Skin structure and function 2

Question 1

Recall what melanocytes are and where do they migrate from and to in foetal development ?

Answer 1

The are pigment producing dendritic cells which migrate from the neural crest to the epidermis (basal layer and above)

Question 2

What organelles do melanocytes contain and what is the function of these organelles ?

Answer 2

• Contain organelles : ‘melanosomes’
• Which convert tyrosine to melanin pigment.

Question 3

Where are Full melanosomes (‘melanin granules’) transferred too ?

Answer 3

Transferred to adjacent keratinocyte via dendrites.

Note - pic below shows this happening in stages (it shows them becoming darker)

There are two different types of melanin pigment:

• –Eumelanin (brown or black)
• –Phaeomelanin (red, yellow)

Question 4

Appreicate the pick of the epidermis (also shows where the basement membrane is)

Answer 4

Question 5

What is the cell shown here ?

Answer 5

Melanocytes

Question 6

What protects the nucleur DNA in basal cells ?

Answer 6

Melanin caps (formed by the organelles in melanocytes)

Question 7

What disease is shown here ?

Answer 7

Vitiligo

Question 8

What is vitiligo ?

Answer 8

It is an autoimmune disease with loss of melanocytes

Question 9

What disease is shown here ?

Answer 9

Albinism

Question 10

What is albinism ?

Answer 10

It is a disorder where there is a genetic partial loss of pigment production

Question 11

What condition is shown here?

Answer 11

Nelsons syndrome

Question 12

What is nelsons syndrome ?

Answer 12

It is a disorder where melanin stimulating hormone is produced in excess by the pituitary gland

Question 13

Name a tumour of the melanocyte cell line ?

Answer 13

Malignant melanoma

Question 14

What is the origin of langerhans cells ?

Answer 14

They are from the bone marrow

Question 15

Where do langerhans cells reside in the epidermis and what 2 other places can they be found ?

Answer 15

Reside in the prickle layer of the epidermis and also are found in the dermis and in lymph nodes

Question 16

What is the function of langerhans cells ?

Answer 16

•Involved in the skin immune system

– Antigen presenting cells

– Pick up antigen in skin and circulate to lymph nodes (prob why they are also found in lymph nodes) via lymphatic system

Question 17

What type of cell is shown in the picture ?

Answer 17

Langerhans cells

Question 18

Where are merkle cells located in the skin ?

Answer 18

Located in the basal layer (stratum basale)

Question 19

What is the function of merkle cells in the skin ?

Answer 19

Mechanoreceptors - sensory receptor that responds to mechanical pressure or distortion.

Question 20

Merkle cell cancer as shown in the pic is a rare form of skin cancer - is it associated with high or low mortality and what causes it?

Answer 20

Caused by viral infection and associated with high mortality

Question 21

Label the hair follicle and what is this unit also referred to ?

Answer 21

The pilosebaceous unit

Question 22

Name 2 hormones which can influence hair growth/development ?

Answer 22

Androgens, thyroxine

Question 23

What is the gland called which is adjacent to the hair follicle ?

Answer 23

Sebaceous gland

Question 24

Describe the 3 main phases of hair growth ?

Answer 24

Anagen phase[edit]

Anagen is the active growth phase of hair follicles[10] during which the root of the hair is dividing rapidly, adding to the hair shaft. During this phase the hair grows about 1 cm every 28 days. Scalp hair stays in this active phase of growth for 2–7 years; this period is genetically determined. At the end of the anagen phase an unknown signal causes the follicle to go into the catagen phase.

Catagen phase[edit]

The catagen phase is a short transition stage that occurs at the end of the anagen phase.[11] It signals the end of the active growth of a hair. This phase lasts for about 2–3 weeks while the hair converts to a club hair. A club hair is formed during the catagen phase when the part of the hair follicle in contact with the lower portion of the hair becomes attached to the hair shaft. This process cuts the hair off from its blood supply and from the cells that produce new hair. When a club hair is completely formed, about a 2-week process, the hair follicle enters the telogen phase.

Telogen phase[edit]

The telogen phase is the resting phase of the hair follicle.[12] When the body is subjected to extreme stress, as much as 70 percent of hair can prematurely enter a phase of rest, called the telogen phase. This hair begins to fall, causing a noticeable loss of hair. This condition is called telogen effluvium.[13] The club hair is the final product of a hair follicle in the telogen stage, and is a dead, fully keratinized hair.[6] Fifty to one-hundred club hair are shed daily from a normal scalp.[6]

Question 25

Label the specific parts of the hair follicle shown

Answer 25

Question 26

Describe what telogen eeffluvium is

Answer 26

When the body is subjected to extreme stress, as much as 70 percent of hair can prematurely enter a phase of rest, called the telogen phase. This hair begins to fall, causing a noticeable loss of hair. This condition is called telogen effluvium.

Question 27

What condition is shown ?

Answer 27

Alopecia areata

Question 28

What is alopecia areata ?

Answer 28

Autoimmune hair loss

Question 29

What is the feature shown and what could it be caused by ?

Answer 29

Feature is virilisation (the development of male physical characteristics (such as muscle bulk, body hair, and deep voice) in a female or precociously in a boy)

Typically caused by excess androgen which could be caused in turn by a tumour

Question 30

Appreciate the structure of nails

Answer 30

Question 31

Appreciate the growth of nails

Answer 31