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# The Cardiovascular System The heart is made up of cardiomyocytes, which are different from skeletal muscles and smooth muscles. They pump blood rhythmically and involuntarily. Electrical impulses in the heart create electrical currents that can be measured on the skin using electrodes. This is...

# The Cardiovascular System The heart is made up of cardiomyocytes, which are different from skeletal muscles and smooth muscles. They pump blood rhythmically and involuntarily. Electrical impulses in the heart create electrical currents that can be measured on the skin using electrodes. This is recorded as an electrocardiogram (ECG). ## Blood Vessels Blood flows through a complex network of blood vessels. **Arteries:** * Carry blood away from the heart. * The aorta is the main artery in the systemic circulation. * Major arteries branch to smaller arteries then arterioles, which extend into the muscles and organs. * Arterial walls are heavy and elastic near the heart, but the walls have more muscle further away, allowing for constriction to adjust blood flow rates. **Arterioles:** * Smaller branches of arteries leading to capillary beds. **Capillaries:** * Tiny, narrow tubes that allow for the exchange of oxygen, nutrients, and waste with tissues. * Fluid leaks from blood into interstitial space. **Venules:** * Connect capillaries to minor veins. **Veins:** * Bring deoxygenated blood back to the heart. * Thinner walls than arteries, due to lower pressure. * Veins have valves to prevent backflow of blood. The diagram shows the heart's structure and the path of blood flow through the body. Arrows indicate the direction of blood flow.