Anatomy of CVS Flashcards
What are the anatomical borders of the mediastinum?
Region between the lungs:
AP: sternum - body of vertebra
SI: superior thoracic aperture - diaphragm
Lungs on the sides
What are the contents of the anterior mediastinum?
Sternopericardial ligaments: connect sternum to the fibrous pericardium,
thymus (children)
thoracic artery + branches
Lymphatics
What’s in the middle mediastinum?
The heart
What surrounds the heart and what structure is just underneath it?
What could happen to this structure that might make the heart stop beating?
The fibrous pericardium is the tough CT layer that covers the heart
The serous layer has a visceral and parietal layer:
-Parietal; adheres to the fibrous pericardium
-Visceral: surrounds the heart
Between them is the pericardial cavity: has lubricating fluids that allow for movement of the heart
*Any leaking blood will fill up the pericardial bag/cavity - if it reaches a certain volume it can stop the heart from beating.
What’s in the posterior mediastinum?
What is it particularly susceptible to?
thoracic (descending) aorta, azygous vein, thoracic duct, esophagus, posterior mediastinal lymph nodes, VAGUS and splanchnic nerves
It’s a large communication channel; so it’s more susceptible to tumours, infection, etc.
What is mediastinitis? Name one sign and three possible symptoms
Mediastinitis: inflammation of the mediastinum
Sign: entire mediastinum may shift due to fluid buildup
Symptoms: SOB, difficulty swallowing, hoarse voice
What’s the thymic sail sign? What can it be confused with?
A ‘sailship’ looking silhouette on an X-ray that indicates the thymus, can be confused with fluid accumulation
Describe the pathway of the VAGUS N going inferior -> superior
Travels through mediastinum: posterior to lung roots and anterior to subclavian, forms “vagal fibres”/plexus around the esophagus and the R descends posteriorly/L descends anteriorly up the esophagus
What does the phrenic N supply?
The diaphragm and the pericardium
What’s the transverse pericardial sinus, what can it be used for in surgery?
Passageway that is posterior to the arterial output/pulmonary trunk and anterior to the superior vena cava
Can be clamped in surgery to stop arterial blood flow
What happens if you have damage to the papillary muscles?
Valve incompetence and cardiac murmur
Name 3 things that aid the valves?
Chordiae tendinae, papillary muscles, cardiac fibrous skeleton (high-density fibrous structure of CT that forms and anchors the valves)
What prevents electrical signals from being mixed between the atria and ventricles?
Fibrous Tissue
Describe the structure of aortic/pulmonary valves and how they open and close
3 cusps: semilunar
Diastole: The backwards flow of blood fills up pockets/cusps, expanding them and closing the valve
Systole: rapid ejection of blood pushes the cusps against the vessel wall, opening the valve
Where does the L coronary artery start and what can branch off of it?
LCA arises from the aorta above the L cusp of the aortic valve
Gives off:
1. Widowmaker: Anterior interventricular artery/L anterior descending: supplies the bulk of R and L ventricles, anterior 2/3rds of the septum and AV node in 20%
- Circumflex; L atrium and ventricle; continues as PIVA in 40% of people which supplies the AV node in 20%
What can branch of the R coronary artery and where does it start?
Above R anterior cusp
- PIVA in 60%; AV node in 80% and posterior 1/3 of the septum
- Sinoatrial node artery: SA node, R and L atria
- Marginal artery; reaches the apex
Where does the bulk AND the minority of cardiac venous drainage go through?
Bulk: coronary sinus
Minority: some anterior veins are independent of the coronary sinus and drain directly into the R atrium
What are venae cordis minimi?
Little direct openings in the heart wall that return venous drainage directly into heart chambers
Where should the apex of the heart be on a chest?
What does it mean if the apex is somewhere else?
3.5 inches away from the midline in 5th ICS
If it’s lower, it indicates heart has enlarged due to being overworked (not good)
Which intercostal spaces and heart chambers make up the bulk of the R and L sides of the heart?
L: 2-5 ICS, L ventricle
R: 3-6 ICS, R atria
Where do you auscultate for each valve?
Mitral Valve: 5th ICS, Left mid-clavicular line
Tricuspid: 4th ICS, left sternal border
Pulmonary: L sternal edge, 2nd ICS
Aortic: R sternal edge, 2nd ICS
What was the fossa ovalis? What was it used for?
Was the foramen ovale that functioned as the shunt between the fetal R and L atria
Why are there rough and smooth surfaces in the R and L atrium?
Rough is the original portion, and smooth is where other vessels have been pulled into the chamber:
R atria: Smooth where the venae cava were pulled in
L atria: smooth where the pulmonary veins have been pulled in
What’s the conus arteriosus and what did it develop from?
smooth wall part in the R ventricle, develops from the bulbus cordis
What does the ligament arteriosum do and what is it the remnant of?
Holds the aorta and pulmonary artery close together, a remnant of the ductus arteriosus
Name which nerves give sympathetic and parasympathetic innervation to the heart, which is associated with referred cardiac pain?
Sympathetic: T1-T4 derived parts of the sympathetic chain, associated with referred cardiac pain: as cardiac visceral sensory fibres travel back to CNS with sympathetic nerves
Parasympathetic: VAGUS n, cardiac branches mainly arise in the thorax and post-ganglionic fibres arise from ganglia on the heart
What does the fibrous pericardium bind to inferiorly?
The central diaphragmatic tendon (also a boundary of most middle mediastinum)
What symptoms can result from decreased perfusion to the R coronary?
Since the R coronary artery supplies the SA node, decreased perfusion can cause an arrhythmia and bradycardia
Which vertebral level is a deep injury detrimental?
T4/T5 - 2nd costal cartilage
Overall, what do the R and L coronary normally supply?
R: R atria and ventricle, SA node, AV node, posterior IV septum
L: atria and ventricle, anterior IV septum and AV bundle
