Which layer of the skin--dermis or epidermis--is better nourished?

The dermis is connective tissue, which is vascular, so its cells would be better nourished than those of the epidermis, which is avascular epithelium.

While walking barefoot in a barn, Jeremy stepped on a rusty nail that penetrated the epidermis on the sole of his foot. Name the layers the nail pierced from the superficial skin surface to the junction with the dermis.

Since the sole of the foot has thick skin, the layers from most superficial to deepest would be the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and startum basale.

The stratum basale is also called the stratum germinativum, a name that refers to its major function. What is that function?

The stratum basale undergoes almost continuous mitosis to replace cells lost by abrasion.

Why are the desmosomes connecting the keratinocytes so important?

The skin is subjected to a lot of abrasion and physical trauma. The desmosomes, which are connecting junctions, help to hold the cells together during such stress.

Which layer of the dermis responsible for producing fingerprint patterns?

The papillary layer of the dermis gives rise to fingerprint patterns.

Which tissue of the hypodermis makes it a good shock absorber?

Fatty tissue in the hypodermis gives it insulating and shock-absorbing properties.

You have just gotten a paper cut. It is very painful, but it doesn't bleed. Has the cut penetrated into the dermis or just the epidermis?

Because there is no bleeding, the cut has penetrated into the avascular epidermis only.

Melanin and carotene are two pigments that contribute to skin color. What is the third and where is it found?

The third pigment contributing to skin color is hemoglobin, the pigment contained in red blood cells found in blood vessels of the dermis.

What is cyanosis and what does it indicate?

Cyanosis is a bluish cast of the skin that indicates that hemoglobin in the red blood cells in the dermal capillaries is poorly oxygenated.

Which alteration in skin color may indicate a liver diorder?

Jaundice or a yellow cast to the skin due to the deposit of yellow bile pigments in body tissues may indicate a liver disorder

What are the concentric regions of a hair shaft, from the outside in?

The regions of a hair from outside in are the cuticle, cortex, and medulla.

Why is having your hair cut painless?

There are no nerves in a hair, so cutting hair is painless.

What is the role of an arrector pili muscle?

The arrector pili muscles pull the hair (normally slanted) to the upright position (when cold or scared).

What is the function of the hair papilla?

The hair papilla contains a knot of capillaries that supplies nutrients to cells of the hair bulb.

Why is the lunule of a nail white instead of pink like the rest of the nail?

The lunule of the nail is white because the thick nail matrix that underlies it blocks the rosy color of the dermal blood supply from showing through.

Why are nails so hard?

Nails are hard because the keratin they contain is the hard keratin variety.

Which cutaneous glands are associated with hair follicles?

Sebaceous (oil) glands and apocrine glands are associated with the hair follicles.

When Anthony returned home from a run in 85ºF weather, his face was dripping with sweat. Why?

His sympathetic nervous system activated his eccrine sweat glands and caused heat-induced sweating in order to cool the body.

What is the difference between heat-induced sweating and a "cold-sweat", and which variety of sweat gland is involved?

Heat-induced sweating occurs all over the body when we are overheated. A cold sweat is emotionally induced sweating that begins on the palms, soles, and armpits and then spreads to other body areas. Both types of sweating are produced by the eccrine sweat glands, but activity of apocrine sweat glands is also likely during a cold sweat.

Sebaceous glands are not found in thick skin. Why is their absence in those body regions desirable?

The palms of the hands and soles of the feet are thick skin areas. It would be dangerous to have oily sols, and oily palms would decrease the ability of hands to hang onto things.

What chemicals produced in the skin help provide barriers to bacteria?

The low pH of skin secretions (acid mantle) inhibits division of bacteria, and many bacteria are killed by dermcidin in sweat, bactericidal substances in sebum, or natural antibiotics called defensins produced by skin cells. Damaged skin secretes cathelicidins that are effective against a certain strain of strep bacteria.

Which epidermal cells play a role in body immunity?

The epidermal dendritic cells play a role in body immunity.

How is sunlight important to bone health?

sunlight causes the skin to produce a precursor of vitamin D from cholesterol. Vitamin D is essential for absorption of calcium from the diet, and calcium is a major component of bone.

When blood vessels in the dermis constrict or dilate to help maintain body temperature, which type of muscle tissue that you learned about (in Chapter 4) acts as the effector that causes blood vessel dilation or constriction?

The effector in this case is smooth muscle.

Which type of skin cancer develops from the youngest epidermal cells?

Basal cell carcinoma develops from the youngest epidermal cells.

What name is given to the rule for recognizing hte signs of melanoma?

The ABCD rule helps one to recognize signs of melanoma.

The healing of burns and epidermal regeneration is usually uneventful unless the burn is a third-degree burn. What accounts for this difference?

First- and second-degree burns can heal uneventfully by regeneration of epidermal cells as long as infection does no occur. Third-degree burns destroy the entire depth of skin and regeneration is not possible. Infection and loss of body fluid and proteins make recovery problematic.

Although the anterior head and face represent only a small percentage of the body surface, burns to this area are often more serious than those to the body trunk. Why?

Burns to the face are serious because damage to the respiratory passageway can occur in such burns.

Which epidermal cell type is most numerous?

keratinocyte

Which cell functions as part of the immune system?

dendritic cell

The epidermis provides a physical barrier due largely to the presence of

keratin

Skin color is determined by

the amount of blood, pigments, oxygenation level of the blood

The sensations of touch and pressure are picked up by receptors located in

the dermis

T or F

The papillary later of the dermis is most responsible for the toughness of the skin

False

Skin surface markings that reflect points of tight dermal attachment to underlying tissues are called

flexure lines

T or F

A sensory receptor is an epidermal derivative.

False

An arrector pili muscle

can cause a hair to stand up straight

The product of this type of sweat gland includes protein and lipid substances that become odoriferous as a result of bacterial action.

apocrine

Sebum

lubricates the surface of the skin and hair, consists of cell fragments and fatty substances, and in excess may cause seborrhea

Which layer of the skin has NO blood vessels?

epidermis

T or F

The hypodermis layer is NOT part of your skin.

True

The skin makes up what percentage of body weight in the average adult?

7%

T or F

Keratin contributes to skin color.

False

This layer of the skin is responsible for our fingerprints.

Papillary dermis

Mitosis occurs in primarily in which stratum of the epidermis?

Basale

What protein gives the epidermis its protective properties?

Keratin

Which cells in the epidermis are key activators of the immune system?

Dendritic cells

Dogs track the scent of epithelial cells that are constantly being shed. These cells shed from which stratum?

Corneum

In which layer of the epidermis would you most expect to find the healthiest cells?

Basale

The dermis is composed of what type of tissue?

Connective

T or F

Keratin is not associated with the dermis.

True

Which layer of the dermis is composed of dense irregular connective tissue?

Reticular layer

Which layer of the dermis is closest to the epidermis?

Papillary layer

Peglike folds of the superficial layer of the dermis are called dermal

papillae

Sudoriferous glands are also known as ____ glands

sweat

What is sweat mostly composed of?

Water

The sweat glands that are important in body temperature regulation are the ____ glands.

eccrine

This gland, found in the skin, is also a holocrine gland.

Sebaceous

T or F

Ceruminous glands are not accessory glands of the skin

False

Hair and nails are modifications of the

epidermis

The protein found in our hair and nails is

keratin

The smooth muscle associated with a hair follicle is called

arrector pili

T or F

The lunule is associated with hair.

False

T or F

The medulla is associated with the nails.

False

When people gain weight, they often also gain inches due to an accumulation of fat in which layer?

Hypodermis