FORAMINA OF SKULL

The skull is rigidly structured to protect the brain but has many foramina (openings) for passage of nerves (nn.), arteries (aa.) and veins (vv.); it is best to have someone show you where they are; however, knowledge of the foramina of the skull is ESSENTIAL to understanding the anatomy of the head and neck. The foramina are listed below according to how one can view them on a skull and indicate which bone they are in, what areas they connect and which structures that pass through them; many of the foramina are doubly listed as they can be seen from the inside or outside of the skull. Foramina listed in [brackets] are not required for identification on the practical exam.

I. FACE

1. Supraorbital notch or foramen ‑ in frontal bone; connects orbit and forehead; contains Supraorbital n., a. and v.

2. Infraorbital foramen ‑ in maxillary bone; connects orbit and face; contains Infraorbital n., a. and v.

3. Zygomatico‑facial foramen ‑ in zygomatic bone; connects orbit and face; contains Zygomatico‑facial nerve.

4. Mental foramen ‑ in mandible; connects mandibular canal to face; contains Mental n., a. and v.

II. CALVARIUM AND CRANIAL VAULT

1. Parietal foramen ‑ in parietal bone on either side of sagittal suture; connects; diploe in bone to scalp; contains emissary veins.

2. Mastoid foramen ‑ located behind mastoid process of temporal bone; connects diploe in bone to scalp; contains emissary veins.

III. BASE OF CRANIUM FROM EXTERNAL SIDE

1. Foramen ovale ‑ located in sphenoid bone; connects middle cranial fossa and infratemporal fossa; contains Mandibular division of V (V3) and Accessory Meningeal artery (when present).

2. Foramen spinosum ‑ located in sphenoid bone; connects middle cranial fossa and infratemporal fossa; contains Middle meningeal artery and Nervus Spinosus (branch of V3).

3. Bony part of auditory tube ‑ located in temporal and sphenoid bones; connects middle ear and (via cartilaginous part of auditory tube) nasopharynx; contains air.

4. Carotid canal ‑ located in temporal bone; connects base of skull to middle cranial fossa (opening of Carotid canal in middle cranial fossa called Foramen Lacerum); contains Internal carotid artery and sympathetic plexus surrounding artery.

5. Stylomastoid foramen ‑ located in temporal bone; connects internal auditory meatus of posterior cranial fossa to base of skull (via facial canal); contains Facial nerve (VII).

6. Jugular foramen ‑ located in temporal and occipital bones; connects posterior cranial fossa and base of skull; contains Internal Jugular vein, Glossopharyngeal (IX), Vagus (X) and Accessory (XI) nerves.

7. Hypoglossal canal ‑ located in occipital bone; connects posterior cranial fossa and base of skull; contains Hypoglossal nerve (XII).

8. Foramen magnum ‑ located in occipital bone; connects posterior cranial fossa and vertebral canal; contains spinal cord (with meninges) and Vertebral arteries and veins.

[9. Pterygoid canal ‑ located in sphenoid bone; connects base of skull to pterygopalatine fossa; contains Nerve and Artery of Pterygoid canal.]

10. Pterygomaxillary fissure ‑ located between maxillary and sphenoid bones (greater wing of sphenoid); connects pterygopalatine fossa and infratemporal fossa; contains Maxillary artery (third part) and branches of Maxillary nerve (V2).

11. Posterior superior alveolar foramina ‑ located in maxillary bone; connects infratemporal fossa to maxillary teeth; contains Posterior superior alveolar n., a. and v.

[12. Petrotympanic fissure ‑ located in temporal bone (between petrous and tympanic parts); connects facial canal and base of skull; transmits Chorda Tympani (branch of VII) and Anterior Tympanic artery.]

III. INTERIOR OF SKULL

1. Olfactory foramen ‑ located in cribriform plate of ethmoid bone in anterior cranial fossa; connects anterior cranial fossa and nasal cavity; contains branches of Olfactory nerve (fila olfactoria) (I).

2. Optic foramen and canal ‑ located at base of Lesser wing of sphenoid bone in middle cranial fossa; connects middle cranial fossa to orbit; contains Optic nerve (II) and Ophthalmic artery.

3. Superior Orbital fissure ‑ located between Greater and Lesser wings of Sphenoid bone in Middle Cranial fossa; connects middle cranial fossa and orbit; contains Oculomotor (III), Trochlear (IV), Abducens (VI) nerves and Ophthalmic division of Trigeminal nerve (V1) and Ophthalmic veins.

5. Foramen rotundum ‑ located in Greater wing of Sphenoid bone; connects middle cranial fossa and Pterygopalatine fossa; contains Maxillary division of Trigeminal nerve (V2).

6. Foramen ovale ‑ located in sphenoid bone; connects middle cranial fossa and infratemporal fossa; contains Mandibular division of V (V3) and Accessory Meningeal artery (when present).

7. Foramen spinosum ‑ located in sphenoid bone; connects middle cranial fossa and infratemporal fossa; contains Middle meningeal artery and Nervus spinosus (branch of V3).

[8. Hiatus for Greater Petrosal Nerve (Superior hiatus) ‑ located in temporal bone; connects facial canal (in temporal bone) to middle cranial fossa; contains Greater Petrosal nerve (branch of Facial nerve VII). (note: look for slit or crack in petrous part of temporal bone directed toward foramen lacerum).]

9. Internal auditory meatus ‑ located in temporal bone; connects posterior cranial fossa to Inner ear and (via facial canal) Stylomastoid foramen; contains Facial (VII) and Vestibulocochlear (VIII) nerves.

10. Jugular foramen ‑ located in temporal and occipital bones; connects posterior cranial fossa and base of skull; contains Internal Jugular vein, Glossopharyngeal (IX), Vagus (X) and Accessory (XI) nerves.

11. Hypoglossal canal ‑ located in occipital bone; connects posterior cranial fossa and base of skull; contains Hypoglossal nerve (XII).

12. Foramen magnum ‑ located in occipital bone; connects posterior cranial fossa and vertebral canal; contains spinal cord (with meninges) and Vertebral arteries and veins.

IV. ORBIT

1. Optic foramen and canal ‑ located at base of Lesser wing of sphenoid bone in middle cranial fossa; connects middle cranial fossa to orbit; contains Optic nerve (II) and Ophthalmic artery.

2. Superior Orbital fissure ‑ located between Greater and Lesser wings of Sphenoid bone in Middle Cranial fossa; connects middle cranial fossa and orbit; contains Oculomotor (III), Trochlear (IV), Abducens (VI) nerves and Ophthalmic division of Trigeminal nerve (V1) and Ophthalmic veins.

3. Inferior Orbital fissure ‑ located between sphenoid and maxillary bones; connects pterygopalatine fossa and infratemporal fossa to orbit; contains Infraorbital and Zygomatic nn., aa. and vv. (nerves are branches of V2).

4. Anterior and Posterior Ethmoidal Foramina ‑ located between ethmoid and frontal bones; connect orbit and nasal cavity; contain (respectively) Anterior and Posterior Ethmoidal nn., aa., and veins (nerves are branches of V1; arteries are branches of Ophthalmic artery).

5. Supraorbital notch or foramen ‑ located in frontal bone; connect orbit and forehead; contain Supraorbital n., a. and v.

6. Infraorbital foramen ‑ in maxillary bone; connects orbit and face; contains Infraorbital n., a. and v.

7. Nasolacrimal duct ‑ located in maxillary, lacrimal bones and Inferior nasal concha; connects orbit and nasal cavity; contains membranous nasolacrimal duct and tears.

V. ORAL CAVITY

1. Incisive foramen ‑ located in maxillary bone; connects nasal cavity and oral cavity; transmits Nasopalatine nerve and Sphenopalatine artery and vein.

2. Greater Palatine foramen ‑ located between maxillary and palatine bones; connects pterygopalatine fossa and oral cavity; contains Greater Palatine n., a. and v.

3. Lesser Palatine foramen ‑ located in palatine bone; connects pterygopalatine fossa and oral cavity; contains Lesser Palatine n., a. and v.

VI. NASAL CAVITY

1. Sphenopalatine foramen ‑ located between sphenoid and palatine bones; connects pterygopalatine fossa and nasal cavity; contains Nasopalatine n. and Sphenopalatine a. and v.

2. Anterior and Posterior Ethmoidal Foramina ‑ located between ethmoid and frontal bones; connect orbit and nasal cavity; contain (respectively) Anterior and Posterior Ethmoidal nn. (branches of V1), aa. (branches of Ophthalmic artery), and veins (nerves.