Skin Flashcards
What is the integumentary system?
-Skin, sweat glands, sebaceous glands, hair, nails
-Physical barrier between ext & int env
What are the functions of integumentary system?
-Prevent water loss
-Protect from harm & bacteria
-Immunity (Langerhans cells)
-Sensory
-Regulates body temp
-Synthesises vitamin D in sunlight
What are the basic layers of the skin?
-Epidermis
-Epidermal ridge & dermal papillae = junctions
-Dermis
-Hypodermis (fat/adipose tissue) - i.e., subcutaneous tissue
Role of dermal ridges
Holds epidermis & dermis together
Role of epidermal ridges/dermal papillae?
Supplies nutrients & O2 to epidermis
What are the layers within the epidermis superficial to deep?
-Stratum corneum (COME)
-Stratum lucidum (LETS)
-Stratum granulosum (GET)
-Stratum spinosum (SUN)
-Stratum basale (BURNT)
Structure of the stratum corneum (epidermis)?
-Dead cells made of keratinocyte cells (keratin - the cells will desquamate & be replaced by lower down cells regularly)
-No nuclei (anucleated)
-Flat cells
-Prevents water loss
-Protects from friction, microbial invasion
-Cells = terminally differentiated or squames = slowly lost
Role of keratinocyte cells in stratum corneum of epidermis?
Here = dead cells - keratin layer - protection
Structure of the stratum lucidum (epidermis)?
-Eosinophilic
-Thin - only in thick skin - palms of feet, hands
-Colourless/translucent
Structure of stratum granulosum (epidermis)?
-3-5 cells thick
-Flat cells
-Central nuclei
-Most = basophilic –> as have keratohyalin granules (help w/ keratinisation of skin at top)
-Thinner keratinocyte layer
-Keratinocyte layer contains = keratohyaline granules containing filaggrin & other prots binding the tonofibrils
-Granules combine w/ tonofilaments (keratin intermediate filaments) = keratin
-Cells here degenerate -> keratinized scales forms corneum
Structure of stratum spinosum (epidermis)?
-Polyhedral cells
-Contains Langerhans cells (immunity)
-Thickest layer
-Central nuclei
-Contains keratinocyte cells
-Contain bundles of intermediate filaments (tonofibrils) containing keratin tonofilaments
Role of Langerhans cells in stratum spinosum of epidermis?
= APCs - detect foreign/harm causing antigens = take up & presents to B-cells to antibody so will be phagocytosed
-Prevent antigens moving to LNs
-Langerhans cells = type of peripheral DC
—> migrate to LN to present antigens to T cells - to initiate response against foreign antigens
Role of keratinocyte cells in stratum spinosum of epidermis?
Undergo keratinization (differentiation) = to form keratin layer on top
-Migrate upwards
How are the cells of stratum spinosum attached to each other?
By desmosomes at the tips of short projections containing bundled keratin, or tonofibrils.
Structure of stratum basale (epidermis)?
-High rate of mitosis
-Where stem cells are
-All cells originate here (& migrate upwards)
-Cuboidal/columnar cells
-Melanocyte cells found here
-Merkel cells here
Role of Merkel cells in stratum basale of epidermis?
Receptor - detects light sensation touches
-Has nerve attached which will send signal to brain
Role of melanocyte cells in stratum basale of epidermis?
-Makes dark melanin pigment synthesised by melanocytes - moves to keratinocytes
–> protects nuclear DNA from UV damage
How are cells of stratum basale attached to BM & each other?
-BM = by hemidesmosomes & integrins
-Other cells = by desmosomes
What is vitiligo?
-Destruction of melanocytes (melanin producing cells)
-Autoimmune condition
-Symmetrical depigmentation
What does hyperkeratosis mean?
-Thickening of stratum corneum of epidermis
-Orthokeratosis hyperkeratosis = hyperkeratosis w/ no nuclei
What is dermatitis?
-Thicker epidermis (shows parakeratosis - retained nuclei of keratinocytes of corneum)
-Itis = inflammation
-Lymphocytic infiltrate = appear purple (basophilic) - involved in inflammation
-Fluid accumulates
-Blood vs = dilates (w/ inf)
–> caused by fungus
What is Bowen’s disease?
-Cells & nuclei = not uniform shapes
-Full-thickness dysplasia with abnormal mitoses
-High mitosis rate - divide uncontrollably
-Dysplasia = abnormal shaped cells
-Intact BM & dermis - so = carcinoma in situ (localised to epidermis) - can develop to squamous cell carcinoma
-Change in shape of nuclei = pleomorphism
Key feature of squamous cell carcinoma?
Keratin pearls (concentric rings)
Label.
C = Corneum
G = Granulosum
S = Spinosum
DP = Dermal Papillae
B = Basement membrane
D = Dermis
What are the layers of the dermis?
-Papillary dermis (top)
-Reticular dermis (bottom)
What is within the dermis (x5)?
-Nerves
-Lymphatics
-Hair follicles
-Glands
-Capillaries
What are the dermal glands x3?
-Merocrine/Eccrine sweat glands
-Apocrine sweat glands
-Holocrine sebaceous glands (= sebum/oil)
How do merocrine glands secrete sweat?
-Sweat within vesicles - cell retained (remains intact)
-Cell secretes vesicle via exocytosis
-Thin sweat secretion
= most sweat glands of body (except axilla & pubic regions)
(made of many cells)
How do apocrine glands secrete sweat?
-Part of cell removed with the sweat vesicles
-Cell replenishes
-Still = exocytosis
-Thicker sweat secretion
-Only in axilla & pubic regions only active in puberty
(made of many cells)
How do holocrine glands secrete sebum/oil?
-Whole cell removed with the sebum vesicles
-Thickest secretion (thicker than sweat)
-Still = exocytosis
-Often for sebaceous glands
(made of many cells)
What are all of the types of sensory receptors in the skin x5?
-Merkel disk
-Krause & bulb
-Ruffini ending
-Meissner’s corpuscle
-Pacinian corpuscle
What does Meissner’s corpuscle detect, where is it & what is its structure?
-Light sensation touches
-In papillary dermis
-Axon is spiralled covered w/ Schwann cells
-Corpuscle has CT covering
-Most in fingertips & lips
What does the Pacinian corpuscle detect, where is it & what is its structure?
-Vibrations & heavy pressure
-In dermis & hypodermis
-Stright axon covered w/ Schwann cells
-Lots of CT layers around corpuscle
What are the 3 components of the pilosebaceous unit?
-Hair follicles (where hair grows) = hair (made of keratin)
-Arrector pili muscle (in papillary dermis layer)
-Sebaceous glands
How does erection of hair on skin occur?
-Smooth muscle = Arector pili muscle
-So erects via sympathetic innervation
–> fear/cold = goosebumps
x3 features/facts about sebaceous glands?
-Stratified cuboidal glandular epithelium
-Central nuclei
-Arrector pili = smooth muscle - spindle shaped
What is acne?
-Lots of sebum secreted = sebaceaous glands enlarged
-Corneum - doesn’t desquamate - sebum stuck (accumulates)
–> creates medium for bacteria = Cuti bacterium acnes
-Inflammatory response to protect from bacteria - lots of neutrophils
What is vitamin D conversion due to sunlight?
7-Dehydrocholesterol = naturally in skin - converted into D3 by sunlight (UV) - or get D3 in diet
D3 converted to 25-Hydroxy-D3 by liver - then converted to 1,25-Dihydroxy-D3 (active vitamin D form) - helps Ca2+ absorption (need to absorb Ca2+)
How do wounds heal?
-Cut = wound
-Cells come to stop bleeding - clot
-WBCs - neutrophils & macrophages come to protect from infection (as is open wound)
-Fibroblasts help heal skin (component of CT)
-Angiogenesis occurs = blood vs formation - provide nutrients to wound - help heal
-Ep will regenerate - scar tissue (fibrosis) below
