Human Anatomy, Part 2 - K. A. Diubenko, A. K. Kolomiitsev, Yu. B. Chaikovskyi 2008
Special Part
Nervous system, systema nervosum - Special Part
Brain - Embryogenesis of the brain - Rhomboid fossa
The Rhomboid fossa, fossa rhomboidea, is a diamond-shaped area formed by the posterior surface of the Medulla Oblongata and the Pons (Fig. 144). It is bounded superiorly by the superior cerebellar peduncles and inferiorly by the inferior cerebellar peduncles. Running from the superior to the inferior angle along the midline of the fossa is the median sulcus, sulcus medianus, which divides it into two symmetrical halves. Lateral to the median sulcus lies the medial eminence, eminentia medialis, which represents an accumulation of Gray matter. The medial eminence gradually tapers and, in its lower part, forms a triangle called the hypoglossal trigone, trigonum nervi hypoglossi, onto which the hypoglossal Nucleus projects. Lateral to it is the second triangle, the vagal trigone, trigonum nervi vagi, which contains the dorsal Nucleus of the Vagus nerve. Superiorly, the medial eminence features the facial colliculus, colliculus facialis, which contains the internal genu of the Facial Nerve ROOT looping around the abducens nucleus.
In the Regions of the lateral angles of the rhomboid fossa lies the vestibular area, area vestibularis, containing the nuclei of the Vestibulocochlear nerve. Fibers arise from these nuclei as medullary striae, striae medullares, which cross the rhomboid fossa transversely and divide it into superior and inferior parts.
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Fig. 144. Rhomboid fossa, fossa rhomboidea. PROJECTION OF THE nuclei onto the rhomboid fossa (diagram) after F. Kiss and J. Szentágothai.
Topography of the gray matter and projection of the nuclei onto the rhomboid fossa
During the Cytology/cytology/16.html">Early stages of Nervous system Embryogenesis, as the neural tube transitions from the Spinal Cord to the medulla oblongata, its posterior wall opens and unfolds to form the rhomboid fossa. Consequently, the posterior horns of the spinal cord's gray matter diverge laterally, and the somatosensory nuclei contained within them become positioned in the rhomboid fossa. The somatomotor nuclei of the anterior horns are situated medially, while the autonomic vegetative nuclei, which originate in the lateral horns of the spinal cord, are positioned in the rhomboid fossa between the sensory and motor nuclei as the neural tube unfolds. Thus, the gray matter nuclei in the rhomboid fossa are arranged in columns: the motor nuclei of Cranial Nerves X, IX, and VII lie in the medial Column near the midline, while the sensory nuclei of the cranial nerves are located in the lateral column (Fig. 144).
The nuclei of cranial nerves VI, VII, VIII, IX, X, XI, and XII lie within the gray matter of the medulla oblongata and pons of the rhomboid fossa; their projection onto the rhomboid fossa is as follows:
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n. Trigeminus (V) Trigeminal nerve (mixed) |
has four nuclei: - nucl. principalis n. trigemini*, principal sensory nucleus of trigeminal nerve (tactile sensation and pressure), located in the posterior part of the pons; - nucl. spinalis inferior n. trigemini, spinal trigeminal nucleus (pain and Temperature Sensation), extending down into the cervical spinal cord (up to the C4 segment); - nucl. mesencephalicus n. trigemini, mesencephalic trigeminal nucleus (proprioceptive), located lateral to the cerebral aqueduct. The above-mentioned nuclei are sensory; - nucl. motorius n. trigeminalis, the motor (somatomotor) nucleus of the trigeminal nerve (masticatory), located in the pons, medial to the sensory nucleus. |
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n. Abducens (VI) Abducens nerve (motor) |
has one motor nucleus: - nucl. n. abducentis, abducens nucleus. It is located within the loop of the facial nerve and corresponds to the facial colliculus. |
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n. Facialis (VII) Facial nerve (Intermediate) (mixed) |
has one motor nucleus: - nucl. n. facialis, located in the posterior part of the pons. The nerve fibers of this nucleus form a loop that creates the facial colliculus, colliculus facialis, in the rhomboid fossa. The intermediate nerve has three nuclei: - nucl. salivatorius superior, superior salivatory nucleus - autonomic (secretory), located in the reticular Formation of the pons, dorsal to the facial nerve nucleus; - lacrimal nucleus - nucl. lacrimalis, (secretory) parasympathetic; - nucl. tracti solitarii, solitary tract nucleus - sensory (shared with cranial nerves VII, IX, and X). |
* A 14 1.05.406. Nucleus principalis nervi trigemini - this term is preferred over nucleus ponti trigeminalis to distinguish it from the oral part of the spinal trigeminal nuclei, which are also found in the tegmentum pontis.
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n. Vestibulocochlearis (VIII) Vestibulocochlear nerve (sensory) |
has six nuclei: - four nuclei belong to the vestibular part of the nerve, vestibularis: nucl. vestibularis superior (Bechterew's), inferior (Roller's), medialis (Schwalbe's), lateralis (Deiters'); - two nuclei (auditory) belong to the cochlear part of the nerve, nucl. cochlearis anterior et posterior. These nuclei project onto the area vestibularis of the rhomboid fossa. |
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n. Glossopharyngeus (IX) Glossopharyngeal nerve (mixed) |
has three nuclei: - nucl. solitarius superior - sensory nucleus; - nucl. salivatorius inferior, inferior salivatory nucleus - autonomic (secretory); the Cells of this nucleus are located in the reticular formation of the medulla oblongata; - nucl. ambiguus - nucleus ambiguus (motor), shared with n. vagus and n. accessorius. |
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n. Vagus (X) Vagus nerve (mixed) |
has three nuclei: - nucl. solitarius, nucleus of the solitary tract - (sensory), located deep within the trigonum n. vagi; - nucl. dorsalis n. vagi - autonomic, located in the region of the vagal trigone; - nucl. ambiguus - motor, shared with The Nucleus of CN X, located in the formatio reticularis. |
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n. Accessorius (XI) Accessory nerve (motor) |
has two motor nuclei: - nucl. n. accessorii, which is located in the spinal cord; nucl. ambiguus is located in the medulla oblongata and is a continuation of the nuclei of cranial nerves X and IX; the fibers of this nucleus then join the vagus nerve. |
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n. Hypoglossus Hypoglossal nerve (motor) |
has one motor nucleus of the hypoglossal nerve: - nucl. nervi hypoglossi, located deep within the trigonum n. hypoglossi. |
Last update: 08/08/2026
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