#05: Heart I Continued

Question 1

Veins vs. Artery Role

Answer 1

• Blood is bought to the heart by the veins to both sides of heart and transported out of heart by arteries.

Question 2

Similarity in Both Sides of Heart

Answer 2

• The volume of blood is same in each side of the heart, and the two sides of the heart contract at the same time.

Question 3

Blood Flow Cycle Beginning With Pulmonary Veins

Answer 3

• Pulmonary veins deliver oxygenated blood to the left side of the heart. Blood leaves the left side of heart into the aorta and enters the systemic circulation. Deoxygenated blood from the body returns to the right side of the heart through the vena cavas. After entering the right side of the heart, blood passes into the pulmonary arteries, where it then travels to the lungs. Then it returns to the heart through the pulmonary veins and the cycle repeats.

Question 4

Blood Flow Beginning With Deoxygenated Blood After Capillaries

Answer 4

• Deoxygenated blood is carried back towards the heart by veins into the right atrium. The right ventricle sends it through the pulmonary arteries to the lungs for oxygenation. Oxygenated blood is then carried back towards the heart by pulmonary veins into the left atrium. The left ventricle then sends it through the aorta and arteries to supply nutrients to body tissues.

Question 5

Atrioventricular Valves

Answer 5

• Blood flowing through the atrioventricular canal passes through the atrioventricular valves, or cusps of tissue, which allow blood flow only in one direction.

Question 6

Tricuspid Valve

Answer 6

○ The right atrioventricular valve is composed of three cusps of tissue and is known as the tricuspid valve.

Question 7

Mitral Valve

Answer 7

○ The left atrioventricular valve is composed of two cusps and is known as the bicuspid valve (or mitral valve).

Question 8

Papilalry Muscles & Chordae Tendineae

Answer 8

○ Each ventricle consists of cone-shaped muscle pillars called papillary muscles, which are attached to the atrioventricular valve cusps by chordae tendineae (thin, strong connective tissue strings). The papillary muscles contract in concert with the ventricle and prevent the valves from opening into the atria by applying tension to the chordae tendineae. Contraction of the ventricle closes the atrioventricular valves by applying fluid pressure to the cusps. During ventricular contraction, the ventricle is a closed chamber preventing flow of blood back into atria.

Question 9

Semilunar Values

Answer 9

• Ventricular openings to pulmonary arteries and aorta are the semilunar valves. Each semilunar valve is composed of 3 pocket-like semilunar cusps. The 3 inner borders of the semilunar valves meet in the center of the artery to block blood flow. Blood leaving the ventricles pushes against the semilunar valves, forcing them to open. Tendons or papillary muscles don’t support these valves. These valves are closed by blood pushing against them from the arteries, preventing arterial blood from flowing back into ventricles during diastole.

Question 10

Opening: AV vs. SL Valves

Answer 10

• So AV valves open when ventricles are relaxed, while SL valves open when ventricles are contracted.

Question 11

Heart Sounds

Answer 11

• Each atria and ventricle pass through systolic (contraction) and diastolic (relaxation) phases in unision. The AV and SL valves must open and close to accommodate these phases. This causes “heart sounds”.
○ During the “lub” sound, the atria enters its diastole phase, while the ventricle enters its systole phase. During the longer “dupp” sound, the ventricle enters its diastole phase, while the atria remains in its diastole phase, until near the end of the sound where it quickly enters the systole phase and then the whole cycle repeats.

Question 12

Heart Murmurs

Answer 12

○ Abnormal valve function causes heart murmurs, the sound produced by blood backflow.

Question 13

Foramen Ovale

Answer 13

• Foramen ovale is a path between the right and left atria that is only there during fetal development.

Question 14

Coronary Circulation

Answer 14

• Coronary circulation is a circulatory pathway exclusive to the heart. It’s required cause heart muscle requires continuous perfusion and a constant supply of oxygen. Heart muscle can’t respire anaerobically like skeletal muscle.
○ Left and right coronary arteries travel within the coronary sulcus of heart to supply the heart wall. They’re only branches of the ascending aorta.
○ All coronary veins drain deoxygenated blood into the coronary sinus, a large vein that lies in the posterior aspect of the coronary sulcus. The coronary sinus drains directly into the right atrium of the heart.

Question 15

Fibrous Skeleton

Answer 15

• The cardiac muscle is attached to a fibrous skeleton. This connection provides support, elasticity, prevents overexpansion, and electrical insulation.

Question 16

Purpose of AV Bundle

Answer 16

• You need the AV bundle to propagate signal to ventricle.

Question 17

Cardiac Muscle vs. Skeletal Muscle

Answer 17

• The cardiac muscle shares many similarities but also differences with the skeletal muscle.
○ Similarly wise, they’re both striated, may have 2 nuclei, and have a similar sarcomere/contraction system.
○ Differently, cardiac muscle is arranged in sheets or spiral bundles of cells interconnected end to end and laterally to adjacent cells by intercalated disks (specialized cell contacts that allow heart cells to act in unison).
○ Another difference is that most of the myoccardium is vascularized by more than one arterial branch. Many of these arterial branches fuse to form anastomoses (end to end continuity of two blood vessels).