Tissues 11 - Hair and Nails Flashcards
Where is hair not found?
Glaborous skin of palms, soles, glans penis and vulval Introitus.
Where is follicle density greatest?
Face
What is the function of hair?
Protection
Sensation
Thermoregulation
Communication/sexual attraction
What are the types of hair?
- Lanugo- fine/long, formed in fetus at 20 weeks, Usually shed before birth. May be seen in premature babies or in anorexics.
- Vellus - Short, fine hairs. Light coloured and cover most of the body.
- Terminal - longer, thicker, darker. Found on scalp, eyebrows, eyelashes, beard, pubic and axillary areas. Originate as vellus hairs then differentiate at puberty (stimulated by androgens).
What is the infundibulum?
The point above the site of entry of the sebaceous duct.
Describe the hair shaft.
Consists of an outer cuticle that encloses a cortex of packed keratinocytes and an inner medulla (in terminal hairs)
Where are the melanocytes and germinative cells located?
In the hair bulb.
What is the arrector pili muscle?
Smooth muscle under autonomic control.
Contracts with cold, fear and emotion which erects the hair.
What are sebaceous glands associated with?
Follicles
At puberty, what are sebaceous glands sensitive to?
Androgens.
How is sebum produced?
Holocrine secretion, whereby cells break down and release their lipid cytoplasm.
What are the 3 phases of hair growth?
Anagen - growing phase. Usually 80-90% hairs are in anagen phase.
Catagen - Resting phase (few weeks). Hair protein synthesis stops, follicle retreats towards surface. 10-20% hairs in catagen phase
Telogen - Shedding phase, presence of hairs with a short club root. 50-100 hairs shed every day, 1% of hairs in telogen
Explain nail structure.
Nail matrix contains dividing cells which mature, keratinise and move forwards, forming nail plate.
Nail bed adherent to nail plate (nail bed also produces small amount of keratin).
What is the hyponychium?
Thickened epidermis underlying the free margin of the nail.
