Lecture 3 - Heart Flashcards
What is the mediastinum?
Identify these structures on this image.
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 = bounded by T1 vertebra, first ribs (L + R) and manubrium
Explain the different subdivisions of the mediastinum.
The most important reference landmark for dividing the mediastinum is the
sternal 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.
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)
• phrenic nerve (L+R)
• azygos vein
• thoracic duct
• sympathetic chain (L+R)
• lymph nodes
What are the contents of the inferior mediastinum?
Inferior mediastinum has 3 parts:
- anterior
- middle
- posterior
What is the anterior mediastinum?
Anterior mediastinum
Located posterior to the sternum and anterior to the heart. Contents:
• thymus gland (atrophied, mostly fat)
• some lymph nodes
What are the contents of the middle mediastinum?
Middle mediastinum
Contents:
• pericardial sac
• heart
• part of superior vena cava
• ascending aorta
• pulmonary trunk with L + R
pulmonary arteries
• pulmonary veins (L+R)
• phrenic nerves
• lymph nodes
What are the contents of the posterior mediastinum?
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
External anatomy of the heart.
Anterior view.
Identify the structures on this image.
External anatomy of the heart.
Posterior view.
Identify the structures on this image.
Explain the internal anatomy of the heart.
What are the heart valves?
Explain the different parts of the heart valves between chambers and name the different structures of the image.
Between chambers:
1. Tricuspid valve
2. Bicuspid (Mitral) valve
Parts:
• Cusps
• Chordae tendineae
• Papillary muscles
Explain the heart valves that are in vessels.
In vessels - semilunar valves:
- Aortic valve (in the base of aorta)
- Pulmonary valve (in the base of pulmonary trunk)
Explain the blood flow through the heart.
Blood flow through the heart:
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 through
pulmonary 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.
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 makes the heart sounds.
The valves control the direction of blood flow. The valves make sound only when they
close (“lub-dub”). As the heart beats, the valves close in a specific order. As ventricular
contraction begins the mitral and then the tricuspid valves close (“lub”, the first heart sound,
S1). As ventricular pressure increases, the pulmonary and then the aortic valves open and
blood is pumped into the large elastic arteries. As the contraction ends, the aortic and then
the pulmonary valves close (“dub”, the second heart sound, S2). During relaxation, the
tricuspid and then the mitral valves open and the ventricles fill.
What is the blood supply of the heart? Identify the image.
Right and left coronary arteries – branches of the ascending aorta.
Fill in the blanks.
Right coronary artery gives:
•
•
Left coronary artery gives:
•
•
Right coronary artery gives:
• Marginal artery
• Posterior interventricular artery
Left coronary artery gives:
• Anterior interventricular artery
• Circumflex artery
Explain the blood drainage of the heart.
Main veins of the heart:
• Great cardiac vein
• Middle cardiac vein
• Small cardiac vein
Blood drainage of the heart
All veins ultimately drain into
the largest vein of the heart,
the coronary sinus which
delivers blood to the right
atrium.
Explain the sympathetic and parasympathetic of the heart.
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.
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 the
atrioventricular node (AV node), which
regulates the contraction of most of the
heart.
Explain the Bundle of his.
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
Review.
