When blood circulates in the body, it enters the heart through the right atrium, passes through to the right ventricle, and flows out through the pulmonary artery to the lungs, where it picks up oxygen and gets rid of carbon dioxide.From the lungs, blood returns to the left atrium and then enters the left ventricle, where it is pumped to the body through the aorta.
Did you know that your blood is alive?Approximately 55% of blood is plasma, a straw-colored, clear liquid that transports blood cells, microbe-fighting antibodies, and platelets that cause blood to clot.Although plasma is 90% water, it also contains dissolved salts and minerals such as calcium, sodium, magnesium, and potassium.
Blood vessels may be tiny but they cover a lot of ground. The smallest blood vessels measure only five micrometers. To give you some perspective, a strand of human hair measures about 17 micrometers. But if you took all the blood vessels out of an average child and laid them out in one line, the line would stretch over 60,000 miles. An adult’s would be closer to 100,000 miles long.There are three kinds of blood vessels: arteries, veins, and capillaries. Each of these plays a very specific role in the circulation process. Arteries carry oxygenated blood away from the heart. They’re tough on the outside but they contain a smooth interior layer of epithelial cells that allows blood to flow easily. Arteries also contain a strong, muscular middle layer that helps pump blood through the body. Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart. Veins carry the blood back to the heart. They’re similar to arteries but not as strong or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.)
When germs appear, white blood cells have a variety of special tactics that deploy to knock out the invaders. In some cases, they produce protective antibodies to overpower the germs. Other times, white blood cells surround and devour the bacteria.. They have a rather short life cycle, surviving only a few days to a few weeks.But don’t let that number give you the impression that white blood cells are fragile. They have strength in numbers: A drop of blood can contain anywhere from 7,000 to 25,000 white blood cells at a time. That number may increase if an invading infection persists. Extra Corner:Even with all of their disease-fighting power, having too many white blood cells can actually be a bad thing. For example, a person suffering from Leukemia, a cancer of the blood, may have as many as 50,000 white blood cells in a single drop of blood.
Red blood cells help the body by transporting oxygen. They also contain a protein called hemoglobin. Hemoglobin contains iron which combines with oxygen to give hemoglobin and our blood, a red color. Red blood cells develop in bone marrow and circulate in the body for around 120 days. Extra Corner: Over 17 million red blood cells are created every second. The average human adult body produces 200 billion red blood cells a day which replaces the 200 billion red blood cells that die each day. red blood cells does not have a nucleus. [Nucleus is responsible for reproduction of a cell and contains genetic information]
To the naked eye, everyone’s blood looks the same. But if you look at blood samples under a microscope, it’s obvious that there are some big differences.An Austrian scientist named Karl Landsteiner was the first person to explore this discovery in 1909. He noticed two distinct chemical molecules that were sometimes present on the surface of the red blood cells. He labeled one molecule "A" and the other molecule "B." From there, he began labeling blood types. We still use this system today.Here’s how it works:If a red blood cell has only "A" molecules on it, it is type A.If a red blood cell has only "B" molecules on it, it is type B.If a red blood cell has a mixture of both molecules, it is type AB.If a red blood cell has neither molecule, it is type O.
Scientists sometimes study Rhesus monkeys to learn more about the human anatomy. Why? Because there are certain similarities between the two species.A specific blood protein was discovered in Rhesus monkeys that is also present in the blood of some people. The presence of the protein, or lack of it, is referred to as the Rh factor.If your blood contains the protein, your blood is said to be Rh positive (Rh+). If your blood does not contain the protein, your blood is said to be Rh negative (Rh-).This Rh factor is connected to your blood type. For example, your blood may be AB+ which means that you have type AB blood with a positive Rh factor. Or, you might have O- blood which means that you have type O blood with a negative Rh factor.