Session 1.1b - Pre-Reading (Organisation of the Neck) Flashcards
Organisation of the Head & Neck VIDEO, pre-reading for Lecture 1 https://www.youtube.com/watch?v=kqwupuoCOzs
What does the neck act as a conduit or passageway for?
Structures running between the head and thorax
What important structures does the neck contain from the respiratory and GI system?
Larynx
Trachea
Pharynx
Oesophagus
What is the best way to visualise the neck?
Via cross-section
- this helps us to appreciate the anatomical arrangement and relationships of the different structures
How are neck structures arranged?
Into ‘compartments’
Other than the neck, what other structures are organised into compartments?
Upper and lower limb
How are the structures through the neck compartmentalised?
Compartments created by fibrous sheets of tissue which are concentrically arranged, called fascia.
Broadly speaking, where do the fascia run?
For the most part, they run the length of the neck, from the base of the skull onto the chest wall or into the thorax.
What is the fascia in the neck called?
Cervical fascia
Cervical = neck
There are a number of cervical fascial layers. What are the two broad categories?
Superficial or deep.
How many layers of superficial cervical fascial layers are there?
One
Where does the cervical fascial layer lie?
Immediately below the skin
What does the superficial cervical fascial layer consist of?
- Very loose connective tissue
- Fat
- Superficial LNs
- Superficial blood vessels, e.g. external jugular vein
- Cutaneous nerves supplying the skin of the neck
- Platysma muscle
What tissue type is the superficial cervical fascial layer?
Loose connective tissue
Give an example of a blood vessel that runs through the superficial cervical fascial layer
External jugular vein
What do the nerves of the superficial cervical fascial layer supply?
They are cutaneous, thus supply the skin of the neck.
What muscle is found in the superficial cervical fascial layer?
Platysma
Describe the platysma muscle’s location, and its origin and insertion.
Arises from the lower part of the face at the inferior border of the mandible
Descends down the neck
Blending onto the clavicle, sternum and anterior chest wall.
What is the platysma’s origin?
Clavicle, sternum and anterior chest wall area
What is the platysma’s insertion?
Inferior border of the mandible (lower part of the face)
How many deep cervical fascial layers are there?
4 (including the carotid sheath)
How are the deep cervical fascial layers named?
Broadly - ‘deep’ because it is deeper than the superficial layer
The individual layers are named depending on the structures that they enclose
What type of tissue is deep cervical fascia?
Dense connective tissue
Which of these, if any, has denser connective tissue, and is therefore tougher?
- Superficial cervical fascia
- Deep cervical fascia
The deep cervical fascia is denser and tougher (dense CT)
The superficial cervical fascia consists of loose CT.
Image 1:
What layers have we removed to create this image?
The skin and superficial cervical fascial layer
Image 2:
What level are we looking at here?
Directly looking at the first of the deep cervical fascia layers i.e. investing layer
Image 3:
At approximately what layer is this cross-section taken?
C7
??? Check
Image 4:
If this image is depicting the first layer of deep cervical fascia, which layer is this red circle depicting and what do the labels mean?
The red circle must be showing the investing layer.
ANT represents anterior (front of the neck), and POST represents posterior (back of the neck), whilst the L and R indicate left and right, respectively.
Image 4:
From what position are we visualising this cross-section drawing?
We are looking from the feet up towards the head i.e. in the same way we would view CT images.
What is the first layer of deep cervical fascia?
The investing layer
What structure do we find most anteriorly running through the neck (particularly at the level of this cross-section)?
The thyroid gland
What is the structure of the thyroid gland when we’re looking at it directly, front on?
It is H-shaped, with a central isthmus and two lateral lobes either side
Image 5:
Name this structure
The thyroid gland
Image 6:
Name the structure and this part of the structure
The central isthmus of the thyroid gland
Image 7:
Name the structure and this part of the structure
The lateral lobe of the thyroid gland
Image 5:
Why does the thyroid gland in this image not look like the classical thyroid gland normally depicted in images (‘H-shaped’)?
The level at which the cross-section was taken (approx. C7) cuts right through the thyroid gland at the level of the isthmus. Therefore, the central isthmus and the two lateral lobes are pictured but the thyroid gland is essentially cut in half transversely. (See Image 8)
What structure is immediately behind the thyroid gland?
The trachea
Image 9:
What structure lies immediately behind the thyroid gland?
The trachea
The trachea lies immediately behind which structure?
The thyroid gland
What is the trachea a continuation of?
The larynx
The larynx continues on to form which structure?
The trachea
About which level does the larynx ends and the trachea begins?
C6
What is found immediately behind the trachea?
The oesophagus
Which structure lies posterior to the thyroid gland and anterior to the oesophagus?
The trachea
The oesophagus is found posterior to which structure(s)?
The trachea (and the thyroid gland).
The oesophagus is a continuation of which structure?
The pharynx
The pharynx continues on to form which structure?
The oesophagus
At which level does the pharynx end and the oesophagus begins?
C6
At the back of the neck you find a very ____, ________ area.
Bony, muscular
What is found in the bony muscular area at the back of the neck?
Cervical vertebrae surrounded by a number of muscles
Which vertebrae are found in the neck?
Cervical vertebrae
Many of the muscles associated with the cervical vertebra run where?
Many run the length of the neck and the spine
What is the collective name for muscles that run the length of the neck and spine (i.e. associated with the cervical vertebra)?
Pre- and paravertebral muscles.
Image 10:
Label this structure.
The oesophagus
Image 11:
Label the cervical vertebra in this image
Spinous object posteriorly in the neck.
Image 11:
Label the posterior structures in this image.
Cervical vertebra, surrounded by pre- and paravertebral muscles (note: these muscles are drawn roughly, and do not necessarily represent the exact number of these muscles - the purpose of the image is merely to indicate that there are quite a few muscles surrounding the vertebra.
What is the function of the pre- and paravertebral muscles?
These are the muscles that surround the cervical vertebra, which act to anchor the head to the neck and the rest of the body.
What lies between the oesophagus and the prevertebral muscles/cervical vertebrae?
A number of neurovascular structures that are running up and down the neck between the thorax and the head. These are within their own fascial compartment, known as the carotid sheath.
A number of neurovascular structures are found in the carotid sheath of the neck. Where do they run?
Up and down the neck between the thorax and the head.
Many neurovascular structures are found in the neck, posterior to the oesophagus and anterior to the prevertebral muscles. What fascial compartment are they found in?
These are within their own fascial compartment, known as the carotid sheath.
The carotid sheath is a part of which cervical fascial layer?
It is its own separate layer in the realms of deep cervical fascia.
Image 12:
What are the green circles?
The carotid sheath
Image 12:
Label the carotid sheath.
Green circles
What does the carotid sheath contain?
Neurovascular structures that are running up and down the neck.
At the level of this cross-section, what artery would you expect to find in the carotid sheath?
The level of the cross-section is about the level of C7 (due to the thyroid gland being split in two, and the central isthmus being visible).
This means you would expect to find the common carotid artery.
Which arteries does the common carotid artery (CCA) bifurcate into?
The internal carotid artery (ICA) and the external carotid artery (ECA).
The internal carotid artery is a branch of which artery?
The common carotid artery
At approximately which level does the common carotid artery bifurcate into its two terminal branches, and which arteries does it bifurcate into?
The level of C4 vertebra
The internal and external carotid arteries.
If the cross-section was taken higher up the neck, e.g. at C3/C4 level, which artery would you find in the carotid sheath?
The common carotid artery bifurcates into the internal and external carotid arteries.
Above the level of ~C4, the internal carotid artery is found in the carotid sheath.
Below ~C4, the common carotid artery is found in the carotid sheath.
What is the carotid sheath?
A neurovascular bundle
What is the neurovascular bundle found in the neck called?
The carotid sheath
Which vein is found in the carotid sheath?
The internal jugular vein (IJV)
Where is the IJV found in the neck?
The internal jugular vein is found in the carotid sheath.
Where does the IJV lie in relation to the CCA?
The IJV lies more laterally in the neck/carotid sheath compared to the CCA.
Which structure do we find posterior to the CCA and IJV in the carotid sheath?
The Vagus Nerve
Where does the VN arise from?
The brainstem
What is the route of the VN?
It arises from the brainstem, enters from the base of the skull and runs down the length of the neck into the thorax.
Describe the third major structure in the carotid sheath, that is not the CCA or IJV.
- What it is
- Its location
- Its origin and route
The vagus nerve lies posteriorly to the CCA or IJV in the carotid sheath. It will arise from the brainstem, enter through the base of the skull and run down the length of the neck into the thorax.
Image 13:
if the red dot indicates an artery, what artery is this?
The major artery in the carotid sheath i.e. the common carotid artery (especially at the level of this cross-section which is ~C7)
Image 14:
Label the artery and vein in the carotid sheath. Explain why you have labelled them as such.
Artery is red dot (CCA)
Vein is blue oval (IJV)
The IJV lies more laterally the CCA in the carotid sheath. The green circles represent the carotid sheath.
Image 15:
Label the structures in the carotid sheath.
- Green circle identified as carotid sheath
- Red dot is CCA (medial)
- Blue oval is IJV (lateral)
- Yellow dot is vagus nerve (posterior)
Which structures do we find in the carotid sheath?
CCA*
IJV
VN
- At the level of ~C7 we would find the CCA. Higher up in the neck (~C4) when the CCA bifurcates, the ECA would leave the carotid sheath, whereas the ICA would continue right up the way into the base of the skull through which it enters intercranially.
If we took a cross-section of the neck at a level where the common carotid artery has bifurcated, which artery would we see in the carotid sheath and why wouldn’t we see the other one?
We would say the ICA, and we wouldn’t see the ECA because this will have left the carotid sheath.
What is the route of the ICA from the carotid sheath of the neck to the cranium?
The ICA would continue from the carotid sheath of the neck up to the base of the skull, through which it enters intercranially.
What structures are found in both the back and front of the neck?
The muscles and the bones [of the vertebral column] are found at the back/posteriorly.
Visceral structures are found at the front/anteriorly, such as the thyroid gland, trachea and oesophagus.
What are the visceral structures of the neck at the C7 level and where are they found?
The thyroid gland, trachea and oesophagus, found at the front/anterior end of the neck.
The thyroid gland, trachea and oesophagus are collectively known as what structures?
Visceral structures
How are the structures at the back (bones and muscles) separated from the visceral structures at the front (thyroid gland, trachea, oesophagus).
They are found within their own fascial compartments.
What fascial layer encloses the structures at the back of the neck?
The pre-vertebral cervical fascia
Where does the pre-vertebral fascia originate, extend to and run its course?
The pre-vertebral fascial layer runs right the way from the base of the skull, right the way down the neck (as a column of fascia), completely enclosing vertebra and muscles of the neck, extending down into the thorax.
What does the column of pre-vertebral cervical fascia enclose?
The vertebra and muscles of the neck (hence the name).
Whereabouts does the pre-vertebral fascia end?
It extends down into the thorax, usually blending with the vertebrae at about T3
Image 16:
What is this layer of fascia known as?
The pre-vertebral fascia
What muscles do we find in front of the visceral structures of the neck?
The infrahyoid muscles (strap-like muscles)
What sort of muscles are the infrahyoid muscles?
Strap muscles (and are therefore alternatively known as such).
How many infrahyoid muscles are there?
4
Where do the infrahyoid muscles arise form?
The hyoid bone
What is the position of the infrahyoid muscles?
They arise from the hyoid bone and run down the neck, lying immediately in front of the thyroid gland.
What are strap muscles also known as?
Infrahyoid muscles.
Image 17:
What are these structures in front of the thyroid gland?
The infrahyoid/strap muscles.
What does the pre-tracheal fascia enclose?
The infrahyoid muscles and the visceral structures (trachea, thyroid and oesophagus).
What are the two layers of the pre-tracheal fascia?
The muscular layer and the visceral layer
What do the muscular and visceral layer of the pre-tracheal fascia contain?
Muscular - infrahyoid muscles
Visceral - thyroid, trachea and oesophagus
Which deep cervical fascia layer has sub-layers (i.e. a compartment with sub-compartments)?
The pre-tracheal layer is divided into a muscular and visceral layer (but still collectively known as the pre-tracheal layer)
Image 18:
What is this layer known as?
The pre-tracheal layer
Note the muscular and visceral sub-compartments within the pre-tracheal compartment
Which deep cervical fascial layer is considered to take its origins from the other 3 cervical fascial layers?
The carotid sheath - perhaps not as easily seen as in the diagram.
In some texts there are considered to be 3 deep cervical fascial layers and 4 deep cervical fascial layers. Explain the difference.
There are 3 deep cervical fascial layers known as the investing layer, pre-vertebral layer, and pre-tracheal layer. A 4th layer is sometimes described, known as the carotid sheath. However, this is thought to take its origins from the other 3 deep cervical fascial layers and is therefore perhaps not considered a deep cervical fascial layer on its own.
What is the posterior wall of the pre-tracheal fascia known as?
The buccopharyngeal fascia
Where is the buccopharyngeal fascia?
Posterior wall of pre-tracheal fascia (still considered part of the pre-tracheal fascia)
Which structures on this diagram (Image 18) does the buccopharyngeal fascia run behind?
The pharynx and the oesophagus
What is the course of the buccopharyngeal fascia?
It extends from the base of the skull, down behind pharynx (higher up in the neck) and the oesophagus (lower down in the neck) into the thorax, blending with the pericardial sac, as far as the diaphragm.
Image 18:
Where is the buccopharyngeal fascia?
Posterior wall of pretracheal fascia.
Image 18:
Locate the anterior pretracheal fascia.
Anterior wall (in front of the infrahyoid muscles) of pretracheal fascia.
Describe some similarities and differences in the posterior and anterior wall of the pretracheal fascia.
Similarities:
- Both blend with the pericardial sac inferiorly
Differences:
- The anterior wall of pretracheal fascia originates from the hyoid bone and is therefore not seen in higher parts of the neck
- The posterior wall of pretracheal fascia runs behind the pharynx and oesophagus, and is able to run up all the way to the base of the skull.
- The posterior wall of pretracheal fascia is also known as buccopharyngeal fascia.
What structures do we find running through the 4 deep cervical fascial layers?
Investing layer - SCM, trapezius
Carotid sheath - CCA, IJV, VN
Pre-vertebral layer - Cervical vertebra & associated muscles
Pre-tracheal layer -
- Muscular layer: infrahyoid muscles
- Visceral layer: thyroid gland, trachea, oesophagus
Image 19:
Which muscle are the red lines showing?
Sternocleidomastoid
What sort of muscle is SCM?
A long, strap-like muscle
What is the origin and insertion of SCM?
Running from the mastoid process down to the sternum and clavicle
Image 20:
What muscle is shown here and from what view?
SCM, from a lateral view
Image 2:
Draw SCM on this image.
Image 20 as answer
Note the two heads, one inserts on the clavicle, the other on the sternum.
What is the broad, triangular muscle of the neck found posteriorly?
Trapezius
Where is trapezius found in the neck and describe its shape.
Posteriorly, it is a broad triangular muscle
Where is the trapezius muscles’ origin and insertion?
It arises from the base of the skull (similar to SCM) and inserts onto the spine of the scapula and the clavicle.
Image 21:
What muscle is outlined in red?
Trapezius
posterior view, broad triangular muscle
Image 22:
What is the outer black layer?
The skin
Image 22:
Label the skin on the cross-section
Outer black layer
Which fascial layer do SCM and trapezius muscles lie?
Investing layer of deep cervical fascia
SCM and trapezius lie immediately below the skin.
True or False?
False, they don’t lie immediately below the skin; they are surrounded by the investing layer of deep cervical fascia.
SCM and trapezius lie within the superficial cervical fascia.
True of False?
False, they lie within the investing layer of deep cervical fascia (the most superficial of deep cervical fascia).
How are SCM and trapezius surrounded by the investing layer?
This splits to completely encase these muscles, so they have their own compartments essentially (Image 23).
Image 23:
Label the SCM and trapezius muscles and which layer they’re in
SCM - anterior muscles (red)
Trapezius - posterior muscle (red)
Within their own compartments in the investing layer (burgundy)
What is the most superficial layer of fascia in the neck?
Superficial cervical fascia
Where does the superficial cervical fascial layer lie?
Immediately below the skin
What do we find within the superficial cervical fascia?
- Superficial lymph nodes
- Veins e.g. external jugular vein
- Cutaneous nerves supplying the neck of the skin
- Platysma
Which fascial layer is the external jugular vein found?
Superficial cervical fascia
What is the sheet-like muscle that covers the front of the neck?
Platysma
Describe the platysma muscle.
It runs down the front of the neck like a sheet
Where is the platysma’s origin, location and insertion?
It arises from the lower part of the jaw (inferior border of the mandible) and extends right the way down the front of the anterolateral neck onto the clavicle and chest wall.
What is the platysma’s origin?
Inferior border of the mandible (lower part of the jaw)
Where does the platysma lie (location)?
It extends down the front of the anterolateral neck
Where does the platysma insert?
Onto the clavicle and chest wall
Describe the platysma muscle location i.e. superficial or deep
It is a very superficial muscle
Where does the platysma muscle lie (anatomically i.e. superficial or deep)?
Just beneath the skin
Which muscle is found in the superficial cervical fascia?
Platysma
Image 24:
Identify the platysma muscle
Burgundy shaded muscle (muscle covering the anterior found in sperficial cervical fascia)
Image 24:
What is different about the spaces found in this image and the spaces between fascial layers in real life?
In this cross-section, there is a lot of space within the structures here; but in life, this isn’t the case - the spaces would be much more squashed together.
What is a problem about having fascial compartmentalisation?
There are potential spaces between the structures
Why can we get potential spaces between the structures?
Due to fascial compartmentalisation
Where is the retropharyngeal space?
Between the buccopharyngeal fascia of the pretracheal fascia and the prevertebral fascial layer, bounded laterally by the carotid sheath.
What is the anterior wall of the retropharyngeal space?
Buccopharyngeal fascia of the pretracheal fascia (posterior wall)
What is the posterior wall of the retropharyngeal space?
Prevertebral fascial layer (anterior wall)
What are the lateral walls of the retropharyngeal space?
(Medial borders of) the carotid sheath
Why is the retropharyngeal space an important space?
If infections or an abscess develops here, there is a potential passageway from within the neck right down to the mediastinum in the thorax, due to the extent of which the fascial layers run the neck.
Where can infections or abscesses develop?
In the retropharyngeal space (or other deep neck spaces)
How can retropharyngeal space infections travel into the mediastinum in the thorax?
Due to the extent of which the fascial layers run the length of the neck.
Where can retropharyngeal space infections travel to?
The mediastinum in the thorax.
How common are retropharyngeal infections?
Fortunately very rare
What is a major concern in terms of sequelae for retropharyngeal space infections?
There is a big concern that they could spread into the mediastinum, causing mediastinitis
Why is mediastinitis such a concern for doctors?
It has a very high mortality associated with it
Name the 4 cervical fascial layers of the neck, and an important deep neck space.
- Superficial cervical fascial layer
- Investing layer
- Pretracheal layer
- Prevertebral layer
- Retropharyngeal space (between buccopharyngeal fascia and prevertebral fascia)
Give a clinical reason why it is important to know the fascial compartmentalisation of the neck.
Compartmentalisation causes spaces between the structures, where infections can occur. An infeciton in the retropharyngeal space, in particular, can spread from the neck down into the thorax and mediastinum, causing mediastinitis, which has a very high mortality associated with it.
