Mediastinum Flashcards
What is mediastinum?
the medial compartment of the thoracic cavity.
It is mobile in the chest e.g., heart needs to contract
Contains all of the thoracic viscera other than the lungs.
Mediastinum is divided into two main compartments for diagnostic purposes by transverse thoracic plane (T4)
- Superior
- Inferior (forms anterior, middle, posterior compartments)
What is in the superior mediastinum?
- Great vessels: Veins (brachiocephalic veins and SVC) are anterior to the arteries (arch of the aorta and the roots of its major branches—the brachiocephalic trunk, left common carotid artery, and left subclavian artery)
- Related nerves (vagus and phrenic nerves and the cardiac plexus of nerves).
- Trachea, esophagus and related nerves (left recurrent laryngeal nerve).
-Thoracic duct and lymphatic trunks.
Part of the the thymus
What is in the posterior mediastinum?
- Thoracic aorta
- Thoracic duct
- Lymphatic trunks
- Posterior mediastinal lymph nodes
- Azygos and hemiazygos veins
- Esophagus and esophageal nerve plexus
What is in the anterior mediastinum?
- Smallest subdivision
- Loose connective tissue
- Fat
- Lymphatic vessels and a few lymph nodes
- Branches of the internal thoracic vessels
- In infants and children, the anterior mediastinum contains the inferior part of the thymus.
What is in the middle mediastinum?
Pericardium = fibroserous membrane that covers the heart and the beginning of its great vessels
Pericardial cavity: the potential parietal and visceral layers of serous pericardium. Contains a thin film of fluid that enables the heart to move and beat in a frictionless environment.
What is the clinical significance of the pericardium?
Pericardial effusion: Passage of fluid from pericardial capillaries or pus into the pericardial cavity. Caused by some inflammatory diseases.
Cardiac tamponade: because the fibrous pericardium is so tough an inelastic, extensive pericardial effusion will compress the heart rather than expand the pericardium. Can be relieved via pericardiocentesis (right)
What are mediastinal lymphatics?
Mediastinal lymph nodes –> tracheobronchial lymph nodes
Mediastinal lymph nodes are found in front of the aorta and alongside it.
Tracheobronchial nodes are located at the bifurcation of the trachea and collect the lymph from the lungs and the heart
What are the position of the lungs in the thorax?
- Posteriorly, lungs reach below the 9th pair of ribs – the pleura reaches even further, into the costodiaphragmatic recess, below the 11th pair of ribs
- Anteriorly, lungs reach to about the 6th pair of ribs, the pleura to the 7th rib pair
What is the lung surface anatomy?
Right lung has 3 lobes, left lung only 2.
Right lung has horizontal and oblique fissure. Left lung only has oblique fissure
Root of the lung: contains the blood vessels and bronchi entering and leaving the lungs on their mediastinal surface as well as lymph nodes and neural structures
Explain the trachea and the lower airways
-On the posterior aspect, the trachea and airways consist of smooth muscle (trachealis)
Branching pattern: Trachea->Primary Bronchi->Lobar Bronchi->Segmental Brochi->bronchioles
Note that the right main bronchus is wider, shorter, and more vertical than left main bronchus. Foreign material (e.g., a foreign body or food) is more likely to enter and lodge in right side
Lung Organisation Bronchopulmonary Segments
- Lung diseases can be compartmentalised in segments
- Surgically, bronchopulmonary segments can be resected without compromising the function of the rest of the lungs
- Different segments have different susceptibility to be flooded by fluids in horizontal or vertical posture
What is COPD?
inflammatory lung disease that causing obstructed airflow from the lungs
Emphysema and chronic bronchitis
What are the pleural reflections of the pulmonary cavities?
There are 3 lines of pleural reflectionon each side of the pulmonary cavities:
- sternal
- costal
- vertebral
