Blood flow through human cardiovascular system? How does it work?

Answer 1

Blood is the fluid that flows through the system. It is pumped by the heart, and circulates through arteries to the tissues, then return to the heart by way of veins. The heart is a muscular organ with four chambers. The right side of the heart pumps blood to the lungs, where they drop off carbon dioxide and pick up oxygen. Then the blood returns to the left side of the heat. It is pumped again, this time to the rest of the body (where it leaves oxygen and nutrients and picks up carbon dioxide and other wastes).

Answer 2

Blood is the fluid that flows through the system. It is pumped by the heart, and circulates through arteries to the tissues, then return to the heart by way of veins. The heart is a muscular organ with four chambers. The right side of the heart pumps blood to the lungs, where they drop off carbon dioxide and pick up oxygen. Then the blood returns to the left side of the heat. It is pumped again, this time to the rest of the body (where it leaves oxygen and nutrients and picks up carbon dioxide and other wastes).
The heart starts its own beat by means of pacemaker cells that depolarize spontaneously to threshold. Then the cells fire an action potential that spreads to all the heart muscle cells, which causes them to contract. While it is self-starting, the heart beat can be modified by the nervous system. For example, if the "flight or fight" syndrome is activated, the heart will beat faster and stronger.

Answer 3

The circulatory system (or cardiovascular system) is an organ system that moves substances to and from cells; it can also help stabilize body temperature and pH (part of homeostasis). While the most primitive animal phyla lack circulatory systems, some invertebrate groups have open circulatory system. Vertebrates have closed circulatory system.
An open circulatory system is an arrangement of internal transport present in some invertebrates such as molluscs and arthropods in which fluid in a cavity called the hemocoel (or haemocoel) bathes the organs directly and there is no distinction between blood and interstitial fluid; this combined fluid is called hemolymph / haemolymph. Muscular movements by the animal during locomotion can facilitate hemolymph movement, but diverting flow from one area to another is limited. When the heart relaxes, blood is drawn back toward the heart through open-ended pores.

Hemolymph fills all of the interior hemocoel of the body and surrounds all cells. Hemolymph is composed of water, inorganic salts (mostly Na+, Cl-, K+, Mg2+, and Ca2+), and organic compounds (mostly carbohydrates, proteins, and lipids). The primary oxygen transporter molecule is hemocyanin.

There are free-floating cells, the hemocytes, within the hemolymph. They play a role in the arthropod immune system.


[edit] Closed circulatory system
The main components of the circulatory system are the heart, the blood, and the blood vessels.

The circulatory systems of all vertebrates, as well as of annelids (for example, earthworms) and cephalopods (squid and octopus) are closed, meaning that the blood never leaves the system of blood vessels consisting of arteries, capillaries and veins.

Arteries bring oxygenated blood to the tissues (except pulmonary arteries), and veins bring deoxygenated blood back to the heart (except pulmonary and portal veins). Blood passes from arteries to veins through capillaries, which are the thinnest and most numerous of the blood vessels and these capillaries help to join tissue with arterioles for transportation of nutrition to the cells.

The systems of fish, amphibians, reptiles, and birds show various stages of the evolution of the circulatory system.

In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as single circulation. The heart of fish is therefore only a single pump (consisting of two chambers). In amphibians and most reptiles, a double circulatory system is used, but the heart is not always completely separated into two pumps. Amphibians have a three-chambered heart.

Birds and mammals show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently of that of mammals.


[edit] Mammalian circulation
De-oxygenated blood enters the right atrium of the heart and flows into the right ventricle where it is pumped through the pulmonary arteries to the lungs. Pulmonary veins return the now oxygen-rich blood to the heart, where it enters the left atrium before flowing into the left ventricle. From the left ventricle the oxygen-rich blood is pumped out via the aorta, and on to the rest of the body.

As blood circulates through the body, oxygen diffuses from the blood into cells surrounding the capillaries, and carbon dioxide diffuses in from those cells. The relatively de-oxygenated blood collects in the venous system which coalesces into two major veins: the superior vena cava (roughly speaking from areas above the heart) and the inferior vena cava (roughly speaking from areas below the heart). These two great vessels empty into the right atrium of the heart. The coronary sinus empties the heart's veins themselves into the right atrium. The right atrium is the larger of the two atria, although both receive the same amount of blood. The blood is then pumped through the tricuspid valve, or right atrioventricular valve, into the right ventricle. From the right ventricle, blood is pumped through the pulmonary semi-lunar valve into the pulmonary artery. This blood enters the two pulmonary arteries (one for each lung) and travels through the lungs, where it is oxygenated and then flows into the pulmonary veins. This oxygenated blood then enters the left atrium, which pumps it through the bicuspid valve, also called the mitral or left atrioventricular valve, into the left ventricle.

From the left ventricle, blood is pumped through the aortic semi-lunar valve into the aorta, a massive and thick-walled artery. The aorta arches and gives off major arteries to the upper body before piercing the diaphragm in order to supply the lower parts of the body with its various branches. Once the blood enters the peripheral tissues oxygen and nutrients are extracted from it and carbon dioxide and wastes added, and it will again be collected in the veins and the process will be repeated. Peripheral tissues do not fully deoxygenate the blood, so venous blood does have oxygen, but in a lower concentration than in arterial blood.

The left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure. The left ventricle pumps blood to the entire body whereas the right ventricle pumps all of its blood directly to the lungs

The release of oxygen from red blood cells or erythrocytes is regulated in mammals. It increases with an increase of carbon dioxide in tissues, an increase in temperature, or a decrease in pH. Such characteristics are exhibited by tissues undergoing high metabolism, as they require increased levels of oxygen.


[edit] No circulatory system
Circulatory systems are absent in some animals, including flatworms (phylum Platyhelminthes). Their body cavity has no lining or or enclosed fluid. Instead a muscular pharynx leads to an extensively branched digestive system that facilitates direct diffusion of nutrients to all cells. The flatworm's dorso-ventrally flatened body shape also restricts the distance of any cell from the digestive system or the exterior of the organism. Oxygen can diffuse from the surrounding water into the cells, and carbon dioxide can diffuse out. Consequently every cell is able to obtain nutrients, water and oxygen without the need of a transport system.