Mediastinum Flashcards
What is the mediastinum
Part of the thoracic cavity which lies between the lungs
What does the mediastinum contain
All thoracic viscera apart from the lungs
Heart and pericardium
Great vessels that enter and leave the heart
Veins that drain the chest wall
Trachea and main bronchi
Oesophagus
Nerves (somatic and autonomic)
Lymphatics
Thymus gland
What is the pericardium
Fibrous sac around the heart
What is the mediastinum divided into
Superior and inferior compartments
Where does the line between the compartments of the mediastinum run
Sternal angle anteriorly to the T4/T5 junction posteriorly
What is the inferior mediastinum divided into
Anterior compartments
Middle compartments
Posterior compartments
Where is the anterior mediastinum
Lies between the posterior aspect of the sternum and the anterior aspect of the pericardial sac
What is the anterior mediastinum
Narrow space that contains the thymus gland in children and remnant in adults
What does the middle mediastinum contain
Heart inside the pericardial sac
The pulmonary trunk
Ascending aorta
Where is the posterior mediastinum
Lies between the posterior aspect of the pericardial sac and the vertebrae
What are the main components of the superior mediastinum
Arch of the aorta and its three branches
Superior vena cava and its tributaries - the left and right brachiocephalic veins
Trachea
Oesophagus
Phrenic nerves (left and right)
Vagus nerves (left and right)
Thoracic duct
Thymus gland
What does the ascending aorta give rise to
Coronary arteries which supply the myocardium
Where does the arch of the aorta lie
Superior mediastinum
Where does the descending (thoracic) aorta descend
Posterior mediastinum
Into the abdomen posterior to diaphragm
What does the right common carotid artery supply
Right side of the head and neck including the brain
What does the right subclavian supply
Right upper limb
What does the left common carotid artery supply
Left side of the head, neck and brain
What does the left subclavian artery supply
Left upper limb
What does the arch of the aorta contain
Aortic bodies where chemoreceptors are located
What do chemoreceptors monitor
Arterial oxygen and carbon dioxide
Where does chemoreceptors information travel
Visceral sensory information travels back to CNS along the path of the vagus nerve
What is the ligamentum arteriosum
Fibrous, cord-like connection between the pulmonary trunk and the arch of the aorta
In the placenta what does the ductus arteriosus do
Diverts most of the blood entering the pulmonary trunk directly to the aortic arch
Where does the superior vena cava return blood from
From the neck, head, and upper limbs
Where does the superior vena cava and its tributaries lie
Superior mediastinum
What does the internal jugular vein drain
Head and neck
What does the subclavian vein drain
Upper limb
What forms each brachiocephalic vein
Internal jugular vein
Subclavian vein
Where does the inferior vena cava return blood from
All regions inferior to the diaphragm (abdomen, pelvis and lower limbs)
How long is the thoracic part of the IVC
Very short
What is the shape of the trachea
Semi-rigid due to C-shape incomplete rings of cartilage in its walls
Where is the trachea palpable
Just superior to the suprasternal notch
Where does the trachea extend
Larynx in the midline of the neck into the superior mediastinum
Where does the trachea terminate
At the level of the sternal angle (and junction between T4 and T5 vertebrae) by bifurcating into the left and right main bronchi
What is the oesophagus
Muscular tube
Where is the oesophagus
Extends from the pharynx in the midline of the neck to the stomach
How does the oesophagus work
Waves of contractions of smooth muscle in the oesophageal wall move swallowed food and fluid distally (peristalsis)
Where does the oesophagus lie in the superior mediastinum
Lies in the midline of the thorax, posterior to the trachea
What are the right and left phrenic nerves formed by
C3, C4, C5 spinal nerves
What innervates the diaphragm
Right and left phrenic nerves
What are the phrenic nerves
Somatic nerves
Contain motor and sensory fibres
Where do the left and right phrenic nerves descend
Descend through the neck
Where do the left and right phrenic nerves enter the thorax
Through the superior thoracic aperture
What is the thoracic duct
Major channel for lymphatic drainage from most regions of the body
Where does the thoracic duct empty
Into the venous system at the union of the left internal jugular vein and left subclavian vein
What type of organ is the thymus
Lymphoid organ
Where does the thymus lie
Superior mediastinum
What is the pericardium
Tough, fibrous sac that encloses the heart like a loose-fitting bag
Why is the pericardium loose
Allow movement of the heart within it
How many layers do the pericardium have and there names
2
Outer fibrous layer
Inner serous layer
Where is the tough, outer fibrous layer of the pericardium attach
Attached superiorly to the great vessels
Inferiorly to the central tendon of the diaphragm
What are the two parts of the thin, inner serous layer
Parietal layer
Visceral layer
What does the parietal layer of the inner serous layer line
Inner aspect of the fibrous pericardium
What does the visceral layer of the inner serous layer line
Covers the surface of the heart
What is the space between the two layers of the serous pericardium
Pericardial cavity
What does the pericardial cavity contain
Small amount of pericardial fluid that lubricated the serous membranes
Allows them to slide over each other with movements of the heart
What innervates the fibrous pericardium
Right and left phrenic nerves give rise to sensory branches
Where does the apex project
Left of the sternum towards the left lung
Name the surfaces of the heart
Base
Inferior surface
Anterior surface
Pulmonary surface
Where does the base (surface of the heart) face
posteriorly
What is another name for the base surface
Posterior surface
Where is the inferior surface of the heart
Lies on the central tendon of the diaphragm
What is another name for the inferior surface
Diaphragmatic surface
What does the anterior surface face
The sternum and ribs
What is another name for the anterior surface
Sternocostal surface
What is the pulmonary surface
Left and right sides of the heart face the lungs
What does the base/posterior surface of the the heart relate to
Left atrium
Part of right atrium
What does the inferior/diaphragmatic surface relate to
Left ventricle
Part of the right ventricle
What does the anterior/sternocostal surface relate to
Right ventricle
What does the left pulmonary surface relate to
Left ventricle
What does the right pulmonary surface relate to
Left atrium
What is the apex formed by
Left ventricle
Where does the apex lie
Lies at the left 5th intercostal space in the midclavicular line
Where is the apex palpable
Left 5th intercostal space in the midclavicular line
What does the right border correspond to
Right atrium
What does the left border correspond to
Left ventricle
What does the inferior border correspond to
Right ventricle and part of the left ventricle
Where does the right border lie
Lateral to the right sternal angle
From right 3rd to right 6th costal cartilage
Where does the left border lie
Extends from left 2nd to left 5th intercostal space in the midclavicular lie
Where does the superior border lie
Along the line connecting the superior extents of the right and left borders
right 3rd costal cartilage to left 2nd intercostal space
Where does the inferior border lie
Along the line connecting the inferior end of the right border with the apex
What is an auricle
Outpouchings from the walls of the right and left atria
