Neck Triangles (A13) Flashcards
All neck triangles are on both sides therefore there are two of each, which is the exception
sub mental
division of neck triangles
- posterior
- anterior
4 types anterior neck triangles
- submandibular
- submental
- muscular
- carotid
posterior neck triangle: 1-borders 2-apex 3-roof 4-floor 5-contents
1-posterior border of SCM , middle third of clavicle, anterior border of trapezius
2-point between anterior border of trapezius and posterior border of SCM SUPERIORLY at the base of the skull on superior nuchal line
3-investing layer of deep fascia
4-deep cervical fascia covering muscles (prevertebral fascia)
5-(spinal) accessory nerve (CNXI)
origin of spinal accessory nerves (CNXI)
-mostly arise from spinal cord rather than the base of the brain
borders of posterior neck triangle
posterior border of SCM , middle third of clavicle, anterior border of trapezius
apex of posterior neck triangle
point between anterior border of trapezius and posterior border of SCM SUPERIORLY at the base of the skull
roof of posterior neck triangle
investing layer of deep fascia
floor of posterior neck triangle
deep cervical fascia covering muscles (prevertebral fascia)
contents of posterior neck triangle
(spinal) accessory nerve (CNXI)
route of (spinal) accessory nerves from spinal cord to muscles
- branches from C1-4 (can be C5/6 too) anterior spinal nerve roots pass up and over foramen magnum to enter cranial cavity and join with vagus
- traverses the posterior cranial fossa to reach the jugular foramen, briefly meets the cranial portion of the accessory nerve, before exiting the skull (along with the glossopharyngeal and vagus nerves) through jugular foramen and splits to supply 2 muscles
- outside the cranium, the spinal part descends along the internal carotid artery to reach the sternocleidomastoid muscle, which it innervates. It then moves across the posterior triangle of the neck to supply motor fibres to the trapezius.
which 2 muscles are supplied by the (spinal) accessory nerve and which type of innervation is this
- SCM and trapezius (SOMATIC MOTOR innervation only)
- enters the deep surface of both muscles
clinical testing of (spinal) accessory nerves
test the movements that the muscles they innervate carry out:
-movement of head to side and look up (SCM)
-shrug shoulders (trapezius)
(if patients can do the above movements, the nerve is working)
which type of innervation do you get from dorsal spinal roots
sensory
which type of innervation do you get from anterior spinal roots
motor innervation
anterior neck triangle (as a whole): 1-borders 2-apex 3-roof 4-floor 5-contents
1-inferior border of mandible, anterior border of SCM muscles, clavicle (and midline divides further)
2-jugular notch
3-subcutaneous tissue with platysma
4-pharynx, larynx and thyroid gland
5-discussed more within each individual anterior neck triangle division (submandibular, submental, muscular and carotid triangles)
what divides the anterior neck triangle in two (left and right)
anterior midline of the neck
what does the hyoid bone divide anterior triangles into
- suprahyoid triangles (above)
- infrahyoid triangles (below)
suprahyoid triangles
- submental triangle
- submandibular triangles
which bone in the body doesn’t attach to any other bone (floating bone)
hyoid bone
why is the submental triangle different to the rest of the anterior neck triangles
only 1 - present in middle below mandible (there isn’t one on left and right side)
submental neck triangle: 1-borders 2-apex 3-roof 4-floor 5-contents
1-medial border of anterior belly of digastric (on both sides), imaginary midline of the neck, hyoid bone
2-mental protuberance
3-fascia and skin (subcutaneous tissue with platysma)
4-mylohyoid muscle
5-start/origin of anterior jugular vein (small veins that unite to form anterior jugular vein), submental lymph nodes
submental lymph nodes
drain lymph from tongue tip, lower lip and lower incisors
mylohyoid muscle
- forms floor of mouth
- runs from mandible to hyoid bone
submandibular neck triangles: 1-borders 2-apex 3-roof 4-floor 5-contents
1-body of mandible, anterior belly of digastric, posterior belly of digastric
2-hyoid bone (point between anterior and posterior belly of digastric)
3-fascia and skin (subcutaneous tissue with platysma)
4-?
5-submandibular salivary gland (fills most of triangle), facial artery, facial vein, submandibular lymph nodes (sit all over triangle), hypoglossal nerve (CNXII)
facial artery and vein
- supply/drain blood to and from face
- pass over body of mandible right at anterior border of masseter
submandibular lymph nodes
-drain most of tongue, more of teeth (not lower incisors) and area covering eyes
hypoglossal nerve
- CNXII
- hypo=under, glossal=tongue (passes under tongue)
- supplies ALL of the intrinsic muscles of the tongue (APART from the palatoglossus muscle)
- has branch that comes down to supply loop of ansa cervicalis (descendens hypoglossi)
only intrinsic muscle of the tongue not supplied by the hypoglossal nerve
palatoglossus
infrahyoid (anterior) neck triangles
- carotid triangles
- muscular triangles
carotid neck triangles: 1-borders 2-apex 3-roof 4-floor 5-contents
1-posterior belly of digastric, superior border of omohyoid, anterior border of SCM
2-point between omohyoid and posterior belly of digastric, superiorly at attachment to hyoid bone
3-?
4-?
5- carotid sheath, common carotid artery (which bifurcates within the carotid triangle into the external and internal carotid arteries), the internal jugular vein, deep cervical lymph nodes and the hypoglossal and vagus nerves
carotid sheath definition
connective tissue tunnel that surrounds different structures
deep cervical lymph nodes
drain deep lymph of head and neck
contents of carotid sheath
- internal jugular vein
- common carotid artery (then internal carotid artery)
- vagus nerve
- deep cervical lymph nodes
area of bifurcation of common carotid artery into internal and external
laryngeal prominence
laryngeal prominence
- adams apple
- formed by joining of 2 thyroid cartilages
ansa cervicalis
-formed from 2 different nerve fibre bundles
-loop of hypoglossal nerve
-C1,C2,C3 motor fibres
-motor supply to ‘strap muscles’ (except thyrohyoid- supplied by C1)
-C1 motor fibres (descendens hypoglossi)
-C2,C3 motor fibres (descendens cervicalis)
(fibres descend from cervical spinal roots to form loop that supply strap muscles, motor fibres from C1 hitch a ride with the hypoglossal nerve then they split, descendens hypoglossi is where it splits from hypoglossal nerve to meet with descendens cervicalis to form ansa cervicalis, and C1 continues along beside hypoglossal nerve to supply thyrohyoid)
location of ansa cervicalis
not embedded within carotid sheath, either sits just on top of sheath or is imbedded in the connective tissue of the sheath
which strap muscle is not supplied by ansa cervicalis
- thyrohyoid
- supplied by C1
muscular triangles of the neck:
1-borders
2-contents
1-hyoid bone, imaginary midline of neck, inferior portion of anterior border of SCM, superior belly of the omohyoid muscle
2-strap muscles and nerve supply (ansa cervicalis, C1,C2,C3)
strap muscles (in muscular triangle of the neck)
-looks like ribbons/straps
-aka infrahyoid muscles
1-omohyoid
2-sternohyoid
3-sternothyroid
4-thyrohyoid
mylohyoid muscle (attachments, actions and innervation)
- suprahyoid muscle
- the mylohyoid muscle is a broad, triangular shaped muscle
- forms the floor of the oral cavity, thus supporting the floor of the mouth
- attachments: originates from the mylohyoid line of the mandible, and attaches onto the hyoid bone
- actions: elevates the floor of the mouth and the hyoid bone.
- innervation: inferior alveolar nerve, a branch of the mandibular nerve (which is derived from the trigeminal nerve)
digastric muscle (attachments, actions and innervation)
- suprahyoid muscle
- comprised of two muscular bellies, connected by a tendon
- attachments: the anterior belly arises from the digastric fossa of the mandible, the posterior belly arises from the mastoid process of the temporal bone, the two bellies are connected by an intermediate tendon, which is attached to the hyoid bone via a fibrous sling.
- actions: depresses the mandible and elevates the hyoid bone.
- innervation: the two parts of the digastric muscle have different innervations; the anterior belly is innervated by the inferior alveolar nerve, a branch of the mandibular nerve (which is derived from the trigeminal nerve, CN V) and the posterior belly is innervated by the digastric branch of the facial nerve
thyroid cartilage
gives rise to adams apple
function of strap muscles
help depress hyoid bone and help anchor larynx
4 suprahyoid muscles
- stylohyoid
- digastric
- geniohyoid
- mylohyoid
stylohyoid muscle (attachments, actions and innervation)
-suprahyoid muscle
geniohyoid (attachments, actions and innervation)
- suprahyoid muscle
- located deep to the mylohyoid muscle, the geniohyoid lies close to the midline of the neck
- attachments: arises from the inferior mental spine of the mandible, it then travels inferiorly and posteriorly to attach to the hyoid bone.
- actions: depresses the mandible and elevates the hyoid bone.
- innervation: C1 nerve roots that run within hypoglossal nerve
omohyoid muscle (attachments, actions and innervation)
- strap muscle/infrahyoid muscle
- innervation:ansa cervicalis
- split into two bellies, connected by a muscular tendon. It is located slightly laterally to the sternohyoid.
- attachments: the inferior belly of the omohyoid arises from the scapula. It runs superiomedially, moving underneath the sternocleidomastoid. Here, it is attached to the the superior belly by an intermediate tendon. This tendon is attached to the clavicle by the deep cervical fascia. The superior belly ascends to attach to the hyoid bone.
- actions: Depresses the hyoid bone.
- innervation: anterior rami of C1-C3, carried by a branch of the ansa cervicalis
sternohyoid muscle (attachments, actions and innervation)
- strap muscle/infrahyoid muscle
- innervation:ansa cervicalis
- along with the omohyoid, the sternohyoid lies superficially in the neck.
- attachments: the sternohyoid muscle originates from the sternum and sternoclavicular joint. It ascends to insert onto the hyoid bone.
- actions: depresses the hyoid bone.
- innervation: anterior rami of C1-C3, carried by a branch of the ansa cervicalis
sternothyroid muscle (attachments, actions and innervation)
- strap muscle/infrahyoid muscle
- innervation:ansa cervicalis
- deep to sternohyoid and omohyoid
- this muscle is wider and deeper than the sternohyoid
- attachments: the sternothryoid runs from the manubrium of the sternum to the thyroid cartilage.
- actions: depresses the thyroid cartilage.
- innervation: anterior rami of C1-C3, carried by a branch of the ansa cervicalis.
thyrohyoid muscle (attachments, actions and innervation)
- strap muscle/infrahyoid muscle
- deep to sternohyoid and omohyoid
- innervation:has its own nerve supply from C1 (not ansa cervicalis)
- the thryrohyoid muscle is a short band of muscle, located underneath the posterior portions of the omohyoid and sternohyoid muscles. It is a continuation of the sternothyroid muscle.
- attachments: It arises from the thyroid cartilage of the larynx, and ascends to attach to the hyoid bone.
- actions: it depresses the hyoid, however, if the hyoid is fixed, it can raise the larynx.
- innervation: anterior ramus of C1, carried within the hypoglossal nerve
