10 - Skin

Question 1

What is dermatology?

Answer 1

Speciality of medicine that deals with skin and skin diseases

Question 2

Name common skin diseases

Answer 2

Skin cancers, inflammatory conditions such as acne, eczema and psoriasis and many systemic diseases will have a skin manifestation.

Question 3

What is skin?

Answer 3

The skin is a single organ and has complex inter relationships with other organ systems. This includes through endocrine, immune, vascular and neural mechanisms.

Question 4

Name the 8 functions of the skin

Answer 4

1. Protection against injury
2. Protection against pathogenic organisms
3. Waterproofing and fluid conservation
4. Thermoregulation
5. Protection against radiation, absorption of ultra violet radiation and vitamin D production
6. Surface for grip
7. Sensory organ
8. Cosmetic

Question 5

What are the 3 main layers of skin? (From outside to inside)

Answer 5

Epidermis,
Dermis,
Subcutis.

Question 6

Name the apendigeal structures

Answer 6

Pilo-sebaceous unit (follicle, hair shaft, sebaceous gland and pilo erecti muscle), 
Sweat glands (apocrine and eccrine).

Question 7

Describe the structure of the epidermis

Answer 7

The epidermis consists of keratinocytes arranged in 4 layers (stratum basale, spinosum, granulosum and corneum - from inside to outside)

Question 8

Name the other cell types in the epidermis

Answer 8

Melanocyte, Langerhans cell, Merkel cell

Question 9

What is the function of a Langerhans cell?

Answer 9

antigen presenting cell

Question 10

What is the function of a Merkel cell?

Answer 10

involved in sensation

Question 11

What lies between the epidermis and the dermis?

Answer 11

Basement membrane zone. Epidermis is attached to the dermis via hemi-desmosomes, anchoring plaques and a multitude of proteins

Question 12

Why is the basement membrane zone clinically important?

Answer 12

A genetic abnormality resulting in an abnormality of a protein in this region can give rise to a blistering condition eg epidermolysis bullosa

Question 13

Describe the structure of the dermis.

Answer 13

Supportive connective tissue consisting of collagen, elastin and glycosaminoglycans.

Question 14

How thick is the dermis?

Answer 14

Varies between 0.1mm (eyelids) and 3 mm (back)

Question 15

What synthesises collagen, elastin and glycosaminoglycans?

Answer 15

Fibroblasts

Question 16

How is thermoregulation achieved?

Answer 16

Skin blood flow, sweating, shivering, behaviour

Question 17

What other cell types are found in the dermis?

Answer 17

Dermal dendritic cells are found along with other immunocompetent cells

Question 18

What is the subcutaneous layer?

Answer 18

Connective tissue and fat

Question 19

What is a melanocyte?

Answer 19

Melanocytes are dendritic cells located within the basal layer of the epidermis.

Question 20

What is the function of a melanocyte?

Answer 20

They produce the pigment melanin in organelles known as melanosomes.

Question 21

How does skin pigmentation work?

Answer 21

1. They produce the pigment melanin in organelles known as melanosomes.
2. These are packaged into granules which move down the dendritic processes and transferred by phagocytosis to adjacent keratinocytes.
3. The melanin granules form a protective cap around the keratinocyte nuclei and protect the DNA within the nucleus from UV induced damage and lead to skin pigmentation. UV radiation mainly within the 290-320 nm spectrum stimulates the melanocytes to produce more melanin. Variation in racial pigmentation is not from differences in melanocyte numbers, but from the number and size of melanosomes produced.