Mediastinum and Heart Flashcards
(33 cards)
What is housed in the Mediastinum?
All the thoracic organs except the lungs
What are the superior and inferior borders of the mediastinum?
Superiorly: Superior thoracic aperture (1st ribs, manubrium, T1 vertebra)
Inferiorly: Diaphragm
How is the Mediastinum divided up superiorly and inferiorly?
Horizontal plane passing through the sternal angle and T4/T5 IV disc separates the region into the superior mediastinum and inferior mediastinum
Describe the Thymus.
It is a lymphoid organ and it undergoes gradual involution and is largely replaced by fat by adulthood, after puberty.
-Lies posterior to the manubrium and body of the sternum; its inferior aspect lies anterior to pericardium
What is the pericardium?
Fibroserous membrane that surrounds the heart & roots of the great vessels
Discus the location of the phrenic nerve.
“Ventral rami of C3, C4, C5 keep the Phrenic alive” Course on the superficial aspect of the pericardium, anterior to the root of the lungs
What does the phrenic nerve innervate?
- Motor innervation to diaphragm
- Sensory innervation to diaphragm, parietal pleura and pericardium (fibrous pericardium and parietal layer of serous pericardium)
Describe the layers of the Pericardium.
- Fibrous pericardium: Tough external layer. Inelastic and so protects the heart against overfilling. Attached to the central tendon of the diaphragm
- Parietal layer of serous pericardium: Lines inner surface of fibrous pericardium
- Visceral layer of serous pericardium (epicardium): Continuous with parietal layer of serous pericardium at great vessels. Adhered to surface of heart
What is the Pericardial cavity?
- Potential space between the parietal and visceral layers of the serous pericardium
- Contains thin layer of serous fluid
What is pericarditis and what effect does it have?
- Inflammation of the serous pericardium
- Will result in roughened surfaces that produce a pericardial friction rub during auscultation
What happens if fluids accumulate in the 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.
Describe an Echo-guided pericardiocentesis.
- It can be performed to drain fluids 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
- Left parasternal approach: A needle is inserted to the left of the sternum, in the left fifth or sixth intercostal space.
Describe the borders of the heart.
- Right border: right atrium between the superior vena cava & inferior vena cava
- Inferior border: primarily right ventricle
- Left border: primarily left ventricle
- Superior border: right and left atria
What comprises the anterior, posterior, apex, and base of the heart?
Anterior position = Right ventricle
Posterior position= Left atrium
Apex = Left ventricle
Base = Left atrium
Discuss the brachiocephalic veins and superior vena cava (SVC).
- Internal jugular + subclavian veins –> form left and right brachiocephalic veins (Left is longer)
- Left and right brachiocephalic veins –> form the SVC
-Brachiocephalic veins lie anterior to the major arteries arising from the arch of the aorta
Describe the parts of the Aorta.
Ascending aorta: Emerges from left ventricle
Arch of the aorta: Begins at sternal angle (T4/T5), arches over the right pulmonary artery and courses posteriorly and inferiorly
Thoracic aorta: After sternal angle.
What branches off the Aorta?
- Brachiocephalic trunk: Gives rise to right subclavian and right common carotid arteries
- Left common carotid artery
- Left subclavian artery
What is the location and significance of the Transverse pericardial sinus?
- Located posterior to the aorta and pulmonary trunk
- During cardiac surgery, the presence of the transverse pericardial sinus allows the surgeon to ligate or clamp the aorta and pulmonary trunk to control the arterial outflow during surgery
What are the grooves that the coronary vessels sit in on the heart’s surface?
- Coronary (atrioventricular) groove
- Anterior and posterior interventricular grooves
What are the branches of the Right coronary artery (RCA)?
- Travels in the coronary groove
- Usually gives off sinoatrial (SA) nodal branch
- At inferior border of the heart, gives off right marginal branch
- Finally, gives off posterior interventricular branch which occupies the posterior interventricular groove
What are the branches of the Left coronary artery (LCA)?
- Gives off anterior interventricular branch (left anterior descending, LAD) which occupies the anterior interventricular groove and runs towards the apex of the heart
- Gives off circumflex branch which occupies the coronary groove
- The circumflex branch gives rise to the left marginal branch
Describe venous draining of the heart.
Great, Middle, and Small cardiac vein collect into the coronary sinus (located posterior portion of the coronary groove) –> drains into right atrium
Describe the structures in the right atrium.
- Openings of the IVC, SVC, and coronary sinus
- Right auricle is an appendage of the right atrium with pectinate muscles
- Crista terminalis = Ridge separating auricle and smooth posterior wall
- Fossa ovalis = oval-shaped depression in the interatrial septum that is the remnant of the embryonic foramen ovale
Describe the structures in the right ventricle.
- Trabeculae carneae muscle
- Anterior, posterior, and septal papillary muscles
- Chordae tendineae extend between papillary muscles and cusps of tricuspid valve
- Septomarginal trabecula (moderator band) = Muscle bundle extending from interventricular septum to anterior papillary muscle. Carries a portion of the right bundle branch (part of the conducting system of the heart)
