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1. Thin skin is hairy, lack dermal papillae and has more sebaceous glands and fewer sweat glands and sensory receptors. Thick skin is hairless, has many dermal papillae, and more sensory receptors.
2. The three phases of hair growth are anagen, catagen, and telogen. Anagen is the growth phase in which the cells in the root of the hair divides rapidly. A new hair is formed and pushes the club hair up the follicle and out. The hair grows about 10cm per year during this phase, and grows for about 2-6 years. Catagen is a transitional phase at the end of anagen which lasts about 2-3 weeks. Growth stops and the follicle shrinks about 1/6 of its normal length and attaches to the root of the hair, which forms what is known as a club hair. Telogen is the resting phase following catagen which lasts about 2-4 months. During this period, the hair growth remains dormant and attached to the follicle, and dermal papilla stays in a resting stage. After the telogen phase expires, the hair follicle re-enters the anagen phase.The dermal papilla and the base of the follicle join together again and a new hair begins to form.

Melanoma develops in melanocytes, and is caused by awry with melanocytes, mostly due to prolonged exposure to UV light. Symptoms can include a change in existing mole, or the spread of a new pigment or unusual looking growth on the skin. The 5-year survival rate for patients whose melanoma is detected before the tumor begins to spread to lymph nodes or other organs is about 98 percent. The survival rate is 62 percent when the disease reaches the lymph nodes, and 15 percent when the disease reaches distant organs. Treatments for melanoma include surgery, chemotherapy, biological therapy, and targeted therapy.