Anatomy of the salivary glands

Chapters:

Watch video only

Introduction0:00–0:30

Have you ever smelled something so good that your mouth begins to water? Well you can thank your salivary glands for this mouth-watering sensation.
The salivary glands, while often overlooked, are a key part of our digestive system. There are three main pairs of salivary glands: the parotid, submandibular, and sublingual glands.
There are also a few smaller companions called accessory salivary glands, which are sprinkled over the palate, lips, cheeks, tonsils, and tongue.When it comes to function, salivary glands secrete saliva into the oral cavity.

Function0:30–1:04

Saliva, as you may know, is a clear, tasteless, and odorless fluid that keeps the mouth’s mucosa hydrated. Saliva also helps lubricate food while we chew, making swallowing easier, and it also starts the digestion of starch, because it contains an enzyme called amylase.
Saliva also acts as ‘nature’s mouthwash’, since it’s rich in antimicrobial compounds such as hydrogen peroxide to keep our mouths clean.
Accessory salivary glands have a similar role, except they tend to secrete less saliva.The parotid glands are the largest of the three paired salivary glands.

Parotid glands1:04–4:07

Superficially, each parotid gland is triangular in shape, where it sits upon the masseter muscle. However, most of the parotid gland actually sits in the retromandibular fossa, anteroinferior to the external acoustic meatus, where it is wedged between the the ramus of the mandible and the mastoid process and sternocleidomastoid muscle posteriorly.
Its apex is situated posterior to - or along - the angle of the mandible, while the base is associated with the zygomatic arch.
The parotid gland is surrounded by a protective sheath derived from the investing layer of the deep cervical fascia called the parotid sheath.
Now, a number of structures are closely associated with the parotid gland. First the extracranial portion of the facial nerve passes through the parotid gland and forms the parotid plexus.
Although it is embedded within the gland, the parotid plexus does not innervate it, on its way to the muscles of facial expression.
It also encloses the retromandibular vein, and the external carotid artery. The auriculotemporal nerve and superficial temporal artery can also be found traversing the superior part of the parotid gland.Another important structure associated with the parotid gland is the parotid duct which is how the saliva produced in the parotid gland gets transported to the oral cavity.
The duct passes horizontally along the parotid gland, where it reaches the anterior border of the masseter and turns medially to pierce the buccinator muscle, entering the oral cavity opposite the second maxillary molar where it releases saliva.Now, regarding nerve supply, we’ve mentioned that the parotid plexus formed by the facial nerve doesn’t innervate the parotid gland.
Instead, sensory innervation is provided by a branch of the mandibular division of the trigeminal nerve called the auriculotemporal nerve, and the great auricular nerve which is a branch of the cervical plexus.Like all glands, the parotid gland also needs parasympathetic and sympathetic innervation to ensure adequate saliva secretion.
For the parotid gland, the stimulatory parasympathetic fibers are from the glossopharyngeal nerve. The glossopharyngeal nerve sends preganglionic fibers to the otic ganglion, which is located in the infratemporal fossa, just inferior to the foramen ovale, medial to the mandibular nerve and posterior to the medial pterygoid muscle.
From the otic ganglion, the postganglionic parasympathetic fibers reach the parotid gland by hitching a ride along the fibers of the auriculotemporal nerve.
Sympathetic fibers are supplied by the superior cervical ganglion via the external carotid plexus, whose fibers travel along the external carotid artery to reach the parotid gland.
Parasympathetic innervation stimulates saliva production, while sympathetic stimulation will reduce production. Time for a quick break!

Quiz4:07–4:17

Can you recall the structures that pass through the parotid gland?Now let’s look at the submandibular glands, which are located near the posterior half of the mandible in the submandibular triangle.

Submandibular glands4:17–5:25

Each submandibular gland has a superficial and a deep lobe. The superficial lobe lies inferior to the body of the mandible and superficial to the mylohyoid muscle, while the deep lobe lies deep to the mandible and the mylohyoid muscle.
The facial artery passes deep to the submandibular gland, while the facial vein passes superficial to it. The deep lobe of the submandibular gland contacts the parotid gland posteriorly.The submandibular gland also comes with its very own submandibular duct, which is located on the medial side of the gland.
The duct starts where the gland lies between the mylohyoid and hyoglossus muscles, and then it passes from lateral to medial to meet the lingual nerve, which loops under the duct.
The duct then opens at the sublingual caruncle, on either side of the base of the frenulum of the tongue. Check out the openings of these ducts yourself by lifting up your tongue while looking in the mirror!Finally, let’s look at the sublingual glands, which are the smallest of the three pairs.

Sublingual glands5:25–6:56

Each sublingual gland is almond-shaped and lies in the floor of the oral cavity, between the mandible and the genioglossus muscle.
But this gland doesn’t like a solitary life so it unifies anteriorly with its twin from the other side of the mouth to form a horseshoe-shaped body around the connective base of the frenulum.
Its unified body has numerous sublingual ducts or ductules which open directly into the floor of the mouth. The sublingual glands are closely associated with the submandibular ducts and the lingual nerves which meet the sublingual glands medially.
Now, what about the innervation of these glands? Well, both the submandibular and the sublingual glands receive parasympathetic and sympathetic innervation from the same nerves.
Preganglionic parasympathetic fibers come from the chorda tympani nerve which is a branch of the facial nerve. The chorda tympani will then hitch a ride with the lingual nerve, which is a branch of the mandibular nerve, to head towards the submandibular ganglion.
Here, the fibers synapse with postganglionic neurons in the submandibular ganglion which lies near the third mandibular molar hanging just below the lingual nerve.
From the submandibular ganglion, some fibers continue to be carried to the glands by the lingual nerve while others travel directly to the glands.
Sympathetic fibers are provided by the superior cervical ganglion which travel through the external carotid plexus and other periarterial plexuses to these glands.Alright, as a quick recap… The parotid gland is located in the retromandibular fossa and along the masseter muscle.

Review6:56–8:15

Within the parotid gland you can find the parotid plexus of the facial nerve and its branches, the retromandibular vein, and the external carotid artery.
The parotid gland secretes saliva through the parotid duct, which opens in the oral cavity, opposite the second maxillary molar.
Parotid parasympathetic fibers are from the glossopharyngeal nerve which synapse in the otic ganglion before traveling via the auriculotemporal nerve to the parotid gland and sympathetic fibers are supplied via the external carotid plexus.
The submandibular gland has a superficial and a deep lobe that lies along either side of the mylohyoid muscle. It secretes saliva through the submandibular duct which opens in the oral cavity through the sublingual caruncle.
Finally, the sublingual glands sit in the floor of the oral cavity where numerous ductules open directly into the mouth’s floor.
Both the submandibular and the sublingual gland receive parasympathetic fibers from the chorda tympani nerve which joins and travels along the lingual nerve.
Its fibers then synapse in the submandibular ganglion before continuing to reach the glands. Sympathetic fibers are also supplied via the external