Lesson 3 - Heart Anatomy Flashcards
What are the three layers of the heart?
Endocardium - The heart’s interior lining
Myocardium (“Myo” = Muscle) - The heart’s muscle
Pericardium (“Peri” = Peripheral) - Encloses the heart
Why is the pericardial fluid necessary?
There is a fluid lining in between the pericardium (“sack”) and the actual heart to reduce friction with other organs during pumps. However, the lining is not completely efficient as the “sack” itself could be causing friction with the wall of the heart.
Which side of the heart pumps to the lungs and which side of the heart pumps to the rest of the body?
The left side of the heart pumps to the rest of the body and the right side of the heart pumps to the lungs. The left side is thicker because it needs to apply more pressure to send blood all the way to the brain and down to the toes. It must go against gravity in order to do so. The right side does not need to apply as much pressure because the lungs are not as far.
What is the difference between the pulmonary circuit and the systemic circuit?
The pulmonary circuit conveys blood between the heart and lungs. The systemic circuit carries blood between the heart and the rest of the body. The arteries of the systemic circuit all carry oxygen-rich blood. The arteries of the pulmonary circuit carry oxygen-poor blood. (This is why arteries cannot be defined by the amount of oxygen in the blood.)
What are the first branches from aorta?
The first branches from the aorta are the coronary arteries, which supply blood to the myocardium. They can become clogged and can cause angina pectoris or even a heart attack (myocardial infarction).
What is the bicuspid valve?
The mitral valve, also known as the bicuspid valve or the left atrioventricular valve, is a dual-flap valve in the heart that lies between the left atrium and the left ventricle.
During diastole, a normally-functioning mitral valve opens as a result of increased pressure from the left atrium as it fills with blood. As atrial pressure increases above that of the left ventricle, the mitral valve opens. Opening facilitates the passive flow of blood into the left ventricle.
What is the tricuspid valve?
The tricuspid valve, also known as the right atrioventricular valve, is between the right atrium and the right ventricle. The function of the valve is to prevent back flow of blood into the right atrium.
How is cardiac muscle contractile?
It can shorten when stimulated. Its membrane is polarized, with excess Ca 2+. When stimulated, ions channels on the membrane allow positive ions to rush inside. These cause actin and myosin filaments to move past each other, generating a force.
How is cardiac muscle self -excitable?
Unlike skeletal muscle, cardiac muscle will spontaneously open its ion channels without a signal from a neutron. It may be signalled by its neighbours, when their ions leak across the connections at the intercalated disks. This is depolarization as the electrical charges were polarized before the event. The muscle must then use energy to re-polarize.
How is cardiac muscle auto-rhythmic (like a metronome)?
If not signalled by an external source, cardiac muscles will depolarize with a regular rhythm, usually about every 1.5 seconds. Pacemaker cells depolarize at a faster rhythm than other cardiac muscle.
How is cardiac muscle non-fatiguing?
Unlike skeletal muscles, cardiac muscles (under normal strain) can contract indefinitely without tiring or becoming damaged.
What is depolarization?
Depolarization is the spontaneous opening of calcium channels. It is a signal for contraction and activates motor proteins (actin and myosin). This occurs when the high concentration of calcium 2+ outside moves into the low concentration of calcium in the muscle, which has a negative charge. The calcium comes rushing into the cell through the calcium channels and they enter through diffusion. This means that the muscle will have positively charged calcium after the calcium 2+ rushes into it.
What are the two types of specialized junctions in the intercalated disks?
Intercalated disk contain desmosomes, which hold the cells tightly together and enable muscle cells to resist the mechanical stress associated with the stretching and contraction of the cardiac cycle. They also have gap junctions, which allow for rapid communication of action potentials between cardiac muscle cells.
What is the correct sequence in which a drop of blood returning from the body encounters the heart chambers?
Right atrium, right ventricle, left atrium, left ventricle.
