Download 2015 Week5/2 NURS1004 The Integument

2015 Week5/2 NURS1004 The Integument
Parts I & II
Martini et al. 10th ed. Ch5 & p.539-542 Martini 9th
ed Ch5 & p498-501. OR International ed. Ch 5 &
p.561-563
The skin, hair, nails, glands and several
specialised receptors make up the integumentary
system.
Functions of the skin:
1. Body temperature regulation
2. Protection (against abrasion, water loss,
bacteria, UVRadiation)
3. Perception of stimuli
4. Excretion
5. Synthesis of vitamin D (calcitriol)
6. Immunity
7. (social function !)
Structure of the skin
About 7% of body weight, from 1.5 to 4.0 mm
thick.
Epidermis (outer layer) composed of epithelial
cells, and a dead layer.
Dermis (inner layer) composed of fibrous
connective tissue and exocrine glands
[Hypodermis (or superficial fascia) composed of
adipose (& some areolar connective) tissue. Not
part of skin, stores fat, anchors skin to muscle,
allows skin to slide over muscle]
1. Epidermal cells (4 distinct types)
1. Keratinocytes. Tightly connected to each other
(by desmosomes), produce keratin (a fibrous
protein).
2. Melanocytes. Have numerous branching
processes that touch all keratinocytes in the
basal layer. Produce melanin, (a pigment
which protects against UV) that is transferred
to nearby keratinocytes.
3. Dendrocytes (langerhans’ cells & granstein
cells). Interact with lymphocytes (T cells) to
assist in the immune response. Are
macrophages.
4. Merkel cells. Associated with a sensory nerve
ending (called Merkel disc) for fine touch &
pressure.
Epidermis is NOT VASCULARISED ! Nutrients reach
epidermal cells by diffusion
Strata (layers) of the epidermis
1. Stratum germinativum/basale. Deepest layer,
attached to dermis, single cell thick, youngest
rapidly dividing keratinocytes. New cells push
up the older ones above. 10%-25% are
melanocytes. Form epidermal ridges.
2. Stratum spinosum. 7 to 10 cells thick. Cells
contain keratin filaments that span cells, attach
to desmosomes & so hold cells together. Blisters
(from repeated rubbing) are fluid-filled pockets
in stratum spinosum caused by disruption of
junctions between cells – layers of skin separate.
3. Stratum granulosum. 3 to 5 cells thick. Contain
granules which aggregate keratin & contain
waterproofing glycolipid*. Cells flatten, nuclei &
organelles disintegrate. (*glycolipids are lipids that
contain carbohydrates, usually simple sugars like glucose)
4. [Stratum lucidum. (only present in thick skin –
palms, soles) a few rows of clear, dead,
flattened keratinocytes.]
5. Stratum corneum. Most superficial layer, 15 to
30 cells thick - up to ¾ of thickness of epidermis.
Dead, flat, filled with keratin. Protects body
against heat, light, chemicals, bacteria,
abrasion. Cholesterol & Glycolipid between cells
waterproofs this layer. – burns victims lose much
water because skin is lost.
2. Dermis
Contains hair follicles, oil & sweat glands, nerve
fibres, blood and lymph vessels.
Strong flexible connective tissue containing
collagen, elastin and reticular fibres. (Dermis of
animals can be tanned to make leather.)
Reticular dermal layer (deep)
80% of thickness of dermis. Contain Pacinian
corpuscles sensitive to deep pressure.
Interlacing collagen fibres arranged in parallel
bundles, (lines of cleavage) give skin strength &
resilience.
Elastin fibres provide the stretch/recoil properties
of skin.
Flexure lines (at joints).
Mammary glands, specialized sweat gland that
secrete milk.
Papillary dermal layer (superficial)
Contain folds and ridges called papillae that push up
into epidermal layer - fingerprints
Papillae contain capillary loop or light touch
receptors – Meissner’s corpuscles.
When capillaries dilated, blood comes close to skin
surface, so energy may be radiated from body.
Sensory receptors in skin
Glands of the dermis
Sebaceous (oil) glands found all over body (except
palms & soles). Secrete sebum into a hair follicle,
keeps skin & hair from drying out. Contains
triglycerides, cholesterol, proteins, electrolytes &
cell fragments.
Sebum is bactericidal.
Blocked ducts – whiteheads, blackheads
Sudiferous (sweat) glands
Eccrine (merocrine) sweat glands, coiled tube in
dermis discharging through duct to pore on skin.
Sweat is hypotonic filtrate of blood. It contains
99% water, Na+Cl-, vit.C, antibodies, urea, uric
acid, ammonia, lactic acid, K+ (pH = 4-6.8).
Under control of sympathetic division of
autonomic NS.
Sweat makes it difficult for non-normal flora to
adhere to skin. Contains dermicidin – an antibiotic.
Evaporation of water molecules (sweat) requires
energy which is drawn from the skin – this leaves
the skin cooler. Body needs to be hydrated to
produce sweat (otherwise  heatstroke).
Apocrine sweat glands in axillary, nipple and
anogenital areas.
Function after puberty.
Ducts empty sweat + fatty substances & proteins
into hair follicles.
Ceruminous glands in ear canal secrete cerumin
(ear wax).
Tactile receptors
Merkel discs: detect fine touch
Meissner’s corpuscles: for fine touch
Pacinian (lamellated) corpuscles: for deep
pressure
Ruffini corpuscles: for pressure and distortion in
skin
Root hair plexus: to detect movement/distortion
of hair follicle
Free nerve endings between epidermal cells (with
small receptive fields) for touch & pressure
Thermoreceptors
Heat free nerve endings: detect heat
Cold free nerve endings: detect cold
Nociceptors for pain: free nerve endings with
large receptive fields (3 types: extremes of temp,
mechanical damage, dissolved chemicals – strong
stimuli excite all 3 !  “burning sensation” excited
by many stimuli)
About 100 sweat glands, 15 oil glands, 230 sensory
receptors per cm2 of skin.
Hair, consists of keratinised cells, protective
function. Arrector pilli muscle stands hair up when
cold (goosebumps).
Nails, modified epidermis consisting of keratin,
useful for scratching, picking things up. Rich bed of
capillaries underlie nails (in dermis).
Burns
1st degree: only epidermis is damaged (sunburn).
Heals in 2-3 days
2nd degree: injures epidermis & upper dermis,
blisters appear (partial thickness burns). Skin
regenerates (1-2 wks) with little or no scarring.
3rd degree: full thickness burns, involve whole
thickness of skin. Nerve endings destroyed.
Extensive burns cannot heal themselves. Skin
grafting required to avoid fluid loss & infection.
If > 10% of skin area is burnt, critical.
If > 20% of skin area burnt, life threatening.
Ageing of skin
Newborn skin is thin. During infancy & childhood
skin thickens & subcutaneous fat deposited. During
adolescence skin & hair become oilier, acne may
appear. After 30 years skin begins to show effects of
“environmental assault”. With old age rate of
epidermal cell replacement slows, skin thins, glands
secrete less. Elastin fibres clump, degenerate,
collagen fibres become fewer & stiffer, hypodermal
fat layer diminishes  wrinkling. Number of active
hair follicles diminishes  hair thinning.
Drug administration
Topical: patted or wiped onto skin, absorbed
through skin & act locally (eg corticosteroids)
Transdermal absorbed through skin, acts
systemically (eg nicotine patch, HRT, nitroglycerine)
Intradermal: injections of < 1 cm3 into dermis. (eg
allergy testing, tuberculin testing)
Subcutaneous: (up to 2ml) injected into
subcutaneous fat (hypodermis) layer (eg heparin,
insulin)
Lipid-soluble substances (eg steroids) can
penetrate skin because glycolipids between cells
of stratum corneum present no barrier.
Vitamin D = calcitriol – required for uptake of
Ca++ from gut
In Skin: UV radiation causes “modified cholesterol
molecules” (=provitamin D3) to be converted to
“vitamin D precursor”.
In Liver: enzymes modify this precursor (add a
hydroxyl group)
In Kidneys: “modified precursor” used to produce
(add a 2nd hydroxyl group) and release calcitriol
(vit D3) upon being signalled by PTH (hormone).
Vit D3 is actually a hormone & skin an endocrine
organ.
M.Caon, 2013
Didy Button 2014
(Additional info)
Human beta defensin 2 is a natural antimicrobial peptide produced by keratinocytes when injured.
Part of skin’s natural defense mechanism (against atopic dermatitis, psoriasis).
Actinic keratoses (solar keratoses = sun spots)
reported in 40% of Australian pop! Can progress
to squamous cell carcinoma. Treatment = cryotherapy with liquid nitrogen or CO2 slush, surgical
removal, or topical therapy with fluorouracil cream.
Non-melanoma skin cancer is the most common type of skin cancer. This type of skin cancer is more
common in men, with almost double the incidence compared to women. Over 434,000 people are
treated for one or more non-melanoma skin cancers in Australia each year. In 2011, 543 people died
from non-melanoma skin cancers.
1. Superficial basal cell carcinoma
2. Nodular basal cell carcinoma
surgically removed with scarring
3. Squamous cell carcinoma
Sunburn causes 95% of melanomas, the most deadly form of skin cancer.
In 2009, more than 11,500 people in Australia were diagnosed with melanoma and in 2011, 1,544
people died due to melanoma. The five-year relative survival rate for melanoma is 90% for Australian
men and 94% for Australian women.
More than 2000 Australians died from skin cancer in 2011.
Majority cured by surgery. Patients with stage IV disease have poorer prognosis with 46% not
surviving longer than 12months from diagnosis http://www.cancer.org.au/about-cancer/types-ofcancer/skin-cancer.html#jump_5 accessed 11/1/14.