Topology and histology of the skin

Question 1

Which is the largest organ in the body?

Answer 1

The skin

Question 2

What is the area of the skin?

Answer 2

2 square metres

Question 3

What is the weight of the skin?

Answer 3

5 kilograms

Question 4

Name four functions of the skin

Answer 4

Protection
Sensation
Thermoregulation
Metabolic function

Question 5

What does the skin protect against?

Answer 5

UV light
Mechanical, thermal and chemical stresses
Dehydration
Pathogens

Question 6

How does the skin sense?

Answer 6

It has receptors that sense touch, pressure, pain and temperature

Question 7

What is thermoregulation?

Answer 7

Maintaining the body temperature

Question 8

What features of the skin are involved in thermoregulation?

Answer 8

Adipose tissue
Hair
Sweat glands
Blood vessels

Question 9

What is the metabolic function of the skin?

Answer 9

Subcutaneous adipose tissue produces vitamin D and triglycerides

Question 10

What are the three layers of skin?

Answer 10

Epidermis
Dermis
Hypodermis

Question 11

Describe the epidermis

Answer 11

Thin outer portion
Contains four layers or five layers depending on thick or thin skin
Stratified squamous epithelium

Question 12

Describe the dermis

Answer 12

Thicker inner portion
Connective tissue layer
Important for sensation, protection and theroregulation

Question 13

Describe the hypodermis

Answer 13

Underneath the dermis
Mainly contains adipose tissue and sweat glands
Produces vitamin D

Question 14

What are dermal papillae?

Answer 14

The dermis extends into the epidermis in thick skin

Question 15

What is the role of dermal papillae?

Answer 15

Helps adhesion between dermal and epidermal layers

Provides large surface area to nourish the epidermal layer

Question 16

Name some things that the dermis contains

Answer 16

Collagen
Elastin
Fibroblasts
Macrophages
Adipocytes
Nerves
Glands
Hair follicles

Question 17

What are the two divisions of the dermis?

Answer 17

Superficial region

Deeper region

Question 18

Describe the superficial region

Answer 18

20% of the dermis
Loose connective tissue
Many capillaries
Contains sensory receptors

Question 19

Describe the deeper region

Answer 19

Dense irregular connective tissue
Collagen and elastin
Sweat glands

Question 20

What is the deep cutaneous plexus?

Answer 20

At the dermal/hypodermal junction

Supplies blood to hypodermic, deeper region as well as hair follicles and sebaceous glands and sweat glands

Question 21

What is the subpapillary plexus?

Answer 21

Lies beneath the dermal papillae

Responsible for thermorgulation

Question 22

What type of epithelium is the epidermis of skin?

Answer 22

Keratinised, stratified, squamous epithelium

Question 23

Name the four layers of thin skin (and name the extra fifth layer of thick skin)

Answer 23

Stratum corneum
(Stratum lucidum)
Stratum granulosum
Stratum spinosum
Stratum basale

Question 24

Where do cells divide?

Answer 24

In the stratum basale

Question 25

What is the amount of time taken for cells to move through the layers?

Answer 25

2-4 weeks

Question 26

Describe the stratum basale

Answer 26

Found closest to the dermis Single layer of cells Cells are dividing

Question 27

Describe the stratum spinosum

Answer 27

8-10 layers of cells High number of desmosomes Keratin

Question 28

Describe the stratum granulosum

Answer 28

3-5 layers of cells Cells start to lose their nuclei and organelles Lipid rich secretions make them water sealant

Question 29

Describe the stratum lucidum

Answer 29

Only present in thick skin | Thin transparent layer

Question 30

Describe the stratum corneum

Answer 30

Dead cells Densely packed keratin 10-20 layers of cells

Question 31

What is a keratinocyte?

Answer 31

Most common cell | 90%

Question 32

What is a melanocyte?

Answer 32

Found only in the basal layer | Produce melanin pigment

Question 33

What is a Langerhans cell?

Answer 33

Found only in the stratum spinosum Lack keratin filaments Antigen presenting cells

Question 34

What is a Merkel cell?

Answer 34

Granular basal epidermal cell Sensitive to touch Mostly found in thick skin

Question 35

What is a Pacinian corpuscle?

Answer 35

Myelinated nerve ending | Pressure sensitive

Question 36

What is a Meissners corpuscle?

Answer 36

Highly sensitive mechanoreceptor found in the palmar surface of fingers and plantar surface of feet

Question 37

Outline differences between thick and thin skin

Answer 37

Thick skin has no hairs, sebaceous glands or apocrine sweat glands Thick skin has a thinner dermis

Question 38

Where are the two types of skin located?

Answer 38

Thick skin is found in areas that undergo abrasion Fingertips Palms Soles of feet

Question 39

What three things determine skin colour?

Answer 39

Carotene pigments in subcutaneous fat Amount of blood and the amount of oxygen it is carrying Amount of melanin

Question 40

How does a melanocyte make melanin?

Answer 40

Tyrosine converted to DOPA | DOPA polymerised to melanin

Question 41

What makes melanin?

Answer 41

Melanocytes

Question 42

What happens to melanin when it has been produced by the melanocytes?

Answer 42

Melanin binds to protein, making a melanoprotein Melanoprotein transported into melanosome Phagocytosed by keratinocytes Keratinocytes take up melanin

Question 43

What is the purpose of melanin?

Answer 43

Protect DNA from UV rays

Question 44

How does melanin protect the nucleus from UV light?

Answer 44

It creates a veil over the nucleus

Question 45

Where are melanocytes found?

Answer 45

Stratum basale

Question 46

How do melanocyte numbers vary in people of different races?

Answer 46

They don't

Question 47

What are the two types of sweat gland?

Answer 47

Eccrine sweat glands | Apocrine sweat glands

Question 48

What is the purpose of eccrine sweat?

Answer 48

Thermoregulation

Question 49

What is the purpose of apocrine sweat?

Answer 49

Thermoregulation | Oderous (attracting opposite sex)

Question 50

What do sebaceous glands produce?

Answer 50

Sebum

Question 51

What are the two parts of the hair?

Answer 51

Hair root and hair shaft

Question 52

What is a nail?

Answer 52

A hard plate of keratin

Question 53

What does the nail sit on?

Answer 53

The nail bed

Question 54

Where does the nail grow from?

Answer 54

The nail root

Question 55

What is the name of the white end of the nail?

Answer 55

Lunula