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49 Cards in this Set

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Define mediastinum.
Th anitomic region located between the lungs describes as a partition seperating two pleural cavities.
What is the sternal angle? What divisions does it divide the mediastinum into?
The sternal angle is above the sternum and aligns with disc T4-5 it also divides the mediastinum into superior/inferior.
What is the importance of the mediastinum? What organs does it contain?
The mediastinum serves as a corridor through which structures from the head and neck region connect with lower regions of the body and vice versa. It contains all the principal tissues and organs of the the chest except the lungs.
What are the boundaries of the mediastinum?
It extends from the sternum back to the vertebral column and is bounded laterally by the pericardium, the membrane enclosing the heart, adn the mediastinal pleurae, membranes that are continuous with those lining the thoracic cavity.
What are some of the specific structures of the mediastinum?
It contains the heart, thymus gland, portions of esophagus and trachea and other structures.
What are the compartments of the mediastinum?
Superior Mediastinal Compartment and
Inferior Mediastinal Compartment:
Consists of Anterior, Middle and Posterior Compartments.
Where is the superior mediastinum located? What is its posterior boundary? What structure is it continuous with superiorly? What structure is it continuous with inferiorly? What is it bound by laterally?
THe superior mediastinum is located above the manubriosternal angle. Its posterior boundary is made up of the first four thoracic vertebrae. Above it is continuous with the neck. Below it is continuous with both anterior and posterior mediastina. Laterally it is limited by parietal (mediastinal) pleura.
What are the contents of the superior mediastinum? (9) Also name the branches when needed.
Structure
-Thymus
-Aorta (arch): Brachiocephalic trunk, left common carotid artery, left subclavian artery
-Superior Vena Cava: Left and right brachiocephalic veins
-Trachea: Left and Right bronchi
-Esophagus
-Right vagus nerve
-left vagus nerve: left recurrent laryngeal nerve
-Phrenic nerves
-Thoracic duct
What is the anterior mediastinal compartment bound by anteriorly and posteriorly? What does this compartment contain?
The antioror mediastinal compartment is bordered by the sternum anteriorly and the pericardial sac posteriorly. The compartment contains the sternopericardial ligament, fat and lymph nodes.
What are the ventral and dorsal borders of the middle mediastinum? What structures are in the middle mediastinal compartment?
The ventral border is the anterior mediastinal compartment. The dorsal border is the posterior mediastinum. Structures in the middle mediastinum include the pericardium, heart, phrenic nerves, pericardioacophrenic vessels, stems of great vessels.
What are the anterior and posterior borders of the posterior mediastinal compartment? What structures are found in it (7)?
It is bound anteriorly by the pericardial sac and posteriorly by the anterior surface of the vertebral bodies.
In the posterior mediastinal compartment there is the descending aorta, esophagus, azygous system of veins, vagus nerve, thoracic duct, lymph nodes, thoracic splanchnic nerves.
What is the thymus? Where is it located? What structure is it posterior to? Where does it extend into?
The thymus is a primary lymphoid organ. It is located in the lower part of the neck and the anterior part of the supeior mediastinum. It lies posterior to the manubriu mand extends into the anterior mediastinum.
How long does the thymus continue to grow for? When does it stop growing and what is it replaced by? What is the blood supply, innervation, and function?
The thymus continues to grow untill age 5-6. After puberty it is largely replaced by fat. Its blood supply is the inferior thyroid and internal thoracic.
Its innervation is branches from the vagus and sympathetic trunk.
Its function is development and maintenence of the immune system.
What is the anterior mediastinal compartment bound by anteriorly and posteriorly? What does this compartment contain?
The antioror mediastinal compartment is bordered by the sternum anteriorly and the pericardial sac posteriorly. The compartment contains the sternopericardial ligament, fat and lymph nodes.
What are the contents of the superior mediastinum? (9) Also name the branches when needed.
Structure
-Thymus
-Aorta (arch): Brachiocephalic trunk, left common carotid artery, left subclavian artery
-Superior Vena Cava: Left and right brachiocephalic veins
-Trachea: Left and Right bronchi
-Esophagus
-Right vagus nerve
-left vagus nerve: left recurrent laryngeal nerve
-Phrenic nerves
-Thoracic duct
Describe the aorta.
Where is the ascending aorta?
Where is the aortic arch?
Where/what is the descending portion of the aorta?
The ascending aorta goes from the left ventricle to the aortic arch and is mostly within the pericardial sac.
The aortic arch is above the plane of the manubriosternal angle and courses posteriorly and laterally (in superior mediastinum)
The descending aorta is a continuation of the arch on the left side of the vertebrae and coures downward towards the midline. It reaches the midline at T12 as it passes through the diaphragm.
Where is the pulmonary trunk and pulmonary arteries? When does the pulmonary trunk divide into the left and right pulmonary arteries?
Where is the right/left posterior arteries in relation to the ascending/descending aorta? What is the ligamentum arteriosum? Why is it important?
The pulmonary trunk courses upwards and to the left. IT divides into the left and right arteries in the concavity of the aortic arch.
The right pulmonary artery is posterior to the ascending aorta.
The left pulmonary artery is anterior to the descending aorta.
The ligamentum artiosum is important for the location of the vagus nerve.
What is genral rule for veins in relation to arteries?
Generally veins are in plane anterior to arteries.
What is the general rule of veins of the thorax in relation to arteries?
Generally veins are in plane anterior to arteries.
Where is the inferior vena cava? How does it approach the heart?
The inferior vena cava pierces the diaphragm at T8 and immediately enters the pericardium and heart.
Where is the left brachiocephalic vein? What confluence is it formed by? What is its course in relation to the great arteries? What vein does it join and where does it do this?
The left brachiocephalic vein is formed by the confluence of internal jugular and subclavian. It courses obliquely to the right in front of the great arteries. It joins the right brachiocephalic vein behind intercostal space 1.
Where is the right brachiocephalic vein? What confluence is it formed by? What structure does it course vertically behind? With what vein does it join to form what large vein?
The right brachiocephalic vein is formed via the confluence of internal jugular and the subclavian. It courses vertically behind the manubrium and joins the left bc vein to form the superior vena cava.
Where is the superior vena cava formed? How does it course in relation to the right atrium? What important vein does it recieve?
The superior vena gcava is formed behind intercostal space 1 by two brachiocephalics and courses vetically to the right atrium. It recieves the azygous vein.
Where do the pulmonary veins arise and where do they go?
The pulmonary veins arise directly from the root of the lung and lead to the left atrium.
What is the function of the thoracic duct? What chamber of the mediastinum is it located in? What are the 3 branches of it and what do they drain?
The thoracic duct drains all of the body below the diaphragma and left side thorax. It is located in the posterior mediastinum.
The right lymphatic duct has 3 branches:
1)Right jugular- drains the right side of head and neck
2)Subclavian- drains right upper limb
3)bronchomediastinal- drains the right side of the thorax
What is the cisterna chyli? Where does the thoracic duct go as it ascends (what structure does it go through and what does it ascend between)? What plane does it stop ascending? What structure does it join and what do these structures lie directly behind?
The cisterna chyli is a dilation of the origin of the thoracic duct (abdomen) it ascends through the aortic hiatus of the diaphragm and ascends between the azygous vein and aorta to the T4-5 plane. It crosses to the left at T4-5 to ascend behind the esophagus into the neck. It joins the confluence of the internal jugular and subclavian veins.
What is the shape of the tracheal tubes? What compartment of the mediastinum is it located in? From where to where does the trachea course?
The trachea is located in the superior mediastinum and is formed by D-shaped tubes supported by cartilage. The trachea courses from larynx to bifurcation.
Where does the bifurcation of the trachea take place? What is anterior and posterior to the trachea? What is to the right/left of the bifurcation?
The bifurcation takes place at T4-5. Anteriorly there are the great vessels and the thymus. Posteriorly there is the esophagus. The azygous vein is to the right of the bifurcation. The aortic arch is to the left of the bifurcation.
What divides the bronchi? What is the left bronchus anterior to? What is the right bronchus inferior to? What is the blood supply of the trachea (2)? What is the inervation of the trachea (3)?
The carina divides the bronchi. The bronchioles are in the posterior mediastinum. The left bronchus is anterior to the aorta. The right bronchus is inferior to the azygous arch. The blood supply of the trachea is the bronchial arteries and the inferior thyroid arteries. The innervation is the pulmonary plexus and branches of the vagus and sympathetic trunk.
What mediastinum compartments does the esophagus course through? What is it continuous superiorly with in the neck? Where does it pierce the diaphragm and what structure does it join? What pushes the esophagus toward the midline?
The esophagus courses through superior and posterior mediastinum. It is continuous superiorly with the pharynx in neck and pierces the diaphragm at T10 to join the stomach. The upper portion is in the thorax and is slightly left of the midline. At the lower end it passes through the diaphragm to the left of the midline. It is pushed toward the midline by the aortic arch.
What type of muscle is in the upper/middle/lower third of the esophagus?
Striated muscle in neck.
Smooth muscle in lower third.
Mixed in middle.
What courses anteriorly to the esophagus?
The trachea the left bronchus crosses it and the pericardium (left atrium).
What courses posteriorly to the esophagus?
The vertebral bodies, thoracic duct, azygous system and intercostal aa.
What courses to the left and right of the esophagus?
The right is associated with the terminal azygos and the left is crossed by the aortic arch.
What are the constrictions of the esophagus (3)?
The constrictions are at the superior end in the neck, where the aorta and left bronchus compress it and at near the gastric end.
What are the arteries that supply the esophagus?
The arteries that supply it are the esophageal branches of the thoracic aorta. These anastamose with the inferior thyroid arteries and left gastric arteries.
What veins serve the esophagus and where do they drain superiorly and inferiorly?
The submucosal and surface plexus are the veins that drain the esophagus. They go to the azygos system and may drain superiorly to the inferior thyroid veisn and may drain inferiorly to the gastric vein (portal caval)
What is the inervation of the esophagus (3 distinct categories)?
Straited muscle: vagal (recurrent branch)
Smooth muscle: parasympathetic vagal
Esophageal plexus: surrounds the lower thoracic esophagus and is mostly vagal fibers and some sympathetic.
What is the phrenic nerve always accompanied by? What does its motor fibers innervate? What does its sensory fibers innervate?
The phrenic nerve always is accompanied by pericardial vessels. It sends motor fibers to all of the diaphragm (C3-C5). It is sensory to the parietal pleura, the pericardium and the central diaphragm.
Describe the course of the right phrenic nerve.
IT descends along the right side of the great veins (right brachiocephalic vein, s. vena cava, right atrium, inferior vena cava, anterior to root of lung.
Describe the course of the left phrenic nerve.
It courses along the left side of the subclavian artery and crosses the left side of th aortic arch anterior to root of lung. It is along the left side of the pericardial sac.
Describe the vagus nerve (what is it made of and where is it going).
The preganglionic parasympathetic fibers for thoracic and abdominal viscera. It spits into left and right vagus.
Describe the course of the right vagus.
The right vagus enters the thorax posterolateral to brachiocephalic v. anterior to rt. subclavian artery. The right recurrent branch hooks under the subcavian artery to ascend near the trachea and esophagus. It descends to the lateral side of the trachea posterior to root of the lung. It descends on the posterior esophagus to form the plexus. It passes through the diaphragm with esophagus as the posterior vagal trunk.
Describe the course of the left vagus. Also give the branches of the vagus in the thorax (4).
The left vagus enters the thorax between the carotid and subclavian arteries. It descends to cross the left side of the aortic arch. The recurrent branch recurves around the ligamentum arteriosum to ascend in neck between trachea and esophagus. It then goes behind the root of the lung and onto the anterior esophagus - forms plexus and through the diaphragm with esophagus as the anterior vagal trunk.

The branches of the vagus in the thorax include the left recurrent laryngeal, the br. to pulmonary plexus, the br. to esophagus and br. to cardiac plexus.
Describe what the azygos system does and what are the 3 parts of it.
The azygos system of veins draisn the intercostal veins and some lumbar segmental veins. It includes the azygos vein, the hemiazygos vein, and the accessory hemiazygos vein.
What is the azygos formed by (2 veins)? Describe the path of the azygos. What are its tributaries?
The azygos vein is formed by the union of the right ascending lumbar vein and the right subcostal vein. It ascends along the right side of the vertebral column to T4 and is supervisial to the intercostal aa. with the thoracic duct to the left. It arches over the bronchus to join the superior vena cava.
Its tributaries include:
r. posterior intercostal vv. - 5-11
r. superior intercostal v. - drains ICS 2-4
hemiazygous v.
accessory hemiazygous v.
esophageal, mediastinal, pericardial, bronchial veins
What is the hemiazygous formed by? What is its course? What are its tributaries?
The hemiazygos is formed by a union similar to the azygous. It ascends left of the vertebral column. It crosses over to join azygous at T8-T9. It is posterior to aorta and esophagus.
Its tributaries include the left posteriro intercostal veins 7-11, esophageal, mediastinal, and pericardial veins.
What is the accessory hemiazygous vein? What intercostals form it? Where is its location with respect to the vertebral column? Where does it join the azygous?
The accessory hemiazygous vein is formed by posterior intercostals 4-8, it is left of the vertebral column and crosses to join the azygous at T8.
What is the left superior intercostal vein formed by? Where does it drain to?
The left superior intercostal vein is formed by the upper posterior intercostal veisn and draisn to left brachiocephalic vein.