Introduction to Skin

Question 1

What are the three main layers of skin?

Answer 1

Epidermis, dermis and hypodermis (fat layer)

Question 2

What is keratin?

Answer 2

Keratin is an intermediate filament that is most abundant in the stratum corneum (top layer), hair and nails.

Question 3

Where is keratin most abundant in the skin?

Answer 3

Epidermis, stratum corneum (top layer), hair and nails too

Question 4

What are the two types of keratin?

Answer 4

Soft (alpha) and hard (beta) - determined by the secondary structure and suffice bridges

Question 5

What are the four main layers of the epidermis?

Answer 5

Stratum corneum, stratum granulosum, stratum spinosum and stratum basale

Question 6

Describe the stratum corneum layer of the epidermis

Answer 6

Protective layer of the skin with dead cells and intercellular lipids (ceramics) to maintain skin moisture

Question 7

Describe the stratum granulosum layer of the epidermis

Answer 7

This is 2-3 cells thick and has large granules of keratohyalin

Question 8

Describe the stratum spinosum layer of the epidermis

Answer 8

3-4 cells thick with many desmosomes to separate the keratinocytes which gives the layer a spiny appearance

Question 9

Describe the stratum basale layer of the epidermis

Answer 9

Proliferation of epithelial cells occurs here and cells are slightly denser

Question 10

Describe the composition of the basement membrane of the epidermis of the sin

Answer 10

ECM consists of laminin 332, collagen IV and collagen VII

Question 11

What is the role of the basement membrane in the epidermis?

Answer 11

To provide cell polarity, regulate basal function and to anchor the epidermis to the dermis

Question 12

What is the function of the hemidesmosomes in the basement membrane of the epidermis?

Answer 12

Bind the keratin cytoskeleton to the basement membrane

Question 13

What is the role of the dermis?

Answer 13

Provides strength and elasticity to the skin

Question 14

What is the most abundant cell in the dermis?

Answer 14

Fibroblasts

Question 15

What is the function of fibroblasts in the dermis?

Answer 15

Produce elastin, collagen and proteoglycans

Question 16

What is the neuromuscular supply to the dermis like?

Answer 16

Innervated and vascularised

Question 17

What are the three layers of the dermis?

Answer 17

Papillary, reticular and adipose

Question 18

Describe the papillary layer of the dermis

Answer 18

Contains fine, randomly organised type III collagen and elastin, and lies directly below the basement membrane of the epidermis

Question 19

What type of collagen is present in the dermis?

Answer 19

Type III collagen

Question 20

Describe the reticular layer of the dermis

Answer 20

The thickest layer densely packed with collagen providing mechanical strength

Question 21

Which dermal layer is largely responsible for the mechanical strength of the skin, and why?

Answer 21

Reticular layer of the dermis as it is densely packed with collagen

Question 22

What are adherens junctions?

Answer 22

These are more basal than tight joints and involve a cadherin receptor linked to an actin cytoskeleton

Question 23

What are desmosomes?

Answer 23

Provide a connection between intermediate filaments of the cell cytoskeletons of adjacent cells; cadherin receptor is linked to the keratin cytoskeleton

Question 24

What are tight junctions?

Answer 24

These seal adjacent epithelial cells in a narrow band just beneath their apical surface. Claudin and occluding molecules seal the intercellular space

Question 25

What are gap junctions?

Answer 25

These form intercellular pores made up of connexins

Question 26

Name four different types of cell-cell adhesions

Answer 26

Adherens, desmosome, tight junctions and gap junctions

Question 27

Name three types of glands that may be present in the skin

Answer 27

Sebaceous, eccrine sweat gland, apocrine gland

Question 28

What is a sebaceous gland?

Answer 28

Exocrine gland (secreted into duct) usually found attached to a hair follicle which produces sebum to lubricate skin

Question 29

What is acne caused by?

Answer 29

Infection of the sebaceous glands

Question 30

How are sebaceous glands affected by puberty?

Answer 30

The gland is sensitive to androgens, and enlarges at puberty as a result

Question 31

What is the role of the eccrine gland?

Answer 31

To produce watery sweat for thermoregulation

Question 32

What is the difference between eccrine and apocrine glands?

Answer 32

They are both sweat glands but apocrine glands are associated with hair follicles whereas eccrine glands are not

Question 33

Describe the structure of the eccrine sweat gland

Answer 33

Has an excretory duct and a secretory coil

Question 34

What is the role of the apocrine gland?

Answer 34

To secrete sweat associated with hair follicles, and is found in the armpit and pubic region

Question 35

Where are apocrine glands usually found?

Answer 35

Axilla and pubic regions

Question 36

What causes the smell of body odour from sweating?

Answer 36

Sweat secretion itself is odourless, but is broken down by bacteria on the skin leading to the release of volatile fatty acids which produce the odour

Question 37

What are the two types of hair follicle?

Answer 37

Vellus and terminal

Question 38

What is a villus hair follicle?

Answer 38

A hair follicle found on body hair

Question 39

What is a terminal hair follicle?

Answer 39

A hair follicle found on the scalp or with secondary sexual hair

Question 40

Which cells produce hair?

Answer 40

Keratinocytes in the matrix of the hair follicle

Question 41

What cells are involved in controlling hair growth?

Answer 41

Dermal papilla fibroblasts

Question 42

What are the three phases of the hair growth cycle?

Answer 42

Anagen, catagen and telogen

Question 43

What is the anagen phase of hair growth?

Answer 43

Active phase of hair growth

Question 44

What is the catagen phase of hair growth?

Answer 44

Regressive phase of hair growth

Question 45

What is the telogen phase of hair growth?

Answer 45

Resting phase of growth

Question 46

Where are melanocytes found?

Answer 46

In the epidermis (on basement membrane) and in the hair follicle matrix

Question 47

What is the function of melanocytes?

Answer 47

Produce melanin and package it into melanosomes (eumelain and pheomelanin) which are injected into keratinocytes to provide skin with protection against UV radiation

Question 48

Where do melanocytes inject melanin?

Answer 48

Into keratinocytes

Question 49

What are melanocytes?

Answer 49

A form of dendritic cell in the basement membrane of epidermis and in the hair follicle matrix

Question 50

What are Langerhan's cells?

Answer 50

A form of dendritic cell in the basal and spinosum layers of the epidermis

Question 51

What is the role of Langerhans cells?

Answer 51

Act as antigen presenting cells to T cells and are a first line of defence against infection

Question 52

What are Merkel cells?

Answer 52

Involved in sensory perception of the skin (basal layer of epidermis)

Question 53

Where are Merkel cells found?

Answer 53

The basal layer of the epidermis

Question 54

What are mast cells?

Answer 54

Cells involved in the immune response by secreting histamine

Question 55

Where are mast cells found?

Answer 55

Dermis of the skin

Question 56

What is a superficial skin wound?

Answer 56

Damage to epidermis only

Question 57

What is a partial thickness skin wound?

Answer 57

Damage to epidermis and dermis

Question 58

What is a full thickness skin wound?

Answer 58

Damage to epidermis, dermis and hypodermis

Question 59

What are the three stages of wound healing?

Answer 59

Inflammation, proliferation and maturation

Question 60

How long should it take for a wound to heal?

Answer 60

Less than 6 weeks

Question 61

Outline the inflammation phase of wound healing

Answer 61

Blood clot is formed to seal wound and immune response is initiated

Question 62

Outline the proliferation phase of wound healing

Answer 62

Keratinocytes move over the wound to create a barrier, fibroblasts infiltrate wound site to produce ECM to form the new dermis and repair damaged blood vessels

Question 63

Outline the maturation phase of wound healing

Answer 63

Replace immature tissue with mature tissue