From the upper angle to the lower angle longitudinally in the midline of the rhomboid fossa goes a groove called the median sulcus. It divides the fossa into the right and left half.

In transverse directions from both lateral corners to the midline, bundles of fibers pass which are known as the striae medullares. They divide the fossa into upper and lower triangular-shaped parts and at the same time also represent a border between the dorsal surfaces of the pons and medulla oblongata.

The superior triangle of the rhomboid fossa is formed by the pons. The inferior triangle - by the medulla oblongata and a small portion of the lower aspect of the dorsal surface of pons.

The rhomboid fossa can also be divided into the following three parts:

Upper part - formed by the superior triangle;
Intermediate part - represented by the striae medullares;
Lower part - formed by the inferior triangle.

On both sides, laterally from the median sulcus and parallel to it, goes another slightly convex groove known as the sulcus limitans. Along its course, at both ends, this sulcus contains two slight depressions:

Superior fovea - located above the striae medullares;
Inferior fovea - situated below the striae at the lower aspect of the sulcus limitans.

A longitudinal elevation - medial eminence - is located between the sulcus limitans and median sulcus along the entire length of the rhomboid fossa.

The surfaces of the lateral aspects of the rhomboid fossa at the beginning of the lateral recesses and laterally to the sulcus limitans are a bit elevated. These elevated sites are known as vestibular areas - they house the vestibular nuclei.

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Rhomboid fossa: main landmarks