Lecture 2- Anatomy of the skin part 2

Question 1

Where is hair located?

Answer 1

• On the skin all over the body, but not the palms +soles of feet (thick skin).
• Most prominent on head

Question 2

What does hair consist of?

Answer 2

• Hair shaft
• Hair follicle
• Arrector pili muscle
• Sebaceous gland

Question 3

What is the role of the arrector pili muscle associated with hair?

Answer 3

• Contracts to make hair stand on end

- This is useful for insulation and also in fight or flight

Question 4

What does the sebaceous gland associated with hair do?

Answer 4

• Produces sebum which is a natural moisturizer/ water repellent
• Sebum travels from the gland up the hair shaft to the surface of the skin

Question 5

What is lanolin?

Answer 5

Sheep sebum, is used in skin care products

Question 6

How does acne occur? What areas have increased risk of acne due to this?

Answer 6

• Acne is when hair follicles are blocked and infection occurs
• An increase in sebum production increases the risk of acne
• There is the highest production of sebum on shoulders +face and so this why acne common in these places

Question 7

What are the two types of sweat glands?

Answer 7

• Eccrine = found everywhere, used for thermoregulation

- Apocrine = specialized, situated deeper in the skin for release in the base of the hair follicle. Are ‘oily’

Question 8

What are the three types of skin receptors?

Answer 8

• Tactile
• Lamellar
• Bulbous

Question 9

What is the basic difference between tactile and lamellar skin receptors?

Answer 9

• Tactile are situated shallow on the skin (near surface) and detect finer details
• Lamellar are situated a lot deeper in the skin and detect intense stimuli

Question 10

What is the function/s of nails?

Answer 10

• Protect fingertips
• Enhance sensation: sensory receptors require deformation and fingernails allow this and when force is applied receptors will push against hard surface and change shape (particularly important for tactile receptors)

Question 11

What are some examples of accessory structures of the skin?

Answer 11

• Hair
• Sweat glands
• Receptors
• Nails

Question 12

How does skin anatomy relate to its function?

Answer 12

• Aging
• Pigmentation
• Skin cancer/ Vitamin D insufficiency
• Tattoo

Question 13

What does the melanin pigment do?

Answer 13

Absorbs UV light protecting cells from damage

Question 14

Where is the pigment melanin produced in the skin?

Answer 14

Melanocytes (cells)

Question 15

Where is the melanin in melanocytes taken and how?

Answer 15

• Dendrites from melanocyte reach up between cells and melanosomes containing melanin bud off
• These vesicles transfer melanin to epidermal cells (outer layer of skin)

Question 16

What are melanosomes?

Answer 16

Vesicles containing melanin

Question 17

What do moles and freckles have in common?

Answer 17

• Both areas of skin that have higher levels of pigmentation

- Triggered by higher levels of sun exposure

Question 18

How are moles and freckles different?

Answer 18

• Moles are a cluster of melanocytes (more cells i.e over proliferation), they 3D
• Freckles are due to melanocytes over producing melanosomes (more vesicles i.e over production), they 2D

Question 19

Where are melanocytes found?

Answer 19

• Only found in stratum basal (deep level of epidermis at the dermal/epidermal boundary)
• Means are not shed so don’t lose pigment

Question 20

Where are melanosomes found?

Answer 20

-Found throughout the epidermis and are therefore shed with keratinocytes

Question 21

How does the density of melanocytes vary?

Answer 21

-Varies throughout the body but not between races

Question 22

Why does human skin pigmentation vary?

Answer 22

• Skin pigment matches UV exposure
• As humans migrated out of Africa we lost the pigment in our skin
• There is a greater incidence of lightly pigmented skin at higher altitudes due to less UV exposure

Question 23

What is Vitamin D essential for?

Answer 23

Normal calcium metabolism and strong bones (also effects mood if don’t have enough)

Question 24

What is the disease that may arise due to not enough UV light?

Answer 24

• UV light exposure is required for synthesis of vitamin D

- When not enough vitamin D is synthesized this is known as Rickets

Question 25

What happens when skin pigmentation and latitude don’t match?

Answer 25

• Highly pigmented people are more susceptible to vitamin D deficiency at extreme latitudes where there are low levels of vitamin D (rickets)
• Alternatively light skin pigment with high levels of UV leads to cancer explaining why NZ + Australia have high levels of skin cancer compared to other countries

Question 26

What could be causing the increase in cases of rickets in England in recent years?

Answer 26

Lifestyle change means people are spending more time inside and so get less UV light exposure, also potentially due to people being more sunsmart

Question 27

What are the two types of skin cancer?

Answer 27

• Basal cell carcinoma

- Malignant melanoma

Question 28

What are the characteristics of basal cell carcinoma?

Answer 28

• Common but relatively benign
• Originates in Stratum Basale (deep level of epidermis)
• Metastasis is rare (unlikely to break off and move to other parts of body)

Question 29

What are the characteristics of Malignant melanoma?

Answer 29

• Rare but deadly if not treated
• Originates in melanocytes therefore pigmented and easy to spot
• Highly metastatic due to melanocytes sticking dendrites out into cells
• Mortality rate dependent upon tumor

Question 30

What is the trend in skin tumor size and mortality rate and why?

Answer 30

• As melanoma gets thicker/ bigger mortality rate increases
• This is because the bigger it gets the deeper into the layers of the skin it can go. If its small it is contained within the epidermis and is soon shed. As it get thicker goes into dermis and subsequently can travel in circulatory system reaching important organs

Question 31

What are tattoos/how do they relate to skin anatomy?

Answer 31

• Artificial pigment (usually ink) is deposited deep within the skin
• If deposited on skin surface (epidermal layer) would be shed so ink needs to reach the dermis where it won’t be shed but instead captured inside immune cells/scar tissue

Question 32

Why are tattoos painful?

Answer 32

As they have to be deposited deep into the skin to the dermal layer this is where the receptors that detect pain are found

Question 33

What do doctors have to be careful of when trying to detect melanoma?

Answer 33

One way they can diagnose melanoma is to see if there is pigment in the lymph nodes. However, this could also be from a tattoo as over years the tattoo is broken down and ink transported there.