Maxillary sinus

MAXILLARY SINUS

• Maxillary Sinus is an air cavity located within the body of each maxillae.
• The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose.

DEVELOPMENT:

• Development of the maxillary sinus occurs after 3 months of gestation.
• After the development of paranasal sinuses the maxillary sinus are separated from the maxillae by the membrane of the nasal capsule.
• Maxillary sinuses are first to be developed.
• Increase in the height of the maxillae is due to increase in the size of the sinus
• Maxillary sinus fully develops as the human being reaches the age of 16 at secondary dentition 
• Base is formed by the alveolar process and maxillary molars and premolars teeth root lining in close approximation.
• Sinus may increase in size during adult life by extension into the alveolar process.

ANATOMY:

WALLS:

• SUPERIOR – Orbital, base of the infra orbital, and is positioned towards the zygomatic bone
• INFERIOR – Alveolar process of maxillary roots. The roots of molars and pre molars (3,4,5,6,7,8)
• POSTERIOR- Pterygopalatine fossa
• LATERALLY – the nasal bone forms it base
• Each sinus communicate with the nasal cavity through maxillary ostium in the posterior end of the hiatus semilunaris of the middle meatus.
• Osteomeatal complex (OMC) connects Nasal cavity with maxillary sinus

NERVE INNERVATIONS:

• The maxillary sinus is innervated by the maxillary division of the trigeminal nerve.
• The maxillary nerve branches into following nerves :

1. Posterior Superior Alveolar Nerve 
2. Middle Superior Alveolar Nerve 
3. Infra Orbital Nerve 
4. Anterior Superior Nerve
5. Greater and Lesser Palatine Nerves

BLOOD SUPPLY:

• The Maxillary sinus is supplied by blood from following arteries

1. External Carotid Artery
2. SphnopalatineArtery
3. Internal Carotid Artery
4. Maxillary Artery
5. OphthalimeArtery
6. Anterior EthomoidArtery
7. Posterior EthmoidArtery
8. Superior Orbital Artery
9. Supra Orbital Artery
10. Supratrochlear Artery  
11. Facial Artery

LYMPHATIC DRAINAGE:

• The lymphatic drain of the sinus is through the nose or the submandibular lymph nodes.
• The lymphatic drainages reaches the specialised cells in the maxillary sinus via infra orbital foramen or through the anterosuperior wall and then to the submandibular lymphatic gland.

ANATOMIC MORPHOLOGY:

• The average size of maxillary sinus in an adult is about 3.2cm depth, 3.5cm height, 2.5cm width
• In children the size increases with age as the child grows up the size changes.
• Each sinus in both maxillary has an average capacity of 15ml of fluid.
• The maxillary sinus is divided into several compartments by bony septa.
• Schnerderian Membrane:
• The maxillary sinus are lined with a specialised cells (ciliated columnar epithelium) similar to those found on the respiratory tract.
• The mucous film it secrets moves spirally and upwards against the gravity across the membrane to the opening of the sinus located on the anterior superior wall where it drain into the nasal cavity. 
• This forms the schnerderian membrane (mucosa of the nose).