W2: Organisation of the neck

Question 1

Important landmarks and levels

Answer 1

• Hyoid ( Body, greater horn) –C3
• Thyroid cartilage –C4 & C5
• Cricoid cartilage –C6
• External occipital protuberance
• Spine C7 ( vertebral prominence)

Question 2

Describe hyoid bone

Answer 2

Has body and greater and lesser horns

Question 3

Where does the thyroid gland lie in the neck?

Answer 3

The isthmus of the thyroid gland lies at the level of the 2nd and 3rd tracheal cartilage rings

Question 4

Which triangles do we have?

Answer 4

The neck may be divided into two anatomical triangles, bordered by the sternocleidomastoid and trapezius muscles:

• Anterior triangle – area between the mid-line anteriorly and the anterior border of sternocleidomastoid posteriorly, bounded superiorly by the lower jaw. Subdivided into a further 3 triangles.
• Posterior triangle – area between sternocleidomastoid and the trapezius muscles, bounded inferiorly by the middle 1/3rd of the clavicle.
  
  • Submandibular triangle
  • Carotid triangle
  • Muscular triangle

Question 5

Discuss posterior triangle

Answer 5

Bounded by sternocleidomastoid (anterior) and trapezius (posterior) and the middle 1/3 of clavicle (inferior) forms the base

Contents:

Nerves:

• Spinal accessory nerve - sternocleidomastoid and trapezius - superficial and vulnerable to injury
• Cutaneous nerves (cervical plexus) (Lesser occipital nerve (C2) ,Great Auricular nerve(C2,C3),Transverse cervical cutaneous nerve (C2,C3),Supraclavicular nerve (C3,C4) - also phrenic
• Trunks of brachial plexus

Vasculature:

• Subclavian artery (3rd part)
• Branches of Subclavian artery
• Subclavian vein (central catheter)
• External jugular vein (fromed by retromandicular and posterior auricular) - superficially - emplies into subclavian vein

Muscles:

• omohyoid crosses
• Floor
  
  • Lev scap
  • Scalenes

Question 6

What are the boundaries of anterior triangle?

Answer 6

Superiorly – inferior border of the mandible (jawbone).

Laterally – anterior border of the sternocleidomastoid.

Medially – sagittal line down the midline of the neck.

Question 7

What can the anterior triangle be split into?

Answer 7

Carotid

Submental

Submandibular

Muscular

Question 8

Discuss carotid triangle

Answer 8

The carotid triangle of the neck has the following boundaries:

Superior – posterior belly of the digastric muscle.

Lateral – medial border of the sternocleidomastoid muscle.

Inferior – superior belly of the omohyoid muscle.

The main contents of the carotid triangle are the common carotid artery (which bifurcates within the carotid triangle into the external and internal carotid arteries), the internal jugular vein, and the hypoglossal and vagus nerves.

Question 9

Discuss submental triangle

Answer 9

The submental triangle in the neck is situated underneath the chin. It contains the submental lymph nodes, which filter lymph draining from the floor of the mouth and parts of the tongue. Also anterior jugular vein

It is bounded:

Inferiorly – hyoid bone.

Medially – midline of the neck.

Laterally – anterior belly of the digastric

The floor of the submental triangle is formed by the mylohyoid muscle, which runs from the mandible to the hyoid bone.

Question 10

Discuss submandibular triangle

Answer 10

The submandibular triangle is located underneath the body of the mandible. It contains the submandibular gland (salivary), and lymph nodes. The facial artery and vein also pass through this area.

The boundaries of the submandibular triangle are:

Superiorly – body of the mandible.

Anteriorly – anterior belly of the digastric muscle.

Posteriorly – posterior belly of the digastric muscle.

Question 11

Discuss muscular triangle

Answer 11

The muscular triangle is situated more inferiorly than the subdivisions. It is a slightly ‘dubious’ triangle, in reality having four boundaries. The muscular triangle contains some muscles and organs – the infrahyoid muscles, the pharynx, and the thyroid, parathyroid glands.

The boundaries of the muscular triangle are:

Superiorly – hyoid bone.

Medially – imaginary midline of the neck.

Supero-laterally – superior belly of the omohyoid muscle.

Infero-laterally – inferior portion of the sternocleidomastoid muscle.

Question 12

What is the roof of these triangles made from?

Answer 12

deep (investing) fascia that surrounds the neck like a collar, enclos- ing the sternocleidomastoid anteriorly and the trapezius posteriorly.

Question 13

Discuss floor of posterior triangle

Answer 13

The floor of the posterior triangle is formed by the pre-vertebral fascia, which surrounds the deep pre-verte- bral muscles of the neck.The vertebral vessels pass through a triangular gap in the fascia to reach the foramen transversarium of the cervical spine.

Question 14

What can fascia be divided into?

Answer 14

Deep and superficial

Question 15

What does the superficial fascia blend with?

Answer 15

Platysma muscles

Question 16

What are the deep fascial layers? (superficial -> deep)

Answer 16

Investing layer

Pretracheal layer

Prevertebral layer

Carotid sheath

Question 17

Discuss investing layer

Answer 17

The investing layer is the most superficial of the deep cervical fascia.

It surrounds all the structures in the neck. Where it meets the trapezius and sternocleidomastoid muscles, it splits into two, completely surrounding them.

The investing fascia can be thought of as a tube; with superior, inferior, anterior and posterior attachments:

Superior – attaches to the external occipital protuberance and the superior nuchal line of the skull.

Anteriorly – attaches to the hyoid bone.

Inferiorly – attaches to the spine and acromion of the scapula, the clavicle, and the manubrium of the sternum.

Posterior – attaches along the nuchal ligament of the vertebral column

Question 18

Discuss pretracheal layer

Answer 18

The pretracheal layer of fascia is situated in the anterior neck. It spans between the hyoid bone superiorly and the thorax inferiorly (where it fuses with the pericardium).

The trachea, oesophagus, thyroid gland and infrahyoid muscles (sternothyroid, sternohyoid, omohyoid) are enclosed by the pretracheal fascia.

Anatomically, it can be divided into two parts:

Muscular part – encloses the infrahyoid muscles.

Visceral part – encloses the thyroid gland, trachea and oesophagus.

Question 19

Discuss prevertebral layer

Answer 19

The prevertebral fascia surrounds the vertebral column and its associated muscles; scalene muscles, prevertebral muscles, and the deep muscles of the back.

It has attachments along the antero-posterior and supero-inferior axes:

Superior attachment – base of the skull.

Anterior attachment – transverse processes and vertebral bodies of the vertebral column.

Posterior attachment – along the nuchal ligament of the vertebral column

Inferior attachment – fusion with the endothoracic fascia of the ribcage.

The anterolateral portion of prevertebral fascia forms the floor of the posterior triangle of the neck. It also surrounds the brachial plexus as it leaves the neck and subclavian artery as it passes through the lower neck region – in doing so, it forms the axillary sheath.

Question 21

Discuss carotid sheath

Answer 21

The carotid sheaths are paired structures on either side of the neck, which enclose an important neurovascular bundle of the neck.

The contents of the carotid sheath are:

• Common carotid artery
• Internal jugular vein.
• Vagus nerve.
• Accompanying cervical lymph nodes.

The fascia of the carotid sheath is formed by contributions from the pretracheal, prevertebral, and investing fascia layers. The carotid artery bifurcates within the sheath into the external and internal carotid arteries.

The carotid fascia is organised into a column, which runs between the base of the skull to the thoracic mediastinum. This is of clinical importance as a pathway for the spread of infection.

Question 22

Discuss sternocleidomastoid

Answer 22

asses from the manubrium and clavicle to insert into the mastoid process of the temporal bone. When contracting unilaterally, tilts the head to the same side and rotates face, When contracting bilaterally, flexes cervical vertebrae so chin approaches manubrium. Sternocleidomastoid is

innervated by the spinal accessory nerve (CN XI).

Question 23

Discuss trapezius

Answer 23

passes from the external occipital protuberance and spinous processes of C7-T12, to insert

into the clavicle, acromion and spine of the scapula.When contracted, elevates, retracts and rotates scapu-

lae.Trapezius is innervated by the spinal accessory nerve (CN XI).

Question 24

Discuss scalene muscles

Answer 24

a group of three muscles within the lateral neck, innervated by C4-C7 spinal nerves, which

function to elevate the thoracic cage and bend the neck ipsilaterally.

Question 25

Discuss strap muscles

Answer 25

also known as the infrahyoid muscles.A group of four muscles in the anterior part of the

neck that function to depress the hyoid bone and larynx during swallowing and speech.

Question 26

Vagus nerve

Answer 26

Question 27

Discuss spinal accessory nerve

Answer 27

Question 28

Discuss phrenic nerve

Answer 28

Question 29

Discuss cervical plexus

Answer 29

Question 30

Discuss sympathetic chain

Answer 30