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what is hair?
consists of hard, flexible, dead keratinized cells,
What are the functions of hair?
Warn of insects on skin
Hair on head guards against physical trauma
Protect from heat loss
Shield skin from sunlight
what is the shaft?
area that extends above scalp, where keratinization is complete
what is the root?
area within scalp, where keratinization is still going on
what are the three parts to the hair shaft?
medulla, cortex, cuticle
what is the medulla?
central core, not present in fine hairs
what is the cortex?
several layers of flattened cells surrounding the medulla
what is the cuticle?
outer layer consisting of overlapping layers of single cells
where are hair pigments made?
melanocytes in hair follicles
what is red hair made by?
additional pheomelanin pigment
how is gray hair made?
when melanin production decreases and air bubbles replace melanin in shaft
what is the hair bulb?
expanded area at deep end of follicle
what is the wall of follicle composed of?
Peripheral connective tissue sheath, Glassy membrane, Epithelial root sheath
what is the peripheral connective tissue sheath?
Derived from dermis
Also called fibrous sheath
what is the glassy membrane?
acts like a basement membrane, located in between the epithelial root sheath and peripheral connective tissue sheath
what is the epithelial root sheath?
Derived from epidermis
Has external (continuation of epidermis) and internal (derived from matrix cells)
what is the hair matrix?
actively dividing area of bulb that produces hair cells
As matrix makes new cells, it pushes older ones upward
what is hair papilla?
Dermal tissue containing a knot of capillaries that supplies nutrients to growing hai
what are the 2 types of hair growth?
vellus hair, terminal hair
what is vellus hair?
pale, fine body hair of children and adult females
what is terminal hair?
coarse, long hair
Found on scalp and eyebrows, face and neck of males
At puberty
Appear in axillary and pubic regions of both sexes
what does the nail protect?
distal and dorsal surface of fingers and toes
what is the nail matrix?
thickened portion of bed responsible for nail growth
what is the nail fold?
skin folds that overlap border of nail
what is the eponychium?
nail fold that projects onto surface of nail body
Aka cuticle
what is the hyponychium?
area under free edge of plate that accumulates dirt
what is the part of the nail that contains a thickened nail matrix and appears white?
lunule, abnormal color or shape is an indicator of disease
What is another name for sweat glands?
sudoriferous glands
what are the 2 main types of sweat glands?
Eccrine (merocrine) sweat glands
Apocrine sweat glands
what type of cells do sweat glands have?
myoepithelial, Contract upon nervous system stimulation to force sweat into ducts (exocrine gland)
what sweat gland is the most numerous type and is located on palms, soles, and forehead?
Eccrine (Merocrine) Sweat Glands
where do Eccrine (Merocrine) Sweat Glands open to?
open directly on the skin’s surface, they secrete sweat
where can you find apocrine sweat glands?
Confined to axillary and anogenital areas
what do apocrine sweat glands secrete?
viscous milky or yellowish sweat that contains fatty substances and proteins (BO)
where do apocrine sweat glands empty into?
hair follicles which being to function at puberty
what are two modified apocrine glands?
ceruminous and mammary glands
what are ceruminous glands?
lining of external ear canal; secrete cerumen (earwax)
what do mammary glands do?
secrete milk
where can you find sebaceous (oil) glands?
Widely distributed, except for thick skin of palms and soles on hair follicles and secrete into hair follicles
how do sebaceous (oil) glands activate?
Relatively inactive until puberty
Stimulated by hormones, especially androgens
what do sebaceous glands secrete?
sebum
Oily holocrine secretion
Bactericidal (bacteria-killing) properties
Softens hair and skin
Petite
Rhinos
Can’t
Mimic
Big
Elephants
Protection
Regulation of body temperature
Cutaneous sensations
Metabolic functions
Blood reservoir
Excretion of wastes
what are the three barriers of skin?
Chemical barrier
Physical barrier
Biological barrier
what is the chemical barrier?
Skin secretions to inhibit bacterial growth or kill bacteria
Melanin provides a chemical barrier against UV radiation damage
what is the physical barrier?
Provided by the continuity of the skin and the hardness of the keratinized cells
what is the biological barrier?
Dendritic cells and macrophages to stimulate immune response
what is insensible perspiration?
resting body temperature, sweat glands produce about 0.5L of unnoticeable sweat per day
what is sensible perspiration?
to cool the body, sweat gland activity increases to produce up to 3 gallons of noticeable sweat
what are Cutaneous sensory receptors a part of?
nervous system
what is cutaneous sensation?
Respond to stimuli outside body, such as temperature and touch
what do metabolic functions do?
Skin provides the metabolic function of making Vitamin D
important for absorption of calcium
stimulated by the sunlight
what does it mean when the skin is blood reservoir?
Skin can hold up to 5% of the body’s total blood volume
Blood can be diverted to other areas of the body if needed
what is excretion?
Skin can secrete limited amounts of nitrogen-containing wastes, such as ammonia, urea, and uric acid (most of these wastes are excreted via urine)
Sweating eliminates excess water and salts