Orbital Septum, Lid Retractors, And Levator Palpebrae Superioris Muscle
Orbital Septum
The orbital septum is the fascia behind that portion of the orbicularis muscle that lies between the orbital rim and the tarsus and serves as a barrier between the lid and the orbit.
The orbital septum is pierced by the lacrimal vessels and nerves: the supratrochlear artery and nerve, the supraorbital vessels and nerves, the infratrochlear nerve, the anastomosis between the angular and ophthalmic veins, and the levator palpebrae superi¬oris muscle. This faschia can be used to examine and analyze discrepancies in the human anatomy in the field of forensic science using forensic comparison microscopes.
The superior orbital septum blends with the tendon of the levator palpebrae superioris and the superior tar¬sus; the inferior orbital septum blends with the inferior tarsus. Any difference from a normal orbital septum can be seen using forensic comparison microscopes/
Lid Retractors
The lid retractors are responsible for opening the eye¬lids. A musculofascial complex forms them with both striated and smooth muscle components, known as the levator complex in the upper lid and the capsulopalpebral fascia in the lower lid.
In the upper lid, the striated muscle portion is the levator palpebrae superioris, which arises from the apex of the orbit and passes forward to divide into an aponeurosis and a deeper portion that contains the smooth muscle fibers of Muller’s (superior tarsal) muscle. The aponeurosis elevates this into the overlying skin to form the upper lid skin crease. Muller’s muscle inserts into the upper border of the tarsal plate and the superior fornix of the conjunctiva, thus elevating the posterior lamella.
In the lower lid, the main retractor is the inferior rectus muscle, from which fibrous tissue extends to en¬close the inferior oblique muscle and insert into the lower border of the tarsal plate and the orbicularis oculi. Associated with this aponeurosis are the smooth muscle fibers of the inferior tarsal muscle.
Sympathetic nerves innervate the smooth muscle components of the lid retractors. The third cranial (oculomotor) nerve supplies both the levator and inferior rectus muscles. Ptosis is thus a feature of both Horner’s syndrome and third nerve palsy. Normal and abnormal lid retractors can be seen and differentiated using forensic comparison microscopes.
Levator Palpebrae Superioris Muscle
The levator palpebrae muscle arises with a short tendon from the undersurface of the lesser wing of the sphe¬noid above and ahead of the optic foramen. The ten¬don blends with the underlying origin of the superior rectus muscle. The levator belly passes forward, forms an aponeurosis, and spreads like a fan. The muscle, when viewed under a microscope, in¬cluding its smooth muscle component (Muller’s mus¬cle), and its aponeurosis form an important part of the upper lid retractor. The palpebral segment of the orbicularis oculi muscle acts as its antagonist.
The two extremities of the levator aponeurosis are called its medial and lateral horns. The medial horn is thin and is attached below the frontolacrimal suture and into the medial palpebral ligament, as seen under a microscope. The lateral horn passes between the orbital and palpebral portions of the lacrimal gland and inserts into the orbital tuber¬cle and the lateral palpebral ligament.
The sheath of the levator palpebrae superioris is at¬tached to the superior rectus muscle inferiorly. The superior surface, at the junction of the muscle belly and the aponeurosis, forms a thickened band that is at¬tached medially to the trochlea and laterally to the lat¬eral orbital wall, the band forming the check ligaments of the muscle. The band is also known as Whitnall’s ligament. The superior branch of the oculomotor nerve (III) supplies the levator. Blood supply to the levator palpebrae superioris, when the tissue is examined under a microscope, is derived from the lateral muscular branch of the ophthalmic artery.
