Triangles & Roots of the Neck

Question 1

How is the neck divided into two main triangles?

Answer 1

By the Sternocleidomastoid (SCM) muscle, forming the anterior and posterior triangles.

Question 2

What are the boundaries of the anterior triangle?

Answer 2

Mandible (superior), Sternocleidomastoid (lateral), Midline of the neck (medial).

Question 3

What are the four subdivisions of the anterior triangle?

Answer 3

Submental, Submandibular, Carotid, Muscular triangles.

Question 4

What are the boundaries of the submental triangle?

Answer 4

Hyoid bone (inferior), anterior bellies of digastric (both sides).

Question 5

What are the contents of the submental triangle?

Answer 5

Submental lymph nodes, small veins draining into anterior jugular vein.

Question 6

What are the boundaries of the submandibular triangle?

Answer 6

Mandible (superior), anterior and posterior bellies of digastric.

Question 7

What are the contents of the submandibular triangle?

Answer 7

Submandibular gland, Facial artery & vein, Hypoglossal nerve (CN XII).

Question 8

What are the boundaries of the carotid triangle?

Answer 8

Sternocleidomastoid (SCM), posterior belly of digastric, superior belly of omohyoid.

Question 9

What are the contents of the carotid triangle?

Answer 9

Common carotid artery bifurcation, Internal jugular vein, CN X (Vagus), CN XII (Hypoglossal), Ansa cervicalis.

Question 10

What are the boundaries of the muscular triangle?

Answer 10

Midline of neck, SCM, Superior belly of omohyoid.

Question 11

What are the contents of the muscular triangle?

Answer 11

Infrahyoid muscles, Thyroid & Parathyroid glands, Larynx, Trachea.

Question 12

What are the boundaries of the posterior triangle?

Answer 12

Trapezius (posterior), SCM (anterior), Clavicle (inferior).

Question 13

What are the two subdivisions of the posterior triangle?

Answer 13

Occipital and Supraclavicular (Subclavian) triangles.

Question 14

What are the boundaries of the occipital triangle?

Answer 14

Trapezius, SCM, Inferior belly of omohyoid.

Question 15

What are the contents of the occipital triangle?

Answer 15

CN XI (Accessory nerve), Transverse cervical artery, Posterior cervical lymph nodes.

Question 16

What are the boundaries of the supraclavicular triangle?

Answer 16

Clavicle, SCM, Inferior belly of omohyoid.

Question 17

What are the contents of the supraclavicular triangle?

Answer 17

Subclavian artery & vein, Brachial plexus roots.

Question 18

Origin: manubrium, med. 1/3 clavicle
Insertion: mastoid process
Innervation: Accessory N (CN XI)
Action: Rotation of head to opposite side, flex/rotate neck

Answer 18

SCM

Question 19

• 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)

Answer 19

Congenital torticollis

Question 20

Posterior triangle boundaries

Answer 20

Trapezius
SCM
Clavicle

Question 21

Floor of posterior triangle

Answer 21

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

Question 22

Posterior triangle nerves

Answer 22

Cervical plexus rami (C1-C4)

Lesser occipital N
Great auricular N
Transverse cervical N
Supraclavicular N
Sensory nerves

Question 23

Cervical plexus block

Answer 23

Erb’s Point (nerve point of neck)
Site for regional anesthesia (cervical plexus block)

Question 24

Deep Posterior triangle nerves

Answer 24

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

Question 25

# Deep Posterior triangle nerves Phrenic N * Lies ______ to ______ scalene muscle * C__-C__ nerve roots * innervates ______

Answer 25

Phrenic N * Lies anterior to anterior scalene muscle * C3-C5 nerve roots * innervates Diaphragm

Question 26

# Deep Posterior triangle nerves CN XI: Spinal Accessory N * Leaves skull via jugular _____ * Crosses _______ jugular v * Pierces _____, continues deep to ______

Answer 26

CN XI: Spinal Accessory N * Leaves skull via jugular foramen * Crosses internal jugular v * Pierces SCM, continues deep to trapezius

Question 27

# Deep Posterior triangle nerves Brachial plexus * C__-T___ * Emerges between _______ & _____ scalene muscles

Answer 27

Brachial plexus * C5-T1 * Emerges between anterior & middle scalene muscles

Question 28

boundaries of anterior triangle

Answer 28

SCM Median line Inferior Mandible

Question 29

4 subdivisions of the anterior triangle

Answer 29

Subdivisions: 1. Submental triangle 2. Submandibular triangle 3. Carotid triangle 4. Muscular triangle

Question 30

Submental triangle boundaries and contents

Answer 30

Boundaries: * Anterior belly of digastric * Body of hyoid * Midline Contents: * Lymph nodes from tip of tongue * Floor of mouth

Question 31

Submandibular triangle boundaries and contents

Answer 31

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

Question 32

# Submandibular triangle contents Nerve to Mylohyoid * Branches off inferior ________ n. (V___) * ____ innervation to mylohyoid

Answer 32

Nerve to Mylohyoid * Branches off inferior alveolar n. (V3) * Motor innervation to mylohyoid

Question 33

# Submandibular triangle contents Facial Artery * Branch of _______ * Travels through/deep to _________ gland to cross mandible * ______ (appearance?)

Answer 33

Facial Artery * Branch of external carotid a (ECA) * Travels through/deep to submandibular gland to cross mandible * Torturous

Question 34

# Submandibular triangle contents Lingual Artery * Branch of ______ * Dives deep to _____

Answer 34

Lingual Artery * Branch of ECA * Dives deep to mylohyoid

Question 35

# Submandibular triangle contents CN XII: Hypoglossal N * Exits skull via ______ canal * Crosses _______ a. * Runs deep to _______ to enter & supply _______ innervation to tongue

Answer 35

CN XII: Hypoglossal N * Exits skull via hypoglossal canal * Crosses occipital a. * Runs deep to mylohyoid to enter & supply motor innervation to tongue

Question 36

Carotid triangle boundaries and contents

Answer 36

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

Question 37

# 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

Answer 37

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

Question 38

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 & ______

Answer 38

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

Question 39

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)

Question 40

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

Answer 40

Carotid endarterectomy

Question 41

Carotid sinus * Base of internal carotid * Baroreceptors (sense BLOOD PRESSURE) * Innervated by CN IX

Question 42

Muscular triangle boundaries and contents

Answer 42

Boundaries: * Midline * Superior belly of omohyoid * Anterior border of SCM Contents: * Thyroid gland * Parathyroid glands * Infrahyoid muscles Thyroid gland

Question 43

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

Question 44

Location of the thyroid gland: Wraps cricoid cartilage, trachea (C5 – T1 level) * Deep to infrahyoid (“strap”) muscles, covered in pretracheal fascia

Answer 44

Location of the thyroid gland: Wraps cricoid cartilage, trachea (C5 – T1 level) * Deep to infrahyoid (“strap”) muscles, covered in pretracheal fascia

Question 45

Parathyroid glands -4 Total (2 Superior & 2 Inferior) -Lie posteriorly

Question 46

Thyroglossal duct: Embryological connection between the tongue and thyroid Can persist as: * Pyramidal lobe

Question 47

Thyroid gland arteries

Answer 47

superior (external carotid a) and inferior thyroid arteries (thyrocerevical trunk)

Question 48

# thyroid gland veins SUPERIOR & MIDDLE THYROID VEINS --> Drain into internal jugular veins --> to brachiocephalic veins at the venous angle

Question 49

INFERIOR THYROID VEIN to brachiocephalic vein directly

Question 50

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

Question 51

SUPRAHYOID MUSCLES: * All insert on hyoid; elevate/protract during swallowing * Hyoid fixed: depress mandible

Question 52

Mylohyoid M: Attaches to mylohyoid line of mandible Digastric M: Anteriorly: attaches to mandible Posteriorly: mastoid notch Stylohyoid M: styloid process Geniohyoid M

Question 53

Facial N (CN VII) * Motor branches exit stylomastoid foramen Innervates: * Stylohyoid M * Digastric M (post. belly)

Question 54

Genohyoid M: C1 branch to Geniohyoid M * carried on CN XII

Question 55

Mylohyoid N (from CN V3) * Mylohyoid M * Digastric M (ant. belly)

Question 56

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)

Question 57

Strap Muscles: Thyrohyoid M Sternohyoid M Sternothyroid M Omohyoid M (two bellies)

Question 58

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