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BL Skin Structure And Function Flashcards

1
Q

What are the layers of the skin?

A

Epidermis
Dermis
Hypodermis

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2
Q

Structure of the epidermis

A
  • made of epithelial cells - keratinocytes
  • keratinised stratified squamous epithelium
  • thick skin - 5 layers
  • thin skin - 4 layers
  • adherens junctions
  • desmosomes
  • avascular
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3
Q

Function of the epidermis

A

Prevents water loss
Protection against bacteria + parasites
Presents pathogens to immune cells
Prevents underlying tissue loss from abrasion
Keratin synthesis
Temperature regulation
Sensation

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4
Q

Layers of the epidermis

A

Come, Let’s Get Sunburnt

Stratum Corneum - corny/horny later
Stratum Lucidum - only in palms + sole of feet
Stratum Granulosum - granular layer
Stratum Spinosum -spinous layer
Stratum Basale - basal cell layer

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5
Q

Outline the structure of the stratum corneum

A

Made of squames: dead keratinocytes
Thick on palms + soles of feet - prone to injury
Continuously shed

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6
Q

Outline the structure of the stratum granulosum

A

Very darkly stained
Stratified squamous epithelium
Many Golgi apparatus for vesicles
Lamellar granules + keratohyalin granules
Tonofibrils

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7
Q

What are lamellar granules?
Where are they found?

A

Filament associated proteins that assemble keratin fibrils + release it
Stratum granulosum

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8
Q

What are tonofibrils?
Where are they found?

A

Bundles of keratin filaments + keratohyalin granules
Stratum granulosum

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9
Q

Outline the structure of the stratum spinosum

A

Cuboidal epithelium arranged in 3 layers - held together by desmosomes
Producer of lamellar bodies - lipid production
- keratohyalin factories
Keratohyalin granules

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10
Q

Outline the structure of stratum basalt

A

Columnar epithelium
Keratinocytes are constantly dividing by mitosis
Melanocytes

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11
Q

What are do melanocytes release and what stimulates this?

A

Melanin
MSH - melanocyte stimulating hormone

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12
Q

Outline the structure of the dermis

A

Loose connective tissue - upper papillary layer
Dense irregular connective tissue - lower reticular layer
Collagen
Elastin
Contains blood vessels

0.6mm-10mm thick

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13
Q

Functions of the dermis

A
  • thermoregulation - contains hairs and sweat glands
  • touch - contain sensory structures
  • structure + body shape
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14
Q

What causes skin wrinkling?

A

Thinning of the dermis
Less collagen and elastin

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15
Q

Structure of the hypodermis

A

Mainly adipose tissue
Loose connective tissue - fibroblasts, macrophages

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16
Q

Functions of the hypodermis

A
  • provides energy store - generate heat
  • insulator for underlying muscle heat generation
  • shock absorber
  • makes hormones
  • connects skin to underlying muscles + bones
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17
Q

What is the varying thickness of the hypodermis based on?

A

Location
Person - men vs women

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18
Q

Hypodermis thickness in men

A

Thick in abdomen - white adipose - energy storage
Thick in back of shoulders - brown adipose

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19
Q

Hypodermis thickness in women

A

Thick in hips, thigh and buttock

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20
Q

What part of the body has a thick hypodermis in both sexes?

A

Palms of the hand

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21
Q

Function of the skin

A
  • protection and repair
  • temperature regulation + excretion of waste products
  • lubrication
  • storage
  • vitamin D synthesis
  • absorption
  • aesthetics
  • sensations
22
Q

How does the skin provide protection?

A

Epidermis of keratinocytes - abrasion
UV protection by melanocytes

23
Q

Outline vitamin synthesis in the skin

A

1- cholecalciferol produced in the skin
2- converted into 25-hydroxyl cholecalciferol by liver
3- converted into 1,25-hydroxyl cholecalciferol VitD3 - active vitamin by kidneys

24
Q

What is desquamation?

A

Shedding of the outer layer of the skin

25
Describe the process of keratinocyte differentiation
- upwards maturation of basal keratinocytes into cornified cells with the progressive flattening of cells, loss of nuclei + other organelles . - **stranum basale** - keratinocytes are made via cell division - one cell remains + others move up layers. Tonofibrils are synthesised - **stranum spinosum** - where keratohyalin granules + lamellar bodies begin in form - start of cornifying cells + aggregating keratin filaments - **stratum granulosum** - more keratohyalin granules + lamellar bodies produced. Tonofibrils act as water barrier - **stranum corneum** - progressive flattening + lose of organelles to form the corny layer
26
What hormone does the hypodermis produce? What does it do?
Leptin Involved in regulating food intake
27
Where is soft and hard keratin found?
Soft - skin Hard - horns, hair + nails
28
Location of langerhan’s cells
Stratum spinosum
29
What is a merkel cell? What does it look like in H+E staining?
Mechanorecpetor cells associated with sensory nerve endings - surrounded by Schwann cells Schwann cell contains lipids > don’t stain in H+E > pale circle around purple dot
30
Who are at the greatest risk of skin cancer?
People with albinism Don’t produced melanin
31
What are the four types of skin?
Hairy skin + non hairy skin Thin skin + thick skin Hairy skin tends to be thin Non-hairy skin tends to be thick
32
Location of non-hairy/thick skin
Palms of hand Sole of feet Area between fingers and toes
33
Function of non-hairy/thick skin
**Prevents tissue** loss due to abrasion **Increased friction** between skin + surfaces **Increased sensation**
34
Structure of non-hairy/thick skin
No hair No arrector pili muscles No sebaceous glands Thicker startum corneum Thinner dermis Increased density of mechanoreceptors
35
Thick skin vs thin skin in relation to: - hair follicles - sebaceous glands - arrector pili muscles - ridges + furrows - dermal papillae - stranum lucidum
**Thick**: - no hair follicles - no sebaceous glands - no arrector pili muscles - pronounced ridges + furrows - regular shaped dermal papillae - stratum lucidum present **Thin** - presence of hair follicles - presence sebaceous glands - presence of arrector pili muscles - smaller ridges + furrows - irregular dermal papillae - stratum lucidum absent
36
What are skin appendages derived from? Examples
Derived from down growths of epidermal epithelium during 3rd month of fetal development - hairs - arrector pili - sebaceous glands - sweat glands - nails
37
What are the types of hair? Describe them + location
**Lanugo** - covers developing fetus **Vellum** - replaces lanugo - short, thin, light coloured + soft **Terminal** - *scalp, eyebrows, nasal passage, axillae, external genital region* - long, wide, dark coloured, coarse - produced by the actions of testosterone
38
Functions of hair
- **Thermoregulation** - **Sexual attraction** - **Sensation** - **Protection**
39
Explain the hair’s function in thermoregulation
**Piloerection** - when body temp is low **Pilorelaxation** - when body temp is normal or raised Arrector pili muscles contract when stimulated by sympathetic fibres >> piloerection
40
Explain the hair’s function in sexual attraction
Apocrine sweat glands secrete pheromones that attract the opposite sex Hair traps the pheromones
41
Explain the hair’s function in sensation
- Hairs have sensory nerve ending within bulb - Movements sensed by the bulls an transmitted to CNS - Provide sensory awareness
42
Explain the hair’s function in protection
- barrier to UV rays - scalp - eyelashes and nasal hair prevent dust and pathogens - eyebrows reduce the amount of light and sweat entering the eyes - axilla hair conducts sweat away from body
43
Explain the role of arrector pili muscles and how they work
- Consist of smooth muscle fibres attached to papillary region of dermis and hair bulb - Can induce sebum release from sebaceous gland - piloerection + pilorelaxation
44
What are holocrine glands?
Secretions are produced in the cytoplasm Released by rupture of plasma membrane >> destroys the cell Substance secreted
45
Functions of sebaceous glands
**Produce sebum** - lubricate skin/hair - reduce water loss - aid skin flexibility - protect from UV damage - reduce friction damage - facilitate cooling of skin
46
Where are sebaceous glands found?
Mostly in face and scalp Eyelids, penis, labia, nipples, lip
47
List mechanoreceptors and what they detect
- **end bulbs**: *thermoreceptor* - temp. - **free nerve endings**: *nociceptors* - pain - **tactile discs**: touch, pressure + texture - **meissner corpuscle**: tapping + flicker movements - light + touch - **pacinian corpuscle** - vibrations/pressure - **ruffini’s corpuscle** - joint movements + stretch - **root hair plexus** - vibrations in hair shaft
48
Frequencies used for pacinian corpuscle Range Optimum
100 to 1000 Hz Optimum - 450 Hz
49
Frequencies used for meissner’s corpuscle Range Optimum
10 to 50 Hz Optimum 35 Hz
50
Structure of nails
Only made of alpha keratin
51
Functions of nails
- **protection of distal phalanx** - **enhances precise delicate movements** - extra grip - **enhances sensitivity of the fingertip** - **as a tool**
52
What are the epithelium of the layers of epidermis?
- **stratum corneum**: squames (dead keratinocytes with no organelles) - **stratum granulosum**: stratified squamous epithelium - **stratum spinosum**: cuboidal epithelium - **startum basale**: columnar epithelium

Body logistics (20 decks)

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