Organization of the thorax: Wilson Flashcards
The sternal angle is an important landmark for what?
- manubriosternal joint
- 2nd rib
- vertebral level T4-T5
The thorax can be divided into what 3 cavities?
- left and right pleural cavities holding the lungs
- the mediastinum holding the heart
What is the superior boundary of the mediastinum?
superior thoracic aperture
What is the inferior boundary of the mediastinum?
inferior thoracic aperture whose space is bounded by the diaphragm
What is the anterior boundary of the mediastinum?
sternum
What is the posterior boundary of the mediastinum?
thoracic vertebrae
What is the lateral boundary of the mediastinum?
pleura
A line running from the sternal angle to T4-5 divides the mediastinum into what?
superior and inferior mediastinum
What further divides the inferior mediastinum into the anterior, posterior, and middle mediastinum?
pericardial sac
How does the mediastinal viscera position shift from a supine to standing position?
the heart is located more inferiorly when standing than when in supine position
Where is the location of the thymus in relation to the sternum?
thymus is found immediately beneath the sternum
In the adult , the thymus gland usually undergoes what process?
involution to fat
histologically, fragments of thymus remain within the fat throughout life
What are the great veins that are found in the superior mediastinum?
left and right brachiocephalic vein that come together to form the superior vena cava
Which part of the mediastinum is the superior vena cava located in?
superior vena cava is located primarily in the superior mediastinum with its distal portion located in the middle mediastinum
What arteries are located in the superior mediastinum?
arch of the aorta
What are the direct branches of the arch of the aorta?
- brachiocephalic trunk (which will branch into right subclavian and right common carotid artery)
- left common carotid artery
- left subclavian artery
What nerve runs along the lateral border of the superior vena cava?
phrenic nerve
What nerve passes posterior to the ligamentum arteriosum and provides innervation to the esophagus, trachea, and larynx?
left recurrent laryngeal nerve which is a branch of the left vagus nerve
What is the embryological form of the ligamentum arteriosum?
ductus arteriosus
Explain how dysphonia be a sign of an aortic aneurysm.
The left recurrent laryngeal nerve passes posterior to the ligamentum arteriosum which is in between the aortic arch and left pulmonary artery. The enlarged aortic arch could compress this nerve which provides innervation to the larynx.
What does the right recurrent laryngeal nerve wrap around before ascending to innervate the larynx?
the right subclavian artery
Why are the courses of the left and right recurrent laryngeal nerve different in the adult?
because they have differential development of the right and left 4th aortic arches
Where does the trachea bifurcate? Which portion of the mediastinum is it located in?
- bifurcates at the sternal angle
- thus the bronchi are not in the mediastinum
What is the importance of the carina of the trachea?
- carina is a wedged shaped cartilage on the inside of the trachea that is lined with mucous membrane and has an abundant supply of sensory nerve fibers that are sensitive to irritation
- if you aspirate you evoke a violent cough reflex due to the stimulation of these sensory nerve fibers in the carina
What drainage does the inferior bronchiotracheal (carinal) lymph nodes receive? How is this significant clinically?
- receives lymphatic drainage from both the left and right lungs
- biopsies of these carinal nodes are done to test for lung cancer metastases
What is found directly posterior to the trachea?
esophagus
What vessel can provide an important anastomotic group if the right subclavian vein is damaged?
- azygos vein which is right sided
- blood can bypass the right subclavian vein obstruction and return to the heart
Where does the azygos vein drain into?
superior vena cava
What does the azygos vein drain?
drains the posterior abdominal/thoracic wall
Where does the azygos vein run on top of and where does it begin and terminate?
- usually runs on top of vertebral column
- begins in the abdomen
- terminates into the superior vena cava
What ascends through the superior mediastinum and terminates at the junction of the left subclavian and internal jugular veins?
thoracic duct which is the LARGEST lymphatic duct in the body
Which mediastinum is found in between the body of the sternum and the pericardial sac?
anterior mediastinum
The phrenic nerve is located within which mediastinum?
middle mediastinum
-phrenic nerves run along the lateral borders of the pericardial sac
What forms the border of the middle mediastinum?
pericardial sac
What provides sensory innervation to the pericardium and diaphragm?
phrenic nerve
What artery and vein is found in the anterior mediastinum? What do they supply and drain?
- internal thoracic artery and vein
- they supply and drain the breast (axillary vein is the primary drainer) and is used in the bypass surgery (angioplasty)
Where does the phrenic nerve originate? Where would pain be referred to on the body if there is irritation of the pericardium or the diaphragm?
- phrenic nerve originates from spinal nerves C3, C4, and C5
- referred pain in the shoulders and neck region
The heart is located in which mediastinum?
middle mediastinum
What are the contents of the middle mediastinum?
- heart
- ascending aorta
- pulmonary trunk (proximal)
- superior vena cava (termination)
From an anterior anatomical view, which portion of the heart is mainly seen?
right ventricle
-only a portion of the right atrium and left ventricle are seen laterally
Normally which part of the heart is never seen from an anterior view?
left atrium
How can an enlarged left atrium cause difficulty swallowing?
the enlarged atrium can displace the esophagus by bending it, making swallowing more difficult
Which mediastinum is located in the space between the pericardial sac and vertebral column?
posterior mediastinum
The azygos vein and thoracic duct are located in which mediastinum?
posterior mediastinum
T/F. Pulmonary vein is part of the middle mediastinum.
True
Which part of the aorta is located in the posterior mediastinum?
descending aorta
What are the 5 major contents of the posterior mediastinum?
- descending aorta
- esophagus
- esophageal plexus (consists of right and left CN X)
- thoracic duct
- azygos vein
What is the continuation of the aortic arch that crosses into the inferior mediastinum?
descending aorta
What does the descending aorta exit the thorax through and at what vertebral level?
exits the thorax through the aortic hiatus in the diaphragm at T12
What are the 3 branches of the descending aorta?
- bronchial artery
- posterior intercostal artery
- esophageal artery
When passing instruments into the stomach, what are the potential sites of the esophagus that can be perforated?
the four constrictors
Where are the four constrictors of the esophagus located?
- begins in the neck at C6
- crosses the arch of aorta
- is crossed by the left bronchus
- exits the thorax at the esophageal hiatus in the diaphragm at T10
What nerves anastomose to form the esophageal plexus?
the right and left vagus nerves
What two nerves are formed by the esophageal plexus as the esophagus pierces the diaphragm and enters the abdomen?
- anterior gastric nerve
- posterior gastric nerve
The anterior and posterior nerves come from which vagus nerves?
- anterior gastric nerve (left CN X)
- posterior gastric nerve (right CN X)
What is the largest lymph vessel in the body?
thoracic duct
The greater splanchnic nerve is a branch of what and is found at what vertebral levels?
- branch of the sympathetic chain
- vertebral levels T5-9
What two vessels does the thoracic duct run in between?
azygos vein and the aorta
The greater greater splanchnic nerve is found within which mediastinum?
posterior mediastinum
