Submandibular Gland

 Where is submandibular gland Located and what are its dimensions?

Submandibular gland is a mixed type of gland (contains both mucous and serous acini) but is predominantly serous in nature.

Location:  It is located in the anterior part of digastric triangle partly deep  in the submandibular fossa of mandible and partly below the mandible.

Size and shape: It is of the size of a walnut and weighs approx.10-20gms.

What are the parts of submandibular gland?

Parts: It consists of two parts:

• Large superficial part: It fills the anterior part of digastric triangle and lies superficial to mylohyoid muscle.
• Smaller deep part: It lies deep to mylohyoid.  It is continuous with the superficial part around the free posterior margin of mylohyoid.

Describe the Gross Features and Relations of Submandibular Gland

Superficial part of submandibular gland fills the anterior part of digastric triangle and extends upwards deep to mandible till the mylohyoid line. It has three surfaces i.e. superficial (inferior), lateral and medial.

Relations of Superficial Surface

Superficial (inferior) surface is covered by the following structures from superficial to deep:

• Skin
• Superficial fascia containing platysma and marginal mandibular branch of facial nerve
• Investing layer of deep cervical fascia
• Facial vein
• Submandibular lymph nodes

Relations of lateral Surface

Lateral surface is related to:

• Submandibular fossa of mandible
• Medial pterygoid muscle
• Facial artery

Relations of Medial Surface

Medial surface: can be divided into three parts:

Anterior part is related to:

• Mylohyoid muscle
• Mylohyoid nerve and vessels
• Submental artery

Middle part is related to:

• Hyoglossus muscle
• Lingual nerve
• Submandibular ganglion
• Hypoglossal nerve

Posterior part is related to:

• Styloglossus muscle
• Middle constrictor of pharynx
• Glossopharyngeal nerve
• Stylohyoid ligament

Deep part of submandibular gland:It lies on the hyoglossus muscle deep to mylohyoid. Anteriorly it extends up to the sublingual gland and posteriorly it is continuous with the superficial part.

Submandibular (Wharton’s) duct

• Submandibular duct is 5cm. long
• It begins on the medial surface of superficial part (at the posterior border of mylohyoid).
• It enters deep part and then emerges from the anterior end of deep part.
• It thend runs forwards on hyoglossus  muscle & is crossed by lingual nerve from lateral to medial side).
• It continues forwards and upwards between the genioglossus  muscle and sublingual gland.
• It opens in the floor of mouth at the summit of sublingual papilla lateral to frenulum of tongue.

Describe the Nerve Supply of submandibular Gland.

Submandibular gland is supplied by branches from submandibular ganglion carrying following fibers:

• parasympathetic (secretomotor),
• sympathetic and
• sensory fibers.

Parasympathetic (Secretomotor) fibers:  Preganglionic fibers originate from superior salivatory nucleus in pons. they pass successively through the facial nerve and a branch of facial nerve viz. chorda tympani. Chorda tympani joins lingual nerve and the fibers relay/synapse in submandibular ganglion. Postganglionic fibers arise from the ganglion and supply the submandibular gland.

Sympathetic fibers: Preganglionic fibers originate from the lateral horn of T1 spinal segment, relay in superior cervical sympathetic ganglion and the postganglionic fibers form plexus around facial artery and supply submandibular gland.

Sensory fibers arise from the lingual branch of mandibular nerve.

*Parasympathetic stimulation generates watery secretion (rich in enzymes), whereas the sympathetic  fibers stimulate secretion that has more of mucus. Sympathetic supply is also vasomotor.

Applied Aspects