Mid-Unit Summary

This unit, we are learning about the circulatory system. The heart of the circulatory system is, metaphorically and literally, the heart itself.
Let's look at the structure of the heart. Comprised of four chambers, the heart is hollow to allow for blood to be pumped in and out. The chambers are the left ventricle, right ventricle, left atrium, and right atrium. The atria are the upper chambers, and the ventricles are below. The right atrium receives oxygen deprived blood. The left atrium receives oxygen rich blood. The right ventricle pushes blood out of the heart to the lungs. The left ventricle discharges blood to the body. There are valves in the heart that prevent back-flow of blood: the sublunar pulmonary and aortic valves, the tricuspid valve, and the bicuspid valve. The heart sounds we hear are the slamming of these valves shut.
The circulatory system branches from the heart to the entire body. The 3 components are the heart, the network of tubes, and the blood. Blood flows in veins to the hearts, or arteries away from the heart. Small arteries are called arterioles, and small veins are called venules.
Blood itself is comprised of 55% plasma and 45% cellular stuff. The cellular stuff is red blood cells, white blood cells, platelets, and others. The white blood cells are neutrophils, basophils, eosinophils, lymphocytes, and  monocytes. Platelets help blood clot. Red blood cells carry oxygen in the blood.
When there is an excess amount of LDL, the bad cholesterol, it sticks to artery walls, becoming a plaque, which can then rupture and cause a blood clot. Blood clots can lead to strokes and heart attacks, which are very deadly.

https://upload.wikimedia.org/wikipedia/commons/e/e0/Heart_diagram-en.svg
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