Boundaries and bony nasal septum
The bony nasal cavity has two primary boundaries — an inlet and an outlet:
- Anterior boundary is represented by the piriform aperture (Apertura piriformis). This bony opening is bounded by the nasal bone, the nasal notch (Incisura nasalis), and the anterior nasal spine (Spina nasalis anterior) belonging to the maxilla.
- Posterior boundary consists of the posterior nasal apertures, or choanae (Choanae), which lie lateral to the bony septum and lead into the pharyngeal cavity.
Along the midline, the cavity is divided by the bony nasal septum (Septum nasi osseum). Several structures contribute to its formation: the perpendicular plate of the ethmoid bone, the vomer (Vomer), the nasal spine of the frontal bone, and the sphenoidal crest located on the body of the sphenoid bone.
Superior and inferior walls
The bony nasal cavity is enclosed by walls that form its roof and floor:
- Superior wall (roof). Formed by the nasal bone, the nasal part of the frontal bone, the cribriform plate of the ethmoid bone, and the body of the sphenoid bone.
Important note: the nasal cavity communicates with the anterior cranial fossa via the cribriform foramina (Foramina cribrosa).
- Inferior wall (floor). Corresponds entirely to the bony hard palate.
Important note: the inferior wall connects the nasal cavity with the oral cavity via the incisive canals (Canales incisivi).
Lateral wall and nasal meatuses
Lateral wall features the most complex topography. It is formed by a complex of bones: the nasal bone, the frontal process of the maxilla, the lacrimal bone, the ethmoidal labyrinth, the three nasal conchae (superior, middle, and inferior), the nasal surface of the maxilla, the perpendicular plate of the palatine bone, and the medial plate of the pterygoid process of the sphenoid bone.
The nasal conchae divide the lateral space into specialized channels — nasal meatuses, each with specific communications:
- Superior nasal meatus (Meatus nasi superior) — communicates with the posterior ethmoidal cells and the sphenoid sinus.
- Middle nasal meatus (Meatus nasi medius) — leads to the anterior and middle ethmoidal cells, as well as the frontal and maxillary sinuses.
- Inferior nasal meatus (Meatus nasi inferior) — contains the opening of the nasolacrimal canal (Canalis nasolacrimalis).
- Common nasal meatus (Meatus nasi communis) — a narrow vertical space situated between all conchae and the bony septum.
- Nasopharyngeal meatus (Meatus nasopharyngeus) — opens into the nasopharynx region.
Additionally, the sphenopalatine foramen (Foramen sphenopalatinum) is located on the lateral wall, through which the nasal cavity communicates with the pterygopalatine fossa.
Adjacent structures: temporal and infratemporal fossae
In addition to the nasal cavity proper, this region contains important fossae that are directly or indirectly connected to it:
Temporal fossa (Fossa temporalis) Bounded superiorly by the superior temporal line, and inferiorly by the zygomatic arch and infratemporal crest. Its anterior borders are set by the temporal line and the temporal surface of the zygomatic bone, and posteriorly and medially by the greater wing of the sphenoid bone. It communicates with the infratemporal fossa and the orbit (via the zygomaticofacial foramen).
Infratemporal fossa (Fossa infratemporalis) Located inferior to the temporal fossa. Bounded superiorly by the zygomatic arch and infratemporal crest, and anteriorly by the infratemporal surface of the maxilla. The medial boundary is the lateral plate of the pterygoid process, and the lateral boundary is the ramus of the mandible. Communications of the infratemporal fossa:
- with the orbit (via the inferior orbital fissure);
- with the oral cavity (via the alveolar canals);
- with the pterygopalatine fossa (via the pterygomaxillary fissure);
- with the mandible (via the mandibular canal).
Pterygopalatine fossa
Pterygopalatine fossa (Fossa pterygopalatina) is a deep, slit-like continuation of the infratemporal fossa. It has 4 walls and serves as a crucial distribution center, featuring 6 major communications:
- With the orbit — via the inferior orbital fissure.
- With the middle cranial fossa — via the foramen rotundum.
- With the external cranial base — via the pterygoid canal.
- With the oral cavity — via the greater palatine canal.
- With the nasal cavity — via the sphenopalatine foramen.
- With the infratemporal fossa — via the pterygomaxillary fissure.
Briefly: answers to topical questions
What nerves and blood vessels pass through the sphenopalatine foramen?
The following blood vessels and nerves pass through the sphenopalatine foramen:
- Sphenopalatine artery (A. sphenopalatina);
- Corresponding veins;
- Lateral and medial superior posterior nasal branches (Rr. nasales posteriores superiores laterales et mediales) — branches of the maxillary nerve (N. maxillaris).
This foramen provides communication between the nasal cavity and the pterygopalatine fossa.
What passes through the foramen rotundum connecting the pterygopalatine fossa to the middle cranial fossa?
The maxillary nerve passes through the foramen rotundum.
- Maxillary nerve (N. maxillaris) — a sensory nerve that enters the pterygopalatine fossa through this foramen.
It subsequently gives rise to the posterior superior alveolar branches, infraorbital nerve (n. infraorbitalis), zygomatic nerve (n. zygomaticus), and branches to the pterygopalatine ganglion (ganglion pterygopalatinum).
What anatomical structures pass through the incisive canal?
The following anatomical structures pass through the incisive canal:
- Nasopalatine nerve (N. nasopalatinus / n. nasopalatini) — a branch of the maxillary nerve (N. maxillaris), which belongs to the second division of the trigeminal nerve. It emerges from the nasal cavity onto the hard palate.
- Nasopalatine artery (a. nasopalatini).
- Nasopalatine vein (v. nasopalatini).
The canal opens onto the hard palate via the incisive foramen.
Mnemonic for nasal meatus destinations: Superior — Sphenoid sinus and Posterior ethmoidal cells; Middle — Frontal, Maxillary sinuses and Anterior/middle ethmoidal cells; Inferior — Nasolacrimal canal only.
Class and exam questions
What forms the bony nasal septum?
The bony septum (Septum nasi osseum) is formed by the perpendicular plate of the ethmoid bone, the vomer, the nasal spine of the frontal bone, and the sphenoidal crest of the body of the sphenoid bone.
Where does the nasolacrimal canal open?
The nasolacrimal canal (Canalis nasolacrimalis) opens strictly into the inferior nasal meatus (Meatus nasi inferior).
How does the nasal cavity communicate with the oral cavity?
Communication with the oral cavity is established through the inferior wall (hard palate) via the incisive canals (Canales incisivi).
How many communications does the pterygopalatine fossa have?
The pterygopalatine fossa has 6 communications: with the orbit, middle cranial fossa, external cranial base, oral cavity, nasal cavity, and infratemporal fossa.
What else to study on this topic
- Detailed structure of the lateral wall of the nasal cavity
- Anatomy and boundaries of the temporal fossa
- Walls and communications of the infratemporal fossa
- Communications of the pterygopalatine fossa (Fossa pterygopalatina) with other cavities
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