**Core Concept**
Buerger's disease, also known as thromboangiitis obliterans, is a rare disorder characterized by inflammation and clotting of blood vessels in the hands and feet. This condition is strongly associated with smoking and is more common in men.

**Why the Correct Answer is Right**
Buerger's disease primarily affects the small and medium-sized arteries, veins, and nerves of the extremities, particularly the legs and arms. The inflammation and clotting of these vessels lead to reduced blood flow, pain, and tissue damage. The pathophysiology involves an autoimmune response, with activated T-cells and macrophages contributing to the vascular damage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect because Buerger's disease can affect any vessel in the extremities, but it is not typically associated with the aorta or major arteries.

**Option B:** This option is incorrect because Buerger's disease is characterized by inflammation and clotting of both arteries and veins, but the exact involvement of capillaries is not a defining feature.

**Option C:** This option is incorrect because Buerger's disease affects the skin and subcutaneous tissues of the extremities, but it is not typically associated with the gastrointestinal tract or other internal organs.

**Clinical Pearl / High-Yield Fact**
Buerger's disease is strongly associated with smoking, and quitting smoking is the most effective way to slow the progression of the disease. Patients with Buerger's disease should be counseled on smoking cessation and managed with a multidisciplinary team.

**Correct Answer: A. The aorta or major arteries are not typically affected by Buerger's disease.**