Anterior Triangle of the Neck Flashcards
What divides the anterior from the posterior triangle?
Sternocleidomastoid
Boundaries of the anterior triangle?
Anterior border = imaginary midline of the neck
Posterior border = anterior border of SCM
Base = mandible
Divisions of anterior triangle?
Contents?
Submental – submental lymph nodes, beginning of anterior jugular vein
Submandibular – submandibular salivary gland, submandibular lymph nodes, facial artery & vein, carotid sheath, hypoglossal nerve
Carotid – carotid sheath, branches of external carotid artery, internal jugular vein, hypoglossal, accessory and vagus nerves
Muscular – sternohyoid and sternothyroid form the floor beneath which lies the thyroid gland, larynx, trachea and oesophagus
Label divisions of anterior triangle
Label fascial layers of the neck
The superficial cervical fascia lies close to the skin and the deep fascia is divided into sections that surround structures such as the carotid arteries and muscles of the neck.
Label fascial layers of the neck
platysma attachments?
Innervation?
From fascia above pectoralis major and clavicle to —> lateral neck and mandible
Facial nerve CN VII (muscle of facial expression)
Function of platysma?
classed as a muscle of facial expression, even though it acts to tighten the skin of the neck
Platysma
Label superficial veins of the neck + face
Superficial veins of the neck? - found?
External jugular = anterior to SCM (post triangle)
Internal jugular = posterior to SCM (ant triangle)
Anterior jugular = midline, may be absent
External jugular vein anatomical relation?
Tributary? Drains?
External jugular vein crosses anterior surface of sternocleidomastoid
Posterior division of the retromandibular vein joins external jugular vein –> into the subclavian vein
Tributaries internal jugular vein?
Found?
Drains?
Facial vein joins anterior division of the retromandibular vein —> drains into internal jugular vein
IJV lies deeper in the neck, within the carotid sheath
Joins subclavian vein to form brachiocephalic vein (one each side)
Anterior jugular vein drains?
drain into the external or internal veins depending on the individual
Cervical plexus formed from?
Found?
Covered by?
Function?
C1-C4 anterior rami
joined into loops that lie anterior to levator scapulae and scalenus medius
Covered by pre-vertebral layer of deep cervical fascia
Function = motor supply to muscles in anterior triangle + sensory to skin of neck (also some sympathetic)
Label branches of cervical plexus
Label branches of cervical plexus
Label both motor + sensory branches of cervical plexus
Include nerve roots
What is the ansa cervicalis?
Function?
The motor branches supply some of the supra and infra hyoid muscles of the neck and form a loop of nerve tissue – an ‘ansa’ to do this.
The ansa cervicalis contains nerve fibres from C1 to C3
Which bone is this?
Where is it found?
Hyoid bone
Found between mandible + larynx
Muscles attached to hyoid bone divided into?
Muscles attach to the hyoid bone – some from above the hyoid – ‘suprahyoid’ muscles and some from below the hyoid – ‘infrahyoid’ muscles
Suprahyoid muscles?
Function?
Digastric, mylohyoid, geniohyoid, stylohyoid
raise hyoid bone (but digastric and mylohyoid can also depress mandible)
Label suprahyoid muscles
Attachments suprahyoid muscles?
Digastric muscle has two bellies - divided by a small tendon that passes through a loop of connective tissue attached to hyoid bone. A
Anterior belly = attaches to mandible
Posterior belly = to mastoid process of the temporal bone
Stylohyoid = attaches to styloid process of the temporal bone + hyoid
Mylohyoid = attaches to mylohyoid line of mandible + hyoid
Geniohyoid = attaches to inferior genial tubercle of the mandible + hyoid
Which muscle forms diaphragm in floor of oral cavity?
Which muscle lies deep to this muscle?
Mylohyoid
Geniohyoid lies deep to mylohyoid
Innervation suprahyoid muscles?
Stylohyoid + posterior belly of digastric = facial nerve
Mylohyoid + anterior belly of digastric = mandibular division of trigeminal CNV3
Geniohyoid = C1 via hypoglossal CN XII
(facial nerve exits the skull via the stylomastoid foramen so will pass close to both the posterior head of digastric and to stylohyoid)
Infrahyoid muscles?
Also called?
Function?
Omohyoid, sternohyoid, thyrohyoid, sternothyroid
Also called strap muscles because of their shape
Function = depress hyoid bone + thyroid cartilage
Label infrahyoid muscles
Label
Superficial vs deep infrahyoid muscles?
Attachments?
Innervation?
Superficial muscles = omohyoid + sternohyoid,
Deeper muscles = sternothyroid + thyrohyoid
Thyrohyoid = attaches to thyroid cartilage + hyoid
Sternothyroid = sternum + thyroid
Sternohyoid = sternum + hyoid
Omohyoid superior belly = attaches to hyoid bone, becomes tendinous near the clavicle + passes through fascial sling attached to clavicle.
Inferior belly = attaches to scapula
All of the muscles are innervated by the ansa cervicalis except thyrohyoid = C1 via the hypoglossal nerve
Which structure is indicated by white dotted line
Ansa cervicalis
Common carotid artery origins?
Branches?
LCA = from arch of aorta RCA = from brachiocephalic
Branches = only terminal 2 branches, internal + external carotid
label
level of bifurcation of common carotid?
Internal carotid artery found?
Function of internal + external?
Where are they both found?
Between thyroid cartilage + hyoid bone (level C3/C4)
Just to confuse everyone - internal carotid lies external to external carotid at the bifurcation but becomes internal as it passes into the skull (external carotid remains on the external surface of the head to supply the face and neck)
External = head, face + neck Internal = brain
Both found in carotid sheath with internal jugular vein + vagus nerve
carotid sheath lies posterior to?
contents?
sternocleidomastoid
internal jugular vein, common carotid artery + lying between them, the vagus nerve
Branches of external carotid that lie in anterior triangle?
Supply?
Superior thyroid artery - thyroid gland
Facial artery - face
Lingual artery - tongue
Label branches of external carotid
Label branches of subclavian artery
Function?
The subclavian artery supplies blood to the upper limb but branches from the first part of the subclavian artery also supply the thoracic wall (internal thoracic branch), the brain (the vertebral branch) and structures in the neck (thyrocervical trunk).
Vagus nerve found?
Branches?
Carotid sheath
recurrent laryngeal branches to muscles of larynx (left around arch of aorta, right around subclavian artery)
Internal + external laryngeal branches
also gives parasympathetic supply to thorax and abdomen
Vagus nerve
What nerve is found in the neck between the oesophagus + trachea?
Recurrent laryngeal
thyroid gland?
structure?
level?
what is found on posterior surface?
endocrine gland that regulated metabolic rate
structure = 2 lobes, isthmus + capsule
from lamina of thyroid cartilage down to 6th tracheal ring (isthmus over ring 2/3)
parathyroid glands found on posterior surface
where does [blank] lie deep to?
thyroid gland is covered by the infra hyoid muscles
arterial supply to thyroid gland?
branch from?
superior thyroid + inferior thyroid arteries
Superior thyroid is the first anterior branch of the external carotid artery
Inferior thyroid is a branch of the thyrocervical trunk of the subclavian artery
Venous drainage of thyroid gland?
Where do they drain?
Superior, middle and inferior thyroid veins
superior + middle thyroid veins drain into internal jugular vein
both inferior veins drain into left brachiocephalic vein
submandibular salivary gland found?
ducts open into?
Innervation?
Inferior to mylohyoid
part in floor of mouth superior to mylohyoid
one duct each side = open between 1st + 2nd lower incisor (either side of frenelum)
Facial nerve CN VII (parasymp secretomotor)
what crosses submandibular salivary gland?
crossed by the facial vein
submandibular gland
lymphatic drainage thyroid?
thoracic duct empties?
Thoracic duct empties lymph into the venous system deep in the anterior triangle.
At the junction of the internal jugular and subclavian veins (as they form the brachiocephalic vein)
Photograph A shows the external jugular vein as it crosses the anterior surface of sternocleidomastoid to pass into the posterior triangle and drain into the subclavian vein. A vein communicating between the facial vein and the external jugular vein can also be seen. This vein may be present and/or an anterior jugular vein may be present.
Photograph B shows that the great auricular nerve also crosses the anterior surface of sternocleidomastoid as it passes from the cervical plexus towards the skin. The nerves shown by the white dotted line are lying in the posterior triangle but also appear from beneath the posterior border of sternocleidomastoid, they are the supraclavicular nerves.
Photograph A shows omohyoid muscle that has two bellies. The superior belly attaches to the hyoid bone and crosses the anterior triangle, the inferior belly crosses the posterior triangle and attaches to the scapula.
Photograph B shows the muscle that lies medial to omohyoid – sternohyoid. As its name suggests, this muscle lies between the sternum and the hyoid bone.
Both muscles are innervated by the ansa cervicalis.
Photograph A shows omohyoid and sternohyoid reflected to reveal sternothyroid. It passes between the sternum and the thyroid cartilage, so it acts to depress the thyroid cartilage. As the thyroid cartilage and hyoid bone are joined by connective tissue this will also depress the hyoid bone. Sternothyroid is innervated by the ansa cervicalis.
Photograph B shows thyrohyoid, it passes between the thyroid cartilage and the hyoid bone. This muscle is innervated by nerves from C1 that are carried in the hypoglossal nerve (CN XII).
Photograph A shows the anterior triangle when sternocleidomastoid has been reflected. This reveals the carotid sheath – a fascial sheath that surrounds the great vessels of the neck. The black dotted line indicates the position of the ansa cervicalis nerve loop that lies on the anterior surface of the sheath.
Photograph B shows the contents of the carotid sheath – the common carotid artery, internal jugular vein and, lying between them, the vagus nerve. The ansa cervicalis is also shown but, in life, this lies outside the carotid sheath.
