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.