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21 fall: histology > Lecture 11 skin > Flashcards

Lecture 11 skin Flashcards

1
Q

Skin functions

A

maintains body temperature

vitamin D synthesis (hormone, not a vitamin)

barrier

  • loss of body fluid
  • mechanical injury
  • noxious agents
  • immunological barriers against pathogen
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2
Q

layers of skin

A

epidermis

dermis

hypodermis (sub Q)

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3
Q

Development of skin

A

epidermis and its appendages are derived from ectoderm

dermis, hypodermis and vascular elements of these tissues are derived from mesoderm

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4
Q

5 layers of epidermis

A
  1. stratum corneum
  2. stratum lucidum
  3. stratum granulosum/ granular layer
  4. stratum spinosum/spinous layer
  5. stratum basale/basal layer
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5
Q

the main parenchymal cell type of the epidermis

A

epidermal keratinocytes

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6
Q

Keratinocytes are characterized by expression of ___

A

cytokeratin genes

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7
Q

keratins proteins encoded by a large ___

A

gene family (54 in humans)

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8
Q

epidermal keratinocytes are considered prototypical ___

A

intermediate filaments

  • larger than actin filaments and microtubules but smaller than myosin
  • play a basic structural role/ provide mechanical strength
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9
Q

type 1 (acid) and type 2 (basic) cytokeratins always form ___

A

heterodimers

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10
Q

basal layer of epidermis expresses Keratin ___

A

5 and 14

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11
Q

granular layer of epidermis expresses keratin ___

A

1 and 10

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12
Q

cytokeratin filaments are anchored by ___

A

desmosomes

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13
Q

DIFC

A

desmosome-intermediate filament complexes

Desmocollin and desmoglein

bind to plakophilin and plakoglobin

which bind to desmoplakin

which bind to intermediate filaments

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14
Q

main categories of skin

A

thick or thin

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15
Q

layers of thin skin

A

stratum basale

stratum spinosum

stratum granulosum

stratum corneum

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16
Q

layers of thick skin

A

stratum basale

stratum spinosum

stratum granulosum

stratum lucidum (extra layer)

stratum corneum

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17
Q

differences between thin and thick skin

A

thick:

5 layers (stratum lucidum)

lack most appendages (hair follicles, sebacous glands, smooth muscle) but does have eccrine sweat glands

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18
Q

Basal Layer

A

germinativum

deepest layer of epidermis

single layer of columnar or cuboidal cells directely attached to the basement membrane by hemidesmosomes

basal cells (basal keratinocytes) are the stem cells of the epidermis

mitosis occurs in vertical manner, one daughter cell ramins basal while the other moves into the stratum spinosum asymmetric division

mitotic activity replenished the cells in the intermediate layers while the most superficial cells (stratum corneum) are shed (homeostasis)

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19
Q

stratum basale are attached to basement membrane by ___

A

hemidesmosomes

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20
Q

what are the stem cells of the epidermis

A

basal cells (basal keratinocytes)

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21
Q

mitosis occurs in a vertical manner in stratum basale, one daughter cell remains basal the other moved into the stratum spinosum. This is called ___

A

asymmetric division

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22
Q

Stratum spinosum

A

“Spiny layer”

irregular, heterogenous

can see “bridges(desmosomes)” between cells

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23
Q

why can you see the desmosomes of stratum spinosum

A

artifact from making the slide

cells retract from each other but stuck at “bridges”

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24
Q

stratum granulosum

A

in thick skin: several layers of flattened cells

in thin skin: can be one layer of cells

keratohyalin granules

-also contain membrane coating lipid granules, secreted by exocytosis onto the surface of the cells, providing a hydrophobic barrier to water

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25
keratohyalin granules
found in stratum granulosum contain **filaggrin,** which associates the cross links keratin filaments
26
Stratum lucidum
only present in thick skin - several layer of flattened dead cells - nuclei begin to degenerate, only faint nuclear outlines present here - cells are constantly shedding from most superficial layer
27
in statrum lucidum, ___ begin to degenerate
nuclei
28
stratum corneum
outermost layer of epidermis cells are completely filled by keratin filaments no longer have nuclei very flat space between cells filled with lipids, giving the appearance of continuous sheet of keratin
29
JEB
junctional epidermolysis bullosa
30
junctional epidermolysis bullosa
-defect in the formation of effective **hemidesmosomes** severe and often lethal genetic disease - very fragile skin, blisters, sloughing, prone to infection - monogenic disease caused by mutations in any: laminin collagen XVII integrin a6B4
31
mutations in what genes leads to junctional epidermolysis bullosa
laminin collagen XVII Integrin alpha6Beta4 (what hemidesmosomes are made out of)
32
loss of function mutation in LAMB3 caused
blistering and infection (staph) and loss of 60% of skin
33
junctional epidermolysis bullosa was treated by
making skin graphs that had the LAMB3 gene corrected
34
melanocytes
neural-crest derived cells produce the dark brown pigment melanin from tyrosine Melanin is synthesized in melanosomes, which then transit along the cytoplasmic extension and are transferred into keratinocytes lie on basal membrane, attached by hemidesmosomes
35
melanin is synthesized in
melanosomes
36
melanosomes transit along the cytoplasmic extensions and are transferred into \_\_\_
keratinocytes
37
melanocytes lie upon the basement membrane between the ___ of the stratum basale
keratinocytes
38
melanocytes send fine processes between other cells and transfer melanin to \_\_\_, mainly to the basal cells
keratinocytes
39
the fine processes of melanocytes invade the ___ and bud off part of the melanocyte cytoplasm, including the \_\_\_
keratinocytes melanosomes
40
melanin protects the chromosomes of the mitotically active basal cells against \_\_\_
UV-induced damge
41
\_\_ produced by the pituitary and the adrenal glands affect pigmentation
hormones
42
langerhans cells
morphologically similar to melanocytes, but are actually immune cells Dendritic cells fine processes form a network between cells where they can eat antigens which enter the epidermis after langerhans cells eat antigen, they will migrate to lymph nodes to “present” antigen to T cells which will initiate an immune response
43
Merkel Cells
neuroendocrine cells derived from epithelial proto-basal cells scattered throughout the stratum basale, mostly found in **thick skin** **“touch cells”**- transmit sensory information via direct innervation
44
merkel cells are found mostly in \_\_\_
thich skin
45
Merkel cells act as \_\_\_
touch sensors- transmit sensory information via direct innervation
46
it is hard to see merkel cells using \_\_\_, easier to see using \_\_\_
light microscope electron microscopy - dense core granules by their immunocytochemical staining profile (express keratin 8)
47
Dermis
thick layer of connective tissue to which the epidermis is attached
48
dermis is akin to ___ in mucosal tissue
lamina propria
49
two sublayers of dermis
papillary layer reticular layer
50
Papillary layer of dermis
wavy surface loose-cell rich connective tissue which fills the gaps (dermal papillae) at the deep surface of the epidermis contains nerve endings, fibroblast, macrophages ect. frequent capillaries fine, not very dense collagen fibers
51
ridges of papillary layer of dermis
dermal papillae
52
reticular layer of dermis
deeper layer of dermis dense and fewer cells thick type 1 collagen fibers, often aggregate into bundles interlacing collagen network, mostly parallel to the epidermis
53
deeper layer of dermis
recticular layer
54
reticular layer of dermis has ___ which form into bundles
Type 1 collagen fibers
55
hypodermis
layer of connective tissue that anchors the dermis to the underlying bone and muscle loose arrangment of collagen and elastin matrix lots of adipose tissue (adipocytes) in the form of small clusters of large masses that make up a cushion of fat
56
hypodermis has lots of ___ tissue that form a “cushion”
adipose
57
loose arrangement of collagen and elastin matrix
hypodermis
58
\_\_\_ anchors the dermis to the underlying bone and muscle
hypodermis
59
Hair follicles
in mammals- covers the entire body except foot pads, penis and nipples - flexible and keratinized structure - root of the hair is anchored in a tubular invagination of the epidermis, hair follicle
60
the root of each hair is anchored in a tubular invagination of the epidermis called the \_\_\_
hair follicle
61
what are some appendages of the epidermis
hair follicle sebaceous gland sweat gland arrector pilli muscle
62
label the hair follicle
63
Hair growth stages
anagen (active growth) catagen (regression) telogen (silent/quiescence) exogen(hair shedding)
64
anagen
active hair growth in mice: lasts around 3 weeks humans: scalp hair: last several years eyelashases/eyebrows 1-4 months
65
catagen
regression hair growth
66
telogen
3rd stage of hair growth quiescence/silent
67
exogen
4th stage of hair growth shedding of hair
68
hair growth is controlled by ___ and ___ factors
hormonal and hereditary
69
in anagen phase of hair growth
stem cells get activated that move deeper into skin and trigger proliferating progenitor cells which make hair
70
the bulge of the hair follicle contains the \_\_\_
follicular epithelial stem cells
71
the bulge of the hair follicle resides in the ___ and is the deepest and most protected place within the epithelial compartment
base of the permanent portion of the follicle
72
induction of a new anagen phase occurs when the dermal papilla recruits one or more \_\_\_
bulge cells
73
in humans hair growth occurs in a ___ pattern
mosaic each individual hair develops independently of its neighbor
74
In species other than humans, hair growth occurs in a \_\_\_
wave pattern (mice) cycles of growth and rest, starting at the head and move towards the tail
75
\_\_ can initiate hair growth
plucking- leads to apoptosis-a bunch of stuff- wave of hair growth **quorum sensing**
76
sinus hair follicles
whiskers (vibrissae) large hairs modified to act as mechanosensors thicker and stiffer then normal hairs hair follicle - surrounded by **blood sinus**
77
what am I
78
\_\_\_ amplifies the movement and allows the mechanoreceptors at the base of the vibrissa to detect extremely small deflections
blood (sinus hair follicle) (whiskers)
79
\_\_\_ offer an advantage to animals when use of non tactile senses is limited
vibrissae | (whiskers)
80
Two types of sweat glands
eccrine (merocrine) sweat glands apocrine sweat glands
81
sebaceous glands
holocrine gland empty their secretory product into the upper part of the hair follicle found in thin skin hair follicles and lips and genitalia alveoli
82
type of gland that the secretory product is essentially the dead cells of the gland itself an example is \_\_\_
holocrine sebaceous glands
83
hair follicle and its associated sebaceous gland form the \_\_\_
pilosebaceous unit
84
What am I
sebaceous gland
85
explain how sebaceous glands work
live in alveoli basal cells are flattened and mitotically active daughter cells accumulate lipids and grow until they break and release their contents (holocrine secretion)
86
Sweat glands
Eccrine (merocrine) sweat glands * empty onto surface of epidermis * found in footpads of dogs and cats, nasolabial region of ruminants * found all over in human * watery secretion -Apocrine Sweat Glands * non actually aprocine- misnomer * milk and odorless secretion * empties into the upper part of the hair follicle (pilosebaceous unit)
87
What is this
eccrine sweat gland
88
where are eccrine sweat glands found
footpads of dogs and cats, the nasolabial region of ruminants all over in humans
89
Eccrine sweat glands is a ___ duct
excretory - empty directly onto the surface of the skin
90
A layer of ___ cells is found between the secreotory cells of the epithelium and the basement membrane in eccrine sweat glands
myoepithelial
91
Apocrine sweat glands
non actually apocrine- misnomer milk and odorless secretion empties into the upper part of the hair follicle (pilosebaceous unit)

21 fall: histology (36 decks)

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