Which nerve innervates the rectus capitis posterior minor muscle?

It is innervated by the suboccipital nerve (n. suboccipitalis), which is the dorsal ramus of the first cervical spinal nerve (C1).

What happens during unilateral contraction of the rectus capitis posterior major?

Unilateral contraction of this muscle rotates the head toward the same side (ipsilaterally).

It allows for the rapid spread of purulent infection, which can easily extend to the eyelids and nose.

This group includes two muscles running from the vertebrae to the occipital bone, primarily serving as extensors:

Rectus capitis posterior minor (m. rectus capitis posterior minor). Originates from the posterior tubercle of the atlas (C1). Its fibers pass superiorly and insert into the medial part of the inferior nuchal line of the occipital bone. Its primary function is to extend the head. Like most muscles in this group, it is innervated by the suboccipital nerve (n. suboccipitalis, C1 segment).
Rectus capitis posterior major (m. rectus capitis posterior major). Originates inferiorly from the spinous process of the axis (C2). It inserts onto the occipital bone just below the inferior nuchal line (linea nuchae). Bilateral contraction extends the head, while unilateral contraction rotates the head toward the same side.

The oblique muscles lie at an angle to the midline axis and play an active role in complex movements of the craniovertebral junction:

Obliquus capitis superior (m. obliquus capitis superior). Originates from the transverse process of the atlas. Its fibers course superiorly and insert into the occipital bone between the superior and inferior nuchal lines.
Obliquus capitis inferior (m. obliquus capitis inferior). Unlike the superior oblique, it connects two adjacent vertebrae: it originates from the spinous process of the axis and inserts into the transverse process of the atlas. The primary function of this muscle is head rotation.

Uninterrupted function of the suboccipital muscle group requires an adequate arterial blood supply. Two main vessels supply this area:

When studying the anatomy of the head and neck, it is important to keep several critical structures and spaces in mind:

Subaponeurotic space of the scalp carries clinical significance. If infection enters this space, it can spread rapidly, reaching the eyelids and nose.
Facial nerve (n. facialis). Damage to this nerve causes pronounced facial asymmetry. A hallmark symptom is lagophthalmos—the inability to completely close the eyelids due to paralysis of the orbicularis oculi muscle (m. orbicularis oculi).
Parotid duct. Along its course, it pierces the buccinator muscle (m. buccinator) and opens into the oral vestibule precisely opposite the upper second molar.