Skin Structure & Function Flashcards
Epidermis tissue type
Stratified squamous epithelium
Dermis tissue type
Connective tissue
Layers of the epidermis
Superficial to deep - Keratin layer Granular layer Prickle cell layer Basal layer (then dermis)
rete ridges
downward projections of the epidermis down into the dermis
Blaschko’s lines
lines of normal cell development in the skin - not seen normally.
Presence indicates a developmental growth pattern of skin problem
What composes 95% of the epidermis
Keratinocytes
Why is there continuous regeneration of the epidermis
Keratinocytes migrate from the basement membrane of the epidermis
How long does the process of keratinocyte migration normally take
around 28 days
How long does the process of keratinocyte migration take in psoriasis
45 days
In what layer of the epidermis can intra-epidermal blistering occur
Prickle cell layer -
lots of desmosomes (connections) that are burst apart by hydrostatic pressure
What layer of the epidermis is the origin of the ‘cornified envelope’
Upper cells of the granular layer - stratum corneum
lose their nuclei and become surrounded by tough envelope of proteins
what are corneocytes
terminally differentiated keratinocytes that are non-nucleated
what common skin complaint affects keratinocytes
Warts - HPV 4+11
why are children more susceptible to warts
cornified envelope hasn’t formed properly
Other epidermal cells apart from keratinocytes
melanocytes
langerhans cells
merkel cells
What are skin appendages
hair follicles
sebaceous glands
sweat glands
what are melanocytes
melanin-producing neural-crest derived cells
pigment-producing dendritic cells
What layer of epidermis are melanocytes found
basal layer
Vitiligo
autoimmune disease with loss of melanocytes
Albinism
genetic partial loss of pigment production
Nelson’s syndrome
Clinical sign for presence of a pituitary tumour - melanin stimulating hormone produced in excess by pituitary
What layer of epidermis are Langerhan’s cells found in
Prickle cell layer (suprabasal)
also dermis and lymph nodes
What are Langerhan’s cells
main skin resident immune cell
antigen-presenting - pick up antigen in skin and circulate to lymph node
Characteristic of Langerhan’s cells
Birbeck granules
What are merkel cells
mechanoreceptors found in skin (mostly palms and soles) responsible for light touch sensation
What layer of epidermis are merkel cells found in
basal layer
what are hair follicles also known as
pilosebaceous unit (adjacent sebaceous gland)
dermal papillae definition
any small elevation in the dermis that indent the inner surface of the epidermis
Label the different parts of the pilosebaceous unit
(be able to do)
phases of growth of hair follicles
Anagen = growing (3-7yr)
Catagen = involuting (3-4wks)
Telogen = resting (shedding) (each day 50-100 <1%)
Label the different parts of the nail unit
(be able to do)
Hyponychium of the nail
secures the free nail edge
Structure of the Dermo-Epidermal junction
From superficial to deep -
Hemidesmosomes - at basal cell layer of epidermis Lamina lucida Lamina densa Sub lamina densa zone (then dermis)
Inherited conditions of the DEJ
Epidermolysis bullosa - mutation of one of the proteins in the DEJ
Acquired conditions of the DEJ
Pemphigus
Pemphigoid
Dermatitis herpetiformis
- autoantibodies to proteins in the DEJ
What are the different components of the dermis
Cells:
fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells
Fibres:
collagen, elastin
Ground substance:
jelly like mass
Blood vessels, lymphatics, nerves
Role of fibroblasts in dermis
Collagen secretion
Role of macrophages in dermis
Antigen presentation
Role of Langerhans cells in dermis
Antigen presentation
Role of mast cells in dermis
Chemical messengers
How do blood vessels in the dermis appear
as horizontal plexuses
role of lymphatic vessels in dermis
continual drainage of plasma proteins, extravsculated cells and excess interstitial fluid
Specialised nerve receptors in the dermis
Pancinian receptors - pressure receptors
(nearer bottom of dermis)
Meissners corpuscles - vibration receptors
(nearer top of dermis)
Different types of skin glands
Sebaceous glands
Apocrine glands
Eccrine glands
What are sebaceous glands
exocrine glands that secrete oily sebum
present on face and chest mostly
hormone sensitive
inactive until puberty
What are apocrine glands
develop as part of pilosebaceous unit (coiled side part on histology)
found mostly in armpits, areola of nipples
androgen dependent sweat glands
What are eccrine glands
common sweat gland
found throughout skin except mucosal surfaces
mostly palms/soles to aid grip
Main metabolic roles of skin
vitamin D metabolism
thyroid hormone metabolism (T4 to T3)
