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DIAGNOSTIC MEDICINE 2 > 30 – Structure of Skin Lesions > Flashcards

30 – Structure of Skin Lesions Flashcards

1
Q

What are some functions of the skin?

A
  • Enclosing barrier
  • Environment protection
  • Allows motion and shape
  • Temperature regulation
  • Indicator regulation
  • Indicator of general health
  • Storage reservoir
  • Immunoregulation
  • Sensory perception
  • Etc.
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2
Q

What are the 3 ‘big’ layers of skin?

A
  • Epidermis
  • Dermis
  • Subcutis
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3
Q

What are the layers of the epidermis?

A
  • Stratum corneum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
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4
Q

Epidermis

A
  • Outer layer of the skin
  • Dogs and cats: 2-3 cell layers thick except at
    o Foot pads
    o Nasal planum
  • Keritinization/cornification
  • Endpoint terminally differentiated, dead keratinocyte (corneocyte)
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5
Q

What are the main cell types of the epidermis?

A
  • Keratinocytes
  • Langerhans cells
  • Melanocytes
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6
Q

Keratinocytes (epidermis)

A
  • Comprise 80% of epidermis
  • Characterized by keratin intermediate filaments
    o Scaffolding of the cell
    o Keratins: attach to desmosomes and hemidesmosomes
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7
Q

Desmosomes

A
  • Cytoplasmic: anchorage sites for keratin filaments
  • Intercytoplasmic: mediate strong cell-cell adhesion
  • *desmosome-keratin system
    o Imparts tensile strength
    o Mechanical resistance
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8
Q

Stratum basale

A
  • Mitotically active
  • Attach to basement membrane
  • Attach to other keratinocytes
    o Desmosomes
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9
Q

Stratum corneum: structure

A
  • Stacked layers of anucleate, flattened cornified cells
    o Undergo desquamation
  • “Bricks and mortar”
    o Corneocytes and lipids
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10
Q

Stratum corneum: function

A
  • Mechanical protection
  • Barrier to water loss
  • Barrier to permeation of soluble substances in environment
  • *good example of it being destroyed=allergies
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11
Q

In a healthy epidermis: cell production=cell exfoliation

A
  • Replenished in stratum basale
  • Exfoliated in stratum corneum
  • Normal migration: 22 days
  • Normal exfoliation is NOT visible
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12
Q

Langerhans cells (epidermis)

A
  • Antigen processing and present cells
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13
Q

Melanocytes (epidermis)

A
  • Cosmetic entity
  • Barrier against ionizing radiation
  • Scavenger of cytotoxic radicals and intermediates
  • Participates in developmental and inflammatory process
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14
Q

What are some examples of diseases affecting the epidermis?

A
  • Pemphigus foliaceus
  • Ichthyosis
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15
Q

Pemphigus foliaceus

A
  • Autoimmune disease
  • Affects desmosomes
  • Causes pustules
  • Crusting
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16
Q

Ichthyosis

A
  • Congenital skin disorders
  • Causes abnormalities in differentiation of keratinocytes
  • *Golden retrievers: excessive scaling
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17
Q

What is a disease of Langerhans cells?

A
  • Canine cutaneous histiocytomas
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18
Q

Canine cutaneous histiocytomas

A
  • Typically benign masses
  • Young dogs
  • Usually spontaneously regress
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19
Q

What is a disease of melanocytes?

A
  • Colour dilution alopecia
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20
Q

Colour dilution alopecia

A
  • Some dogs with dilute hair coat
  • Blue, fawn, silver
  • Hair shafts have larger than normal pigment granules
  • Leads to hair loss: recurrent skin infections
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21
Q

Basement membrane zone: what is its role?

A
  • *interface between epidermis and dermis
  • Anchors epidermis to dermis
  • Maintains a functional and proliferative epidermis
  • Maintains tissue architecture
  • Wound healing
  • Functions as a barrier
  • Regulates a nutritional transport b/w epithelium and connective tissue
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22
Q

What is a disease of the basement membrane zone?

A
  • Epidermolysis bullosa
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23
Q

Epidermolysis bullosa

A
  • Group of hereditary disorders
  • Targets anchoring complexes of the epidermis
  • Causes ulceration of “stressed” skin
    o Bony prominences
    o Pressure points
24
Q

What does the dermis contain?

A
  • Blood and lymph vessels
  • Nerves
  • Epidermal appendages
25
What does the dermis modulate?
- Wound healing - Structure and function of epidermis
26
Dermal insoluble fibers (dermis)
- Collagenous fibers o Provides tensile strength (accounts for 90% of dermal fibers) - Elastins o Provides elasticity
27
What are some diseases of the dermis?
- Mucin - Ehlers Danlos syndrome
28
Mucin (dermis)
- Glycoprotein in the dermis - Found in higher quantities in the SHAR-PEI dog - Causes wrinkling
29
Ehlers Danlos syndrome (dermis)
- Inherited disorder affecting connective tissue - Fragility and hyperextensibility of the skin
30
Deep infections of dermis
- Will try ‘wall it off’=get a NODULE
31
What are the functions of hair?
- Physical barrier against trauma - Protection from UV radiation - Thermoregulation/insulation - Repelling water - Source of cells for re-epithelization during wound healing
32
What are the components of the hair shaft?
- Medulla: innermost region o Can contain pigment: does NOT influence hair colour - Cortex: middle layer o Contains pigment cells - Cuticle: outermost layer
33
What are 2 examples of tactile hairs?
- Sinus hairs - Tylotrich hairs
34
Whiskers location
- Face, eyebrows - Palmar aspect of carpus on cats - *slow adapting mechanoreceptors
35
Tylotrich hairs
- Scattered amongs normal hairs - *Rapid acting mechanorecptors
36
What are the stages of hair growth?
- *anagen: growth - Catagen: phase of regression - *telogen: phase of rest o Some conditions make it go into this stage for longer (ex. hypothyroid disease) - Exogen: shedding
37
Sebaceous glands
- Distributed through haired skin - Open into hair follicle lumen - Not present: footpads and nasal planum - Most prevalent at: mucocutaneous junctions, interdigital spaces, dorsal neck/rump, chin, dorsal tail
38
Sebaceous glands: produce sebum
- Oily secretion - Keeps skin soft and moist - Helps retain moisture/maintain proper hydration - Gives hair glossy sheen - Forms a chemical barrier against pathogens
39
What is a disease of the hair follicle?
- Alopecia X
40
Alopecia X
- Abnormalities in sex hormone receptor function o Level of hair follicles
41
What is a disease of sebaceous glands?
- Sebaceous adentitis
42
Sebaceous adenitis
- Glands are destroyed by inflammation - Loss of sebum o Severe scaling o Follicular plugging
43
Subcutis
- *deepest and thickest layer - Energy reserve - Thermogenesis and insulation - Protective padding and support - Maintaining surface contours - Steroid reservoir - *attaches directly to musculature beneath
44
Where is the subcutis absent?
- Pinna - External ear canal - Eyelid - Anus
45
What is a disease of the subcutis?
- Post-rabies vaccination panniculitis - Mycobacterial panniculitis - *”draining’ tracts
46
Post-rabies vaccination panniculitis
- Poodles, chihuahuas, Bichon Frises, Maltese - Site of vaccination o Hair loss o Pigmentation o Inflammation
47
Pinnae and external ear canal
- Collects sound waves - Transmits sound waves to tympanic membrane and auditory ossicles - *external ear canal: vertical (at entrance) and horizontal canals o Curve in between them: more pronounced in dog vs. cat
48
Cerumen (external ear canal)
- Normal emulsion that coats the ear canal - Comprised of o Desquamated keratinized squamous epithelial cells o Secretions from cerumen and sebaceous glands o Immunoglobins - *forms a protective barrier
49
Tympanic membrane
- Separates the external canal from the middle canal - Separated into 2 sections o Pars flaccida: upper part which contains small blood vessels (“fleshy”) o Pars tensa: lower part which is where the manubrium of the malleus attaches (can see all the way through it in a healthy ear)
50
Ear disease
- Very common presentation in small animals (especially dogs) - Head shaking, scratching, otic discharge - Signs of otitis media/interna o Facial nerve paralysis o Head tilt o Vestibular signs, etc.
51
Anal sacs
- Paired invaginations of skin o b/w the muscles of internal and external anal sphincters o connected to the surface by a single duct
52
Anal sacs: walls
- fibrous connective tissue - large sebaceous glands - epitrichial sweat glands
53
Anal sac impaction
- More common in small breeds - Etiology is unknown o Change in character: secretion, change in muscle form or fecal form o Retention may be due to: obesity and intestinal disorders
54
Anal sac infections: various reasons
- Recurrent or chronic impaction - Incomplete emptying - Obestity - Fecal contamination - Low tail attachment - Chronic bowel disease - Allergies - Endocrine diseases - *consider all causes of anal pruritus
55
Anal sac neoplasia
- Most commonly adenocarcinoma - Often metastasizes
56
What are the most common presenting complaints for the anal sac?
- *scooting and licking - Other things can cause the SAME SIGNS o Allergies o Tail fold dermatitis o Vulvar fold dermatitis o Perianal fistulae

DIAGNOSTIC MEDICINE 2 (14 decks)

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