Heart and Great Vessels - SDL Worksheet Flashcards
Define the term mediastinum
Mass of tissues and organs separating the sternum in front and the vertebral column behind, containing the heart, its vessels, trachea, oesophagus, thymus, lymph nodes and other structures and tissues
What is the mediastinum divided into?
2 parts by imaginary line –> superior and inferior
Where is mediastinum divided?
By imaginary line from the sternal angle to T4 vertebrae.
Where does superior aspect of mediastinum terminate?
extends upwards, terminates at superior thoracic aperture
Where does inferior aspect of mediastinum terminate?
extends downwards, terminates at the diaphragm
What can the inferior aspect of the mediastinum be divided into?
Anterior, middle and posterior
Describe boundaries of:
- Anterior
- Posterior
- Lateral
- Superior
- Inferior mediastinum
- Pericardium
- Bodies of thoracic vertebrae 5-12
- Mediastinal pleura
- Plane of sternal angle up to superior thoracic aperture
- Sternal angle down to diaph§agm
What is the phrenic nerve?
Bilateral, mixed nerve that originates in the neck and descends through the thorax to reach the diaphragm. As the only source of motor innervation to the diaphragm this nerve has an important role in breathing
What is the motor function of the phrenic nerve?
Innervates the diaphragm
What is the sensory function of the phrenic nerve?
Innervates the central part of diaphragm, the pericardium and mediastinal part of parietal pleura
Where does the right phrenic pass in relation to the subclavian artery and vein?
Passes anteriorly to the 2nd part of subclavian artery, and posteriorly to the subclavian vein.
Enters thorax.
How does the right phrenic pass into the thorax?
Enters thorax via superior thoracic aperture
Where does the right phrenic pass after entering thorax?
Descends anteriorly to the right lung root, down the right side of the pericardium. Reaches the diaphragm and pierces the muscle to supply the underlying surface
Where does the left phrenic pass in relation to the subclavian artery and vein?
Passes anteriorly to the 1st part of subclavian artery and posteriorly to the subclavian vein.
Enters thorax
How does the left phrenic pass into the thorax?
Enters thorax via superior thoracic aperture
Where does the left phrenic pass after entering thorax?
Crosses the aortic arch and vagus nerve, and descends anteriorly to the left lung root, down the left side of the pericardium. Reaches the diaphragm and pieces the muscle to supply the underlying surface
Describe the vagus nerve
- 10th cranial nerve (CN X)
- Longest cranial nerve
Describe the origin of the vagus nerve
Originates from the medulla of the brainstem
How does the vagus nerve exit the cranium?
Via jugular foramen
Where does the auricular branch of the vagus arise?
Within the cranium
Describe the route of the common vagus nerve after leaving the cranium
Passes into carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery. R and L have different pathways
Describe pathway of left vagus
Passes inferiorly between left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering thorax
Describe pathway of right vagus
Passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering thorax
What branches arise in the neck of the vagus (after it leaves the cranium)?
- Pharyngeal branches
- Superior laryngeal nerve
- Recurrent laryngeal nerve (right side only)
What is function of the pharyngeal branches?
Provides motor innervation for muscles pharynx and soft palate
What does the superior laryngeal nerve split into?
Splits into internal and external branches
What does the external laryngeal nerve innervate?
The cricothyroid muscle of the larynx
What does the internal laryngeal nerve innervate?
Provides sensory innervation to the laryngopharynx and superior part of the larynx.
What does the recurrent laryngeal nerve innervate?
Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx.
Describe vagus nerve once it enters thorax
- Forms posterior vagal trunk (right), anterior vagal trunk (left)
Where does left recurrent laryngeal nerve arise? What is its function?
In the thorax
Hooks under arch of aorta, ascending to innervate the majority of intrinsic muscles in larynx), cardiac branches (innervate regulate heart rate and provide visceral sensation to the organ)
How do the vagal trunks terminate?
By dividing into branches that supply the oesophagus, stomach, small and large bowel
What are branches of ascending aorta?
Rises up from the heart. The coronary arteries branch off the ascending aorta to supply the heart with blood
Branches of aortic arch?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
What is the ligamentum arteriosum?
Arterial ligament. Small ligament connected to the superior surface of the proximal descending aorta and left pulmonary artery