The skin Flashcards
what is the technical term for the skin?
The Integumentary System
what are the 3 layers to the integument?
- epidermis
- dermis
- subcutaneous layer (hypodermis)
what are the 2 layers of the dermis?
- papillary layer
- reticular layer
what is the largest organ of the body?
the skin
what is the surface area of the skin in an adult?
1.5-2 m^2
what are the 2 main layers of the skin?
epidermis and dermis
what makes up the subcutaneous layer?
areolar and adipose tissue
what are the 5 layers to the epidermis? top->bottom
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
describe the stratum corneum
Most superficial layer of epidermis; 20–30 layers of dead, flattened,
anucleate, keratin-filled keratinocytes
describe the stratum lucidum
2–3 layers of anucleate, dead keratinocytes; seen only in thick skin (i.e., palms of hands, soles of feet)
describe the stratum granulosum
3–5 layers of keratinocytes with distinct granules in cytoplasm; keratinization begins in this layer
describe the stratum spinosum
Several layers of keratinocytes attached to neighbors by desmosomes; epidermal dendritic cells present
describe the stratum basale
Deepest, single layer of cuboidal to low columnar keratinocytes in contact with basement membrane; cell division occurs here; also contains melanocytes and tactile cells
describe the papillary layer
Superficial layer of dermis; composed of areolar connective tissue; forms dermal papillae; houses capillaries and tactile receptors
describe the reticular layer
- Deeper layer of dermis;
- composed of dense irregular connective tissue;
- surrounds and supports hair follicles, sebaceous glands and sweat glands, nerves, and blood vessels
what type of tissue is the epidermis?
Stratified keratinised squamous epithelium
true or false:
the epidermis has no blood vessels or nerve endings
true
where do the cells from the epidermis originate from?
- the basal layer (stratum basale)
- Progress and migrate towards the skin surface
what are the depper layers of the epidermis bathed in? why?
- bathed in interstitual fluid
- from the dermis
what happens to the epidermal cells when they reach the skins surface?
- they are flat, thin, non-nucleated
- cytoplasm replaced by keratin
how long does complete replacement of the epidermis take?
~1 month
state 4 things about thick skin
- found on palms of hands and soles of feet
- all 5 epidermal strata
- 0.4-0.6mm thick
- Has sweat glands but no hair follicles or sebaceous glands
state 4 things about thin skin
- found everywhere else
- 4 epidermal strata (excluding stratum lucidum)
- 0.075-0.15mm thick
- Contains sweat glands, hair follicles, sebaceous glands
what determines skin colour?
- Determined predominantly by melanin
- Also by haemoglobin and carotene
- Type and amount of melanin varies, NOT number of melanocytes
what 2 things determine the amount of melanin in the skin?
- genetics
- sun exposure
what is the difference between darker skinned people and lighter skinned?
- Darker skinned people produce more and darker melanin
- and package melanin into more superficial layers
what forms the dermis?
connective tissue:
- collagen
- elastin
what gives the dermis its tensile strength?
Collagen fibres bind water and give dermis its tensile strength
what allows the dermis to stretch and recoil?
elastin fibres
what causes stretch marks/striae?
overstretching/tearing of fibres
what 3 cells are found in the dermis?
- fibroblasts
- macrophages
- mast cells
describe the dermal papillae
Upward projections of dermal layer, interdigitating with epidermal ridges (downward projections of epidermis)
how are blisters formed?
separation of the dermis and epidermis, collection of serous fluid between the layers
what are the 2 functions of the dermal papillae?
- Anchor dermis securely to epidermis
- Allow passage and exchange of nutrients and waste products to lower epidermis
where is the epidermis thicker? why?
- thicker on palms and soles
- subject to greater wear and tear
what creates finger prints?
- Friction ridges formed by meeting of dermal papillae and epidermal ridges
- Where arranged in parallel lines are fingerprints
what injury may cause a gape and delay healing?
An incision perpendicular
to cleavage lines
what are langer lines?
lines of cleavage
– indicate predominant direction of collagen fibres in reticular layer
state 5 things that are found in the reticular layer of the dermis
- Small blood and lymph vessels
- Sensory nerve endings
- Sweat glands and ducts
- Hairs and arrector pili muscles
- Sebaceous glands
what do the arterioles and cappilaries in the dermis supply?
- sweat glands
- hair follicles
- sebaceous glands
the dermis
what are the 4 things that the sensory receptors in the dermis detect?
- touch
- temperature
- pressure
- pain
what corpuscle detects light pressure and low frequency vibration?
Meissner’s corpuscle
what does the Meissner’s corpuscle detect?
light pressure and low frequency vibration
what corpuscle detects deep pressure and high frequency vibration?
Pacinian corpuscle
what does the pacinian corpuscle detect?
deep pressure and high frequency vibration
what detects pain, extreme temperature, chemical irritants?
Free nerve ending (nociceptor)
what do free nerve ending (nociceptor) detect?
pain, extreme temperature, chemical irritants
where is body hair found?
Everywhere except palms and soles, lips and parts of genitalia
what are hair follicles?
downgrowths of epidermal cells into der
what is the papilla? where is it found?
- hair bulb
- found at the base of the follicle
how is hair formed?
- hair is formed by multiplication of cells in the bulb
- As cells are pushed upwards, they die and become keratinised
- Hair above the skin is the shaft, remainder is the root
what determines hair colour?
Colour is genetically determined, dependent on the amount and type of melanin
what are arrector pili?
little bundles of smooth muscle fibres attached to hair follicles
what are nails derived from?
derived from same cells as epidermis and hair
what are nails?
keratin plates
what are the function of nails?
protect the tips of fingers and toes
when do nails grow faster?
when the environmental temperature is higher
where are sweat glands found?
- Widely distributed throughout the skin
- Most numerous in the palms and soles
what forms sweat glands?
formed from epithelial cells
where are the bodies of sweat glands found?
lie coiled in subcutaneous tissue