Final answer:
The transverse plane is perpendicular to the long axis of the body and divides it into upper and lower portions, known as cross sections.
Step-by-step explanation:
The sectional plane oriented perpendicularly to the long axis of the body is the transverse plane. This planar orientation is horizontal and divides the body or organ into upper and lower portions, producing what are known as cross sections. If this cut is made at an angle rather than perfectly horizontal, it is then referred to as an oblique plane. In the context of anatomical directional terms, the transverse plane is different from the midsagittal plane, which divides the body into equal left and right halves, and the frontal plane, also known as the coronal plane, which divides the body into anterior and posterior portions.