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Organology > Skin > Flashcards

Skin Flashcards

1
Q

Definition

A

Largest organ in the mammalian body

Comprised of an epithelial covering, it’s derivatives (hair, glands, horns, hooves, etc.), and associated CT

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2
Q

Functions

A 
Protection
Regulation of body temperature
Secretion
Sensory Organ
Communication
Reflects physiological condition of the animal
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3
Q

Organization

A

Epidermis & dermis

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4
Q

Epidermal cell types

A

Keratinocytes
Langerhans cells
Melanocytes
Merkel Cells

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5
Q

Layers of Epidermis

A 
Stratum basale/germinativum
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
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6
Q

Keratin - types

A

Soft keratin

Hard keratin

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7
Q

Keratinization/Formation of Keratin

A
  1. Synthesis of filaments in stratum basale - synthesizes 2 of 4 keratin subtypes
  2. Aggregation of filaments 0 in superficial cells of stratum spinosum
  3. Stratum spinosum cells form membrane-coating granules that eventually release lipid-rich contents into intercellular space forming a waterproof permeability barrier
  4. Keratohyalin granules - non membrane bound - appear in close association w/filaments in s. granulosum and non-keratin proteins released by them cause keratin to associate into thicker bundles
    Keratohyalin granules also sequester non-keratin proteins (loricrin and filaggrin and keep them separated from other cellular constituents until they are required in stratum lucidum for keratin filaments to form macrofibrils
  5. Degradation of nucleus and loss of cellular organelles - begins in most superficial layer of the stratum granulosum and is completed in stratum lucidum and corneum
  6. formation of a filament-matrix complex of keratin - in stratum corneum
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8
Q

Layers of Dermis

A

Papillary layer

Reticular layer

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9
Q

Dermis - definition

A

= corium
layer of skin immediately deep to epidermis
derived from mesoderm
composed of connective tissue
most accessory structures are embedded in here

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10
Q

Hypodermis

A

subcutaneous layer/superficial fascia that isn’t part of the skin
consist of looser irregular CT
anchors dermis to underlying CT of deep fascia, perocondrium, etc
Depots of fat are here in animals of good condition

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11
Q

Accessory structures of the skin

A

Hair, sweat glands, sebaceous glands
derived from epidermis
anchored in dermis or hypodermis

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12
Q

Function - Protection

A

most important characteristic
barrier between internal and external environments
guards against injury, bacterial invasion, UV damage, desiccation

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13
Q

Function - regulation of body temperature

A

insulation - mediated by hair coat & adipose tissue

heat dissipation - cutaneous blood supply and sweat glands (in some animals)

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14
Q

Function - secretion

A

from sweat, sebaceous, and mammary glands

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15
Q

Function - Sensory organ

A

largest sensory organ of the body

provides pain, touch, pressure, and temperature sensation

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16
Q

Function - communication

A

gives off odors that govern sexual behavior

helps animals ID each other and their territories

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17
Q

Function - reflects physiological condition of the animal

A

may reflect internal and external disease processes

endocrine disorders, nutritional problems (i.e. Vitamin A deficiency)

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18
Q

Epidermis

A

stratified squamous epithelium

ectodermal origin

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19
Q

Keratinocytes

A

majority of cells

arranged in 5 laters

20
Q

Melanocytes

A

derived from neural crest
octopus like
produce pigment melanin from tyrosine
pass melanin to neighboring keratinocytes (don’t retain it) that carry it up thru layers of skin

21
Q

Langerhans cells

A

dendritic cells
in stratum spinosum
play a role in induction of cutaneous immune responses
important in allergic responses - interact w/Ag and migrate to lymph nodes and interact w/T cells

22
Q

Merkel cells

A

ubiquitously distributed in skin of vertebrates
couple w/axon terminals to form mechanoreceptors
can form malignant tumors in cats, but benign tumors in dogs

23
Q

Stratum basale/germinivatum

A

innermost single layer of cuboidal/low columnar keratinocytes
lie against dermo-epidermal boundary

24
Q

Stratum spinosum

A

polyhedral cells
comprise majority of epidermis
appear to have spines/”hairs” protruding from them and connecting them to adjacent cells = desmosomes that hold adjacent cells together

25
Q

Stratum granulosum

A

thin layer
keratinocytes still retain nucleus and basophilic keratohyalin granules and membrane-coating granules
not uniform in distribution
may not be present in thin skin

26
Q

Stratum lucidum

A 
clear layer/lightly stained
thin layer
flattened dead cells
no nuclei or organelles that contain densely packed keratin filaments
only found in thick, hairless skin
27
Q

Stratum corneum

A

outermost layer
keratinized
flattened cells (squamous)
dead cells filled w/keratin filaments embedded in an amorphous matrix
outermost stratum corneum is sloughed off in normal process of wear and tear

28
Q

Soft keratin

A

elastic, desquamates (ex: skin)

29
Q

Hard keratin

A 
more sulfur than soft keratin
less elastic
more permanent
resistant to degradation
does not desquamate (ex: nails, horns, hooves)
30
Q

Papillary layer

A

Dermal layer
subepithelial loose CT
contains thin collagen and elastic fibers in loose networks

31
Q

Reticular layer

A

dermal layer
dense CT
thick type I collagen fibers packaged into large bundles assoc. w/thick elastic fibers
contains epidermally derived hair, sweat, and sebaceous glands
thick in horse and cow
thin in carnivores

32
Q

Squamous cell carcinoma

A

neoplasia of cells in stratum spinosum
Accounts for 15% of cutaneous tumors in the cat and 5% of those in the dog
Usually found in unpigmented or lightly pigmented skin

33
Q

Melanoma

A

Melanocytic tumor
represents 4-7% of all canine neoplasms
most common malignant tumor of canine oral cavity and digits
Early recognition can lead to more successful attempts at removal and ID of grade/stage of cancer
can metastasize to any area of body, esp. lymph nodes and lungs
cats seem much less susceptible to melanoma tumors than dogs

34
Q

Hair

A

dead
produced by living keratinocytes at base of hair (hair bulb)
pigmentation comes from melanocytes

35
Q

Hair follicle

A

sac from which a hair grows and into which sebaceous glands open
Function - insulation, camouflage, sex recognition, social purposes
Types: single and compound

36
Q

Single hair follicle

A

=simple hair follicle
one hair emerges from a single open
found in horse, cattle, pig, sheep
face, ear, distal portion of limbs

37
Q

Compound follicle

A

several hairs emerge from a single opening
cat, dog, sheep (wool growing areas)
consists of a long principle/guard hair and 7-20 soft, smaller, auxiliary (wool) hairs, (undercoat)

38
Q

Structure of hair follicles

A

Hair bulb
Hair shaft
Hair Sheath
Arrector pili muscle

39
Q

Hair bulb

A

=hair root and dermal papilla
located at the base of hair follicle
comprised of germinal matrix cells - give rise to layers of hair and to internal and external epithelial root sheath
dermal papilla: forms center base of hair bulb - sends chemical signals that induce germinal matrix to proliferate, plays an important role in hair growth
hair root: embedded in a hair follicle. contains epithelial cells that actively divide about dermal papilla. Produces 5 cell layers (hair shaft forms inner 3 layers and hair sheath forms outer 2)

40
Q

Hair shaft

A

non-growing portion of a hair that protrudes from skin
consists of inner 3 layers of hair root
characteristics are species specific
Cuticle: hard, thin, outermost layer of hair. comprised of a single layer of flat, keratinized cells w/overlapping edges (interdigitates w/cuticle of internal epithelial root sheath)
Cortex: consists of compact, dead, keratinized cells - form the bulk of hair shaft - pigment may be present
Medulla - central region of shaft - may be absent in some hairs - comprised of flattened cells separated by numerous air spaces

41
Q

Hair sheath

A

outer 2 layers from hair root
inner epithelial root sheath - forms from periphery of germinal matrix - surrounds hair root and ends somewhere around the point of input of sebaceous glands
external epithelial root sheath - adjacent to internal root sheath - similar in structure and continuous with stratum germinativum - upper part keratinized, lower part not

42
Q

Arrector pili muscle

A 
smooth muscle
origin at epidermal/dermal junction
inserts onto the outside of the follicle
contraction --> erection of hair (piloerection)
response to cold, anger, fear
innervated by the sympathetic nervous system
most evolved in furry animals
increases insulation against heat loss
43
Q

Sweat glands - definition and types

A 
=sudoriferous glands
simple, coiled tubular glands
hollow or more or less circular 
walls composed of low cuboidal epithelium
Types: eccrine and apocrine
44
Q

Eccrine sweat glands

A 
small
widely distributed
produce a watery secretion
mainly a mechanism for cooling
restricted to foot pads of carnivores, frog of ungulates, and nasolabial region of ruminants and swine
45
Q

Apocrine sweat glands

A

larger
cuboidal epithelium
produce oily and foamy secretions
most common in the grown, axilla and scrotum of dogs and cats
most numerous and extensive in horses
most common type found in domestic animals
pheromones are produced and emitted by these

46
Q

Sebaceous glands

A

simple, often branched
acinar glands
open into a hair follicle about halfway up the shaft
secrete sebum = lysed cells and accumulated lipids containing precursors of vitamin D; gives hair it’s sheen and acts as a lubricant for skin and hair

Organology (6 decks)

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