Skin Flashcards
1
Q
what are the functions of the skin
A
-protection
- sensation
- thermoregulation
- metabolic functions
2
Q
how does the skin function in protection
A
from UV, mechanical, chemical, and thermal insult. prevents dehydration; provides physical barrier to microorganisms
3
Q
how does the skin function in sensation
A
-largest sense organ of body; contains receptors for touch, pressure, pain, and temperature
4
Q
how does the skin function in thermoregulation
A
insulation via hair and subcutaneous fat; heat loss facilitated by sweat glands and dermal capillary network
5
Q
how does the skin function in metabolic functions
A
energy stores in subcutaneous fat
- vitamin D synthesized in the skin via sunlight
-maintains homeostasis; sweating and immune defense
6
Q
what are the 3 main layers of the skin
A
-epidermis
- dermis
- hypodermis (subcutis)
7
Q
what does the epidermis consist of
A
keratinized stratified squamous epithelium
8
Q
what are the cells of the epidermis called
A
keratinocytes
9
Q
what are the two types of epidermis
A
thick skin and thin skin
10
Q
what is the character of thick skin
A
highly keratinized, no hair
11
Q
where is thick skin located
A
soles of feet and palms of hands
12
Q
what does glabrous mean
A
lacking hair
13
Q
does the epidermis have blood vessels
A
no
14
Q
what is the epidermis supplied by
A
blood vessels in underlying dermis
15
Q
what is the dermis composed of
A
dense, irregular collagenous connective tissue (type 1 collagen, with elastic fibers
16
Q
how does aging of skin occur
A
progressive damage to elastic fibers from sunlight
17
Q
describe what supplies the dermis
A
highly vascular and contains many sensory receptors
18
Q
what are the 2 layers of the dermis
A
superficial papillary layer and the deep reticular layer
19
Q
describe the papillary layer
A
relatively thin- interdigitates with epidermis
20
Q
what do corrugations do
A
increase surface area for attachment, prevent shear and mechanical abrasion
21
Q
what are epidermal ridges
A
epidermal projections into the dermis
22
Q
what is another term for epidermal ridges
A
rete ridges
23
Q
what are dermal ridges
A
dermal projections into epidermis
24
Q
what is another term for dermal ridges
A
dermal papillae
25
what are fingerprints
large dermal ridges in thick skin
26
what is another word for fingerprints
dermatoglyphs
27
describe the deep reticular layer of the dermis
thicker and less cell than papillary layer
- contains hair follicles, sweat and sebaceous glands
- interdigitates with hypodermic (subcutis)
28
what are langer's lines
thick collagen bundles and elastin fibers in reticular layer form these lines in the deep reticular layer
29
how do skin incisions heal with less scarring
parallel to langer's lines
30
describe the hypodermis
layer of loose, irregular connective tissue and adipose tissue below the dermis
31
what are some other terms for hypodermis
subcutis, superficial fascia, panniculus adiposus
32
what are the vascular plexi
superficial subpapillary plexus, deep cutaneous plexus and deeper subcutaneous plexus
33
where is the subpapillary plexus located
at the junction of papillary and reticular layers
34
where is the cutaneous plexus located
the junction of reticular layer and hypodermis
35
where is the subcutaneous plexus located
deep within hypodermis, largest of the three
36
what is the purpose of the vascular plexi
thermoregulation in fingertips and ears, associated with AV shunts containing glomus bodies
37
what are glomus bodies and what is their function
-thickened regions of smooth muscle in the wall or arterioles surrounded by connective tissue capsule
-bypass capillary bed and reroute blood from arterial to venous circulation
38
how is skin grown and replaced
cells travel from deep germinal layer, mature and be sloughed from superficial epidermis
39
what happens in psoriasis
keratinocyte maturation only takes 1 week, absence of a granular layer and abnormal keratohyaline and tonofibrils
40
what are the layers of the epidermis from deep to superficial
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
41
describe the stratum basale
mitotic layer of cuboidal germinal cells bound to BM by hemidesmosomes
42
how is the stratum basale attached to the underlying dermis
anchoring filaments and microfibrils
43
describe the stratum spinosum
prickle cell layer, cells look spiny; thickest layer of epidermis in thin skin
44
describes the cells of the stratum spinosum
polyhedral cells with prominent intercellular birdges, numerous cytoplasmic processes and lateral folding of cell membrane
45
what do polyhedral cells produce
cytokeratin
46
what does cytokeratin do
forms tonofilaments that aggregate into tonofibrils and anchor to desmosomes
47
describe the stratum granulosum
granular cell layer
- characterized by cells containing basophilic keratohyaline granules
48
what are keratohylaine granules
non-membrane bound electron dense granules
49
what is the keratinization of cells
represents interaction between keratohyaline granules and tonofibrils
50
what is keratinization initiated by
release of lysosomal enzymes ruptures keratohyaline granules and polymerization of their contents forms a matrix for tonofibrils of cytokeratin which results in mature keratin
51
what happens as keratinocytes mature
die and lose nuclei
52
what do cells of the granular layer contain
membrane-bound, lamellar structures called keratinosomes
53
what do keratinosomes contain
glycolipids, provide waterproofing coat for skin cells
54
where is the stratum lucidum present
in thick skin
55
describe the stratum lucidum
homogenous, compact layer of enucleate cells between stratum granulosum and stratum corneum
56
what is the stratum corneum
most superficial layer; thickest layer of epidermis in thick skin
57
describe the cells of the stratum corneum
flattened, enucleate, dead cell remnants called squames
58
what are squames and what is their function
primarily soft keratin that acts as hydrophobic barrier to prevent dessication
59
what is desquamination
exfoliation
60
what are the types of common skin tumors
squamous cell carcinoma, basal cell carcinoma, melanoma
61
what skin tumors are derived from epithelial cells
squamous cell carcinoma and basal cell carcinoma
62
what skin tumors are derived from melanocytes
melanoma
63
what happens in first intention healing
from a clean incision
-incision immediately fills with blood and clots
- within 3-24 hours neutrophils infilatrate clot (acute phase)
-epithelial cells of stratum basale begin mitosis -> epithelial closure within 24-48 hours (reapproximation)
- day 3-7 neutrophils begin to be replaced by macrophagees (transition from acute to subacute phase)
- day 5 incision filled with granulation tissue
- week 2- continued fibroplasia and collagen accumulation ->mature granulation tissue. progressive decrease in inflammation. itching from inflammatory cell products
- month 2- CT scar
64
what are the 3 processes in the transition from acute to subacute phase (days 3-7)
neovascularization, fibroplasia (fibroblasts elaborate collagen), re-epithelialization (epithelial proliferation) -> production of granulation tissue
65
what happens with vitamin C deficiency
collagen breaks down, old scars can re-open and bleed
66
what happens in second intention healing
- clot formation, epithelial cells of stratum basale migrate from edges of wound
- takes 3 weeks to fill a 1 cm wide cut
- in haired skin, migration of cells from external root sheath of hair follicles augments re-epithelialization
- simultaneous proliferation of keratinocytes slowly restores multilayered stratified epidermis
- takes 25 days for cells to mature from stratum basale to stratum corneum -> keratinization
- keratinization of new cells and lifting of scab after 3 weeks
- followed by wound contraction due to myofibroblasts
-in full thickness abrasion or third degree burns, re-epithelialization limited by size of wound
67
when does second intention healing occur
with more extensive loss of tissue where wound edges do not approximate
68
what is a keloid
raised thickened connective tissue scare
69
what is a keloid caused from
excess fibroplasia
70
what does a 1st degree involve
only epidermis
71
what does a second degree burn involve
epidermis and dermis
72
what does a third degree burn involve
all three layers, epidermis, dermis, hypodermis
73
what are melanocytes derived fromm
neuroectodermal dendritic cells in epidermis
74
where are melanocytes found
usually restriced to basal layer
75
where might the cytoplasmic extensions of melanocytes extend into
stratum spinosum
76
what do melanocytes do
produce melanin
77
what is melanin released from and taken up by
released from melanosomes in melanocytes.
-taken up by epidermal cells
78
how do you idenitify melanocytes
dark staining nuclei, clear cytoplasm
79
what are the 2 types of melanin
eumelanin and pheomelanin
80
where is eumelanin found and what do their melanocytes look like
darked haired individuals, elongated melanocytes
81
where is pheomelanin found and what do their melanocytes look like
individuals with red or blonde hair, oval melanocytes
82
describe how melanocytes operate and are distrubuted across peoepl
equal number of melanocytes across people but variable rates of melanin production and degradation by lysosomal enzymes
83
how do light skin people produce and process pigment compared to dark skinned
light skineed produce less pigment or digest pigment faster
84
what is vitiligo
autoimmune disease, destruction of melanocytes -> depigmentation
85
what controls melanin synthesis
melanocyte stimulating hormone (MSH) in pituitary
86
how is melanin synthesized (mechanism)
-tyrosine precursor oxidized to DOPA by tyrosinase located in premalosomes
- DOPA -> melanin in melanosomes
87
what happens with albinos
lack tyrosinase so DOPA and melanin not formed
-premelanosomes form but dont mature
88
what can tyrosinase be used for
as a marker to differentiate melanocytes from keratinocytes containing phagocytosed melanin
- Tumor ID
89
what does melanin do
shield nucleus from UV rays , inhibits mutagenesis
90
what does UV stimulate
melanin synthesis
91
what is melanin necessary for
normal neural development
92
what are langerhans cells
fixed tissue macrophages- phagocytic antigen presenting cells
93
what do langerhans cells contain
birbeck granules
94
where are langerhans cells located
stratum spinosum
95
what are langerhans cells involved in
contact allergic dermatitis
96
what are skin appendages and examples
embyrological outgrowths of epidermis
ex: hair, nails, sebaceous sweat glands
97
what is terminal hair
coarse hair on scalp, axillae and pubis
98
what does the hair shaft consist of
outer cortex and inner medulla
99
what is the hair shaft covered by and what is its function
cuticle of overlapping keratin plates to prevent the matting of hair
100
what is the hair shaft produced by
hair follicles that are downgrowths of epithelium surrounded by collagen sheaths
101
where does hair growth occur
in the deep terminal expansion of follicle called the hair bulb
102
what is the hair bulb lined with
actively dividing epithelial cells homologous of stratum basale
103
what is the dermal papilla and where is it located
it is a finger-like invagination of dermis containing blood vessles and is located at the base of the bulb
104
what happens as epithelial cells lining hair bulb mature
fill with hard keratin filaments arranged in parallel bundles
105
how does hair get color
melanocytes adjacent to hair follicle produce melanin and becomes incorporated into cortex
106
what do the internal and external root sheath do
surround and protect developing hair and line hair follicle
107
what is the glassy membrane
a modified BM separates hair bulb from surrounding epidermis
108
what is the function of hair
thermoregulation and protection
109
what is the internal root sheath made up of
CT
110
what is the external root sheath made of
cellular
111
where is hair absent
on thick skin of palms and soles
112
what are arrector pili muscles
bundles of smooth muscle cells that attach to hair follicle sheath and insert on epidermal ridges
113
what happens when arrector pili muscles contracct
raises hair -> goosebumps
114
what is arrector pili muscle contraction caused by
sympathetic stimulation due to cold, fear, aggression
115
how are arrector pili muscles spatially oriented to the hair shaft
30 degree angle
116
what are the phases of hair growth and what happens in each
-anagen- growth phase
- catagen- involuting phase (loss of blood supply)
- telogen- resting phase
-exogen- shedding of old hair shaft
117
what is vellus hair
fine body hair in children
118
what is androgenic alopecia
most common form of hair loss, genetic and androgen dependent
- high levels of 5alpha reductase, the enzyme that converts testosterone to dihydrozytestosterone results in follicular atrophy
119
where is the nail plate
rests of stratified squamous epithelium of nail bed
120
where is the nail root located
extends into dermis and attaches to periosteum of distal phalanx
121
where does nail growth occur
by proliferation and differentiation of epithelium at nail root in germinative zone of nail matric
122
what is the lunula and what covers it
the white crescent base of nail, covered by superficial cuticle
123
what happens as epthithelial cells mature on the nail
fill with keratin and die forming nail plate
124
what is the nail plate made of
densely packed, hard keratin filaments embedded in amorphous matrix
