Triangles & Roots of the Neck Flashcards
How is the neck divided into two main triangles?
By the Sternocleidomastoid (SCM) muscle, forming the anterior and posterior triangles.
What are the boundaries of the anterior triangle?
Mandible (superior), Sternocleidomastoid (lateral), Midline of the neck (medial).
What are the four subdivisions of the anterior triangle?
Submental, Submandibular, Carotid, Muscular triangles.
What are the boundaries of the submental triangle?
Hyoid bone (inferior), anterior bellies of digastric (both sides).
What are the contents of the submental triangle?
Submental lymph nodes, small veins draining into anterior jugular vein.
What are the boundaries of the submandibular triangle?
Mandible (superior), anterior and posterior bellies of digastric.
What are the contents of the submandibular triangle?
Submandibular gland, Facial artery & vein, Hypoglossal nerve (CN XII).
What are the boundaries of the carotid triangle?
Sternocleidomastoid (SCM), posterior belly of digastric, superior belly of omohyoid.
What are the contents of the carotid triangle?
Common carotid artery bifurcation, Internal jugular vein, CN X (Vagus), CN XII (Hypoglossal), Ansa cervicalis.
What are the boundaries of the muscular triangle?
Midline of neck, SCM, Superior belly of omohyoid.
What are the contents of the muscular triangle?
Infrahyoid muscles, Thyroid & Parathyroid glands, Larynx, Trachea.
What are the boundaries of the posterior triangle?
Trapezius (posterior), SCM (anterior), Clavicle (inferior).
What are the two subdivisions of the posterior triangle?
Occipital and Supraclavicular (Subclavian) triangles.
What are the boundaries of the occipital triangle?
Trapezius, SCM, Inferior belly of omohyoid.
What are the contents of the occipital triangle?
CN XI (Accessory nerve), Transverse cervical artery, Posterior cervical lymph nodes.
What are the boundaries of the supraclavicular triangle?
Clavicle, SCM, Inferior belly of omohyoid.
What are the contents of the supraclavicular triangle?
Subclavian artery & vein, Brachial plexus roots.
Origin: manubrium, med. 1/3 clavicle
Insertion: mastoid process
Innervation: Accessory N (CN XI)
Action: Rotation of head to opposite side, flex/rotate neck
SCM
- CAUSE?
Damage to SCM during gestation
Fibrosis (shortening) of SCM - Unlike the normal action of SCM to turn the head away from
that side, this type of torticollis causes the head to tilt toward
(and the face turn away from) the affected side
Affected SCM
TREATMENT?
* Gentle stretching
* Infant stimulation to
encourage movement
* Bracing (Torticollis
Collar)
Congenital torticollis
Posterior triangle boundaries
Trapezius
SCM
Clavicle
Floor of posterior triangle
Floor of Posterior Triangle:
o Anterior, Middle, and Posterior Scalene MM
o Levator Scapula M
**Roots of brachial plexus exit between
Anterior and Middle Scalene
Posterior triangle nerves
Cervical plexus rami (C1-C4)
Lesser occipital N
Great auricular N
Transverse cervical N
Supraclavicular N
Sensory nerves
Cervical plexus block
Erb’s Point (nerve point of neck)
Site for regional anesthesia (cervical plexus block)
Deep Posterior triangle nerves
Phrenic N
* Lies anterior to anterior scalene muscle
* C3-C5
* Diaphragm
CN XI: Spinal Accessory N
* Leaves skull via jugular foramen
* Crosses internal jugular v
* Pierces SCM, continues deep to trapezius
Brachial plexus
* C5-T1
* Emerges between anterior &
middle scalene muscles
Deep Posterior triangle nerves
Phrenic N
* Lies ______ to ______ scalene muscle
* C__-C__ nerve roots
* innervates ______
Phrenic N
* Lies anterior to anterior scalene muscle
* C3-C5 nerve roots
* innervates Diaphragm
Deep Posterior triangle nerves
CN XI: Spinal Accessory N
* Leaves skull via jugular _____
* Crosses _______ jugular v
* Pierces _____, continues deep to ______
CN XI: Spinal Accessory N
* Leaves skull via jugular foramen
* Crosses internal jugular v
* Pierces SCM, continues deep to trapezius
Deep Posterior triangle nerves
Brachial plexus
* C__-T___
* Emerges between _______ & _____ scalene muscles
Brachial plexus
* C5-T1
* Emerges between anterior & middle scalene muscles
boundaries of anterior triangle
SCM
Median line
Inferior Mandible
4 subdivisions of the anterior triangle
Subdivisions:
1. Submental triangle
2. Submandibular triangle
3. Carotid triangle
4. Muscular triangle
Submental triangle boundaries and contents
Boundaries:
* Anterior belly of digastric
* Body of hyoid
* Midline
Contents:
* Lymph nodes from tip of tongue
* Floor of mouth
Submandibular triangle boundaries and contents
Boundaries:
* Bellies of digastric M
* Inferior border of mandible
* Mylohyoid M (roof)
Contents:
* Submandibular gland (*)
* Hypoglossal N
* Nerve to mylohyoid M
* Facial, lingual AA/VV
Submandibular triangle contents
Nerve to Mylohyoid
* Branches off inferior ________ n. (V___)
* ____ innervation to mylohyoid
Nerve to Mylohyoid
* Branches off inferior alveolar n. (V3)
* Motor innervation to mylohyoid
Submandibular triangle contents
Facial Artery
* Branch of _______
* Travels through/deep to _________ gland to cross mandible
* ______ (appearance?)
Facial Artery
* Branch of external carotid a (ECA)
* Travels through/deep to submandibular gland
to cross mandible
* Torturous
Submandibular triangle contents
Lingual Artery
* Branch of ______
* Dives deep to _____
Lingual Artery
* Branch of ECA
* Dives deep to mylohyoid
Submandibular triangle contents
CN XII: Hypoglossal N
* Exits skull via ______ canal
* Crosses _______ a.
* Runs deep to _______ to enter & supply _______ innervation to tongue
CN XII: Hypoglossal N
* Exits skull via hypoglossal canal
* Crosses occipital a.
* Runs deep to mylohyoid to enter & supply motor innervation to tongue
Carotid triangle boundaries and contents
Boundaries:
* Sternocleidomastoid M
* Superior belly of omohyoid M
* Posterior belly of digastric M
Contents:
* CN X, XI, XII
* Ansa cervicalis
* Common carotid A and major branches
* Internal jugular V and major tributaries
Carotid triangle contents
CN X: Vagus Nerve Pathway
* Leaves skull via jugular ______
* Runs in _____ sheath between carotid A. and IJV
* Terminates in lower thorax as ______ trunks,
continues into abdomen
CN X: Vagus Nerve Pathway
* Leaves skull via jugular foramen
* Runs in carotid sheath between carotid A. and IJV
* Terminates in lower thorax as vagal trunks,
continues into abdomen
CN XII: Hypoglossal Nerve Pathway
* Leaves skull via ______ canal
* Crosses internal/external carotid AA at level of
_________ A (deep to ______ A)
* Passes deep to ___________ belly of digastric & ______
CN XII: Hypoglossal Nerve Pathway
* Leaves skull via hypoglossal canal
* Crosses internal/external carotid AA at level of
lingual A (deep to occipital A)
* Passes deep to posterior belly of digastric & mylohyoid
Carotid body
* Chemoreceptors (SENSE BLOOD pH+, pCO2, pO2)
* Innervated by CN IX
ARTERIES
External carotid A (Branches in the neck)
Common carotid A - Bifurcation at C4
Internal carotid A (ascends directly to cranial cavity)
WHAT IS IT? Removal of atherosclerotic plaque from the carotid arteries (usually at the
bifurcation)
* CAUTION? What is near the carotid arteries? CRANIAL NERVES! CN IX, CN X (Superior
Laryngeal N), CN XI, or CN XII
Carotid endarterectomy
Carotid sinus
* Base of internal carotid
* Baroreceptors (sense BLOOD PRESSURE)
* Innervated by CN IX
Muscular triangle boundaries and contents
Boundaries:
* Midline
* Superior belly of omohyoid
* Anterior border of SCM
Contents:
* Thyroid gland
* Parathyroid glands
* Infrahyoid muscles
Thyroid gland
FUNCTIONS:
* Endocrine gland
* Thyroid gland: Thyroxine & Calcitonin
o Controls metabolic rate, muscle & digestive
function, bone maintenance, and maintains
blood calcium levels
* Parathyroid gland: Parathyroid Hormone
o Maintain blood calcium levels
Location of the thyroid gland:
Wraps cricoid cartilage, trachea (C5 – T1 level)
* Deep to infrahyoid (“strap”) muscles, covered in
pretracheal fascia
Location of the thyroid gland:
Wraps cricoid cartilage, trachea (C5 – T1 level)
* Deep to infrahyoid (“strap”) muscles, covered in
pretracheal fascia
Parathyroid glands
-4 Total (2 Superior & 2 Inferior)
-Lie posteriorly
Thyroglossal duct: Embryological connection between the tongue and thyroid
Can persist as:
* Pyramidal lobe
Thyroid gland arteries
superior (external carotid a) and inferior thyroid arteries (thyrocerevical trunk)
thyroid gland veins
SUPERIOR & MIDDLE THYROID VEINS –> Drain into internal jugular veins –> to brachiocephalic veins at the venous angle
INFERIOR THYROID
VEIN
to brachiocephalic
vein directly
HYOID BONE
* Suspended in neck at C3 (no bony articulations)
* Anchor for neck muscles, jaw, tongue, pharynx
* Bony support for airway (suspends laryngeal skeleton)
* Mobile during swallowing
SUPRAHYOID MUSCLES:
* All insert on hyoid;
elevate/protract during
swallowing
* Hyoid fixed: depress mandible
Mylohyoid M: Attaches to mylohyoid line of mandible
Digastric M: Anteriorly: attaches to mandible
Posteriorly: mastoid notch
Stylohyoid M: styloid process
Geniohyoid M
Facial N (CN VII)
* Motor branches exit stylomastoid foramen
Innervates:
* Stylohyoid M
* Digastric M (post. belly)
Genohyoid M:
C1 branch to Geniohyoid M
* carried on CN XII
Mylohyoid N (from CN V3)
* Mylohyoid M
* Digastric M (ant. belly)
INFRAHYOID MUSCLES:
* Fix hyoid (stabilize), depress larynx after swallowing
* Innervated by ansa cervicalis (cervical plexus, C1-C3)
* Thyrohyoid M innervated by C1 (via CN XII)
Strap Muscles:
Thyrohyoid M
Sternohyoid M
Sternothyroid M
Omohyoid M (two bellies)
Ansa cervicalis (motor only)
(from cervical plexus, C1-C3)
*Superior root (C1)
*Inferior root (C2-C3)
* Careful : Ansa cervicalis lies just
anterior to carotid sheath
