Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Body Logistics > 10.1 - Skin Structure > Flashcards

10.1 - Skin Structure Flashcards

1
Q

what is the skin also known as

A

the integumentary system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 3 main layers of the skin

A

epidermis
* outer layer (most superficial)
* approx 3mm
* derived from ectoderm
* has 4 layers called keratinocytes

dermis
* regular, dense, connective tissue + collagen + elastin
* find many structures here, eg sweat glands
* important for flexibility and strength in the ksin
* 0.6mm - 1cm
* derived from ectoderm

hypodermis
* below dermis
* aka ‘superficial fascia’
* majority of adipose tissue is found here
* highly vascularised
* derived from mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the cutis

A

epidermis and dermis
☞ derived from ectoderm

hypodermis is not in this, as it is derived from mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

the hypodermis

features (functions on different cards)

A
  • innermost layer of skin
  • aka superficial fascia
  • derived from mesoderm (therefore not considered part of skin)
  • majority of adipose tissue found here: storing energy
  • thickness varies in different regions + different individuals → depends on amount of fat
  • varies considerably between m+f (different card)
  • highly vascularised (some neurovascular bundles and lymphatics)
  • loose connective tissue - fibroblasts, macrophages and fibres
  • thinning of this layer during aging is responsible for wrinkling and hypothermia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

functions of hypodermis

(features on diff card)

A
  • energy store - generates heat
  • insulator for underlying muscle heat generation
  • shock absorber - cushions impact, and acts as protection for underlying structures
  • connects skin to underlying muscle and bones
  • hormones - eg produces leptin to control eating habits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

differences in thickness of hypodermis between males and females

A

men
* thickest in abdomen and shoulders
* abdomen - white adipose tissue for energy storage
* shoulders - brown adipose tissue

women
* thickest in hips, thighs and buttocks
* this is where white adipose tissue is found

☞ for both, relatively thick on the palms of the hands and feet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

features of the dermis

A
  • between the epidermis and hypodermis
  • aka corium
  • with epidermis collectively = cutis
  • variable thickness 0.6-3.0 mm
  • contains hair and sweat glands, and blood vessels and nerves

Three layers
☞ papillary dermis: upper, paler part. Less collagen and elastin.
☞ dermal papillae: interdigitating parts of papillary dermis
☞ reticular dermis: lower, darker, part. Dense collagen and elastin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the functions of the dermis

A
  • contains hair and sweat glands for thermoregulation
  • contains sensory structures - special senses - touch
  • gives structure to skin and therefore body shape
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

features of the epidermis

A
  • outermost layer made of epithelial cells (keratinocytes)
  • four layers of cells (thin skin) or five (thick skin) ☞ on different card
  • held together laterally by adherens junctions
  • held together basal-apical by desmosomes
  • some terminal nerve endings
  • no blood vessels - all nutrients come through dermis
  • rete ridges sometimes present on keratin layer (forms fingerprints)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

functions fo the epidermis

A
  • prevents water loss (layer of lipid)
  • prevents entry to bacteria and parasites
  • special cells that present pathogens to immune cells
  • synthesis of keratin (keratin layer on surface that can be lost)
  • prevents underlying tissue loss due to abrasion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the four/five layers of the epidermis

A

stratum corneum/corny/horny layer
* outermost layer made of squames
* thick on palms and soles of feet (prone to injury)
* continously shed

stratum lucidium/clear layer
* only found on palms and soles of feet

stratum granulosum/granular layer
* stratified squamous epithelium
* very darkly stained
* lamellar granules (filament associated proteins that assemble keratin fibrils and release it)
* tonofibrils (bundles of keratin filaments and keratohyalin granules made by lamellar bodies)
* golgi apparatus appears increased in this layer

stratum spinosum/spinous/prickle cell
* cuboidal epithelium in 3 layers held together by desmosomes
* producers of lamellar bodies (keratohyalin factories and lipid production)

stratum basale/basal cell layer
* tall columnar epithelial
* constantly renew keratinocytes by cell division
* as daughter cells differentiate they move away from epidermis-dermis junction, become stratum spinosum
* these make keratin filaments (tonofilaments) - lose ability to divide
* melanocytes (produce melanin) found here

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

keratinocytes

A
  • synthesise keratins (fibrous protiens)
  • keratins contribute to strength of epidermis
  • keratins are main constituents of hair and nail
  • normal transit time of a keratinocyte from basal layer to stratum corneum in the epidermis is 28-40 days
  • this transit time is massively reduced in psoriasis
  • hyperkeratosis: too much keratin being put on the surface of the skin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

keratin synthesis pathway

A
  • starts at basal cells, already making keratin
  • here, they are called tonofilaments (intermediate keratin filaments)
  • there are different types of keratin made in different cells in the body, and not all cells can
  • as the intermediate keratin filaments divide, they push cells upward ☞ daughter cell become spinous cell and then granular cell
  • its at this point, lamellar bodies are produced (contain a lot of lipid) and keratin forming factories (where tonofilaments coming together to form tonofibrils)
  • tonofibrils are released and act as water barrier between dead and live skin cells
  • as cells are pushed further up, they make keratohyalin granules (can see dark on microscope)
  • cells undergo apoptosis (lose all organelles)
  • cells pushed through water barrier mechanically
  • cells lose ability to maintain pH so become more acidic
  • cells lose water and pushed down, and keratin in cells becomes more compacted (cells get smaller)
  • filaggrin proteins from desmosomes (holding these cells together) are broken down by pH
  • this allows upper (dead) cells ‘squames’ to fall off (desquamation of keratin layer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

melanocytes

A
  • found in the epidermis
  • produces melanin
  • combination of different types determines their hair and skin colour
  • the melanin is moved into sacs called melanosomes
  • melanosomes are transferred to neighbouring keratinocytes by pigment donation (phagocytosis of tips of melanocyte
  • melanin protects nucleus against UV light, therefore preventing DNA damage
  • these are not increased in number in dark skin, just produces more melanosomes
  • histology: look similar to langerhan’s cells, but melanocytes are seen at regular intervals on basal layer of epidermis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

langerhans cell

A
  • most commonly found in stratum spinosum of epidermis
  • come from the bone marrow and are part of immune response
  • difficult to see histologically without special stains but looks a lot like melanocytes (but different layer)
  • highly specialised capacity to present antigens to T-lymphocytes to mediate immune reactions (eg contact dermatitis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are merkel cells

A
  • mechanoreceptor cells associated with sensory nerve endings
  • difficult to see histologically without special stains
  • have a ‘halo’ due to schwann cells surrounding the nerve cells - the schwann cells are lipid so not stained
17
Q

two main types of skin

with exceptions

A

hairy skin tends to be thin skin

non-hairy tends to be thick skin

exceptions to the rules include the lips, back of pinna, some areas of external genitalia

18
Q

what are the features and functions of non-hairy (thick) skin

A

location
* palmar surface of hand
* plantar surface of foot
* area between fingers and toes (webs)

structure
same as rest of body except….
* no hair, no arrector pili muscles, no sebaceous glands
* thicker strata corneum
* thinner dermis
* increased density of mechanoreceptors

functions
* prevents tissue loss to abrasion
* increased friction between skin and surfaces
* increased sensation

18
Q

what are the features and functions of non-hairy (thick) skin

A

location
* palmar surface of hand
* plantar surface of foot
* area between fingers and toes (webs)

structure
same as rest of body except….
* no hair, no arrector pili muscles, no sebaceous glands
* thicker strata corneum
* thinner dermis
* increased density of mechanoreceptors

functions
* prevents tissue loss to abrasion
* increased friction between skin and surfaces
* increased sensation

19
Q

thick (non-hairy) vs thin (hairy) skin

A

thick/non hairy
* no hair follicles
* no sebaceous glands
* no arrector pili muscles
* pronounced ridges and furrows on surface
* regular shaped dermal papillae
* stratum lucidium often visible

thin/hairy
* presence of hair follicles
* sebaceous glands present
* arrector pili muscles present
* smaller riges and furrows
* irregular dermal papulae
* stratum lucidium absent

20
Q

what are skin appendages and examples

A

skin associated structures that serve a particular function
* hairs
* arrector pili
* sebaceous glands
* sweat glands
* nails

all developed from ‘down growths’ of epidermal epithelium during 3rd month of fetal development

21
Q

what are the three types of hair

A

lanugo
* covers developing fetus
* sometimes seen at birth
* people with albanism don’t have this
* thin and long

vellus
* replaces lanugo
* short, thin, light coloured and soft
* not connected to sebeceous gland

terminal
* present on head (scalp and eyebrows, nasal passage), axillae, external genital region
* long, wide, dark coloured and coarse
* produced by the actions of testosterone

22
Q

what are the funtions of hair

A

thermoregulation
* hair lays flat when body temp is within normal range or elevated
* hair stands erect when low temp (due to arrector pili muscles contracting, stimulated by sympathetic fibres from autonomic NS)
* also acts as partial barrier to UV light

sexual attraction
* apocrine glands secrete oils (pheromones)
* these attract opposite sex

sensation
* hairs have sensory nerve endings within bulb
* detect air movement, physical interactions
* vibrations transmitted to bulb, which is transmitted to CNS
* provides sensory awareness eg bug landing on hair

protection
* eyelashes and nasal hair prevent dust and pathogens from entering body
* eyebrows reduce the amount of light and sweat entering the eyes
* axilla hair acts as conduit to conduct sweat away from body

23
Q

arrector pili muscle

A
  • consist of smooth muscle fibres attached to papillary region of dermis (origin) and hair bulb (insertion)
  • fight or flight response, or the cold causes involuntary contraction
  • ‘goose bumps’
  • muscle contracts when stimulated by sympathetic fibres from the autonomic NS
  • squeezes sebacous gland at same time, releasing sebum release
24
Q

sebaceous glands

and functions

A
  • holocrine glands that produce sebum (oily/waxy substance)
  • found mostly in the face and scalp
  • also eyelids, penis, labia, nipples and lip
  • part of the pilosebaceous unit

functions
* lubricate skin and hair
* reduce water loss from skin and hair
* aid skin flexibility
* protect skin and hair from too much moisture + UV damage
* reduce epidermal damage from friction
* facilitate the cooling down of skin in hot conditions (in conjuctions with sweat glands)

25
Q

sweat glands in the skin

A
  • can be apocrine or eccrine
  • apocrine glands secrete a thick, odorous fluid into hair follicles
  • eccrine sweat glands secrete a water fluid onto the surface of the skin
  • the sweat glands are found
  • both are fomed as downgrowths of the epidermis
26
Q

mechanoreceptors of the skin

A
  • end bulbs thermoreceptor
  • free nerve endings have nocicreceptors to register pain
  • tactile discs attaches to basal layer keratinocyte. senses touch, pressure and texture
    ☞ merkel in non-hairy
    ☞ meissner in hairy
  • meissner corpuscle tapping and flicker movements
  • pacinian corpuscle for vibration and pressure, particularly high frequency
  • ruffinis corpuscle for join movements and tissue stretch
  • root hair plexus vibrations in hair shaft
27
Q

what are the frequencies detected by meissners corpuscle and pacinian corpuscle

A

pacinian corpuscle
100 → 1000 Hz
but optimum is about 450 Hz

meissners corpuscle
10 → 50 Hz
but optimum is about 35 Hz

28
Q

nails

A

location
on the distal surfaces of phalanges (fingers and toes)

structure
* mainly α keratin
* made up of nail plate, matrix, and nail bed below it, and the grooves surrounding it

functions
* protection of distal phalanx and surrounding soft tissues
* enhances precise delicate movements
* enhances sensitivity of fingertip
* ‘extended precision grip’ eg picking up needle

note that growth of nails is correlated with length of phalanx

29
Q

functions of skin

summary

A
  • protection and repair eg uv protection by melanocytes, repair of epidermis by keratinocytes, wound healing of papillary dermis by fibroblasts
  • temperature regulation and excretion of waste products eg via sweat glands, excretion of urea, NaCl, water and CO2
  • lubrication sebaceous glands release oil onto surface and act as water barrier
  • storage white adipose tissue provide lipids for energy
  • vit D synthesis covered in MEH
  • absorbtion small amounts of water and O@ and some drugs
  • aesthetics as a mode of communication eg tattoos
  • sensation specialised strucutres (mechanoreceptors) for pressure, touch, vibrations etc

note: first few mm of skin can respire via gas exchange of O2 and CO2

Body Logistics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions