anatomy of the front of the neck Flashcards
Describe the borders of the anterior triangle of the neck
situated at front of neck
superiorly - inferior border of mandible
laterally - medial border of sternocleidomastoid muscle
medially - imaginary saigittal line down midline of body
name the suprahyoid muscles
- digastric muscle
- mylohyoid muscle
- stylohyoid muscle
- geniohyoid muscle
Describe the digastric muscle
two muscular tendons connected by a tendon
anterior belly arises from gastric fossa of the mandible - gives rise to central tendon
posterior belly arises from the mastoid process of the temporal bone
two bellies connected by intermediate tendon attached to the hyoid bone via a fibrous sling
describe the mylohyoid muscle
triangular shaped muscle forming the floor of the oral cavity, supporting the floor of the mouth
originates from the mylohyoid line of the mandible and attaches to the hyoid bone (posterior fibers)
Describe the sternocleidomastoid muscle
attaches to:
- sternum
- clavicle
- mastoid process
innervated by CNXI
tendinous head attaches to sternum
fleshy head attaches to clavicle
Describe the platysma muscle
superficial muscle that overlaps the sternocleidomastoid
broad sheet arising from fascia covering upper pectoralis major and deltoid
fibers cross clavicle obliquely upward and medially along side of neck
Describe the thryoid cartilage
- laryngeal notch
- composed of two sheets (laminae) that join anteriorly (laryngeal prominence)
- posterior border projects superiorly and inferiorly to form the superior and inferior horns
- superior horns articulate with hyoid bone
- inferior horns in contact with cricoid cartilage
What is the cricoid cartilage?
- complete ring of hyaline cartilage
- completely encircles the airway, marking the inferior border of the larynx at C6 level
What is the cricothyroid ligament?
connective tissue that connects front parts of the contiguous margins of the cricoid and thyroid cartilages
What is a cricothyrotomy?
incision made through the skin and cricoid membrane to establish a patent airway
- site where emergency airway can be placed
What are the strap muscles?
also called infrahyoid muscles
cover the lobes of the thyroid gland and must be retracted for surgery
located inferiorly to the hyoid bone in the neck
What are the groups of strap muscles
- superficial plane
> omohyoid
> sternohyoid - deep plane
> sternothyroid
> thyrohyoid
What is the arterial and venous supply of the infrahyoid muscles?
superior and inferior thyroid arteries
venous supply by corresponding veins
Describe the sternohyoid muscle
originates from the sternum and sternoclavicular joint
ascends to insert onto the hyoid bone
Describe the omohyoid muscle
- two muscle bellies connected by a muscular tendon
inferior belly arises from scapula runs superomedially underneath the sternocleidomastoid muscle
attached to the superior belly by an intermediate tendon, which is anchored to the clavicle by the deep cervical fascia
from here the superior belly ascends to attach to hyoid bone
describe the thyrohyoid muscle
short band of muscle, thought to be continuation of the sternothyroid muscle
arises from the thyroid cartilage of the larynx and ascends to attach to the hyoid bone
Describe the location of the thyroid gland
- anterior neck
- spans C5-T1
- lies behind sternohyoid and sternothyroid muscles wrapping around the cricoid cartilage and superior tracheal rings
- inferior to the thyroid cartilage
- in visceral compartment of neck
Describe the thyroid gland
- endocrine gland
- two lobes divided by isthmus
Describe the visceral compartment of the neck
contains:
- thyroid
- trachea
- oesophagus
- pharynx
compartment bound by pretracheal fascia - also secures thryroid gland to trachea and larynx
Why does a goitre move on swallowing?
the fascia attaches the gland and thereby the growth to the larynx, which moves
(if a lump on the neck moves on swallowing it is likely to be localised to the thyroid gland)
Why is the thyroid highly vascularised?
gland secretes hormones directly into the blood
Which two main arteries supply the thyroid gland?
superior and inferior thyroid arteries
paired arteries arising on both the left and right sides
Describe the superior thyroid artery
first branch of the external carotid artery
- then descends towards the thyroid gland
- generally supplies the superior and anterior portions of the gland
Describe the inferior thyroid artery
arises from thyrocervical trunk (branch of the subclavian)
travels superomedially to reach the inferior pole of the thyroid
tends to supply the postero-inferior aspect
What additional artery can be found in a small proportion of the population?
thyroid ima artery
originates from the brachiocephalic trunk of aortic arch, supplying the anterior surface and isthmus
Describe the venoud drainage of the thyroid
superior, middle and inferior thyroid veins form a venous plexus
superior and middle drain into internal jugular
inferior drains into brachiocephalic
Describe the innervation of the thyroid gland
branches derived from the sympathetic trunk
- do not control endocrine secretion, which is highly regulated by the pituitary gland
What is the submental triangle?
found in the neck, situated under the chin
contains submental lymph nodes
bounded:
- inferiorly: hyoid bone
- medially: imaginary sagittal midline of the neck
- laterally: anterior belly of the digastric
base formed by mylohyoid muscle (runs from mandible to the hyoid bone)
What is the submandibular triangle?
located underneath the body of the mandible
contains the submandibular gland and lymph nodes
facial vein and artery also pass through here
boundaries:
- superiorly: body of mandible
- anteriorly: anterior belly of digastric muscle
- posteriorly: posterior belly of digastric muscle
