Anatomy of the neck part 2 Flashcards
Where does the bifurcation of the common carotids occur
The superior part of each common carotid artery and its division into external and internal carotid arteries occurs in the carotid triangle (Fig. 8.166), which is a subdivision of the anterior triangle of the neck
Describe the carotid sinus
At the bifurcation, the common carotid artery and the beginning of the internal carotid artery are dilated. This dilation is the carotid sinus (Fig. 8.167) and contains receptors that monitor changes in blood pressure and are innervated by a branch of the glossopharyngeal nerve [IX].
Describe the carotid body
Another accumulation of receptors in the area of the bifurcation is responsible for detecting changes in blood chemistry, primarily oxygen content. This is the carotid body and is innervated by branches from both the glossopharyngeal [IX] and vagus [X] nerves.
Summarise the internal carotid arteries
After its origin, the internal carotid artery ascends toward the base of the skull (Fig. 8.167). It gives off no branches in the neck and enters the cranial cavity through the carotid canal in the petrous part of the temporal bone.
The internal carotid arteries supply the cerebral hemispheres, the eyes and the contents of the orbits, and the forehead.
Summarise the external carotid arteries
The external carotid arteries begin giving off branches immediately after the bifurcation of the common carotid arteries
What does the internal jugular vein drain; describe its basic appearance and where it exits the skull
Collecting blood from the skull, brain, superficial face, and parts of the neck, the internal jugular vein begins as a dilated continuation of the sigmoid sinus, which is a dural venous sinus. This initial dilated part is referred to as the superior bulb of jugular vein and receives another dural venous sinus (the inferior petrosal sinus) soon after it is formed. It exits the skull through the jugular foramen associated with the glossopharyngeal [IX], vagus [X], and accessory [XI] nerves, and enters the carotid sheath.
Describe the passage of the internal jugular vein
The internal jugular vein traverses the neck within the carotid sheath, initially posterior to the internal carotid artery, but passes to a more lateral position farther down. It remains lateral to the common carotid artery through the rest of the neck with the vagus nerve [X] posterior and partially between the two vessels.
The paired internal jugular veins join with the subclavian veins posterior to the sternal end of the clavicle to form the right and left brachiocephalic veins
List some tributaries of the internal jugular vein
Tributaries to each internal jugular vein include the inferior petrosal sinus, and the facial, lingual, pharyngeal, occipital, superior thyroid, and middle thyroid veins.
Describe the importance of the jugular venous pulse
The jugular venous pulse is an important clinical sign that enables the physician to assess the venous pressure and waveform and is a reflection of the functioning of the right side of the heart
Which cranial nerves pass through the anterior triangle
The cranial nerves in these categories include the facial [VII], glossopharyngeal [IX], vagus [X], accessory [XI], and hypoglossal [XII
Branches of which spinal nerve pass through the anterior triangle
Branches of spinal nerves in these categories include the transverse cervical nerve from the cervical plexus and the upper and lower roots of the ansa cervicalis.
Describe the facial nerve in the anterior triangle
After emerging from the stylomastoid foramen, the facial nerve [VII] gives off branches that innervate two muscles associated with the anterior triangle of the neck:
▪
the posterior belly of the digastric, and
▪
the stylohyoid.
The facial nerve [VII] also innervates the platysma muscle that overlies the anterior triangle and part of the posterior triangle of the neck.
Describe the passage of the glossopharyngeal nerve
It begins its descent between the internal carotid artery and the internal jugular vein, lying deep to the styloid process and the muscles associated with the styloid process. As the glossopharyngeal nerve [IX] completes its descent, it passes forward between the internal and external carotid arteries, and curves around the lateral border of the stylopharyngeus muscle (Fig. 8.168). At this point, it continues in an anterior direction, deep to the hyoglossus muscle, to reach the base of the tongue and the area of the palatine tonsil.
What does the glossopharyngeal nerve innervate in the anterior triangle
As the glossopharyngeal nerve [IX] passes through the area of the anterior triangle of the neck it innervates the stylopharyngeus muscle, sends a branch to the carotid sinus, and supplies sensory branches to the pharynx.
Describe the basic course of the vagus nerve
The vagus nerve [X] exits the cranial cavity through the jugular foramen between the glossopharyngeal [IX] and accessory [XI] nerves.
Outside the skull the vagus nerve [X] enters the carotid sheath and descends through the neck enclosed in this structure medial to the internal jugular vein and posterior to the internal carotid and common carotid arteries
Describe the branches of the vagus nerve in the anterior triangle
Branches of the vagus nerve [X] as it passes through the anterior triangle of the neck include a motor branch to the pharynx, a branch to the carotid body, the superior laryngeal nerve (which divides into external and internal laryngeal branches), and possibly a cardiac branch.
Describe the basic course of the accessory nerve
The accessory nerve [XI] is the most posterior of the three cranial nerves exiting the cranial cavity through the jugular foramen. It begins its descent medial to the internal jugular vein, emerging from between the internal jugular vein and internal carotid artery to cross the lateral surface of the internal jugular vein as it passes downward and backward to disappear either into or beneath the anterior border of the sternocleidomastoid muscle
Does the accessory nerve give off any branches in the anterior triangle
The accessory nerve gives off no branches as it passes through the anterior triangle of the neck.
BUT it does innervate the sternocleidomastoid and trapezius muscle
How would you test the function of the accessory nerve
Ask the patient to shrug their shoulders and hold it there
Where does the accessory nerve exit the skull?
The accessory nerve begins in the upper spinal cord and ascends to enter the skull through the foramen magnum
The accessory nerve then leaves via the jugular foramen
Describe the basic course of the hypoglossal nerve
The hypoglossal nerve [XII] leaves the cranial cavity through the hypoglossal canal and is medial to the internal jugular vein and internal carotid artery immediately outside the skull. As it descends, it passes outward between the internal jugular vein and internal carotid artery (Fig. 8.171). At this point it passes forward, hooking around the occipital artery, across the lateral surfaces of the internal and external carotid arteries and the lingual artery, and then continues deep to the posterior belly of the digastric and stylohyoid muscles. It passes over the surface of the hyoglossus muscle and disappears deep to the mylohyoid muscle.
Are there any branches of the hypoglossal nerve in the anterior triangle
The hypoglossal nerve [XII] leaves the cranial cavity through the hypoglossal canal and is medial to the internal jugular vein and internal carotid artery immediately outside the skull. As it descends, it passes outward between the internal jugular vein and internal carotid artery (Fig. 8.171). At this point it passes forward, hooking around the occipital artery, across the lateral surfaces of the internal and external carotid arteries and the lingual artery, and then continues deep to the posterior belly of the digastric and stylohyoid muscles. It passes over the surface of the hyoglossus muscle and disappears deep to the mylohyoid muscle.
Describe the transverse cervical nerve
Branch of cervical plexus arising from the anterior rami of C2-3.
It emerges deep to the posterior border of the sternocleidomastoid, near the middle of the muscle, and loops around the muscle to cross its anterior surface in a transverse direction.
It continues across the neck and provides cutaneous innervation to this area.
Describe the ansa cervicalis
A loop of nerve fibres from C1-C3 that innervate the ‘strap muscles’ in the anterior triangle of the neck.
It begins as branches of the cervical nerve C1 join the hypoglossal nerve soon after it leaves the skull.
Superior and inferior roots innervate the superior and inferior bellies of the omohyoid muscle respectively.
Describe the anatomical location of the oesophagus
The oesophagus is part of the G.I system and has a short course in the lower neck. It begins at C6, where it is continuous with the pharynx above and courses inferiorly to pass through the thoracic inlet. It lies directly anterior to the vertebral column.
Describe the anatomical location of the trachea
Part of lower airway and, like the oesophagus, begins at C6, where it is continuous with the larynx above. The larynx lies directly anterior to the oesophagus and passes inferiorly in the midline to enter the thorax.
Describe the anatomical location of the pharynx and larynx
Pharynx- common pathway for air and food, and it connects respiratory and digestive compartments in the head with similar compartments in the lower neck
The larynx is the upper end of the lower airway. It is continuous with the trachea below and the pharynx poster superiorly.
Describe the basic structure of the thyroid gland
The thyroid gland is anterior in the neck below and lateral to the thyroid cartilage. It consists of two lateral lobes (which cover the anterolateral surfaces of the trachea, the cricoid cartilage, and the lower part of the thyroid cartilage) with an isthmus that connects the lateral lobes and crosses the anterior surfaces of the second and third tracheal cartilages.
Describe the anatomical location of the thyroid gland
Lying deep to the sternohyoid, sternothyroid, and omohyoid muscles, the thyroid gland is in the visceral compartment of the neck. This compartment also includes the pharynx, trachea, and esophagus and is surrounded by the pretracheal layers of fascia.
Describe the key features of the parathyroid glands
The parathyroid glands are two pairs of small, ovoid, yellowish structures on the deep surface of the lateral lobes of the thyroid gland. They are designated as the superior and inferior parathyroid glands. However, their position is quite variable and they may be anywhere from the carotid bifurcation superiorly to the mediastinum inferiorly.
Out of the triangles which constitute the anterior triangle of the neck, which is the only unpaired triangle?
the submental triangle.
What is the function of the trapezius
To elevate the shoulders
What are the muscles of the anterior triangle mainly associated with
Moving mandible. hyoid and larynx (or stabilising these structures during swallowing)
What is the posterior triangle mainly filled with
Nerves and vessels on their way down to the neck and the limbs
Where is the posterior triangle found
The posterior triangle of the neck is on the lateral aspect of the neck in direct continuity with the upper limb
Describe the borders of the posterior triangle
▪
anteriorly by the posterior edge of the sternocleidomastoid muscle,
▪
posteriorly by the anterior edge of the trapezius muscle,
▪
basally by the middle one-third of the clavicle, and
▪
apically by the occipital bone just posterior to the mastoid process where the attachments of the trapezius and sternocleidomastoid come together.
What are the key structures found in the posterior triangle
External jugular vein Subclavian artery Subclavian vein Trunks of the brachial plexus Phrenic nerve Vagus nerve Spinal accessory nerve
What layer of fascia is found at the roof of the posterior triangle
The roof of the posterior triangle consists of an investing layer of cervical fascia that surrounds the sternocleidomastoid and trapezius muscles as it passes through the region.
What fascia is found at the floor of the posterior triangle
The muscular floor of the posterior triangle is covered by the prevertebral layer of cervical fascia; and from superior to inferior consists of the splenius capitis, levator scapulae, and the posterior, middle, and anterior scalene muscles.
Describe the origin and insertion of the trapezius
Origin: Superior nuchal line; external occipital protuberance; ligamentum nuchae; spinous processes of vertebrae CVII to TXII
Insertion: Lateral one-third of clavicle; acromion; spine of scapula
Describe the innervation and function of the trapezius
Motor—accessory nerve [XI]; proprioception—C3 and C4
Assists in rotating the scapula during abduction of humerus above horizontal;
upper fibers—elevate,
middle fibers—adduct,
lower fibers—depress scapula
Describe the origins and insertions of the sternocleidomastoid
Sternal head:
origin- Upper part of anterior surface of manubrium of sternum
insertion- Lateral one-half of superior nuchal line
clavicular head:
origin- Superior surface of medial one-third of clavicle
insertion - Lateral surface of mastoid process
Describe the innervation and function of the sternocleidomastoid
Accessory nerve [XI] and branches from anterior rami of C2 to C3 (C4)
Individually—will tilt head toward shoulder on same side rotating head to turn face to opposite side; acting together, draw head forward
List the muscles found in the posterior triangle
Trapezius Sternocleidomastoid Splenius capitis Levator scapulae Posterior scalene Middle scalene Anterior scalene Omohyoid
Describe the superior and inferior bellies of the omohyoid
The superior belly is in the anterior triangle.
▪
The inferior belly crosses the posterior triangle, subdividing it into a small, omoclavicular or subclavian triangle inferiorly and a much larger occipital triangle superiorly.
Describe the formation of the external jugular vein
One of the most superficial structures passing through the posterior triangle of the neck is the external jugular vein (Fig. 8.181). This large vein forms near the angle of the mandible, when the posterior branch of the retromandibular and posterior auricular veins join, and descends through the neck in the superficial fascia.
Outline the basic course of the external jugular vein
After crossing the sternocleidomastoid muscle, the external jugular vein enters the posterior triangle and continues its vertical descent.
In the lower part of the posterior triangle, the external jugular vein pierces the investing layer of cervical fascia and ends in the subclavian vein.
What are the tributaries of the external jugular vein
Tributaries to the external jugular vein while it traverses the posterior triangle of the neck include the transverse cervical, suprascapular, and anterior jugular veins.
Which part of the subclavian artery is found in the posterior triangle of the neck
Several arteries are found within the boundaries of the posterior triangle of the neck. The largest is the third part of the subclavian artery as it crosses the base of the posterior triangle
Describe the first part of the subclavian artery
The first part of the subclavian artery ascends to the medial border of the anterior scalene muscle from either the brachiocephalic trunk on the right side or directly from the arch of the aorta on the left side. It has numerous branches.
Describe the second part of the subclavian artery
The second part of the subclavian artery passes laterally between the anterior and middle scalene muscles, and one branch may arise from it.
Describe the third part of the subclavian artery
The third part of the subclavian artery emerges from between the anterior and middle scalene muscles to cross the base of the posterior triangle. It extends from the lateral border of the anterior scalene muscle to the lateral border of rib I where it becomes the axillary artery and continues into the upper limb.
Describe the branches of the first two parts of the subclavian arteries
first part
vertebral artery: courses cranially to supply the posterior cerebral circulation
internal thoracic artery: courses caudally
thyrocervical trunk: very short trunk that soon divides into 4 branches
second part
costocervical trunk: courses cranially before bifurcating
Which branch may arise from the third part of the subclavian artery
A single branch (the dorsal scapular artery) may arise from the third part of the subclavian artery. This branch passes posterolaterally to reach the superior angle of the scapula where it descends along the medial border of the scapula posterior to the rhomboid muscles.
