Respiratory System 5: Mediastinum Flashcards
What is the mediastinum?
It is the central compartment of the thoracic cavity, sandwiched between the left and right pulmonary cavities, containing all thoracic viscera and structures except the lungs.
What are the boundaries of the mediastinum?
It is covered on each side by the mediastinal pleura.
What forms the superior boundary of the mediastinum?
The superior thoracic aperture.
What structure forms the inferior boundary of the mediastinum?
The diaphragm.
What structure forms the anterior boundary of the mediastinum?
The sternum.
What forms the posterior boundary of the mediastinum?
The vertebral bodies of T1 to T12.
What forms the lateral boundaries of the mediastinum?
The mediastinal pleura on the left and right sides.
How is the mediastinum positioned within the thoracic cavity?
It is centrally located, extending from the sternum anteriorly to the vertebral bodies posteriorly and bounded laterally by the lungs.
How is the mediastinum divided for descriptive purposes?
It is divided into superior and inferior parts.
What separates the superior and inferior mediastinum?
An imaginary transverse plane at the level of the sternal angle (also known as the transverse thoracic plane).
How is the inferior mediastinum further subdivided?
3 parts: Into anterior, middle, and posterior parts.
What lies in the anterior part of the inferior mediastinum?
The space between the sternum and the pericardium.
What is contained in the middle part of the inferior mediastinum?
The pericardium, the heart, and the roots of the great vessels.
What structures are found in the posterior part of the inferior mediastinum?
The space between the pericardium and the bodies of T5-T12 vertebral bodies.
What anatomical landmark is used to define the transverse thoracic plane?
The sternal angle.
Where is the superior mediastinum located?
It lies between the manubrium and the upper four thoracic vertebrae.
What are the structures found in the superior mediastinum from anterior to posterior?
- Thymus
- Great vessels (brachiocephalic veins and SVC) anterior to the arteries (arch of aorta and roots of its major branches)
- Vagus and phrenic nerves
- Inferior continuation of trachea and esophagus, including the left recurrent laryngeal nerve
- Thoracic duct and lymphatic trunks
What great veins are located in the superior mediastinum?
The brachiocephalic veins and the superior vena cava (SVC).
What major arteries are found in the superior mediastinum?
The arch of the aorta and its major branches.
Where is the anterior mediastinum located?
It lies between the sternum and the pericardium.
What type of tissue is commonly found in the anterior mediastinum?
A variable quantity of fat.
What is the role of the thymus in the anterior mediastinum during childhood?
The thymus lobes are located in the superior and anterior mediastinum, enlarging to reach their greatest size at puberty and regressing with age.
What structures are found in the anterior mediastinum?
Sternopericardial ligaments (extremely variable and often not detectable)
Some lymph nodes
Branches of the internal thoracic vessels.
Where is the middle mediastinum located?
It is bounded by the pericardium and contains everything deep to it, including the roots of the great vessels.
What major structures are contained in the middle mediastinum?
- The pericardium, the heart, and the ascending aorta
- The lower half of the superior vena cava (SVC), receiving the azygos vein (the arch)
- The pulmonary trunk and the left and right pulmonary arteries and veins
- The phrenic nerves (running anterior to the roots of the lungs).