Anatomy of Anterior and Posterior Neck Flashcards
What is the neck?
Region of the body lying between:
- the lower margin of mandible and superior nuchal line of the occipital bone above
- and the suprasternal notch and upper border of clavicles below
Describe the innervation of the skin of the neck?
At the back – supplied segmentally by posterior rami of c2-c5
At front and sides – supplied by anterior rami of c2-c4
Describe the superficial fascia of the neck?
forms a thin layer that encloses the platysma muscle.
> embeds cutaneous nerves, superficial vessels & lymphatics
Describe the deep fascia of the neck?
consists of areolar tissue that supports muscles, vessels and viscera
What are the fibrous sheets of the deep fascia?
- Investing layer - surrounds all structures in the neck
- pre-tracheal layer
- prevertebral layer
- carotid sheath
Name the 3 compartments of the neck and their contents?
- Visceral Compartment
- Digestive and respiratory systems + several endocrine glands - Vertebral Compartment
- Cervical vertebrae, spinal cords, cervical nerves, associated muscles - Vascular Compartments
- Major blood vessels and vagus nerve [X]
What divides the neck into anterior and posterior triangles?
sternocleidomastoid
What are the boundaries of the anterior triangle?
- Anterior border: Imaginary midline of the neck
- Posterior Border: Anterior border of SCM
- Superiorly (Base): inferior margin of mandible
> The roof is formed by skin, superficial fascia, platysma and investing layer of deep fascia
What are the 4 divisions of the anterior triangles?
- submandibular (digastric)
- submental
- carotid
- muscular
Which muscles form the 4 divisions of the anterior triangle?
- digastric muscles
- superior belly of Omohyoid
What are the contents of the submental division of the anterior triangle?
- submental lymph nodes
- beginning of anterior jugular vein
What are the contents of the submandibular division of the anterior triangle?
- submandibular salivary gland
- lymph nodes
- facial artery & vein
- carotid sheath
- hypoglossal nerve
What are the contents of the carotid division of the anterior triangle?
- carotid sheath
- branches of external carotid artery
- internal jugular vein
- hypoglossal
- accessory and vagus nerves
What are the contents of the muscular division of the anterior triangle?
sternohyoid and sternothyroid form the floor beneath which lies the:
- thyroid gland
- larynx
- trachea
- oesophagus
Name the supra-hyoid muscles of the anterior triangle and their action?
Stylohyoid
digastric
mylohyoid
geniohyoid
> Raise hyoid bone or depress mandible (mylohyoid and digastric)
What is the innervation of the supra-hyoid muscles?
- Facial nerve
> posterior belly of digastric and stylohyoid - Mandibular division of trigeminal CNV3
> anterior belly of digastric and mylohyoid - branches from anterior ramus of C1 carried along the Hypoglossal nerve [XII]
> geniohyoid
What are the infrahyoid muscles and what is their action?
Omohyoid
sternohyoid
thyrohyoid
Sternothyroid
- depress hyoid bone
Note: Names indicate sites of attachment
What is the innervation of the infrahyoid muscles?
Ansa cervicalis
> except thyrohyoid = C1 via hypoglossal CN XII
Describe the cervical plexus?
- Anterior rami C1-4
- Joined into loops that lie anterior to levator scapulae and scalenus medius
- Covered by pre-vertebral layer of deep cervical fascia
- Somatic motor and sensory (plus sympathetic)
Describe the course of the vagus nerve?
Descends in carotid sheath
Recurrent laryngeal branches to muscles of larynx = L around arch of aorta, R around subclavian artery
Internal and external laryngeal branches
Through thoracic inlet into superior mediastinum – parasympathetic to thorax and abdomen
Describe the course of the common carotid artery?
LCA from arch of aorta
RCA from brachiocephalic
No branches but terminal 2 = internal and external
Internal carotid to brain
External carotid to head, face, neck
Within carotid sheath with internal jugular vein and vagus nerve
Describe the thyroid gland in the anterior triangle?
Endocrine – regulates metabolic rate
2 lobes, isthmus and capsule
From lamina of thyroid cartilage down to 6th tracheal ring
Isthmus over tracheal ring 2 or 3
Parathyroid glands embedded into posterior surface
Describe the arterial supply of the thyroid gland?
Describe the venous drainage of the thyroid gland?
Describe the course of the submandibular salivary gland?
Inferior to mylohyoid, plus part in floor of mouth superior to mylohyoid
One duct each side opens between the first and second lower incisor (either side of frenelum)
What are the borers of the posterior triangle?
- anterior - posterior border of SCM
- posterior - anterior border of trapezius
- base - clavicle
- Floor - splenius capitis, levator scapulae, posterior, middle and anterior scalene muscles
> The floor is formed by prevertebral layer of deep fascia
> The triangle is covered by skin, sup fascia, platysma, and investing layer of deep fascia (roof)
What are the contents of the posterior triangle?
external jugular vein
roots of brachial plexus
accessory nerve
cervical and supra-clavicular lymph nodes
Occipital artery
3rd part of subclavian
Lateral branches of thyrocervical trunk
Describe the floor of the posterior triangle?
- Omohyoid
• Superior border of scapula - inferior border of hyoid bone
• Depress hyoid bone - Ansa cervicalis
- Splenius capitis
• Nuchal ligament, spinous process of C7-T4 to mastoid process
• Extend the neck, rotate - Dorsal rami middle cervical
Cutaneous branches of cervical plexus running across the posterior triangle?
- lesser occipital (C2)
- great auricular (C2,3)
- lateral supraclavicular (C3,4)
- intermediate supraclavicular (C3,4)
- medial supraclavicular (C3,4)
- transverse cervical (C2,3)
Locations of nerves of the posterior triangle?
- CN XI crosses obliquely on surface of L. scapulae
- phrenic nerve - crosses obliquely over anterior scalene
- brachial plexus - passing between middle and anterior scalene
What are the divisions of the posterior triangle and what separates these divisions?
- Occipital triangle (larger – above)
- Supraclavicular triangle (smaller – below)
> subdivided by inferior belly of omohyoid
Describe the action of the sternocleidomastoid muscle?
- unilateral = lateral flexion of neck to same side (face opposite)
- bilateral = flexion of neck
Describe the innervation of the sternocleidomastoid muscle?
motor = spinal accessory nerve (CN XI)
pain and proprioception = cervical plexus C2, C3
Describe the action of the trapezius muscle?
- ascending part (inferior) = depress scapula
- transverse part (middle) = retracts scapula
2 descending part (superior) = elevate scapula, rotate glenoid cavity
> holds scapula in position - weightlifting
Describe the innervation of the trapezius muscle?
spinal accessory nerve (CN XI), cervical plexus C3,C4 (proprioception)
Describe the action of the levator scapulae muscle?
Help control scapular position, elevate shoulder (with trapezius), shoulder fixed can laterally flex neck to the same side
Location of levator scapulae?
Transverse processes of atlas and axis, 3rd and 4th C vertebrae to medial scapular border between superior angle and medial end of scapular spine
Location of scalene muscles?
Origin:
From transverse processes of:
1. C3-6 (anterior),
2. C2-7 (middle)
3. C4-6 (posterior)
Insertion:
1. To ribs 1 (scalene tubercle m) = anterior
2. Upper surface of rib 1 = middle
- Artery lies between it and tubercle
3. Upper surface of rib 2 (posterior)
Innervation of scalene muscles?
- anterior - ant. rami C4-7
- middle - ant. rami C3-7
- posterior - ant. rami C5-7
Action of scalene muscles?
flex neck (bilateral)
tilt head to same side (unilateral)
elevate upper ribs
What is an emergency cricothyroidotomy?
an incision made through the skin and cricotyroid membrane to establish a patent airway during certain life-threatening situations
e.g. airway obstruction by foreign body, angioedema or massive facial trauma
