L11: Parotid Bed

Question 1

What week do salivary glands start developing in the embryo?

Answer 1

• Weeks 6-7

Question 2

Explain embryological development of salivary glands. Discuss parotid gland formation.

Answer 2

• Develop during weeks 6-7.
• CT tissue of glands is derived from neural crest cells
• Secretory portions of glands from oral epithelium
• Parotid are first of salivary glands to appear.
• Cord of cells develops from area between maxillary and mandibular prominences (area that is corner of future mouth)
• Cord proceeds towards ear, but maintains connections with angle of mouth
• By week 10, the solid cord develops a lumen and becomes parotid duct
• Terminal ends of cord become secretory portions of gland
• Gland is fully functional by 18th week and starts to secrete saliva

Question 3

Location of parotid gland.

Answer 3

• Located anterior, inferior to the ear, wedged bw ramus and mastoid process in an area known as the parotid bed.

Question 4

Sheath surrounding parotid

Answer 4

• Investing layer of deep cervical fascia on both sides of parotid, known as parotid capsule/sheath.
• Continuous with deep fascia of neck.

Question 5

Course of parotid duct.

Answer 5

• Leaves anterior edge of the gland, courses superficial to masseter muscle and pierces the buccinators muscle to enter into the oral cavity.
• Opens in oral cavity opposite 2nd maxillary molar at parotid papilla

Question 6

What are accessory parotid glands?

Answer 6

• These are parotid gland tissue that are anterior to the actual parotid gland or fused typically with the parotid gland

Question 7

What are structures found within the parotid gland?

Answer 7

• CN VII
• Retromandibular vein (deep to CN VII)
• External carotid artery (deep to vein)

Question 8

Explain course of CN VII.

Answer 8

• CN VII enters the posteriomedial part of the gland and is the most superficial structure in the parotid gland. It forms plexus in gland from which 5 branches are given off to muscles of facial expression. Two branches are given off before entering the gland: posterior auricular branch to occipital belly of occipitofrontalis; motor nerve to posterior belly of digastric.

Question 9

Explain course of retromandibular vein.

Answer 9

• Lies deep to CN VII.
• Formed in parotid gland by junction of superficial temporal and maxillary veins
• In gland, divides into an anterior and posterior part.
• Posterior part joins with posterior auricular vein to form external jugular vein
• Anterior part joins with facial vein to drain into internal jugular vein

Question 10

Explain course of external carotid artery.

Answer 10

• Lies deeper to vein
• Enters gland from its inferior surface
• Terminates in parotid by giving off terminal branches, which are maxillary artery and superficial temporal artery

Question 11

Nerve supply to parotid. Describe course.

Answer 11

• Sympathetic: from superior cervical ganglion, postganglionic fibers enter parotid with external carotid a. Stimulation causes secretion of thick saliva.
• Parasympathetic: branches from CN IX (tympanic nerve and lesser petrosal nerve) bring preganglionic fibers to otic ganglion. Postganglionic fibers from otic ganglion to parotid gland with auriculotemporal nerve (CN V3). Stimulation causes secretion of thin watery saliva.

Question 12

What is mumps?

Answer 12

• Infection of parotid gland. Is acute and communicable viral infection. Can infect other salivary glands. Glands swell causing pain because of sheath of gland.

Question 13

Where do salivary gland tumors occur mostly?

Answer 13

• 80% of salivary gland tumors occur in parotid.

Question 14

Why have a tortuous facial artery?

Answer 14

• Rotation of head.