Author Question: Leonard works in the agriculture industry and raises beef cattle. At 60 years of age, he has spent ... (Read 126 times)

leo leo · **on:** Jun 25, 2018

Leonard works in the agriculture industry and raises beef cattle. At 60 years of age, he has spent most of his life working outdoors harvesting hay and tending to his herds.

His wife was the first to notice a change in his skin. One day, after taking off his shirt, she noticed a significant change in the mole he had on his right shoulder. It not only was darker but was moist and appeared to have been bleeding at one point. Surrounding the mole, his skin was red. His wife remembered hearing stories of Leonard working on his father's farm, spending long hours out in the hot sun even though his father had gone into the barn to work during the hottest part of the day. She insisted him go to the family physician to have it examined.

Leonard's physician performed a biopsy on the lesion and told Leonard he suspected the growth may be malignant melanoma. What cells are affected in this form of skin cancer? How might his childhood exposures to the sun predispose him to this form of cancer?

How do UVA and UVB rays contribute to the process of oncogenesis in skin cells?

The mole on Leonard's shoulder was a nevocellular nevus. What are the cellular composition and appearance of this type of mole before it underwent malignant change?

Question 2

Which of the following facts accounts for the variation in skin tone that exists between individuals?

A)
Someone with dark skin has more melanocytes in his or her skin layers.
B)
Darker-skinned individuals have melanosomes that produce melanin faster.
C)
Dark skin is associated with spherical melanosomes, which produce and package pigment differently.
D)
Greater numbers of keratinocytes result in darker skin tone.

yasmina · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

Melanocytes are the cells affected in malignant melanoma. Sudden and intense bursts of sun exposure are associated with this form of cancer. A history of either three or more blistering sunburns or three or more outdoor jobs before the age of 20 increases the risk of developing malignant melanoma.

Cellular DNA readily absorbs UV radiation and is directly damaged as a result. UV radiation also reduces the number of Langerhans cells and hinders the immune functions of the skin. Normal immune function is thought to contribute to the destruction of cells with malignant potential. When immune cells are depleted, this protective mechanism is lost.

Nevocellular nevi are composed of melanocytes in the deepest layer of the epidermis. The structure of the melanocytes undergoes transformational change so that they become rounder and grow in clusters within the junction between the epidermis and dermis. The nevi have a uniform, pale to dark brown color. They are small in size and have regular, well-demarcated borders.

Answer to Question 2

Ans:
B

Feedback:

The amount of melanin in the keratinocytes determines a person's skin color. Dark-skinned and light-skinned people have the same amount of melanocytes. However, in dark-skinned people, larger melanosomes are produced and transferred to the keratinocyte individually. In light-skinned people, a number of smaller melanosomes are packaged together in a membrane and then transferred to the keratinocyte. The way the melanosomes are packaged is responsible for the pigmentation in darker-skinned persons. Darker-skinned people do not have more melanocytes than light-skinned people, but the production and packaging of pigment is different.