TOPIC 2 Group A The heart pumps blood throughout the entire body The heart beats approximately 72 beats per minute supplying cells of the body with nutrients they need to survive Heart When looking at an image, the right and left are defined as the right and left of the patient.
When looking at an image, the right and left are defined as the right and left of the patient.
The atria of the heart are receiving chambers. The right atrium receives blood from the body via the superior and inferior vena cava and the left atrium receives blood from the lungs via the pulmonary veins.
The atrial chambers contain pectinate muscles within the walls of the chamber. Blood passes from the atria to the ventricles through a one-way opening called the atrioventricular valve.
The ventricles are the discharging chambers. The right ventricle pumps blood away from the heart to the lungs via the pulmonary arteries and the left ventricle pumps blood away from the heart to the body through the aorta.
The ventricular chambers contain trabeculae carneae muscle. Ventricular chambers are more muscular and larger in size because they must pump blood away from the heart into a system under higher pressure, the pulmonary arteries or aorta. The left ventricle is the most muscular since it functions to pump blood to the entire body via the aorta.
As blood fills the atria, the pressure rises and forces the blood into the ventricles through the one-way atrioventricular valve. The period of ventricular filling is called diastole in the cardiac cycle. When a physician listens with a stethoscope, the ventricle filling with blood sounds like a “lub”.
When the ventricles fill, an electrical impulse signals them to contract to push the blood into the pulmonary artery (right ventricle) or into the aorta (left ventricle). This period of ventricular contraction is called systole in the cardiac cycle. When a physician listens with a stethoscope, the ventricle squeezing blood out of the heard sounds like a “dub”.
To listen to heart sounds that determine healthy heart function, a physician places a stethoscope on the chest wall during an examination.
The physician locates the intercostal spaces, or spaces between the ribs, where certain structures pertaining to heart function can be heard.
This image of the anterior chest wall demonstrates stethoscope placements:
1= At the 2nd intercostal space, to the right of the midline, one can hear the blood in the aorta as it leaves the heart.
2= At the 2nd intercostal space, to the left of the midline, one can hear the blood in the pulmonary trunk as it leaves the heart.
3=At the 3rd through 5th intercostal spaces, just to the left of the midline, one listens for proper function of the right ventricle.
4=At the 5th intercostal space, far left of the midline, one listens for proper function of the left ventricle.
If one imagines the heart in place under the thoracic wall, the same stethoscope placements viewed in the previous slide can be correlated with blood flow through anatomically important structures of the heart.
1= Blood flow into the aorta can be heard.
2= Blood flow into the pulmonary trunk can be heard.
3= Blood flow between the right atrium and right ventricle, through the tricuspid valve, can be heard.
4= Blood flow between the left atrium and left ventricle, through the mitral valve, can be heard.
Blood flow in the Fetal Heart Differs from Blood Flow in the Heart after Birth
Normally blood flows from the right side of the heart to the left. Deoxygenated blood enters the right atrium then right ventricle. Blood travels to the lungs through the pulmonary artery to become oxygenated. The left atrium then receives the oxygenated blood. After passing through the left atrium, blood travels to the left ventricle and then to the aorta, and finally out to the body. However, in fetal circulation, blood in the heart is shunted away from the lungs.
To the Body
Typically, the foramen ovale and ductus arteriosus close following birth, thus altering the circulatory system. Blood begins to move from the right atrium to the left atrium and then to the lungs for the exchange of oxygenand carbon dioxide and the newborn begins to breath on its own. However, in some cases either of the two shunts may not close leading to health complications. The foramen ovale is initially closed by a flap. The pressure in the left atrium prevents the flap from opening. Eventually the flap seals closed so that the foramen ovale opening in the fetus becomes the fossa ovale depression in heart after birth.
If the flap forms incompletely or does not completely seal close, then deoxygenated blood can pass from the right atrium to the left atrium. A patient with an open or patent foramenovale will have a heart murmur. Unfortunately, this heart murmur maybe undetectable and the patient will exhibit no other obvious symptoms.
If the ductus arteriosus remains open after birth and fails to close it is referred to as a patent ductusarteriosus. The term “patent” means open. Complications associated with patent ductus arteriosus are poor growth and eating, easy tiring, and a rapid heart rate. It is also common to notice that the infant is blue in color, especially while feeding, due to a lack of oxygen.