L19- Skin Flashcards
three main layers of the skin
epidermis
dermis
hypodermis
layers of the epidermis from outer layer inwards
Cats Gather Suspciously Boldly
- stratum corneum
- stratum granulosum
- st. spinosum
- st. basale
what structures are found in the dermis
hair follicles
arrector pili muscle
sweat glands
sebaceous gland
what type of tissue is the dermis
irregular dense connective tissue
thickness of hypodermis varies in
ifferent regions of the body and can vary considerably between different people
Thickness plays an important role in distinguishing between males and females
hypodermis in men
hypodermis is thickest in the abdomen and shoulders
hypodermis in women
thickest in the hips, thighs, and buttocks
hypodermis is the
lowest layer of the skin
hypodermis also known as
subcutaneous layer
structure of hypodermis
- Mainly contains adipose tissue
• Loose connective tissue – fibroblasts/ macrophages/fibres
function of hypodermis
- energy store- generates heat
- insulator for udnelryign muscl eheat gen
- shock absorber
- conencts skin to underlying muscle and bone
- makes hormones
dermis located
between epidermis and hypodermis
structure of dermis
Three layers
• Papillary - upper
- Reticular - lower
- Dermal papillae – interdigitating
dermis shows…
vairbale thickness
0.6 mm on eyelid; 3 mm on hands/feet
function of dermis
• Contains hairs and sweat glands - thermoregulation • Contains sensory structures – special senses - touch • Gives structure to skin and so body shape
epidermis location
Outermost layer made of epithelial cells (keratinocytes)
structure of epidermis
- Four layers of cells (thin skin)
- Five layers (thick skin)
- Held together (laterally) by adherens junctions • Some terminal nerve endings
- NO blood vessels
function of epdiermis
- Prevents water loss
- Prevents entry to bacteria and parasites
- Special cells that present pathogens to immune cells • Synthesis of keratin
- Prevents underlying tissue loss due to abrasion
stratum corneum
Outermost layer made of squames (dead keratinocytes)
stratum corenum on paalms and soles of feet
thickest- prone to injury- continously shed
strautum lucidum is
transparent
where is stratum lucidum found
palms and soles
stratum granulosum
- stratified squamous epithelium
- lamellar granules
- tonofibrils
lamellar granules
filament-associated proteins that assemble keratin fibrils and secrete it
tonofibrils
bundles of keratin filaments and keratohyalin granules- made by lamellar bodies
stratum spinosum
3 layers of cubodial epithelium (held together by desmosomes)
- producers of lamellar bodies
- first time golgi apparatus appears
lamellar bodies
keratin factories
stratum basale
Tall columnar epithelial cells
Constantly renew keratinocytes by cell division
As daughter cells differentiate they move away from the epidermis-dermis junction
These make keratin filaments (tonofilaments) They lose their ability to divide
Also home to the melanocytes – produce melanin
ketatinocytes synthesise
keratins that cotnribute to the strength of the epidermis
(keratin- main constituents of hair and nail, and animal horns)
normla transit tiem of keratinocytes from basale to stratum conreum
28-40 days
in psoriasis
transit time is reduced, such that stratum corneum is
produced in abundance as silvery scales every 2-3 days
hyperkeratosis
too much keratin put on the surface of skin (especially on the hands and feet)
main cell found in epidermis
keratinocyte
other cells in epidermis
melanocytes
langerhans
merkel cells
how many melanocytes in epidermis
1:8 of basal layer of epidermis
melanocytes function
produce melanin, the main pigment that gives the skin its
colour
langerhans function
highly specialised capacity to present antigens to
T lymphocytes mediate immune reactions e.g. in allergic contact dermatiti
merkel cells
mechanoreceptor cells associated with sensory nerve
endings.
merkel cells acoount for approx ……. cells in the epidermis
6-10%
four main types of skin
- hairy 2. non-hairy 3. Thin 4. Thick
hairy skin tends to be
thin skin
non hairy skin tends to be
thick skin
expection to the hairy/non-hairy/thin/ thick skin rule
the lips, back of the ear, some areas of the external genitalia
location of nonhairy (thick) skin
- Palmar surface of hand
- Plantar surface of the foot
- Area between fingers and toes (webs)
structure of non hairy thick skin
NO hair, arrector pili muscles, no sebaceous glands • Thicker strata corneum
• Thinner dermis
• Increased density of mechanoreceptors
function of non- hairy thick skin
- Prevent tissue loss due to abrasion
- Increased friction between skin and surfaces • Increased sensation
skin can be classified based on its reaction to ultrabioloit radiation
differences between thick (non-hairy) and thin (hairy skin)
thick skin has deep
Rete ridges and extended dermal papillae
thin (non-hairy) skin has less
keratin (stratum corneum narrower) and fewer dermal papillae
skin appendages
skin associated sturctures that serve a particular function
name some skin appendages
hairs
arrector pili
sebaceous glands
sweat glands
nails
how many types of ahirs
3
name the 3 types of hair
- langugo
- vellus
- terminal
lanugo
covers the developing fetus (sometimes seen at birth)
vellus
replaces lanugo
• Short,thin,lightcolouredandsoft(not
connected to sebaceous gland)
terminal
head (scalp and eyebrows, nasal passage), axillae, external genital region
• Long, wide, dark coloured and coarse
how is terminal hair produced
• Produced by the actions of testosterone
hair function (4)
thermoregulation
sexual attraction
sensation
protection
hair lays flat when
body temperature is within normal range or elevated
hair stands erect when
body temperature is lower than normal range
how do hairs stand erect
Arrector pili muscle contracts when stimulated by sympathetic nervous system
hair and sexual attraction
- Hair style can be alluring!
- Apocrine sweat glands secrete oils (pheromones) that attract the opposite sex
- Hairs trap these oils and accentuate their pungency
hair and sensation
Hairs have sensory nerve endings within the bulb:
Air movement, physical interaction, vibrations transmitted to the bulb sensed and
hair and protection
- Eyelashes and nasal hair prevent dust and pathogens from entering the body
- Eyebrows reduce the amount of light and sweat from entering the eyes
arrector pili muscle consist of
smooth muscle fibres attached to papillary region of the dermis (origin) and hair bulb (insertion)
arrector pili muscle may also induce
sebum release from sebaceous gland
name 7 mechanoreceptors in the skin
end bulb
free nerve endings
tactile discs
meissner corpuscle
pacinina corpusle
rufinnis corpuslce
root hair plexus
end bulbs
thermoreceptors
free nerve endings
have nociceptors- register pain
tactile disc
senses touch, pressure and texture (Merkel in non-hairy skin); Meissner in hairy skin)
meissner corpuscle
tapping and flicker movements detected
pacinian corpuscle
vibration
ruffinis corpuscle
joint movements and tissue stretch
root hair plexus
vibrations in the hair shaft
location of nails
distal surfaces of phalanges (fingers and toes)
structure of nails
Consists solely of alpha keratin
gross structure of nail
