• • Anterior & posterior ethmoidal foramina

    • Anterior & posterior ethmoidal neurovasculature

• • Lacrimal fossa

    • Nasolacrimal sac

2. What is the parasympathetic pathway for the lacrimal gland?

Anatomists have classically understood (and taught) that the secretomotor postganglionic fibers to the lacrimal gland were conducted by the lacrimal n. from fibers transmitted from the pterygopalatine ganglion via the zygomaticotemporal brs. (i.e. pterygopalatine ganglion → zygomaticotemporal brs. → lacrimal n. → lacrimal gland). Recent studies show considerable variation in the course of these fibers, with the majority of cases demonstrating secretomotor postganglionic fibers from the pterygopalatine ganglion directly innervating the lacrimal gland via the zygomaticotemporal brs. Variants do exist that reflect the ‘classical condition.’

3. What are the three parts of the eyeball? Describe the supporting apparatus of the eyeball and its various components.

The fibrous layer of the eye is important in providing structure and strength to the eyeball. This layer consists of the sclera and cornea. The sclera covers the majority of the eyeball, is often referred to as the “white of the eye.” It is the insertion site for extra-ocular and intrinsic eye muscles. The cornea covers the anterior portion of the eye (approximately ⅙th of the anterior eye - Moore et al., 7th edition), is completely avascular, sensitive to touch, and is the main refractive index of the eye.

The vascular layer of the eye (uvea) is composed of 3 structures: choroid, ciliary body, and iris. The iris is a diaphragm located on the anterior surface of the lens. The pupil, an aperture important in transmitting light, is located centrally in the iris. The iris is the portion of the uvea with color, while the pupil is black. The pupil is controlled by two muscles: sphincter pupillae (contracts pupil, parasympathetically-controlled) and dilator pupillae (dilates pupil, sympathetically-controlled).

The inner (nervous) layer of the eye is composed of the neural retina. The retina is composed of 10 layers that contain specialized receptors (rods and cones) as well as interneurons, glia, and ganglion cells. The axons of the ganglion cells exit the retina as the optic n. (CN II). The main source of blood supply to the retina is the central retinal a., which travels within the optic n. to the retina, and is a branch of the ophthalmic a.

4. What are the extra-ocular muscles of the eye and their attachments? What are the actions of these muscles? What nerves innervate these muscles?

Extra-ocular muscles separated by eye movements

The distal tendon of the superior oblique m. runs through the trochlea, a fibrocartilaginous loop (pulley) that attaches to the trochlear fossa of the frontal bone, before inserting on the posterosuperior sclera of the eye.

The common anular tendon (common tendinous ring) is the origin site for the rectus muscles. The ring encircles the optic n. (CN II), oculomotor n. (CN III), and abducens n. (CN VI).

5. What are the nerves that provide autonomic innervation to the orbit and its content?

Long ciliary nn.

The long ciliary nerves arise from the nasociliary n. (V1) in the vicinity of the optic n. (CN II). These branches carry postganglionic sympathetic fibers to the dilator pupillae muscle of the eye.

Oculomotor n. (CN III)

The oculomotor n. (CN III) arises from the midbrain, travels within the lateral wall of the cavernous sinus, divides into superior and inferior divisions, and these divisions enter the orbit through the superior optic fissure (and also through the common anular tendon). The superior and inferior divisions are typically separated by the nasociliary n. (of V1) and the optic n. (CN II).

The inferior division of oculomotor n. transmits preganglionic parasympathetic fibers to:

• • ciliary ganglion (for sphincter pupillae muscles and ciliary muscles)

Short ciliary nn.

The short ciliary nn. transmit three types of fibers between the eye and the ciliary ganglion:

• • afferent fibers from the eye, through the ganglion, to the nasociliary n. (V1),

    • postganglionic parasympathetic fibers from the ganglion (preganglionics from oculomotor) to the ciliary muscles and sphincter pupillae muscles, and

    • postganglionic sympathetic fibers (from perivascular plexuses) to the intra-ocular vessels.

Ciliary ganglion

The ciliary ganglion is a peripheral parasympathetic ganglion for intra-ocular muscles, typically located on the lateral aspect of the optic n. (CN II) near the apex of the orbit. The ciliary ganglion has three conduits to/from the remainder of the PNS:

• • nasociliary n. (of V1) - transmits afferent fibers from the eye through the ganglion to the nasociliary n.,

    • oculomotor n. (CN III) - transmits preganglionic parasympathetic fibers to the ciliary ganglion, and

    • sympathetic - postganglionic sympathetic fibers are transmitted to (and through) the ciliary ganglion from perivascular plexuses of the internal carotid a. These fibers may also associate with the oculomotor n.

The ciliary ganglion communicates with the eye via the short ciliary nn.

6. What are the conchae and meatuses of the lateral nasal wall? What spaces communicate via each meatus?

The superior and middle nasal conchae (turbinates) are scroll-shaped components of the ethmoid bone located on the lateral wall of the nasal cavity. The superior nasal concha is the smallest with the middle concha of intermediate size. The inferior nasal concha is the largest and most substantial of the nasal conchae, and are not components of another bone. Occasionally, there are highest (supreme) nasal conchae, within the sphenoethmoidal recess. The nasal conchae are thickly lined with nasal mucosa, and serve several functions: increase surface area of nasal cavity, humidification and filtration of inspired air, and direction of airflow.

There are four meatuses or recesses associated with the nasal conchae, the:

• • spheno-ethmoidal recess is located superior to the superior nasal concha,

  • superior nasal meatus can be found between the superior and middle nasal conchae,

  • middle nasal meatus is located between the middle and inferior nasal conchae,

  • inferior nasal meatus can be identified below the inferior nasal concha.

The spheno-ethmoidal recess is located above the superior nasal concha, and the opening of the sphenoidal sinus is located here.

The superior nasal meatus is located between the superior and middle nasal conchae. The openings of the posterior ethmoidal cells are located in the superior nasal meatus.

The middle nasal meatus is located between the middle and inferior nasal conchae. The openings of several sinuses are found in the middle nasal meatus (middle ethmoidal cells, frontal sinus, maxillary sinus, and anterior ethmoidal cells).

Within the middle nasal meatus, there are several important structures. The ethmoidal bulla is a noticeable projection just inferior to the middle nasal concha, caused by the middle ethmoidal cells. Inferior to the bulla is a slit-like opening, the semilunar hiatus. The anterosuperior portion of the semilunar hiatus expands into a funnel-shaped opening, the ethmoidal infundibulum. The frontonasal duct of the frontal sinus typically drains into the ethmoidal infundibulum, while the semilunar hiatus hosts openings for the anterior ethmoidal cells and maxillary sinus.

The inferior nasal meatus can be identified below the inferior nasal concha, and contains the opening of nasolacrimal duct, which conducts tears from the orbit.

7. Describe the innervation and vasculature of the nasal cavity.

Nasal septum (medial wall of nasal cavity):

The nasal septum receives vasculature from three general sources:

• • superiorly, from the anterior ethmoidal a. (via anterior septal brs.) and the posterior ethmoidal a.,

  • posteriorly from the sphenopalatine a. (via posterior septal brs.), and

  • anteriorly from the superior labial a. (via nasal septal brs.) and greater palatine a.

These arteries come from the ophthalmic a. (anterior & posterior ethmoidal aa.), maxillary a. (sphenopalatine & greater palatine aa.), and the facial a. (superior labial a.). The arteries of the nasal septum anastomose on the anterior aspect of the septum, and area known as the Kiesselbach’s area/plexus. A preponderance (>90%) of episodes of epistaxis (‘nose bleed’) originate in Kiesselbach’s area.

The nasal septum is innervated by branches of V1 and V2.

V1 supplies the septum through:

• • medial nasal brs. (from internal nasal brs. of the anterior ethmoidal n.), whereas

V2 supplies the septum through:

• • nasopalatine n., and the

  • posterior superior medial nasal brs.

Most of the nasal septum is innervated by nasopalatine n. A small part of the nasal roof and superior portion of the septum is innervated by the posterior superior medial nasal brs. The anterior portion of the nasal septum is innervated by medial nasal brs. (of internal nasal brs. of the anterior ethmoidal n.).

One of the more obvious contributions of neurovasculature to the nasal septum is the collection of olfactory nn. (CN I). The olfactory nn. can be located descending inferiorly from the cribriform foramina of the ethmoid bone.

Lateral wall of nasal cavity:

The lateral nasal wall is served by branches of the same arteries which serve the nasal septum, namely the:

• • anterior ethmoidal (via anterior lateral nasal brs.) & posterior ethmoidal aa.,

  • sphenopalatine a. (via posterior lateral nasal aa.), and the

  • facial a. (via lateral nasal br.).

The lateral nasal wall is innervated by branches of V1 and V2 that also serve the nasal septum.

V1 supplies the lateral wall through:

• • lateral nasal brs. (from internal nasal brs. of the anterior ethmoidal n.), whereas

V2 supplies the lateral wall through:

• • posterior superior lateral nasal brs.,

  • posterior inferior lateral nasal brs. (from greater palatine n.),

  • nasal brs. of the anterior superior alveolar n., and

  • internal nasal br. of the infra-orbital n.

The mid- to posterior aspects of the lateral nasal wall are innervated by posterior superior lateral nasal brs. and posterior inferior lateral nasal brs. (from greater palatine n.). Posterior superior lateral nasal brs. innervate the superior and middle nasal meatuses, whereas the posterior inferior lateral nasal brs. innervate the middle and inferior nasal meatuses. The anterior aspect of the lateral wall is innervated superiorly by lateral nasal brs. (from internal nasal brs. of the anterior ethmoidal n.) and inferiorly by nasal brs. (of the anterior superior alveolar n.) and internal nasal brs. (of the infra-orbital n.).

8. What are the walls/boundaries of the pterygopalatine fossa? What are the major structures located (or traveling through) this fossa?

The pterygopalatine fossa is a space located between the nasopharynx (medially) and the infratemporal fossa (laterally). Its boundaries include:

• • Lateral: pterygomaxillary fissure

  • Medial: palatine bone

  • Anterior: posterior wall of maxilla

  • Posterior: anterior surface of greater wing of sphenoid

    • Two openings: foramen rotundum and pterygoid canal

  • Roof: body of sphenoid

Contents of the pterygopalatine fossa include:

• • Maxillary n. (V2) and branches

  • Pterygopalatine ganglion

  • 3rd part of maxillary a. and branches

The pterygopalatine fossa communicates with:

• • Orbit: via the inferior orbital fissure

  • Oral cavity: via the greater & lesser palatine canals

  • Nasal cavity: via the sphenopalatine foramen

  • Infratemporal fossa: via the pterygomaxillary fissure

A pathway from the infratemporal fossa (lateral) to the sphenopalatine foramen (medial) can be succinctly described as:

Infratemporal fossa → Pterygomaxillary fissure → Pterygopalatine fossa → Sphenopalatine foramen

9. What are the three divisions of the maxillary artery?

The maxillary a. is one of the two terminal divisions of the external carotid a., and distributes blood flow to the upper maxilla and lower mandible, deep facial areas, the middle ear, cerebral dura mater, and the nasal cavity. It is considered a blood vessel which supports both hard and soft tissue in the maxillofacial region.

The main trunk of the maxillary a. is divided into three parts, which are named according to related structures along the artery’s course (path of travel).