Surface anatomy of the neck and clavicular region Flashcards
What are the borders of the anterior triangle of the neck
- Superior: body of the mandible
- Posteriorly: anteiror border of sternocleidomastoid
- The two anterior triangles meet in the midline and the two apices meet at the suprasternal notch
What structures are found in the anterior triangle of the neck?
- Vessels (2)
- Nerves (4)
- Other structures (5)
- Carotid and jugular vessels [NOT external jugular vein]
- CN 9, 10, 11, 12 (glossopharyngeal, vagus, accessory, hypoglossal)
- Salivary glands including lower pole of the parotid gland
- Larynx, pharynx, trachea, thyroid
What are borders of the posterior triangle of the neck
Anterior: posterior border of SCM
Posterior: anterior edge of trapezius
Base: mid-third of the clavicle
What structures are found in the posterior triangle of the neck
* vessels (3)
* nerves (3)
- Subclavian artery (3rd part)
- Occasionally, subclavian vein
- External jugular vein
- Brachial and cervical plexi
- Accessory nerve (CN 11)
Describe the mandible
Forms the superior border of the anterior triangle of the neck
Ramus descends from the temperomandibular joint into the** angle** which turns forwards as the **body **of the mandible
Describe the clavicle
- Runs between the sternoclavicular (SCJ) and acromioclavicular (ACJ) joints
- SCJ joins wi thte manibrium sterni
- ACJ joins the acromium
Describe the sternocleidomastoid muscle.
What manouvre makes it more prominent?
Two heads, which unite in the mastoid process of the skull
* Tendonous: runs from sternum
* Muscular: runs from medial third of clavicle
Asking the patient to put their left ear to their shoulder and then look upwards and rightwards against resistance will cause the left SCM to stand out (and vice versa)
Describe the trapezius muscle
Runs from the occiput and C7-T12 spines to the** scapula** and lateral third of clavicle.
Asking the patient to shrug the shoulders against resistance will cause it to stand out
Describe the carotid sheath
* Contents (4)
* Course (cranial and caudal limits)
* Point where arterial pulsation is most prominent
A fascial sheath containing
* Carotid arteries
* Internal jugular vein
* Vagus nerve
* Deep cervical lymph nodes
Runs through the anterior triangle along a line:
* caudal limit: sternoclavicular joint (or suprasternal notch)
* cranial limit: **midway between the tip of the mastoid process and angle of the mandible **
The common carotid artery bifurcates at the level of the upper edge of the thyroid cartilage - arterial pulsation is most prominent at this level
Describe the relations of the structures in the carotid sheath
What complications could arise from directing the needle to medially when attempting to cannulate the internal jugular vein
- Carotid puncture -> expanding haematoma -> airway compression
- Rarely: direct injury to airway structures
- Injury to vagus or phrenic nerves
The arteries are located MEDIAL to the vein, ANTERIOR to the vagus nerve
Describe the course of the subclavian artery
- The third part (most proximal) runs through the anterior-inferior apex of the posterior triangle, arching convexly upwards between the sternoclavicular joint and midpoint of the clavicle
- Can be palpated here, and firm pressure on the first rib can be used to control life-threatening upper limb haemorrhage
- Lies deep and posterior to the subclavian vein (which rarely rises above the clavicle)
- Runs out laterally, crosses over the lateral edge of the first rib
- Becomes the axillary artery
Describe the axillary artery
Subclavian artery becomes the axillary artery as it crosses over the lateral edge of the first rib
Lies deep to the coracoid process (the most anterior projection of the scapula which can be palpated just below the lateral 1/3 of the clavicle)
Pectoralis minor (which arises from the coracoid process) demarcates the second part of the artery from the first (medial) and third (lateral) parts
What lies behind the subclavian vessels and the medial third of the clavicle?
The dome of the pleura
-> may be injured by penetrating trauma or attempts to cannulate the cental venous system -> pneumo or haemo-thorax
Describe the external jugular vein
The principal vessel draining venous blood from the tissues of the face and neck.
* Superficial tissues of neck, behind the angle of the mandible
* Drops through deep fascia approx 2cm cephalad to the clavicle
* Drains into the subclavian vein (there is a 90 degree junction and usually a valve at this point which typically precludes central cannulation).
Can be visualised by asking the patient to perform a valsalva manouvre
Describe the position of the brachial plexus
Key fact: The brachial plexus roots emerge in the interscalene groove posterior to SCM and the cords are related to the second part of the axillary artery
- Roots emerge between the scalenus anterior and medius muscles via the interscalene groove (behind the SCM, anterior to external jugular)
- Cephalad limit is a line from the cricoid cartillage to the clavicular midpoint
- Trunks run through the lower part of the posterior triangle with the third part of the subclavian artery. Upper and middle trunks lie above the artery, lower trunk lies behind. Closely related to the pleura here: risk of PTX if trying to block plexus at this level
- Divisions form laterally as the plexus continues behind the clavicle
- Cords from from the divisions in the axilla, and are initially lateral and superior to the axillary artery
To what structure do the cords of the brachial plexus relate in order to get their respective names - medial, lateral and posterior?
The second part of the axillary artery: the part lying behind pectoralis minor
Describe the cervical plexus (there are 4 nerves)
Emerges behind the midpoint of posteior border of SCM into the posterior triangle
- Lesser occipital N: follows posteiror border of SCM upwards
- Greater auricular N: runs over SCM directly cephalad toward the pina
- Transverse cervical nerves: pass forwards over the SCM to the anterior region of the neck
- Supraclavicular nerves: descend in fan-like distribution towards the clavicle below
