Chpater 5 PLQs

This layer of epidermis is composed of a single row of cuboidal or columnar keratinocytes.

Stratum basale

This layer of the epidermis contains layers of flattened keratinocytes that are going through apoptosis.

Stratum granulosum

Describe how fingerprints are formed and what they are used for.

The ducts of sweat glands open on the tops of the epidermal ridges as sweat pores, the sweat and ridges form fingerprints (or footprints) on touching a smooth object. The epidermal ridge pattern is in part genetically determined and is unique for each individual. Normally, the ridge pattern does not change during life, except to enlarge, and thus can serve as the basis for identification.

The hair root plexus functions to...

assist hair in touch perception.

The process of keratinization involves...

cells accumulating a tough fibrous protein that helps protect the skin.

"Goose bumps" are caused by...

contraction of arrector pili muscles.

You stepped on a nail. List the sequential layers (or strata) of the epidermis that the nail penetrated through to finally reach the dermis.

corneum, lucidum, granulosom, spinosum, basale

Keratin...

is a protein.

The stratum lucidum...

is present only in thick skin.

Albinism is the inherited inability to produce...

melanin.

In the diagram of a hair root shown, where is the cuticle of the hair?

C

In the diagram of skin shown below, where is the sebaceous gland?

C

In the diagram, which is the external root sheath?

C

In the figure of a sagittal section of a fingernail shown, where is the lunula?

C

Which structure in the figure detects touch sensations?

C

During embryonic development, which of the following accessory structures of the skin develops as an outgrowth of epithelial cells from the sides of a hair follicle? A. Eccrine sweat glands B. Apocrine sweat glands C. Sebaceous glands D. Fingernails E. Arrector pili muscles

C. Sebaceous glands

Which of the following structures found in the skin plays an important role in thermoregulation? A. Merkel cells B. Sebaceous glands C. Sweat glands D. Nails E. Fingerprints

C. Sweat glands

In the diagram, which is the papilla of the hair?

E

In the figure of a sagittal section of a fingernail shown below, where is the nail matrix?

E

In the photomicrograph of a portion of thick skin shown below, which layer is the stratum basale?

E

Which letter is pointing to the subcutaneous layer of the skin in the figure?

E

Characteristics of thick skin include: A. Found in the palms, soles of the feet and fingertips. B. Does not contain hair follicles. C. Contains more sweat glands than thin skin. D. Contain epidermal ridges. E. All of these choices are correct.

E. All of these choices are correct.

Which of the following terms refers to an inflammation of the skin characterized by patches of redness, blistering, and extreme itching? A. Papule B. Laceration C. Keratosis D. Frostbite E. Eczema

E. Eczema

Which of the following terms refers to persistent redness of the skin such as seen in patients with inflammation, infection or heat exposure? A. Hirsutism B. Pallor C. Jaundice D. Androgenic alopecia E. Erythema

E. Erythema

Which of the following chemicals does NOT contribute to the color of human skin? A. Carotene B. Hemoglobin C. Pheomelanin D. Eumelanin E. Melatonin

E. Melatonin

Which of the following structures found in the skin help prevent water loss and inhibit bacterial growth on the surface of the skin? A. Arrector pili B. Lunula C. Sweat glands D. Hair follicles E. Oil glands

E. Oil glands

This is another name for the subcutaneous layer.

Hypodermis

In the diagram, which layer is the stratum corneum?

I

Which structures are dermal papillae?

I

List and briefly describe the major functions of the skin.

1. Thermoregulation is the homeostatic regulation of body temperature. The skin contributes to thermoregulation in two ways: by liberating sweat at its surface and by adjusting the flow of blood in the dermis. 2. The dermis houses an extensive network of blood vessels that carry 8-10% of the total blood flow in a resting adult. For this rea- son, the skin acts as a blood reservoir. 3. The skin provides protection to the body in various ways. Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes. Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration; they also retard entry of water across the skin surface during showers and swims. The oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals (substances that kill bacteria). The acidic pH of perspiration retards the growth of some microbes. The pigment melanin helps shield against the damaging effects of ultraviolet light. Two types of cells carry out protective functions that are immunological in nature. Epidermal Langerhans cells alert the immune system to the presence of potentially harmful microbial invaders by recognizing and processing them, and macrophages in the dermis phagocytize bacteria and viruses that manage to bypass the Langerhans cells of the epidermis. 4. Cutaneous sensations are sensations that arise in the skin, including tactile sensations—touch, pressure, vibration, and tickling—as well as thermal sensations such as warmth and coolness. Another cutaneous sensation, pain, usually is an indication of impending or actual tissue damage. 5.The skin normally has a small role in excretion, the elimination of substances from the body, and absorption, the passage of materials from the external environment into body cells. 6. Synthesis of vitamin D requires activation of a precursor mole- cule in the skin by ultraviolet (UV) rays in sunlight. Enzymes in the liver and kidneys then modify the activated molecule, finally producing calcitriol, the most active form of vitamin D. Calcitriol is a hormone that aids in the absorption of calcium from foods in the gastrointestinal tract into the blood.

In the diagram of skin shown below, which labeled structure generates fingerprints?

A

In the figure of a sagittal section of a fingernail shown below, where is the nail root?

A

Which structure in the figure produces a protein that helps protect the skin and underlying tissues from heat, microbes and chemicals?

A

Which structures in the figure are sensitive to warmth, coolness and itching?

A

John has just been brought into the emergency room following a fiery explosion at a chemical plant. He is diagnosed with third degree burns over the anterior surfaces of his arms and trunk. What specific structural damage has occurred to his skin? What risks to John's life have resulted from this damage?

A third-degree burn or full-thickness burn destroys the epidermis, dermis, and subcutaneous layer. Most skin functions are lost. Such burns vary in appearance from marble-white to mahogany colored to charred, dry wounds. There is marked edema, and the burned region is numb because sensory nerve endings have been de- stroyed. Regeneration occurs slowly, and much granulation tissue forms before being covered by epithelium. Skin grafting may be required to promote healing and to minimize scarring. The injury to the skin tissues directly in contact with the damaging agent is the local effect of a burn. Generally, however, the systemic effects of a major burn are a greater threat to life. The systemic effects of a burn may include (1) a large loss of water, plasma, and plasma proteins, which causes shock; (2) bacterial infection; (3) reduced circu- lation of blood; (4) decreased production of urine; and (5) diminished immune responses.

Which of the following terms refers to a Hardened and thickened area of skin resulting from persistent pressure and friction? A. Callus B. Blister C. Wart D. Papule E. Fever blister

A. Callus

Which of the following conditions is characterized by excessive body hair caused by tumors in adrenal glands, testes or ovaries? A. Hirsutism B. Pallor C. Jaundice D. Androgenic alopecia E. erythema

A. Hirsutism

In the diagram of a hair root shown, where is the cortex?

B

In the diagram, which is the internal root sheath?

B

In the figure of a sagittal section of a fingernail shown, where is the eponychium (cuticle)?

B

In the photomicrograph of a portion of thick skin shown below, which layer is only seen in thick skin?

B

Which of the following skin disorders involves inflammation of sebaceous glands caused by bacteria which thrive in the lipid-rich sebum? A. Alopecia B. Acne C. Vitiligo D. Pressure ulcer E. Eczema

B. Acne

Which of the primary germ layers of the embryo does the epidermis of the skin develop from? A. Endoderm B. Ectoderm C. Mesoderm D. All of these choices are correct. E. Both endoderm and ectoderm.

B. Ectoderm

Which of the following terms refers to reddened, elevated, and itchy patches of skin commonly caused by emotional stress, physical trauma, or certain food allergies? A. Wart B. Hives C. Papule D. Cyst E. Eczema

B. Hives

Which of the following terms refers to paleness of the skin such as seen in patients with shock or anemia? A. Hirsutism B. Pallor C. Jaundice D. Androgenic alopecia E. Erythema

B. Pallor

Which of the following best describes the events occurring at point A in the diagram of deep wound healing shown below?

Blood clot is forming.

Which of the labeled cells in the diagram of deep wound healing shown below has phagocytic properties?

Both E & F

Which of the following best describes events that lead to the tanning of skin that occurs after exposure of the skin to the sun's UV radiation? A. UV radiation stimulates increased numbers of melanocytes in the skin. B. UV radiation stimulates increased numbers of keratinocytes in the skin. C. UV radiation stimulates increased production of melanin by melanosomes. D. UV radiation inactivates tyrosinase activity in melanocytes. E. UV radiation stimulates increased production of carotenes by keratinocytes.

C. UV radiation stimulates increased production of melanin by melanosomes.

Briefly describe the steps in epidermal wound healing.

Common types of epidermal wounds include abrasions, in which a portion of skin has been scraped away, and minor burns. In response to an epidermal injury, basal cells of the epidermis surrounding the wound break contact with the basement membrane. The cells then enlarge and migrate across the wound. The cells appear to migrate as a sheet until advancing cells from opposite sides of the wound meet. When epidermal cells encounter one another, they stop migrating due to a cellular response called contact inhibition. Migration of the epidermal cells stops completely when each is finally in contact with other epidermal cells on all sides. As the basal epidermal cells migrate, a hormone called epidermal growth factor stimulates basal stem cells to divide and replace the ones that have moved into the wound. The relocated basal epidermal cells divide to build new strata, thus thickening the new epidermis

In the diagram of skin shown below, where is the arrector pili muscle?

D

In the photomicrograph of a portion of thick skin shown below, which layer is the stratum spinosum?

D

Meissner's corpuscle would be found in which layer of the skin shown in the figure?

D

Which structure in the figure produces a pigment that contributes to skin color and absorbs UV radiation?

D

Which of the following terms refers to an irregular tear of the skin? A. Abrasion B. Papule C. Keloid D. Laceration E. Cyst

D. Laceration

Which condition results from androgens inhibiting hair growth in genetically predisposed adults? A. Hirsutism B. Pallor C. Jaundice D. Male-pattern baldness E. Erythema

D. Male-pattern baldness

Which of the following is a common characteristic of thin skin? A. Hairless. B. Contains a stratum lucidum. C. High density of sensory receptors. D. Presence of sebaceous glands. E. Contains epidermal ridges.

D. Presence of sebaceous glands.

Briefly describe the steps in deep wound healing.

Deep wound healing occurs when an injury extends to the dermis and subcutaneous layer. Because multiple tissue layers must be repaired, the healing process is more complex than in epidermal wound healing. In addition, because scar tissue is formed, the healed tissue loses some of its normal function. Deep wound healing occurs in four phases: an inflammatory phase, a migratory phase, a proliferative phase, and a maturation phase. During the inflammatory phase, a blood clot forms in the wound and loosely unites the wound edges. As its name implies, this phase of deep wound healing involves inflammation, a vascular and cellular response that helps eliminate microbes, foreign material, and dying tissue in preparation for repair. The vasodilation and increased permeability of blood vessels associated with inflammation enhance delivery of helpful cells. These include phagocytic white blood cells called neutrophils; monocytes, which develop into macrophages thatphagocytize microbes; and mesenchymal cells, which develop into fibroblasts. The three phases that follow do the work of repairing the wound. In the migratory phase, the clot becomes a scab, and epithelial cells migrate beneath the scab to bridge the wound. Fibroblasts migrate along fibrin threads and begin synthesizing scar tissue (collagen fibers and glycoproteins), and damaged blood vessels begin to regrow. During this phase, the tissue filling the wound is called granulation tissue. The proliferative phase is characterized by extensive growth of epithelial cells beneath the scab, deposition by fibroblasts of collagen fibers in random patterns, and continued growth of blood vessels. Finally, during the maturation phase, the scab sloughs off once the epidermis has been restored to normal thickness. Collagen fibers become more organized, fibroblasts decrease in number, and blood vessels are restored to normal.

This layer of the skin is composed mainly of dense irregular connective tissue containing collagen and elastic fibers.

Dermis

This type of exocrine gland is a simple, coiled tubular gland that is found throughout almost the entirety of the skin.

Eccrine sweat gland

This layer of the skin is composed of a keratinized stratified squamous epithelium.

Epidermis

Which of the following best describes the events occurring at point B in the diagram of deep wound healing shown below?

Epithelium is migrating across wound.

In the diagram of a hair root shown, where is the dermal root sheath?

F

In the diagram of skin shown below, where is the apocrine sweat gland?

F

In the diagram, which is a melanocyte?

F

Which structure in the figure is a receptor sensitive to pressure?

F

In the diagram, which is the hair matrix?

G

In the diagram, which layer is the stratum granulosum?

G

In the diagram, which structure is directly destroyed by electrolysis?

G

In the figure of a sagittal section of a fingernail shown, where is the hyponychium (nail bed)?

G

Which structure is an eccrine sweat gland?

G

In the diagram of skin shown below, where is the reticular region of the dermis?

H

Which condition is due to a buildup of bilirubin pigment in the skin?

Jaundice

In this type of scar, the scar tissue extends beyond the boundary of the injury into normal tissue.

Keloid scar

This epidermal cell has a role in immunity and disease resistance.

Langerhans cells

This is fine nonpigmented hair that covers the body of the fetus.

Lanugo

This pigment secreted by specialized cells in the skin is capable of absorbing ultraviolet light.

Melanin

Describe the structure and function of arrector pili.

Sebaceous (oil) glands and a bundle of smooth muscle cells are associated with hairs. The smooth muscle is the arrector pili. It extends from the superficial dermis of the skin to the dermal root sheath around the side of the hair follicle. In its normal position, hair emerges at an angle to the surface of the skin. Under physiological or emotional stress, such as cold or fright, autonomic nerve endings stimulate the arrector pili muscles to contract, which pulls the hair shafts perpendicular to the skin surface. This action causes "goose bumps" or "gooseflesh" because the skin around the shaft forms slight elevations.

This type of exocrine gland is a simple, branched acinar gland connected to a hair follicle.

Sebaceous gland

This is a mixture of triglycerides, cholesterol, proteins and inorganic salts.

Sebum

Describe the structural characteristics of the epidermis that contribute to its ability to protect the surface of an animal.

The skin provides protection to the body in various ways. Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes. Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration; they also retard entry of water across the skin surface during showers and swims. The oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals (substances that kill bacteria). The acidic pH of perspiration retards the growth of some microbes. The pigment melanin helps shield against the damaging effects of ultraviolet light. Two types of cells carry out protective functions that are immunological in nature. Epidermal Langerhans cells alert the immune system to the presence of potentially harmful microbial invaders by recognizing and processing them, and macrophages in the dermis phagocytize bacteria and viruses that manage to bypass the Langerhans cells of the epidermis.

Constant exposure of skin to friction stimulates the formation of a callus, which is the thickening of the ________ of the epidermis.

stratum corneum