Which of the following is NOT a part of the digestive system?

The pituitary gland is not part of the digestive system; instead, it is an important endocrine gland located at the base of the brain. Its primary function is the regulation of various hormonal activities in the body, including growth, metabolism, and reproductive processes. Unlike the small intestine, rectum, and esophagus, which all play direct roles in the digestion and processing of food, the pituitary gland operates within the endocrine system and does not aid in the breakdown or absorption of nutrients. This distinction clarifies why the pituitary gland is not considered a component of the digestive system.