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Body Logs > L19- The skin > Flashcards

L19- The skin Flashcards

1
Q

What are the 3 layers of the skin? (from outer to inner)

A
  1. Epidermis
  2. Dermis
  3. Hypodermis
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2
Q

a) What is the name of the inner most layer of the skin? (also known as??)
b) Structure
c) Functions

A

a) Hypodermis, also known as sub-cutaneous layer

b) - Mainly adipose tissue (some neurovascular bundles/lymphatics)
- loose connective tissue- fibroblasts/macrophages/fibres

c) - Provides energy store (generate heat)
- insulator for underlying muscle heat generation
- shock absorber- cushions impacts/protection for underlying structures
- connects skin to underlying muscle and bones
- makes hormones e.g. leptin to control eating habits

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3
Q

Thinning of what layer during ageing is responsible for skin wrinkling and hypothermia?

A

Hypodermis

also dermis

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4
Q

a) What is the name of the middle layer of the skin? (also known as??)
b) Structure
c) Functions

A

a) Dermis- also known as corium

b) - 3 layers: (from upper to lower): papillary, reticular and dermal papillae (interdigitating)
- Variable thickness e.g. 0.6 mm on eyelid and 3mm on hands/feet

c) - contains hairs and sweat glands: thermoregulation
- Contains sensory structures- special senses- touch
- gives structure to skin and so body shape

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5
Q

a) What is the name of the outer most layer of the skin?
b) What cells is it mostly made of ?
c) Structure?
d) Functions?

A

a) Epidermis
b) Keratinised stratified squamous epithelium –> keratinocytes

c) - 4 layers of cells in thin skin, 5 layers in thick skin (soles of feet and palms)
- held together (laterally) by adherens junctions
- some terminal nerve endings
- no blood vessels

d) - prevents water loss (absorbs h20)
- prevents entry to bacteria and parasites
- special cells that present pathogens to immune cells
- synthesis of keratin
- prevents underlying tissue loss due to abrasion

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6
Q

What would be the 2 most important functions of the epidermis?

A
  • Prevents entry to bacteria and parasties

- synthesis of keratin

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7
Q

The epidermis has 4 layers to it, 5 in the palms and soles of feet.

What are they? Include cell type and function.

(From outer to inner)

A

OUTER MOST –> INNER MOST

  1. Stratum corneum (horny cell layer):
    - Cell type: squames (dead keratinocytes)
    - thick on palms + soles of feet (prone to injury)
    - continuously shed
    1. Stratum lucidum (transparent layer)*
  • only on palms and soles of feet
  1. Stratum granulosum (granular layer):
    Cell type: Stratified squamous epithelium
    Functions:
    - contains lamellar granules that are filament-associated proteins that assemble keratin fibrils and secrete it
    - contains tonofibrils (made by lamellar bodies): bundles of keratin filaments and keratohyalin granules
  2. Stratum spinosum (spinous layer)
    Cell type: cuboidal epithelium arranged in 3 layers held together by desmosomes
    Functions:
    - producers of lamellar bodies (keratin factories)
    - first time the golgi apparatus appears
  3. Stratum basale (basal cell layer)
    Cell type: tall columnar epithelial cells
    Functions:
    - constantly renew keratinocytes by cell division (as new daughter cells differentiate they move further from epidermis-dermis division)
    - keratinocytes make keratin filaments (tonofilaments)
    - home to melanocytes: produce melanin
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8
Q

Which layer has cells that produce melanin and what are these cells called?

A

The epidermis

melanocytes

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9
Q

What is the normal transit time of a keratinocyte from the basal layer to the stratum corneum?

A

28-40 days

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10
Q

How is psoriasis related to transit time of keratinocytes?

A
  • transit time of keratinocytes reduced, stratum corneum produced in abundance as silvery scales every 2-3 days
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11
Q

What is hyperkeratosis and what causes this disease?

A
  • too much keratin put on surface of skin, ecspecially hands and feet, causes thickening of the outer layer of the skin

Caused by: pressure rubbing (calluses), defence against inflammation, infeection, radiation of sunlight and iritating chemicals

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12
Q

What are the specialised cells of the epidermis and what do they do? (4)

(where in the epidermis are they found?)

A
  1. Keratinocytes: synthesise keratin which contributes to the strength of the epidermis, found in stratum basale
  2. Melanocytes: produce melanin, the main pigment that gives the skin its colour, found in stratum basale
    - the amount of melanocytes not increased in tanned or black skin just the amount of melanin secreted
  3. Langerhans cells: highly specialised capacity to present antigens to T lymphocytes, mediate immune reactions e.g. in allergic dermatitis
    - found in stratum spinosum
  4. Merkel cells: mechanoreceptor cells associated with sensory nerve endings, stratum basale
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13
Q

Textbooks often categorise there being 4 types of skin but these can group together to form 2 types.

a) What are the 2 types?
b) What is the exception to this?

A

a)
1. Hairy + thin skin
2. Non-hairy + thick skin

b) lips, back of the ear, some areas of external genitalia

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14
Q

How does the thickness of the hypodermis differ between a) women and b) men?

A

a) Women have a thick hypodermis in the hips, thigh and buttocks
b) men have a thick hypodermis in the abdomen and shoulders

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15
Q

Compare the structure of thick skin versus thin skin?

A

Thick skin (non hairy)

  • no hair follicles
  • no sebaceous glands
  • no arrector pili muscles
  • pronounced ridges and furrows on surface
  • regular shaped dermal papillae
  • stratum lucidum often seen
  • thicker stratum corneum, thinner dermis
  • increased density of mechanoreceptors

Thin skin (hairy)

  • hair follicles
  • sebaceous glands
  • arrector pili muscles
  • smaller ridges and furrows
  • irregular dermal papillae
  • stratum lucidum absent
  • thinner stratum corneum, thicker dermis
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16
Q

Compare the functions and location of thick skin vs thin skin?

A
  1. Thick skin (non-hairy)

Location: palmar surface of hand, plantar surface of foot and area between fingers and toes

Functions: Prevent tissue loss to abrasion, increased friction between skin and surfaces and increased sensation

  1. Thin skin (hairy)

Location: everywhere else in the body

Functions: all the other functions

17
Q

a) What are skin appendages?

b) What are the different types?

A

a) Skin associated structures that serve a particular function

b) - Hairs
- arrector pili
- sebaceous glands
- sweat glands
- nails

18
Q

What are the 3 types of hair?

A
  1. Lanugo: covers the developing fetus (sometimes seen at birth)
  2. Vellus: this replaces lanugo, it is short, thin light coloured and soft (not connected to sebaceous gland)
  3. Terminal: head (scalp + eyebrows, nasal passages), axillae and external genital region:
    - long, wide, dark coloured and coarse
    - produced by actions of testosterone
19
Q

What are the functions of hair?

A

Thermoregulation:

  • Hair flat when body temp normal or higher
  • Hair erect when body temp lower (arrector pili muscle contracts when stimulated by sympathetic fibres from ANS)
  • acts as barrier to UV rays in scalp

Sexual attraction:

  • hair style
  • apocrine sweat glands secrete oils (pheromones) that attract opp sex + hairs trap these oils

Sensation:
- hair have sensory nerve endings within bulb: air movement, physical interaction, vibrations transmitted to bulb sensed and transmitted to CNS

Protection:

  • eyelashes + nasal hair prevent dust and pathogens
  • eyebrows reduce amt of light and sweat entering eyes
  • axilla hair acts as a conduit to conduct sweat away from body
20
Q

Arrector pili muscle

a) Structure
b) Function

A

a) - consist of smooth muscle fibres attached to papillary region of dermis (origin) and hair bulb (insertion)

b) - Fight or flight response or cold causes involuntary contraction –> goose bumps
- may also induce sebum release from sebaceous gland

21
Q

List the 7 types of mechanoreceptors and what they do

A
  1. End bulbs: thermoreceptor
  2. Free nerve endings: have nocireceptors- register pain
  3. Tactile discs: vertical dimpling of skin, attaches to basal layer keratinocyte and senses touch pressure and texture (merkel in non-hairy skin, meissner in hairy skin)
  4. Meissner corpuscle: tapping and flicker movements detected
  5. Pacinian corpuscle: vibration
  6. Ruffini’s corpuscle: joint movements and tissue stretch
  7. Root hair plexus: vibrations in hair shaft
22
Q

Nails:

a) Location
b) Structure
c) Functions

A

a) Distal surface of phalanges (fingers and toes)
b) Consists solely of alpha keratin and has nail plate, nail matrix and nail bed below it and grooves surrounding it

c) - Protection of distal phalanx and surrounding soft tissues from injuries
- Enhances precise delicate movements of the distal digits through counter pressure exerted on pulp of finger
- enhancing sensitivity of finger tip (even tho no nerve endings)
- as a tool enabling the precision grip e.g. splinter pulling, cutting or scraping

23
Q

What is the growth rate of nails correlated with?

A

Length of phalanx

24
Q

List 8 general and summarised functions of the skin

A
  1. Protection and repair: keratinocytes and UV protection by melanocytes, papillary dermis by fibroblasts (wound healing)
  2. Temp regulation and excretion of waste products: sweat glands secrete urea, NaCl , h20 and co2
  3. Lubrication: sebaceous glands release oil onto surface and acts as water barrier
  4. Storage: white adipose cells provide lipids for energy
  5. Vit D synthesis
  6. Absorption: absorbs h20 and o2
  7. Aesthetics: mode of communication or attraction (tattoos, piercings, hair-stykes)
  8. Sensations: mechanoreceptors (pain, pressure, touch, arousal etc)
25
Q

Outline the process of keratinocyte proliferation and differentiation

A
  1. Keratinocytes proliferate in the basal layer- the basal cells make keratin filaments (tonofilaments)
    - as the cells move away from the basal layer they lose their ability to divide
  2. In the spinous layer lamellar bodies are formed (keratin forming factories)
  3. In the granular layer: Tonofibrils formed (bundles of keratin filaments and keratohyalin granules) made by lamellar bodies
    - apoptosis first seen at this level (become committted to terminal differentiation)
    - tonofibrils are also water barriers

Keratinised cells held together by desmosomes

Body Logs (15 decks)

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