S3: The Structure and Function of Skin Flashcards Preview

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Flashcards in S3: The Structure and Function of Skin Deck (47)
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1
Q

What does integuent/integuementary system refer to?

A

It refers to the skin, hair and nails.

It is the largest and heaviest organ of the body.

2
Q

How does the skin act as a barrier?

A

It prevents:

  • Dehydratation. This is achieved by the epidermis and lipids stop it from evaporating.
  • Infection where the epidermis is a impervious barrier and also an immune system (langerhan cells)
  • Injury/Abrasion - all layer contribute. The epidermis is strong and rapid healing, thick where friction occurs. The dermis has collagen so is tough and the hypodermis acts as a shock cushion.
  • Solar radiation where the stratum corneum in the epidermis contains melanin pigment.
3
Q

How does the skin thermoregulate and insulate?

A

The hypodermis acts as an insulator and it regulates temperature via thermoreceptors.
It is also a homeostatic organ, regulating body temperature via sweat production and blood flow, e.g. gym and snow. It is not a fluid homeostatic mechanism, as we do not adjust our fluid volume by controlling sweat production, but we do lose water through skin.

4
Q

Functions of the skin

A
  • Barrier
    -Thermoregulation
  • Insulator
  • Sensation via nerves and receptors
  • Repair - Epidermis normally proliferates and dermis-fibroblasts fills gaps in skin with new collagen that
    epidermis can attach to.
  • Vitamin D production - the skin is also a secretory organ and the epidermis is the site of production
5
Q

What are the three layers of the skin?

A
  1. Epidermis
  2. Dermis
  3. Hypodermis
6
Q

What does the skin contain?

A
  • Glands
  • Hairs
  • Sense Organs
7
Q

Briefly describe the three layers of the skin

A

Skin is composed of the thin epidermis on the top which is the part continuously growing and being shed.
The dermis is much looser connective on which the epidermis sits.
The subcutic/hypodermis is the inner fatty layer

8
Q

Describe the histology of the layers of the skin

A

The cells in the epidermis are very close together giving a very intense whereas the tissue in the dermis is much looser with cells further apart so it stains less intensely. The dermis layer is thicker than epidermis in the tissue section.
Fat doesn’t stain at all so it appears as the white round bits.

9
Q

Give examples of epidermis being thin and thick in different parts of the body

A

Thick epidermis e.g. heel

Thin epidermis e.g. abdomen

10
Q

Name the four main layers of the epidermis

A
  1. Stratum basale
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum corenum
11
Q

Describe the stratum basale

A

It is the layer that is on the bottom, at the base of the epidermis and top of dermis.
Stratum basale is a single layer containing stem cells that divide and push upwards. As they move up, they differentiate and they get more glattened until they are shed from the outer surface.

12
Q

Describe the stratum spinosum

A

This is the layer above the stratum basale.
The layer looks spiny because it contains lots of desmosomes. These are connections between cells that hold the cytoskeletons of cells together.
They are strong cellular adhesions holding the epidermis together making the skin into a good barrier.

13
Q

Describe the stratum granulosum

A

There are two things in these granular cells:

  1. Keratohyalin granules (precursor to keratin).
  2. Lamellar bodies that are full of lipids.

Both these things differentiate to form the top layer (stratum corneum).

14
Q

Describe stratum corneum

A

This is the top layer. They are squamous cells that have lost their nuclei and are cornified (full of ‘horny’ keratin from keratohyalin granules) so they are touch and resistant to injury.
Non polar lipids (waterproof) are between the cells and they come from lamellar bodies.

15
Q

Why is the skin oily and soft but nails and hair hard?

A

Most skin is oily and soft, this is because the cells contain soft keratin. However other parts such as nails and hair contain hard keratin.

16
Q

Does the epidermis have blood supply?

A

No

17
Q

What is the stratum lucideum?

A

It is the clear layer containing immature keratin that is halfway between stratum granulosum and stratum corneum.

18
Q

What are the 3 other epidermal cell types in the skin (that aren’t part of the skin)?

A
  1. Melanocytes (pigment)
  2. Langerhans cells (defence)
  3. Merkel cells (sensation)
19
Q

Describe role and mechanism of melanocytes in the skin

A

Melanocytes allow pigmentation in the skin. Melanocytes release melanin which is taken up by surrounding cells - the rate at which it is processed determines colour of skin.
They do this by synthesisng melanosomes (pigment granules) and transfers them to basal keratinocytes though long dendrites.
- Melanin pigment is mostly in basal epidermis
- Colour of skin depends on presence of eumelanin

20
Q

What is vitiligo?

A

It is the loss of melanocytes, causing change in pigmentation.

21
Q

Describe role and mechanism of Langerhans cells

A

Langerhans cells are immune cells that act as antigen presenting cells. They are also dendritic cells forming a network.

22
Q

What are Merkel cells?

A

They are sensory cells in the skin associated with nerve endings.

23
Q

Describe vitamin D production

A
  • Vitamin D3 is made in the epidermis
  • It occurs mostly in stratum basale but also in stratum spinosum
  • It requires UV light and more UV in darker skin due to melanin barrier
  • It is converted to active form in liver and kidney : 1,25 dihydroxyvitamin D3
24
Q

What is vitamin D deficiency called?

A

Vitamin D is commonly deficient in the UK. In adults it is called osteomalacia and in children it is called rickets.

25
Q

What is the structure of the dermis?

A

it is dense irregular connective tissue.

Dense = it is full of collagen fibres.
Irregular= fibres run in all directions and are not parallel.
It also contains elastin.

26
Q

What is the function of the dermis?

A

It provides tensile strength from collagen and protects against abrasion and impact.
It also contains elastin which is a protein complex that provides elasticity.
The dermis also carries blood and nerve supple for the epidermis and is rich in blood vessels.

27
Q

What is the dermal-epidermal border and where on our body is it noticible?

A

It is the border between the dermis and epidermis.

It is often wavy to resist shear forces (rubbing sideways) and it is noticeable on our hands and feet.

28
Q

What are rete ridges?

A

The epidermis has them and they are opposite the dermal paillae going into the dermis.

29
Q

What are dermal paillae?

A

Finger like projections the dermis has which allows the epidermis to access nutrients from blood vessels running in the dermis.

30
Q

What cell in the dermis makes and maintains collagen?

A

Fibroblasts.

Collagen is much of the volume of the dermis.

31
Q

Describe the dermis in an Elastin van Gieson stain

A

Collagen fibres are red and elastic fibres are black.

32
Q

What can cause wrinkles?

A

UV light on skin can damage the elastic fibres in the dermis resulting in an loss of elasticity leading to wrinkles.

33
Q

Why does our skin go wrinkly if we stay in the bath for ages?

A

Water can only go as far as the stratum granulosum layer (it’s oily) but the stratum corneum can absorb a lot of water. So as the cornified layer swells the granular layer stays the same so the stratum corneum has to ripple.

34
Q

What is the hypodermis also called?

A
  • The fascia

- Subcutis

35
Q

What is the cutis?

A

Epidermis + dermis = cutis

36
Q

Describe the structure of the hypodermis

A

It is composed of fat, containing glands, hair follicles, nerves and blood vessels. It is often the thickest layer of skin and the thickness varies with age, body site, nutrition etc.

37
Q

What is the thickest layer of skin?

A

The hypodermis

38
Q

What is the function of the hypodermis?

A

The function is to provide insulation, cushioning and energy storage.

39
Q

Where do you put a hypodermic syringe?

A

The hypodermis is where you put a hypodermic syringe for a subcutaneous injection.

40
Q

Describe hair follicles in the skin

A

Each hair follicle has an arrector pili muscle which controls the angle of the hair. Hair follicles can be a site of acne when follicle becomes blocked and infected.
Hair also keeps the head warm.

41
Q

Describe the two types of sweat glands

A
  1. Eccrine (all over the body). They are normal sweat glands and they provide watery secretion n to skin surface to cool the body by evaporation.
  2. Apocrine (smelly in armpit and groin) and they secrete into hair follicles. It is oily fluid in humans, function unclear but source of body odour after bacterial action. Only found after pubert and less in asians.
42
Q

Describe sebaceous glands

A

These are holocrine glands. They secrete oily sebum (lanolin) into the hair follicle. They are a conditioner for the hair and skin preventing dryness and flaking.

43
Q

What are goose pimples?

A

Goosepimples allow hair to be much thicker by the piloerector muscles pulling on them, they are sort of redundant in humans.

44
Q

How do antiperspirant/deodorants work?

A

Antiperspirant chemicals clog apocrine sweat glands and also kill bacteria that give the bad smell, the deodorant gives a nice smell

45
Q

Describe structure of nails

A

The nail is also an appendage, it is made of hard keratin.
Nail bed is the skin that the nail rests on. The crevice underneath the nail is called hyponychium - has some medical important as it can get infected.

46
Q

Name three ways a gland/cell can secrete something

A

Merocrine -> Release via exocytosis (these are eccrine glands)
Apocrine -> Pinch bits off, give bits away
Holocrine -> Blow up

47
Q

Describe the sense organs in the skin

A

Meissner’s corpuscle (light touch) found in the skin of a fingertip (epidermis).
Pacinian Corpuscle (pressure) in hypodermis.
Thermoreceptor senses heat or cold.
Nociceptor senses pain and are free nerve endings, black.