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What is the mediastinum?
3-D space between pleural cavities that extends vertically from thoracic inlet and to thoracic outlet
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What are the divisions of the mediastinum?
- superior mediastinum
- inferior mediastinum
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What separates the superior mediastinum from the inferior mediastinum?
imaginary plane that passes through sternal angle and interverterbral disc between T4-5 vertebrae
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Which vessel is just below the superior mediastinum?
pulmonary trunk and arteries
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Where is the inferior mediastinum?
lies below the imaginary plane separating the two divisions
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What are the subdivisions of the inferior mediastinum?
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What makes up the middle (central) component of the inferior mediastinum?
heart and pericardium
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What is contained in the superior mediastinum?
- all structures entering and exiting thoracic inlet
- thymus gland
- great vessels of heart
- ligamentum arteriosum
- 3 branches of aortic arch
- phrenic nerves
- vagal nerves
- left recurrent laryngeal nerve
- trachea
- esophagus
- cardiac plexuses
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Where is the thymus gland found?
- superior mediastinum
- anterior mediastinum
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Where is the anterior mediastinum?
located posterior to sternum, just in front of pericardium
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What is found in the anterior mediastinum?
thymus gland
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Which mediastinum are the heart and pericardial sac found?
middle mediastinum
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Where is the middle mediastinum located?
between anterior and posterior mediastinum
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Where is the posterior mediastinum located?
- between middle mediastinum (pericardium) and anterior longitudinal ligament
- stretches from T5-12
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What does the anterior longitudinal ligament cover?
anterior surface of vertebral column
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What is contained in the posterior mediastinum?
structures oriented either vertically or horizontally
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What vertically oriented structures are found in the posterior mediastinum?
- descending thoracic aorta
- thoracic duct
- esophagus
- vagus nerves
- azygos system of veins
- greater splanchnic nerve
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What horizontally oriented structures are found in the posterior mediastinum?
intercostal arteries, veins, and nerves
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What is the esophagus? What does it connect?
muscular tube connecting pharynx w/ stomach
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Where does the esophagus begin?
- in neck
- level of larynx/C6 vertebra
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What does the esophagus descend through?
thorax
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What does the esophagus lie next to?
aorta
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After the esophagus descends through the thorax what does it enter?
abdominal cavity
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What does the esophagus pass through before it enters the abdominal cavity?
esophageal hiatus in respiratory diaphragm
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Is the esophagus normally collapsed or held open?
collapsed
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Approximately how wide is the esophagus?
1" wide
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About how long is the esophagus?
12" long
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The esophagus extends vertically from which vertebrae levels?
C6-T11
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Where are the locations of the constrictions of the esophagus?
- at commencement (origin)
- where passes posterior to aortic arch
- where passes posterior to left main bronchus
- where passes through esophageal hiatus
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Why are the constrictions of the esophagus important?
- constrictions can adhese and block the pathway for food
- doctors must know location when doing a scope
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Is the esophagus anterior or posterior to the anterior longitudinal ligament?
anterior
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While in the neck and superior mediatinum, the esophagus is anteiror or posterior to the trachea?
posterior
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While in inferior mediastinum, the esophagus is anterior or posterior to left atrim?
posterior
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What innervates the esophagus?
vagal nerves from nerve network
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The vagal nerves come from which nerve network?
esophageal plexus
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Where is the esophageal plexus?
on external surface of esophagus
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Do the vagal nerves provide sensory or motor fibers to the esophagus?
both
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Where does the arterial supply of the esophagus begin?
in cervical region
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Where does the arterial supply of the esophagus extend?
to abdominal region
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What provides arterial supply to the esophagus?
- inferior thyroid arteries
- bronchial arteries
- aortic esophageal arteries (2 or 3)
- left gastric artery
- inferior phrenic arteries
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What do the esophageal veins correspond to?
the arteries which supply it
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Many of the esophageal veins are tributaries to what?
azygos system of veins
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Why is venous drainage of esophagus clinically important?
possibility of esophageal varices, observed in patients w/ cirrhosis of the liver
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The left gastric vein provides dirct connection between what?
esophageal venous plexus and hepatic portal system
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Where does the hepatic portal system receive venous blood from?
gastrointestinal tract
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What can the venous blood from the gastrointestinal tract bypass and return to the right atrium?
cirrhotic liver
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How does venous blood bypass a cirrhotic liver and return to the right atrium?
via esophageal venous plexus
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What happens if esophageal venous plexus becomes engorged with blood?
- causes many vessels to dilate and become subject to rupture
- esophageal varicise (varicose veins in esophagus)
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Where does the esophageal lymphatic plexus drain?
posterior intercostal and mediastinal nodes
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Where do the posterior intercostal and mediastinal nodes drain to?
thoracic duct and/or bronchomediastinal trunks
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What is the descending thoracic aorta continuous with?
aortic arch
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What vertebrae levels does the descending thoracic aorta run along?
extends from T4-12
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What is at the level of T4-12 vertebrae?
aortic hiatus in diaphragm
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Where does the descending thoracic aorta deviate?
from left toward midline
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What are the branches of the descending thoracic aorta in the thorax (posterior mediastinum)?
- bronchial
- esophageal
- pericardial
- mediastinal arteries to lymph nodes
- posterior intercostal
- subcostal arteries
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How many pairs of posterior intercostal areteries are there from the descending thoracic aorta?
8 pairs
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What do the 8 pairs of posteiror intercostal arteries supply?
intercostal spaces 3-11
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How many subcostal arteries are there?
one pair
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Where does the azygos system of veins collect blood from?
- posterior intercostal spaces
- esophagus
- respiratory diaphragm
- pericardium
- bronchi
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Are the azygos system of veins fairly consistent from one body to the next?
no, considerable individual variation
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Where does the azygos system of veins commence (begin)?
at inferior vena cava
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Where does the azygos system of veins ascend?
along vertebral bodies
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Where does the azygos system of veins terminate?
in superior vena cava (arches over right main bronchus)
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Where are the hemiazygos veins?
on left side of aorta
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What are the hemiazygos veins tributaries to?
azygos vein
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What are the tributaties to the azygos system of veins?
- posteiror intercostal
- esophageal
- phrenic
- bronchial
- pericardial
- mediastinal
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Does the right recurrent laryngeal nerve enter the thorax?
no, it is only in the nck
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Which nerve is next to the ligamentum arteriosum?
left recurrent laryngeal N
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What was the ligamentum arteriosum in the embryo?
ductus arteriosus (vessel in embryo that closes off to form ligament)
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What is the thymus gland important in?
in immune system
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When is the thymus gland large?
in infants
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What is the size and shape of the thymus in newborns?
varies
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What do doctors called large thymus glands in newborns?
Thymic "sail"
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Within the first years of life, T-cells in the thymus leave the gland to go where?
to other lymphatics throughout body to set up clones to produce T-cells
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After migration of the T-cells, what happens to the thymus gland?
gets smaller (happens by age 2 or 3)
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After migration, what is left of the thymus gland?
- fatty connective tissue
- no functional thymic tissues
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Which arteries supply thymus gland?
internal thoracic arteries, not aorta
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Where is the boundary line between the superior and inferior mediastinum?
line between aorta and pulmonary trunk
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Does the trachea go into inferior mediastinum?
no, because it splits before
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