Musculoskeletal System
The head is positioned upon the superior portion of the vertebral column, attaching the skull upon C-1, (the atlas). The skeletal section of the head and neck forms the superior segment of the axial skeleton and comprises skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
- (a) cranium, (8 bones: frontal, 2-parietal, occipital, 2-temporal, sphenoid, ethmoid), and
- (b) facial bones, (14 bones: 2-zygomatic, 2-maxillary, 2-palatine, 2-nasal, 2-lacrimal, vomer, 2-inferior conchae, mandible).
As the fetus develops, the facial bones usually form into pairs, and then fuse together. As the cranium fuses, sutures are formed that resemble stitching between bone plates.
In a newborn, the junction of the parietal bones with the frontal and occipital bones, form the anterior (front) and posterior (back) fontanelle, or soft spots. The separation of the cranial bone plates at time of birth facilitate passage of the head of the fetus through the mother's birth canal, or pelvic girdle. The parietal bones, and occipital bone can overlap each other in the birth canal, and form the unusual looking "cone head" appearance in a newborn when delivered in a natural, or vaginal, delivery.
The occipital bone articulates with the atlas near the foramen magnum. The atlas articulates with the occipital condyle superiorly and the axis inferiorly. The spinal cord passes through the foramen magnum providing continuity for the central nervous system (CNS). Articulation of the neck includes: flexion, extension, (nodding yes), and rotation (shaking head no).
| Group | Name | Nerve | Function |
| facial expression | Epicranius: Frontalis and Occipitalis | facial nerve | eyebrows and scalp |
| facial expression | Orbicularis oris | facial nerve | closes lips |
| facial expression | Zygomaticus major | facial nerve | smiling |
| facial expression | Zygomaticus minor | facial nerve | smiling |
| facial expression | Levator labii superioris | facial nerve | upper lip |
| facial expression | Levator labii superioris alaeque nasi | facial nerve | upper lip |
| facial expression | Depressor labii inferioris | facial nerve | lower lip |
| facial expression | Depressor anguli oris | facial nerve | frowning |
| facial expression | Platysma | facial nerve | frowning (during fear or shock) |
| facial expression | Buccinator | facial nerve | cheeks |
| facial expression | Mentalis | facial nerve | chin |
| facial expression | Platysma | facial nerve | frowning |
| facial expression | Risorius | facial nerve | mouth angle |
| facial expression | Orbicularis oculi | facial nerve | closes eye |
| facial expression | Nasalis | facial nerve | flare nostrils |
| facial expression | Corrugator supercilli | facial nerve | eyebrow |
| facial expression | Levator palpebrae superioris | oculomotor nerve | upper eyelid |
| chewing – lower mandible | Masseter | Trigeminal nerve | closing and protruding mandible, |
| chewing – lower mandible | Temporalis | Trigeminal nerve | elevates and controls side to side movement of mandible |
| chewing – lower mandible | Medial pterygoid | Trigeminal nerve | elevates mandible, |
| chewing – lower mandible | Lateral pterygoid | Trigeminal nerve | protracts mandible, opens mouth. |
| tongue – extrinsic | Genioglossus | hypoglossal nerve | protraction, |
| tongue – extrinsic | Styloglossus | hypoglossal nerve | elevation and retraction, |
| tongue – extrinsic | Hyoglossis | hypoglossal nerve | depresses tongue |
| tongue – extrinsic | Palatoglossus | Pharyngeal plexus, pharyngeal branch of vagus nerve | elevates tongue while swallowing |
| oral cavity floor | Digastric | Trigeminal nerve and Facial nerve | hyoid and mandible movement |
| oral cavity floor | Stylohyoid | Facial nerve | elevates hyoid |
| oral cavity floor | Mylohyoid | Trigeminal nerve | hyoid and mandible movement |
| oral cavity floor | Geniohyoid | Cervical nerve C-1 | hyoid, tongue, and mandible movement |
| move head | Sternocleidomastoid | Accessory nerve | nodding and turning |
| move head | Semispinalis | dorsal rami of cervical nerves | extends head, supports turning |
| move head | Splenius capitis | dorsal rami of middle and lower cervical nerves | extend head, supports turning |
| move head | Longissimus capitis | dorsal rami of middle and lower cervical nerves | extends head, supports turning |
| move head | Rectus capitis posterior major | Suboccipital nerve C-1 | extends head |
| move head | Rectus capitis posterior minor | Suboccipital nerve C-1 | extends head |
Read more about this topic: Head And Neck
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