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116 Cards in this Set
- Front
- Back
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4 basic structural components/layers of skin
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- Epidermis
- Dermis - SQ fat - Adnexa |
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Primary function of skin
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Protection
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4 types of barriers the skin acts as
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- Structural
- Metabolic - Immunologic - Photoprotective |
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6 secondary functions of skin
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- Temperature and BP control
- Sensory perception - Antimicrobial action - Vitamin D production - Pheromone production - Excretory |
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What are most of the protective barriers of the skin provided by?
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Epidermis
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What cells are the epidermis primarily composed of? (3)
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- Keratinocytes
- Merkel cells - Dendritic cells |
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Which epidermal cell type makes up the majority of the epidermis?
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Keratinocytes (90%)
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Correlation between amount of hair and thickness of epidermis
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Inverse
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4 layers of the epidermis
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- Stratum basal
- Stratum spinosum - Stratum granulosa - Stratum corneum |
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Which epidermal layer is the most mitotically active?
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Stratum basal
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What layer of the epidermis provides the major structural barrier of the skin?
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Stratum corneum
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Which layer of the epidermis makes the epidermis impermeable to water?
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Stratum corneum
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3 biochemical pathways that cause cornification
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- Organization of keratin intermediate filaments
- Dispersion of intercellular lipid 'glue' - Cornified envelope around the corneocyte |
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What organizes the keratin fibrils within the cell?
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Filaggrin
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Where is the precursor of filaggrin found?
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Keratohyaline granules
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What synthesizes the lipids used to form the 'glue' used in cornification?
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Lamellar bodies
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Function of the lipids in cornification (2)
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- 'Glue'
- Repels water |
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What do desmosomes primarily hold together?
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Nucleated keratinocytes
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What provides structural support of the corneocyte?
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Cornified envelope
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What connects the intercellular lipid 'glue' with the IC keratins?
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Cornified envelope
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Origin of enzymes that break down the lipid glue used in cornification
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Lamellar bodies
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Why is the lipid glue broken down?
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For desquamation
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What is an inherited cornification disorder called?
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Ichthyosis
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3 examples of an ichthyosis
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- Epidermolytic hyperkeratosis
- Harlequine ichthyosis - Lamellar ichthyosis |
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Abnormality of keratins (term)
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Epidermolytic hyperkeratosis
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Abnormality of stratum corneum (term)
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Harlequine ichthyosis
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Abnormality of cornified envelope (term)
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Lamellar ichthyosis
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Term for an abnormality of epidermal turnover time for a basal cell to become fully cornified
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Idiopathic seborrheic dermatitis
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Cocker Spaniels are predisposed towards which dermatologic disease?
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Idiopathic seborrheic dermatitis
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Which layer of the epidermis acts as the metabolic barrier?
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Stratum spinosum
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What cell in the skin acts to toxify and/or detoxify compounds?
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Keratinocytes
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A keratinocyte can metabolize toxins just as well as a hepatocyte
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A keratinocyte can metabolize toxins just as well as a hepatocyte
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What is the immunologic barrier provided by in the epidermis? (2)
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- Keratinocytes
- Langerhans cells |
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What is the immunologic barrier provided by in the dermis? (3)
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- Dermal dendrocytes
- Lymphocytes - MP |
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Major function of immunologic cells in the epidermis
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Antigen processing
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What is the structural immunologic barrier?
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Stratum corneum
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3 characteristics of the stratum corneum
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- Dry
- Low pH - Constantly renewing |
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What makes up the innate immunologic barrier? (2)
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- Keratinocytes
- Langerhans cells |
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What makes up the adaptive immunologic barrier?
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Langerhans cells
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3 things the photoprotective barrier of the skin is provided by
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- Hair
- Melanocytes - Keratinocytes |
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Two major types of melanin in mammals
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- Eumelanins (brown/black)
- Phaeomelanins (red/brown) |
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Two major functions of melanin
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- Appearance (camo and attractiveness)
- Protection against UV light |
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What does hyperpigmentation occur secondary to? (2)
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- Exposure of melanocytes to UV radiation
- External injury to the skin |
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3 examples of melanocytic diseases
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- Albinism
- Vitiligo - Equine melanoma |
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Four major components of the dermal-epidermal junction
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- Hemidesmosomes
- Lamina lucida - Lamina densa - Fibrillar zone |
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Thin membrane that connects the epidermis to the underlying dermis forming a strong junction
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Dermal-epidermal junction
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What's required for re-epithelialization after an ulcerative injury?
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Basement membrane zone (stroma?)
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2 diseases that affect the basement membrane zone
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- Junctional epidermolysis bullosa
- Bullous pemphigoid |
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Major function of the dermis
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Provide tensile strength
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3 major components of the dermis
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- Collagen
- Elastic fibers - Connective tissue mucins |
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Two major layers of the dermis
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- Adventitial dermis
- Reticular dermis |
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Which layer of the dermis is composed of fine, elastic fibers?
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Adventitial dermis
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Which layer of the dermis is composed of course, elastic fibers?
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Reticular dermis
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A group of glycoproteins produced by fibroblasts
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Collagens
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Function of collagens
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Provide tensile strength to the dermis
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Example of intracellular modification of collagen
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Hydroxylation of proline
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What does the hydroxylation of proline depend on?
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Vitamin C
- Lack of Vitamin C causes scurvy |
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Example of an extracellular modification of collagen
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Crosslinking of collagen molecules
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3 heritable collagen disorders
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- Ehlers-Danlos disease
- Hereditary equine regional dermal asthenia (HERDA) - Feline acquired cutaneous fragility |
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What do heritable collagen disorders cause?
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Extremely distensible skin
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What functions to provide dermis with the ability to recoil after stretching?
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Elastic fibers
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2 things elastic fibers of the dermis are composed of
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- Elastin
- Fibrillin |
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2 components of proteoglycans
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- Protein core
- COH chains |
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What do the COH chains on proteoglycans do? (2)
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- Bind large quantities of water
- Provide integrity of EC matrix |
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What breed has a normally increased amount of proteoglycans in the skin?
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Shar-Peis
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What disease is characterized by an excess of proteoglycan in the skin?
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Papular mucinosis
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What provides blood flow to the epidermis?
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Plexus between adventitial and reticular dermis
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What regulates blood flow to the dermis?
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Plexus between deep dermis and SQ fat
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What supplies blood flow to the hair follicles?
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Plexus in mid-dermis
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What do almost all inflammatory skin diseases start as?
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Perivascular dermatitis
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Inflammation of endothelial walls of vessels
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Vasculitis
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What are the best known malformations of the cutaneous vasculature?
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Hemangiomas
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3 functions of hair follicles
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- Protective barrier
- Attracting mate - Origin of re-epithelialization in wound healing |
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3 types of protection hair provides
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- Structural
- Thermal - Photoprotective |
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3 sections of the hair follicle
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- Infundibulum
- Isthmus - Inferior portion |
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Section of the hair follicle that extends from opening of hair follicle to insertion of the duct of the sebaceious gland
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Infundibulum
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Section of the hair follicle that extends from the sebaceous gland duct to the insertion of the arrector pili muscle
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Isthmus
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Section of the hair follicle that extends from insertion of arrector pili muscle to base of follicle
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Inferior portion
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Which two general types of mammals have simple hair follicles?
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- Omnivores
- Herbivores |
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Which general type of mammal has a compound hair follicle?
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Carnivores
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3 stages of the hair cycle
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- Anagen
- Catagen - Telogen |
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What happens during anagen?
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Active growth
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What happens during catagen?
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Stage between active and no growth
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What happens during telogen?
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Hair doesn't grow but is retained
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Which breed has an anagen based cell cycle?
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Poodles
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Example of a breed that has a telogen-based cell cycle
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Labradors
- Why they shed a lot |
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Two general disease categories associated with too little hair
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- Nonscarring alopecias
- Inflammatory and Scarring alopecies |
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3 types of nonscarring alopecias
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- Hair cycle abnormalities
- Follicular dysplasias - Trauma-induced alopecias |
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Source of follicular dysplasias
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Congenital
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What are hair cycle abnormalities related to?
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Prolonged telogen state
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What disease can cause hair cycle abnormalities?
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Hyperadrenocorticism
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Three sources of follicular dysplasias
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- Color dilute alopecia
- Black hair follicular dysplasia - Chinese Crested dogs |
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2 examples of trauma-induced alopecias
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- Psychogenic alopecia of cats
- Allergic dermatitis |
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2 types of inflammatory and scarring alopecias
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- Direct (inflammation, disease)
- Indirect (disease destroys vasculature providing follicle) |
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What are diseases in which the hair coat is denser than normal and/or the hair is larger and coarser than normal?
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Hypertrichosis
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2 examples of Hypertrichosis
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- Equine hyperadrenocorticism
- Acral lick dermatitis |
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What are sinus hairs AKA?
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Whiskers
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Function of sinus hairs
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Tactile organ
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4 examples of inflammatory and scarring alopecias
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- Bacterial folliculitis
- Dermatophytic folliculitis - Demodectic folliculitis - Juvenile pyoderma ("Puppy strangles" :( |
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Non-innervated holocrine glands associated with hair follicles
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Sebaceous glands
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Fxn of sebaceous glands (3)
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- Lubricates hair shaft as they exit infundibilum
- Adds sheen to coat - May have antibacterial activity |
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Secretion of sebaceous glands
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Sebum
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Two locations that sebaceous glands are not present
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- Nose
- Footpads |
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Disease of sebaceous glands
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Sebaceous adenitis
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Two breeds predisposed towards sebaceous adenitis
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- Standard Poodles
- Akitas |
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Hepatoid glands (define)
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Modified sebaceous glands around the perianal region
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Which glands of the hair follicle are innervated?
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Apocrine
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Inability to sweat
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Anhidrosis
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Major function of apocrine glands in dogs and cats
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Makes 'body odor'
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Major function of apocrine glands in horses
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Sweating
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Where are eccrine glands present?
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Footpads of carnivores
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Function of eccrine glands
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Increases traction
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Band of smooth muscle attached to the hair follicle
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Arrector pili muscle
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Fxn of SQ fat (3)
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- Insulate
- Protect - Store energy |
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Disease of the panniculus
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Injection site panniculitis
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What is SQ fat AKA?
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Panniculus
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