M01.02.036 The External Nose

The external nose is a prominent facial structure, that provides an entrance to the nasal cavity. This guide explores the surface appearance, skeletal structure, muscles, vascular supply, lymphatic drainage, and innervation of the external nose.

Surface Appearance of the External Nose

General Features

Shape: Pyramidal.
Key landmarks:
- Nasal root: Continuous with the forehead (superior boundary).
- Apex: Rounded tip at the inferior end.
- Dorsum: Spans between the root and apex.
- Nares: Openings into the vestibule of the nasal cavity.
  - Boundaries:
    - Medial: Nasal septum.
    - Lateral: Ala nasi (lateral cartilaginous wings).

Landmark	Description
Nasal root	Connects the nose with the forehead.
Apex	The rounded tip of the nose.
Dorsum	The ridge extends from the root to the apex.
Nares	Openings into the nasal cavity.

Skeletal Structure of the External Nose

Components

Bony Component (superior):
- Nasal bones.
- Frontal bone.
- Maxillae.
Cartilaginous Component (inferior):
- Two lateral cartilages.
- Two alar cartilages.
- One septal cartilage.
- Smaller alar cartilages.

Skin and Hair

Bony region: Thin skin.
Cartilaginous region: Thicker skin with sebaceous glands.
Vestibule of the nose: Contains hairs for filtering air.

Muscles of the External Nose

Muscle	Origin	Insertion	Function
Procerus	Fascia over nasal bones	Inferior forehead	Depresses medial eyebrows, wrinkles skin of superior dorsum.
Nasalis (transverse)	Maxilla	Nasal cartilage	Aids in compressing the nasal aperture.
Nasalis (alar)	Maxilla	Major alar cartilage	Dilates nares (flares nostrils).
Depressor septi nasi	Maxilla	Nasal septum and alar cartilage	Assists in flaring nostrils.

Innervation

All nasal muscles are supplied by the facial nerve (CN VII).

Blood Supply and Lymphatic Drainage

Arterial Supply

Skin: Branches of the maxillary and ophthalmic arteries.
Septum and cartilage: Angular artery and lateral nasal artery (branches of the facial artery).

Venous Drainage

Blood drains into the facial vein, which empties into the internal jugular vein.

Lymphatic Drainage

Superficial lymphatic vessels accompany the facial vein.
Ultimately drains into the deep cervical lymph nodes.

Structure	Vascular Supply	Lymphatic Drainage
External skin	Maxillary, ophthalmic arteries	Superficial lymphatics to deep cervical nodes
Septum and cartilage	Angular and lateral nasal arteries	Same as above

Clinical Relevance: Danger Triangle of the Face

Venous connections between the facial vein and cavernous sinus allow infections to spread to the brain, risking:
- Cavernous sinus thrombosis.
- Meningitis.
- Brain abscess.

Innervation of the External Nose

Function	Nerve
Sensory	Trigeminal nerve (CN V):

Clinical Relevance

Saddle Nose Deformity

Cause: Trauma leading to septal damage or nasal septal hematoma.
Mechanism:
- Cartilage depends on blood vessels for nutrients.
- A hematoma disrupts nutrient flow, leading to septal destruction.
- Result: Sunken middle nose.

Points to Remember

The external nose comprises both bony and cartilaginous elements.
The danger triangle highlights the risk of infections spreading to the brain.
Sensory and motor innervation are by branches of trigeminal and facial nerves, respectively.
Muscles of the nose contribute to facial expressions and nasal flaring.
Lymphatic drainage ultimately involves the deep cervical nodes.

Bibliography

TeachMeAnatomy: Anatomy of the External Nose
OpenStax College: Nasal Anatomy (CC BY 3.0).