Intro to derm Flashcards
What are the layers of the skin?
Epidermis
Basement membrane (dermal-epidermal junction)
Dermis
Subcutaneous fat
What is the epidermis composed of ?
Keratinocytes
What are the layers of keratinocytes?
Progressive differentiation / flattening towards surface:
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum (palms and soles only, no nuclei or organelles)- skin thicker on palms and soles.
Stratum corneum (no nuclei or organelles)
How long does cellular progression in epidermis from basal layer towards surface take?
30 days, but accelerated in certain skin diseases
What type of cell are melanocytes?
Dendritic
What do melanocytes do?
Distribute melanin pigments (in melanosomes) to keratinocytes
What type of cells are Langerhans cells?
Dendritic APCs
What type of receptors do Merkel cells have?
Mechanosensory receptors
What are the 2 layers of the dermis? (top to bottom)
Papillary dermis
Reticular dermis
What makes up 80-85% of the dermis?
Collagen, mainly types 1 and 3
What makes up 2-4% of the dermis?
Elastic fibres- fibrillin and elastin
What glycoproteins are in the dermis?
fibronectin, fibulin, intregrins
What do glycoproteins in the dermis do?
facilitate cell adhesion and cell motility
Where is ground substance located?
between dermal collagen and elastic tissue
What is ground substance made of?
glycosaminoglycan
What are the primary cells within the dermis?
Fibroblasts
Does blood supply cross into the epidermis?
No
What are the 3 types of corpuscles?
Meissner’s, Ruffini, and Pacinian
Where are Meissner’s corpuscles most concentrated?
thick hairless skin, (finger pads and lips)
What sort of touch are Meissner’s corpuscles most sensitive to?
Light Touch (+slow vibration)
Where are Ruffini corpuscles most concentrated?
around fingernails
What are Ruffini corpuscles sensitive to?
skin stretch
What do Ruffini corpuscles monitior?
Slippage of objects
Where are Pacinian corpuscles most concentrated?
Dermal papillae of hands and feet
What are Pacinian corpuscles sensitive to?
Deep pressure and vibration (deep touch)
What do Pacinian corpuscles detect?
Surface texture
What do Merkel cells detect?
Light touch
Are dermal and epidermal receptors encapsulated or unencapsulated?
Dermal nerve receptors (Meissner’s / Ruffini / Pancinian corpuscles) are encapsulated while epidermal (Merkel cell) receptors are not
What are the 6 functions of skin?
Physical barrier
Immunological barrier
Thermoregulation
Sensation
Metabolism
Aesthetic appearance
What cells carry out immune surveillance in the dermis?
Tissue‐resident T-cells
Macrophages
Dendritic cells
How are cornified cell envelope and stratum corneum important in the role of skin as a physical barrier?
restrict water and protein loss from skin
How is subcutaneous fat important in the role of skin as a physical barrier?
important role in cushioning trauma
How are melanocytes important in the role of skin as a physical barrier?
protection against UV-induced DNA damage
How does the skin regulate body temperature (thermoregulation)?
Vasodilatation or vasoconstriction in deep or superficial vascular plexuses
→ regulate heat loss
Eccrine sweat glands
→ cooling effect
What are the 6 functions of hair?
Protection against external factors
Sebum
Apocrine sweat
Thermoregulation
Social and sexual interaction
Epithelial and melanocyte stem cells
What are the 2 types of hairs?
Terminal and vellus
Where are terminal hairs located?
scalp, eyebrows and eyelashes
Where are vellus hairs located?
Rest of body (except palms, soles, mucosal regions of lips, and external genitalia)
What ae the 3 stages of the hair cycle?
Anagen (where new hair forms and grows), catagen (regressing phase), telogen (resting phase)
What % of hair is in anagen?
85%
What % of hair is in catagen?
1%
What % of hair is in telogen?
15%
How long does anagen last?
2-6 years
How long does catagen last?
3 weeks
How long does telogen last?
3 months
What happens after the 3 phases of the hair cycle?
Old hair falls out
What 3 things are contained in a pilosebaceous unit?
hair shaft, hair follicle, sebaceous gland
What is the Infundibulum?
Uppermost portion of the hair follicle extending from opening of sebaceous gland to surface of the skin
What is the Isthmus?
Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
Where are eccrine sweat glands located?
Almost everywhere
Where do eccrine sweat glands open to?
directly onto the skin’s surface
Where are apocrine sweat glands located?
in areas with many hair follicles such as the scalp, armpits, groin
Where do apocrine sweat glands open into?
open into the hair follicle
Where does the nail plate emerge from?
proximal nail fold
How much do nails grow a month?
1-3mm
Where does the nail plate detach?
hyponychium
What does the nail matrix produce?
the nail plate
Where does the nail matrix lie?
Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
What is the visible part of the nail matrix called?
Lunula
What are the 5 functions of the nails?
Protection of distal phalanx
Counterpressure effect to pulp - important for walking and tactile sensation
Increase dexterity / manipulation of small objects
Enhance sensory discrimination
Scratching or grooming
