BIO 004 · Human Anatomy
The Skull
Block 2 · Module 2: Axial Skeleton, Skull
A reference for the skull video and lab. The skull is 22 bones in two groups, the cranium that encloses the brain and the facial skeleton that frames the face. This page names every bone, the sutures and fontanelles, the key markings, the cavities, and the major foramina.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice: type the term, click Reveal to check yourself. The comparison grids respond to Study and Quiz too, with a Reveal button on each row.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level material: the cranial markings, the cavities, and the major foramina.
- Distinguish the cranial bones from the facial bones and name the bones in each group.
- Identify the significant markings on each cranial and facial bone, and the major sutures and fontanelles.
- Identify the bones that form the orbit, the nasal cavity, and the hard palate, and locate the paranasal sinuses.
- Name the major foramina of the skull and the structure each one transmits.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
Skull, anterior view
Add a labeled anterior view of the skull.
Skull, lateral view
Add a labeled lateral view showing the sutures and the pterion.
Cranial base
Add a view of the cranial floor showing the fossae and foramina.
The Skull, an Overview
The skull has 22 bones. The eight cranial bones enclose the brain, and the fourteen facial bones frame the face. The hyoid bone of the neck is associated with the skull but is counted separately.
- The skullthe bony framework of the head, 22 bones, plus the associated hyoid bone
- Craniumthe eight cranial bones that enclose and protect the brain
- Facial skeletonthe fourteen facial bones that frame the face and hold the teeth
- Calvariathe domed roof of the cranium, the skullcap
- Cranial basethe floor of the cranium, shaped into anterior, middle, and posterior cranial fossae
The Cranial Bones
Eight bones: the frontal, occipital, sphenoid, and ethmoid are single, the parietal and temporal bones are paired. The grid gives them at a glance, then each bone is broken out below with its significant markings.
| Bone | Number | Region it forms |
|---|---|---|
| Frontal bone | single | the forehead, the roof of the orbits, and the floor of the anterior cranial fossa |
| Parietal bones | paired | the superior and lateral walls of the cranium |
| Temporal bones | paired | the inferior lateral walls and part of the cranial base, house the ear |
| Occipital bone | single | the posterior wall and much of the cranial base |
| Sphenoid bone | single | the central wedge of the cranial base, articulates with every other cranial bone |
| Ethmoid bone | single | the deepest cranial bone, between the orbits, forms part of the nasal cavity |
Frontal bone
- Squamous partthe broad plate of the forehead
- Supraorbital marginthe ridge above each orbit
- Supraorbital foramenthe opening in that margin, passes the supraorbital nerve and vessels
- Glabellathe smooth area between the eyebrow ridges
- Orbital platesthe paired plates that roof the orbits and floor the anterior cranial fossa
- Frontal sinusthe air space within the bone, above the orbits
Parietal bones
- The cranial roofthe pair form most of the superior and lateral walls of the cranium
- Parietal eminencethe rounded high point of each bone, the skull's widest measure
- Suture bordersthey meet at the sagittal suture and form the coronal, lambdoid, and squamous sutures with neighboring bones
Temporal bones
- Squamous partthe flat region forming the lower lateral wall of the skull
- Zygomatic processthe bar that joins the zygomatic bone to complete the zygomatic arch
- Mandibular fossathe socket that receives the mandible, forming the temporomandibular joint
- External acoustic meatusthe opening of the ear canal
- Mastoid processthe bump behind the ear, a muscle attachment, filled with air cells
- Styloid processthe slender spike below the ear that anchors tongue and neck muscles
- Petrous partthe dense wedge of the cranial base that houses the middle and inner ear
- Internal acoustic meatusthe canal carrying the nerves for hearing and facial movement
- Stylomastoid foramenthe exit of the facial nerve, between the styloid and mastoid processes
Occipital bone
- Foramen magnumthe large central opening for the spinal cord
- Occipital condylesthe paired knobs beside the foramen magnum that articulate with the atlas
- External occipital protuberancethe midline bump felt at the back of the head
- Hypoglossal canalthe canal passing the nerve to the tongue muscles
Sphenoid bone
- Bodythe central cube of the bone, contains the sphenoid sinus
- Sella turcicathe saddle on the body whose deep seat cradles the pituitary gland
- Greater wingsthe broad lateral wings forming part of the cranial floor, the orbit, and the lateral skull wall
- Lesser wingsthe smaller anterior wings forming part of the anterior cranial fossa
- Pterygoid processesthe downward projections that anchor the chewing muscles
- Optic canalpasses the optic nerve from the eye
- Superior orbital fissurepasses the nerves that move the eye
Ethmoid bone
- Crista gallithe upright ridge where the falx cerebri, a fold of the brain covering, attaches
- Cribriform platethe perforated horizontal plate that the olfactory nerve filaments pass through
- Perpendicular platethe vertical plate forming the upper part of the nasal septum
- Lateral massesthe side portions, which contain the ethmoidal air cells
- Superior and middle conchaethe scroll-shaped projections into the nasal cavity
The Facial Bones
Fourteen bones: six are paired and two, the vomer and the mandible, are single. The grid gives them at a glance, then the maxillae and the mandible, the largest facial bones, are broken out in detail.
| Bone | Number | What it forms |
|---|---|---|
| Maxillae | paired | the upper jaw, form the anterior hard palate and hold the upper teeth |
| Palatine bones | paired | the posterior hard palate and part of the orbit |
| Zygomatic bones | paired | the cheekbones |
| Nasal bones | paired | the bridge of the nose |
| Lacrimal bones | paired | the medial wall of the orbit, grooved for the tear duct |
| Inferior nasal conchae | paired | scroll-shaped bones on the lateral wall of the nasal cavity |
| Vomer | single | the inferior part of the nasal septum |
| Mandible | single | the lower jaw, the only freely movable bone of the skull |
The maxillae
- Bodythe central mass of the bone, contains the maxillary sinus
- Alveolar processthe ridge that holds the upper teeth
- Palatine processthe shelf forming the anterior part of the hard palate
- Frontal processthe upward projection that meets the frontal bone
- Zygomatic processthe lateral projection that meets the cheekbone
- Infraorbital foramenthe opening below the orbit, passes the infraorbital nerve to the face
The mandible
- Bodythe horizontal, U-shaped portion that holds the lower teeth
- Ramusthe vertical portion on each side, rising to two processes
- Anglethe corner where the body meets the ramus
- Condylar processthe posterior process whose head meets the temporal bone at the jaw joint
- Coronoid processthe anterior process where the temporalis chewing muscle attaches
- Mandibular notchthe gap between the condylar and coronoid processes
- Alveolar processthe ridge that holds the lower teeth
- Mental foramenthe opening on the body that passes the nerve to the chin and lower lip
- Mandibular foramenthe opening on the inner ramus, the entry for the nerve to the lower teeth and the target for a dental block
Sutures and Fontanelles
The major sutures
A suture is an immovable fibrous joint between skull bones. Compare the four major sutures, plus the pterion, by the bones each one joins.
| Suture | Bones it joins | Location |
|---|---|---|
| Coronal suture | the frontal bone and the two parietal bones | runs across the top of the skull, behind the forehead |
| Sagittal suture | the two parietal bones | the midline of the skull roof |
| Lambdoid suture | the parietal bones and the occipital bone | the back of the skull |
| Squamous suture | a parietal bone and a temporal bone | the lower side of the skull, one on each side |
| Pterion | the frontal, parietal, temporal, and sphenoid bones | the H-shaped junction on the side of the skull, the thinnest part |
The fontanelles
Fontanelles are fibrous membrane gaps between the bones of an infant skull. They let the skull compress during birth and grow with the brain. Compare the four named fontanelles.
| Fontanelle | Also called | Location |
|---|---|---|
| Anterior fontanelle | the largest fontanelle | where the frontal and parietal bones meet |
| Posterior fontanelle | the occipital fontanelle | where the parietal bones meet the occipital bone |
| Anterolateral fontanelles | the sphenoidal fontanelles | on the side of the skull, one on each side |
| Posterolateral fontanelles | the mastoid fontanelles | behind the ear, one on each side |
Cavities and Special Features
The orbit and nasal cavity
- The orbitthe bony eye socket, built from seven bones: frontal, sphenoid, zygomatic, maxilla, lacrimal, ethmoid, and palatine
- Nasal cavitythe space behind the nose, with a bony roof, floor, lateral walls, and septum
- Nasal septumthe partition of the nasal cavity, the vomer plus the perpendicular plate of the ethmoid plus septal cartilage
- Hard palatethe bony roof of the mouth, the maxillae in front and the palatine bones behind
Paranasal sinuses
The paranasal sinuses are air-filled cavities that lighten the skull and drain into the nasal cavity. Compare the four by the bone each one occupies.
| Sinus | Bone it occupies | Location |
|---|---|---|
| Frontal sinus | the frontal bone | above the orbits |
| Ethmoidal sinuses | the ethmoid bone | the ethmoid air cells, between the orbits |
| Sphenoidal sinus | the sphenoid bone | within the body of the sphenoid |
| Maxillary sinuses | the maxillae | the largest sinuses, in the cheek region |
The hyoid bone
- Hyoid bonea U-shaped bone in the anterior neck, below the mandible
- Unique featureit does not articulate with any other bone, it is slung by ligaments from the styloid processes
- Roleanchors the tongue and several muscles of the neck and larynx
Major Foramina
A foramen is an opening that lets a nerve or a vessel pass through bone. Compare the major openings of the skull by the bone they pierce and what passes through.
| Foramen | Bone | What passes through |
|---|---|---|
| Foramen magnum | occipital bone | the spinal cord and the vertebral arteries |
| Optic canal | sphenoid bone | the optic nerve, cranial nerve II |
| Superior orbital fissure | sphenoid bone | nerves that supply the eye, including those that move it |
| Foramen ovale | sphenoid bone | a branch of the trigeminal nerve to the lower jaw |
| Cribriform foramina | ethmoid bone | the olfactory nerve filaments, cranial nerve I |
| Internal acoustic meatus | temporal bone | the nerves for hearing and for facial movement |
| Carotid canal | temporal bone | the internal carotid artery |
| Jugular foramen | between the temporal and occipital bones | the internal jugular vein |
| Mental foramen | mandible | the nerve and vessels to the chin and lower lip |
See also: Bone Histology for the bone tissue that builds the skull.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Name the eight cranial bones and contrast their job with that of the facial bones.
- Trace the four major sutures of the skull and name the bones each one joins.
- What passes through the foramen magnum, and why is its location significant?
- Compare the orbit and the nasal cavity by which bones contribute to each.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.