Intro to Dermatology Flashcards
(76 cards)
1
Q
What is the Epidermis?
A
- Outermost layer of skin
- Primary defense layer to the external environment
- 85% keratinocytes, also melanocytes, Langerhans’ cells, and Merkel’s cells
- Layers: (deep to superficial)
- Stratum Basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum Corneum
2
Q
What are Keratinocytes? Funtion?
A
- Contain keratin
- Produce cytokines - cutaneous immune response, inflammation, wound healing
- Produce lipids
- capable of phagocytosis
- Held together by desmosomes
3
Q
What is a Melanocyte? Function?
A
- Found in the basal layer of the epidermis, outer root sheath of hair follicles, hair matrix, sebaceous and sweat gland ducts
- Melanocytes produce melanin pigments
- Photoprotective function
- Scavenging free radicals
4
Q
What are Langerhans’ Cells? Function?
A
- Dendritic cells located in the basal layer or suprabasally
- Antigen presenting cells
- antigen specific T-cell activation
- Produce cytokines
5
Q
What is a Markel Cell? Function?
A
- Located int he stratum basale, tylotrich pads, and hair follicle epithelium
- Slow-adapting mechanoreceptors
6
Q
What is the Stratum basale?
A
- Basal layer
- Deepest layer of the epidermis
- Area of active mitosis
- consists of a single keratinocyte cell layer that is in direct contact with the basement membrane zone
7
Q
What is the Stratum spinosum?
A
- Spinous layer
- Cells arise from the basal layer and have prominent intracellular attachment sites called “desmosomes”
- Lipid synthesis occurs
- dispersed into intercellular spaces and a lipid layer surrounds each corneocyte
8
Q
What is the Stratum granulosum?
A
- Granular layer
- Cells are flattened and contain keratohyalin granules
- Granules release profilaggrin, cleaves to filaggrin
9
Q
What is the function of filaggrin
A
- Necessary for organization of keratin intermediate filaments
- Required for effective epidermal barrier function
10
Q
What is the Stratum lucidum
A
- Thin layer of fully keratinized cells
- Present only in footpads and nasal planum
11
Q
What is the Stratum corneum
A
- Most superficial layer
- Fully keratinized cells
- End product of epidermal differentiation where cells lose their mitotic activity and undergo gradual desquamation (constantly shed)
- Cells have cornified cellular envelope that connects the intracellular keratin matrix with the intercellular lipids
- Cells are anucleate, flattened cells that form layers that are permeated by sebum, sweat and lipids
- Impedes external movement of water and electrolytes and serves as a barrier to the entrance of external substances.
- decreases in stratum corneum lipids result in defective barrier function ⇢ increased transepidermal water loss (TEWL)
- Antimicrobial peptides ae a component
12
Q
What is the function of the cornified cellular envelope
A
- Structural support and protection
- Resistance to microorganism invasion
13
Q
What is the Basement Membrane Zone (BMZ)?
A
- The interface between the epidermis and dermis in the BMZ
- Complex structure that has several layers
- Functions of the BMZ:
- Anchors the epidermis to the dermis and maintains a functional epidermis
- Maintains tissue architecture and structural support
- Barrier and wound healing functions
- The site of injury/attack in certain autoimmune disorders ⇢ blister formation
14
Q
What is the Dermis?
A
- Provides tensile strength, elasticity and structural support
- Water and electrolyte storage
- Made up of Fibers, ground substance, cells, appendages and arrector pili muscles, vessels, and nerves
15
Q
What are dermal fibers?
A
- Formed by fibroblasts
-
Collagen (collagenous fibers)
- comprised of multiple protein fibrils
- Main component responsible for skin tensile strength
- 90% of dermal fibers are collagen
- Several types of collagen (most is type I collagen)
-
Elastic fibers
- comprised of protein (cross-linked amino acids) and microfibrils
- Visualized microscopically with special elastin stains
-
Reticular fibers
- similar to collagen
16
Q
What is Dermal Ground Substance?
A
- Interstitial substance of fibroblast origin
- Comprised of glucosaminoglycans and proteins (proteoglycans)
- Water storage
- glucosaminoglycans and proteoglycans bind water
- Passage of electrolytes, nutrients and cells from vessels to the epidermis
- Maintenance of dermal structure
- Fibronectins are glycoproteins that modulate cell interactions, vascular permeability, wound healing
17
Q
What are Dermal Cells
A
- Fibroblasts and dermal dendrocytes
- Mast cells (small #)
- Melanocytes may be present around vessels and hair bulbs
- Sparse neutrophils, lymphocytes, plasma cells, macrophages, eosinophils
- Normally, there are few cells in the dermis
18
Q
What appendages are in the dermis?
A
- Hair follicles
- Hair shafts
- sebaceous glands
- apocrine sweat glands
- Eccrine sweat glands
- Tail gland (supracaudal gland)
19
Q
What are hair follicles?
A
- These are compound in the dog and cat (large primary hairs and smaller secondary hairs all exit through a common opening)
- Outer layer (outer root sheath) is a downward extension of the epidermis
- Hair matrix cells, at the base of the follicle, give rise to the hair
20
Q
What are hair shafts
A
- Comprised of protein
- Primary (guard), Secondary (undercoat) and tactile (whiskers)
- Medulla - cells, glycogen vacuoles, and air
- Cortex - pigmented cells
- Cuticle - outermost layer of flattened cells
21
Q
What are sebaceous glands?
A
- Holocrine
- open through a duct into the hair follicle
- More numerous on dorsal neck, rump, tail, chin, interdigital regions, and mucocutaneous junctions
- Production of oily sebum (triglycerides, cholesterol, phospholipids, fatty acids)
- Sebum has antimicrobial properties
- Sebum-sweat emulsion retains moisture, softens skin, produces sheen, provides physical and chemical barrier
- Androgens cause hypertrophy of sebaceous glands
- Estrogens and glucocorticoids cause atrophy of sebaceous glands
22
Q
What are apocrine sweat glands
A
- Open through a duct into the hair follicle
- Sweat has antimicrobial and pheromonal properties and functions in excretion of waste products
23
Q
What are Eccrine sweat glands
A
- Found only in footpads
- Duct opens onto footpad surface
- May see eccrine seating of footpads in nervous animals
24
Q
What are tail glands?
A
- Dog - oval area on the dorsal tail surface, about 5 cm distal to the anus
- Cat - all along the dorsal tail surface
25
What are arrector pili muscles
* smooth muscle with vacuoles
* Largest in dorsal neck and rump skin
* Contraction causes piloerection (hair stands up)
26
What are the function of blood vessels in the dermis?
* Arise form superficial, middle and deep plexus of arteries and veins
* Supply hair follicles, glands, arrector pili muscles and the epidermis
27
What is the function of lymph vessels in the dermis?
* drain away tissue debris, protein, cells, fluid and have an immunoregulatory function (via linking the skin and regional lymph nodes)
28
What is the function of nerves in the dermis?
* Innervate the blood vessels, hair follicles, glands and arrector pili muscles
* Ara of skin supplied by branches of one spiral nerve is called a dermatome
* Nerves function in sensory perception and maintenance of epidermal viability
29
How does the nervous system sense an ‘Itch’?
* Itch is received by free nerve endings near the dermal-epidermal junction
* Specialized afferent neve fibers transmit the itch sensation to the central nervous system
* Tertiary neurons relay the itch to the level of conscious perception in the cerebral cortex
30
What is the Subcutis?
* Panniculus
* Consists of fat lobules separated by fibrous bands
* Functions:
* Protective cushion
* Structural support
* Energy reserve (steroid reservoir)
* Insulation
* Capillary walls are thinner as compared to those in the dermis and there are no lymphatics present in fat lobules
* fat is susceptible to disease processes from injury because of an inefficient system for removal of damaged tissue
31
How does Hair grow?
* occurs in cycles, rather than continuously
* Stages:
* Anagen - active growth
* Catagen - transitional stage
* Telogen - resting stage
* Exogen - shedding of the hair shaft
32
What factors affect hair growth:
* Photoperiod
* Breed/genetics
* Age (transition from puppy to adult coat occurs anywhere from 3 months up to 9 months)
* Ambient temperature - activity maximal in summer
* Certain cytokines and growth factors
* hormones
* nutrition
* illness/stress
* Drugs
* Location on the body
33
How long does it take hair to grow?
* Medium/Short coats ~ 3-4 months after shaving
* Long coats up to 1.5 years
34
What is shedding?
* Animals in temperate climates may shed heavily in spring and fall
* indoor animals may shed abundantly all year long (artificial light = ⇡ photoperiod
* Follicular activity is maximal in summer and minimal in winter
* Patterns:
* No/minimal shedding
* Continuous shedding
* Seasonal shedding
35
What is Alopecia?
* hair loss
36
What is hypotrichosis?
partial hair loss (partial alopecia)
37
What is hypertrichosis
* excessive hair
38
What are the primary skin lesions
* Papule
* Pustule
* Vesicle
* Wheal
* Nodule
* Macule
* Cyst
39
what is a papule
* pinkish/red, raised, solid, circumscribed elevation of the skin
* 1mm to a few mm in diameter
* Indicative of cellular infiltrate and usually represents an inflammatory lesion
* Common causes in dogs:
* bacterial skin disease (pyoderma)
* ectoparasitism (scabies ,demodicosis, flea bite hypersensitivity
* Common causes in cats:
* hypersensitivity/allergic dermatitis
* infected feline acne
40
What is a pustule
* small, round, epidermal elevation containing pus
* “white head”
* Usually contains neutrophils
* eosinophilic pustules are less common
* Often indicate bacterial infection
* can be sterile ⇢ pemphigus foliaceus
* Fragile and rupture easily
41
What is a Vesicle?
* Small (\<1cm) epidermal elevation containing clear fluid ( ~blister)
* Rarely seen ⇢ occur infrequently and rupture easily
* Causes:
* autoimmune skin diseases
* irritant reactions
* burns
* Vesicular lesions \>1cm = “bulla”
42
What is a Wheal
* Raised, well-circumscribed, edematous lesion
* “hives”, urticaria)
* Overlying skin usually normal
* Persist for minutes to hours (short lived)
* Uncommon in dogs, rare in cats
* Causes:
* insect bites
* hypersensitivity reactions
43
What is a nodule?
* Well-circumscribed, solid lesion that usually occurs deep within the skin
* Numerous causes including inflammatory or neoplastic cellular infiltration
44
What is a Macule
* Circumscribed flat, nonpalpable, small (\<1cm) spot of color change
* A patch is a macule \>1cm
* Can be hyperpigmented, hypopigmented, erythematous, hemorrhagic
* Common in dogs as a post-inflammatory hyperpigmented change
45
What is a cyst
* Epithelium-lined cavity that is filled with fluid or solid material
* Can be soft/fluctuant or firm (follicular cysts are often firm)
46
What are secondary skin lesions
* May evolve from primary lesions
* May occur due to chewing, scratching, trauma
* May occur as a result of infections
* Lesions:
* Epidermal collarette
* Lichenification
* Callus
* Fissure
* Erosion/ulcer
* Scar
* Excoriation
47
What is an epidermal collarette
* Circular ring of scale/peeling keratin
* Often a remnant of a papule or pustule
48
What is Lichenification
* A rough appearance of the skin, usually thickened
* generally from friction and is indicative of chronicity
49
What is a callus
* A thickened, rough, alopecic hyperkeratotic plaque-like lesion
* Commonly seen over bony areas and caused by pressure and friction
* elbow calluses are protective to the underlying bone
50
what is a Fissure
* A linear cleavage into or through the epidermis
* a ‘crack’ in the skin
* Sites include:
* footpads
* ear margins
* nasal planum
* mucocutaneous junctions
51
What is an erosion or ulcer?
* Erosion - epidermal defect that does _not_ penetrate the BMZ and heals without scarring
* Ulcer - Epidermal defect that is deeper than an erosion ⇢ exposes the dermis
* often heals with scarring
* Causes:
* self-trauma
* infection
* neoplasia
* vasculitis
* autoimmune skin diseases
* burns
52
What is a scar
* Fibrous tissue replacement of normal epidermis, dermis, or subcutis
* May result from burns or deep infection
53
what is excoriation?
* lesions resulting from self-trauma (excessive scratching, biting, rubbing)
* Response to pruritus or pain
54
What lesions can be primary or secondary
* Alopecia
* Scale
* Crust
* Follicular cast
* Comedo
* Pigmentary Abnormalities
* Erythema
55
What is alopecia
* Abnormal hair loss
* May be partial (hypotrichosis) or complete
* Causes of Primary:
* endocrine disease
* follicular dysplasia
* Causes of Secondary:
* skin infections
* inflammation
* seelf induced trauma
56
What is scale
* accumulation of skin cells (flakes, dandruff)
* Primary:
* primary seborrhea
* Ichthyosis
* zinc-responsive dermatosis
* sebaceous adenitis
* Secondary:
* non-specific, occurs with many infectious and inflammatory skin conditions
57
What is scale
* accumulation of skin cells (flakes, dandruff)
* Primary:
* primary seborrhea
* Ichthyosis
* zinc-responsive dermatosis
* sebaceous adenitis
* Secondary:
* non-specific, occurs with many infectious and inflammatory skin conditions
58
What is a crust
* Dried exudate, serum, cells, blood, scales ("scab")
* Primary:
* zinc-responsive dermatosis
* primary seborhea
* Secondary:
* dermatoses
* pyoderma
* pruritic dermatoses
59
What is a follicular cast
* A cylindrical accumulation of keratin adhered to and surrounding a hair shaft
* Primary:
* sebaceous adenitis
* Primary seborrhea
* Secondary:
* dermatophytosis
* demodicosis
60
What is a comedo (comedones)
* Plugged follicle containing keratin (sebum an dcornified skin cells)
* Primary:
* Feline acne
* Schnauzer comedo Syndrome
* Primary seborrhea
* hyperdrenocorticism
* Secondary:
* demodicosis
* dermatophytosis
61
What are some Pigmentary Abnormalities?
* Hyperpigmentation
* Post-inflammatory change (secondary)
* Hypopigmentation
* Vitiligo (Primary)
* Melanotrichia
* Leukotrichia
* Keukoderma (non pigmented skin)
*
62
What lesions are annular?
* bacterial folliculitis
* Dermatophytosis
63
What lesions are linear
* Excoriations
* lesions with vessel involvement
* congenital conditions
64
What lesions are serpiginous
* Wavy, undulating margins
* Canine demodicosis
65
What lesions are target shaped
* Target = central healing
* Bacterial folliculitis
* dermatophytosis
66
What history is important to get when dealing with skin lesions?
* Signalment (Coat color!)
* Chief complaint
* Onset of problem
* Progression
* Past response to therapy / current therapy
* Seasonality
* Pruritic or nonpruritic? level?
* Environmental/dietary history
* Other animals/people with
67
What is important to note during the PE when dealing with skin lesions?
* General PE
* Examine skin - lesions
* Configuration?
* Distribution/pattern
* Pruritic or nonpruritic
* Painful?
68
What laboratory tests can be performed for skin lesions
* Skin scrapings
* Flea combing
* Acetate tape impressions
* Hair examination (trichography)
* Cytology
* Culture
* Wood's lamp
* Biopsy and dermatohistopathology
* Allergy testing
* Bloodwork/UA
* Specific tests:
* thyroid function
* Adrenal function
* Antinuclear antibody test
69
What does a skin scrape test for
ectoparasites (mites)
70
What does flea combing test for
* Ectoparasites
* fleas
* Cheyletiella mites
71
What do acetate tape impressions test for
* Ectoparasites (Cheyletiella mites)
* Yeast
72
What does Trichography test for?
* Self-induced alopecia
* Dermatophytes
* Ectoparasites
* Color dilution alopecia
* follicular dysplasia
* hair shaft abnormalities
* hair growth stage
73
What does cytology of the skin test for
* Infection
* bacteria
* yeast
* autoimmune conditions
* neoplasia
* allergies
74
What does a skin culture test for
* dermatophytes
* deeper fungal infections
75
What does Wood's lamp test for
* dermatophytosis
76
What does biopsy and dermatohistopathology test for?
* Definitive diagnostic for:
* dermatoses not responding to appropriate therapy
* Unusual or serious dermatoses (autoimmune conditions)
* Conditions not easily dx w/out biopsy
* persistent ulcertated dermatoses
* Vesicular conditions (rare)
* Dermatoses for which treatment may be dangerous
* Neoplastic lesions
