Background Flashcards
(22 cards)
What are the functions of normal skin?
Protective barrier against environmental insult Temperature regulation Sensation Vit D synthesis Immunosurveillance Appearance/cosmesis
What structures form the skin?
Epidermis Dermis Appendages -hair -nails -sebaceous glands -sweat glands
What four major cell types comprise the epidermis?
Keratinocytes
Langerhan’s cells
Melanocytes
Merkel cells
What is the main function of
a) keratinocytes?
b) Langerhan’s cells?
c) melanocytes?
d) Merkel cells?
a) produce keratin as a protective barrier
b) present antigens and activate T-cells for immune protection
c) produce melanin, giving skin pigmentation and protects cell nuclei from UV radiation-induced DNA damage
d) contains specialised nerve endings for sensation
What are the layers of the epidermis?
Stratum basale (basal cell layer) Stratum spinosum (prickle cell layer) Stratum granulosum (granular cell layer) Stratum corneum (horny layer)
In thick skin e.g. sole, may be fifth layer (stratum lucidum) beneath stratum corneum, consisting of paler compact keratin
Each stage represents a different stage of keratinocyte maturation
Average maturation time approx. 30d
What is the composition of
a) stratum basale?
b) stratum spinosum?
c) stratum granulosum?
d) stratum corneum?
a) actively dividing cells, deepest layer
b) differentiating cells
c) called because cells lose nuclei and contain granules of keratohyaline; secrete lipid into intercellular spaces
d) layer of keratin, most superficial
What kinds of pathology affect epidermis?
Change in epidermal turnover time e.g psoriasis (reduced turnover time)
Change in surface of skin/loss of epidermis e.g. scales, crusting, exudate, ulcer
Changes in pigmentation of skin e.g. hypo/hyperpigmented skin
What is the dermis made of?
Mainly collagen, some elastin and glycosaminoglycans (synthesised by fibroblasts); collectively provide dermis with strength and elasticity Also -immune cells -nerves -skin appendages -vasculature and lymphatics
What kinds of pathology affect the dermis?
Changes to contour of skin/loss of dermis e.g. formation of nodules, papules, skin atrophy, ulcers
Disorders of skin appendages e.g. hair disorder, acne (disorder of sebaceous glands)
Changes related to lymphatic and blood vessels e.g. erythema (vasodilatation), urticaria (inc permeability of capillaries and small venules), purpura (capillary leakage)
What types of hair exist?
Lanugo hair (fine long hair in fetus) Vellus hair (fine short hair on all body surface) Terminal hair (coarse long hair on scalp, eyebrows, eyelashes, pubic areas)
What does hair consist of?
Modified keratin, divided into hair shaft (keratinised tube) and hair bulb (actively dividing cells and melanocytes giving pigment to hair)
What are the phases of a hair follicle growth cycle?
Anagen (long growing phase)
Catagen (short regressing phase)
Telogen (resting/shedding phase)
What pathology may involve hair?
Reduced/absent melanin pigment production e.g. grey/white hair
Changes in duration of growth cycle e.g. hair loss (premature entry of hair follicles into telogen phase)
Shaft abnormalities
What is the nail composed of?
Nail plate (hard keratin) arising from nail matrix at posterior nail fold, rests on nail bed Nail bed contains blood capillaries (give pink colour)
What pathologies may involve the nail?
Abnormality of nail matrix e.g. pits and ridges
Abnormality of nail bed e.g. splinter haemorrhage
Abnormality of nail plate e.g. discoloured nail, thickening of nail
What is the role of the sebaceous glands?
Produce sebum via hair follicles (collectively called pilosebaceous unit)
Secrete sebum onto skin (lubricates/waterproofs skin)
Sebaceous glands stimulated by conversion of androgen to dihydrotestosterone (so become active at puberty)
What pathology may affect the sebaceous glands?
Increased sebum production and bacterial colonisation e.g. acne
Sebaceous gland hyperplasia
What is the function of sweat glands?
Regulation of body temp
Innervated by SNS
What are the types of sweat gland?
Eccrine
-universally distributed in skin
Apocrine
-found in axillae, areolae, genitalia, anus (modified forms found in external auditory canal)
-only function from puberty onwards
-action of bacteria on sweat produces body odour
What pathology may involve the sweat glands?
Inflammation/infection of apocrine glands e.g. hidradenitis suppurativa
Overactivity of eccrine glands e.g. hyperhidrosis
What are the stages of wound healing?
Haemostasis
Inflammation
Proliferation
Remodelling
What are the mechanisms of
a) haemostasis?
b) inflammation?
c) proliferation?
d) remodelling?
a) Vasoconstriction and platelet aggregation
Clot formation
b) Vasodilation
Migration of neutrophils and macrophages
Phagocytosis of cellular debris and invading bacteria
c) Granulation tissue formation (synthesised by fibroblasts) and angiogenesis
Re-epithelialisation (epidermal cell proliferation and migration)
d) Collagen fibre re-organisation
Scar maturation
