Head and Neck 1: Front of Neck SDL Flashcards
Where is the hyoid bone?
situated in the anterior midline of the neck between the chin and the thyroid cartilage
Where is the thyroid cartilage?
Below hyoid bone and above cricoid cartilage
Position of cricoid cartilage
Where is the cricothyroid membrane? Clinical relevance?
- Between thryoid and cricoid cartilage
- This ligament is cut during emergency cricothyrotomy. This kind of surgical intervention is necessary if the airway is blocked above the level of vocal folds.
What are the 3 unpaired cartilages of the larynx?
- Thyroid
- Cricoid
- Epiglottis
Location of suprasternal notch? Vertebral level?
- Seen as a visible dip between the two clavicles.
- Generally, lies at the T2 vertebral level
Attachments of sternocleidomastoid muscle?
Is a two-headed neck muscle with attachments to the manubrium of sternum (sterno-), the clavicle (-cleido-), and the mastoid process of the temporal bone (-mastoid).
Vertebral level of hyoid bone?
C3 vertebral level
How to palpate thyroid cartilage?
Place your finger on the tip of your chin. Slide your finger down the midline and the first hard structure you hit is the laryngeal prominence (typically known as the Adam’s apple) of the thyroid cartilage. The hyoid is just above that
Vertebral level of thyroid cartilage?
Between C4-5 vertebral levels
Vertebral level of cricoid cartilage?
C6 vertebral level
How to palpate cricoid cartilage?
Lies below the thyroid cartilage but is not easy to palpate
Location of thyroid gland? What vertebrae does it span?
The thyroid gland is located in the anterior neck and spans the C5-T1 vertebrae.
Structure of thyroid gland?
- Right lobe
- Left lobe
- Isthmus
Where can the lobes of the thyroid gland be palpated?
- Inferior to the position of the oblique line of the thyroid cartilage.
- Find the laryngeal prominence and arch of the cricoid cartilage, then feel posterolateral to the larynx. The thyroid gland also rises upon swallowing.
Where is the isthmus of the thyroid gland located?
- In the midline, anterior to the upper end of the trachea.
- Cannot be palpated easily.
Where can the trachea be palpated?
Can be felt at the anterior neck below the larynx.
Vertebral level of trachea?
Spans vertebral levels C6-T4 (T4 is the level of the terminal bifurcation of the trachea)
Level of bifurcation of trachea?
T4
Where can the carotid pulse be palpated? What should be noted?
- Palpating lateral to the upper border of the thyroid cartilage and just medial to the anterior border of SCM
- Do not palpate both sides at once and do not rub the vessel
The neck can be be divided into anterior and posterior triangles on each side. What are the anterior and posterior triangles divided by?
The sternocleidomastoid muscle
What forms the:
- Base?
- Posterior boundary?
- Anterior boundary?
of the posterior triangle of the neck?
- Base: middle 1/3 of clavicle
- Posterior boundary: anterior border of trapezius
- Anterior boundary: posterior border of sternocleidomastoid
Between the sternocleidomastoid and trapezius muscles the important contents of the posterior triangle can be identified. What are these?
- trunks of the brachial plexus
- the spinal accessory nerve
- the inferior belly of omohyoid muscle
- the external jugular vein.
Stab wounds in the posterior triangle may damage the upper trunk of the brachial plexus and/or the apex of the lung - why?
- Apex of lung extends above clavicle
- Upper trunk of brachial plexus located in posterior triangle of neck
The accessory nerve (cranial nerve XI) also descends posteroinferiorly through the posterior triangle.
Which muscles are supplied by this nerve?
- Trapezius
- Sternocleidomastoid
Where is the external jugular vein (EJV) formed? Where does it travel?
Forms near the angle of the mandible and descends through the subcutaneous tissue of the neck coursing medially to laterally across the surface of the sternocleidomastoid muscle towards the middle of the clavicle.
What does the external jugular vein drain into?
The subclavian vein
Surface markings of external jugular vein (LARGE arrows)
can be found by following an imaginary line from the earlobe, across angle of mandible to the middle of the clavicle, passing superficial to SCM.
What forms the:
- superior boundary?
- lateral boundary?
- medial boundary?
of the anterior triangle of the neck?
- superior: inferior border of mandible
- medial: sagittal line down midline of neck
- lateral: anterior border of sternocleidomastoid
What are the contents of the anterior triangle of the neck?
- lobes of the thyroid gland
- suprahyoid muscles and infrahyoid muscles (except the inferior belly of omohyoid which is found in the posterior triangle)
- the common carotid artery and its division into internal and external carotid arteries
- the internal jugular veins
- numerous cranial and peripheral nerves
Where are the infrahyoid muscles (‘strap’ muscles)?
This group of muscles lie distal to the hyoid bone
Function of infrahyoid muscles?
depressing the hyoid bone during swallowing
How many infrahyoid muscles are there? What are they?
4:
- Omohyoid
- Sternohyoid
- Sternothyroid
- Thyrohyoid
What 2 groups can the infrahyoid muscles be divided into? Which muscles are in which group?
Superficial plane – omohyoid and sternohyoid muscles.
Deep plane – sternothyroid and thyrohyoid muscles.
Attachments of omohyoid?
The omohyoid is comprised of two muscle bellies, which are connected by a muscular tendon.
- The inferior belly arises from the scapula. It runs superomedially underneath the sternocleidomastoid muscle.
- It is attached to the superior belly by an intermediate tendon, which is anchored to the clavicle
- From here, the superior belly ascends to attach to the hyoid bone.
Attachments of sternohyoid?
Originates: from the sternum and sternoclavicular joint.
Inserts: It ascends to insert onto the hyoid bone.
Attachments of sternothyroid?
Origin: the manubrium of the sternum
Inserts: the thyroid cartilage.
Attachments of thyrohyoid?
Origin: the thyroid cartilage of the larynx
Inserts: the hyoid bone.
What are most of the infrahyoid muscles innervated by?
Anterior rami of C1-C3, carried by a branch of the ansa cervicalis.
What are the ansa cervicalis?
a loop of nerves which are formed for the first three cervical nerves (C1–C3)
What is the only exception to the innervation of the infrahyoid muscles?
The thyrohyoid muscle
What is the thyrohyoid muscle innervated by?
Anterior ramus of C1, carried within the hypoglossal nerve.
From which nerve(s) do the roots of ansa cervicalis take origin?
first three cervical nerves (C1–C3)
Where are the suprahyoid muscles located?
Above the hyoid bone
What do the suprahyoid muscles form?
The floor of the mouth
How many suprahyoid muscles are there? What are they?
4:
- Stylohyoid
- Digastric
- Mylohyoid
- Geniohyoid
Function of the suprahyoid muscles?
have an important function in moving the hyoid bone during swallowing –> elevate the hyoid
What are the attachments of digastric?
The digastric is comprised of two muscular bellies, which are connected by a tendon.
Origin:
- The anterior belly arises from the digastric fossa of the mandible.
- The posterior belly arises from the mastoid process of the temporal bone.
Inserts:
- The two bellies are connected by an intermediate tendon, which is attached to the hyoid bone
What is the function of the digastric muscle?
Depresses the mandible and elevates the hyoid bone
In the gap between the left and right infrahyoid muscles, what components of the larynx can be identified?
- Thyroid cartilage
- Cricoid cartilage
- Laryngeal prominence
- Cricothyroid membrane
- Trachea
- Isthmus of the thyroid gland
What is a cricothyroidotomy (sometimes called a laryngotomy)?
An incision made through the skin and cricothyroid membrane to establish a patent airway (and then inserting a tube)
What is tracheostomy?
Creating an opening in the neck in order to place a tube into a person’s windpipe. The tube is inserted through a cut in the neck below the vocal cords. This allows air to enter the lungs.
When is a tracheostomy done?
Under 3 conditions:
- to bypass an obstructed upper airway
- to clean and remove secretions from the airway
- to more easily, and usually more safely, deliver oxygen to the lungs.
What is the carotid sheath?
A thick layer of fascia in the neck
What three important structures are surrounded by the carotid sheath?
- Carotid artery
- Jugular vein
- Vagus nerve
What does the internal jugular vein drain?
Drains blood from the brain, skull and superficial parts of the face and neck.
Location of internal jugular vein diagram
the Internal jugular vein (IJV) transverses the neck lateral to the common carotid artery to join the subclavian veins.
What does the IJV drain into?
Subclavian vein
What can cause conspicuous swelling in the jugular veins?
is impeded blood flow to the heart, which may indicate possible clinical factors such as chronic lung disease, mediastinal tumours, or infections.
Veins in neck diagram
When palpating the carotid pulse, why should you not palpate both sides at once or rub the vessel?
Can lead to fainting or can lead to stroke: by blocking blood flow to vein or the carotid arteries also have nerve endings that respond to changes in blood pressure
At which vertebral level does the carotid bifurcation lie? What laryngeal landmark lies at the level of the carotid bifurcation?
CIII-CIV - At the level of the superior margin of the thyroid cartilage. This bifurcation occurs in the carotid triangle.
Does the internal carotid artey have any branches in the neck? Does the external carotid artery?
Internal - no
External - yes
Which cranial nerve is the vagus nerve?
Cranial nerve X
Where does the vagus nerve originate?
From the medulla of the brainstem
Where does the vagus nerve exist the cranium?
Via the jugular foramen
Within the cranium, which branch of the vagus nerve arises? What does this supply?
The auricular branch arises. This supplies sensation to the posterior part of the external auditory canal and external ear.
In the neck, what does the vagus nerve travel in?
the vagus nerve passes into the carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery.
What is important to note about the left and right vagus nerves at the base of the neck?
They have differing pathways
At the base of the neck, where does the right vagus nerve pass?
The right vagus nerve passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax.
At the base of the neck, where does the left vagus nerve pass?
The left vagus nerve passes inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.
Which branches of the vagus nerve arise in the neck?
- Pharyngeal branches
- Superior laryngeal nerve
- Recurrent laryngeal nerve (right side only)
What do the pharyngeal branches of the vagus nerve innervate?
Motor - Provides motor innervation to the majority of the muscles of the pharynx and soft palate.
What does the superior laryngeal branch of the vagus nerve innervate?
Splits into internal and external branches:
- External –> innervates the cricothyroid muscle of the larynx.
- Internal –> provides sensory innervation to the laryngopharynx and superior part of the larynx.
What does the right recurrent laryngeal nerve (branch of vagus) innervate?
Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx.
Where does the left recurrent laryngeal nerve arise?
Branch of vagus nerve that arises in the thorax (from the anterior vagal trunk)
In the thorax, what does the right vagus nerve form? The left?
The right vagus nerve forms the posterior vagal trunk, and the left forms the anterior vagal trunk.
What does the left recurrent laryngeal nerve innervate?
it hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx.
Where does the production of sound begin? What is this process called?
In the larynx - phonation
What is the larynx composed by?
composed by cartilages which are connected by membranes, ligaments and associated muscles
What does the inside of the laryngeal cavity contain?
The epiglottis and the vocal folds (‘vocal folds’)
Name the other function of the larynx (i.e. in addition to its role in phonation)?
helps to maintain a patent airway by protecting the respiratory system from the entrance of food and foreign substances
How is sound produced?
By vibration of the vocal cords in the larynx
At rest, how are the vocal folds? How does this change during phonation?
- They are separated at rest
- During phonation, they are adducted –> obstructing the flow of air
- Pressure builds up, the folds are forced apart, air escapes
- The folds then return to their adducted position
Rapid repetition of these movements results in vibration of the folds, giving rise to sound waves
How is pitch varied? How are these features adjusted?
- By altering the length and tension of the vocal folds (which alters the frequency of their vibration).
- These features are adjusted by the action of the intrinsic muscles of the larynx.
What can the muscles of the larynx be divided into?
Internal and external intrinsic muscles
How do the intrinsic muscles of the larynx affect the vocal folds?
The intrinsic muscles of the larynx alter both the length and the tension placed upon the vocal cords as well as the rima glottidis
Which cranial nerve supplies the intrinstic muscles of the larynx?
All the intrinsic muscles of the larynx (except the cricothyroid) are innervated by the inferior laryngeal nerve
What is the inferior laryngeal nerve a branch of?
Is the terminal branch of the recurrent laryngeal nerve (itself a branch of the vagus nerve)
How does the innervation of the cricothyroid muscle differ from that of the other intrinsic muscles?
Innervated by the external laryngeal nerve
What is the external laryngeal nerve a branch of?
Branch of the superior laryngeal nerve (which is a branch of the vagus nerve)
What is the loudness of sound produced by the larynx related to?
The pressure of the expired air
What does the quality or timbre of the voice depend on?
resonating chambers above the vocal cords
Though which spaces do sound waves pass to reach the outside world?
?
Sound is broken up into recognisable vowels and consonants by movements of the lips and the tongue. What is this process called?
Articulation
Which cranial nerves supply the muscles responsible for movements of the lips?
The facial nerve - CN VII
Which cranial nerves supply the muscles responsible for movements of the tongue?
hypoglossal nerve (CN XII).
The vagus nerve supplies both motor and sensory fibres to the larynx. What 2 branches does the vagus nerve give off to the larynx?
- Superior laryngeal nerve –> running toward the upper boundary of the larynx
- Recurrent laryngeal nerve –> running toward the lower boundary of the larynx
Where does the left recurrent laryngeal nerve arise?
In the thorax
Which artery is the recurrent laryngeal nerve closely related to? When should extra care be taken?
- The inferior thyroid artery (a branch of the thyrocervical trunk, which arises from the first part of the subclavian artery)
- Both structures need to be carefully considered when performing surgical procedures to the thyroid gland
Why does hoarseness sometimes occur following thyroid surgery?
Damage to a recurrent laryngeal nerve can cause you to lose your voice or become hoarse. Temporary hoarseness can occur when one or more of the nerves are irritated during the operation or because of inflammation that occurs after the surgery.
What artery does the superior laryngeal nerve lie close to?
The superior thyroid artery (a branch of the external carotid artery)
Where does the superior laryngeal nerve divide? What does it divide into?
it divides into its external laryngeal and internal laryngeal branches just above the hyoid bone
Diagram of nerves to the larynx
What does the internal laryngeal branch of the superior laryngeal nerve supply?
Above the vocal folds the sensory innervation of the larynx is via the internal laryngeal nerve.
What other cranial nerves pass out of the skull alongside the vagus nerve?
Glossopharyngeal nerve (CNIX), vagus nerve (CNX), descending portion of the spinal accessory nerve (CNXI)
Difference between pharynx and larynx?
Pharynx is a part of an alimentary canal, which extends from the nasal cavity and mouth to the larynx and the esophagus whereas larynx is the upper portion of the trachea. Both air and food pass through the pharynx.
What are the 3 subdivisions of the pharynx?
- Nasopharynx
- Oropharynx
- Laryngopharynx
What separates the nasopharynx from the oropharynx?
the roof of the soft palate
What separates the oropharynx from the laryngopharynx?
The superior border of the epiglottis
The first stage of swallowing is voluntary and involves passage of the bolus of food from the oral cavity into the oral part of the pharynx.
How is this achieved?
The tongue squeezes the bolus backward along the palate, through the fauces, and into the pharynx
What muscles are involved in voluntary swallowing? What is their nerve supply?
- Infrahyoid muscles
- Omohyoid (ansa cervicalis)
- Sternohyoid (ansa cervicalis)
- Sternothyroid (ansa cervicalis)
- Thyrohyoid (CN XII)
- Longitudinal pharyngeal muscles (mostly by vagus nerve)
The remaining stages of swallowing are involuntary. What are these controlled by?
a series of reflexes involving cranial nerves IX and X
Which cranial nerve supplies sensory fibres to the posterior third of the tongue and the oropharynx?
Glossopharyngeal nerve (CN IX)
When the bolus of food comes into contact with these regions, a number of reflex movements follow:
- The soft palate is tensed and elevated. Why?
This prevents the food bolus from entering the nasopharynx
When the bolus of food comes into contact with these regions, a number of reflex movements follow:
How is the laryngopharynx opened? How does this shut off the laryngeal inlet?
The hyoid bone is pulled forwards and upwards, and with it the larynx and the root of the tongue; these movements open the laryngopharynx and tilt the epiglottis downwards over the laryngeal inlet.
Which other laryngeal structures help to close off the laryngeal inlet during swallowing?
- When you swallow, the epiglottis moves to block the entrance of food particles into your larynx and lungs - tthe muscles of the larynx pull upward to assist with this movement.
- The muscles of the larynx also so tightly close during swallowing. That prevents food from entering your lungs.
During swallowing (involuntary), how does the circular muscles of the pharynx move the bolus?
Contraction of the circular (constrictor) muscles of the pharynx moves the bolus of food down over the closed inlet of the larynx and on into the oesophagus.
Summary of reflex movements involved in swallowing:
- The soft palate is tensed and elevated.
- The hyoid bone is pulled forwards and upwards, and with it the larynx and the root of the tongue; these movements open the laryngeal pharynx and tilt the epiglottis downwards over the laryngeal inlet.
- Contraction of the circular (constrictor) muscles of the pharynx moves the bolus of food down over the closed inlet of the larynx and on into the oesophagus.
Where do virtually all the muscles of the pharynx and soft palate receive their nerve supply from?
Via the pharyngeal plexus (a complex network of nerves in the pharyngeal wall)
N.B. Sensory fibres from the pharyngeal wall also pass via this plexus
What is the pharyngeal plexus formed from?
- the pharyngeal branch of the glossopharyngeal nerve (CN IX)
- the pharyngeal branch of the vagus nerve (CN X) – which carries some fibres that have originated in the cranial part of the accessory nerve
- autonomic fibres
Describe vocal folds when we swallow
Closed
Describe vocal cords during respiration?
Vocal folds are open when we breathe quietly
Describe vocal cords during phonation
Air causes vocal folds to vibrate between open and closed positions when we talk
