Skin Structure/Function Flashcards
What are the protective functions of the skin?
protects against:
mechanical impact
pressure
temperature variations
microbes
radiation/chemicals
how does the skin physiologically regulate the body?
body temperature - sweat/hair
peripheral circulation changes
fluid balance - sweat (minor)
vitamin D synthesis
how does the skin provide sensation?
through a nerve cell network that detects and relays changes in the environment (temperature, touch, pain)
describe the characteristics of the stratum corneum
large, flat, plate-like envelopes filled with cross-linked keratin
contains lipids
no nucleus/cytoplasm
describe the characteristics of the stratum granulosum
flattened cells, contains keratohyalin granules
beginning to lose nucleus and cytoplasm
describe the characteristics of the stratum spinosum
polyhedral keratinocytes
rich in desmosomes
describe the characteristics of the stratum basale
cuboidal/low columnar cells
mitotically active, constant regen of other layers
connected to BM by hemidesmosomes
what additional layer does thick skin have?
stratum lucidum
what features does the dermis contain?
CT - collagen type 1 (tensile strength), elastin (allows stretch) and ground substance
fibroblasts
blood supply
what are the 2 dermis layers called?
papillary (upper)
reticular (lower)
describe the function of the dermo-epidermal junction
attachment of epidermis and dermis
aligns epidermal cells
serves as reepithelialisation base in wound healing
barrier function (to/from epidermis)
what are the functions of the subcutis?
energy source
shock absorption
insulation
explain the structures in the papillary dermis allowing skin to perform its sensory function
merkel cells - attaches to PD and acts as mechanoreceptors
meissners corpuscles - mechanoreceptors responsible for touch in PD in hands/feet
what structure in the subcutis allows skin to perform its sensory function?
pactinian corpuscles - detects deep pressure/vibration
explain the function of eccrine glands in skin
temp control glands that excrete sweat
mostly found in palms, soles and axillae
what are apocrine glands and where are they found?
scent glands found in axillae and genitals
what is the function of sebaceous glands and where are they found?
formed from hair follicle
present everywhere except palms and soles
produces sebum
what is the definition of epithelium?
type of tissue that covers body surfaces, lines cavities or forms glands
what type of epithelium is the epidermis?
stratified squamous keratinised epithelium
where are keratinocytes located and what is their function?
location - keratinised stratified squamous epithelium
function - protection/barrier and vitamin D production
where are stem cells found in the epidermis and what is their function?
location - stratum basale
function - self renewal/repopulation of epidermal layers
where are merkel cells located and what is their function?
located - basal layer of epidermis
function - sensation
where are langerhans cells located and what is their function?
located - stratum spinosum and papillary dermis
function - dendritic cell: antigen presentation and phagocytosis
where are melanocytes found and what is their function?
location - basal layer
function - radiaton protection
what can chronic UV exposure in humans lead to?
loss of skin elasticity/fragility
abnormal pigmentation
blood vessel haemorrhage
wrinkles/premature ageing
what is keratins location and function?
location - all epidermal layers
function - structural proteins, intermediate filaments
what is profilaggrin’s location and function?
location - keratohyalin granules
function - converted to filaggrin which fuses keratin filaments into tight bundles
what is involucrin’s location and function?
location - keratohyalin granules
function - forms cell envelope around stratum corneum cells and cross links to loricrin (also in keratohyalin granules)
what are polysaccharides/glycoproteins/lipids location in the skin and what is their function?
location - lamellar granules
function - extrudes into intercellular space and forms the ‘cement’ holding stratum corneum cells together
what is the function of dermal fibroblasts?
collagen/elastin/ECM synthesis
acts as growth factors
what is the function of dermal lymphocytes?
immunosurveillance
what is the function of dermal dendritic cells?
phagocytosis and antigen presentation
what is the function of dermal mast cells?
produces inflammatory mediators (e.g histamine) during degranulation
produces chemotactic factors for eosinophils and neutrophils
what main molecules are present in the dermis and what are their functions?
type 1 collagen - structural fibrous proteins
elastin - elasticity and recoil
proteoglycans/glycosaminoglycans - hydration
what is the definition of a wound?
breakdown in the protective function of the skin
desrcibe the cellular features of a wound
loss of epithelium continuity
possible loss of underlying CT
what is damaged in an erosion wound?
only epidermis
what is damaged in an ulceration wound?
structures deep to epidermis
what is damaged in a partial thickness wound?
epidermis + some dermis
what is damaged in a full thickness wound?
epidermis, dermis and deeper structures
what are the 3 aspects of wound healing?
inflammatory, proliferative, remodelling
explain the process of the inflammation/vascular phase in wound healing
platelets initiate haemostasis/blood clot and initiate the healing cascade
neutrophils/macrophages recruited to fight infection by phagocytosing dead tissue and microbes
explain the process of reepithelialisation in proliferative wound healing
epithelial cells loosen cell-cell adhesions and migrate to wound site, cover the granulation tissue and meet in the middle
once one layer of keratinocytes covers the area, all keratinocytes proliferate
what forms the granulation tissue in proliferative wound healing?
type 3 collagen
what is neurovascularisation in proliferative wound healing?
proliferation and migration of endothelial cells
what physiological changes occur in the remodelling phase of wound healing?
granulation tissue becomes mature scar tissue
collagen organised into thick bundles and cross-linked, forming a mature scar
type 3 collagen becomes type 1
what growth factor is responsible for reepithelialisation?
epidermal growth factor (EGF)
what is the function of platelet-derived growth factor (PDGF)?
matrix formation (increased fibroblast abundance/activity) and remodelling (protease production)
what is the function of vascular endothelial growth factor (VEGF)?
angiogenesis (endothelial cell proliferation/migration)
what signalling molecules are responsible for inflammation in wounds?
interleukin 1 (Il-1), Il-6 and tumour necrosis factor a (TNFa)
what local factors influence wound healing?
infection, foreign body, oxygenation, vascular supply
what systemic factors influence wound healing?
age, disease, alcohol/smoking, immonucompromised conditions, obesity, medications
