Hair and Nails Flashcards
What are the functions of hair?
-Protection against UV, minor injury and eyelashes protect the eyes
-Sensation- hairs have sensory innervation within the follicles which can amplify sensation
-Thermoregulation ( minimal in humans)
- Communication/ sexual attraction
PTSC
Name 2 places that don’t have hair ?
Everywhere except mucous membranes, palms and soles
Name 3 types of hair?
Lanugo- fine and long. Formed in the detus at 20 weeks. Normally shed before birth but maybe seen in premature babies. Also occur in anorexia.
Vellus- short,fine,light and cover most of the body
Terminal- Found on the scalp, pubic and axillarry and beard areas. Longer, thicker, darker. They originate as villus hair and differentiation is stimulated at puberty by androgen.
LVT
what is a pilo-sebaceous unit?
The structure consisting of hair, hair follicle, arrector pili muscle and sebaceous gland.
Name the important structures around the hair?
Hair Bulb- where the hair grows from, sits in the mid/deep dermis
Arrector pilli muscle- raise the hairs in shivering , to keep warm
Sebaceous gland- lubricate the hair
What cells are located in the hair bulb?
germinative cells and melanoctyes cells
What happens to the sebaceous glands during puberty?
-they become large and active
sensitive to androgens
What type of secretion produces sebum?
Sebum is produced by holocrine secretion in which the cells disintergrate to release their lipid cytoplasm
Name the phases of hair growth?
Unlike the skin, which grows continously – hair grows in cycles
Anagen – growth phase. Normally 85% hairs are in this stage. Energy intensive process, higly vascularized, most metabolically active
- rate depends on the body site. Increased vasculature and VEGF expression.
Catagen – Cell division slows and stops. The end of the shaft keratinizes and form a club shape. The dermal papilla and the club moves towards the base of the muscle insertion.
Telogen – Hair is shed actively and the next anagen phase begins. The club hair can take 4-6 weeks to be released. This was originally thought to be passive. Now we know that the hair is actively shed from the follicle
Anagen to Catogen to Telogen to return to Anagen to Early Anagen back to Anagen
What is the portion above the site of entry of the sebaceous duct known as?
infundibulum
What does the hair shaft consist of?
Outer cuticle, the encloses a cortex of packed keratinocytes and an inner medulla (in terminal hairs)
What are the functions of nails?
-Protection (weapon)
-Touch- Manual dexterity
-Communication-Socially
PTC
Protection of the distal fingertip – most sensitive part of the finger
-good job- mechanical stress
very strong –due to dense keratin structure
impervious to chemical assault
Aids tactile discrimination
Communication and sexual attraction context- socially
More true in the animal world, can be used as weapons.
Summarise the structure of nails?
-consists of a plate of hardened and densely packed keratin
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Summarise the growth of nails?
-The nail matrix contains dividing cells which mature , keratinize and move forward to form the nail plate.
Describe the structure of the nail?
The nail bed( produce a small amount of keratin) is adherent to the nail plate.
The adjacent dermal capillaries produce a small amount of pink colour in the nails
The white luna is the visable part of the matrix
The hyponychium is the thickened epidermis that underlies the dree margin of the nail.
