Skin:Structure and function

Question 1

Define integument

Answer 1

The integument system refers to the skin, hair and nails as well as the glands

Question 2

what is the largest and heaviest organ of the body?

Answer 2

The skin

Question 3

What are the 5 main functions of the skin?

Answer 3

1)Barrier= protection against dehydration, infection, injury/abrasion and solar radiation
2)Thermoregulation= maintain body’s correct temp
3)Sensation(feeling)
4)Repair itself (more damage done to the skin than any other organ)
5)Vitamin d production (enzymes in the skin activated by UV rays from the sun)

Question 4

what are the 3 layers of the skin? name them.

Answer 4

1)Epidermis (outer epithelial layer)
2)Dermis (middle connective tissue/ collagen layer)
3)Hypodermis (inner fatty layer and can be the thickest of the 3 layers)

Question 5

How many individual layers does the epidermis have?

Answer 5

4

Question 6

Name the 4 layers of the epidermis (outer epithelial layer)

Answer 6

1) Basal layer (innermost layer of the epidermis)
2)Stratum Spinosum
3)Stratum Granulosum
4)Stratum Corneum (outermost layer of the epidermis)

Question 7

Describe the innermost layer of the epidermis (the basal layer)/ the first layer

Answer 7

1) Contains stem cells (basal cells)that can constantly divide to form new cells to replace the squamous cells that wear off on the skins surface
2)These daughter cells move up in the epidermis (towards outside?), differentiating and flattening as they go to eventually becoming squamous cells
3)Is the innermost layer of the epidermis, sits next to the dermis (connective middle layer of the skin)

Question 8

Within how many days are the cells shed from the outer surface of the skin/

Answer 8

20-50 days

Question 9

Describe the Stratum Spinosum layer (the second layer of the epidermis)

Answer 9

1)The “Spiny layer”
2)These cells within this layer don’t differentiate anymore rather they move upwards and attach cells to each other as they have spines (desmosomes) sticking out of each other
3)This ensures the skin is coherent and tight
4)The cells within this layer have desmosomes (junctions)=spines and strong bonds holding the epidermis together

Question 10

Describe the Stratum Granulosum layer of the epidermis (a.ka Granular layer)

Answer 10

1)Consists of 1-4 layers of cells containing prominent granules of “Keratohyalin” (precursor for the protein keratin).
2)The keratohyalin functions to cross-link keratin to form a tight barrier (epidermis)
3)There are also lamellar bodies that differentiate to form the corneum cells

Question 11

Describe the Stratum corneum (outermost layer/thickest layer)

Answer 11

1)outermost protective layer of the epidermis- layers of dead cells, reduced to flattened scales, or squamous filled with densely packed keratin.
2)contains Keratocytes=tough protein that helps resist friction
2)non-polar lipids (waterproof) come from lamellar bodies that are formed from the granulosa cells
3)Squamous cells which have lost their nuclei- are cornfield full of keratin

Question 12

What stain can be used to look at the thick epidermis?

Answer 12

H&E (hematoxylin and eosin stain)

Question 13

what is the main component of horns, hair, nails, hooves and claws?

Answer 13

Keratin

Question 14

Name 4 important epidermal cells and give a very brief (one sentence) description of what they do.

Answer 14

1)Keratinocytes-
2)Melanocytes- produce pigment
3)Langerhan cells- in defence
4)Merkel cells-for sensations

Question 15

What is the function of melanocytes in the epidermis?

Answer 15

1)Synthesise melanosomes (pigment granules) and transfers them to basal keratinocytes through long dendrites (melanin transfers to keratinocytes as they retain pigment to provide the skin and hair with colour)

Question 16

which region of the skin is the melanin pigment

Answer 16

Basal layer- so the dendrites of the melanocytes go towards the basal layer (the innermost layer/to the keratinocytes)

Question 17

what happens once the melanosomes get transferred to the kertincodytes?

Answer 17

1)Keratinocytes arrange melanin pigment in a cap distal to the nucleus (sunny side)
2)Especially in basal layer (stem cells)
3)the melanin acts as UV protection

Question 18

Can melanocytes be detected under the microscope normally? and what colour are they stained?

Answer 18

1)No
2)Pale

Question 19

What is the function of Merkel cells?

Answer 19

Specialised cells in the skin that are important for proper neural encoding of light touch stimuli

Question 20

what colour do Merkel cells also appear as in the basal layer?

Answer 20

pale- makes hard to differentiate between them and melanocytes

Question 21

What is the function of Langerhan cells? and what type of cell are they? what colour do they appear under H&E stain?

Answer 21

1)Mainly function in the immune system and they form antigen-presenting cells (APC’s), like macrophages
2)They are dendritic cells, forming a network
3)Under h&e stain they appear pale- small, pale cells in non-basal layer of epidermis
4)Hard to see with h&e only

Question 22

in what cells is vitamin D3 (precursor to vitamin d) made from? and which layers of the skin is it made?

Answer 22

1)Basal cells/ basal layer
2)Stratum Spinosum in the epidermis

Question 23

What is the precursor of vitamin D?

Answer 23

Vitamin D3

Question 24

What does the formation of vitamin D require?

Answer 24

1)Requires uv light (more required in darker skin due to melanin barrier to make the same amount of vit d )

Question 25

Vitamin D3 which was made in the epidermis is then converted into the active form of Vitamin D. What is its name?

Answer 25

1,25 dihydroxyvitamin D3

Question 26

Describe the dermis briefly and what does it consist of? and what are their functions? (5)

Answer 26

1)Consists of irregular connective tissue
2)It is dense= is full of collagen fibres- provides tensile strength when pulled, providing protection against abrasion and impact
3)Irregular= fibres run in all directions (not parallel)
4)Elastin- provides elasticity
5)Carries blood vessels and nerve supply for epidermis- there is no blood supply in epidermis so dermis has all these

Question 27

Describe the dermal-epidermal border

Answer 27

wavy, to resist shear forces (rubbing sideways)

Question 28

At the dermal-epidermal border what is the structure of the epidermis and the dermis?

Answer 28

1)Epidermis= rete ridges
2)Dermis= finger-like dermal papillae

Question 29

what can you see after staining the dermis with H&E ?

Answer 29

1)Collagen (appear as pink striations)
2)Fibroblasts (make and maintain the collagen, made of the cells of the extracellular matrix)
3)Small blood vessels

Question 30

What can you see after using Elastic van Gieson stain on the dermis? and what colour does it stain these features?

Answer 30

1)Elastic fibres= black
2Collagen fibres= red

Question 31

What does uv light do to the elastic fibres and what affect does this have on the skin?

Answer 31

It damages them so they lose their elasticity so you get wrinkles

Question 32

The hypodermic is which layer of the skin?

Answer 32

The third layer of the skin

Question 33

Describe the hypodermis

Answer 33

1)The inner fatty layer of skin
2)composed of fat
3)contains glands, hair follicles, nerves and blood vessels
4)often the thickest layer of the skin

Question 34

what is the function of the hypodermis?

Answer 34

provides insulation, cushioning and energy storage

Question 35

Name the 3 sweat glands

Answer 35

1)Sebaceous glands
2)Eccrine sweat glands
3)Apocrine sweat glands

Question 36

what is the function of the Sebaceous sweat gland?

Answer 36

Secrete oily sebum (lanolin) into hair follicle- acts as a conditioner for hair and skin, prevents dryness and flaking.

Question 37

What is the function of the Eccrine sweat glands?

Answer 37

Normal sweat glands that produce watery secretions on the skins surface to cool the body via evaporation, enabling thermoregulation

Question 38

What is the function of Apocrine sweat glands?

Answer 38

secrete oily fluid humans, in hair. The function is unclear but provides body odour after bacterial action.

Question 39

where are Apocrine sweat glands found?

Answer 39

armpits and anogenital region- produces odour only after puberty

Question 40

What is the function of the pili muscles?

Answer 40

raise the hair and can be useful with extra insulation

Question 41

what cell are nails made from?

Answer 41

Keratinocytes

Question 42

what layer do nails grow out from?

Answer 42

the basal layer of the nail from the epidermis under the nail as there is little space underneath the nail that can get infected easily, which is called the hyponchyium.

Question 43

What are the 4 sensory cells in the skin?

Answer 43

1)Thermoreceptors
2)Meissner’s corpuscle
3)Nociceptor
4)Pacinian corpuscle

Question 44

What do thermoreceptors do?

Answer 44

sense the heat or cold and determine how we react

Question 45

what do Meissner’s corpuscle do? and in what other cell In the skin can they be found and for what reason?

Answer 45

Sense touch. They can also be found in Merkel cells in the basal epidermis to sense light touch. The Meissner’s stretches up to the epidermis (individual cells)and the Merkel cells are found in the basal epithelium.

Question 46

what do Nociceptors do?

Answer 46

Sense pain and these are free nerve endings that are present in the epidermis and dermis

Question 47

what does the pacinian corpuscle do?

Answer 47

Senses pressure applied to the skin. Only present in hypodermis, so senses touch signals and doesn’t respond to light touch, but only a a lot of pressure.