The cardiovascular system carries oxygen from the respiratory system and nutrients from the digestive system to every cell, and takes waste to the kidneys and lungs.
Role
The heart and blood vessels move blood, carrying materials to the other systems.
Links
- Respiratory: picks up oxygen and drops off CO2.
- Digestive: carries nutrients from the gut.
- Kidneys: filter blood, controlling pressure.
- Endocrine: distributes hormones.
- Immune: moves white blood cells.
- Muscular: supplies muscles.
Facts
Blood circulates the body in about 1 minute.
Why it matters
All organs depend on blood flow.
Numbers on the circulatory loop
The heart beats about 100,000 times per day and pumps roughly 5 liters of blood per minute at rest, about 7,500 liters per day. An adult has about 96,000 km (60,000 miles) of blood vessels. Blood makes two circuits: the pulmonary circuit to the lungs and the systemic circuit to the body.
- Respiratory system: red blood cells pick up oxygen in the lungs and release carbon dioxide. Hemoglobin carries about 98 percent of oxygen in the blood.
- Kidneys: they receive about 20 to 25 percent of cardiac output and filter blood to regulate pressure and fluid volume through the renin-angiotensin system.
- Endocrine system: hormones such as adrenaline raise heart rate, and atrial natriuretic peptide from the heart signals the kidneys to excrete sodium.
- Lymphatic system: returns about 2 to 4 liters of fluid per day to the blood.
Why it matters
Cardiovascular disease is the leading cause of death worldwide, causing about 17.9 million deaths per year according to the WHO. Digestive absorption of nutrients, skin temperature control and immune cell transport all depend on circulation. Blood pressure, cholesterol, smoking and diabetes are the main modifiable risk factors.
Numbers on the circulatory loop
The adult heart beats about 60 to 100 times a minute and pumps roughly 5 liters of blood per minute at rest. Blood travels through about 100,000 km of vessels. The circulatory system delivers oxygen from the lungs, nutrients from the digestive system and carries hormones and waste to the kidneys.
Why it matters
The respiratory system oxygenates blood, the kidneys regulate fluid and pressure and the nervous system controls heart rate. Exercise raises output up to 20 to 25 liters per minute in trained athletes.
Heart and lungs working together
The right side of the heart sends blood to the lungs, where oxygen enters and CO2 leaves through alveoli, a surface area of about 70 square meters. The left side pumps oxygenated blood to the body. Heart rate and breathing rise together in exercise. Cardiac output equals stroke volume times heart rate, about 70 mL times 70 bpm at rest.
Links to other systems
The kidneys regulate blood volume and pressure through renin. The endocrine system releases adrenaline to speed the heart. The nervous system controls vessel diameter. The digestive system delivers nutrients that blood carries. The immune system uses blood to deliver white cells. Heart failure affects about 6.7 million Americans, and illustrates the connections.
Based on data from the American Heart Association and the NIH
