Blood Flow and Circulation

The circulatory system operates on a principle of double circulation, featuring two distinct circuits:

1. Pulmonary Circuit: Pulmonary arteries carry deoxygenated blood from the heart to the lungs. Capillaries around alveoli allow oxygen and carbon dioxide exchange. Pulmonary veins return oxygenated blood to the heart for distribution.
2. Systemic Circuit: The aorta carries oxygenated blood from the left ventricle to body tissues. Superior and inferior vena cavae return oxygen-poor blood to the right atrium.

Highlight: Understanding the blood flow through the heart | step by step is crucial for comprehending the circulatory system's function.

The cardiac cycle consists of alternating contractions and relaxations:

• Diastole: The relaxation stage where heart chambers fill with blood.
• Systole: A brief contraction of atria followed by a powerful contraction of ventricles.

Vocabulary: Arterioles are smaller blood vessels branched off from arteries, while venules are small vessels that converge to form veins.

Heart problems can arise from various issues:

• Arrhythmia: Abnormal heart rhythms
• Heart attack $myocardial infarction$: Often due to blockage, affecting the SA node's ability to maintain normal rhythms
• Stroke: Death of brain tissue due to lack of oxygen, usually from arterial rupture or blockage

Definition: Atherosclerosis is the buildup of fatty deposits $plaque$ in vessels, restricting blood flow and potentially leading to heart attacks.

Blood composition plays a crucial role in the circulatory system:

• Plasma: The fluid matrix containing various substances
• Red blood cells $erythrocytes$: Transport oxygen bound to hemoglobin
• White blood cells $leukocytes$: Fight infections

Example: The 3 types of blood vessels and their functions work together like a complex highway system: arteries are the main roads carrying blood away from the heart, veins are the return routes, and capillaries are the local streets delivering nutrients directly to cells.