Anatomy of salivary glands

Imaging appearances of salivary glands:
In young: homogeneous and hyper/ iso echoic relative to muscle on USG, same as muscle on CT, fatty on MRI
In adults: undergoes progressive fatty infiltration, hence low attenuation on CT and more fatty on MR

USG:
Homogeneously hyperechoic in comparison to adjacent muscles

Parotid gland:
Located in retromandibular fossa, anterior to ear and SCM
Located at mandibular angle wrapping it
Majority is superficial to masseter
Divided into superficial and deep lobes by the facial nerve; Since VII N is not seen on USG, retromandibular vein (lies directly above facial nerve) is used as landmark
Deep lobe lies deep to mandibular angle and very little is seen on USG
Drained by Stenson duct - exits above upper 2nd molar tooth; usually not seen on USG
Facial nerve is located lateral to posterior belly of digastric and retromandibular vein
Lymph nodes may be seen mainly in upper and lower poles

Accessory parotid gland:
Seen in 20%
Drains directly into parotid duct
Lies superficial to masseter, anterior to main parotid gland

Submandibular gland:
Seen in posterior part of submandibular triangle
Triangular in shape
May be connected with parotid or sublingual gland by glandular processes
Facial artery may cross submandibular gland
Facial vein runs along anterosuperior part of submandibular gland
Posteriorly, a branch connecting the retromandibular vein
Medially lingual artery and vein
Wharton duct runs from hilum at the level of mylohyoid muscle, bends around free part of mylohyoid, extends to its orifice at sublingual caruncle along the medial part of the sublingual gland

Sublingual gland:
Lies between muscles of floor of oral cavity, viz., geniohyoid, intrinsic muscles of tongue and hyoglossus and mylohyoid
Lies adjacent to mandible
Oval on cross section and lentiform on long axis
Medially there is Wharton duct

References:
1. Lowe LH et al. Swelling at the Angle of the Mandible: Imaging of the Pediatric Parotid Gland and Periparotid Region. Radiographics. 2001;21:1211-1227
2. BialekEJ etal. US of the Major Salivary Glands: Anatomy and Spatial Relationships, Pathologic Conditions, and Pitfalls. RadioGraphics 2006;26:745-763