Skull Anatomy and Muscles of Facial Expression

Comprehensive practice flashcards covering the anatomical structures, development, foramina, and muscles of expression associated with the human skull.

What are the two primary divisions of the skull (cranium)?

The neurocranium and the viscerocranium.

Which eight bones compose the neurocranium?

The sphenoid, occipital, frontal, ethmoid, two temporal bones, and two parietal bones.

Which four cranial bones are classified as pneumatized bones containing air spaces?

The frontal, temporal, sphenoid, and ethmoid bones.

What are the two anatomical sub-parts of the neurocranium?

The calvaria (skull cap) and the basicranium (cranial base).

What are the three singular (unpaired) bones that make up the viscerocranium?

The mandible, ethmoid, and vomer.

What six bones form the bilateral pairs of the viscerocranium?

The lacrimal, inferior nasal conchae, maxillae, palatine, nasal, and zygomatic bones.

Through which process of bone formation do the calvaria and some parts of the cranial base develop?

Intramembranous ossification.

Through which process of bone formation do most parts of the cranial base develop?

Endochondral ossification.

Why are newborn infants particularly vulnerable to facial nerve injury during a forceps delivery?

Newborns lack a mastoid process, leaving the facial nerve exposed superficially as it emerges from the stylomastoid foramen.

What shape is the anterior fontanelle, and when does it typically cease to be palpable?

It is diamond- or star-shaped and closes by 18 months of age.

What is the remnant of a persistent frontal suture called when it fails to fuse in approximately 8% of individuals?

A metopic suture.

What cranial malformation is caused by premature closure of the sagittal suture, resulting in a long, narrow, wedge-shaped cranium?

Scaphocephaly.

What cranial malformation is depicted in this clinical photograph, which is caused by premature closure of the coronal suture and results in a high, tower-like cranium?

Oxycephaly (or turricephaly).

What three diagnostic conditions can physicians evaluate by palpating an infant's fontanelles?

Progress of bone growth, degree of hydration (a depressed fontanelle indicates dehydration), and intracranial pressure level (a bulging fontanelle indicates increased pressure).

Which four bones unite to form the H-shaped sutural junction known as the pterion?

The frontal bone, parietal bone, greater wing of the sphenoid bone, and temporal bone.

Why is a severe blow to the pterion considered life-threatening?

The pterion overlies the anterior branches of the middle meningeal vessels, and a fracture there can cause an epidural hemorrhage.

What defining orientation establishes the Orbitomeatal Plane (Frankfort Horizontal Plane)?

The inferior margin of the orbit and the superior margin of the external acoustic meatus lie in the same horizontal plane.

Which craniometric point represents the most prominent point of the external occipital protuberance?

The Inion.

Which structures pass through the cribriform plate of the ethmoid bone?

The olfactory nerves (CN I).

Which cranial nerve and blood vessel pass through the optic canal?

The optic nerve (CN II) and the ophthalmic artery.

Which major structures pass through the superior orbital fissure?

The superior and inferior ophthalmic veins, lacrimal, frontal, and nasociliary branches of the ophthalmic nerve ($V_1$), oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN VI).

Which cranial nerve branch passes through the foramen rotundum?

The maxillary nerve ($V_2$).

Which structures pass through the foramen ovale?

The mandibular nerve ($V_3$) and the accessory meningeal artery.

Which structures pass through the foramen spinosum?

The middle meningeal artery, middle meningeal vein, and the meningeal branch of the mandibular nerve.

What three structures pass through the internal acoustic meatus?

The facial nerve (CN VII), vestibulocochlear nerve (CN VIII), and labyrinthine artery.

Which cranial nerves pass through the jugular foramen?

The glossopharyngeal nerve (CN IX), vagus nerve (CN X), and spinal accessory nerve (CN XI).

What structure passes through the hypoglossal canal?

The hypoglossal nerve (CN XII).

What major structures pass through the foramen magnum?

The medulla oblongata and meninges, vertebral arteries, spinal accessory nerve (CN XI), anterior and posterior spinal arteries, and dural veins.

What three anatomical structures make up the sella turcica of the sphenoid bone?

The tuberculum sellae, hypophysial fossa, and dorsum sellae.

What structures pass through the stylomastoid foramen?

The facial nerve (CN VII) and the stylomastoid artery.

What structures are transmitted through the incisive foramen (fossa) of the hard palate?

The nasopalatine nerve and the greater palatine blood vessels.

What action does the frontal belly of the occipitofrontalis muscle perform?

It elevates the eyebrows and produces transverse wrinkles across the forehead.

What nerve provides motor innervation to the occipital belly of the occipitofrontalis muscle?

The posterior auricular branch of the facial nerve (CN VII).

What muscle originates on the medial end of the superciliary arch and acts to draw the eyebrows medially and downward?

The corrugator supercilii muscle.

What is the primary difference in function between the orbital part and palpebral part of the orbicularis oculi muscle?

The orbital part closes the eyelids tightly (winking/squinting), while the palpebral part closes the eyelids gently (blinking/sleep).

Which facial muscle compresses the cheek against the teeth and gums during mastication and expels air when blowing?

The buccinator muscle.

Which muscle originates on the lateral aspect of the zygomatic bone, inserts at the angle of the mouth, and elevates the labial commissure to smile?

The zygomaticus major muscle.

Which type of maxillary fracture passes horizontally superior to the maxillary alveolar process and crosses the bony nasal septum?

A Le Fort I fracture.

Which type of maxillary fracture passes from the posterolateral parts of the maxillary sinuses through the infra-orbital foramina to the bridge of the nose?

A Le Fort II fracture.

Which type of maxillary fracture passes horizontally through the superior orbital fissures, ethmoid, nasal bones, sphenoid greater wings, and frontozygomatic sutures?

A Le Fort III fracture.

What muscle originates from the canine fossa of the maxilla and acts to raise the angle of the mouth when smiling or grinning?

The levator anguli oris muscle.

What muscle originates on the body of the mandible anterior to the roots of the inferior incisors, inserts into the skin of the chin, and elevates/everts the lower lip?

The mentalis muscle.

Which nerve branch innervates the platysma muscle?

The cervical branch of the facial nerve (CN VII).

What clinical condition resulting from facial nerve (CN VII) injury leads to facial weakness, drooping of the mouth/eyebrow, and inability to close an eyelid?

Bell's palsy.