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AN34.1-3 | Submandibular region — Gate Quiz
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The mylohyoid muscle forms the muscular floor (diaphragm) of the mouth. It separates:
Correct! The mylohyoid muscle is the musculodiaphragm of the floor of the mouth. It separates the sublingual space (above, where the sublingual gland and deep part of the submandibular gland lie) from the submandibular space (below, where the superficial part of the submandibular gland lies).
Mylohyoid origin: mylohyoid line of mandible. Insertion: median fibrous raphe + hyoid body. Function: floor of mouth diaphragm; elevates the hyoid + floor of mouth; assists swallowing. Nerve: mylohyoid nerve (branch of inferior alveolar, CN V3).
Incorrect. Mylohyoid forms the floor of the mouth, separating the sublingual space (above) from the submandibular space (below). This is critical in understanding how Ludwig's angina spreads from one space to the other.
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Wharton's duct (the submandibular duct) opens into the oral cavity at:
Correct! Wharton's duct opens at the sublingual papilla (caruncula sublingualis) — a small papilla beside the lingual frenulum at the floor of the mouth.
Salivary duct openings: Parotid (Stensen's) → opposite upper 2nd molar (parotid papilla). Submandibular (Wharton's) → sublingual papilla beside frenulum. Sublingual (Rivinus' ducts) → along the sublingual fold or into Wharton's duct.
Incorrect. Wharton's duct (submandibular duct) opens at the sublingual papilla beside the frenulum. Stensen's duct (parotid) opens at the parotid papilla opposite the upper second molar.
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Parasympathetic secretomotor fibres to the submandibular gland relay in the submandibular ganglion. The preganglionic fibres reach the ganglion via:
Correct! CN VII → chorda tympani (leaving the facial canal through the petrotympanic fissure) → joins the lingual nerve in the infratemporal fossa → travels to the submandibular ganglion. Postganglionic fibres supply the submandibular and sublingual glands.
Parasympathetic supply of major salivary glands: Parotid — CN IX → lesser petrosal nerve → otic ganglion → auriculotemporal nerve. Submandibular + sublingual — CN VII → chorda tympani → lingual nerve → submandibular ganglion. Lacrimal — CN VII → greater petrosal → pterygopalatine ganglion.
Incorrect. Submandibular gland parasympathetic: CN VII → chorda tympani → lingual nerve → submandibular ganglion → postganglionic fibres to submandibular + sublingual glands. The lesser petrosal nerve and otic ganglion supply the parotid gland via CN IX.
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Which of the following anatomical/physiological factors MOST explains why 80% of salivary calculi form in the submandibular gland?
Correct! Three converging factors make the submandibular gland/duct stone-prone: (1) Wharton's duct is long (5 cm) and tortuous, running upward against gravity (stasis). (2) Saliva is more mucous and viscous. (3) Higher pH (alkaline) and higher calcium concentration → calcium phosphate precipitation.
Sialolithiasis predisposition in submandibular: (1) Duct anatomy — 5 cm, tortuous, runs against gravity. (2) Saliva — more mucous, higher pH (alkaline), higher calcium. (3) Narrow segment as duct wraps around mylohyoid. These three factors create stasis + favourable conditions for calcium salt precipitation.
Incorrect. The parotid is actually the largest salivary gland. The key reason for submandibular stones is the combination of: upward-running tortuous long duct (stasis) + alkaline, mucous, calcium-rich saliva (favours precipitation).
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Ludwig's angina originates from a lower molar periapical abscess and rapidly spreads to involve the submandibular, submental, and sublingual spaces bilaterally. The primary anatomical route for spread from the submandibular to the sublingual space is:
Correct! The posterior free border of the mylohyoid is the route by which infection (and the deep part of the submandibular gland) passes from the submandibular space (below) into the sublingual space (above). Once in the sublingual space, it can cross the midline and extend bilaterally.
Ludwig's angina spread: Lower molar abscess → submandibular space → around posterior mylohyoid border → sublingual space → bilateral spread → tongue elevation → airway obstruction. The posterior border of mylohyoid is the key anatomical gateway.
Incorrect. Infection spreads from submandibular → sublingual space around the posterior free border of the mylohyoid muscle (the gap through which the deep part of the gland and its duct pass). Not via skin or lymphatics.
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The lingual nerve crosses Wharton's duct in the floor of the mouth. How many times does this crossing occur?
Correct! The lingual nerve crosses Wharton's duct twice: first passing from lateral to medial (under the duct) at the posterior floor of the mouth, then again from medial to lateral (back above the duct) near the anterior sublingual region. This double crossing is critical knowledge for duct stone surgery.
Lingual nerve and Wharton's duct: At the posterior floor — lingual nerve is lateral and above. It then dips below (medial to) the duct in the mid-floor. At the anterior floor — it emerges medial to and then below the duct. Two crossings total. At risk in both stone extraction and gland excision.
Incorrect. The lingual nerve crosses Wharton's duct TWICE in a characteristic pattern — making it vulnerable to injury during intraoral stone removal. A memory aid: "the lingual nerve wraps around the submandibular duct like a swinging door."
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The hypoglossal nerve (CN XII) supplies all intrinsic and extrinsic muscles of the tongue EXCEPT:
Correct! Palatoglossus is the only tongue muscle NOT supplied by CN XII. It is supplied by the **vagus nerve (CN X)** via the pharyngeal plexus, reflecting its pharyngeal (branchial arch) origin rather than lingual (occipital somite) origin.
CN XII (hypoglossal): supplies all intrinsic tongue muscles (superior/inferior longitudinal, transverse, vertical) + all extrinsic muscles (genioglossus, hyoglossus, styloglossus) EXCEPT palatoglossus (CN X). Clinical: CN XII LMN palsy → tongue deviates to the affected side on protrusion.
Incorrect. CN XII supplies all tongue muscles EXCEPT palatoglossus, which is supplied by CN X (via pharyngeal plexus). Palatoglossus has a pharyngeal origin and function — it elevates the back of the tongue during swallowing.
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During submandibular gland excision, the facial artery is routinely ligated. Its relationship to the gland is:
Correct! The facial artery typically grooves — and sometimes actually passes through — the posterior surface of the superficial part of the submandibular gland before hooking around the inferior border of the mandible at the anterior edge of the masseter. This intimate relation requires careful ligation during gland excision.
Facial artery route: ECA → loops under posterior belly of digastric → grooves/passes through submandibular gland → hooks over inferior border of mandible at anterior masseter border → continues as the facial artery of the face. The facial artery is ligated at two points during gland excision.
Incorrect. The facial artery passes through or deeply grooves the posterior surface of the submandibular gland. This is why the surgeon must ligate the facial artery at the inferior border of the mandible and at the lower pole of the gland during submandibular gland excision.
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A patient complains of pain and swelling under the jaw that begins within minutes of starting a meal and gradually resolves over 30–60 minutes. Which pathological process best explains this pattern?
Correct! Eating stimulates salivary flow. A stone obstructing Wharton's duct blocks saliva outflow, causing the gland to swell (obstructive sialadenitis). As saliva is gradually reabsorbed or trickles past the stone, the swelling and pain subside. This "meal-time swelling" is the pathognomonic presentation of sialolithiasis.
Sialolithiasis presentation: meal-time pain and swelling (salivary colic). Stimulus (food sight/smell/taste) → reflex salivation → stone blocks outflow → gland distends → pain. Subsides as saliva reabsorbs. Location under jaw = submandibular. Bimanual palpation to feel the stone in the duct.
Incorrect. The meal-time swelling (saliva wave blocked by stone → gland distension → pain) is the classic, pathognomonic presentation of salivary duct obstruction by a calculus. Given the submandibular location (under the jaw), this is most likely Wharton's duct stone.
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During excision of the submandibular gland through an incision 2 cm below the inferior border of the mandible, the surgeon is most concerned about injuring which nerve during the skin incision and superficial dissection?
Correct! The marginal mandibular branch of CN VII runs in the investing fascia just below the inferior border of the mandible (or even above the mandible border in many people). It is vulnerable during the skin incision and superficial dissection of submandibular gland surgery. Injury causes drooping of the corner of the mouth.
Three nerves at risk in submandibular gland excision: (1) Marginal mandibular branch (CN VII) — during skin incision/flap raising; causes angle-of-mouth drooping if damaged. (2) Lingual nerve (CN V3) — during duct dissection (crosses duct twice); causes tongue anaesthesia. (3) Hypoglossal nerve (CN XII) — during deep dissection; causes ipsilateral tongue paralysis.
Incorrect. The marginal mandibular branch of CN VII is the most at-risk nerve during the skin incision (superficial dissection). The lingual and hypoglossal nerves are at risk during deeper dissection around the duct and gland. The skin incision is placed 2–3 cm below the mandible specifically to protect the marginal mandibular branch.
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