Lecture 8 RH Flashcards
What is the mediastinum?
Mediastinum is an area in the thoracic cage in the center of the thoracic cavity. It contains the space between the lungs.
What are the sections of the mediastinum? What separates them?
superior mediastinum
inferior mediastinum
They are separated by the plane of louis. (At the manubriosternal joint)
What happens at the plane of louis and what are some structures present nearby?
between T4 and T5
It is the point where the great vessels leave the heart.
It is the point where the Main bronchi bifurcate.
What are the postero anterior sections of the mediastinum?
heart is at the middle mediastinum.
Anteriorly is the thoracic cage and the pericardium.
Posteriorly is the descending aorta and all the structures behind the heart directly.
Where is the thymus located?
immediately deep to the manubrium is the thymus..
what is the function of the thymus?
Thymus is important for the development of the immune system. It is lost during puberty due to redundancy.
What are the branches of the superior vena cava?
Superior vena cava forms 2 branches; the right and left brachiocephalic veins.
What are the branches of the left and right brachiocephalic veins?
right brachiocephalic vein forms the right subclavian and right internal jugular vein.
Left does the same with left subclavian and internal jugular.
What are the branches of the aortic arch?
Brachiocephalic artery to the right.
Left common carotid
Left subclavian artery
What does the aorta arch over?
Posteriorly to the left over the left pulmonary trunk and the left main bronchus before descending into the posterior inferior mediastinum.
What is the purpose of the brachiocephalic trunk?
forms a bridge between the aortic arch and the right subclavian + right common carotid.
What are the first branches of the aorta?
The coronary arteries.
What are the main nerves that innervate the heart?
Right and left vagus nerves
Right and left phrenic nerves
Right and left recurring laryngeal nerves. (these nerves come of the vagus nerves and curl under the left side of the aortic arch and goes back up to the larynx)
What is the purpose of the recurrant laryngeal nerves?
For phonation
What structure is the left recurrant laryngeal nerve really close to?
The ligamentum artereosum.
What is the clinical significance of the location of the left recurrant (recurrent you daft cunt) laryngeal nerve?
Cardiosurgeons repairing a patent ductus artereosus could potentially accidentally constrict the nerve causing phonation problems.
What are the structures found in the superior mediastinum?
oesophagus
trachea
Thoracic duct (drains lymph from below diaphragm into the left brachiocephalic vein)
Where does the thoracic duct drain into?
Brachiocephalic vein
What can be found in the anterior mediastinum?
Fat
Lymph nodes
Internal thoracic vessels
Inferior part of thymus (in children)
What can be found in the middle mediastinum?
Superior vena cava
Phrenic nerve
Heart
Pulmonary trunk
Ascending aorta
What structures can be found in the posterior mediastinum?
Thoracic duct
Right and left vagus nerve (running behind the main bronchi)
oesophagus (moves off towards the left)
descending thoracic aorta
Where is the descending aorta relative to the oesophagus in the posterior mediastinum?
lateral and posterior.(remember that aorta goes behind the diaphragm whereas the oesophagus goes through muscular part of the diaphragm right crus slings around the oesophagus to form functional sphincter)
Where does the thoracic duct run within the mediastinum?
Directly anterior to the vertebra and posteriorly to the aorta. (this structure is very hard to find)
What level does the aorta pierce the diaphragm?
T12
What structures does the descending aorta supply?
descending aorta supplies most abdominal viscera and the thoracic walls. It gives off the posterior intercostal arteries which anastomose with anterior intercostal arteries derived from the internal thoracic arteries.
Bronchial arteries supply non-respiratory parts of the lungs and bronchi. They are derived from descending aorta
oesophagus is supplied directly by the oesophageal branches of the descending aorta.
Where are anterior intercostal arteries derived from?
From the internal thoracic arteries
Where are the internal thoracic arteries derived from?
From the subclavian arteries.
What is the function of bronchial arteries?
bronchial arteries supply non-respiratory parts of the lungs and bronchi. They are derived from descending aorta
Where does the oesophagus derive its blood supply?
oesophagus is supplied directly by the oesophageal branches of the descending aorta.
What are the layers of the oesophagus?
3 layers of muscle; circular, longitudinal, then circular.
What is the shape of the oesophageal tube?
oesophagus is flattened in an anteroposterior direction.
What veins drain the oesophagus?
The azygous system of veins.
What nerves supply the oesophagus?
Sympathetic nerves
vagus sends branches in for parasympathetic innervation.
Autonomous nervous system form mixture of nerves known as plexuses.
What is the path that the thoracic duct takes in?
Thoracic duct as it ascends at around plane of louie it moves off to the left side and descends to the left brachiocephalic vein.
What does the thoracic duct drain?
Below the diaphragm and the left upper limb.
What is the cysterna chyli?
A swollen structure that appears in the thoracic duct in rare cases.
How do the lungs drain into the thoracic duct?
lymphatic drainage of the left lung drains via the bronchomediastinal trunk into the left thoracic duct.
Right lung goes into right lymphatic duct into the right brachiocephalic vein. This right lymphatic duct drains the right upper limb as well.
Where does the right lymphatic duct drain?
The right upper limb and right lung.
What is the function of the azygous system?
azygous veins are on posterior wall of thorax and they drain the whole thorax and return it into the superior vena cava
What side does the azygous vein run along?
The right of the vertebral column it loops around the right main bronchus.
What do the intercostal veins drain into?
upper posterior drain into accessory azygous veins
Lower posterior intercostal veins drain into the hemizygous vein.
What do the accessory and hemiazygous veins drain into?
into the azygous veins. (at about T9 lots of variability)
What can be said about the variability of the azygous vein?
Huge variability in the way the azygous system looks.
Where can the azygous vein drain into to reach the heart?
azygous vein can communicate at the inferior vena cava below the level of the diaphragm.
It loops around the right main bronchus into the superior vena cava.
