Thyroid and Salivary Glands Flashcards
Thyroid Gland:
Location: (2)
- Lies deep to the sternothyroid and sternohyoid muscles
- Located anteriorly in the neck at the level of C5-T1 vertebrae
Thyroid gland
* Anteriorly- (2)
* Posteriorly-
* Posterolateral-
- Anteriorly-
o Loose sheath formed by pretracheal fascia
o Sternohyoid and sternothyroid - Posteriorly- cricoid cartilage and upper 2-3 tracheal rings
- Posterolateral- carotid sheaths and their contents
What is the structure of the thyroid gland? (3)
- Consists primarily of right and left lobes anterolateral to the larynx and trachea
- A thin isthmus unites the lobes over the trachea anterior to 2nd and 3rd tracheal rings
- Surrounds by a thin fibrous capsule which sends septa deeply into the gland
What is the function of the thyroid gland? (2)
- Endocrine gland- ductless gland that secretes directly into the blood
- Secretes
o Thyroid hormone
What is the function of thyroid hormone? (3)
- Acts on whole body except itself, the uterus and spleen
- Controls metabolic rate
o Calcitonin - Controls calcium metabolism
Arterial supply of the thyroid hormone:
* Superior and inferior thyroid arteries lie between the ____ ______ and loose fascial sheath
fibrous capsule
Arterial supply
* Superior thyroid artery from external carotid artery: (2)
o Descends to superior poles of the gland, pierces pretracheal layer
o Supplies anterosuperior aspect
Arterial supply
* Inferior thyroid artery from thyrocervical trunk of subclavian artery: (2)
o Run superomedially posterior to carotid sheaths
o Supplies posteroinferior aspect
What is the Thyroid ima artery? (2)
o In 10% of people
o Small unpaired artery ascending on the anterior surface of trachea to supply the gland
Venous Drainage
* Thyroid venous plexus on the anterior surface is formed by 3 veins:
o Superior thyroid veins
o Middle thyroid veins
o Inferior thyroid veins
What is the superior thyroid vein? (2)
- Accompany the superior thyroid veins
- Drain the superior poles
What are the middle thyroid veins? (2)
- Run parallel to the inferior thyroid arteries
- Drain the middle lobes
What are the inferior thyroid veins? (2)
- Run independently
- Drain the inferior poles
Venous drainage:
* Superior and middle thyroid veins drain into the ____ _____ veins
* Inferior thyroid vein drains into the ________ vein posterior to manubrium
internal jugular
brachiocephalic
Lymphatic Drainage:
How does this take place? (2)
- Lymphatic vessels run in the interlobular connective tissue
- Communicate with a capsular network of lymphatic vessels
Lymphatic Drainage:
* Superiorly:
o Prelaryngeal lymph nodes drain into superior deep cervical lymph nodes
Lymphatic Drainage:
* Inferiorly:
o Pretracheal and paratracheal lymph nodes drain into inferior deep cervical nodes
Lymphatic Drainage:
* Laterally:
o Vessels located along the superior thyroid veins pass directly into the inferior deep cervical lymph nodes
Lymphatic drainage:
* Some vessels drain into brachiocephalic nodes or _______ _____.
thoracic duct
Innervation
* Sympathetic
o Superior middle and inferior cervical ganglia via: (3)
- Cardiac periarterial plexus
- Superior thyroid periarterial plexus
- Inferior thyroid periarterial plexus
Innervation
* Parasympathetic:
o Superior and recurrent laryngeal nerves from vagus nerve
- All fibres are ______
o They constrict blood vessels
vasomotor
What are Recurrent laryngeal nerves? (4)
- Arise from vagus nerve in the inferior part of the neck
- Right recurrent loops inferior to right subclavian a. at T1-T2
- Left recurrent loops inferior to aortic arch at T4-T5
- Both ascend superiorly to the posteromedial aspect of the thyroid gland
Parathyroid glands:
* Location and structure: (2)
o Small flattened, oval glands
o Lie external to the thyroid capsule on the medial half of the posterior surface of each lobe of the thyroid gland within the pretracheal fascia
o Superior parathyroid glands: (3)
- Less variable in position
- 1 cm superior to piercing of inferior thyroid a.
- Level of inferior border of cricoid cartilage
o Inferior parathyroid glands: (2)
- Variable in position
- 1 cm inferior to piercing of inferior thyroid a.
Parathyroid glands:
* Function:
o Secretes Parathormone (PTH)
- Regulates calcium and phosphorus metabolism
- Targets the skeleton, kidneys and intestines
Parathyroid glands:
* Arterial supply:
o Primarily supplied by inferior thyroid a.
o May also be supplied by: (5)
§ Superior thyroid a.
§ Thyroid ima a.
§ Laryngeal a.
§ Tracheal.
§ Oesophageal a.
Parathyroid glands:
* Venous drainage:
o Parathyroid veins
- Drain into thyroid venous plexus
Parathyroid glands:
Lymphatic drainage -
o Run along thyroid vessels deep cervical lymph nodes and paratracheal lymph nodes
Parathyroid glands:
Innervation: (2)
o Vasomotor fibres from thyroid branches of the cervical ganglia
o No secretomotor fibres- the gland is hormonally regulated
What are Salivary Glands?
- Saliva is secreted by the parotid, submandibular and sublingual glands and the mucous glands of the oral cavity
What is the function of saliva? (4)
o Keeps the mucosa moist
o Lubricates food during mastication
o Begins the digestion of starches
o Prevents tooth decay
- Accessory salivary glands are scattered over the….
palate, lips, cheeks and tongue
Submandibular glands:
- Lies along the body of the mandible
What is the submandibular duct? (4)
o 5cm long
o Arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscles
o As it runs anteriorly, the lingual nerve loops underneath
o Opens by 1 or 3 orifices on a small sublingual papilla beside the base of the frenulum of the tongue
Submandibular glands:
* Arterial supply:
o Submental arteries
Submandibular glands:
* Venous drainage:
o Submental veins
Submandibular glands:
* Lymphatic drainage:
o Jugulo-omohyoid lymph nodes of the deep cervical lymph nodes
Submandibular glands:
* Innervation:
What are the Sublingual glands? (4)
- Smallest and most deeply situated and almond-shaped
- Lie in the floor of the mouth between the mandible and the genioglossus
- The glands from each side unite to form a horseshoe-shaped mass around the connective tissue core of the frenulum of the tongue
- Numerous small sublingual ducts open on the floor of the mouth along the sublingual folds
Sublingual glands:
* Arterial supply:
o Sublingual a. (from lingual a.) and submental a. (from facial a.)
Sublingual glands:
* Innervation:
o Accompany submandibular gland innervation
Parotid glands:
* Location:
o Lies in parotid region
o Superior:
o Posterior:
o Medial:
o Anterior:
o Inferior:
o Lies in parotid region
o Superior: zygomatic arch
o Posterior: ear and anterior border of SCM
o Medial: ramus of mandible
o Anterior: medial border of masseter
o Inferior: angle of mandible
- Content of parotid region: (5)
o Parotid gland and duct
o Parotid plexus of facial nerve
o External carotid artery
o Retromandibular vein
o Masseter muscle
Parotid glands:
* Structure: (3)
o Largest of the salivary glands
o Enclosed within a tough fascial capsule
o Has an irregular shape since it is wedged between the ramus of the mandible and the mastoid process
What is the parotid duct? (3)
o Passes horizontally from anterior edge of the gland
o At anterior border of masseter, it turns medially to pierce buccinator
o Enters the oral cavity through a small orifice opposite the 2nd maxillary molar tooth
Parotid glands:
* Blood supply: (2)
o Posterior auricular artery from external carotid
o Superficial temporal artery from external carotid
Parotid glands:
* Venous drainage:
o Retromandibular vein
- Embedded within the parotid gland: (3)
o Parotid plexus of the facial nerve
o Retromandibular vein
o External carotid artery
Parotid glands:
* Innervation:
