Structure and Function of skin

Question 1

The developmental growth pattern of skin follow which lines?

Answer 1

Blashcko’s lines (not following any nerves, vessels or lymphatics)

Question 2

What are melanocytes and where do they migrate from?

Answer 2

Pigment producing cells from the neural crest.

Question 3

95% of the epidermis is made up of what cells?

Answer 3

Keratinocytes, they contain structural keratins

Question 4

What type of epithelium is the epidermis?

Answer 4

Stratified squamous

Question 5

What are the 4 epidermal cell layers?

Answer 5

Basal Layer (Deep)
Prickle cell layer
Granular Layer
Keratin layer (Superficial)

Question 6

What is meant by differentiation?

Answer 6

Keratinocytes migrating from the basement membrane, this takes 28 days. Continuously regenerates the epidermis.

Question 7

Describe the basal layer

Answer 7

Usually one cell thick, small and cuboidal.
Lots of intermediate filaments (keratin)
Highly metabolically active.

Question 8

Describe the prickle cell layer

Answer 8

Larger Polyhedral cells (think P for Prickle, P for Polyhedral)
Lots of desmosomes (connections)
Intermediate filaments connect to desmosomes

Question 9

Describe the granular layer

Answer 9

2-3 layers of flatter cells
Large keratohyalin granules – contain structural filaggrin & involucrin proteins 
Odland bodies (lamellar bodies)
High lipid content
Origin of “cornified envelope”
Cell nuclei lost

Question 10

Describe the keratin layer

Answer 10

Corneocytes (overlapping non-nucleated cell remnants)
Insoluble cornified envelope
80% keratin & filaggrin
Lamellar granules release lipid
Tight waterproof barrier

Question 11

Melanocytes

Answer 11

Migrate from the epidermis to neural crest in first 3 months of foetal development
basal layer and above
pigment producing dendritic cells

Question 12

What is Nelson’s Syndrome?

Answer 12

A disorder where melanin stimulating hormone is produced in excess by the pituitary (resulting in far darker than expected skin)

Question 13

What layer are Langerhan’s cells found?

Answer 13

Prickle cell layer in epidermis

Question 14

What do langerhans cells do?

Answer 14

They are antigen presenting cells that pick up antigens in the skin and circulate them to the lymph nodes via the lymphatic system.

Question 15

Phases of hair growth, what is anagen, catagen and telogen?

Answer 15

anagen = growing 
catagen = involuting 
telogen = resting

Question 16

What is the dermo-epidermal junction?

Answer 16

It is an interface between the epidermis and dermis. It holds a key role in epithelial-meschymal interactions e.g.:

• support, anchorage, adhesion, growth and differentiation of epidermal cells.
• it is a semi permeable membrane that acts as a barrier and a filter.

Question 17

Cells in the dermis:

Answer 17

Fibroblasts: secrete collagen

Macrophages: scavengers, antigen presentation

Lymphocytes: immune reactions

Langerhans cells (also in epidermis): antigen presentation

Mast cells: chemical messengers

Question 18

What is the most important structure in the skin that determines drug penetrance?

Answer 18

Stratum corneum

Question 19

Tuberous Sclerosis

Answer 19

• One of the most common genodermatoses
• May present as infantile seizures
• Earliest sign is the ash leaf macule
• Autosomal Dominant
• It is the next most common genodermatosis after NF type 1
• Depigmented macule found in 90% of tuberous sclerosis
• Other skin signs are shagreen patches and enamel pitting.

Question 20

Epidermolysis Bullosa:

Answer 20

3 types: simple, junctional and dystrophic

• Dominant, recessive, new mutation or acquired.
• Variable severity - blistering at birth does not determine prognosis

Question 21

Features of Neurofibromatosis Type 1:

Answer 21

Café au lait
Neurofibromas
Plexiform neuroma - diffuse
Axillary or inguinal freckling
Optic glioma
2 or more Lisch nodules
A distinctive bony lesion

Question 22

Eczema is a complex disease, describe some of the genetic factors:

Answer 22

Filaggrin (a skin barrier gene, mutations are common approx 1 in 10)
IL-4 and IL-13

Question 23

Eczema Hepeticum

Answer 23

Monomorphic punched out lesions