• Ossification

• Intramembranous-found in the flat bones of the face
  • Mesenchymal cells cluster and form strands
  • Strands are cemented in a uniform network. Which is known as osteoid
  • Calcium salts are deposited; osteoid is converted to bone
  • Trabeculae are formed and make cancellous bone with open spaces known as marrow cavities
  • Periosteum forms on the inner and outer surfaces of the ossification centers
  • Surface bone becomes compact bone
• Endochondral-primary type of ossification In the human

Innervation of the Pharynx

• The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
• The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.

• The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
• The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).

Superior Constrictor Muscle

• Origin: Hamulus, pterygo-mandibular raphe, and mylohyoid line of the mandible.
• Insertion: Median raphe of the pharynx.
• Nerve Supply: Vagus nerve via the pharyngeal plexus.
• Arterial Supply: Ascending pharyngeal artery, ascending palatine artery, tonsillar branch of the facial artery, and dorsal branch of the lingual artery.
• Action: Constricts the wall of the pharynx during swallowing.

Nerve Supply of the Muscles of the Orbit (pp. 715-6)

• Three cranial nerves supply the muscles of the eyeball; the oculomotor (CN III), trochlear (CN IV) and abducent (CN IV) nerves.
• All three enter the orbit via the superior orbital fissure.

• The trochlear nerve supplies the superior oblique muscle.
• The abducent nerve supplies the lateral rectus muscle.
• The oculomotor nerve supplies everything else.

• A mnemonic that is used is this formula for this strange sulfate: SO₄(LR₆)₃

Geniohyoid Muscle

• Origin: Inferior genial tubercles of the mandible.
• Insertion: Anterior surface of the body of the hyoid bone.
• Nerve Supply: Branch of C1 through the hypoglossal nerve (CN XII).
• Arterial Supply: Sublingual branch of the lingual artery.
• Action: Elevates the hyoid bone and depresses the mandible.

The skull, the skeleton of the head, is the most complex bony structure in the body because it:

1. Encloses the brain, which is irregular in shape;
2. Houses the organs of special senses for seeing, hearing, tasting, and smelling; and
3. Surrounds the openings in to the digestive and respiratory tracts.

• In the anatomical position, the skull is oriented so that the inferior margin of the orbit (eye socket) and the superior margin of the external acoustic meatus (auditory canal) are horizontal. This is called the orbitomenial plane (Frankfort plane).

• The term cranium (L. skull) is sometimes used when referring to the skull without the mandible (lower jaw), but the cranium is often used when referring to the part of the skull containing the brain.
• The superior part is the box-like structure called the calvaria (cranial vault, brain case); the remainder of the cranium, including the maxilla (upper jaw), orbits (eyeball sockets) and nasal cavities, forms the facial skeleton.
• The term skullcap (calotte) refers to the superior part of the calvaria, which is removed during autopsies and dissections. The inferior aspect of the cranium is called the cranial base.