where mechanical stresses are severe
-cells on exposed surfaces may contain keratin – a protein that reduces water loss and provides strength = keratinized epithelium
-non-keratinized epithelium is tough but must be kept moist = e.g. oral mucosa

14. -four types of cells: Stratified Squamous Epithelium – the Epidermis
1. keratinocytes – make up the majority of the epidermis
-epithelial cells that synthesize the protein keratin
2. melanocytes – cells for the synthesis of the light absorbing pigment melanin
3. Merkel cells – neurons that detect pressure
4. Langerhans cells – immune responses

15. 5 layers maximum Stratified Squamous Epithelium – the Epidermis
Stratum Basale/Germinativum
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum

16. Epidermis: layers -stratum basal/germinativum:
-inner most/deepest layer of the epidermis - attached firmly to the basement membrane between epidermis & dermis underneath
- contain germinative stem cells that differentiate into the keratinocytes and melanocytes of the epidermis
-Merkel cells are found in hairless regions- pressure and touch receptors
- stratum spinosum: several layers of keratinocytes
-keratinocytes of the stratum basale migrate into this layer
-keratinocytes are interconnected by desmosome for strength
-keratinocytes can divide to increase thickness of this layer
-melanocytes are common
-Langerhans cells of the immune system also found in the more superficial layers

17. Epidermis: layers -stratum granulosum:
-made up of keratinocytes migrating up from the stratum spinosum
-cells synthesize large quantities of proteins (including keratin) – cytoplasm appears granular
-as more and more keratin is made – keratinocytes become thinner and flatter
-the cells then die and dehydrate

18. Epidermis: layers -stratum lucidum:
-flattened, densely packed cells filled with keratin
-have a glassy appearance because they do not stain well
-present only in the skin of fingertips, palms & soles
B. stratum
lucidum
C. stratum
spinosum
D. stratum
granulosum
A. stratum
corneum

19. Epidermis: layers - stratum corneum: cornu = horn
layers of flattened, dead, interlocking cells
-if large amounts of keratin are present – the tissue is said to be “cornified”
- keratin makes this layer water-resistant - very dry to prevent growth of bacteria
-kept moist by oily secretions from sebaceous glands
-penetration is promoted by attachment to a lipid or dissolution in a lipid-based solutions
-transdermal drug patches – drugs are in oils or lipid-soluble carriers
- moisturizing lotions – only penetrate few first layers of corneum
-takes days to move from germinativum to corneum
-cells will remain in corneum for an additional 2 weeks before being shed

20. Transitional Epithelium
-stratified squamous epithelium that permits stretching
-located in walls of the bladder, renal pelvis and the ureters
e.g. bladder wall - when empty the epi. looks as if it has several layers
-actual number of layers can be seen upon stretching

21. Transitional Epithelium

22. Simple Cuboidal Epithelium
-cells are cubes
-big, round nucleus found in the center of the cell
-found in regions of secretion and absorption
e.g. kidney tubules
pancreas & salivary glands - buffers & enzymes
thyroid follicles - thyroid hormones

23. Simple Cuboidal Epithelium

24. Simple Columnar Epithelium
-height is greater than their width
-oval shaped nuclei found close to the BM & aligned with each other
-simple columnar: found in areas of absorption and secretion
-located in the gallbladder, larger ducts of exocrine glands, gastric pits of stomach
-frequently the apical face is modified with microvilli
e.g. intestinal lining = brush border
-short-lived cells – replaced every 4 to 5 days
-frequently found with Goblet cells (intestine and stomach)

25. Simple Columnar Epithelium
microvilli
wandering lymphocytes

26. Pseudostratified Columnar Epithelium
-pseudostratified columnar: only a single layer despite looking like many
-nuclei are at varying levels - appearance of multiple layers
-BUT basal face of every cell contacts the BM
-exposed apical surface typically bears cilia
e.g. respiratory epithelium

27. Pseudostratified Columnar Epithelium
-these tissues are generally ciliated

28. Type:
Simple squamous
Simple cuboidal
Simple columnar
Pseudostratified
columnar
Stratified squamous
Description:
single layer, flattened cells
single layer, cube-shaped
cells
single layer, elongated
multiple layers, flattened
Function:
filtration, diffusion, osmosis
secretion, absorption
protection, secretion, absorption
protection, secretion, movement of mucus
protection
Location:
lungs, linings of blood
vessels
ovaries, kidneys, certain
glands
linings of uterus, stomach
and intestines
linings of respiratory
passages and reproductive
outer layer of skin, oral
cavity, throat

29. Glandular Epithelium
epithelial cells specialized to produce and secrete substances
gland = single epithelial cell OR multiple cells
two types of glands: 1) exocrine = secrete into ducts
e.g. sweat glands
2) endocrine = secrete directly into bloodstream
e.g. thyroid, pituitary
** one gland is mixed - e.g. pancreas

30. exocrine gland structure:
Unicellular: single-celled glands
e.g. goblet cells
SIMPLE COLUMNAR with GOBLET CELLS
-goblet cells = unicellular exocrine glands that secrete mucus

31. exocrine gland structure:
Multicellular glands – multiple cells grouped together
multicellular glands can be classified based on:
1. Mode of secretion – used by physiologists
Merocrine
Apocrine
Holocrine
2. Consistency of secretion – used by histologists
Serous
Mucus
Mixed
3. Structure – used by histologists
shape of the secretory portion
branching pattern of the duct
simplest multi-cellular gland is a secretory sheet
e.g. gastric epithelium

32. Serous Glands 1. serous - watery fluid that contains enzymes
e.g. saliva – parotid salivary gland

33. Mucus Glands
2. mucous - glycoproteins called mucins that absorb water to form a
slippery mucus

34. Mixed Glands 3. mixed - more than one type of gland cell
-produces different types of secretions - mucus and serous
e.g. submandibular or sublingual salivary gland

35. Connective Tissue
binds structures together
provides support
produces blood
fills cavities
protects organs

36. Connective Tissue components: matrix + cells
-matrix: non-cellular support material
-comprised of extracellular protein fibers – mainly collagens
e.g. 1. collagen fibers (white) – collagen type I
2. elastic fibers (yellow)
3. reticular fibers – collagen type III
4. fibronectin
-plus a ground substance = water + hyaluronan (sugar),
proteoglycans and glycoproteins
-cells: secrete the matrix
-some have become very specialized and make a very
specialized matrix

37. The way I organize Connective tissues
Loose – areolar CT, adipose & reticular
Dense – dense (regular, irregular), elastic
Supportive – bone & cartilage
Fluid – blood

38. Types: 1. Areolar 2. Dense – regular and irregular 3. Adipose
Cartilage
Bone
Blood
Description:
Cells in fluid-gel matrix
Cells in solid-gel matrix
Cells in solid matrix
Cells in fluid matrix
Function:
Binds organs together,
holds tissues, fluids
Protects, insulates and
stores
Binds organs together
Supports, protects,
provides framework
provides framework
Transports gases, defends
against disease, clotting
Types:
1. Areolar
2. Dense – regular and irregular
3. Adipose
4. Cartilage
5. Bone
6. Blood

39. Loose connective tissues: Loose Areolar tissue
-cells are mainly fibroblasts, spaced far apart
-matrix: mostly ground substance + collagen fibers, elastic fibers
-cushions and can be distorted due to loose organization
e.g. found beneath the dermis connecting it to muscle and bone

40. Loose connective tissues: Adipose tissue
-cells = adipocytes (fat storing fibroblasts)
-cushions joints and organs
-stores energy
-insulates
-often found intermixed with areolar tissue

41. Dense connective tissues: types
-most of the tissue is densely packed extracellular matrix fibers of collagen type I
-cells are fibroblasts
-often called fibrous tissue
-two types: 1) dense regular – dense & elastic in nature
e.g. tendons, ligaments
2) dense irregular - interwoven meshwork or fibers
-e.g. dermis of skin, perichondrium of joints
and periosteum of bone

42. Dense connective tissues: Dense Regular Connective
-few fibroblasts
- multiple, closely packed collagen I fibers
- fine network of elastic fibers
e.g. tendons, ligaments

43. Dense connective tissues: Dense Irregular Connective
found in the deepest layers of the dermis = also called the reticular layer (don’t confuse it with reticular tissue)

44. Connective Tissue: The Dermis
-two major components:
1. papillary layer
2. reticular layer
Papillary Layer
-about 1/5th thickness of dermis
-loose areolar connective tissue
-well vascularized and innervated
-dermal projections into the epidermis
= dermal papillae
-some papillae contain Meissner’s corpuscles for touch
-also free nerve endings – project into the
epidermis - sensations of pain, warmth, itching
Reticular Layer (“little net”)
-dense irregular connective – interwoven
collagen bundles plus elastic fibers
-contains blood vessels, nerves,
hair follicles, sweat glands and
sebaceous/oil glands
-also contains lamellated corpuscles
(Pacinian corpuscles) that detect deep
touch and pressure

45. Supportive Connective tissues: Bone & Cartilage
-cartilage & bone
-see your lecture on the skeletal system

46. Fluid Connective tissue: Blood
-cells suspended in a fluid matrix = plasma
-plasma ~ 55% blood volume
-inorganic salts
-organic substances - e.g. sugars, proteins
-cells: 1) RBCs - biconcave, disc-shaped
-contains hemoglobin - 4 globin proteins
+ heme group (iron)
2) WBCs - fight infection
= leukocytes
- many types: a. monocytes/macrophages
b. lymphocytes - T and B cells
c. basophils - histamine
d. neutrophils - 1st at infection
e. eosinophils - allergic response
3) platelets - blood clotting response

47. Membranes -superficial epithelial sheet + underlying connective layer
(called a lamina propria)
-cover & protect
-four types:
1. serous
2. mucous
3. cutaneous
4. synovial

48. 1. Serous membranes
-line the subdivisions of the abdominopelvic cavity and thoracic cavity
-covers, protects and moistens/lubricates
-comprised of an epithelial layer (simple squamous epithelium) called a mesothelium + underlying loose areolar connective tissue
-the mesothelium secretes a watery fluid = serous fluid (separates and lubricates the movement of organs)
-divided into two separate layers: 1)outer parietal layer - lines the cavity
2) inner visceral layer - covers organs
-serous membrane lining the pleural cavity (lungs) = pleura
- serous membrane lining the pericardial cavity (heart) = pericardium
- serous membrane lining the peritoneal cavity (abdomen) = peritoneum

49. 2. Mucous membranes
-line cavities that directly communicate with the exterior environment
e.g. respiratory, urinary, reproductive, digestive
-covers, protects and moistens/lubricates
-epithelial layer (simple squamous, simple cuboidal, simple columnar) is kept moist through production of mucus by glands, other glandular secretions or exposure to fluids (e.g. urine)
-in areas of physical stress = stratified epithelial tissue rather than simple
-connective tissue layer is loose areolar tissue = lamina propria
--supports embedded blood vessels and nerves

50. 3. Synovial membranes
-lines & lubricates the synovial joint cavity - to permit easy movement of bones over each other
-bones are covered by incomplete layers of simple squamous or cuboidal epithelial cells
-some cells within the synovial membrane are phagocytic to remove pathogens
-others are secretory - secrete a watery synovial fluid for lubrication

51. 4. Cutaneous membrane (skin)
-covers the surface of the body
-22 sq. ft or 16% of body weight
-epithelial layer is keratinized stratified squamous = epidermis
-underlying tissue is areolar tissue reinforced with dense connective tissue = dermis
-skin is attached to underlying muscle and bone by areolar tissue + adipose
-skin turns in at the mouth, nasal cavity, anus and urethral and vaginal openings – meets the mucous membranes lining these cavities
1. physical protection: protection from microbes, abrasion, heat
2. chemical protection – keratin - dryness of the epidermis; salt of sweat
3. regulation of water exchange: by sweating
4. regulation of body temperature: thermoregulation
-by sweating & adjusting blood flow through the dermis
5. excretion of wastes -by sweating
6. nutrition – synthesis of vitamin D precursor
-activated in skin, converted to calcitrol in liver
7. sensation: touch, pressure, vibration, pain & thermal
8. immune defense: Langerhans cells of the epidermis

52. Muscular Tissue specialized for contraction
very distinct organelles within the cells
3 types
1. skeletal – voluntary muscle
2. cardiac – involuntary muscle
3. smooth – involuntary muscle

53. Skeletal Muscle: voluntary muscle
-voluntary nervous control
-repeating banding patterns of actin & myosin = striated appearance
-mature cells = multi-nucleated cells – made from fusion of myoblasts
-cells are very long – sometimes called muscle fibers
-cannot divide – but new cells form from differentiation of myogenic stem cells = satellite cells
-attached to bones via tendons

54. Cardiac Muscle: involuntary muscle
-cells are striated but uni-nuclear = cardiomyocytes
-incapable of dividing – PLUS there are no satellite cells
-therefore damaged heart muscle cannot be regenerated
-identified by the presence of intercalated discs
-for cell-cell communication and force transmission

55. Smooth Muscle: involuntary muscle
-lines blood vessels, airways and organs
-non-striated
-spindle shaped cells - single nucleus (uni-nuclear)
-control their own rate of contraction through action of pacemaker cells
-BUT nervous system can also control contraction
-slow, sustained & strong contraction

56. Neural Tissue (Nervous Tissue)
specialized for the conduction of electrical impulses from one body
region to another
two types of neural cells:
1) neurons
2) glial cells – astrocytes, oligodendrocytes, microglia