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Accessory Structures
Chapter 5 - A & P Lecture
| Question | Answer |
|---|---|
| what are the accessory skin structures? | hair, glands, nails |
| where is hair found? | found everywhere on human body except palms, soles, lips, nipples, parts of external genitalia, and distal segments of fingers and toes |
| how does hair change? | hair structure and coloration changes as a person ages |
| what is lanugo? | delicate, unpigmented hair of the fetus |
| what is terminal hair? | long, course, pigmented hair of the scalp, eyelids, eyebrows, and with puberty, acill, pubic, and face |
| what is vellus hair? | fine, short hair on the rest of the body |
| where is the shaft within the hair structure? | protrudes above skin surface |
| where is the root within the hair structure? | located below surface; base of root is the hair bulb |
| how many concentric layers does the hair structure have? | 3 (medulla, cortex, cuticle) |
| what is the medulla? | central axis |
| what is the cortex? | forms bulk of hair |
| what is the cuticle? | forms hair surface |
| what is the source of hair? | internal matrix |
| within the hair follicle where is the dermal root sheath? | part of dermis that surrounds the epithelial root sheath |
| within the hair follicle where is the epithelial root sheath? | with internal and external parts |
| what does the internal part contain? | stratum basale that may remain after injury and supply a source of new epidermis |
| when can you view the internal part? | when hairs are pulled out, internal part comes out and is visible as white bulb |
| what does it mean for growth and resting stages of hair to be cyclic? | the are regularly repeated |
| what are the stages for hair growth? | growth stage & resting stage |
| describe the growth stage? | cells added at base and hair elongates |
| describe the resting stage? | 1) follicle shortens and holds hair in place 2) rest 3) then hair falls out of follicle 4)new hair begins |
| what does the amount of time spent in each stage depend on? | type or location of the hair |
| what does regular hair loss mean? | hair is being replaced |
| what is the common cause of permanent hari loss? | pattern baldness |
| what is alopecia areata? | spot baldness most likely due to an autoimmune response |
| what is hair color caused by? | caused by varying amounts and types of melanin |
| what is the muscle in the hair follicle? | a type of smooth muscle called arrector pili |
| describe arrector pili? | extends from the dermal root sheath of the follicle to the papillary layer of the dermis |
| what do muscle contractions cause hair to do? | "stand on end" |
| how are goose bumps formed? | skin pushed up by movement of hair follicle |
| what is holocrine? | death of secretory cells |
| what does sebaceous glands secret? | sebum |
| what is the function of sebaceous glands? | prevents druing and inhibits some bacteria |
| where do most sebaceous glands empty? | hair follicle |
| what areas don't have sebaceous glands attached to their hair follicle? | lips, meibomian, glands of eyelids, genitalia |
| what are the two types of sweat (sudoriferous) glands? | apocrine & merocrine (but apocrine may secrete in a merocrine or holocrine fashion) |
| what are eccrine (merocrine) glands? | most common, numerous in palms and soles, simple coiled tubular glands |
| where do merocrine galnds open? | directly onto surface of skin and have their own pores |
| what do merocrine glands produce? | isotonic fluid (sweat) containing mostly water and some wastes |
| why are merocrine glands important? | regulate body temp. |
| when are apocrine glands active? | puberty |
| where do apocrine glands open? | into hair follicles superficial to opening of sebaceous gland |
| what do apocrine glands secret? | organic compounds that are odorless but when acted upon by bacteria become odiferous |
| where are apocrine glands found? | in axillae, genitalia (external labia, scrotum), around anus |
| do apocrine glands help regulate temp? | no |
| what are ceruminous glands? | modified eccrine sweat glands in the external auditory canal |
| what is cerumen composed of ? | cerumen or earwas is made of a combination of sebum and secretion from ceruminous |
| what is the funciton of cerumionous glands? | with hairs they prevent dirt and insects from entry |
| what are mammary glands? | modified apocrine sweat glands that produce milk |
| describe the structure of nails? | thin plate of layers of dead stratum corneum cells with hard keratin |
| what is the nail body? | stratum corneum; visible portion |
| what does the matrix (nail bed) do? | cells that give rise to the nail |
| what is the nail root? | covered by skin; extends from nail matrix |
| what is the nail matrix and bed composed of? | epithelial tissue with a stratum basale that gives rise to the cells that form the nail |
| do nails grow continuously? | yes, unlike hair |
| how many mm does fingernails grow? | 0.5 to 1.2mm/day (faster than toenails) |
| what is the lunula? | small part of nail matrix seen through the nail body as a whitish, crescent-shaped area at the base of the nail |
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