Circulatory system

Your body has a special way to move things.

Your heart pumps red liquid through tubes. These tubes are called blood vessels. The liquid carries food and air to your body. It also picks up waste to take it away.

Tiny tubes called capillaries help the food reach your parts. This system works to keep you healthy. It keeps your body at the right temperature, too.

It is a busy system that never stops!

Your body uses a circulatory system to move things around.

This system includes your heart, blood, and blood vessels. The blood is a fluid made of plasma. It also has red cells, white cells, and platelets.

Blood carries oxygen and nutrients to your tissues. It also picks up waste to take it away.

In humans, the system is closed. This means blood stays inside the vessels. The system has two main loops. The pulmonary circulation moves blood to the lungs. There, the blood picks up oxygen. The systemic circulation moves that oxygen-rich blood to the rest of your body.

Blood travels through different parts. It starts in large arteries. These branch into smaller vessels called arterioles. Then, it reaches tiny capillaries. These small tubes let nutrients reach your organs. After that, blood moves into veins. Veins carry the blood back to the heart. The heart has four chambers to help this work. It pumps the blood through the whole loop.

Your body uses a circulatory system to keep everything working.

This system includes your heart, blood, and blood vessels. The heart acts like a pump for your blood. This blood is a fluid made of plasma. It also contains red blood cells, white blood cells, and platelets. Blood carries oxygen and nutrients to your tissues. It also picks up waste materials to carry them away.

The way it works involves two main loops. The first loop is the pulmonary circulation. This loop takes blood from the right side of the heart to the lungs. In the lungs, the blood picks up oxygen. The second loop is the systemic circulation. This loop sends oxygen-rich blood from the left heart to the rest of your body.

It uses a large artery called the aorta to start this journey. The aorta is very thick and elastic. This elasticity helps maintain your blood pressure.

Blood travels through a network of different vessels. It begins in large arteries that move away from the heart. These arteries branch into smaller passages called arterioles. Eventually, the blood reaches tiny tubes called capillaries.

These capillaries are so small that they reach deep into your organs. After passing through capillaries, the blood moves into venules. These small veins join together to form larger veins. These veins eventually carry the blood back to the heart.

An average adult has about five to six quarts of blood. This is roughly 4.7 to 5.7 liters of fluid. This amount of blood is about 7% of a person's total body weight. The human heart has four chambers to manage the flow. These are the left atrium, left ventricle, right atrium, and right ventricle.

The system also includes the lymphatic system. This is an open system that helps move extra fluid. It works with your immune system to protect you from diseases.

This system connects to many other parts of your body. For example, the coronary circulation provides blood to the heart muscle itself. The cerebral circulation sends blood to your brain. The renal circulation handles the blood supply for your kidneys.

Your digestive system also helps by providing nutrients for the blood. Even as a tiny embryo, your body begins building these paths. Fetal circulation starts around the 8th week of development. Before you are born, you get oxygen from your mother through the placenta.

The circulatory system is a complex network of organs and vessels. It includes the heart, the blood, and the blood vessels. This system is vital for maintaining life in vertebrates. It moves oxygen and nutrients to tissues throughout the body. It also collects and removes waste materials. In humans, this is a closed system. This means the blood stays inside the network of vessels at all times.

The system functions through two main circuits. The first is the pulmonary circulation. This loop moves deoxygenated blood from the right side of the heart to the lungs. In the lungs, gas exchange occurs. The blood releases carbon dioxide and absorbs oxygen. The oxygen-rich blood then returns to the left side of the heart. The second circuit is the systemic circulation. This loop delivers oxygenated blood from the left heart to the entire body. It begins with the aorta, which is a massive, thick-walled artery.

Blood travels through various types of vessels. It starts in large, elastic arteries. These arteries branch into smaller passages called arterioles. These lead into capillaries, which are tiny vessels. In a 70 kg human, muscle capillaries can reach 9,000 to 19,000 km in length.

Capillaries connect the arterial system to the venous system. After passing through capillaries, blood enters venules. These small veins merge into larger veins. Eventually, blood returns to the heart through the superior and inferior venae cavae.

The human heart manages these flows using four chambers. There is a left atrium and a left ventricle. There is also a right atrium and a right ventricle. The right atrium receives deoxygenated blood from the venae cavae. This blood flows through the tricuspid valve into the right ventricle. The right ventricle then pumps it through the pulmonary semilunar valve. This sends the blood into the pulmonary artery. The left side of the heart handles the oxygenated blood from the lungs. This blood enters the left atrium and moves into the left ventricle. From there, it is pumped into the aorta.

Blood itself is a specialized fluid. It consists of plasma, red blood cells, white blood cells, and platelets. Plasma carries nutrients like proteins and minerals. It also transports hormones and gases. Red blood cells contain hemoglobin to carry oxygen. White blood cells help the immune system fight disease. Platelets are also present in the fluid. An average adult has about 4.7 to 5.7 liters of blood. This amount represents roughly 7% of total body weight.

Specific regions of the body have dedicated circulatory routes. The coronary circulation supplies the heart muscle itself. It begins with the right and left coronary arteries near the aorta. The cerebral circulation supplies the brain. It uses an anterior circulation from the carotid arteries and a posterior circulation from the vertebral arteries. These join at the circle of Willis. The renal circulation supplies the kidneys. This receives about 20% of the total cardiac output. There is also the hepatic portal vein. This carries blood from the gastrointestinal tract to the liver.

The lymphatic system is a vital subsystem of the circulatory system. It is an open system, unlike the closed blood system. It carries lymph through a network of vessels and nodes. Its main job is to drain interstitial fluid from tissues. This fluid is then returned to the blood circulation. Without this, the blood would become depleted of fluid. The lymphatic system also works with the immune system to fight pathogens. This process of lymph circulation takes much longer than blood circulation.

Development of this system begins in the embryo through vasculogenesis. The arterial system develops from the aortic arches. Specifically, arches 3, 4, and 6 contribute to the system. The venous system arises from three bilateral veins during weeks 4 to 8. Fetal circulation begins around the 8th week of development. During this stage, the lungs are bypassed via the truncus arteriosus. The fetus receives oxygen and nutrients from the mother through the placenta and umbilical cord.