Integumentary system 2 Flashcards
Where does not hair grow?
palms, palmer surfaces of digits, soles, and plantar surfaces of the digits
hair is
dead, keratinized epidermal cells bonded together by extracellular proteins
Genetics and hormones determine thickness and pattern of distribution
Hair function (3)
- Protection (injury, sun’s rays, eyelashes and eyebrows protect eyes from foreign particles)
- Senses light touch: touch receptors in hair root plexus are activated when hair moves
- Prevents heat loss (scalp)
Structure of hair
Shaft - visible projects above the skin
Root - below the surface into the dermis and sometimes subcutaneous layer
Shaft and Root - consist of 3 concentric layers of cells (medulla, cortex, cuticle)
What surrounds the root of the hair?
hair follicle, consists of
1. external root sheath - downward continuation of the epidermis
2. internal root sheath
1+2=epithelial root sheath or hair follicle
what is at the base of each hair follicle
the bulb, nourishes the growing hair follicle
contains a germinal layer of cells called the hair matrix
Where the hair matrix cells arise from
The stratum Basale, the site of cell division
what does smooth muscle in dermis contracts with cold or fear
Arrector pili
forms goosebumps as hair is pulled vertically
What detects hair movement and senses touch
Hair root plexus
what secretes oil
Sebaceous (oil) glands
what is the three stages of hair growth cycle
Growth stage (2-6 years) matrix cells at base of hair root are active producing length
Regression stage (2-3 weeks) Cells of matrix stop dividing, hair follicle atrophies and hair stops dividing
Resting stage (3 months)
following the resting stage, a new growth cycle begins
old hair falls out as growth stage begins again
What is the normal hair loss/day
70-100 hairs/day
Types of hair in Utero
Lanugo hair: fine non-pigmented downy hair that covers the fetus
Prior to birth, Lanugo hair is replaced by
Terminal hair: coarse, heavily pigmented hair that replaces hair on eyebrows, eyelashes and scalp
Vellus hair: short fine pale hair barely visible to the human eye replaces lanugo on the rest of the body
The type of hair at puberty
Terminal hair replace vellus hair in the axillae and pubic regions of girls and boys and face, limbs, chests of boys.
Hair color is due to….
the amount and type of melanin (passed into cortex and medullary cavity)
Graying of hair occurs because of….
Progressive decline in tyrosinase and decline in melanin production
Dark hair contains
true melanin
Blond and red hair contain
melanin with iron and sulfur added
white hair is due to
lack of melanin and air bubbles in the medullary shaft
partial or complete loss of hair
Alopecia, by genes, aging, endocrine disorders, chemotherapy, skin disease
Chemotherapy kills
rapidly dividing cells such as hair matrix cells (the 15% of hairs in resting stage are not affected0
Excessive body hair or body hair in areas that are not usually experienced by females or prepubertal males
Hirsutism - caused by tumor in the adrenal glands, ovaries or testes that produce an excessive amount of androgens
Genetic predisposition where androgens inhibit hair growth
Androgenic Alopecia or male pattern baldness