Salivary glands - Submandibular

Question 1

What type of salivary secretions does the sub-mandibular gland produce?

Answer 1

A mixed serous and mucous saliva.

Question 2

Anatomical position?

Answer 2

It is located within the anterior part of the submandibular triangle. The boundaries of the triangle are:

Superiorly - inferior body of the mandible

Anteriorly - anterior belly of the digastric muscle

Posteriorly - posterior belly of the digastric muscle

Question 3

Anatomical structure?

Answer 3

The submandibular gland is made up of two arms:

1) Superficial - comprises the greater portion of the gland and lies partially inferior to posterior half of the mandible within an impression on its medial aspect (the submandibular fossa). It is situated outside the boundaries of the oral cavity.
2) Deep - hools aroujnd the posterior margin of mylohyoid through a triangular aperture to enter the oral cavity proper. It lies on the lateral surface of the hyoglossus, lateral to the root of the tongue.

Question 4

Ducts?

Answer 4

Secretions from the gland travel into the oral cavity via the submandibular duct (Wharton’s duct). This is approximately 5cm length and emerges anteromedially from the deep arm of the gland between the mylohyoid, hypoglossus and genioglossus muscles. The duct ascends on its course to open as 1-3 orifices on a small sublingual papilla (caruncle) at the base of the lingual frenulum bilaterally.

Question 5

Relationship with nerves?

Answer 5

The submandibular duct share an intimate anatomical relationship with the follow nerves:

1) Lingual - begins lateral to the submandibular duct and then courses anteromedially by looping beneath the duct and then terminating as several medial branches. The terminal branches ascend on the external and superior surface of the hypoglossus to provide GSA innervation to the mucous membrane of the anterior 2/3 of the tongue
2) Hypoglossal - lies deep to the submandibular gland and runs superficial to hypoglossus and deep to the digastric.
3) Facial (marginal mandibular) - exits the anterior-inferior portion of the parotid gland at the angle of the jaw and traverses the margin of the mandible in the plane between platysma and the investing layer of the deep cervical fascia curving down inferior to the submandibular gland.

Question 6

Clinical relevance: submandibular gland excision?

Answer 6

It is a common procedure indicated for conditions of the submandibular gland, such as neoplasia and recurrent calculi.

As discussed previously, this gland lies in close proximity to the three principle nerves. Consequences of injuries of these nerves include:

1) Lingual - Ipsilateral paraesthesia and loss of taste on the anterior 2/3 of tongue that is rarely permanent.
2) Hypoglossal - Ipsilateral paresis or paralysis of the intrinsic muscles of the tongue - this leads to dysarthria and deviation of the tongue to one side. This is rarely damaged in this procedure.
3) Facial nerve (marginal mandibular) - ipsilateral paresis or paralysis of the muscles supplying the lower lip and the chin, including depressor labii inferioris (drooping of the lip). Usually temporary (6-12 weeks).