What part of the GI tract is primarily affected by ulcerative colitis?

Ulcerative colitis is an inflammatory bowel disease that primarily affects the large intestine (colon) and the rectum. It is characterized by inflammation and ulceration of the mucosal layer of the colon, leading to symptoms such as diarrhea, abdominal pain, and rectal bleeding. This condition specifically starts in the rectum and can extend in a continuous manner to involve other parts of the colon.

The focus on the large intestine and rectum is vital because these areas show the most significant pathology, including pseudopolyps and ulcers, leading to the typical clinical manifestations of the disease. In contrast, the other options represent parts of the gastrointestinal tract that are not primarily involved in ulcerative colitis, making the selection of the large intestine and rectum the most accurate choice. Understanding this specific involvement helps in both diagnosing and managing the condition effectively.