Chapter 6 // The Skull (Axial)

How many bones form the axial and appendicular skeleton?

206 bones

How many bones are in the axial skeleton and what are its functions?

The axial skeleton has 80 bones; it supports the head, neck and trunk; protects the brain, spinal cord, and thoracic organs.

What is the most complex bony structure of the skeleton, formed by the cranial and facial bones?

The skull

What type of bones is the skull made of and what are they connected by?

They are made of flat bones; they are connected by sutures

How many bones comprise the skull? How many cranial bones and how many facial bones are there?

22 bones total; there are 8 cranial bones, and 14 facial bones

There are 85 named openings in the skull. What are the 4 most common names for them?

Foramina (singular = foramen), canals, fissures, lacerum

Name all 8 of the cranial bones.

Frontal, parietal (2), occipital, temporal (2), sphenoid, and ethmoid

Which cranial bone forms the forehead and the roofs of the orbits (bony cavity containing eyeballs)?

The frontal bone

What is the opening above each orbit called, and which structures does it transmit?

Supra-orbital foramen; supra-orbital nerve and artery

Which two paired cranial bones are located posterolateral to the frontal bone, forming the sides of the cranium?

The parietal bones

Where are the superior and inferior temporal lines located and what purpose do they serve?

They are low ridges on the external surface of each parietal bone; they mark the attachment of the temporalis muscle (closes the mouth)

What are the six major sutures of the skull, and which cranial bone(s) are they associated with?

Lambdoid, sagittal, coronal, frontonasal, occipitomastoid, squamous; the parietal bones.

Which cranial bone forms the floor and back wall of the skull?

The occipital bone

What is the hole in the base of the occipital bone through which the spinal cord passes and is connected to the brain?

The foramen magnum (the “big hole”)

What are the four major regions of the temporal bones?

Squamous, Tympanic, Mastoid, and Petrous

Which region of the temporal bone would you find the zygomatic process?

Squamous region

What is the common name for the zygomatic arch?

The cheekbone (Zygomatic bone defines the projection of the cheek)

Which cranial bone holds the styloid process and what does that process mark?

The styloid process (process = projection) is held by the temporal bone; it marks the attachment site for ligaments that support the hyoid bone and muscles of the tongue, pharynx, and larynx.

What is the “breast-shaped” region posterior to the ear?

The mastoid region.

What is the rough projection that anchors some neck muscles that rotate and extend the the head?

The mastoid process

What is the most massive portion of the temporal bone and what 4 openings can you find there?

The petrous region; contains the jugular foramen, carotid canal, foramen lacerum, and the internal acoustic meatus

What is the “bat-shaped” bone that spans the width of the cranial floor and forms the anterior plateau of the middle cranial fossa (fossa = hollows, depressions)?

The sphenoid bone.

What is the part of the sphenoid called that contains the hypophyseal fossa? (hypophyseal = pituitary)

The Sella Turcica (sella = saddle shaped)

What are the five important openings of the sphenoid?

Optic foramen, superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum

Which cranial bone is irregularly shaped, located anterior to the sphenoid, and forms most of the medial bony area between the nasal cavity and the orbits?

The ethmoid bone.

What are the 3 major parts of the ethmoid bone?

Cribriform plates, ethmoidal labyrinth, and perpendicular plate

Which suture can be found where the parietal bones articulate with the frontal bone?

The coronal suture

Which suture can be found where the parietal bones articulate with the temporal bones inferiorly?

The squamous suture

Which suture can be found where right and left parietal bones meet?

The sagittal suture

What are the 14 facial bones?

Mandible, Maxillae (2), Zygomatic (2), Nasal (2), Lacrimal (2), Palatine (2), Vomer (1), and Inferior Nasal Conchae (2)

All facial bones, except for which, articulate with the maxillae?

The mandible.

They say there are 4 “special” parts of the skull to consider. What are these parts called?

The orbits of the eyes, the nasal complex/nasal cavity, the paranasal sinuses, and the hyoid bone.

What is the function of the orbit(s)?

Enclose and protect the eyeballs.

What is the nasal complex/nasal cavity constructed of?

Bone and cartilage.

How would you describe the paranasal sinuses of the skull?

Air-filled sacs that produce mucus, lighten skull bones, and resonate during sound production.

What is the only bone in the body that does not articulate directly with any other bone?

The hyoid bone.

The “greater horns” are a larger process of the hyoid that do what?

Support the larynx and serve as the base for muscles that move the tongue.

Which statement applies to the sella turcica?

What is the relationship between the pituitary gland and the sphenoid bone?

There is a depression between the “wings” of the sphenoid bone that cradles the pituitary gland just inferior to the brain. This depression is called the hypophyseal fossa and the bony enclosure is called the sella turcica.

What are some factors that can cause increased mucus production by the mucous membranes of the paranasal sinuses?

The mucous membranes of the paranasal sinuses respond to stress in their environment by producing more mucus. The mucus flushes irritants off the wall of the nasal cavities. Many things can cause this including sudden changes in temperature or humidity, irritating vapors, and bacterial or viral infections.

What is the relationship between the temporal bone and the ear?

The petrous region of the temporal bone houses the internal ear structures that provide information about hearing and balance.

What is the purpose of the many small openings in the cribriform plate of the ethmoid bone?

The foramina (holes) in the cribriform plate permit passage of the olfactory nerves, providing the sense of smell.

Which bone is a passageway for sensory nerves from teeth, gums, lips, and chin?

The mandible

Which bones are the smallest in the skull and contain a groove that aids in tear drainage?

The lacrimal bones

What is the largest fontanel?

Anterior fontanel

Where is the supra-orbital foramen located?

Frontal bone