session 6-skin and clinical disease

Question 1

what epithelium makes up the epidermis and what cells are involved?

Answer 1

stratified,keratinised squamous epithelium made up of KERATINOCYTES
note: squamous cells provide large surface area for epidermis to be nourished

Question 2

what are the names of the 4 layers that make up the epidermis?

Answer 2

Stratum corneum
granular layer
prickle cell layer
basal layer

Question 3

which layer does keratinocyte mitosis mainly occur?

Answer 3

basal layer

Question 4

what layer do the daughter keratinocytes move up to, to carry out terminal differentiation?

Answer 4

prickle cell layer

Question 5

what 2 changes occur in the granular layer, regarding the keratinocytes?

Answer 5

• lose their plasma membrane

- differentiate into corneocytes-main cells of stratum corneum (uppermost part of epidermis)

Question 6

what is the role of melanocytes and where do they occur?

Answer 6

• produce melanin which gives skin its colour (black or tanned skin=more melanin produced)
• basal layer

Question 7

where do melanocytes come from?

Answer 7

neural crest (derived from embryonic ectoderm cells)

Question 8

what is the role of langerhans cells and where do they occur?

Answer 8

• present antigens to t lymphocytes and mediate immune repsonse
• prickle cell layer

Question 9

where are langerhans cells originated from?

Answer 9

bone marrow

Question 10

where is the basement membrane/dermo-epidermal junction located and what stain is used to see it best?

Answer 10

• just below the basal layer

- PAS (periodic acid schiff)

Question 11

what is a good prognosis (likely cause of action and outcome) in melanoma (a tumour formed by rapidly dividing melanocytes)?

Answer 11

malignant melanocytes above epidermal basement membrane

Question 12

what cells synthesis the ECM of the dermis and what does the ECM mainly include?

Answer 12

• fibroblasts

- ECM mainly includes collagen (type 1) and elastin

Question 13

what is the name of the formation of irregular fibrous tissue due to a scar or injury?

Answer 13

keloid

Question 14

when is histamine produced from mast cells?

Answer 14

-allergic reactions

Question 15

what does histamine do?

Answer 15

-increases vascular permeability and leakage of plasma from vessels into extravascular sites causing local oedema=swelling and build up of fluid

Question 16

why are nerves located near to the skin surface?

Answer 16

sensation

Question 17

why is the sebaceous gland a holocrine gland?

Answer 17

it’s product of secretion (sebum) is released with remnants of the now dead, mature cell

Question 18

what do the major merocrine sweat glands produce?

Answer 18

• clear,odourless substance consisting of water and salt.

- involved in thermoregulation

Question 19

what do the large apocrine sweat glands produce?

Answer 19

• axillae,genital
• no functional value
• produce odourless, protein rich secretion
• digestion by microbes causes body odour

Question 20

state the 4 main functions of the skin

Answer 20

barrier
sensation
thermoregulation due to sweating and vascular thermoregulation
psychosexual communication (appearance of skin e.g. tattoos and piercings)

Question 21

what are the physical features seen by psoriasis and what is its pathology?

Answer 21

red,itchy,scaly patches on skin
Caused by extreme proliferation of basal layer, causing gross thickening of prickle cell layer and production of excessive stratum corneum cells

Question 22

what is alopecia areata?

Answer 22

autoimmune attack against hair follicles

Question 23

what is vitiligo?

Answer 23

• depigmentation of the skin

- autoimmune response attacking melanocytes,leading to hair loss (alopecia)

Question 24

What reacts to cause allergic contact dermatitis?

Answer 24

Langerhans cells

Question 25

Melanin from melanocytes in basal layer is fed out to surrounding keratinocytes through….

Answer 25

Dendrites

Question 26

What is a good prognosis of malignant melanoma?

Answer 26

Superficial growth I.e. Above epidermal basement membrane

Question 27

Why does psoriasis lead to dry scaly skin?

Answer 27

• disrupted skin barrier leads to loss of fluid,protein,nutrients and heat
• absorption of harmful agents

Question 28

What 2 diseases affect sensation?

Answer 28

Leprosy (affect skin and mucous membranes and nerves causing discolouration and lumps on skin)
Diabetic sensory neuropathy