Neurovascular Structures in the Neck 2 Flashcards
What structures does the vagus follow the course of?
It follows the course of the internal and external carotid arteries and the internal jugular vein – therefore it contributes to a great neurovascular bundles with these vessels.
What is the great neurovascular bundle with the vagus nerve called and what is it surrounded by?
This is called the carotid sinus and it is loosely bound by connective tissue.
How does the vagus nerve enter the thorax?
It runs down the carotid sheath and eventually over the front of the subclavian artery to enter the thorax.
What does the vagus nerve give off after leaving the skull?
It gives off a pharyngeal branch.
What do the fibres of the pharyngeal branch of the vagus nerve form on the surface of the pharyngeal muscle?
They form a meshwork on the surface of the pharyngeal muscles and they carry motor fibres to the pharynx and the palate.
What is the uppermost branch of the vagus nerve to the larynx?
The superior laryngeal nerve.
What does the superior laryngeal nerve divide into?
Divides to give a sensory branch and a motor branch.
What is the sensory branch of the superior laryngeal nerve?
This is the internal laryngeal nerve.
How does the internal laryngeal nerve enter the larynx?
It enters the larynx by piercing a membrane.
What is the motor branch of the superior laryngeal nerve called?
It is called the external laryngeal nerve.
What is the external laryngeal nerve destined to supply?
It is destined to supply one important muscles on the surface of the larynx.
What artery does the superior laryngeal nerve follow to form a neurovascular bundle?
It follows the superior thyroid artery to form a neurovascular bundle.
What is the lower branch of the vagus nerve to the larynx on the right?
This is the right recurrent laryngeal nerve.
How does the right recurrent laryngeal nerve form a neurovascular bundle?
It hooks around the right subclavian artery and ascends with the inferior thyroid artery to form another important neurovascular bundle.
What does the right recurrent laryngeal nerve supply?
It enters the larynx to supply the remainder of the laryngeal muscles.
Where does the left recurrent laryngeal nerve arise?
It arises in the thorax.
What does the left recurrent laryngeal nerve do before it ascends into the neck?
It hooks around the arch of the aorta before ascending into the neck.
What is the relationship of the left recurrent laryngeal nerve with the inferior thyroid artery?
It ascends with the inferior thyroid artery to form another neurovascular bundle.
How does the 11th cranial nerve = the accessory nerve arise?
The cranial root - arise from the brain just below the vagus
The spinal root - arise from the upper part of the spinal cord
When do the 2 roots of the accessory nerve converge?
They join and converge on the vagus nerve just before the 10th and 11th cranial nerves leave the skull.
What happens to the accessory nerve after it leaves the jugular foramen?
They separate again.
What do the cranial fibres of the accessory nerve join after pass through the jugular foramen?
They join the vagus nerve.
What happens to the spinal fibres of the accessory nerve?
They travel on as a separate nerve.
What is the vagus nerve entering the neck a mixture of?
It is actually a mixture of vagoaccessory fibres.
More accurately, what is the accessory nerve in neck?
This is more accurately the spinal part of the accessory nerve.
How does the vagoaccessory mixture supply motor fibres to the muscles of the pharynx?
They supply the muscles of the pharynx through the pharyngeal branch of the vagus.
What is the pharyngeal plexus made of?
- motor pharyngeal complex of vagoaccessory mixture
- sensory fibres from the glossopharyngeal nerve
- a few sympathetic fibre
these form a meshwork of nerve fibres on the pharyngeal wall
What does the pharyngeal plexus supply?
It supplies motor and sensory nerve fibres to the pharynx.
Motor supply to the muscles of the soft palate except the tensor palati.
What do the laryngeal nerves contain a mixture of?
They contain a mixture of true vagal and cranial accessory fibres.
In terms of the vagal fibres, what do we seen in the thorax and the abdomen?
By the time the vagal trunks have reached the thorax, on their way to the abdomen, all the cranial accessory fibres have been used up and some vagal fibres are also used up while supplying the pharynx, larynx and soft palate.
Therefore in the abdomen we have true vagal fibres.
What is the hypoglossal nerve in the neck?
This is a nerve of transit in the necl mostly.
What does the hypoglossal nerve supply?
It supplies almost all of the tongue muscles therefore it aims for the lingual artery and travels with its as a neurovascular bundle.
Describe the course of the hypoglossal nerve.
- leaves the cranial cavity through the hypoglossal canal
- takes a wide embracing route around the internal and external carotids and also outside the loop of the lingual artery
What fibres hitch hike along the hypoglossal nerve?
A few fibres from the first cervical ramus run with the hypoglossal nerve close to the skull base. These hitch hike along with the hypoglossal nerve for a while.
How the fibres from the first cervical vertebrae leave the hypoglossal nerve?
They leave the hypoglossal nerve as a slender filament called the superior root of the ansa cervicalis.
What do the fibres of the 2nd and 3rd cervical ventral rami form?
They form the inferior root of the ansa cervicalis.
What do the superior and inferior root of the ansa cervicalis join to form?
They join to form a delicate U shaped loop on the common carotid artery and internal jugular vein.
What are the cervical nerve fibres of the superior and inferior ansa cervicalis destined to supply?
They are destined to supply some of the strap like muscles at the front of the neck.
Which muscles weave through the carotid tree from the bony styloid process on the base of the skull?
The 3 styloid muscles. These complete out picture of the deep structures at the side of the neck.
What is the styloglossus?
This is a deep muscle destined for the tongue.
What is the stylopharyngeus muscle?
This is the longitudinal muscle of the pharynx.
What is the path of the stylopharyngeus muscle?
- passes with the glossopharyngeal nerve
- first passes between internal and external carotid arteries
- passes over the upper border of the middle constrictor
Where is the stylohyoid muscle positioned?
It is more superficial and runs around the carotid tree (just like the hypoglossal nerve) and inserts into the hyoid bone.
What are the smaller branches of the external carotid artery?
- ascending pharyngeal artery
- occpital artery
- posterior auricular branch
Where does the ascending pharyngeal arise?
Arises opposite the superior thyroid artery.
Where does the ascending pharyngeal artery supply blood to?
It supplies blood to the pharyngeal wall.
Where does the occipital artery arise?
It arises opposite the facial artery and passes to the back of the neck deep to the sternocleidomastoid muscle.
What does the posterior auricular branch supply?
It runs out of the parotid gland near the neck of the mandible and supplies adjacent parts of the parotid gland as well as skin and muscles here.
What type of gland is the thyroid gland?
This is an endocrine gland.
What is the thyroid gland composed off?
It is composed of 2 lateral lobes.
Where does the thyroid gland lie?
It lies on each side of the larynx and upper tracheal cartilages.
What does the thyroid gland overlap?
It overlaps the carotid sheaths.
How are the 2 lateral lobes of the thyroid gland joined?
They are joined in front of the trachea by an isthmus of thyroid tissue.
How is each lateral lobe of the thyroid gland shaped?
It is conical in shape.
What is the lower part of the medial surface of the lobe moulded against?
Moulded against the trachea and oesophagus.
Where does the recurrent laryngeal nerve lie?
It lies in the groove between the trachea and the oesophagus.
What is the upper part of the medial surface of the lobes of the thyroid gland placed against?
Placed against the cricoid and thyroid cartilages.
Comes in relationship with the mtoor branch of the superior laryngeal nerve = external laryngeal branch.
What is embedded in each lobe on the posterior surface of the thyroid gland?
2 small parathyroid glands.
What are the parathyroid glands involved with?
They are involved with the maintainence of calcium levels in the body.
Where is the superior parathyroid gland positioned?
It is relatively constant in position and it lies in the middle of the posterior surface surface of the lobe
Where is the inferior parathyroid gland?
This lies near the inferior pole of the lobe or it could be amongst the structures that are below the lobe.
Why is it that the inferior parathyroid has a variable length?
Because the inferior thyroid develops with the thymus gland and the thymus gland descends over the anterior mediastinum of the thorax during development and it drags the inferior parathyroid gland with it. Therefore the final resting place of the parathyroid gland may be anywhere along this path of descent.
Where does the isthmus of the thymus lie?
It lies over the 2nd, 3rd and 4th tracheal rings and it joins the 2 lateral lobes.
What is the pyramidal lobe of the thyroid gland?
Often a tongue of glandular thyroid tissue springs from the upper border of the isthmus and extends upwards towards the hyoid bone.
How can the pyramidal lobe of the thyroid gland be attached to the hyoid?
It can be attached to the hyoid by a small muscular slip that is called the levator glandulae thyroideae.
Occassionally what is the levator glandulae thyroideae represented by?
It is occassionally represented by a strand of fibrous tissue.
What does the thyroid gland develop from?
It develops from the floor of the embyrological pharynx.
Where can we see the site of origin of the thyroid gland?
It can be seen near the back of the tongue as a small depression called the foramen caecum
What happens to the cells of the future gland from the foramen caecum?
These cells multiply and descend into the neck, they pass in front of the hyoid bone and loop up behind the bone and they then descend to reach their adult position.
What can we sometimes find along the pathway of development of the glandular thyroid tissue?
We can sometimes find small clusters of glandular thyroid along this pathway and they may present as midline swellings in the neck.
If glandular thyroid tissue develop in the region of the foramen caeum on the tongue, what is it called?
It is called lingual thyroid.
What else is a development remnant of the thyroid gland?
The occassional fibrous slip or pyramidal lobe that unites the isthmus to the hyoid is also a development remnant of the thyroid gland.
What are the lobes and isthmus of the thyroid gland enclosed in?
They are enclosed in a sheath of fascia which is part of a sheet of fascia that is called the pretracheal fascia.
What is the pretracheal fascia attached to?
Attached to the thyroid cartilage and the cricoid cartilage of the larynx
What does the pretracheal fascia blend with at the side?
It blends with the fascia of the carotid sheaths.
What is the significance of the fact that the thyroid gland is attached to the thyroid cartilage and the cricoid cartilage?
The thyroid gland moves with the larynx during swallowing.
What does the pretracheal fascia blend with below?
It blends with the fascia over the arch of the aorta.
What is the superior thyroid artery a branch of?
It is a branch of the external carotid artery.
What nerve does the superior thyroid artery travel with?
With the external laryngeal nerve.
What is the inferior thyroid artery a branch of?
It is a branch of the subclavian artery.
What is the course of the inferior thyroid artery?
It passes deeply behind the carotid sheath towards the gland and then divides here.
Where do the branches of the inferior thyroid artery lie?
They lie in close relationship with the recurrent laryngeal nerve.
Therefore in thyroid surgery we need to take care to preserve the external laryngeal nerve when ligating the superior thyroid artery and to preserve the recurrent laryngeal nerve whe ligating the inferior thyroid artery.
What small artery can occasionally arise from the arch of the aorta, brachiocephalic artery or left common carotid artery and ascends over the front of the trachea to supply the isthmus of the thyroid gland?
The thyroid ima.
How is blood from the thyroid gland collected?
It is connected into a venous network which is also found on the surface of the gland.
How does blood drain from the venous network?
From here it drains through 3 pairs of veins.
- superior thyroid vein
- middle thyroid vein
- inferior thyroid vein
What do the superior and middle thyroid veins enter?
They enter the internal jugular vein.
What does the inferior thyroid vein descend through?
It descends through the superior aperture of the thorax to drain into the brachiocephalic veins behind the manubrium.
What is path of lymphatics around the thyroid?
They follow vascular patterns and drain to nodes around the carotid sheath and the root of the neck.
A few drain into the upper mediastinal nodes in the thorax.
