Levator Palpebrae Superioris Muscles

• This is a thin, triangular muscle that elevates the upper eyelid.
• It is continuously active except during sleeping and when the eye is closing.

• Origin: roof of orbit, anterior to the optic canal.
• Insertion: this muscle fans out into a wide aponeurosis that inserts into the skin of the upper eyelid. The inferior part of the aponeurosis contains some smooth muscle fibres that insert into the tarsal plate.
• Innervation: the superior fibres are innervated by the oculomotor nerve (CN III), and the smooth muscle component is innervated by fibres of the cervical sympathetic trunk and the internal carotid plexus.

Illnesses involving the Levator Palpebrae Superioris

• In third nerve palsy, the upper eyelid droops (ptosis) and cannot be raised voluntarily.
• This results from damage to the oculomotor nerve (CN III), which supplies this muscle.

• If the cervical sympathetic trunk is interrupted, the smooth muscle component of the levator palpebrae superioris is paralysed and also causes ptosis.
• This is part of Horner's syndrome.

The Rectus Muscles

• There are four rectus muscles (L. rectus, straight), superior, inferior, medial and lateral.

• These arise from a tough tendinous cuff, called the common tendinous ring, which surrounds the optic canal and the junction of the superior and inferior orbital fissures.
• From their common origin, these muscles run anteriorly, close to the walls of the orbit, and attach to the eyeball just posterior to the sclerocorneal junction.

• The medial and lateral rectus muscles attach to the medial and lateral sides of the eyeball respectively, on the horizontal axis.
• However, the superior rectus attaches to the anterosuperior aspect of the medial side of the eyeball while the inferior rectus attaches to the anteroinferior aspect of the medial side of the eye.

The Oblique Muscles

The Superior Oblique Muscle

• This muscle arises from the body of the sphenoid bone, superomedial to the common tendinous ring.
• It passes anteriorly, superior and medial to the superior and medial rectus muscles.
• It ends as a round tendon that runs through a pulley-like loop called the trochlea (L. pulley).
• After passing though the trochlea, the tendon of the superior oblique turns posterolaterally and inserts into the sclera at the posterosuperior aspect of the lateral side of the eyeball.

The Inferior Oblique Muscle

• This muscle arises from the maxilla in the floor of the orbit.
• It passes laterally and posteriorly, inferior to the inferior rectus muscle.
• It inserts into the sclera at the posteroinferior aspect of the lateral side of the eyeball.

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.

The Inferior Wall of the Orbit

• The thin inferior wall of the orbit or the floor is formed mainly by the orbital surface of the maxilla and partly by the zygomatic bone, and orbital process of the palatine bone.

• The floor of the orbit forms the roof of the maxillary sinus.

• The floor is partly separated from the lateral wall of the orbit by the inferior orbital fissure.

Movements of the Temporomandibular Joint

• The two movements that occur at this joint are anterior gliding and a hinge-like rotation.
• When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.

• As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc.
• This permits simple chewing or grinding movements over a small range.

• Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding

• This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
• The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
• It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).

• The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.

• During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.

• Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.

• The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
• This aponeurosis attaches to the posterior margin of the hard palate.

The Temporomandibular Joint

• This articulation is a modified hinge type of synovial joint.
• The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.

• An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.

• The articular disc is more firmly bound to the mandible than to the temporal bone.

• Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle