Chapter 5 Homework Quiz
|T/F: The biggest risk factor for the development of skin cancer is excessive exposure to ultraviolet radiation from sunlight.||True|
The single most important risk factor for skin cancer is overexposure to the UV radiation in sunlight. UV radiation damages DNA bases and appears to disable tumor suppressor genes, leading to the formation of cancerous cells. There is no such thing as a “healthy tan.”
|Transformed cells within labeled layer C (spinosum) give rise to which form of cell cancer?|
squamous cell carcinoma
basal cell carcinoma
|squamous cell carcinoma|
Abnormally growing cells within the stratum spinosum result in squamous cell carcinoma. Note that the spinosum is the region of keratinocyte “flattening,” hence the term squamous cell.
|Which structure is a type of cutaneous sensory receptor?||Structure B is a pacinian corpuscle, one of several structural and functional types of cutaneous sensory receptors.|
|Which of the following is NOT a layer of the epidermis?|
There isn’t a stratum reticulum. The epidermis of thick skin consists of 5 layers. From deep to superficial, these layers are stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. (Study tip: try the mnemonic BSGLC–Betty’s Skin Glows Like Candles) Note: thin skin lacks the stratum lucidum; thus, it consists of only the four major layers.
|Which of the following statements is INCORRECT?|
Keratinocytes produce a fibrous protein to protect the epidermis.
Tactile cells anchor the skin to the body.
Langerhans cells activate the immune system.
Melanin provides protection against ultraviolet (UV) radiation.
|Tactile cells anchor the skin to the body.|
This is the incorrect statement. Tactile cells, in conjunction with their sensory nerve endings, function as touch receptors. The hypodermis, not tactile cells anchors skin to the body.
|Which is the most common type of skin cancer?|
basal cell carcinoma
squamous cell carcinoma
|basal cell carcinoma|
Basal cell carcinoma is the least malignant and most common skin cancer, accounting for nearly 80% of all skin cancers. The cancer lesions appear most often in sun exposed areas of the face.
|Which of the following represents a difference between eccrine sweat glands and apocrine sweat glands?|
Eccrine sweat glands begin to function at puberty, while apocrine sweat glands function throughout life.
|The secretions of apocrine sweat glands contain more fat and protein than do the secretions of eccrine sweat glands.|
Compared to the watery secretions of eccrine glands, apocrine sweat glands have secretions that are enriched with fats and proteins.
|T/F: Melanin protects skin cell DNA from the damaging effects of ultraviolet (UV) radiation.||True|
Melanin absorbs and dissipates the harmful UV rays that can damage the DNA of viable skin cells.
|T/F: In the presence of sunlight, modified cholesterol is converted into Vitamin D precursors in the skin.||True|
The skin is a “chemical factory”, carrying out a variety of chemical reactions. An example is the synthesis of a vitamin D precursor (cholecalciferol) in the presence of ultraviolet (UV) radiation from sunlight.
|Which layer(s) of the skin is(are) damaged in a second-degree burn?|
The epidermis and the superficial region of the dermis are damaged.
|The epidermis and the superficial region of the dermis are damaged.|
Second-degree burns result in damage to the epidermis and the superficial region of the dermis.
|Cell division would be most common amongst cells in which of the labeled layers?||D|
Cells migrate upwards through the epidermis after being generated by mitosis in the stratum basale.
|Earwax is made by ________.|
Ceruminous glands are modified apocrine sweat glands found in the lining of the external ear canal. Their secretion mixes with sebum produced by nearby sebaceous glands to form a sticky, bitter substance called cerumen, or earwax, which is thought to deter insects and block entry of foreign material.
|A cancerous growth on the skin will likely exhibit ________.|
a size smaller than 6 mm
Cancerous growths exhibit asymmetry. Benign growths exhibit symmetry, regular borders, uniform coloration, and they are usually less than 6 mm in diameter.
|T/F: Hair and nails are made primarily of calcium.||False|
The primary component of hair and nails is hard keratin (not calcium), produced by keratinocytes.
|T/F: Our skin helps us to regulate our body temperature.||True|
Sweat glands secrete water (sweat) onto the surface of skin, which removes body heat as it evaporates. By dilating cutaneous blood vessels, blood flow to the skin is increased, which increases heat loss. By constricting blood vessels in the skin, the body decreases blood flow to the skin and thereby lowers heat loss.
|The skin consists of two main regions. From deep to superficial they are the ________.|
dermis and epidermis
|dermis and epidermis|
The skin is composed of two distinct regions, the (superficial) epidermis and the (deep) underlying dermis. Strictly speaking, the hypodermis is not part of the skin, but shares some of its protective functions.
|Layers B and C collectively form the ______.|
Although layers B and C can be distinguished based on their structural components, they form a continuous layer of the skin termed the dermis.
|Sam is so cold that he has “goose bumps.” What causes goose bumps?|
arrector pili muscles pulling hair follicles into an upright position
|arrector pili muscles pulling hair follicles into an upright position|
Most hair follicles approach the skin surface at a slight angle. The arrector pili muscle is attached to the follicle in such a way that its contraction pulls the follicle into an upright position and dimples the skin surface, producing goose bumps in response to cold external temperature or fear.
|Sweat is secreted by ________.|
Sudoriferous glands, which include eccrine and apocrine sweat glands, produce sweat.
|Which of the following is a metabolic function of skin?|
body temperature regulation
|synthesis of a vitamin D precursor|
Yes, this is a function of the skin carried out by chemical reactions in the skin. When sunlight bombards the skin, modified cholesterol molecules are converted to a vitamin D precursor (called cholecalciferol), which is transported via the blood to the liver and kidneys where it is converted into a hormone called calcitriol, or active vitamin D.
|Which labeled structure produces an oily secretion?||Structure A produces sebum, an oily secretion.|
|Which structures of the dermis give rise to friction ridges (fingerprints)?|
Dermal ridges cause the overlying epidermis to form epidermal ridges. Collectively these ridges are called friction ridges.
|Which of the following best explains the fact that eyebrows do not grow as long as the hair on the head?|
The hair follicles of the eyebrows are not responsive to androgens; hair follicles in the scalp are responsive to androgens.
|The hair follicles of the eyebrows are active for only a few months before becoming inactive; the hair follicles in the scalp are active for years before becoming inactive.|
The hair follicles in the scalp remain active for up to ten years, while those of the eyebrow are only active for up to four months, before becoming inactive.
|The hypodermis is distinguished by an abundance of ______.|
The hypodermis (D) consists mainly of adipose tissue.
|Which of the following does NOT protect the skin from bacteria?|
|the temperature of the skin|
The temperature of the skin does not protect the skin against bacteria. In fact, the temperature of the skin is ideal for many types of bacteria.
|Which stratum of the epidermis is responsible for regenerating the more superficial layers?|
The stratum basale is the deepest layer of the epidermis and consists of one layer of actively mitotic stem cells. Some of the newly formed cells become part of (regenerate) the more superficial layers: spinosum, granulosum, and corneum.
|The most dangerous type of skin cancer is ________.|
Melanoma, cancer of melanocytes, is the most dangerous skin cancer because it is highly metastatic and resistant to chemotherapy. These cancers appear spontaneously, and about one-third develop from preexisting moles.
|Sebum does NOT ________.|
slow water loss from the skin during low humidity conditions
|protect the skin from the damaging effects of UV radiation|
This is false; it is melanin (not sebum) that protects the skin from the damaging effects of UV radiation. Sebum serves as a lubricant, an antibacterial agent, and protects against water loss in low humidity conditions.
|The ________ is a thin translucent band found only in thick skin.|
The stratum lucidum, or clear layer, visible only in thick skin, is a thin, translucent band found just above the stratum granulosum.
|What is the role of the hair matrix?|
The hair matrix produces hair.
|The hair matrix produces hair.|
The hair matrix is the actively dividing area of the hair bulb that produces hair.