Chapter Two - Heart Flashcards
What is the mediastinum? What is the thoracic inlet?
Mediastinum is the midline visceral space in the thorax between the thoracic inlet superiorly, the diaphragm inferiorly, the sternum anteriorly, and the bodies of thoracic vertebrae T1-T12 posteriorly
Thoracic inlet = area bounded by T1 vertebra, first ribs (L + R) and manubrium.
What is the most important reference landmark for dividing the mediastinum? What are the two main subdivisions of the mediastinum, and what line separates them?
The most important reference landmark for dividing the mediastinum is thesternal angle. A plane drawn between the sternal angle and the inferior edge of the fourth thoracic vertebra (T4) separates the superior and inferior mediastinum.
What are the contents of the superior mediastinum?
Superior mediastinum
Contents:
superior vena cava
brachiocephalic veins (L + R)
arch of aorta
brachiocephalic artery
left common carotid artery
left subclavian artery
trachea and primary bronchii
esophagus
vagus nerve (L+R) (vagus means wondering)
phrenic nerve (L+R)
azygos vein
thoracic duct
sympathetic chain (L+R)
lymph nodes
How many parts does the inferior mediastinum have? What are they called?
Inferior mediastinum has 3 parts:
- anterior
- middle
- posterior
Where is the anterior mediastinum situated? What does it contain?
Located posterior to the sternum and anterior to the heart.
Contents:
- not much, mostly fat… but also, thymus gland (atrophied, mostly fat)
- some lymph nodes
What does the middle mediastinum contain?
Contents:
pericardial sac
heart
part of superior vena cava
ascending aorta
pulmonarytrunkwithL+R pulmonary arteries
pulmonary veins (L+R)
phrenic nerves
lymph nodes
Where is the posterior mediastinum situated, precisely? What does it contain?
Posterior mediastinum
The posterior mediastinum is located posterior to the heart and anterior to the bodies of thoracic vertebrae T5 to T12.
Contents:
descending aorta
esophagus
vagal plexuses (branches of L and R vagus nerves)
azygos venous system
thoracic duct
sympathetic chain (L+R)
lymph nodes
Name the main external structures that we can observe in an anterior view of the heart.
Name the main external structures that we can observe in a posterior view of the heart.
What are the two heart valves between chambers? What are the two heart valves in vessels? In between which structure are they situated?
HEART VALVES:
Between chambers:
- Tricuspid valve
- Bicuspid (Mitral) valve
* valves have three and two “cusps”, respectively
In vessels:
- Aortic valve
- Pulmonary valve
(semilunar valves)
What are the parts of the heart valves situated between chambers?
Cusps
Chordae tendineae
Papillary muscles
Where does the “mitral” term come from?
From the mitor
What are the parts of the heart valves situated in vessels (semilunar valves)?
Parts:
Pulmonary sinus
Nodule
Lunule
Left, Anterior and Right Semilunar cusps
The bigger the valves get (filled with blood), the closer they come to each other and they close up the lumen of the pulmonary trunk
Describe in details the passage of the blood flow through the heart, starting at venous deoxygenated blood.
Venous (deoxygenated) blood returning to the heart from the body flows through the inferior and superior vena cava into the right atrium of the heart. Blood passes through the tricuspid valve to the right ventricle, which pumps the blood to the pulmonary trunk and pulmonary arteries to the lungs for oxygenation. Oxygenated blood returns from the lungs to the heart throughpulmonary veins to the left atrium. Blood passes from the left atrium through the bicuspid valve to the left ventricle. The left ventricle pumps the blood into the aorta and to the body.
Which are stronger, the atria or the ventricues, and which ventricule is stronger? Why?
The atria are thin walled and collect blood for the ventricles to pump blood out into arteries. The left ventricle is much stronger, i.e., more muscular, than the right ventricle.
What is the blood supply of the heart? Describe the main arteries and their ramifications.
Right and left coronary arteries – branches of the ascending aorta. *** The heart is the very first structure to receive blood from the aorta
Right coronary artery gives:
Marginal artery
Posterior interventricular artery
Left coronary artery gives:
Anterior interventricular artery
Circumflex artery
What are the two main types of nerve supply (innervation) that the heart has? What is the role of each of them?
The heart has a sympathetic and parasympathetic nerve supply.
Sympathetic innervation (“fight or flight”) increases the heart rate.
Parasympathetic innervation (“rest and digest”) decreases the heart rate. Vagus nerve (CN X) is the source of the parasympathetic fibers to the heart.
Other than the sympathetic and parasympathetic innervations, the heart has its own nerve supply. How is it called? What are its two nodes and what innervates them. Give their respective role.
The heart also has its own (intrinsic) nerve supply.
The sinoatrial node (SA node) is part of the intrinsic nerve supply of the heart and is regulated by the sympathetic and parasympathetic nervous systems.
The SA node regulates theatrioventricular node (AV node), which regulates the contraction of most of the heart.
What is the Bundle of His? What is it part of? Where is it situated? What is its role? How do we call the cells that compose it, and what is their role?
The Bundle of His is a part of the intrinsic electrical conduction system of the heart. It transmits impulses from the AV node (in the interatrial septum) to the ventricles of the heart. The bundle of His branches into the left and right bundle branches which run along the interventricular septum.
The conducting cells in the heart are not neurons, but modified cardiac cells called Purkinje fibers. They distribute the impulse to the ventricular muscle.
