Normal skin and skin appendages

Question 1

List the functions of normal skin

Answer 1

Protective barrier against environmental insults
Temperature regulation
Vitamin D synthesis
Sensation 
Immunosurveillence
Appearance/cosmesis

Question 2

Describe the structure of skin

Answer 2

Epidermis
Dermis
Subcutaneous tissue

PLUS

Skin appendages

Question 3

Describe skin appendages

Answer 3

Formed by skin derived cells

Hair, nails, sebaceous glands, sweat glands

Question 4

List the 4 main cell types in the epidermis

Answer 4

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

Question 5

What is the main function of keratinocytes

Answer 5

Produce keratin (protective barrier)

Question 6

What is the main function of melanocytes

Answer 6

Produce melanin - skin pigment and protection from UV DNA damage

Question 7

What is the main function of Langerhans cells

Answer 7

Present antigens and activate T lymphocytes for immune protection

Question 8

What is the main function of merkel cells

Answer 8

Contain specialised nerve endings for sensation

Question 9

What is the average epidermal turnover time

Answer 9

30 days

Question 10

List the 4 layers of the epidermis from inside to outside

Answer 10

Stratum basale - actively dividing cells (deepest layer)

Stratum spinosum - differentiating cells

Stratum granulosum - Cells lose their nuclei and contain granules of keratohyaline - secrete lipid into intercellular spaces

Stratum corneum - Horny layer - Layer of keratin (most superficial)

Question 11

What does each layer of epidermis represent

Answer 11

Different level of maturation of keratinocytes

Question 12

Describe the 5th layer of epidermis found in areas of thick skin such as the sole

Answer 12

Stratum lucidum
Found under stratum corneum
Consists of paler, compact keratin

Question 13

Describe the structure of the dermis

Answer 13

Collagen
Elastin 
Glycosaminoglycans 
Immune cells
Nerves
Skin appendages
Lymphatics
Blood vessels

Question 14

List the 3 types of hair

Answer 14

Lanugo - fine long hair in fetus
Vellus - short fine hair all over body
Terminal - coarse long hair

Question 15

Describe the structure of hair

Answer 15

Consists of modified keratin
Contains hair shaft - keratinized tube
Hair bulb - actively dividing cells and melanocytes which give pigment to the hair

Question 16

Describe the growth cycle of hair

Answer 16

Anagen (long growing phase)
Catagen (short regressing phase)
Telogen (resting/shedding phase)

Question 17

Describe the structure of the nail

Answer 17

The nail is made up of a nail plate (hard keratin) which arises from the nail matrix at the posterior nail fold, and rests on the nail bed.

The nail bed contains blood capillaries which gives the pink colour of the nails.

Question 18

Describe the structure of a pilosebaceous unit

Answer 18

Sebaceous gland plus hair follicle

Question 19

What is the function of the sebaceous glands

Answer 19

Produce sebum - lubricates and waterproofs the skin

Question 20

What stimulates sebaceous glands?

Answer 20

Conversion of androgens to dihydrotestosterone

Question 21

What is the function of sweat glands

Answer 21

Regulate body temp

Question 22

What are sweat glands innervated by?

Answer 22

Sympathetic nervous system

Question 23

Name and describe the 2 types of sweat gland

Answer 23

Eccrine - all over body

Apocrine - axilla, areola, anus, genitalia and modified ones in external auditory canal

Question 24

Describe the four stages of wound healing

Answer 24

Haemostasis - vasoconstriction, platelet aggregation, clot formation

Inflammation - vasodilation, migration of neutrophils and macrophages, phagocytosis of cellular debris and invading bacteria

Proliferation - granulation tissue formation and angiogenesis, re-epithelialisation

Remodelling - collagen fibre re-organisation and scar maturation