A&P 1- Chapter 5: Check your understanding & end of chapter questions

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

The ABCD rule helps one to recognize signs of melanoma.

Skin color is determined by

The amount of blood, pigments, and oxygenation level of the blood.

On an outline diagram of the human body, mark off various regions according to the rule of nines. What percentage of the total body surface is affected if the skin over the following body parts is burned? (a) The entire posterior trunk and buttocks (b) An entire lower limb (c) The entire front of the left upper limb

(a) 36% (b) 9% (c) 2.25% Total percentage: 47.25%

Explain each of these familiar phenomena in terms of what you learned in this chapter: (a) pimples (b) dandruff (c) greasy hair and "shiny nose" (d) stretch marks from gaining weight (e) freckles

(a) Accumulated sebum blocks a sebaceous gland duct, a white head appears. If the material oxidizes and dries, it darkens to form a blackhead. (b) Shingle-like cell remnants of the stratum corneum (cornified cells). (c) The arrector pili muscle contracts to force sebum out of the hair follicles on to the skins surface (shiny nose), and the sebum directly on the hair shaft results in greasy hair. (d) Silvery white scars (striae). (e) Local accumulations of melanin.

Count Dracula, the most famous vampire, rumored to have killed at least 200,000 people, was based on a real person who lived in eastern Europe about 600 years ago. He was indeed a "monster" although he was not a real vampire. The historical Count Dracula may have suffered from which of the following? (a) porphyria (b) EB (c) Halitosis (d) vitilgo. Explain your answer.

(a) Porphyria- Certain enzymes needed to form the heme of hemoglobin of blood are lacking. Without the enzymes, metabolic intermediates of the heme pathway called porphyrins build up, spill into the circulation, and eventually cause lesions throughout the body, especially when exposed to sunlight. The fingers, toes, and nose are disfigured, gums degenerate and teeth become prominent.

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.

-Stratum corneum -Stratum lucidum -Stratum granulosum -Stratum spinosum -Stratum basale

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

Apocrine gland

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

Basal cell carcinoma develops from the youngest epidermal cells.

Why are there no skin cancers that originate from stratum corneum cells?

Because the cells in the stratum corneum are dead.

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

Because the thick nail matrix that underlies it blocks the rosy color of the dermal blood supply from showing through

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.

A man got his finger caught in a machine at the factory. The damage was less serious than expected, but the entire nail was torn off his right index finger. The parts lost were the body, root, bed, matrix, and eponychium of the nail. First, define each of these parts. Then, tell if this nail is likely to grow back.

Body- visible attached portion Root- embedded in the skin Bed- extends beneath the nail Matrix- thickened proximal portion of the nail bed Eponychium- proximal nail fold projects onto the nail body No, the nail is not likely to grow back because the matrix was lost.

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 passageways can occur in such burns.

An arrector pili muscle

Can cause a hair to stand straight up

You go to the beach to swim on an extremely hot, sunny summer afternoon. Describe two ways in which your integumentary system acts to preserve homeostasis during your outing.

Chemical barriers of protection: Melanin provides a chemical pigment shield to prevent UV damage to skin cells. Body temperature regulation: The body releases sweat (body heat) and as that evaporates off the skin it cools the body.

What is cyanosis and what does it indicate?

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

Which cell functions as a part of the immune system?

Dendritic cell

Describe the process of hair formation, and list several factors that may influence (a) growth cycles and (b) hair texture.

Each follicle goes through growth cycles. In the regressive phase, the hair matrix cells die and the follicle base and hair bulb shrivel somewhat, dragging the hair papilla upward to abut the region of the follicle that does not regress. The follicle enters a resting phase for one to three months. The cycling part of the follicle regenerates and the matrix proliferates again and forms a new hair to replace the old one that has fallen out or will be pushed out by the new hair.

The rule of nines is helpful clinically in

Estimating the extent of a burn

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

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

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 not occur. Third-degree burns destroy the entire depth of skin and regeneration is not possible. Infection and loss of body fluid and proteins are problematic.

Distinguish clearly between first-, second-, and third-degree burns.

First- only the epidermis is damaged. Second- injure the epidermis and the upper regions of the dermis. (first and second are partial-thickness burns) Third- involve the entire thickness of the skin.

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

Flexure lines

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.

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

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

Which is not a true statement about the papillary layer of the dermis?

It is most responsible for the toughness of the skin.

What color does carotene impart to the skin?

It is the yellow to orange pigment most obvious in the palms and soles, where the stratum corneum is thickest, and most intense when large amounts of carotene-rich foods are eaten.

Which alteration in skin color may indicate a liver disorder?

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

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

Keratin

Which epidermal cell type is most numerous?

Keratinocyte

Which epidermal cells are also called prickle cells? Which contain keratohyaline and lamellar granules?

Keratinocytes. Keratinocytes in the stratum granulosum.

What change in the skin leads to cold intolerance in the elderly?

Loss of subcutaneous fat, common in the elderly, leads to cold intolerance seen in this group of people.

Sebum

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

Is a bald man really hairless? Explain.

No, the follicular growth cycles become so short that many hairs never even emerge from their follicles before shedding.

Which cutaneous glands are associated with hair follicles?

Sebaceous glands and apocrine glands are associated with the hair follicles.

Which of the following is not an epidermal derivative?

Sensory receptor

Given that epithelia are avascular, which layer would you expect to have the best-nourished cells?

Stratum basale.

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 bone synthesis.

What is the role of an arrector pili muscle?

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

Why does skin wrinkle and what factors accelerate the wrinkling process?

The decreasing elasticity of the skin, along with the loss of subcutaneous tissue, inevitably leads to wrinkling. Old age, UVA and UVB rays.

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

The dermis

Which epidermal cells play a role in body immunity?

The epidermal dendritic cells

What is the function of the hair papilla?

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

A common belief is that having your hair cut makes it become thicker. Explain why this belief is not true.

The hair that gets cut is already dead. Cutting the hair does not change the color or shape of the hair follicle.

Why are nails so hard?

The keratin they contain is the hard keratin variety.

What chemicals produced in the skin help provide barriers to bacteria? List at least three and explain how the chemicals are protective.

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

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

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

Which layer of the dermis is responsible for producing fingerprint patterns?

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

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.

How does the skin contribute to body metabolism?

The skin carries out chemical conversions that supplement some of the protective conversions carried out by the liver, convert some chemicals into carcinogens, activate some steroid hormones, and synthesize the vitamin D precursor.

Why are the desmosomes connecting the keratinocytes so important?

The skin is subjected to a lot of abrasion. Desmosomes, which are connecting junctions, help hold the cells together during stress.

The stratum basale is also called the stratum germinativium, 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.

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

The third pigment contained in red blood cells found in blood vessels of the dermis.

Why is having your hair cut painless?

There are no nerves in a hair

How does UV radiation contribute to skin wrinkles?

UV radiation degrades collagen and leads to loss of skin elasticity and water-holding capacity.

What is the source of vernix caseosa that covers the skin of the newborn baby?

Vernix caseosa is a product of the sebaceous glands.