session 6-skin and clinical disease Flashcards
what epithelium makes up the epidermis and what cells are involved?
stratified,keratinised squamous epithelium made up of KERATINOCYTES
note: squamous cells provide large surface area for epidermis to be nourished
what are the names of the 4 layers that make up the epidermis?
Stratum corneum
granular layer
prickle cell layer
basal layer
which layer does keratinocyte mitosis mainly occur?
basal layer
what layer do the daughter keratinocytes move up to, to carry out terminal differentiation?
prickle cell layer
what 2 changes occur in the granular layer, regarding the keratinocytes?
- lose their plasma membrane
- differentiate into corneocytes-main cells of stratum corneum (uppermost part of epidermis)
what is the role of melanocytes and where do they occur?
- produce melanin which gives skin its colour (black or tanned skin=more melanin produced)
- basal layer
where do melanocytes come from?
neural crest (derived from embryonic ectoderm cells)
what is the role of langerhans cells and where do they occur?
- present antigens to t lymphocytes and mediate immune repsonse
- prickle cell layer
where are langerhans cells originated from?
bone marrow
where is the basement membrane/dermo-epidermal junction located and what stain is used to see it best?
- just below the basal layer
- PAS (periodic acid schiff)
what is a good prognosis (likely cause of action and outcome) in melanoma (a tumour formed by rapidly dividing melanocytes)?
malignant melanocytes above epidermal basement membrane
what cells synthesis the ECM of the dermis and what does the ECM mainly include?
- fibroblasts
- ECM mainly includes collagen (type 1) and elastin
what is the name of the formation of irregular fibrous tissue due to a scar or injury?
keloid
when is histamine produced from mast cells?
-allergic reactions
what does histamine do?
-increases vascular permeability and leakage of plasma from vessels into extravascular sites causing local oedema=swelling and build up of fluid
why are nerves located near to the skin surface?
sensation
why is the sebaceous gland a holocrine gland?
it’s product of secretion (sebum) is released with remnants of the now dead, mature cell
what do the major merocrine sweat glands produce?
- clear,odourless substance consisting of water and salt.
- involved in thermoregulation
what do the large apocrine sweat glands produce?
- axillae,genital
- no functional value
- produce odourless, protein rich secretion
- digestion by microbes causes body odour
state the 4 main functions of the skin
barrier
sensation
thermoregulation due to sweating and vascular thermoregulation
psychosexual communication (appearance of skin e.g. tattoos and piercings)
what are the physical features seen by psoriasis and what is its pathology?
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
what is alopecia areata?
autoimmune attack against hair follicles
what is vitiligo?
- depigmentation of the skin
- autoimmune response attacking melanocytes,leading to hair loss (alopecia)
What reacts to cause allergic contact dermatitis?
Langerhans cells
Melanin from melanocytes in basal layer is fed out to surrounding keratinocytes through….
Dendrites
What is a good prognosis of malignant melanoma?
Superficial growth I.e. Above epidermal basement membrane
Why does psoriasis lead to dry scaly skin?
- disrupted skin barrier leads to loss of fluid,protein,nutrients and heat
- absorption of harmful agents
What 2 diseases affect sensation?
Leprosy (affect skin and mucous membranes and nerves causing discolouration and lumps on skin)
Diabetic sensory neuropathy
