Odd One Out — Pupil, Iris, and Cornea are parts of the human eye; Medulla is not. Identify the odd term and explain the anatomical distinction.

Introduction / Context:
Anatomical grouping problems ask you to recognize which term does not belong to a stated organ system. Here three terms belong to the eye; one belongs to the brainstem.

Given Data / Assumptions:

• Pupil: the variable opening in the iris controlling light entry.
• Iris: pigmented ring controlling pupil size.
• Cornea: transparent, outermost refractive surface of the eye.
• Medulla: medulla oblongata, part of the brainstem.

Concept / Approach:
Identify organ association for each term. If three map to the eye and one to the central nervous system, the latter is the outlier.

Step-by-Step Solution:
Map Pupil → Eye.Map Iris → Eye.Map Cornea → Eye.Map Medulla → Brainstem (not eye).

Verification / Alternative check:
Functional check: the first three govern light entry/refraction; the medulla regulates autonomic functions (breathing, heart rate), unrelated to ocular anatomy.

Why Other Options Are Wrong:

• Pupil: ocular structure.
• Iris: ocular structure.
• Cornea: ocular structure.

Common Pitfalls:
Confusing “medulla” with “medulla of hair” or “renal medulla.” In common biomedical usage without qualifier, medulla refers to the brainstem region.

Final Answer:
Medulla