Mastering Chapter 5 Homework

dermis (Although layers B and C can be distinguished based on their structural components, they form a continuous layer of the skin termed the dermis)

subcutaneous (The hypodermis ("under the skin") layer is also referred to as the subcutaneous region.)

to supply cells to replace those lost from the epidermis

Structures A, B, C, and D are located in the dermis (Each of the labeled structures is located within the dermal layer of the skin.)

A; holocrine ( Structure A is a sebaceous gland that secretes oily materials by complete rupture of the gland cells.)

to lubricate hair and prevent infection (Structure A produces sebum, an oily secretion that coats the hairs and prevents infectious agents from penetrating the hair shaft)

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keratinocytes (Keratinocytes are the primary cells that form the stratified layers of the epidermis)

d (Cells migrate upwards through the epidermis after being generated by mitosis in the stratum basale.)

melanocyte (Melanocytes within the stratum basale produce the pigment melanin, which is deposited within the deeper layers of the epidermis)

a dermal papilla (Dermal papillae are projections of the dermis that form indentations in the overlying epidermis.)

a

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reticular layer (The reticular layer is one of two layers of connective tissue that form the dermis of thin and thick skin.)

Tactile cells anchor the skin to the underlying structures of 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.)

stratum basale (10−25% of the cells in the stratum basale are melanin producing cells called melanocytes. Their branching processes extend among the surrounding cells, reaching well into the more superficial stratum spinosum layer.)

stratum basale (The stratum basale is the deepest layer of the epidermis and consists of one layer of actively mitotic stem cells. The stem cells in this layer generate the cells that will migrate to the more superficial layers: spinosum, granulosum, and corneum.)

pain receptors (Pain receptors formed by free nerve endings are found deep to the epidermis in the papillary layer of the dermis.)

melanin (Melanin is the only one of the three pigments (melanin, carotene, and hemoglobin) that contribute to skin color that is actually produced in the skin itself. Melanin protects the DNA of skin cells from UV radiation by absorbing the rays and dissipating the energy as heat.)

the reticular layer (The thicker, deeper layer of the dermis, called the reticular dermis, is named for its network of collagen fibers. These collagen fibers run in various planes, but most run parallel to the skin surface. Separations, or less dense regions, between these bundles form cleavage (tension) lines in the skin.)

scalp (The skin of scalp has hair, which gives it added protection from the damaging ultraviolet rays of the sun.)

False (The nail matrix is the thickened proximal portion of the nail bed responsible for nail growth. The cuticle is the part of the proximal skin fold, or nail fold, that projects onto the nail body.)

ceruminous glands (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.)

protection from 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.)

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 produce a more viscous secretion that is enriched with fats and proteins.)

sebaceous glands (Sebaceous glands secrete an oily substance called sebum. Sebum softens and lubricates the hair and skin, slows water loss from the skin when external humidity is low, and has bactericidal properties.)

thermoregulation (Sweat is used for thermoregulation. As sweat is released onto the surface of the epidermis, heat from the body is conducted into the water. Water is a better conductor of heat than air is. As the sweat evaporates, the heat from the body dissipates into the environment.)

melanoma (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.)

False (The single most important risk factor for skin cancer is overexposure to the UV radiation in sunlight and tanning beds. 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." Tanning beds use the same types of UV radiation found in natural sunlight, often at even higher intensities, to stimulate melanin production.)

asymmetry (Cancerous growths exhibit asymmetry. Benign growths exhibit symmetry, regular borders, uniform coloration, and they are usually less than 6 mm in diameter.)

second-degree burn (Second-degree burns injure the epidermis and the superficial region of the dermis. Symptoms mimic those of first-degree burns, but blisters also appear.)

border regularity (Border irregularity would be a sign of melanoma, especially if you were to see rough or notched edges.)

Inflammation causes increased blood flow.

destruction of underlying pain receptors

c (Structure C is an eccrine gland, the most abundant type of sweat (sudoriferous) gland.)

detection of pressure stimulus (Structure B is a lamellar (Pacinian) corpuscle that responds to cutaneous contacts involving deep pressure.)

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, which is transported via the blood to the liver and kidneys, where it is converted into active vitamin D.)

apocrine gland: thermoregulation (While the function of the apocrine cells is not well understood, they do not provide much assistance in thermoregulation because of their location.)