Mediastinum & Heart I Flashcards
Mediastinum
- Location?
- Bounded by what superiorly and inferiorly?
- Houses?
- Superior and inferior mediastinum divide where?
Mediastinum
Midline region between right and left pleural cavities
Bounded superiorly by the superior thoracic aperture (includes: rib 1, T1 vertebrae, and manubrium) and inferiorly by the diaphragm
Houses all of the thoracic organs except the lungs
Superior and inferior mediastinum divides at sternal angle at T4 / T5
Thymus
- What kind of organ?
- Location?
- What happens after puberty?
Thymus
Lymphoid organ
Posterior to manubrium and body of sternum. Inferior aspect of thymus is anterior to pericardium.
After puberty, thymus undergoes gradual involution (shrinking) and is largely replaced by fat
However, it continues to function throughout adult life
Pericardium
- What is it?
- What are the layers?
Pericardium
Fibroserous membrane that surrounds the heart and root of great vessels
Fibrous pericardium - tough external layer, inelastic, prevents heart from overfilling, attached to central tendon of diaphragm
Parietal layer of serous pericardium - lines inner surface of fibrous pericardium (continuous with visceral at great vessels)
Visceral layer of serous pericardium - adheres to surface of heart (continues with parietal at great vessels)
Phrenic nerves
- Location?
- Motor innervation to?
- Sensory innervation to?
Phrenic nerves
Phrenic nerves (ventral rami C3, 4, 5) course on the superficial aspect of the pericardium, anterior to the root of the lungs
Motor innervation to the diaphragm
Sensory innervation to the diaphragm, parietal pleura, and pericardium (fibrous and parietal)
Pericardial cavity
- What is it?
- What does it contain?
- Pericarditis
- Cardiac tamponade
Pericardial cavity
Potential space between the parietal and visceral layers of the serous pericardium
Contains thin layer of serous fluid
Pericarditis is the inflammation of the serous pericardium. Results in roughened layers that produce pericardial friction rub “rustle of silk” during auscultation
If fluid accumulate in pericardial cavity, cardiac tamponade (heart compression) may result. Since the fibrous pericardium is inelastic, the fluid will eventually restrict the heart’s ability to expand and fill with blood
Pericardiocentesis
- What is it?
- What are the two approaches?
Periocardiocentesis
Echo guided pericardiocentesis can be performed to drain fluid from the pericardial cavity
Subxiphoid approach - a needle is inserted to the left of the xiphoid process and directed superiorly, deep to the costal margin (need to watch out for internal thoracic artery)
Parasternal approach - a needle is inserted to the left of the sternum, in the left 5th or 6th intercostal space (takes advantage of the cardiac notch in left lung)
Other locations can also be targeted
Surface anatomy of the heart
- Apex and base location?
- What occupies anterior and posterior position?
- What are the borders of the heart?
Surface anatomy of the heart
Apex is directed anteroinferiorly and to the left, and is formed by the left ventricle
Base is directed posteriorly and is formed by the left atrium
Right ventricle occupies anterior position, relative to rest of the chambers
Left atrium occupies posterior position, relative to rest of the chambers
Right border - right atrium between SVC and IVC
Left border - left ventricle
Superior border - right and left atria
Inferior border - right ventricle
Superior vena cava and inferior vena cava
Returns _________ blood from __________ to __________
Superior vena cava - returns oxygen poor blood to right atrium from structures superior to diaphragm (except heart)
Inferior vena cava - returns oxygen poor blood to right atrium from structures inferior to diaphragm
Veins that form superior vena cava
Veins that form superior vena cava
Internal jugular and subclavian veins join to form right and left brachiocephalic veins
Right and left brachiocephalic veins join to form SVC
Brachiocephalic veins
- Location?
- What do they join to form?
- What do they branch off into?
- Which side is longer?
Brachiocephalic veins
Lie anterior to the major arteries arising from aortic arch
Right and left brachiocephalic veins join to form SVC
Internal jugular veins and subclavian veins branch off
Left vein is much longer because it must cross midline to reach SVC
Aorta
- Where does ascending aorta emerge?
- Where does aortic arch start and end?
- Location of the aortic arch?
Ascending aorta emerges from left ventricle
Aortic arch begins / ends at sternal angle T4 / T5
Arches over the right pulmonary artery and courses posteriorly and inferiorly
Branches of the aortic arch
Branches of the aortic arch - proximal to distal
Brachiocephalic trunk (gives rise to the right subclavian artery and right common carotid artery)
Left common carotid artery
Left subclavian artery
Transverse pericardial sinus
- Location?
- Significance?
Transverse pericardial sinus
Located posterior to the aorta and pulmonary trunk
During cardiac surgery, this sinus allows surgeon to ligate or clamp the aorta and pulmonary trunk to control the arterial outflow during surgery
Parasympathetic innervation of the heart
- Effect on heart?
- Location of pre and post ganglionic cell bodies and fibers
Parasympathetic innervation of the heart
Slows heart rate
Preganglionic cell body - brain
Preganglionic fiber - vagus nerve
Postganglionic cell body - wall of target organ (heart)
Postganglionic fiber - wall of target organ (heart) and very short in length
Vagus nerves location
Vagus nerves location
Right and left vagus nerves course through the neck and into the mediastinum
Travel posterior to root of lungs
