1. Integument—a fancy word for skin
Rachel Boggus

2. Skin What are the functions of skin? (4 things)
What is considered part of the skin? (VERY GENERALLY)

3. Skin What are the functions of skin?
Protective barrier
Prevents desiccation of the body
Temperature regulation
Sense organ
What is considered part of the skin? (VERY GENERALLY)
Epidermis, dermis, and hypodermis (sometimes)

4. Epidermis What type of epithelium? What does it give rise to?
What are the different cell types?

5. Epidermis What type of epithelium? What does it give rise to?
Statified squamous, keratinized
What does it give rise to?
Accessory organs—hair, nails, sweat glands (eccrine and apocrine) and sebaceous glands
What are the different cell types?
Keratinocytes—most cells
Melanocytes—form pigment
Langerhans cells—immune reactions
Merkel cells—related to specialized innervation

6. Dermis
What does it include?
What are the two layers?

7. Dermis What does it include?
Collagen fibers and elastic fibers, GAGs (proteoglycans), fibroblasts, nerve endings, blood vessels, lymphatic vessels, smooth muscle
What are the two layers and their features?
Papillary layer—loose irregular CT below basement membrane
Reticular layer—dense irregular CT

8. Back to the Epidermis What are the 5 layers?
What is the predominant cell type that undergoes differentiation in these layers?

9. Back to the Epidermis What are the 5 layers?
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
What is the predominant cell type that undergoes differentiation in these layers?
The keratinocyte

10. The changing keratinocytes
What do keratinocytes look like in the stratum basale (both LM and EM)?

11. The changing keratinocytes
What do keratinocytes look like in the stratum basale (both LM and EM)?
LM—single basal layer—cells cuboidal columnar and basophilic
Sometimes undergoing mitosiskeratinocytes for other strata
EM—keratin filaments abundant in the cytoplasm, also have many free ribosomes

12. Nice LM of the stratum basale

13. Stratum Spinosum
Describe this layer in the EM and LM?

14. Stratum Spinosum Describe this layer in the EM and LM?
LM—cells become polygonal and flattened, several cells thick with lots of intracellular bridges—where desmosomes are present
EM—increase in number of desmosomes with increased cytoplasmic bundles (tonofibrils)
Membrane coating granules (MCG) appear in the cytoplasm of keratinocytes in upper layers of stratum spinosum
First appear near the golgi Apparatus

15. EM of stratum spinosum

16. LM of stratum spinosum

17. Stratum Granulosum
Describe this layer in both the light microscope and electron microscope

18. Stratum Granulosum
Describe this layer in both the light microscope and electron microscope
LM—large basophilic and irregularly shaped keratohyalin granules numerous
EM—KHGs are large, irregularly shaped not bounded by cell membrane, MCGs more numerous, migrate to periphery
So have both keratohyalin granules AND MCGs

19. LM stratum granulosum

20. Stratum lucidum
Describe its appearance in both EM and LM

21. Stratum lucidum Describe its appearance in both EM and LM
LM—nuclei not evident in flattened cells with pale if any staining
EM—organization of keratin filaments more regular

22. Stratum corneum
Describe in EM and LM

23. Stratum corneum Describe in EM and LM
LM—cells flattened and scale like, cytoplasm uniform and acidophilic, no nuclei
EM—orderly aggregated Keratin filaments
Cell envelope—formed in cytoplasm adjacent to plasma membrane
Lipids from MCG cross-link to cell enveloperesists fluid penetration

24. LM of Stratum lucidum and stratum corneum

25. Melanocytes Where do they originate from?
How do they deliver melanosomes? What is the process called?
What are melanosomes?

26. Melanocytes Where do they originate from?
Neural crest cells
How do they deliver melanosomes? What is the process called?
Via dendritic processes extending between keratinocytescytocrine transfer
What are melanosomes?
Vesicles in which melanin is formed

27. More on melanosomes
They contain the enzyme tyrosinase which takes tyrosineDOPAdopaquinone
What happens in dark skin vs. light skin?

28. More on melanosomes
They contain the enzyme tyrosinase which takes tyrosineDOPAdopaquinone
What happens in dark skin vs. light skin?
In dark skin melanosomes remain as single structures retained by keratinocytes
In light skin—melanosomes aggregate and are degraded by hydrolytic enzymes from lysosomes in stratum spinosum

29. EM of melanosomes (labled 5)

30. Langerhans Cells Macrophage of the skin
Most frequent in the stratum spinosum

31. Merkel cells Found in stratum basale Maybe mechanoreceptors
Many dense core granules may contain neurotransmitters

32. Do you have thick skin?
What is different about thick skin vs. thin skin?

33. Do you have thick skin?
What is different about thick skin vs. thin skin?
Thick skin lacks hair follicles and sebaceous glands
Two layers of skin are bound to each other by epidermal ridges—rete pegs and dermal papillae

35. Dermis
Describe the papillary layer?
Describe the reticular layer?

36. Dermis Describe the papillary layer? Describe the reticular layer?
Just below epidermis and includes dermal papillae. Loose irregular ct and includes collagen, elastic fibers, GAGs, fibroblasts, etc
Describe the reticular layer?
Dense irregular ct (thicker than papillary layer) collagen, and other ct constituents

38. Blood vessels of the dermis
Found in 2-3 plexuses
Subpapillary plexus—at the junction of the papillary and reticular layerscapillaries in papillary layer
Cutaneous plexus—at junction of reticular layer and hypodermis
Third plexus below hypodermis

39. Nerve endings
What are the different types?

40. Nerve endings What are the different types and what are they for?
Pacinian corpuscles—deep pressure
Meissner’s corpuscles—light touch
Free nerve endings—pain, fine touch, heat and cold receptors
Ruffini corpuscles—in collagen fibers, respond when fibers are mechanically stressed/displaced

41. Pacinian corpuscle – green arrow
For the gunners: whats the blue arrow?

42. COWS Circle Of Wavy Shit
Peripheral nerve – this one is cut in cross section

43. Meisner’s Corpuscles - green

44. Accessory Organs Hair– what is vellus hair vs. terminal hair
What are follicles?

45. Accessory Organs Hair– what is vellus hair vs. terminal hair
Vellus hairpeach fuzz
Terminal hairthicker hair, formed from vellus hair
What are follicles?
Invagination of epidermal cells into the dermis
Formation induced by protrusion of dermis, dermal papilla into the hair bulb

46. More hair crap
What are the epidermal cells adjacent to the dermal papilla called?
What are they?

47. More hair crap
What are the epidermal cells adjacent to the dermal papilla called?
Matrix cells
What are they?
Proliferative cells that correspond to the stratum basale
They give rise to different layers of the hair shaft—medulla, cortex and cuticle

48. What layers of the epidermis can be seen where on the hair?

49. What layers of the epidermis can be seen where?
Upper 1/3—all layers of the epidermis are evident
Middle 1/3—only lower two layers of epidermis
Lower 1/3—limited only to basal layer—continuous with the hair bulb

50. I thought we needed a picture
Don’t worry, there will be plenty more later on

51. What happens to matrix keratinocytes?
When they proliferate they form hard keratin
Matrix cells peripheral to the cells forming the hair shaft form the internal root sheath that surrounds the hair shaft within the follicle.

52. Hair crap just goes on and on…
What are epidermal cells that form the hair follicle called?
And the dermis surrounding the hair follicle is called?
What about the basement membrane?

53. Hair crap just goes on and on…
What are epidermal cells that form the hair follicle called?
External root sheath
And the dermis surrounding the hair follicle is called?
Connective tissue root sheath
What about the basement membrane?
Glassy membrane… its really thick
Between external root sheath and connective tissue sheath

54. ALMOST FINISHED WITH HAIR
What is the arrector pili muscle?

55. ALMOST FINISHED WITH HAIR
What is the arector pili muscle?
Bundle of smooth muscle attached to connective tissue of the follicle and the basement membrane of epidermis
Contraction in response to cold or fear makes the hair erect

56. Phases of hair growth
And of course they couldn’t just call the phases of hair growth growing, receding, and resting because that would make sense.
Instead, its anagen, catagen, and telogen
At the end of anagen(growing) the catagen (receding) phase begins with follicle receding toward epidermal surface, dermal papilla lost
During telogen—hair shaft is released
Then the next anagen phase begins as new papilla formed and new hair shaft arises

57. See papilla so it must be anagen

58. Sebaceous glands Simple, branched acinar glands
Derived from outpouching of basal cells in upper 1/3 of hair follicle
Glands secrete by HOLOCRINE mode of secretion
Lack myoepithelial cells
Become active during puberty
Acne is caused by obstruction of these glands

59. Sebaceous glands galore

60. Sweat glands Eccrine (merocrine) sweat gland
Simple, coiled, tubular glands
Numerous, assoc. with skin all over the body
Two types of secretory cells?

61. Sweat glands Eccrine (merocrine) sweat gland
Simple, coiled, tubular glands
Numerous, assoc. with skin all over the body
Two types of secretory cells?
Light (clear) cells—more numerous than
Mucous (dark) cells—responsible for secretory product

62. Sweat
What does sweat consist of?

63. Sweat What does sweat consist of? Water and sodium chloride
Secretion from light cells released from apical surface of cells and into intercellular canaliculi
Between the base of the secretory cells and the basal lamina are myoepithelial cells—resemble smooth muscle
Ducts of glands extend to epidermal surface lined by stratified cuboidal epi.
Duct cells active in reabsorption of NaCl ions from secretory product
Reabsorption regulated by aldosterone

64. Duct
Secretory portion

65. Apocrine sweat gland Simple branched coiled tubular glands
Where are they located?
How are they different from eccrine glands?

66. Apocrine sweat gland Simple branched coiled tubular glands
Where are they located?
Axilla, pubic, areola, and circumanal regions
Note: I have a funny story to tell here, don’t let me forget
How are they different from eccrine glands?
Larger lumens, only one type of secretory cell present
Acidic secretory granules often visable

67. DUCT
SECRETORY PORTION

68. Nail Composed of nail plate with root and free edge
Nail consists of scales of cornified cells
What is the eponychium?
Hyponychium?

69. Nail Composed of nail plate with root and free edge
Nail consists of scales of cornified cells
What is the eponychium?
Region where nail emerges from epidermis at the junction with the stratum corneum
Hyponychium?
Where nail leaves nail bed to form free edge

70. Nail the nail

71. Image review
Get ready….

72. Layers of skin – what you need to know
Epidermis (basale, spinosum, granulosum, lucidum, corneum)
Dermis (papillary layer, reticular layer)
Basically just CT
Hypodermis
Contains a lot of adipose

73. Sweat glands Apocrine and eccrine Secretory portion Duct
Myoepithelial cells
Eccrine have flat-topped epithelium and are found EVERYWHERE
SIMPLE coiled tubular
Apocrine have rounded/rough looking tops and are found in your pits and private areas
BRANCHED coiled tubular

74. Hair follicles Associated with smooth muscle of arrector pili muscles
Also associated with sebaceous glands that DO NOT have myoepithelial cells

75. A little embryo action
Keratinocytes (corneum, lucidum, etc. etc.), hair follicles, sweat glands, sebaceous glands from ECTODERM
Epidermal stuff
Fibroblasts, smooth muscle cells, macrophages from MESODERM
Dermal stuff

76. Thick skin – a ton of corneum; soles of feet and palms

77. Close up
Pap. layer
Retic. layer

78. More thick skin
The elusive lucidum

79. corneum
lucidum
granulosum
spinosum
basale

80. lucidum
granulosum
spinosum
basale

81. Epidermal pegs/rete pegs (white) – epidermis that bulges into dermis; anchor epidermis to dermis; dermal papillae (blue) is the dermis that bulges into epidermis. Got it?

82. dermis Papillary layer on top Reticular layer on the bottom Looser CT
Contains blood vessels, nerve endings (esp. in dermal papilla)
Reticular layer on the bottom
Denser CT (dense irregular CT)

83. Thin skin – only a few corneum layers
Another clue = see hair and oil glands

84. Now time for its close up of thin skin; notice the brown melanin pigment

85. Hair follicle – must be thin skin

86. Cross section hair follicle and oil gland

87. Sebaceous glands – NOT in thick skin

88. So much shit Oil gland Sweat gland Thin skin Reticular layer of dermis
Adipose in hypodermis

89. Blue = smooth muscle of arrector pili, note that’s its near a sebaceous gland

90. Apocrine sweat glands – rough tops

91. Remember the meissners corpuscle for touch in the dermal papillae???

92. Pacinian corpuscle in the dermis-hypodermis junction – onion rings

96. Thick skin showing epithelial detail
Thick skin showing epithelial detail. Cornified (keratinized) stratified squamous epithelium makes up the epidermis. The stratum granulosum is very dark; the stratum lucidum is bright red. The stratum corneum is thick, and very pale.

97. Detail of epithelium of thick skin from the superficial to deep:
pale stratum corneum
bright red stratum lucidum
purple stratum granulosum
stratum spinosum

98. THIS WAS ON OUR EXAM
Many desmosomes between cells (arrows). The cell membranes of the two cells are repeatedly interdigitated, giving the appearance of "intercellular bridges" in light microscopy. These bundles of keratin filaments are called TONOFIBRILS.

99. Detail of epithelium of thin skin, showing melanin in the basal layer
Detail of epithelium of thin skin, showing melanin in the basal layer. The pigment is produced by stellate shaped melanocytes of the dermal layer and then deposited in the basal cells of the epidermis. Melanocytes are of neural crest origin and have to be specifically stained in order to be seen.

100. Thick skin – check out the corneum

102. Papillary (finer strands) vs
Papillary (finer strands) vs. reticular (thicker collagen strands) dermis

103. Meissners corpuscle in dermal papilla: This is a touch receptor

104. Meissner’s

105. The secretory portions of several sweat glands lie in clusters among the fat cells of the hypodermis, low in the picture. A Pacinian corpuscle is in the same area. These are the eccrine sweat glands of skin – they secrete their watery fluid by merocrine secretion.
pacinian
Eccrine sweat

106. Notice that the last slide was thick skin
Notice that the last slide was thick skin. It DOES have sweat glands, just no hair follicles or oil glands. Think about it. Does anyone you know have hairy feet? I hope not. Also, makes sense why the lotion business is huge – no oil glands on hands!

107. Eccrine sweat glands and ducts

108. Detail of sweat gland. The darker circles in the lower part of the field are ducts; the lighter cross-cuts above are the secretory portions.

109. Eccrine sweat gland

110. The ducts are distinguished by their stratified cuboidal appearance and the fact that they are much denser

111. eccrine

112. eccrine

113. Apocrine – ruffled tops… where are these found??? ;)

114. apocrine
                                                         

115. Apocrine!

116. Apocrine sebaceous

123. (1) hair shaft; (2) connective tissue sheath; (3) external root sheath; (4) internal root sheath; (5) dermal papilla; (6) germinal matrix

125. Hair follicles of scalp, with associated pale sebaceous glands
Hair follicles of scalp, with associated pale sebaceous glands. The follicles extend down into the hypodermis, which is largely adipose tissue. Notice the arrector pili (orange) muscle running diagonally toward the upper right-hand corner of the field.

126. At the base of a hair follicle sebaceous glands (red) are found
At the base of a hair follicle sebaceous glands (red) are found. These glands secrete oil into the follicle. They secrete via a process called "holocrine secretion" in which the cell fills with secretory material and then essentially distintegrates; the whole cell is shed

127. Detail of sebaceous gland
Detail of sebaceous gland. Cells look foamy because of loss of lipid droplets during tissue fixation. This gland exhibits holocrine secretion, in which whole cells swell up, degenerate, and are desquamated. The secretion is emptied into the hair follicles and eventually reaches the surface of the skin.

129. Identify the layer identified by the arrow

130. Hints:
You are in the epidermis
Answer: Stratum spinosum
You know because you could see the intracellular bridges

131. Identify

132. Hints: This is cut in cross section!
Answer:
It’s a hair follicle

133. Identify

134. Hints: Answer: It’s a pacinian corpuscle
You know because of its onion-like appearance

135. Identify

136. Answer: Arrector Pili muscle
Hints:
What can you see on the slide?
What type of tissue is it?
Answer: Arrector Pili muscle

137. Identify

138. Is it associated with a hair follicle?
Hints
What type of tissue?
Is it associated with a hair follicle?
Answer:
Eccrine gland

139. What is indicated by each arrow?

140. Hints Answer: What is the main structure in the image?
Blue arrow—vascular pole
Green arrow—urinary pole

141. Identify

142. Hints:
C-shaped cartilage
Answer:
trachea

143. Identify

144. Hints
epithelium
Presence of glands
Answer:
False vocal fold/cord

145. Identify

146. Hints What type of tissue? Is it associated with hair? Answer:
Sebaceous gland
What mode of secretion?
Holocrine

147. Identify blue arrow

148. Hints:
Where are you?
Answer:
Rete pegs/epidermal ridges

149. Identify

150. Hints:
Layer of epidermis
Answer:
Stratum basale

151. 1? 2?

152. (1) arrector pili muscle; (2) sebaceous gland

153. What is at the white arrow and what layer(s) of the skin are shown in this image?

154. sweat gland (secretory unit and duct) in the hypodermis

155. What type of skin is this?

156. THIN!!!!!!! – you can see a snip of arrector pili at the bottom as a clue!

157. Identify the multicellular structure at the tip of each of the numbered arrows.

158. (1) Meissner's corpuscle; (2) dermal papilla

159. What is the brown material at the tips of the arrows?

160. MELANIN

161. WHEW!!!!