Anatomy
Head and Neck
A 45 year old man presents to ED with an ongoing nose bleed. On examination you suspect the site of bleeding to be in Little's area. Which of the following blood vessels are likely to be involved:
Answer:
Kiesselbach's plexus (Little's area) is formed by anastomosis between branches of four arteries on the anterior nasal septum:- The greater palatine artery (maxillary artery)
- The sphenopalatine artery (maxillary artery)
- The superior labial artery (facial artery)
- The anterior ethmoidal artery (ophthalmic artery)
Nasal Cavity
Anatomy / Head and Neck / Nose and Paranasal Region
Last Updated: 11th April 2019
The nasal cavities are separated from each other by a midline nasal septum, from the oral cavity below by the hard palate and from the cranial cavity above by parts of the frontal, palatine, ethmoid and sphenoid bones. The nasal cavity is lined by ciliated epithelial cells which help trap and remove particulate matter from the airway.
Boundaries
Table: Anatomical Boundaries of the Nasal Cavity
| Space | Nasal Cavity |
|---|---|
| Floor | Hard palate (palatine process of maxilla and horizontal plate of palatine bone) |
| Roof | Frontal bone, nasal bone, cribriform plate of ethmoid bone, sphenoid bone |
| Medial wall | Thin nasal septum (formed primarily from perpendicular plate of ethmoid bone, vomer and septal cartilage) |
| Lateral wall | Ethmoid bone, nasal bone, palatine bone, sphenoid bone, lacrimal bone, maxilla, conchae |
Each nasal cavity has a floor, a roof, a medial and a lateral wall.
The floor of each nasal cavity consists of soft tissues of the external nose and the upper surface of the palatine process of the maxilla and the horizontal plate of the palatine bone (which together form the hard palate).
The roof of the nasal cavity is formed:
- anteriorly by the nasal spine of the frontal bone and the nasal bones, and the lateral processes of the septal cartilage and cartilages of the external nose
- centrally by the cribriform plate of the ethmoid bone
- posteriorly by the sphenoid bone and palatine bone.
The medial wall of the nasal cavity is the mucosa-covered surface of the thin nasal septum.
Bony support for the lateral wall of the nasal cavity is provided by the ethmoid bone, palatine bone, sphenoid bone, lacrimal bones and maxillae.
![Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/07/nasal-conchae.png)
Coronal Section of Nasal Cavities. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Conchae
The lateral wall is characterised by three curved shelves of bone - the conchae - which run one above the other and project medially and inferiorly across the nasal cavity. These conchae increase the surface area of contact between tissues of the lateral wall and respired air.
The conchae divide each nasal cavity into four air channels:
- an inferior nasal meatus (between the inferior concha and the nasal floor)
- a middle nasal meatus
- a superior nasal meatus
- a sphenoethmoidal recess (between the superior concha and the nasal roof).
The openings of the paranasal sinuses are on the lateral wall and roof of the nasal cavities.
In addition the lateral wall also contains the nasolacrimal duct opening onto the inferior nasal meatus, draining tears from the eye into the nasal cavity.
![Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/07/nasal-cavity.png)
Lateral Wall of the Nasal Cavity. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Innervation
The nasal cavities are innervated by:
- The olfactory nerve - carrying olfaction
- The trigeminal nerve - carrying general sensation, anteriorly by the ophthalmic nerve and posteriorly by the maxillary nerve
- The facial nerve - carrying parasympathetic fibres to the nasal glands (which join branches of the maxillary nerve in the pterygopalatine fossa).
Blood Supply
The nasal cavities have a rich vascular supply to allow them to alter the humidity and temperature of respired air.
Blood supply to the nasal cavity is by terminal branches of the maxillary and facial arteries (from the external carotid artery) and ethmoidal branches of the ophthalmic artery (from the internal carotid artery).
The vessels form extensive anastomoses with each other, particularly in the anterior region of the medial wall where there are anastomoses between branches of the greater palatine (maxillary artery), sphenopalatine (maxillary artery), superior labial (facial artery) and anterior ethmoidal arteries (ophthalmic artery) - this area is known as Little's area and is the major site of epistaxis.
Blood Supply of the Nasal Cavity. (Image by Asatur Basmajian via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
