Posterior & Anterior Triangles of the Neck, Thyroid & Parathyroid* Flashcards
Identify the boundaries of the anterior triangle.
- Inferior border of mandible (SUP)
- Anterior border of sternocleidomastoid (SCM) (LAT)
- Midline of neck (MED)
What are the roof, and floor of the anterior triangle covered by ?
- Deep investing fascia around muscles (covers ROOF)
* Petracheal fascia and carotid sheath (latter posterolaterally) (cover FLOOR)
What is fascia ?
Thin sheath of CT enclosing muscle or other organs
What are the fascial layers of neck ?
- Investing fascia (around circumference of neck, composed of deep cervical fascia)
- Neurovascular column, composed of carotid sheath (contains vagus, common carotid, internal jugular)
- Visceral column, made of pre-tracheal fascia (larynx, pharynx, oesophagus, trachea)
- Pre-vertebral column (spine, muscles of back)
What are the fascial layers of neck ? State what each one contains.
- Investing fascia (around circumference of neck, composed of deep cervical fascia)
- Neurovascular column, composed of carotid sheath (contains vagus, common carotid, internal jugular)
- Visceral column, made of pre-tracheal fascia (larynx, pharynx, oesophagus, trachea)
- Neuromusculoskeletal column, made of pre-vertebral fascia (spine, muscles of back)
Identify the main subdivisions of the anterior triangle.
- Submandibulardivision
- Submental
- Carotid
- Muscular
Identify the main contents of the submandibular (digastric) subdivision of the anterior triangle.
Contains
- Submandibular gland
- Lymph nodes
- (parts of) CN XII
- Mylohyoid nerve
- Parts of facial artery and vein
Identify the main contents of the submental triangle subdivision of the anterior triangle.
Contains
- Submental lymph nodes
- Some small veins
Identify the main contents of the carotid triangle subdivision of the anterior triangle.
Contains
• Thyroid gland • Larynx • Pharynx • Carotid sheath (and its contents) • Branches of cervical plexus • Superior root of ansa cervicalis • Deep cervical lymph nodes • (Parts of) CNXI and XII
Identify the main contents of the muscular (omotracheal) triangle subdivision of the anterior triangle.
Contains • Sternohyoid muscles • Sternothyroid muscles • Thyroidgland • Parathyroid glands
Where are the suprahyoid muscles located ? Where do they connect ?
SUPRAHYOID MUSCLES
• Above hyoid
• Connect to skull or
mandible
Where are the infrahyoid muscles located ? Where do they connect ?
INFRAHYOID MUSCLES
• Below hyoid
• Connect to inferior structures (sternum, scapula, thyroid cartilage)
Identify the main suprahyoid muscles.
Mylohyoid
Digastric
Stylohyoid
Geniohyoid
Identify the main infrahyoid muscles.
Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid
What do suprahyoid muscles do ?
Raise the hyoid bone as required during swallowing
MYLOHYOID MUSCLE
- Origin
- Insertion
- Actions
MYLOHYOID MUSCLE
- Origin: mylohyoid line on mandible
- Insertion: body of hyoid and fibers of opposite mylohyoid
- Actions: elevates hyoid and floor of the mouth + supports floor of mouth + reinforces floor of oral cavity
DIGASTRIC MUSCLE
- Origin
- Insertions
- Actions
DIGASTRIC MUSCLE
1) Anterior Belly
- Origin: digastric fossa on lower medial aspect of mandible
- Insertions: at attachment of their intermediate tendon at hyoid
- Actions: raises hyoid and opens mouth by lowering mandible
2) Posterior Belly
- Origin: mastoid notch on medial side of mastoid process
- Insertion: at attachment of their intermediate tendon at hyoid
- Actions: elevates and retracts hyoid bone
STYLOHYOID
- Origin
- Insertion
- Actions
STYLOHYOID
- Origin: styloid process
- Insertion: body of hyoid (laterally)
- Actions: pulls hyoid bone upwards (posterosuperior direction)
GLENOHYOID
- Origin
- Insertion
- Actions
GLENOHYOID
-Origin: mental spine of mandible
-Insertion: body of hyoid
-Actions:
Fixed mandible- elevates and pulls hyoid forward
Fixed hyoid- pulls mandible downwards and inward
Describe innervation of suprahyoid muscles.
- Mylohyoid is innervated by CN V3 inferior alveolar branch (known as nerve to mylohyoid)
- Digastric muscle is innervated by:
- Anterior belly – nerve to mylohyoid (CN V3,)
- Posterior belly – Digastric branch of CN VII
- Sytlohyoid is innervated by CN VII
- Glenohyoid is innervated by anterior ramus of C1 (travels with CNXII)
What do infrahyoid muscles do ?
Depress hyoid after elevation during swallowing
What is another name for infrahyoid muscle ?
Strap muscle
STERNOHYOID
- Origin
- Insertion
- Actions
STERNOHYOID
- Origin: posterior surface of sternoclavicular joint and manubrium
- Insertion: body of hyoid medially
- Actions: depresses hyoid after elevation during swallowing
OMOHYOID
- Origin
- Insertion
- Actions
OMOHYOID
1) Superior belly
- Origin: intermediate tendon
- Insertion: body of hyoid laterally
2) Inferior belly
- Origin: superior border of scapula
- Insertion: Its intermediate tendon in posterior triangle (tendon attaches to clavicle using fascial sling)
-Actions: depress and fix the hyoid
THYROHYOID
- Origin
- Insertion
- Actions
THYROHYOID
- Origin: oblique line on thyroid cartilage
- Insertion: greater horn and adjacent body of hyoid
- Actions: depress hyoid + can raise larynx when hyoid is fixed
STERNOTHYROID
- Origin
- Insertion
- Actions
STERNOTHYROID
- Origin: posterior surface of manubrium
- Insertion: oblique lines on thyroid cartilage
- Actions: draws larynx downwards
Describe innervation of infrahyoid muscles.
Anterior rami of C1 to C3
• Sternohyoid
• Omohyoid
• Sternothyroid
THYROHYOID
-Innervated by anterior rami of C1 (whose fibers run with CNXII)
Which compartment of the neck is the thyroid gland present in ?
Within visceral compartment of the neck
Identify the main structural features of the thyroid gland.
- Composed of 2 lateral lobes (right and left) (extends from thyroid cartilage to 5th tracheal ring)
- Midline isthmus (level of 3rd tracheal ring)
- Midline pyramidal lobe (variably present, remnant of thyroglossal duct)
Describe arterial supply of the thyroid gland.
• Superior thyroid artery (1st
branch of external CA)
• Inferior thyroid artery (branch of thyrocervical trunk from subclavian)
Describe venous drainage of the thyroid gland.
Thyroid venous plexus:
• Superior thyroid vein (into IJV)
• Middle thyroid vein (into IJV)
• Inferior thyroid vein (into brachiocephalic)
Describe anatomical position of parathyroid glands.
Two pairs (superior and inferior) of small glands usually on posterior surface of thyroid, but exact position varies
Describe arterial supply, and veinous drainage of parathyroid glands.
Arterial supply:
-Inferior thyroid arteries (branch of thyrocervical trunk from subclavian)
Veinous drainage: Thyroid venous plexus
• Superior thyroid vein (into IJV)
• Middle thyroid vein (into IJV)
• Inferior thyroid vein (into brachiocephalic)
Describe innervation of thyroid and parathyroid.
Both thyroid and parathyroid glands are innervated by thyroid branches from the cervical (sympathetic) ganglia
Why is it important to consider the recurrent laryngeal nerve’s relationship to the thyroid and parathyroid glands?
Recurrent laryngeal nerve is around area of thyroid gland. Hence, concern during neck (e.g. when doing surgery on thyroid gland) surgery – symptoms of injury include hoarseness or aphonia
Identify the main boundaries of the posterior triangle.
- Posterior border of SCM (anterior)
- Anterior border of trapezius (posterior)
- Middle 3rd of clavicle (inferior)
- Occipital bone (apex)
What are the roof, and floor of the posterior triangle covered by ?
Deep investing fascia around muscles (SCM and trapezius) (covers ROOF)
-(muscular) prevertebral fascia surrounding splenius capitus, levator scapulae, and P, M, A scalenes (covers FLOOR)
SCM
- Origin
- Insertion
- Actions
SCM
1) Sternal head
- Origin: manubrium of sternum
- Insertion: inserts lateral half of the superior nuchal line
2) Clavicular head
- Origin: medial 3rd of clavicle
- Insertion: lateral surface of mastoid process
-Actions: Draws the head forward (both SCMs), or tilts head toward ipsilateral shoulder while turning faces contralaterally (one SCM)
What is the innervation of the SCM ?
Spinal Accessory Nerve (CNXI)
TRAPEZIUS
- Origin
- Insertion
- Actions
TRAPEZIUS -Origin: • superior nuchal line • external occipital protuberance • Ligamentum nuchae • Spinous processes (C7-T12)
-Insertion:
• Lateral 3rd of clavicle
• Acromion
• Spine of scapula
-Actions • Assists rotating scapula during abduction of humerus • Upper fibres elevate scapula • Middle fibres adduct scapula • Lower fibres depress scapula
What is the innervation of the Trapezius ?
Spinal accessory nerve (CN XI)
LEVATOR SCAPULAE
- Origin
- Insertion
- Actions
LEVATOR SCAPULAE
- Origin: C1-C4 (transverse processes)
- Insertion: scapula (upper medial border)
- Actions: Elevates scapula
What is the innervation of Levator Scapulae ?
C3, C4, Dorsal scapular nerve (C4, C5)
ANTERIOR SCALENE
- Origin
- Insertion
- Actions
ANTERIOR SCALENE
- Origin: C3-C6 (anterior tubercle of transverse processes)
- Insertion: upper surface of rib 1 and scalene tubercle
- Actions: Elevates 1st rib
MIDDLE SCALENE
- Origin
- Insertion
- Actions
MIDDLE SCALENE
- Origin: C4-C7 (transverse processes)
- Insertion: upper surface of rib 1, posterior to groove for SCA
- Actions: Elevates 1st rib
What is the innervation of the anterior scalene ? middle scalene ?
ANTERIOR SCALENE
• Anterior rami of C4-C7
• C3
MIDDLE SCALENE
• Anterior rami of C4-C7
What are the main components of the cervical plexus ?
Anterior rami of C1, C2-C4
Identify the muscular branches of the cervical plexus, including the spinal nerves that contribute to each.
Muscular branches
• Phrenic nerve (C3, C4, C5)
• Ansa cervicalis (C1, C2, C3) branches to prevertebral and vertebral muscles
Identify the cutaneous branches of the cervical plexus, including the spinal nerves that contribute to each.
Cutaneous branches
• Lesser occipital branches (C2)
• Great auricular and transverse cervical nerves (C2, C3)
• Supraclavicular nerves (C3, C4)
What is the main function of the ansa cervicalis ?
Superior and inferior roots innervate infrahyoid muscles
Identify contents of the posterior triangle.
- Inferior belly of omohyoid muscle
- CNXI
- Branches of cervical plexus
- Distal part of Sc artery
- Sc vein
- Trunks of brachial plexus
Describe superficial venous drainage of the neck.
- External jugular vein drains into the subclavian vein
* Anterior jugular vein drains into the external jugular vein
