Anterior Triangle - Muscles and Endocrine Glands Flashcards
What are the borders of the anterior triangle?
Inferior border of mandible
Anterior border of SCM
Midline of neck
What can be found on the roof of the anterior triangle?
Deep investing fascia around muscles
What can be found on the floor of the anterior triangle?
Pretracheal fascia and carotid sheath (postolaterally)
What are the sub-triangles of the anterior triangle?
Submandibular
Submental
Carotid
Muscular (omotracheal)
What can be found in the submandibular (digastric) triangle?
Submandibular gland
Lymph nodes
Parts of CN XII
Mylohyoid nerve
Parts of the facial artery and vein
What can be found in the submental triangle?
Submental lymph nodes
Some small veins which unite to form the anterior jugular vein
What can be found in the carotid triangle?
Thyroid gland
Larynx
Pharynx
Carotid sheath and its contents
Branches of the cervical plexus
Superior root of the ansa cervicalis
Parts of CN XI and XII
Deep cervical lymph nodes
What can be found in the muscular (omotracheal) triangle?
Sternohyoid
Sternothyroid
Thyroid gland
Parathyroid gland
What are the suprahyoid muscles and where do they connect?
Connect to skull or mandible
Mylohyoid
Digastric
Stylohyoid
Geniohyoid
What are the infrahyoid muscles and where do they connect?
Connect to inferior structures - sternum, scapula, thyroid cartilage
Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid
What is the exception to infrahyoid muscle attachment?
The sternothyroid doesn’t attach to the hyoid but the sternum inferiorly and the thyroid cartilage superiorly
What is the general function of suprahyoid muscles?
Elevate the hyoid (swallowing) and larynx (tone production) and constitute substance of floor of mouth
Where does the mylohoid originate and insert?
Originates at mylohyoid line on mandible
Inserts into body of hyoid and fibres of opposite mylohyoid
What is the action of the mylohyoid?
Elevates the hyoid and the floor of the mouth
Reinforces the floor of the oral cavity
Where does the digastric originate and insert?
Anterior belly originates at digastric fossa on lower medial aspect of mandible
Posterior belly originates at mastoid notch on medial side of mastoid process
Both insert at attachment of their intermediate tendon at hyoid by a fascial sling
What is the action of the digastric?
Anterior belly raises hyoid and opens mouth by lowering mandible
Posterior belly elevated and retracts the hyoid bone
What innervates the mylohyoid?
CN V3 - inferior alveolar branch known as nerve to mylohyoid
What innervates the digastric?
Anterior belly - nerve to mylohyoid
Posterior belly - digastric branch of CN VII
Where does the stylohyoid originate and insert?
Originates at the styloid process
Inserts into body of hyoid laterally
What is the action of the stylohyoid?
Pulls hyoid bone upwards (posterosuperior direction)
What innervates the stylohyoid?
CN VII
Where does the geniohyoid originate and insert?
Originates from the mandible - mental spine
Inserts at the body of hyoid - superior to mylohyoid
What is the action of the geniohyoid?
If fixed mandible - elevates and pulls hyoid forwards
If fixed hyoid - pulls mandible down and inwards
What is the innervation for the geniohyoid?
Anterior ramus of C1 - travels with CN XII
What is the general function of infrahyoid muscles?
Depress or fix hyoid bone and provide attachment for suprahyoid muscles
Where does the sternohyoid originate and insert?
Originates at posterior surface of sternoclavicular joint and manubrium
Inserts into body of hyoid medially
What is the action of the sternohyoid?
Depresses hyoid after elevation during swallowing
Where does the omohyoid originate and insert?
Superior belly originates at its intermediate tendon and inserts into body of hyoid laterally
Inferior belly originates at superior border of scapula and inserts/ends at its intermediate tendon
What is the function of the omohyoid?
Depresses and fixes the hyoid
Where does the thyrohyoid originate and insert?
Originates at the oblique line on thyroid cartilage
Inserts into the greater horn and adjacent body of the hyoid
What is the function of the thyrohyoid?
Depresses the hyoid
Can raise the larynx when hyoid is fixed
Where does the sternothyroid originate and insert?
Originates at posterior surface of the manubrium
Inserts into the oblique line on thyroid cartilage
What is the action of the sternothyroid?
Draws the larynx downward
What innervates the sternohyoid, omohyoid and sternothyroid?
The anterior rami of C1 to C3 - through the ansa cervicalis
What innervates the thyrohyoid?
Anterior rami of C1 - fibres run with CN XII
Describe the location and appearance of the thyroid gland
Found in visceral compartment of neck
Composed of 2 lateral lobes (L and R)
Extends from thyroid cartilage to 5th tracheal ring
Midline isthmus at 3rd tracheal ring
Midline pyramidal lobe variably present
What is the arterial supply for the thyroid gland?
Superior thyroid artery - 1st branch of external carotid
Inferior thyroid artery - branch of thyrocervical trunk from subclavian
10% have an additional artery
Describe the venous drainage of the thyroid venous plexus
Superior thyroid vein - into IJV
Middle thyroid vein - into IJV
Inferior thyroid vein - into brachiocephalic
Describe the location and appearance of the parathyroid glands
Two pairs (superior and inferior) of small glands usually on posterior surface of thyroid
Exact position can vary extensively and aberrant parathyroid tissue can be present
Describe the arterial supply and venous drainage of the parathyroid glands
Inferior thyroid arteries (branch of thyrocervical trunk)
Venous drainage same as thyroid
What innervates the thyroid and parathyroid glands?
Thyroid branches from the cervical (sympathetic) ganglia
Vasomotor fibres - constrict blood vessels; endocrine secretion regulated hormonal by pituitary
What are implications of the thyroid and parathyroid glands for neck surgery?
Anatomical relationship to recurrent laryngeal nerves from CN X
Potential damage to right recurrent laryngeal nerve
Symptoms of injury include hoarseness or aphonia (loss of voice)
What is a cricothyrotomy?
(Coniotomy)
Emergency procedure, large bore needle passed through cricothyroid ligament
May be replaced by a small tracheostomy tube
What is a tracheostomy?
Surgical airway, involves retraction of infrahyoid muscles and incision of isthmus to insert tube between 1-2nd or 2-4th tracheal rings
What are the anatomical considerations of airway procedures?
Awareness of vasculature of neck
Age-related variation - presence of thymus in children or risk to oesophageal damage due to softness of trachea in children
