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VET 411: Skin > Skin Development & Microanatomy > Flashcards

Skin Development & Microanatomy Flashcards

(92 cards)

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1
Q

what germ layers is skin derived from

A

ectoderm
mesoderm

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2
Q

what structures are derived from ectoderm

A

epidermis
hair follicles
sweat glands
sebaceous glands
modified glands

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3
Q

what structures are derived from mesoderm

A

dermis + subcutis
- dermal matrix (collagen, elastin, proteoglycans)
- vessels/lymphatics
- nerves
- arrector pili muscle
- subcutaneous fat

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4
Q

what does skin thickness depend on

A

thickness of the DERMIS

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5
Q

what are 3 general causes of increased skin thickness

A
  1. increased cellularity from inflammation
  2. neoplastic infiltrate
  3. matrix deposition/fluid in the dermis
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6
Q

what cell types are present in the epidermis

A
  1. keratinocytes
  2. melanocytes
  3. langerhans cells
  4. merkel cells
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7
Q

function of keratinocytes

A

create a barrier to the outside

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8
Q

structure of keratinocytes

A

stratified (4-5 cell layers)

  • stratum basale
  • stratum spinosum
  • stratum granulosum
  • stratum corneum
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9
Q

basal layers (stratum basale)

A

innermost layer

contains germinal cells that undergo mitosis to form undifferentiated keratinocytes

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10
Q

spinous layer (stratum spinosum)

A

middle 1-2 layers of cells that differentiate into keratinocytes

begin to flatten

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11
Q

granular layer (stratum granulosum)

A

cells that begin producing components of the lipid envelope for the cornified layer

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12
Q

cornified layer (stratum corneum)

A

outermost layer of dead keratinocytes

acts as a barrier to and communicates with the environment

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13
Q

types of cornified layers

A

compact
basket weave

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14
Q

compact cornified layer

A

seen in glabrous (hairless) skin and regions under constant pressure/friction

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15
Q

basket-weave cornified layer

A

seen in normal haired skin

high lipid content causes loose arrangement of keratin lamellae

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16
Q

lipid envelope

A

connects dead keratinocytes together in the cornified layer

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17
Q

what connective structures are used to connect keratinocytes

A

desmosomes
tight junctions
E-cadherins

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18
Q

desmosomes

A

connect keratinocytes to each other
- should NOT be visible in health

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19
Q

spongiosis

A

intercellular edema causing keratinocytes to separate

desmosomes become visible

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20
Q

tight junctions

A

prevent passage of molecules through intercellular spaces to require them to pass within the cells via diffusion/active transport
- maintains health of keratinocytes without needing blood supply

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21
Q

E-cadherins

A

connects keratinocytes to each other, to melanocytes, and to langerhans cells

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22
Q
A
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23
Q

what determines the thickness of the epidermis

A

the thickness of the SPINOUS layer

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24
Q

epidermal thickness vs hair coat

A

glabrous (hairless) = thick epidermis

haired = thin epidermis

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25
is epidermal atrophy common
no, rare caused by hyperadrenocorticism
26
what is epidermal turnover
the time it takes for basal cells to reach the cornified layer takes 3 weeks
27
immunologic properties of keratinocytes
- normal flora/microbiome - antimicrobial peptides - lipids - cytokines/chemokines - express MHC II to act as APCs to T cells in the epidermis
28
epidermal hyperplasia
acanthosis increased thickness of the epidermis caused by chronic irritation (to the cells or the envelope)
29
steps of acanthosis
1. injury/irritation causes rapid basal cell division 2. spinous layer thickens 3. increased turnover rate 4. decreased transit time between layers 5. decreased differentiation 6. changes in granular and keratin layer
30
subacute acanthosis lesions
- hypogranulosis: lack of granular layer (dec. differentiation) - parakeratosis: retention of nuclei in keratin layer
31
chronic acanthosis lesions
- hypergranulosis: adaptation to high turnover - compact hyperkeratosis: compaction of the cornified layer despite haired skin
32
melanocytes
provide pigmentation to the skin and hair coat
33
location of melanocytes
between basal keratinocytes extend dendritic processes that carry melanosomes to surrounding keratinocytes
34
melanosomes
synthesize and store melanin pigments
35
hyperpigmentation
excess melanin stimulating hormone (MSH) caused by chronic irritation or solar exposure
36
depigmentation
loss of skin or hair pigment caused by injury to the dermis-epidermis junction and basal cells OR matricidal cells of the hair bulbs leading to melanocyte damage
37
leukoderma
depigmentation of the epidermis
38
leukotrichia
depigmentation of the hair coat
39
merkel cells
oval receptor cells located in the epidermis synapse with somatosensory afferent nerve fibers to sense light touch, shape, and textures also have a neuroendocrine function
40
what are other sensory cells in the skin
- merkel cells - tylotrich pads - vibrissae
41
langerhans cells
epidermal dendritic APCs used for immune surveillance
42
where are langerhans cells located
in the epidermis and hair follicle epithelium
43
function of langerhans cells
sample antigens from the environment on the skin surface --> detach from the adjacent keratinocyte --> migrate to draining lymph node --> present to lymphocytes to initiate an immune response
44
what type of immune response do langerhans cells initiate
adaptive immune response
45
what is the function of collagen
provide tensile strength
46
what is the function of elastin
provide elasticity
47
what is the function of proteoglycans
provide pliability
48
dermal dendritic APCs
provide immunosurveillance in the dermis sample antigens from dermis --> migrate to draining lymph node --> initiate response
49
what type of immune response to dermal dendritic APCs initiate
adaptive immune response
50
basement membrane zone
complex structure of proteins and glycoproteins that connects the epidermis and dermis NOT visible on H&E
51
dermo-epidermal separation
defects in the basement membrane zone that lead to separation of the dermis from the epidermis
52
panniculus vs subcutis
panniculus - around the panniculus muscle subcutis - underneath the panniculus muscle
53
panniculus muscle
thin muscle layer attached to the skin underneath the dermis
54
panniculus fat
fat located directly below the dermis (above the panniculus muscle)
55
subcutaneous fat
fat located directly below the panniculus muscle (in the subcutis) develops independently of panniculus fat
56
panniculitis
inflammation in the fatty tissue under the dermis (panniculus or subcutis)
57
cellulitis
inflammation of the subcutaneous fat due to infection
58
hair follicles
extensions of the epidermis develops from germinal cells in the epidermis that grow downwards along with keratinocytes
59
infundibulum
superficial portion of the hair follicle that opens into the orifice of the follicle
60
what is the epithelium of the infundibulum
epidermis
61
where are the majority of the immune cells in hair follicles located
infundibulum (CD4 and CD8 T cells, langerhans cells)
62
isthmus
middle portion of the hair follicle that includes the bulge
63
bulge
location of the follicular stem cells and melanocyte stem cells present throughout life forms new anlagen phase and pigmentation of hair shaft
64
supra-bulbar and bulb regions
deepest portions of the hair follicle
65
compound hair follicles
one primary hair follicle + several secondary hair follicles grouped together all hair exits through one follicular opening dogs, cats, rabbits, sheep, goats
66
primary follicles
produce guard hairs
67
secondary follicles
produce undercoat/wool NO sweat glands or arrector pili muscle more secondary follicles = higher quality wool
68
simple hair follicles
one primary hair shaft exits from the follicular opening horse, cattle, pigs, sheep, goats
69
what does hair growth cyclicity depend on
breed: continuously growing vs prolonged telogen seasonal synchronized shedding: daylight and temp body location: mane and tail vs body
70
what controls cyclic growth
growth factors hormones (T4, cortisol)
71
effect of thyroid hormone on hair growth
maintains hair growth and anagen phase hypothyroid --> shuts down hair follicles
72
effect of cortisol on hair growth
initiates anagen phase
73
anagen phase
growing phase - follicles extend down to subcutis - fully developed dermal papilla - hair shaft fully formed/growing
74
do anagen follicles have immune activity
NO - follicular keratinocytes release anti-inflammatory cytokines to counteract IFN-y by preventing follicles from expressing MHC I
75
catagen phase
transition phase - involution of epithelium to initiate detachment of hair bulb
76
telogen phase
resting phase - hair detaches from bulb - shaft is only connected to epithelium by keratin plug (club)
77
exogen phase
old hair is pushed out when new anagen phase begins
78
what controls sweat glands
- hypothalamus - sympathetic NS
79
do rodents have sweat glands
no
80
epitrichial glands
apocrine glands ducts open into hair follicles - barrier - pheromone release - lipid excretion - thermoregulation generalized: dogs, cats, horses, ruminants axillary/inguinal: humans
81
atrichial glands
eccrine glands ducts open directly onto the skin surface - temperature control - "seal" epidermis - secrete electrolytes paw pads/lip/nose: dogs, cats, ruminants generalized: humans
82
modified sweat glands
naslabial glands ceruminous glands (otitis externa) mammary glands anal sac glands mammalian scent glands
83
sebaceous glands
holocrine gland - balls of cells without a lumen; cells in the center undergo cell death located in the mid-dermis and open into the isthmus area of the hair follicle - secrete protective lipids for hair coat/skin - innate immune function - removal of follicular keratin - guide hair shaft through canal - pheromones
84
sebum
contains lipids and dead sebocytes
85
what stimulates sebaceous gland hyperplasia
androgens
86
what stimulates sebaceous gland involution
estrogens glucocorticoids
87
dermal vasculature
3 main plexi: 1. superficial plexus 2. mid-dermal plexus 3. deep plexus
88
superficial plexus
located directly under the epidermis
89
mid-dermal plexus
surrounds the hair follicles at the level of the sebaceous glands
90
deep plexus
located in deep dermis/subcutis
91
vasculitis
acute vascular wall damage leading to infarction/necrosis of the skin
92
chronic vasculitis
chronic, low grade damage leading to ischemia and atrophy of the follicles causing ischemic collagen change

VET 411: Skin (16 decks)

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