88. Salivary glands Flashcards
List the four major salivary glands
- Parotid
- Mandibular
- Sublingual
- Zygomatic
The parotid gland is superficial to the …
Vertical ear canal and is triangular shaped
The parotid gland is bordered:
1. Rostrally by…
2. Caudally by…
3. Ventrally by…
4. Superficially by..
- Rostrally by the masseter muscle and the temporomandibular joint
- Caudally by the sternomastoideus and cleidocervicalis muscles
- Ventrally by the mandibular salivary gland
- Superficially by the parotidoauricularis and platysma muscles
The parotid gland is covered by a thin capsule that blends with deeper surrounding structures. Name 7 of these structures.
The intimate association of the parotid capsule and gland with surrounding structures creates a challenging dissection for complete removal of the parotid salivary gland.
- Facial nerve
- Maxillary artery
- Temporal artery
- Internal maxiallary vein
- External acoustic meatus
- Stylomastoid foramen
The stylomastoid foramen transmits the facial nerve, and the stylomastoid artery.
The parotid duct is formed by two or three converging ductules on the ventrorostral border of the gland.
1. Where does it travel?
2. Where does is open?
It travels over the lateral aspect and ventral third of the masseter muscle and opens into the oral cavity through a small papilla at the level of the upper fourth premolar.
Where is an accessory parotid gland found?
Accessory parotid gland in the form of glandular lobules
Dorsal to the parotid duct.
Where does the accessory parotid gland tissue empty into ?
Directly into the main parotid duct through several small communications.
What is the arterial supply to the parotid gland?
Parotid artery a branch of the external carotid artery.
Several other small branches from surrounding arteries also contribute to its perfusion.
Describe the location to identify the parotid artery
ID: the medial aspect of the parotid gland in the region *ventral *to the external ear canal
Name the venous return from the parotid gland
Superficial temporal and great auricular veins
The majority of the lymphatic flow from the parotid gland is directed toward which two lymph nodes.
- Parotid lymph node
- Medial retropharyngeal lymph node
Describe the location of the zygomatic gland
In reference to the globe and zygomatic arch
Located in the periorbital area just **ventral and rostrolateral **to the globe and medial to the zygomatic arch
How many major and minor ducts come from the zygomatic gland into the oral cavity?
One major
Four minor
Where does the zygomatic gland major duct open into the oral cavity?
Caudolateral aspect of the last upper molar
Typically the zygomatic papilla is approximately 1 cm caudal to the parotid salivary papilla.
True or false?
True
What artery supplies the zygomatic gland?
A branch of the infraorbital artery
Name the vein draining the zygomatic salivary gland
Deep facial vein
Name lymph node that zygomatic gland drain
Medial retropharyngeal lymph node
Mandibular and sublingual salivary gland are seperated by the sublingual muscle. True or false?
False
Intimately associated and thus considered anatomically as a pair.
These two glands share a common capsule and can initially look like a single gland
The mandibular salivary gland can be palpated.
True or false?
True
Large, palpable gland located caudomedial to the angle of the mandible
Describe the location of the mandibular salivary gland
In relation to veins, lymph nodes and anatomic land marks
It lies on the medial aspect of the **linguofacial and maxillary vein junction. The mandibular lymph nodes lie on its ventral surface and the medial retropharyngeal lymph node** and** larynx** on its **medial **surface.
Its cranial border abuts the primary portion of the sublingual salivary gland.
Where does the mandibular salivary duct exit on the gland?
On the glands medial surface.
Describe the course of the mandibular salivary duct
Continues rostrally, medial to the sublingual salivary gland and horizontal ramus of the mandible. Under the oral mucosa, it travels between the styloglossus and mylohyoideus muscles until it exits into the oral cavity
oral cavity: sublingual caruncle lateral to the lingual frenulum
Where does the mandibular salivary gland enter into the oral cavity?
Sublingual caruncle lateral to the lingual frenulum
Name the major blood supply to the mandibular salivary gland
Glandular branch of the facial artery
Other small arteries and veins may be present
Name the venous drainage from the mandibular salivary gland
Branch of the lingual vein
Other small arteries and veins may be present
Name the lymph nodes the mandibular salivary gland drains to
Retropharyngeal lymph nodes
The sublingual salivary gland is composed of monostomatic and polystomatic portions.
True or false?
Monostomatic glands deliver saliva to a distant site through a singular duct, whereas polystomatic glands produce saliva locally through multiple openings adjacent to the saliva-producing glands
True
Which portion of the sublingual salivary gland is found in the capsule shared by the mandibular salivary gland?
Largest and most caudal component of the monostomatic portion
It has a large portion that abuts the mandibular salivary gland and tapers to a triangular shape rostrally
Describe the sublingual salivary gland location external to the capsule
The gland continues rostrally in close association with the mandibular duct but is packaged in loose clusters of glandular tissue deep to the digastricus and mylohyoideus muscles
Sublingual salivary tissue caudal to the lingual nerve empties into the ……..duct and is considered a ……….stomatic salivary gland.
Sublingual salivary tissue caudal to the lingual nerve empties into the sublingual duct and is considered a monostomatic salivary gland.
Sublingual salivary gland: The polystomatic salivary tissue consists of small clusters of glandular tissue rostral to the lingual nerve that typically empty directly into the oral cavity.
True or false?
True
The major sublingual salivary duct courses where?
Alongside the mandibular duct
The major sublingual salivary duct usually exits where?
At the sublingual caruncle just caudal to the mandibular duct.
The monostomatic portion of the sublingual salivary gland receive blood supply from where?
The glandular branch of the facial artery
The polystomatic portion of the sublingual salivary gland receive blood supply from where?
The sublingual branch of the lingual artery
Name sublingual salivary gland venous drainage
Satellite veins
Lymphatics from the sublingual salivary gland drain to the?
Medial retropharyngeal lymph nodes
What are minor salivary glands?
Small collections of salivary tissue surrounding the oral cavity that drain their secretions directly into the oral cavity to keep it moist
Name SIX minor salivary glands
- Buccal
- Labial
- Lingual
- Tonsillar
- Palatine
- Molar
Salivary gland disease is rarely reported with the minor salivary glands.
Open-mouth view in an anaesthetised cat. What is circled?
The membranous molar pad (circled) containing the molar gland, lingual to the molar tooth
Name functions of saliva
(six)
- Lubricate ingesta - facilitate packaging of a food bolus for its passage down the oesophagus
- Thermoregulation (evaporative cooling)
- Oral cavity cleansing
- Buffering of weak acids
- Reduction of oral bacterial growth
- Protection of surface epithelium in the oral cavity
Salivary α-amylase in dogs and cats plays a significant role in carbohydrate digestion.
True or false?
False.
Unlike in other species, salivary α-amylase in dogs and cats does not play a significant role in carbohydrate digestion.
Describe the pathway of saliva from the acinus to the major excretory ducts
Saliva travels from the acinus to the** intercalated ducts**, then to the intralobular ducts, interlobular ducts, lobular ducts, and finally the major excretory ducts
The acinus, or the terminal salivary gland unit, produces saliva that travels into the intercalated ducts. These ducts coalesce to form the intralobular ducts, which flow into interlobular ducts, lobular ducts, lobar ducts, and finally the major excretory ducts.
What are the two types of cells found in most salivary glands?
Histologically, most salivary glands consist of a combination of serous and mucus-producing cell
Define acinus in the context of salivary glands
The acinus is the terminal salivary gland unit that produces saliva
Parotid? Mandibular? Sublingual? Zygomatic?
Which glands produce more serous secretions?
Parotid and Mandibular
Evaluation of the location and viscosity of the aspirated fluid may therefore provide clues in identifying the offending gland.
Whats the diagnosis?
Sialocele
* small-moderate numbers of nondegenerate nucleated cells
* diffuse/irregular clumps of homogenous pink/violet staining mucin
* macrophages may contain abundant, foamy cytoplasm
* mucin-specific stain: periodic acid–Schiff
Where is sialocele? What is the choice of treament?
Exophthalmos, protrusion of the third eyelid, painless orbital swelling
Zygomatic.
* Sialadenectomy.
* Use of a sclerosing agent has also been proposed.
Where is sialocele? What is the choice of treament?
Swelling caudal dorsal or lateral pharynx, just rostral to the level of the epiglottis. Labored breathing or stridor
**Pharyngeal. **
* Acute obstruction - immediate drainage (via incision) or temporary tracheostomy.
* After stabilisation redundant tissue resected and sialocele marsupialized. The origin of the sialocele (sublingual and mandibular salivary gland and duct complex), should also be removed.
Name the sialocele
Sublingual: AKA ranula
Name the sialocele
Swelling in the intermandibular or cranioventral cervical region
Cervical
Describe the ventral approach for sublingual and mandibular sialadenectomy
- Incision: starting 4 to 5 cm caudal to the mandibular ramus on the affected side and extending rostrally toward the mandibular symphysis
- Platysma muscle incised: allows ID of the external jugular bifurcation; the mandibular gland sits at or just cranial to this bifurcation
- Tissues are bluntly dissected to expose the capsule covering the mandibular and sublingual salivary glands
- Glands must be differentiated from mandibular lymph nodes (which are more rostral and ventral at this location)
- Capsule is incised and bluntly dissected off the glandular tissue to allow ligation of vessels on the medial side of the gland
- Gland complex is retracted caudally - blunt dissection of the sublingual gland under (dorsal to) the digastricus muscle
- Place hemostat from rostral to caudal under the digastricus muscle, the ducts are clamped just rostral to the large glandular complex - mandibular and main sublingual gland are excised
- The remaining ducts and sublingual glands are pulled under the digastricus muscle
- Blunt and sharp dissection are continued rostrally to the level of the lingual nerve; the mylohyoideus muscle is incised for best exposure of the rostral glandular tissue and lingual nerve
- Glandular tissue removed up to the lingual nerve - exect if ranular present
- The mylohyoideus, platysma muscle, and subcutaneous tissues are reapposed with an absorbable monofilament suture
If bilateral gland removal is to be performed, a midline incision can be made.
Describe the lateral approach for sublingual and mandibular sialadenectomy
- Lateral recumbency with the affected side upwards and the neck extended
- Jugular bifurcation is identified, and a horizontally oriented incision is made over the expected location of the mandibular salivary gland, between the linguofacial and maxillary veins
- Overlying subcutaneous tissues are removed with blunt and sharp dissection to expose the capsule of the sialocele (or mandibular gland) - capsule is perforated, and the contents are removed with suction
- Next the mandibular and largest sublingual glands are identified and dissected free from surrounding tissues
- Ligation of the blood supply (entering the rostromedial surfaces of the glands) may be necessary during dissection
- Blunt dissection continues rostrally along, and parallel with, the ducts, exposing more clusters of sublingual salivary tissue
- A hemostat is placed distally across the ducts, and traction is applied to the gland-duct complex
- Blunt dissection of fascia proceeds between the duct-gland complex and surrounding muscles (digastricus caudomedially and masseter muscle rostrolaterally); the** lingual branch **of the trigeminal nerve may need to be dissected free of the duct at this time
- Hemostat can be replaced more distally as more duct and glandular tissue are exposed
- Ducts can either be ligated distally and transected just proximal to the ligature, or they can be separated from oral cavity tissue with slow, steady traction
- Alternatively, the duct salivary gland can be transected proximal to the hemostat, and a Carmalt hemostatic forceps passed medial to the rostral digastricus muscle from a caudoventral to rostrodorsal direction
- Transected ends of the remaining salivary ducts are grasped with the tips of the forceps and pulled medial to the rostral digastricus muscle to allow further dissection of the duct
Describe a Zygomatic sialadenectomy
- Incision is made horizontally through the skin and subcutaneous tissue over the dorsal aspect of the arch
- Aponeurosis of the masseter muscle is reflected off of the ventral aspect of the zygomatic arch, and the orbital fascia is reflected dorsally
- Portion of the rostrolateral zygomatic arch is removed, as necessary, with a bone saw or rongeurs to gain access to the region of the zygomatic gland
- Orbital fat is dissected and retracted to gain access to glandular tissue
- Gland resides medial to the zygomatic arch and adjacent to the globe on the rostroventrolateral aspect
- Gland is gently retracted and dissected free from surrounding tissue
- A branch of the infraorbital (malar) artery supplying the salivary gland is accessed for ligation by dorsal retraction of the gland
- During closure, orbital fascia is reapposed to the aponeurosis of the masseter muscle, and subcutis and skin are closed routinely
Careful dissection is required due to sensitive structures in that area and anatomic changes caused by the presence of the sialocele.
Describe a Parotid sialadenectomy
- Patient in lateral recumbency. The skin is incised over the vertical ear canal, starting at a point below the external acoustic meatus and extending ventrally to the level of the caudal angle of the mandible
- Platysma and parotidoauricularis muscles are incised to gain exposure to the glandular tissue
- Ligation and division of the caudal auricular vein
- Parotid gland is bluntly dissected from its attachments, beginning at its dorsocaudal border - continued rostrally, separating the gland from the ear canal and other surrounding tissues
- Dissection should proceed cautiously near the horizontal canal in an attempt to spare the facial nerve
- Several small vessels that require cauterization or ligation will be encountered during the dissection of the medial side of the gland
- The gland is dissected out to the level of the duct, which is freed from surrounding tissues, ligated, and divided
- If clinical presentation included lateral cheek swelling, the accessory parotid gland just dorsal to the parotid duct should also be dissected free and removed
Complete removal of the parotid salivary gland is difficult - dissection extends to the region of the horizontal ear canal, facial nerve paresis or paralysis is a common complication.
