HoyaDocs · HNSS Block 5 · Head & Neck AnatomyUpdated 28 Sep 2026 · Rev 1.0
Lab 5 Exam-Day Review — The Nose
Dissection of the Nasal Cavity — external nose, septum, lateral wall, paranasal sinus drainage, blood supply, innervation and blowout fractures.
1 · Exam-Day Rules & Top Traps
✍️ Wording
- Use anatomical directions (anterior/posterior, superior/inferior). “Conchae” and “turbinates” are the same thing.
- Spelling counts: sphenoethmoidal recess · semilunar hiatus · ethmoidal bulla · frontonasal duct · nasolacrimal duct · perpendicular plate · vomer · alar · cribriform · Kiesselbach’s plexus · piriform aperture.
★ High-yield traps
- Superior + middle conchae = ethmoid bone; the inferior concha is its own bone.
- Middle meatus drains three sinuses (frontal, maxillary, ethmoidal) → blockage here is the most important cause of sinusitis.
- Inferior meatus = nasolacrimal duct only. No sinus drains there.
- Sphenoid sinus → sphenoethmoidal recess; posterior ethmoidal cells → superior meatus.
- Anterior (piriform) aperture is in front; the choana (posterior nasal aperture) is at the back.
- Kiesselbach’s plexus (anterior septum) = most nosebleeds; sphenopalatine artery (from the maxillary artery) = life-threatening posterior nosebleeds.
- Anterosuperior = V1 (anterior ethmoidal nerve); posteroinferior = V2 (nasopalatine on the septum, posterior nasal nerves laterally).
- Orbital floor blowout → contents drop into the maxillary sinus.
2 · External Nose & Apertures
| Structure | Description |
|---|
| Nasal bones | Paired; the bridge. Meet the frontal bone at the nasion; flanked by the frontal processes of the maxilla |
| Lateral cartilages | Paired upper cartilages |
| Alar cartilages | Paired lower cartilages; lateral crura (sides of the nostrils) + medial crura (between the nostrils) |
| Septal cartilage | Single; connects the cartilaginous external nose to the maxilla; most of the septum |
| Vestibule | Skin-lined entrance just inside the nostril (hairs) |
| Anterior nasal aperture (piriform aperture) | Pear-shaped bony opening once cartilage is removed; bordered by the nasal bones and the maxilla (lateral + inferior) |
| Choana (posterior nasal aperture) | Opening from each nasal cavity into the nasopharynx; choanal atresia = congenital blockage |
Sensory to external nose skin
- Root: infratrochlear nerve (V1)
- Dorsum + tip: external nasal nerve (V1) — end of the anterior ethmoidal nerve
- Sides + ala + vestibule: infraorbital nerve (V2)
“V1 runs down the middle, V2 wraps the sides.” Tip = V1 → Hutchinson sign.
Piriform in front, choana in back
Nostril→Vestibule→Anterior (piriform) aperture→Nasal cavity→Choana → nasopharynx
3 · Nasal Septum
Medial wall (septum), schematic. Anterosuperior septum = anterior ethmoidal nerve (V1); posteroinferior = nasopalatine nerve (V2).
Deviated septum
Shifted off center; treated only if obstruction is significant.
Septal perforation
Hole in the septum — drug use, surgery, autoimmune destruction.
Septal hematoma
Blood within the mucous membrane → pressure compromises blood supply + infection risk.
Septal pathology “DPH”: Deviated · Perforated · Hematoma.
4 · Lateral Wall & Sinus Drainage
Lateral nasal wall, schematic. Sinuses (yellow) drain into the recess and meatuses beneath the conchae.
| Space (superior → inferior) | Location | Drains | Via |
|---|
| Sphenoethmoidal recess | Between superior concha and roof | Sphenoid sinus | — |
| Superior meatus | Between superior and middle conchae | Posterior ethmoidal cells | Small openings |
| Middle meatus ★ | Between middle and inferior conchae | Frontal sinus + anterior ethmoidal cells | Frontonasal duct → anterosuperior end of semilunar hiatus |
| Maxillary sinus | Opening in the floor of the semilunar hiatus |
| Middle ethmoidal cells | On/above the ethmoidal bulla |
| Inferior meatus | Between inferior concha and floor | Nasolacrimal duct | — |
Middle meatus landmarks
- Ethmoidal bulla — rounded bulge formed by the middle ethmoidal cells
- Semilunar hiatus — curved groove; superior border = bulla, inferior border = ethmoid bone
- Maxillary opening in its floor; frontonasal duct at its anterosuperior end
“FAME drains in the middle”: Frontal · Anterior ethmoidal · Maxillary · middle Ethmoidal.
Lab tips
- Lift or remove the middle concha to see the bulla and hiatus.
- Follow the hiatus anterosuperiorly toward the frontal sinus → frontonasal duct.
- Probes from the maxillary sinus exit lower and further back in the hiatus floor.
- Conchae increase surface area and warm/humidify air.
5 · Paranasal Sinuses
| Sinus | Bone / location | Drains to | Sensory | High-yield |
|---|
| Frontal | Frontal bone, above the orbits | Middle meatus (frontonasal duct) | Supraorbital nerve (V1) | Above the orbital roof |
| Ethmoidal cells (anterior, middle, posterior) | Ethmoid, between the orbits | Anterior → middle meatus (frontonasal duct) · middle → bulla · posterior → superior meatus | Anterior + posterior ethmoidal nerves (V1) | Paper-thin medial orbital wall; sinusitis → orbit/cavernous sinus |
| Sphenoid | Body of the sphenoid, under the sella turcica | Sphenoethmoidal recess | Posterior ethmoidal nerve (V1) | Trans-sphenoidal route to the pituitary |
| Maxillary (largest) | Maxilla, below the orbit | Middle meatus (floor of semilunar hiatus) | Infraorbital + superior alveolar nerves (V2) | Roof = orbital floor (infraorbital nerve); sinusitis can mimic upper toothache |
Sinus sensation: three up top are V1; the maxillary below the orbit is V2.
6 · Blood Supply & Nosebleeds
Arteries (dual ICA + ECA supply)
- Ophthalmic (ICA) → anterior + posterior ethmoidal arteries
- Maxillary (ECA) → sphenopalatine artery (largest to the lateral wall), greater palatine artery
- Facial (ECA) → superior labial artery (septal branch)
Veins & lymph
- Ophthalmic veins → cavernous sinus (valveless “danger zone”)
- Facial vein → internal jugular vein
- Sphenopalatine vein → pterygoid plexus
- Lymph: anterior → submandibular nodes · posterior + sinuses → retropharyngeal → upper deep cervical nodes
| Anterior nosebleed | Posterior nosebleed |
|---|
| Source | Kiesselbach’s plexus (anterior septum) | Sphenopalatine artery (lateral wall) |
| Frequency | Most nosebleeds | Less common |
| Severity | Usually minor | Life-threatening |
7 · Innervation
Medial wall (septum)
| Anterosuperior | Posteroinferior |
|---|
| Anterior ethmoidal nerve (V1) | Nasopalatine nerve (V2) — sphenopalatine foramen → septum → incisive canal |
Lateral wall
| Anterosuperior | Posteroinferior |
|---|
| Anterior ethmoidal nerve (V1) | Posterior nasal nerves (V2) |
| Function | Nerve / pathway |
|---|
| Smell (special sensory) | CN I — olfactory epithelium in the roof → cribriform foramina; fracture → anosmia |
| General sensation | CN V: V1 anterosuperior, V2 posteroinferior |
| Secretomotor (↑ mucus) | CN VII → greater petrosal nerve → pterygopalatine ganglion → V2 branches |
“Front-top = V1, back-bottom = V2.” “Smell = I, feel = V, secrete = VII.” V1 enters from the orbit (ethmoidal foramina); V2 enters from behind (sphenopalatine foramen).
8 · Orbital Blowout Fractures & the Sinuses
| Floor fracture | Medial wall fracture |
|---|
| Blows into | Maxillary sinus | Ethmoidal air cells |
| Nerve | Infraorbital (V2) → numb lower lid, cheek, upper lip, side of nose | — |
| Globe | Hypoglobus (sits low) / enophthalmos (sunken back) | Enophthalmos |
| Movement | Trapped inferior rectus → can’t look up | Trapped medial rectus → can’t look out toward the injured side |
Enophthalmos
Eye sunken back — orbital contents escape into a sinus.
Proptosis / exophthalmos
Eye bulges forward — something occupies space behind it (e.g., cavernous sinus thrombosis).
Hypoglobus
Eye sits lower — tissue drops into the maxillary sinus.
Paralyzed muscle loses its own action; trapped muscle blocks the opposite action. Don’t confuse proptosis (globe forward) with ptosis (drooping lid).
9 · Clinical Correlations
| Scenario | Answer |
|---|
| Facial pain + congestion from frontal, maxillary and ethmoidal sinuses at once | Blockage of the middle meatus |
| Brisk bleeding from the front of the septum | Kiesselbach’s plexus |
| Heavy posterior bleeding not controlled by anterior packing | Sphenopalatine artery |
| Loss of smell after head trauma | CN I at the cribriform plate → anosmia |
| Newborn with nasal obstruction | Choanal atresia |
| Nasal obstruction after trauma with a boggy septal swelling | Septal hematoma — drain (ischemia + infection risk) |
| Hole in the septum in a cocaine user | Septal perforation |
| Ethmoid sinusitis → lid swelling, proptosis, weak eye movements | Spread via orbital veins → cavernous sinus |
| Pituitary tumor removal through the nose | Trans-sphenoidal approach via the sphenoid sinus |
| Runny nose when crying | Tears → nasolacrimal duct → inferior meatus |
| Numb cheek + can’t look up after a punch to the eye | Orbital floor blowout into the maxillary sinus |
10 · Self-Check Questions
Answer first, then open each one to check.
1. Which conchae belong to the ethmoid bone?
Superior and middle conchae. The inferior concha is its own bone.
2. What drains into the sphenoethmoidal recess?
The sphenoid sinus.
3. What drains into the superior meatus?
Posterior ethmoidal cells.
4. List everything that drains into the middle meatus and how.
Frontal sinus + anterior ethmoidal cells (frontonasal duct); maxillary sinus (floor of the semilunar hiatus); middle ethmoidal cells (ethmoidal bulla).
5. What is the only structure that opens into the inferior meatus?
The nasolacrimal duct.
6. Name the three components of the nasal septum.
Septal cartilage (anterior), perpendicular plate of the ethmoid (posterosuperior), vomer (posteroinferior).
7. What is the other name for the anterior nasal aperture, and which bone borders it laterally and inferiorly?
Piriform aperture; the maxilla.
8. Which nerve supplies the posteroinferior septum?
Nasopalatine nerve (V2).
9. Which nerve supplies the anterosuperior nasal cavity (both walls)?
Anterior ethmoidal nerve (V1).
10. Where do most nosebleeds come from?
Kiesselbach’s plexus on the anterior septum.
11. Which sinus is the largest, and what forms its roof?
Maxillary sinus; the orbital floor (with the infraorbital nerve).
12. What is enophthalmos?
Posterior displacement (sinking) of the eyeball into the orbit.