PD2 Skin, hair and nails - anatomy and physiology

skin layers

epidermis, dermis, hypodermis, appendages

outermost part of the skin

epidermis

Is the epidermis vascular or avascular?

avascular

what major layer of the epidermis protects the body against harmful environmental substances and restricts water loss?

stratum corneum

what major layer of the epidermis is where keratin cells are synthesized?

cellular stratum

what lies beneath cellular stratum and connects epidermis to dermis?

basement membrane

what is the richly vascular connective tissue layer which separates epidermis from cutaneous adipose tissue?

dermis

components of the dermis

-elastin, collagen and reticulin fibers

-sensory nerve fibers

-autonomic motor nerve

what layer of the skin is the subcutaneous layer filled with fatty cells which connects the dermis to underlying organs?

hypodermis

functions of the hypodermis

generates heat, provides insulation, provides shock absorption, provides calorie reserve

Appendages of the skin

eccrine sweat glands, apocrine sweat glands, sebaceous glands, hair, nails

what skin appendage opens directly onto the surface of the skin and regulates body temp through water secretion?

eccrine sweat glands

eccrine sweat glands are distributed throughout the body EXCEPT at...

lip margins, eardrum, nail beds, inner surface of prepuce and glans penis

what appendage of the skin is larger and located more deeply than eccrine glands and secrete white fluid containing protein, carbs and other substances in response to emotional stimuli?

apocrine sweat glands

T/F: apocrine sweat glands are odorless

True

where are apocrine sweat glands found?

axillae, nipples, areolae, anogenital area, eyelids and external ears

what appendage of the skin secrets sebum, a lipid rich substance which keeps skin and hair from drying out, which is stimulated by sex hormones and varies according to hormonal levels?

sebaceous glands

what appendage of the skin is formed by epidermal cells that invaginate into dermal layers and have melanocytes in their shaft that provides its color?

hair

short, fine, soft and non pigmented hair

vellus

coarser, longer, thicker and usually pigmented hair

terminal

males and females have about the same number of hair follicles that are stimulated to differential growth by _________

hormones

epidermal cells converted to hard plates of keratin

nails

stratum corneum layer of skin covering the nail root

cuticle or eponychium

soft tissue surrounding the nail border

paronychium

why is the skin of infants and children smoother than that of adults?

absence of coarse terminal hair

substance covering the skin of the fetus

-mix of sebum and cornified epidermis

vernix caseosa

subcutaneous fat is poorly developed in newborns which predisposes them to..

hypothermia

fine silky hair which covers newborn's body, particularly on shoulders and back

lanugo

-shed within 10-14 days

most infants hair is shed by about _________ months of age

2-3 months

when do eccrine glands start to function in infants?

after 1 month

when do apocrine glands start to function in infants?

they do not function

-less oily

-inoffensive perspiration

what glands enlarge and become active in adolescents, increasing axillary sweating and sometimes body odor?

apocrine glands

in adolescents, increase sebum production occurs in response to increased hormone levels, primarily androgen, which predisposes them to _______

acne

what are some skin changes that occur in pregnant women?

-increase blood flow to skin (especially hands and feet) from peripheral vasodilation and increase number of capillaries

-acceleration of sweat and sebaceous gland activity (assist in dissipating excess heat)

-vascular spiders and hemangiomas that are present may increase in size

-skin thickens, fat is deposited in subnormal layers

most pregnant women have some degree of skin darkening beginning in early pregnancy. Where may this occur?

face, nipples, areolae, axillae, vulva, perianal skin, and umbilicus (90%)

what are some skin changes that occur in older adults?

-decrease sebaceous and sweat gland activity

-epidermis thins and flattens (parchment appearance)

-dermis is less elastic -subcutaneous tissue also decreases

-gray hair

-axillary and pubic hair production declines

-hair follicle size changes

-nail growth slows

in older adults, subcutaneous tissue also decreases giving joints and bony prominences a _________ appearance

sharp, angular

-hollows in thoracic, axillary and supraclavicular regions deepen

in older adults, terminal scalp hair progressively transitions into ______ hair

vellus

(vellus to terminal in hair of nares and on tragus of men's ears)