Thoracic Cavity 1 Flashcards
What is contained in the thoracic cavity?
lungs and chest wall lined by pleura
heart covered with pericardium
What lines body cavities?
serous membrane
What is the function of serous membrane?
- allows movement, expansion and contraction of organs
- compartmentalisation
- layer of fluid to allow frictionless movement
Where is the superior mediastinum found?
behind the manubrium, between the thoracic inlet and the plane through the sternal angle (T4/5 intervertebral disc level)
Where is the inferior mediastinum found?
inferior to the transverse plane through the sternal angle and the diaphragm
subdivided into anterior, middle and posterior mediastinum
Relations of the right side of the mediastinum
- right atrium and veins
- superior vena cava
- arch of the azygos
- inferior vena cava
Relations of the left side of the mediastinum
- left ventricle and arteries
- left common carotid artery
- left subclavian artery
- arch of aorta
- thoracic aorta
What is contained in the middle mediastinum?
- heart
- pericardium
- origins of great vessels (aorta pulmonary trunk)
- terminal parts of IVC and SVC
- phrenic nerves
- branches of vagus
What are the functions and the different layers of the pericardium?
- anchors the heart and prevents overexpansion of the heart
- 2 layers:
- fibrous pericardium externally
- serous pericardium internally
Relations and attachments of the fibrous pericardium
- anteriorly related and attached by the sterno-pericardial ligament to the body of sternum and 3rd-6th CC
- posteriorly related and attached by the pericardiovertebral ligaments to 5th-8th thoracic vertebrae
- inferiorly blends with the central tendon of the diaphragm by the pericardiophrenic ligament
What does the attachment of fibrous pericardium to the diaphragm do?
Stops the diaphragm from everting the ribs medially reducing the pressure on them
Explain the composition of serous pericardium
- 2 layers, parietal and visceral
- parietal: lines inner aspect of fibrous pericardium and reflects on itself around roots of great vessels to continue as the visceral layer
- visceral layer: epicardium
Where is the pericardial cavity found?
between parietal and visceral layers of serous pericardium
What is the purpose of the transverse pericardial sinus?
to separate the arterial and venous ends of the heart tube
Describe the position and relations of the transverse pericardial sinus
posterior to the ascending aorta and pulmonary trunk, anterior to the superior vena cava
superior to the left atrium and pulmonary veins
What is the importance of the transverse pericardial sinus?
Important in cardiac surgery. A finger can make a ligature through the sinus to stop circulation
Other name for transverse pericardial sinus
sinus of Theile
Other name for oblique pericardial sinus
Haller’s cul-de-sac
Describe the relations of the oblique pericardial sinus
surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the IVC
What is the nerve supply to the pericardium?
- sensory fibres from phrenic nerve
- parasympathetic vasomotor fibres from the vagus nerve
- sympathetic cardiopulmonary vasomotor fibres from cardiopulmonary splanchnic nerves
Describe the journey of the phrenic nerve
Arises from ventral rami of C3,4,5 (mainly 4) and travels over the scalenus anterior muscle and enters mediastinum between venous and arterial planes (subclavian artery and vein) between the fibrous pericardium and parietal pleura
What is an identifiable feature of the phrenic nerve?
It passes anterior to the root of the lung
Where does the right phrenic nerve pass?
adjacent to the SVC then IVC and through the caval opening to enter the diaphragm
Where does the left phrenic nerve pass?
crosses the aortic arch and over the left ventricle and pierces diaphragm
