Week 5 Salivary glands

Major salivary glands

Parotid, submandibular, and sublingual glands.

Primary function

Saliva secretion for lubrication, aiding in chewing (mastication),

swallowing, and speech

Enzymatic action

Secrete lipase and amylase, which facilitate the digestion of triglycerides and starches.

Immunological role:

Secrete a glycoprotein that forms a complex with immunoglobulin A

(IgA), offering protection against viruses and bacteria

Oral hygiene

Maintain pH balance to protect teeth from cavity-causing bacteria, effectively keeping the mouth clean.

Embryology: salivary glands develop around?

6-8 weeks of gestation via branching morphogenesis of epithelium.

Embryology: parotid gland

First to form but last to be enclosed in connective tissue.

Unique as the only salivary gland with an enclosed lymphatic system containing a high number of lymph nodes within and around it.

Embryology: developmental timeline

Glands are fully developed by 28 weeks.

Acini (secretory cells) begin producing secretory products.

At birth, salivary glands are completely developed and function

Parotid gland: shape and location

Triangular shape with the base situated superiorly and the apex inferiorly.

Found in the retromandibular fossa, positioned anterior to the ear and sternocleidomastoid muscle.

Parotid gland: relational anatomy

Wraps around the mandibular ramus,

Facial nerve divides the gland into superficial and deep lobes.

The facial nerve, external carotid artery, and retromandibular vein pass through the parotid gland.

Typically contains intraparotid lymph nodes

Accessory Parotid Gland

Present in approximately 20% of the population.

Extends across the masseter muscle anterior to the main parotid gland.

Ultrasound Appearance of Parotid Gland

Homogenous with increased echogenicity compared to nearby muscle.

Generally hyperechoic due to the amount of fatty tissue within the gland.

Deep border of the gland can be difficult to visualize clearly.

Common to see “intra-parotid lymph nodes” due to the presence of lymphoid tissue.

Intra-parotid/paraparotid lymph nodes normal appearance

Small size.

Bean-shaped or oval, but intra-parotid lymph nodes often appear round.

Hypoechoic and located within the gland.

Can represent reactive lymph nodes.

Submandibular Gland (SMG): location

Situated in the submandibular triangle of the neck, below the jaw.

Inferior and lateral to the mylohyoid muscle

Submandibular Gland (SMG): lobes

Consists of a superficial and deep lobe separated by the mylohyoid muscle

Submandibular Gland (SMG): excretory duct

Each SMG has its own excretory duct, known as Wharton’s duct or the submandibular duct.

This duct excretes the contents of the gland into the mouth from under the tongue.

Submandibular Gland (SMG): Ultrasound appearance

Homogenous and slightly hyperechoic.

Typically more hypoechoic than the parotid gland due to less adipose tissue.

Wharton’s duct can be seen in approximately 50% of normal patients.

The duct is easily visualized if dilated or if it contains a stone

Sublingual gland: size and location

Smallest of the major salivary glands.

Located on the floor of the mouth mucosa, between the mandible and the genioglossus muscle.

Sublingual gland: capsule

The only one of the three major salivary glands that lacks a fascial capsule.

Sublingual gland: ducts

Unlike the parotid and submandibular glands, the sublingual gland does not have a dominant duct.

Contains approximately 10 small ducts known as the Ducts of Rivinus.

Several smaller ducts often merge to form Bartholin’s duct, which empties into

Wharton’s duct of the submandibular gland.

Sublingual gland: ultrasound appearance

Homogenous, almond-shaped.

Slightly more hyperechoic than surrounding muscles

Why Scan Salivary Glands?

Superficial location makes ultrasound the most appropriate imaging method.

Detects common pathologies:

• Stones

• Tumours

• Abscesses

Low-risk test for monitoring disease progression or tumour growth.

Guidance for Fine Needle Aspiration (FNA).

Detects diffuse conditions like Sjogren’s Syndrome.

Provides imaging information on:

• Salivary parenchyma

• Ductal system

• Mass lesions

• Lymph nodes within the glands

Parotid Gland: Patient Preparation and Equipment

Low shirt for neck access.

Remove jewellery.

Supine position with neck extended (pillow under shoulders).

High-resolution 7-14MHz linear probe.

Lower frequency (5-7MHz) curved probe for deep portions of parotid and SMG.

Adjust probe frequency to assess superficial and deep aspects.

Parotid Gland: Scanning Technique

Patient tilts head back.

Assess entire gland in longitudinal and transverse planes:

• Size (compare right and left).

• Echogenicity.

• Increased vascularity.

• Surrounding lymph node abnormalities.

• Duct dilatation (use color Doppler to differentiate from vessels).

Document in transverse and longitudinal planes with measurements.

Assess right and left neck and lymph nodes.

Measure pathology in longitudinal and transverse planes; assess vascularity.

Parotid gland: most common pathology

Parotid masses account for 80% of salivary gland tumours.

Calculi

Infection

Sjogren’s syndrome

Sialadenitis

Parotid gland: benign masses (80%)

Pleomorphic adenoma (most common).

Warthin's tumor (commonly bilateral).

Cyst.

Parotid gland: malignant masses (20%)

Acinic cell carcinoma.

Carcinoma (ex pleomorphic adenoma).

Mucoepidermoid carcinoma.

Adenoid cystic carcinoma.

Sjogren’s Syndrome

Chronic autoimmune disorder

Sialadenitis

Painful enlargement of the salivary gland (most common in the parotid gland).

Submandibular Gland: Patient preparation and equipment

Low shirt to gain access to neck region

Remove jewellery

Patient laying supine with neck extended/ can place a pillow under shoulders

Use high resolution 7-14MHz linear probe

May need to utilize a lower frequency (5-7Mhz) curved probe to access deep portion of parotid and SMG

Ask patient to tilt head up and to the contralateral side to gain access under the mandible

Submandibular Gland: scanning technique

Ask patient to tilt head back

Assess the entire gland in longitudinal and trans sweeping all the way through for

• Size ( always good to do a dual image with a Rt and Lt comparison)

• Echogenicity

• any increased vascularity

• any abnormality in surrounding lymph nodes

• duct dilatation ( put colour on to make sure not a vessel)

Document in trans and long with measurements

Assess Rt and Lt neck and lymph nodes

Measure any pathology found in long and trans

Assess for vascularity

Submandibular Gland: most common pathology

Infection

Masses ( account for only 10% salivary gland masses)

Submandibular Gland: infection

Adults- bacterial (calculi, retrograde flow of saliva)

Children- viral ( mumps, URTI)

Can result in abscess ( mimic a mass)

Submandibular Gland: masses

Malignant (45%) – adenoid cystic carcinoma

mucoepidermoid carcinoma

Benign (55%) – pleomorphic adenoma

monomorphic adenoma

Sublingual Glands: Patient preparation and equipment

Low shirt to gain access to neck region

Remove jewellery

Patient laying supine with neck extended/ can place a pillow under shoulders

Use high resolution 7-14MHz linear probe

Head tilted as far back as possible to get to access submental region

Sublingual Glands: most common pathology

Ranula

Sublingual Glands: ranula

Cystic enlargement of a portion of the Sublingual Gland

Due to outflow obstruction of one of the SLG ducts

If situated on floor of the mouth can elevate the patient’s tongue

If extending into the neck is described as a “plunging Ranula”