Integumentary System II

Where is thick skin found, and how many epidermal layers does it have?

Palms and soles; 5 layers.

Where is thin skin found, and how many epidermal layers does it have?

Most of the rest of the body; 4 layers.

Which epidermal layer distinguishes thick skin from thin skin?

Stratum lucidum is present in thick skin.

What four factors contribute to skin color?

Dermal blood supply

Stratum corneum thickness

Carotene concentration

Melanin concentration.

What are the two layers of the dermis?

Papillary layer = superficial; Reticular layer = deep.

What structures are found in the papillary layer of the dermis?

Dermal papillae, capillaries, nerve axons.

What structures characterize the reticular layer of the dermis?

Dense irregular connective tissue, hair follicles, sweat glands, sebaceous glands.

Where is the subcutaneous layer/hypodermis, and is it technically part of the integument?

It is deep to the dermis and is not technically part of the integument.

What is found in the hypodermis, and what is one of its functions?

Adipose tissue, major blood vessels; helps stabilize the integument.

What is hair made of?

Keratin.

How are cells arranged in a hair follicle?

In concentric rings.

Match the three types of hair with their major locations.

Vellus → most of body; Intermediate → arms and legs; Terminal → head.

What are the major functions of hair?

Protection from UV light, insulation, guards entrances to nose and ears, sensory detection when hair moves.

What happens when the arrector pili muscle contracts?

Goose bumps.

What primarily determines hair color?

Variation in melanin production by melanocytes.

What happens to melanin production with age?

Melanin production decreases with age.

What is the correct sequence of the hair growth cycle?

Active → Regression → Resting → Reactivation.

How long does the active phase of hair growth last, and approximately how fast does hair grow?

2-5 years; about 0.33 mm/day.

What happens to the hair during the resting phase?

It loses its attachment to the follicle and becomes a club hair.

What happens during follicle reactivation?

The club hair is lost, and the hair matrix begins producing a replacement hair.

What are the three overall functions of glands in the skin?

Lubricate the epidermis, excrete wastes, assist in thermoregulation.

What do sebaceous glands produce, and what is its major function?

Sebum, which lubricates the skin/hair.

Where are sebaceous glands absent, and where are they especially concentrated?

Absent: palms and soles; high concentration: forehead, face, upper back.

What may occur if sebaceous gland ducts become blocked?

Acne.

Where are apocrine sweat glands concentrated, and what kind of secretion do they produce?

Mainly the axillae/armpits, groin, and nipple regions; they produce a thick/viscous, potentially odorous secretion.

What may apocrine secretions contain, and what strongly influences apocrine glands?

They may contain pheromones and are strongly influenced by hormones.

What is another name for merocrine glands?

Eccrine glands.

Where are merocrine/eccrine glands found, and what is their major function?

Found throughout the body, especially concentrated on palms and soles; produce watery sweat for cooling/thermoregulation.

What is the easiest way to distinguish apocrine from merocrine glands?

Apocrine: limited distribution + thick/odorous secretion + hormonally influenced; Merocrine/eccrine: widespread + watery sweat + thermoregulation + primarily nervous-system controlled.

What are the two specialized types of apocrine glands?

Mammary glands, ceruminous glands.

What do mammary glands produce, and what controls their activity?

Milk, under the control of hormones from the pituitary gland.

Where are ceruminous glands found, and what do they produce?

Found only in the ear canal; produce cerumen (ear wax).

What is the primary function of nails?

Protect the tips of the fingers and toes.

What nail structures should you recognize?

Free edge, lateral nail fold, lunula, eponychium, hyponychium.

Is the epidermis vascular or avascular?

Avascular.

What initially helps defend injured integument against invading bacteria?

The reticuloendothelial system, with macrophages consuming invading bacteria.

What determines the ability of the integument to regenerate after injury?

The layer that was damaged.

From what layer must damaged epidermis be repaired?

Stratum basale — repair occurs from the bottom up.

How does repair of the dermis differ from repair of the epidermis?

The dermis is repaired through connective tissue repair involving fibroblasts.

What effect does infection have on tissue repair?

Infected tissue cannot be repaired while it remains in the inflammatory state.

Match the integumentary infection to the organism(s).

Acne → Propionibacterium acnes

Impetigo → S. aureus or S. pyogenes; Folliculitis/furunculosis/carbunculosis → S. aureus or P. aeruginosa; Necrotizing fasciitis → S. pyogenes.

What happens to the epidermis and dermis with aging?

Both become thinner.

What happens to Langerhans cells with aging?

Their numbers decrease, contributing to decreased immune function.

What happens to vitamin D production with aging?

It declines.

What happens to melanocyte activity with aging?

It declines.

What happens to sweat and sebaceous gland activity with aging?

Glandular activity declines.

What happens to hair follicles during aging?

Some follicles stop functioning, producing thinner, sparser hair.

What happens to skin repair with aging?

Skin repair slows down.

How does reduced blood supply affect aging skin?

Slower healing, reduced ability to lose heat.

Why does aging skin sag and wrinkle?

The dermis becomes thinner and fibers of the reticular layer lose their normal ability to stretch and recoil.

What two major factors are associated with skin wrinkles?

Age and UV light.