7 Lab 5 Oculomotor Control and Anatomy
Specific Learning Objectives
- Identify the foramina of the orbit and describe their contents.
- Identify the extraocular muscles, nerves, and blood vessels in the orbit.
- State the function and innervation of each of the extraocular muscles, including the levator palpebrae superioris muscle.
- Describe the H-test, including how it is used to isolate and test the integrity of each of the 3 cranial nerves that innervate the extraocular muscles.
- Describe the functions of the ciliary body, constrictor pupillae, dilator pupillae, superior tarsal muscle, and lacrimal gland. Outline the autonomic innervation pathway to each structure, including the locations of preganglionic and postganglionic neurons.
- Compare common clinical features associated with a lesion to cranial nerves III, IV, VI or their brainstem nuclei of origin.
Bones and Foramina of the Orbit
Review the bones and foramina of the orbit.
3 question quiz:
Extraocular muscles, movements and nerves
This first movie reviews a dissection of the orbit to demonstrate the location of structures in the orbit.
This movie focuses on details of the actions of the muscles.
Review the radiology of the orbit with this drag and drop image.
Here is a tool that allows simulation of eye position and movement after nerve damage-give it a whirl!
The palpebrae
Autonomically innervated structures of the orbit and eye
Recall the sympathetic innervation of the eye originates from the lateral horn at the T1 spinal cord level which contains the cell bodies of the pre-ganglionic neurons. These neurons synapse in the superior cervical ganglion, the most rostrally-located ganglion within the sympathetic chain. Axons of the post-ganglionic neurons form a plexus around and follow the internal carotid artery superiorly into the cranial vault. This explains why a carotid dissection may disrupt sympathetic function and may result in Horner’s syndrome.
Clinical correlate: Horner’s syndrome is the result of damage anywhere along the sympathetic pathway to the face (see image on the above). The classic triad of symptoms is mild ptosis (drooping eyelid), anhidrosis (lack of sweating), and miosis (constricted pupil) due to the decreased function of the superior tarsal muscle (a smooth muscle that assists with eyelid elevation), facial sweat glands, and the dilator pupillae, respectively.
Contrast this with the symptoms of CN III palsy—severe ptosis, “down and out” position of the pupil, and mydriasis (dilated pupil)—related to the loss of somatic motor and parasympathetic innervation. Notice how damage to one division of the autonomic nervous system shifts the balance in favor of the functional division (e.g. pupil presentation).
Lacrimal gland
Cranial Nerve Palsies affecting Eye Movements