Skin Flashcards
stratum … is above
dermis
what are the four primary tissues in skin as an organ
Epithelium
Connective Tissue
Muscle
Nerve
Epidermal cells are termed
keratinocytes
skin facts
- Largest organ in the body
- Has its own nerve and blood supply
- One of the first noticeable organs in patients
skin and pathological conditions
it has its own pathological conditions:
- Sunburn
- Eczema
- Acne
- Psoriasis
- Melanoma
skin provides external evidence of
underlying systemic conditions:
- Liver disease
- Systemic sclerosis
- Mitral stenosis
- Urticaria
epidermis function
prevents water loss by evaporation
dermis function
- reduces risk of external injury
- maintains epidermis by its blood flow
- permits body cooling
cooling of skin happens by
sweat glands and alterations in surface blood flow.
loss of heat from dilated blood vessels
skin functions
- Immune surveillance
- UV protection
- Energy storage
- Sensory information
structure of skin
Epidermis:
- epithelium
- Forms boundary between internal and external
environments
Dermis:
- connective tissue
- gives structural strengthhypodermis is
Adipose (fatty) CT layer beneath skin = subcutaneous tissue
Anchors skin to underlying structures - (not strictly part of skin)
Epidermis outer layer of skin consists of
of 5 strata = layers.
Epithelial tissue is a
- Stratified squamous keratinising epithelium
- Ectodermal origin
epidermal cell types include
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Function of Merkel cells
touch receptors
Epidermis outer layer of skin consists of
of 5 strata = layers.
- 5 layers formed by maturing keratinocytes
- Continuum from basement membrane to skin surface
- Layers not sharply defined
Function of Melanocytes
pigment formation
Function of Langerhans cells
immune surveillance
What is structure and function of Stratum basale (germinativum)?
- Tall columnar cells interspersed with melanocytes and
Merkel cells - Cells bound to basement membrane by
hemidesmosomes - Irregular interface with dermis - dermal papillae
- Continuous cell proliferation - are stem cells
(undifferentiated)
hemidesmosomes
Bind Stratum basale (germinativum) to basement membrane
What is structure and function of Stratum spinosum
Spinous layer
Created post-mortem:
- Cells shrink but desmosome junctions “create” spines
Little structural evidence of activity
Preparative layer for keratinisationWhat is structure and function of Stratum granulosum
Presence of granules defines the layer
Granules of keratohyalin (possible precursors of keratin)
keratohyalin
possible precursors of keratin
What is structure and function of (Stratum lucidum) Stratum corneum
- Stratum lucidum difficult to distinguish from str. corneum
- Conversion of keratohyalin to keratin
- Lots disulphide linkages give strength
- Stratum corneum has “no” organelles
- Desmosomes bind cells
- 15-30 day turnover
Keratinisation
Organic process whereby keratin is deposited in cells and these become horny as in dead skin, nails, hair
keratinisation process (bottom layer to top)
- stratum basal - stem cell division
- incorporation of keratin
- cell flattening
- loss of nuclei and protoplasm
- stratum corneum - dead cells are sloughed off
psoriasis is
an autoimmune disorder affecting keratinisation
psoriasis is
an autoimmune disorder affecting keratinisation
Palms of hands & soles of foot
thick skin
Abdominal skin
thin skin
what layer of stratum varies most in epidermal thickness
Stratum corneum
dermis also varies
Dermis layers
Papillary layer
- Loose connective tissue
- Cellular
Reticular layer
- Dense irregular connective tissue
- Fibrouswhat layer of dermis is larger
reticular layer and it is also below the papillary layer
Papillary layer has
- Loose connective tissue
- Irregular interface with epidermis - “papillae”
- Cellular eg macrophages
- Protective against pathogens
- Blood vessels
- Nerve endings
why are blood vessels needed in the papillary layer of dermis
- Thermoregulation
- Nutrition
why are nerve endings needed in the papillary layer of dermis
sense organs
Reticular layer has
Dense irregular connective tissue
Collagen bundles in three planes
Elastic fibres
Loss of elasticity is normal in old age
Reticular layer has
- Dense irregular connective tissue
- Collagen bundles in three planes
- Elastic fibres
- Loss of elasticity is normal in old age
Waterproofing and skin
- Function of epidermis
- Keratin in cells “waterproof”
- Intercellular spaces filled with lipid cement
- Keratin originates as lamellated granules in str. granulosum
Skin colour is determined by
- Blood
- Carotene
- Melanin
- Melanocytes
- In str. germinativum
- “Injects” melanin
- Mainly found on “Sun” side of nuclei
Melanin
Protects against UV
Hair and skin
- Thermoregulatory but not in humans
- Responsive to cold but not effective
- Practical use in skin repair
- Derived from epithelial layer
Origin of hair follicles
- From epidermis in utero
- Downgrowth of epithelial cells
- Invasion of knot of blood vessels
- Growth of hair
- Continuity with layers of epidermis
Hair follicle
Hair + sheath(s)
Arrector pili muscles in hair
- Attached to follicle root and base epidermis
- Follicle at angle
- Hair straightens when muscle contracts
Sebaceous glands
- Between follicle and arrector pili muscle
- Secretes sebum
- Function uncertain
strong plate of hard keratin, called
nailornail plate,
nailornail plate which grows out from
nail bed
the nail bed, is a specialised form of
skin epithelium, and has the same four layers of the epidermis of skin, with the nail plate being analogous to thestratum corneumlayer.
lunula is the
white bit on nail above cuticle
eponychium is
cuticle
hyponychium
under end of nail - nail bed
Skin glands
Sebaceous
- Hair follicles
- Sebum
Apocrine sweat glands
- Axilla
- Protein rich - B.O.!
Eccrine
- SweatEccrine sweat glands
- Simple tubular glands
- Located in dermis
- Coiled secretory portion
- Coiled and straight duct in dermis
- Spiral channel in epidermis
- Watery secretion
- Thermoregulatory
Thermoregulation occurs through
Sweat glands
Blood vessel dilation
- Absorption
- Radiation
Hair
- Polar bears not humansSkin – sense organ
Numerous sensory nerve endings:
Meissner’s corpuscles
- light touch - fingertips
Paccinian corpuscles -
- vibration & pressure
Pain receptors
ThermoreceptorsSkin – sense organ
Numerous sensory nerve endings:
Meissner’s corpuscles
- light touch - fingertips
Paccinian corpuscles -
- vibration & pressure
Pain receptors
Thermoreceptorsskin repair after damage
blood clot
scab
granulation tissue
scar
Melanocytes are found in
Basal layer of Epidermis
Q. structure is found in the dermis of the skin
Sebaceous glands
