Posterior Mediastinum And Neck Flashcards
What does the posterior mediastinum contain
• descending (thoracic) aorta
• azygos veins
• oesophagus
• thoracic duct
• sympathetic trunk and splanchnic nerves
• posterior intercostal vessels and nerves
Branches of the descending aorta
• Posterior intercostal arteries which supply the intercostal space
• Bronchial arteries which supply the lungs
• Oesophageal branches which supply the oesophagus
• Pericardial branches which supply the pericardium
• Phrenic branches which supply the diaphragm
What level of vertebrae does the descending aorta pass the diaphragm through
T12
What does the posterior intercostal arteries supply
Intercostal space
What does the bronchial arteries supply
Lungs
What does the phrenic arteries supply
Diaphragm
Azygos veins
arises in abdomen at level of L1/L2 and transverses the diaphragm to enter posterior mediastinum
• Drains blood from posterior thoracic wall and return it to superior vena cava
• Lie on the bodies of the thoracic vertebrae
What drains into the azygos veins
receives blood from the posterior intercostal veins, oesophageal veins and bronchial veins
Azygos veins system
- An azygos vein on the right side of the vertebral bodies
- A smaller (shorter) hemiazygos vein on the left side of the vertebral bodies
- One or more veins connecting the veins to each other
Oesophagus
lies to right of aorta
• Supplied by oesophageal arteries from descending aorta
• Oesophageal veins return venous blood to azygos system
• Smooth muscle wall is under autonomic control
oesophageal hiatus in the diaphragm at level of…
T10
Thoracic duct
returns most of body’s lymph to venous system
• Lies between azygos vein and aorta
• Lymph from lower limbs, pelvis and abdomen flow towards the cisterns chylomicrons ( a sac-like swelling that gives rise to the thoracic duct) which ascends into the thorax
• In the thorax- duct receives lymph from intercostal spaces and lymph nodes
• Duct ascends into neck- receives lymph from left side of head, neck and left upper limb
• Terminates by opening into the venous system at junction between left internal jugular vein and left subclavian vein
• Right side of head , neck and right upper limb are drained by lymphatic ducts that enter the venous system at junction between the right internal jugular and right subclavian veins
What do the posterior intercostal spaces contain
• intercostal muscles
• a posterior intercostal artery (a branch of the thoracic aorta)
• a posterior intercostal vein (which drains to the azygos system)
• a posterior intercostal nerve
Sympathetic trunk
trunks lie on posterior thoracic wall, either side of the vertebral column and posterior to parietal pleura
• Thin, longitudinal fibre tracts interspersed with ganglia (paravertebral ganglia)
• Trunk extends from skull base to coccyx
Facial nerve (CN VII)
supplies platysma in neck
glossopharyngeal nerve (CN IX)
pharynx (sensory innervation)
• carotid sinus (visceral sensory fibres that return to the CNS via CN IX)
Contains:
•Somatic sensory fibres > sensation in the pharynx and posterior 1/3 of the tongue
•Special sense fibres > taste posterior 1/3 of the tongue
•Vital for swallowing
Vagus nerve (CN X)
vital for normal speech and swallowing
• the muscles of the pharynx (motor innervation)
• the larynx (motor and sensory innervation)
• In the neck, the vagus nerve runs between the internal jugular vein and the internal carotid artery (above its bifurcation) and between the internal jugular vein and common carotid artery (below its bifurcation). The three structures run together in a fascial sleeve called the carotid sheath.
Parasympathetic fibres > thoracic and abdominal viscera
•Visceral sensory fibres > internal monitoring and physiological reflexes
Accessory nerve (CN XI)
sternocleidomastoid and trapezius muscles.
Somatic motor fibres only
hypoglossal nerve (CN XII)
motor to the muscles of the tongue.
• It does not supply any structures in the neck but travels through it.
• It lies lateral to the internal carotid artery and deep to the external jugular vein.
Phrenic nerves
formed by C3, C4 and C5 nerve fibres.
• It descends through the neck to enter the thorax.
• It innervates the left and right ipsilateral diaphragm (and the pericardium)
Sympathetic fibres
sympathetic trunk extends as far as the base of the skull.
• The associated sympathetic ganglia in the neck are the superior, middle, and inferior cervical ganglia.
• Postganglionic fibres from these ganglia innervate the head and neck.
External jugular vein
drains blood from scalp and face
• Joins subclavian vein
Internal jugular vein
major vein in the neck, which drains blood from the brain and part of the face. (dural venous sinuses in cranium)
• It unites with the subclavian vein, which returns blood from the upper limb, to form the brachiocephalic vein.
• The right and left brachiocephalic veins unite to form the superior vena cava.
Descends in neck with carotid artery and vagus nerve
Subclavian artery
gives rise to several vessels.
• A large branch, the thyrocervical trunk, gives rise to the inferior thyroid artery.
• The subclavian artery supplies the upper limb.
Common carotid arteries:
ascend in the right and left sides of the neck, respectively.
• The pulsation of the internal carotid can be palpated immediately lateral to the larynx.
• The common carotid arteries bifurcate into external and internal carotid arteries.
• The internal carotid artery does not give rise to any branches in the neck. It enters the cranium and supplies the brain.
• The external carotid artery gives rise to several branches that supply the head and neck, including the pharynx, scalp, thyroid gland, tongue, and the face.
• At the point of bifurcation of the common carotid artery there is a small swelling - the carotid sinus. Baroreceptors here constantly monitor arterial blood pressure. This visceral sensory information is relayed back to the CNS via the glossopharyngeal nerve and results in reflex responses that regulate the blood pressure.
internal carotid artery
does not give rise to any branches in the neck. It enters the cranium and supplies the brain.
external carotid artery
gives rise to several branches that supply the head and neck, including the pharynx, scalp, thyroid gland, tongue, and the face.
carotid sinus.
At the point of bifurcation of the common carotid artery there is a small swelling - the carotid sinus. Baroreceptors here constantly monitor arterial blood pressure. This visceral sensory information is relayed back to the CNS via the glossopharyngeal nerve and results in reflex responses that regulate the blood pressure.
Cervical vertebra
7 cervical vertebrae- small and articulate with each other at facet joints orientated obliquely (allows for good range of flexion and extension in cervical spine compared to thoracic spine)
Hyoid bone
slender u-shaped bone situated anteriorly in upper neck, inferior to mandible. Helps keep pharynx open and provides an attachment point for several muscles in the neck and tongue
Larynx
composed of a skeleton of small cartilages connected by membranes and small joints. It protects the airway, muscles attach to the laryngeal cartilages and move them, in turn moving the vocal cords and allowing phonation
Vocal ligaments within thyroid cartilage
Suprahyoid muscle
4 paired muscles lie superior to hyoid bone and form floor of mouth
• When contract, raise hyoid bone and larynx during speech and swallowing
• mylohyoid, geniohyoid, stylohyoid and digastric
Infrahyoid muscles
4 paired ‘strap’ muscles lie inferior to hyoid bone, lateral to anterior midline of neck
• Draw hyoid bone and larynx inferiorly during speech and swallowing
• Sternohyoid and omohyoid lie superficially; they attach the hyoid to the sternum and scapula, respectively.
• Sternothyroid and thyrohyoid lie deep; they attach the sternum to the thyroid cartilage and the thyroid cartilage to the hyoid, respectively.
Thyroid gland
composed of left and right lobes that lie lateral to lower larynx and upper trachea
• Each lobe lies deep to sternothyroid muscle
• 2 lobes joined by the isthmus, which lies anterior to trachea
• Produces hormones- pituitary gland regulates its secretion
• Blood supply from: left and right superior thyroid arteries (branches of external carotid arteries) and left and right inferior thyroid arteries (branches of thyrocervical trunks)
• Some people have additional thyroid ima artery
• Superior, middle and inferior thyroid veins drain the thyroid gland
Isthmus
Joins 2 lobes of thyroid gland
Blood supply to thyroid gland
left and right superior thyroid arteries (branches of external carotid arteries) and left and right inferior thyroid arteries (branches of thyrocervical trunks)
• Some people have additional thyroid ima artery
• Superior, middle and inferior thyroid veins drain the thyroid gland
Parathyroid glands
usually 4 (right and left superior and inferior glands) located posterior to the thyroid gland
• produce parathyroid hormone which plays a role in calcium regulation.
• are typically supplied by the inferior thyroid arteries.
What does the neck contain
• structures of the respiratory tract - the pharynx, larynx, and trachea
• structures of the gastrointestinal tract - the pharynx and oesophagus
• glands - the thyroid and parathyroid glands
• arteries and veins that serve the neck and head, including the brain
• nerves that serve the head and neck, upper limbs, thoraco-abdominal viscera (via the vagus nerves) and the diaphragm (via the phenic nerves)
• several groups of muscles. These include muscles that move the head and neck, move the larynx in speech and swallowing and that form the floor of the mouth. Platysma is a very thin subcutaneous muscle deep to the skin of the neck.
Platsyma
very thin subcutaneous muscle deep to the skin of the neck.
Triangles of the neck
neck described in terms of anterior and posterior triangles separated by sternocleidomastoid muscle
• Sternocleidomastoid (SCM) is attached to the sternum, clavicle, and the mastoid process (part of the temporal bone). It can act unilaterally or bilaterally (i.e. both the left and right muscles act together). It is innervated by the accessory nerve (cranial nerve XI).
Anterior triangle boundaries
anteriorly (midline of neck), posteriorly (anterior border of sternocleidomastoid), superiorly (lower border of mandible)
What does the anterior triangle contain
• the trachea and larynx
• the thyroid gland, parathyroid glands, and the submandibular salivary gland
• the suprahyoid muscles which connect the hyoid to the skull- form the floor of the mouth and move the hyoid and larynx in speech and swallowing.
• the infrahyoid muscles (‘strap’ muscles)- they connect the hyoid to the sternum and scapula. They move the hyoid and larynx in speech and swallowing.
• the common carotid artery and its terminal branches (the external and internal carotid arteries)
• branches of the external carotid artery to the head and neck
• the internal jugular vein
• branches of the facial nerve (CN VII), the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory nerve (CN XI) and the hypoglossal nerve (CN XII).
• the ansa cervicalis (fibres from C1-C3 which innervate the infrahyoid muscles).
Ansa cervicalis
fibres from C1-C3 which innervate the infrahyoid muscles
Posterior triangle boundaries
anteriorly (posterior border of sternocleidomastoid), posteriorly (anterior border of trapezius), inferiorly (clavicle), superiorly (apex formed by sternocleidomastoid and trapezius)
What does the posterior triangle contain
• muscles that move the head
• part of the subclavian artery and the subclavian vein
• the external jugular vein which drains the scalp and face
• the accessory nerve (CN XI)
• the roots of the brachial plexus (spinal nerves that supply the upper limb)
• the cervical plexus (fibres from C1-4)
• the phrenic nerve.
Pulmonary plexus
innervates bronchi. Sympathetic relaxes bronchi, parasympathetic constricts them
Oesophageal plexus
overlies anterior surface of oesophagus. Sympathetic inhibit peristalsis, parasympathetic stimulate peristalsis
Visceral afferents
relay sensory information from viscera back to CNS along paths of vagus and splanchnic nerves
Cardiac plexus
innervates SAN. Sympathetic fibres increase heart rate and force of contraction, parasympathetic decrease heart rate and force of contraction
Innervation of the thoracic viscera:
cardiopulmonary splanchnic nerves convey postganglionic sympathetic fibres to the thoracic viscera
• Vagus nerves convey parasympathetic fibres to the thoracic viscera
• Form autonomic plexuses (fine meshes) around the viscera: cardiac plexus, pulmonary plexus, oesophageal plexus
Cardiac referred pain:
Cardiac pain is typically felt in the central chest, left side of the neck and left arm- referred pain (felt in another region of the body)
• heart is innervated by the cardiac plexus, composed of sympathetic and parasympathetic fibres. The sympathetic fibres travel to the cardiac plexus and heart from spinal cord segments T1 -T5 via the cardiopulmonary splanchnic nerves.
• The heart is also innervated by visceral sensory nerves, which convey sensory information from the heart back to the CNS - this sensation normally does not reach our conscious perception. However, if the myocardium is ischaemic this sensation does reach our conscious perception, and is interpreted as pain, tightness, crushing pressure or burning, which may be severe.
• Because the visceral sensory nerves travel back to the CNS alongside the sympathetic fibres that innervate the heart, the visceral sensory information enters spinal cord segments T1 - T5. However, somatic sensory information from the skin of the chest wall, neck and arm also returns to spinal cord segments T1 - T5.
• Therefore painful visceral sensory information from the heart and somatic sensory information from the chest wall both enter spinal cord segments T1 - T5. For reasons that are not fully understood, the brain interprets the cardiac pain as coming from the chest, neck, and arm.
referred pain is shoulder pain resulting from pathology of the diaphragm.
Cervical spinal cord segments 3-5 contribute spinal nerve fibres to the phrenic nerve. Cord segments C3-5 also contribute to the nerves that innervate the skin of the neck and shoulder. The brain interprets pain coming from the diaphragm as coming from the shoulder region.
Pathway of sympathetic trunk
• Cell bodies of preganglionic sympathetic neurons lie in thoracic and upper lumbar spinal cord segments (T1-L2/3)
• Are visceral motor fibres that leave the pineal cord from its ventral aspect and enter spinal nerves T1-L2/3 along with somatic motor nerves (cell bodies lie in ventral grey horn)
• sympathetic trunk allows the sympathetic fibres arising from T1 - L2/3 to be distributed to all parts of the body
• Preganglionic sympathetic fibres exit the spinal cord in spinal nerves T1 - L2/3.
• Almost immediately, they separate from the spinal nerves and enter the sympathetic trunk via a short communicating / connecting branch (white ramus communicans).
3 things that preganglionic axon does in sympathetic trunk
- synapses in the ganglion at its level of entry
- ascends or descends in the trunk before synapsing in a ganglion
- travels through a ganglion (and the trunk) without synapsing
If the preganglionic axon
- synapses in the ganglion at its level of entry
- ascends or descends in the trunk before synapsing in a ganglion
In scenarios 1 and 2, the postganglionic axons leaving the ganglia:
1. enter spinal nerves via a communicating branch (grey ramus communicans). Through this arrangement, sympathetic fibres enter all 31 pairs of spinal nerves
2. form visceral nerves that convey sympathetic fibres to the head
3. form visceral nerves that convey sympathetic fibres to the thoracic viscera (cardiopulmonary splanchnic nerves).
If the preganglionic axon
- travels through a ganglion (and the trunk) without synapsing
• In scenario 3, the sympathetic preganglionic axons travel through the sympathetic trunk without synapsing. These fibres exit the trunk and form the abdominopelvic splanchnic nerves:
• Greater splanchnic nerve (sympathetic preganglionic fibres originating from T5-T9 segments of the spinal cord)
• Lesser splanchnic nerve (from T10-11)
• Least splanchnic nerve (from T12)
• Lumbar splanchnic nerves (from L1–L2)
greater, lesser, and least splanchnic nerves
formed in the posterior mediastinum and traverse the diaphragm to enter the abdomen.
• The preganglionic sympathetic fibres in these splanchnic nerves do ultimately synapse with second neurons in prevertebral ganglia that lie close to major blood vessels in the abdomen.
• After synapsing, the postganglionic fibres innervate abdominal viscera
cisterns chylomicrons/ cisterna chyli
Lymph from lower limbs, pelvis and abdomen flow towards the cisterns chylomicrons ( a sac-like swelling that gives rise to the thoracic duct) which ascends into the thorax
Greater splanchnic nerve
sympathetic preganglionic fibres originating from T5-T9 segments of the spinal cord
Supplies: stomach, first half of duodenum, liver, gallbladder and pancreas
Lesser splanchnic nerve
from T10-11
Supplies: second half of duodenum, small intestine, large intestine up to 2/3 along transverse colon
Least splanchnic nerve
from T12
Supplies first half of rectum and rest of large intestine
Lumbar splanchnic nerves
from L1–L2
4 suprahyoid muscles
mylohyoid, geniohyoid, stylohyoid and digastric
4 infrahyoid strap muscles
Sternohyoid and omohyoid
Sternothyroid and thyrohyoid
Transverse foramina
Transmit and protect the vertebral arteries-> brain
Which cervical vertebra are structurally different
C1 and C2 to be able to turn neck
Cervical vertebral foramen
Triangle-shaped and relatively large compared to size of vertebrae- allows extra room for cervical spinal cord
Oblique joints between C spine
Good range of movement: flexion, extension, lateral flexion
But more likely to get injuries
Which 2 laryngeal cartilages are palpable in the anterior midline of the neck
Thyroid and cricoid
Epiglottis
Cartilage that Closes of larynx when swallowing
Cranial nerves
Attached to the brain or brainstem
12 pairs (left and right)
Contains combinations of somatic motor, somatic sensory, special sensory and parasympathetic fibres
CNs IX, X, XI and XII found in neck
Pharynx
Muscular tube
•Part of the respiratory and GI systems
•Three parts > nasopharynx, oropharynx, laryngopharynx
Formed by constrictor muscles
•Swallowed fluid and food prevented from entering the larynx by the epiglottis > diverted into the oesophagus instead
3 parts of pharynx
nasopharynx, oropharynx, laryngopharynx
Branches of external carotid artery
Maxillary artery
Facial artery
Lingual artery
Occipital artery
Superficial temporal artery
Posterior auricular artery
Extrinsic laryngeal muscles
Move the larynx as a whole ‘unit’ with speech and swallowing
•Suprahyoid and infrahyoid muscles
Intrinsic laryngeal muscles
Move the individual cartilages and the vocal cords
•Innervated by the vagus nerve (most via the recurrent laryngeal branch)
Lymphatics of neck
Superficial and deep nodes
•Superficial nodes along the path of the external jugular vein
•Deep nodes along the internal jugular vein – ultimately receive all lymph from the head and neck
•Can become enlarged in local and systemic disease
•Examined and can be biopsied
Major nerves in neck
phrenics and CNs IX, X, XI and XII.
Where do Recurrent laryngeal nerves lie
lie close to the thyroid gland and are potentially at risk in thyroid surgery.
carotid sheath
In the neck, the vagus nerve runs between the internal jugular vein and the internal carotid artery (above its bifurcation) and between the internal jugular vein and common carotid artery (below its bifurcation). The three structures run together in a fascial sleeve
Why is there no parasympathetic trunk
Nerves arise from vagus nerve and sacrum
Nucleus
Cell bodies inside CNS
How many neurones per sympathetic pathway
2
Sections of spinal cord
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
Plexus
Fibres converge
White ramus communicans
Connecting branch To ganglion
Grey ramus communicans
Fibres away from ganglion
Transverse foramina
Protects vertebral artery which supplies the brain
Goiter
Enlarged thyroid
Which blood vessels are protected by the transverse foramina? What do these blood vessels supply?
Vertebral arteries- supply brain (posteriorly) and spinal cord
Why is the hyoid bone unique
Only bone that doesn’t articulate with any other bones
Scalene muscles
three paired muscles (anterior, middle and posterior), located in the lateral aspect of the neck.
Collectively, they form part of the floor of the posterior triangle of the neck.
The scalenes act as accessory muscles of respiration and perform flexion at the neck.
The infrahyoid (‘strap’) muscles depress which TWO structures during speech and swallowing?
Hyoid bone
Larynx
Sympathetic fibres that travel to the cardiac plexus originate from which segments of the spinal cord?
T1-T5
Sympathetic fibres that travel to the brachial plexus originate from which segments of the spinal cord?
C5-T1
The superior thyroid artery is a branch of which other artery
External carotid artery
Muscles of larynx: superficial to deep
Platysma
Sternocleidomastoid
Sternohyoid
Cricothyroid
Vocalis
