H and N 1.9 Flashcards
What is the size of the parotid gland?
The parotid salivary gland is the largest of the 3 paired salivary glands
What is the journey of the parotid gland?
The parotid duct passes horizontally from the gland, pierces the buccinator muscle, and enters the oral cavity opposite the 2nd maxillary molar tooth
Where does the fascial nerve exit?
The facial nerve (CN VII) exits through the stylomastoid foramen, passes through the parotid gland, and distributes its 5 terminal branches over the face
What are the 5 terminal branches of the facial nerve?
- Temporal
- Zygomatic
- Buccal
- Marginal Mandibular
- Cervical branches
Why is surgery of parotid gland dangerous?
Surgery involving the parotid gland (tumor resection) or trauma to this region of the face places the terminal motor branches of the facial nerve (CN VII) in jeopardy, which could result in paralysis or weakness to 1 or more of the facial muscles.
What can a stone cause?
A stone (calculus) may occlude the parotid (Stensen’s) duct, necessitating its removal
What is the parotid gland innervate by?
innervated by the glossopharyngeal nerve (CN IX) via preganglionic parasympathetic fibers that course to the otic ganglion via the lesser petrosal nerve, synapse in the ganglion, and send postganglionic fibers to the gland via the auriculotemporal branch of CN V3
What does the lacrimal apparatus consist of?
lacrimal glands, which secrete tears, and a system of collection ducts
What do lacrimal ducts do?
Lacrimal ducts convey tears from the glands to the conjunctival sac, and the lacrimal canaliculi drain them into the lacrimal sac
Where to tears drain?
drain down the nasolacrimal duct and empty into the inferior nasal meatus behind the inferior nasal concha
How are tears produced?
- Under parasympathetic autonomic control exerted by nerve fibres that originate in the facial nerve (CN VII)
- And ultimately reach the glands via the lacrimal nerve a brach of the ophthalmic division of the trigeminal nerve
What is the plica semilunaris?
The human plica semilunaris is our remnant of the nictitating membrane (a 3rd eyelid that is transparent), seen in many other vertebrates, especially birds, reptiles, and some mammals
What do tears contain?
- albumins
- lactoferrin
- lysozyme
- lipids
- metabolites
- ectrolytes
- provide a protective layer of fluid that helps keep the cornea moist and protected from infection
What is dry eye?
Dry eye (insufficient tear production) is not uncommon and can be treated with lubricating moisturizing eyedrops or systemically with prescription medications
What are the three layers of the eyeball?
- an external fibrous layer consisting of the sclera and transparent cornea
- a middle vascular pigmented layer consisting of the choroid, ciliary body, and iris;
- an internal neural layer, the retina
What is the fovea centralis?
- The fovea centralis, a central depression in the macula, is an avascular region that contains cones but no rods
- This area provides the most acute vision.
How does light travel?
Light passes to the retina through the refractive media of the eye, which consists of the cornea, aqueous humor, lens, and vitreous humor
What is cataract?
- An opacity of the lens
- treatment involves surgically removing the lens and implanting a plastic lens and then correcting the vision with glasses
What is glaucoma?
- An increase in ocular pressure usually due to poor reabsorption fo aqueous humour
- This increased pressure may damage the retina
What is the region of the eyeball (globe) between the zonular fibres and the iris?
The posterior chamber
How does the posterior chamber communicate?
by an opening in the iris (the pupil), with the anterior chamber lying between the iris and the cornea
What does. the. aqueous humour do?
Aqueous humor, continuously produced by the ciliary process of the ciliary body, fills these 2 chambers and is absorbed into the trabecular meshwork and scleral venous sinus.
What do the dilator and sphincter muscles (smooth muscles) of the iris do?
Account for dilation and constriction of the pupillary opening
What does contraction of the ciliary muscles (circular fibres) do?
Contraction of the ciliary muscle (circular fibers) has a sphincteric action on the ciliary body such that the zonular fibers relax and the elastic lens becomes more rounded in shape, leading to accommodation for focusing on objects close to the eye.
