Lecture 9- Hair & Nails Flashcards
What are the main functions of Hair?
- Protection
- Sensation (sensory innovation within hair follicles amplify sensation)
- Thermoregulation
- Communication/ sexual
What are the three types of hair?
1) Lanugo
2) Vellus
3) Terminal
Describe Lanugo hair and where it is found on the body
- Fine, long and unpigmented, unmedullated
- Formed in the foetus
- Shed before birth
- Found on premature babies and anorexics
Describe vellus hair and where it is found on the body
- Short, fine, light coloured, unmedullated
- Covers most of your body
Describe Terminal hair and where it is found on the body
- Long, thick dark hair, medullated
- Scalp, eyebrows, eyelashes, pubic, axilla, beards
- start as vellus but differentiate at puberty because of androgens
Describe the structure of hair
- Outer cuticle > cortex > medulla
- cortex makes up most of the fibre.
- medulla may be absent. Found mainly in large fibres. Made of protein and air spaces
- cortex start off as cells but apoptose during keratinisation
Which places is hair not found?
- mucous membranes (mouth, lips, eyes)
- palms and soles
What is a hair follicle
Follicle= invagination of epidermis containing hair
What is the hair bulb and which layer of skin is it found?
Where the hair grows form, sits in mid/deep dermis. Complex interaction between vascular e and hair
Which muscle is associated with the hair and what is its function?
Errector pilli muscle
- raise hairs in shivering, to keep warm
What helps lubricate the hairs
Sebaceous glands
What are the 5 regions of the follicle
1) INFUNDIBULUM: surface of skin
2) ISTHMUS: gland- erector pilli muscle. May also contain stem cells. Inner Sheath layer disintegrates here
3) suprabulbar: outer and inner root sheath
4) BULB: contains matrix which produce cells of hair shaft and inner root sheath. Also contain melanocytes
5) Dermal papilla: loop of capillary blood vessels and fibroblasts- androgen sensative
Describe the hair growth cycle
1) ANAGEN–> growing phase, energy intense, rate depends on body site
2) CATAGEN –> Cell division stops. End of shaft keratinises= club hair. Papilla moves up
3) TELOGEN–> Hair is shed and anlagen starts again
What is the testosterone paradox
Puberty - testosterone
1st Pubic and axillary hair goes from vellus –> terminal
2nd Beard and chest hair
At extremes of age- nose and ear hair grow
Testosterone causes increase in chest and beard hair but decrease in scalp hair
What happens during androgenic alopecia?
Terminal hair on scalp have androgen sensitive follicles
- reduced anlagen and increased telegenic phase
