Using the Sectra table, you will identify features of the orbit, ear, and nose. Bolded terms are in the objectives for this lab.
The special senses
“The orbit contains the eyeball and extraocular muscles. The eyeball is about 2.5 cm in diameter and occupies the anterior half of the orbit. The posterior half of the orbit contains fat, extraocular muscles, branches of cranial nerves, and blood vessels. Some vessels and nerves pass through the orbit to reach the scalp and face.
[…] There are two nasal cavities: right and left. The nostril (naris) is the anterior entrance to the nasal cavity. Posteriorly, each nasal cavity opens into the nasopharynx through a choana. The nasal cavity is lined by mucosa that is attached directly to the bones and cartilages. The bones and cartilages give the walls of the nasal cavity their characteristic contours. The superior one-third of the nasal mucosa is olfactory in nature, and the lower two-thirds is respiratory in nature. The nasal mucosa is highly vascular and capable of engorgement.
[…] The external ear consists of the auricle and the external acoustic meatus. The middle ear is within the tympanic cavity of the temporal bone and contains the ossicles (bones of the middle ear). The internal ear (vestibulocochlear organ) is the neurologic part of the ear and is contained within the petrous portion of the temporal bone.” – Grant’s Dissector 16th ed.
Use the following view to review the bones of the skull:
Identify the following bony features (they cannot be highlighted on the model, so use the diagrams below to find these features):
- Features of the orbit:
- Frontal bone: supraorbital notch and orbital surface
- Ethmoid bone: anterior and posterior ethmoidal foramina
- Lacrimal bone: lacrimal groove
- Maxilla: infraorbital foramen
- Zygomatic bones
- Palatine bones
- Sphenoid bone: optic canal, lesser wing, greater wing, sphenoid sinus, superior orbital fissure, and inferior orbital fissure (located between sphenoid and maxilla bones)
- Features of the ear:
- Temporal bone: internal acoustic meatus, external acoustic meatus, and stylomastoid foramen
- Ear ossicles: incus, malleus, and stapes
- Features of the oral region:
- Mandible
- Hard palate: maxillae and palatine bones
If you are having trouble highlighting narrow structures (arteries, veins, nerves), you can search for them by selecting the Anatomy tab, typing the name of the structure in the search box, and selecting the sun icon next to the listed structure. You can dissect these structures by selecting the eye icon.
As you highlight a structure, note that the structure will also be highlighted in the multiplanar reconstructed (MPR), or cross-sectional images in the leftmost pane. All structures should be identified on the MPR images. Using three fingers, scroll through the MPR images to understand the three-dimensional relationships between different structures as you work though the lab. Structures that are difficult to identify in the MPR images will have additional links to assist you.
Use the following view to work through the rest of the lab (you can select this button at any time to start over):
The orbit
- Identify and dissect the orbital and palpebral parts of the orbicularis oculi
- Dissect the left and right eyeballs and identify the common tendinous ring and the rectus muscles: inferior rectus, super rectus, medial rectus, and lateral rectus (MPR)
- Identify the oblique muscles: inferior oblique and superior oblique (the trochlea is not visible on the model. Identify it on the diagrams below)
- Identify the levator palpebrae superioris (MPR)
- In the right orbit, identify the cranial nerves of the orbit: optic nerve CN II, oculomotor nerve CN VIII, trochlear nerve CN IV, and abducent nerve CN VI. The ciliary ganglion is not visible on the model, identify them on the diagrams below (MPR)
- Branches of the ophthalmic division of the trigeminal nerve (CN V1) are not visible on the model, identify them on the diagrams below: nasociliary nerve, long ciliary nerves, anterior ethmoidal nerve, frontal nerve, supratrochlear nerve, supraorbital nerve, and lacrimal nerve
- Identify the ophthalmic artery. The central artery of the retina and ophthalmic veins are not visible on the model, identify them on the diagrams below
- Dissect the maxilla and identify the nasolacrimal duct. The lacrimal gland is not visible on the model, identify it on the diagrams below (MPR)
Q1: Describe the production and drainage of tears. (answer)
The ear
- Identify the auricular cartilage of the external ear. Other features of the external ear are not visible on the model, identify them on the model below: auricle, helix, antihelix, concha, tragus, antitragus, and lobe of auricle (MPR)
- Tympanic membrane
- Stapedius muscle & tendon and tensor tympani muscle
- Opening of pharyngotympanic tube
- Cranial nerves: facial nerve (CN VII) & chorda tympani, vestibulocochlear nerve (CN VIII), and glossopharyngeal nerve (CN IX)
Q2: Describe the path of the chorda tympani. (answer)
The nose & nasal cavity
- The cartilages of the external nose are not visible on the model, identify them on the model below
- Identify the septal cartilage, vomer, and perpendicular plate of the ethmoid bone of the nasal septum (the perpendicular plate is not labeled) (MPR)
- Identify the inferior nasal conchae. The middle and superior nasal conchae are not labeled on the model, identify them on the diagrams below and use the MPR images (particularly the coronal plane) to understand the relationship between the nasal septum, the conchae, and the meatus of each conchae
The features of the lateral wall of the nasal cavity are not visible on the model. Identify them on the diagrams below:
- Inferior meatus: opening of the nasolacrimal duct
- Middle meatus: ethmoidal bulla, opening of the middle ethmoidal cells, and opening of frontal sinus
- Semilunar hiatus: opening of the anterior ethmoidal cells
- Superior meatus: opening of the posterior ethmoidal cells and opening of maxillary sinus
- Sphenoethmoidal recess: opening of sphenoidal sinus
- The hard palate cannot be viewed clearly in the model. Identify it on the diagrams below, and use the MPR images (particularly the sagittal plane to understand the relationship between the hard palate, soft palate, and nasal and oral cavities (MPR)
- Dissect the maxilla, maxillary sinuses, and palatine bones
- Identify the tensor veli palatini and levator veli palatini muscles
- Identify the salpingopharyngeus, stylopharyngeus, palatopharyngeus, and palatoglossus muscles (MPR)
Q3: What nerves innervate the muscles of the soft palate? Which of these muscles affect the pharyngotympanic tube, and what are their actions? (answer)
The neurovasculature of the nasal cavity is not visible on the model. Identify it on the diagrams below:
- Nerves: greater palatine nerve, lesser palatine nerve, nasopalatine nerve, maxillary division of trigeminal nerve (CN V2), and glossopharyngeal nerve (CN IX)
- Arteries: greater palatine artery, lesser palatine artery, maxillary artery, sphenopalatine artery, and infraorbital artery
The oral region
- Dissect the mandible
- Identify and dissect the mylohyoid muscles, geniohyoid muscles, and the sublingual glands (MPR)
- Identify the hypoglossal nerve (CN XII) and lingual nerve (the hypoglossal nerve is incomplete on the right side of the model, and the submandibular ganglion is not visible on the model)
- Identify and dissect the body and root of the tongue
- Identify the genioglossus, hyoglossus, and styloglossus muscles (MPR)
- Identify the lingual artery on the left side (it is not visible on the right side of the model)
Q4: Describe the parasympathetic innervation of the head in relation to the ciliary and submandibular ganglia. What are the other ganglia in the head? (answer)
End of Sectra activity
Answers to activity questions
Below are answers to questions asked during the activity. Clicking the ‘back to lab’ link below each answer will take you back to the question (you may need to scroll up a little to view the question again).
Q1: Describe the production and drainage of tears.
- Tears have 3 components:
- Aqueous layer: produced by the lacrimal gland
- Lipid layer: produced by tarsal glands
- Mucous layer: produced by goblet cells
- Tears collect in the lacrimal lake in the medial part of the eye, then drain through the lacrimal puntum into the lacrimal sac. From there tears move into the nasolacrimal canal. The nasolacrimal canal opens into the inferior meatus of the nasal cavity
Q2: Describe the path of the chorda tympani.
- The chorda tympani is a branch of the facial nerve (CN VII), specifically the nervus intermedius. It enters the internal acoustic meatus, traverses the tympanic cavity (passing between the malleus and incus), and exits into the infratemporal fossa. The chorda tympani joins the lingual nerve and travels to the submandibular ganglion.
Q3: What nerves innervate the muscles of the soft palate? Which of these muscles affect the pharyngotympanic tube, and what are their actions?
- Innervation of the soft palate:
- Mandibular division of trigeminal nerve (CN V3): tensor veli palatini
- Vagus nerve (CN X) via the pharyngeal plexus: levator veli palatini, palatoglossus, palatopharyngeus, musculus uvulae
- Muscles that affect the pharyngotympanic (Eustachian) tube:
- The tensor veli palatini and levator veli palatini contract to open the phayngotympanic tube during swallowing
Q4: Describe the parasympathetic innervation of the head in relation to the ciliary and submandibular ganglia. What are the other ganglia in the head?
- Ciliary ganglion
- preganglionic axons: oculomotor nerve (CN III)
- postganglionic axons: short ciliary nerves
- target: pupillary constrictor and ciliary muscle of the eye
- Submandibular ganglion
- preganglionic axons: chorda tympani and lingual nerve
- postganglionic axons: lingual nerve or direct to oral mucosa
- target: submandibular and sublingual glands
- Other ganglia: otic, pterygopalatine