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PHYS - MSS & SKIN > 5. STRUCTURE & FUNCTION OF SKIN > Flashcards

5. STRUCTURE & FUNCTION OF SKIN Flashcards

1
Q

Define integument

A
  • Integument is a collective term for the hair, skin & nails
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2
Q

What are the three layers of skin?

A
  1. EPIDERMIS -thin, outermost layer
  2. DERMIS - nerves, blood vessels
  3. HYPODERMIS - fats & connective tissue
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3
Q

What are the 5 functions of skin?

A
  1. BARRIER against:
    - dehydration - epidermis ahs keratin which holds water, making skin waterproof
    - infection - epidermis is an impervious barrier & also contains Langerhans cells
    - injury/abrasion - all layers
    - solar radiation - stratum corneum & melanin
  2. THERMOREGULATION - Dermis has thermoreceptors & hypodermis provides insulation
  3. SENSATION
  4. REPAIR - Normal proliferation of cells in the epidermis, fibroblasts of the epidermis produce collagen which fill the gaps
  5. VITAMIN D3 PRODUCTION - epidermis is involved in converting 7-dehydrocholesterol -> Vitamin D3 in sunlight
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4
Q

What are the properties of the epidermis?

A
  • The epidermis is the outermost layer of the skin, it’s the most superficial
  • Produces Vitamin D3
  • Gives the skin it’s colour
  • Waterproof
    Infection & abrasion protection
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5
Q

What are the 4 layers of the epidermis?

A
  1. BASAL LAYER (Stratum basale)
  2. SPINY LAYER (Stratum spinosum)
  3. GRANULAR LAYER (Stratum granulosum)
  4. CORNIFIED LAYER (Stratum corneum)
    - Sometimes, there’s another layer in between the granular layer and the cornified layer known as the STRATUM LUCIDEUM only found in the palms or soles of the feet
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6
Q

Describe the basal layer of the epidermis

A
  • The basal layer of the epidermis is the deepest, innermost layer which is attached to the dermis.
  • The basal layer contains stem cell populations which are precursors for keratinocytes, these cells are continuously proliferating & undergoing mitosis
  • The cells move up through the epidermis, distally away from the basal layer towards the cornified layer where it can be shed off, taking around 20-50 days
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7
Q

Describe the spiny layer of the epidermis?

A
  • The spiny layer contains keratinocytes
  • These keratinocytes have desmosomes which are junctions between the cell. The desmosomes appear as spines
  • The spiny structures hold the cell of the epidermis together
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8
Q

Describe the granular layer of the epidermis

A
  • The granular layer of the epidermis contains 1-4 layers of granules containing KERATOHYALINE, which is the precursor for keratin
  • The granular layer also contains LAMELLAR BODIES which contain lipids
  • The cells of the granular layer undergo differentiation to from cells of the cornified layer. The cells lose their nuclei & become flattened
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9
Q

Describe the cornified layer of the epidermis

A
  • The outermost layer of the skin & epidermis is the cornified layer.
  • The cells have no nuclei & are flattened
  • These cells undergo the process of keratinisation
  • The cells then contain keratin which makes the skin tough & resistant to injury
  • The non-polar lipids from the lamellar bodies are also located in between the cells of the cornified layer, which makes the skin waterproof
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10
Q

Give examples of three other cells found in the epidermis

A
  1. LANGERHANS CELLS (Defense)
  2. MELANOCYTES (Pigment)
  3. MERKEL CELLS (Sensation)
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11
Q

What do melanocytes do?

A
  • Melanocytes produce melanosomes which contain the pigment melanin
  • These melanosomes are transferred to basal keratinocytes via long dendrites
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12
Q

How are melanocytes involved in UV protection?

A
  • Once the melanosomes are transferred to the basal keratinocytes
  • The keratinocytes will arrange the melanosomes in a cap around the nucleus, preventing the DNA from damage
  • Seen as pale cells
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13
Q

What are langerhans cells & what do they do?

A
  • Langerhans cells are the resident immune cells of the epidermis
  • Langerhans cells seek & deal with invading microbes. They are antigen presenting cells (APCs) so they act as macrophages
  • Seen as small pale cells
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14
Q

How is Vitamin D3 produced by the skin?

A
  • Vitamin D3 is produced in the epidermis, mainly in the BASAL LAYER & SPINY LAYER (stratum basale & spinosum)
  • UV light is needed to produce Vitamin D3 and a greater proportion is needed in dark skinned individuals
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15
Q

**What are the properties of the dermis?

A
  • The dermis is located beneath the epidermis
  • It contains blood vessels, nerves, skin glands, sensory receptors.
  • The dermis is responsible for the tensile strength & elasticity of the skin
  • The dermis is made up of layers of irregular & dense connective tissue characterised by an interconnected mesh of elastin & collagen
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16
Q

What are the principal cells of the dermis?

A
  • The principal cells of the dermis are fibroblasts

- Fibroblasts are involved in producing elastin & collagen

17
Q

What’s the function of the dermis?

A
  • produce collagen - providing tensile strength when pulled, protection against impact or abrasion
  • produce elastin which is a protein complex providing elasticity
  • Dermis also has a rich blood supply & sensory receptors
18
Q

What are the two layers of the dermis?

A
  1. THIN DERMAL PAPILLAE LAYER (deepest)

2. DEEPER RETICULAR LAYER (superficial)

19
Q

What is the dermal-epidermal border?

A
  • The dermal-epidermal border is the border between the epidermis & the dermis
  • It’s often wavy to resist shear force from sideways rubbing
  • It’s more apparent in the thick skin of the hands
20
Q

What are the components of the dermal-epidermal border?

A
  1. DERMAL PAPILLAE - Finger-like protrusions of the dermis into the epidermis
  2. RETE RIDGES - Extensions of the epidermis into the dermis
21
Q

What is the hypodermis?

A
  • The hypodermis is the deepest layer of skin, it is the fascia or the subcutia
22
Q

What are the properties of the hypodermis?

A

The hypodermis is made up of well vascularized, loose areolar connective tissue & adipose tissue
- Hypodermis consists of fat containing blood vessels, hair follicles, glands & nerves & is the area for subcutaneous injections

23
Q

What’s the function of the hypodermis?

A
  1. Mode of fat storage
  2. Provides cushioning & insulation
  3. Energy storage
24
Q

What are the three components of a hair strand?

A
  1. HAIR BULB
  2. HAIR ROOT
  3. HAIR SHAFT
    - The hair matrix is located in the hair bulb
    - The hair strand sits within the hair follicle which is a pouch like structure
25
Q

What are the two cell types found in the bulb of a hair follicle & what do they do?

A
  1. FOLLICULAR KERATINOCYTES - found at the bulb of the hair & produce hard keratin for hair. The follicular keratinocytes flatten out & stack on top of each other to form the shaft & root
    - These follicular keratinocytes can only replicate a certain number of times, after the follicle stop growing & the hair falls out leading to baldness
26
Q

What are eccrine sweat glands & what do they do?

A
  • Eccrine sweat glands are normal sweat glands that secrete a watery liquid onto the SKIN SURFACE
  • The sweat then evaporates helping to cool the body down
  • Found in the hypodermis
27
Q

What are apocrine sweat glands & what do they do?

A
  • APOCRINE SWEAT GLANDs are located in the armpit & the ano-genital region. They secrete an oily fluid INTO THE HAIR FOLLICLE
  • These sweat glans are only present after. Once bacteria acts on these secretions, it produces an odour
  • Found in the hypdermis
28
Q

What do sebaceous glands do?

A
  • SEBACEOUS GLANDS secrete sebum (lanolin), which acts as a conditioner for hair & skin to prevent dryness & flaking
  • Sebaceous glands are only present after puberty
29
Q

What are the nail folds & the eponychium?

A
  • The nail grows from a proximal to distal direction, away from the nail folds towards the eponychium
  • The NAIL FOLDS is where the skin seals off the edges of the nail
  • The EPONYCHIUM is the proximal skin fold which gives rise to the cuticle
30
Q

What’s the cuticle & the nail matrix?

A
  • The CUTICLE is the semi-circular layer of dead skin keratinocytes which surround the area where the nail enters the skin, it prevents the entry of pathogens
  • The NAIL MATRIX is where the nail plate originates, it is the hard part of the nail that is visible including the free edge that hangs over. The nail matrix contains modified keratinocytes which undergo keratinisation
31
Q

Describe keratinization of the nail matrix

A
  • The nail matrix contains modified keratinocytes which undergo keratinisation
  • The youngest keratinocytes will be in the nail matrix with oldest being in the nail plate
  • In hair cells, the keratinocytes are known as follicular keratinocytes
32
Q

What are the two types of nerve endings?

A
  1. FREE NERVE ENDINGS
  2. ENCAPSULATED NERVE ENDINGS
    - Most sensory receptors are in the dermis but Merkel’s discs are in the basal layer of the epidermis

PHYS - MSS & SKIN (6 decks)

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