Nasal cavity, choanae, vascular and nerve supply

Introduction to some important terms

• The nose: is the beginning of the respiratory tract and is divided into external nose (visible) and nasal cavity.
• The nasal cavities are open to the paranasal sinuses and the nasopharynx.
• The nose warms, humidifies, and purifies the air going into the resp system. Sneezing and other reflexes protect the resp organs. It also has olfactory functions (smelling).
• External nose anatomy:
  • Nasal root —> continuous with the forehead (depression where the nasal bones meet with the frontal bone).
  • Dorsum nasi —> is the bridge of the nose (bony)
  • The left and right ala of the nose (alae nasi dextra and sinistra) —> the cartilaginous sides of the nose.
  • Apex nasi —> the tip of the nose.
  • Columella —> the membranous septum of the nose between the apex nasi and philtrum.
  • Nares —> nasal orifices.

External Nose - Sobotta

Bones and Cartilages of the nose (external) - Thieme Atlas

Bones and Cartilages of the external nose

• From the upper side, the nasal bone is attached to the frontal bone via the nasofrontal suture and the frontal process of the maxilla via the nasomaxillary suture (all posteriorly forming the nasal root).
• The nasal bone is then attached to a set of hyaline cartilages that contruct the shape of the nose. The nasal bone is attached to the lateral nasal cartilage, which is then attached to the major alar cartilage that make us the nasal alae. The minor alar cartilages sit on a set of connective tissue on the ala nasi.
• The major alar cartilage forms the medial and lateral crura of the nose.

Nasal Cavity

• Pyramidally shaped; communicates with the exterior world through the nares and the nasopharynx through the choanae.
• The nasal vestibule is the space just inside the nose surrounded by alar cartilages; it is the only place in the nasal cavity that contains nasal hair. More inside, we will find the nasal cavity proper (olfactory and respiratory parts). Those are separated by the limen nasi.
• Floor of nasal cavity:
  • Much wider than the roof.
  • Created by the horizontal plate of palatine bone and palatine process of maxillary bone, which both form the hard palate.
  • At the front, it is made by the cartilaginous skeleton of the external nose.
• Roof of nasal cavity:
  • At the highest point, it is formed by the cribriform plate of the ethmoid bone (where the olfactory nerve passes through).
  • Going down, we have the spina nasalis of the frontal bone, nasal bone, and then the lateral nasal cartilages along with the major and minor alar cartilages.
  • The sphenoethmoidal recess is a place where the ethmoidal air cells and sphenoid sinuses drain into the superior meatus of the nasal cavity.
• Medial wall of nasal cavity:
  • Anteriorly, it starts with the Pars membranacea, which is made up of dense connective tissue.
  • Then, we have the septal cartilage (pars cartilaginea), and posteriorly we have the perpendicular plate of the ethmoid bone (pars ossea). Posteroinferiorly, we get the vomer bone sitting down.
  • The medial wall separates the 2 nasal cavities from each other.
• Lateral wall of nasal cavity:
  • Formed by the superior and middle conchae of the ethmoid bone, inferior concha, frontal process of maxillary, palatine, lacrimal, and nasal bones.
  • Superior, middle, and inferior meatuses are grooves formed under the corresponding conchae.
  • The sphenoid sinus drains into the sphenoethmoidal recess (a space between the superior concha and openings for the sphenoid sinus right at the junction of the sphenoid and enthmoid bones) above the superior concha.
  • The posterior ethmoidal air cells drain into the superior nasal meatus.
  • The frontal sinus (frontonasal duct into hiatus semilunaris), maxillary sinus (hiatus semilunaris), and anterior and middle (on ethmoid bulla, which is a big anterior ethmoid cell that protrudes a bit outwards) ethmoidal cells open into the middle nasal meatus.
  • The nasolacrimal duct drains into the inferior nasal meatus.

• The nasal meatuses increases surface area of air touching the nasal mucosa, as well as it slows down the air so that it can stay more in the nasal cavity to gain heat and humidity. They are covered by cavernous bodies.
• The uncinate process is a projection from the ethmoidal bone. It partially closes the maxillary hiatus and by that forms the hiatus semilunaris. The top edge forms the ethmoidal infundibulum between the uncinate process and the ethmoidal bulla.

Medial Wall of the Nasal Cavity (left side) - Thieme Atlas

Lateral Wall of the Nasal Cavity (Right side) with Choanae - Thieme Atlas

Choanae

• This is the opening between the nasal cavity and the nasopharynx.
• The space is bounded by:ant
  • Anteriorly and inferiorly by the palatine bone.
  • Superiorly and posteriorly by the sphenoid bone.
  • Laterally by the medial pterygoid plate.
  • Medially by the vomer.

Arterial Supply

• By internal and external carotid arteries.
• Internal carotid artery:
  • Emits the ophthalmic artery which passes through the optical canal into the orbital.
  • Then, from the orbital through the anterior and posterior ethmoidal foramina they become the anterior ethmoidal artery and posterior ethmoidal artery.
  • Those 2 branch out into the nasal septum and lateral wall of nasal cavity.
  • The anterior ethmoidal artery emits the lateral anterior nasal branch and the anterior septal branch.
  • The posterior ethmoidal artery perfuses just a small area of nasal cavity near the skull.
  • The outer nose receives blood from the dorsal nasal artery from the supratrochlear artery which is from the ophthalmic artery as well.
  • The vestibulum nasi receives blood via the r. Septi nasi from the superior labial artery (from facial artery).
• External carotid artery:
  • The maxillary artery emits the sphenopalatine artery, which supplies most of the nasal cavity.
  • The sphenopalatine artery passes through the pterygopalatine fossa into the nose and splits into posterior lateral nasal branches and posterior septal branches.
• The area of overlap between the internal and external carotid branches is called Kiesselbach’s area (septal parts of anterior ethmoid artery and sphenopalatine artery).

Arterial Supply of Nasal Cavity (Medial and Lateral Walls) - Sobotta

Venous Drainage

• The venous drainage tends to follow the arteries. They drain to the pterygoid plexus, facial vein, or cavernous sinus.
• Clinical note: In some people, nasal veins can drain into the sagittal sinus, and this can cause nose infections to reach the brain.

Nerve Supply

• Special innervation (sense of smell):
  • Olfactory nerves - cribriform plate.
• General innervation (sensation):
  • Nasopalatine nerve (from maxillary nerve).
  • Nasociliary nerve (from ophthalmic nerve).
  • External skin by branches of trigeminal nerve.

Nerve. Supply of Nasal Cavity - TeachMeAnatomy

References, Sources, and Links

• Jens Waschke (editor), Tobias M. Böckers (editor), Friedrich Paulsen - Sobotta Anatomy Textbook_ With Latin Nomenclature (2018, Educa Books).
• Anne M Gilroy, Brian R MacPherson, Jamie Wikenheiser, Michael Sc - Atlas of Anatomy (2020, Thieme).
• https://teachmeanatomy.info/head/organs/the-nose/nasal-cavity/