Normal skin and skin appendages Flashcards
List the functions of normal skin
Protective barrier against environmental insults Temperature regulation Vitamin D synthesis Sensation Immunosurveillence Appearance/cosmesis
Describe the structure of skin
Epidermis
Dermis
Subcutaneous tissue
PLUS
Skin appendages
Describe skin appendages
Formed by skin derived cells
Hair, nails, sebaceous glands, sweat glands
List the 4 main cell types in the epidermis
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
What is the main function of keratinocytes
Produce keratin (protective barrier)
What is the main function of melanocytes
Produce melanin - skin pigment and protection from UV DNA damage
What is the main function of Langerhans cells
Present antigens and activate T lymphocytes for immune protection
What is the main function of merkel cells
Contain specialised nerve endings for sensation
What is the average epidermal turnover time
30 days
List the 4 layers of the epidermis from inside to outside
Stratum basale - actively dividing cells (deepest layer)
Stratum spinosum - differentiating cells
Stratum granulosum - Cells lose their nuclei and contain granules of keratohyaline - secrete lipid into intercellular spaces
Stratum corneum - Horny layer - Layer of keratin (most superficial)
What does each layer of epidermis represent
Different level of maturation of keratinocytes
Describe the 5th layer of epidermis found in areas of thick skin such as the sole
Stratum lucidum
Found under stratum corneum
Consists of paler, compact keratin
Describe the structure of the dermis
Collagen Elastin Glycosaminoglycans Immune cells Nerves Skin appendages Lymphatics Blood vessels
List the 3 types of hair
Lanugo - fine long hair in fetus
Vellus - short fine hair all over body
Terminal - coarse long hair
Describe the structure of hair
Consists of modified keratin
Contains hair shaft - keratinized tube
Hair bulb - actively dividing cells and melanocytes which give pigment to the hair
Describe the growth cycle of hair
Anagen (long growing phase)
Catagen (short regressing phase)
Telogen (resting/shedding phase)
Describe the structure of the nail
The nail is made up of a nail plate (hard keratin) which arises from the nail matrix at the posterior nail fold, and rests on the nail bed.
The nail bed contains blood capillaries which gives the pink colour of the nails.
Describe the structure of a pilosebaceous unit
Sebaceous gland plus hair follicle
What is the function of the sebaceous glands
Produce sebum - lubricates and waterproofs the skin
What stimulates sebaceous glands?
Conversion of androgens to dihydrotestosterone
What is the function of sweat glands
Regulate body temp
What are sweat glands innervated by?
Sympathetic nervous system
Name and describe the 2 types of sweat gland
Eccrine - all over body
Apocrine - axilla, areola, anus, genitalia and modified ones in external auditory canal
Describe the four stages of wound healing
Haemostasis - vasoconstriction, platelet aggregation, clot formation
Inflammation - vasodilation, migration of neutrophils and macrophages, phagocytosis of cellular debris and invading bacteria
Proliferation - granulation tissue formation and angiogenesis, re-epithelialisation
Remodelling - collagen fibre re-organisation and scar maturation
