Skin Structure and Function 2 Flashcards
In what layers of the skin are melanocytes found?
Basal and suprabasal
In what parts of the skin are Langerhans cells found?
Prickle cell layer, dermis and lymph nodes
In what part of the skin are merkel cells found?
Basal layer
When do melanocytes migrate from the neural crest to the epidermis?
During the first 3 months of foetal development
What organelles do melanocytes contain?
Melanosomes
What do melanosomes do?
Convert tyrosine (amino acid) to melanin pigment
What are 2 types of melanin and what colour are they?
Eumelanin (brown or black)
Phaeomelanin (red or yellow)
Different combinations of these give different hair colours)
What happens to melanin produced in melanosomes?
Melanin is sent in packages (melanin granules) to surrounding keratinocytes through the melanocyte limbs (dendritic processes) where it absorbs light (neutral density filter)
Form protective melanin caps over the nucleus protecting the DNA in basal cells
What is another name for full melanosomes?
Melanin granules
What causes a tan when we go into the sun?
An increase in the melanin produced
What is the origin of langerhans cells?
Mesenchymal origin - bone marrow
What is the function of langerhans cells?
Antigen presenting cell - pick up antigen in skin and circulate to lymph nodes via lymphatic system
What is the name(s) of the characteristic organelle found in Langerhans cells?
Birbeck granules
Also called racket organelle
Where in basal layer are merkel cells found?
Between keratinocytes and nerve fibres
What is the purpose of merkel cells?
Act as mechanoreceptors
What makes up the pilosebaceous unit?
Hair shaft
Hair follicle
sebaceous gland
erector pili muscle
What type of muscle is the erector pili muscle?
Smooth
Parts of the hair shaft from outside in?
Cuticle
Cortex
Medulla
What is the name of the part of the pilosebaceous unit that produces hair?
Hair follicle
What is the name of the structure at the base of the hair follicle?
papilla of hair follicle
What are the 2 parts of the hair root sheath?
Internal root sheath
External root sheath
What pigments hair?
Melanocytes above dermal papilla (pigmented melanisation of the matrix)
What structure is located around the papilla of the hair follicle?
Matrix
What are the 3 phases of hair growth?
Anagen
Catagen
Telogen
What is the hair doing during anagen?
Growing
How long is anagen typically?
3 - 7 years
What happens to hair during catagen?
Involuting - transition phase where hair cell division declines and the root shrinks to 1/3 of original size
How long is catagen usually?
Few weeks
What happens to hair during telogen?
Resting - falls out/ gets pushed out
How long is telogen generally?
3-4 months
Is phases of hair growth normally synchronised in humans?
No, however you can synchronise you hair cycle e.g. chemo
What endogenous group of chemicals impacts phases of hair growth?
Hormones e.g. thryoxine, androgen
What is the name for the development of male sexual characteristics in females?
what is an example of a cause of this?
Virilisation
Excess androgen from a tumour
Type of hair in utero?
Lanugo
Type of hair found on a woman’s cheek or a prepubescent child (soft and lacks pigment)?
Vellus - “peach fuzz”
Name of thick, strong, pigmented hair that has fully matured e.g. head hair?
Terminal hair
What is the cortex of the hair sheath made up of?
hard keratin
what is the medulla of the hair sheath made up of?
Soft keratin
What part of the hair follicle contains multiple vascular channels?
Papilla
What part of the hair follicle contains keratin producing cells?
Matrix
On a typical head of hair, what % of hair will be in each phase of growth?
90% = anagen 10% = catagen <1% = telogen
What is the name for the extension of skin fold covering the nail root?
Cuticle
What is the name for the white crescent at the bottom of the nail?
Lunula
What is the proper name for the actual hard part of the nail?
Nail plate
What is the name of the part under the nail plate that secures the free nail edge?
Hyponychium
What is the name of the part under the nail plate that you can see (up until the lunula)?
Nail bed
What is the name of the part under the nail plate that you can’t see?
What happens here?
Nail matrix
Cells divide and then produce hard keratin
What type of connective tissue are nails made of?
Specialised keratin
On average, how much do nails grow per day?
0.1mm
Do finger nails or toe nails grow faster?
Finger nails
Do nails grow faster in the summer or winter?
Summer
