The Superior Roof of the Orbit

• The superior wall or roof of the orbit is formed almost completely by the orbital plate of the frontal bone.
• Posteriorly, the superior wall is formed by the lesser wing of the sphenoid bone.

• The roof of the orbit is thin, translucent, and gently arched. This plate of bone separates the orbital cavity and the anterior cranial fossa.

• The optic canal is located in the posterior part of the roof.

The Walls of the Orbit

• Each orbit has four walls: superior (roof), medial, inferior (floor) and lateral.
• The medial walls of the orbit are almost parallel with each other and with the superior part of the nasal cavities separating them.
• The lateral walls are approximately at right angles to each other

The Pharynx

• The pharynx is the continuation of the digestive system from the oral cavity.
• It is a funnel-shaped fibromuscular tube that is the common route for both food and air.
• The pharynx is located posterior to the nasal and oral cavities, and the larynx.

• For the convenience of description, the pharynx is divided into three parts: (1) the nasopharynx, posterior to the nose and superior to the soft palate; (2) the oropharynx, posterior to the mouth; and (3) the laryngopharynx, posterior to the larynx.

• The pharynx is about 15 cm long.
• It extends from the base of the skull to the inferior border of the cricoid cartilage anteriorly, and to the inferior border of C6 vertebra posteriorly.
• It is widest (about 5 cm) opposite the hyoid bone and narrowest (about 1.5) at its inferior end, where it is continuous with the oesophagus.

• The posterior wall of the pharynx lies against the prevertebral fascia, with the potential retropharyngeal space between them.

The Meatus of the Nose

Sphenopalatine Recess

• This space is posterosuperior to the superior concha.
• The sphenoidal sinus opens into this recess.

Superior Meatus

• This is a narrow passageway between the superior and middle nasal conchae.
• The posterior ethmoidal sinuses open into it by one or more orifices.

Middle Meatus

• This is longer and wider than the superior one.

• The anterosuperior part of this meatus lead into a funnel-shaped opening, called the infundibulum, through which the frontonasal duct leads to the frontal sinus.
• There is one duct for each frontal sinus and since there may be several, there may be several frontonasal ducts.

• When the middle concha is removed, rounded elevation called the ethmoidal bulla (L. bubble), is visible
• The middle ethmoidal air cells open on the surface of the ethmoidal bulla.

• Inferior to this bulla is a semicircular groove called the hiatus semilunaris.
• The frontal sinus opens into this hiatus anterosuperiorly.
• Near the hiatus are the openings of the anterior ethmoid air cells.
• The maxillary sinus also opens into the middle meatus.

Inferior Meatus

• This is a horizontal passage, inferolateral to the inferior nasal concha.
• The nasolacrimal duct opens into the anterior part of this meatus.
• Usually, the orifice of this duct is wide and circular.

The Orbital Vessels

• The orbital contents are supplied chiefly by the ophthalmic artery.
• The infraorbital artery, the continuation of the maxillary, also contributes blood to this region.
• Venous drainage is through the superior orbital fissure to enter the cavernous sinus.

The Ophthalmic Artery

• This artery arises from the internal carotid artery as it emerges from the cavernous sinus.
• It passes through the optic foramen within the dural sheath of the optic nerve and runs anteriorly, close to the superomedial wall of the orbit.

The Central Artery of the Retina

• This is the one of the smallest but most important branches of the ophthalmic artery.
• It arises inferior to the optic nerve until it approaches the eyeball.
• It then pierces the optic nerve and runs within it to emerge through the optic disc.
• The central artery of the retina spreads over the internal surface of the retina and supplies it.

The Ophthalmic Veins

The Superior Ophthalmic Vein

• The superior ophthalmic vein anastomoses with the facial vein.
• It has no valves and blood can flow in either direction.
• It crosses superior to the optic nerve, passes through the superior orbital fissure and ends in the cavernous sinus.

The Inferior Ophthalmic Vein

• This begins as a plexus on the floor of the orbit.
• It communicates with the inferior orbital fissure with the pterygoid plexus, crosses inferior to the optic nerve, and ends in either the superior ophthalmic vein or the cavernous sinus.

Muscles acting on the Temporomandibular Joint

• Movements of the temporomandibular joint are chiefly from the action of the muscles of mastication.
• The temporalis, masseter, and medial pterygoid muscles produce biting movements.
• The lateral pterygoid muscles protrude the mandible with the help from the medial pterygoid muscles and retruded largely by the posterior fibres of the temporalis muscle.
• Gravity is sufficient to depress the mandible, but if there is resistance, the lateral pterygoid, suprahyoid and infrahyoid, mylohyoid and anterior digastric muscles are activated.