The right side of your heart takes oxygen-depleted blood from your veins and pumps it to your lungs, where it absorbs oxygen and expel carbon dioxide. The left side of your heart receives oxygen-rich blood from your lungs and transports it to the rest of your body via your arteries. Cells use this oxygen to make energy for their daily activities.
Your skin is a very effective form of protection against noxious substances and extremes in temperature. It also acts as a sensor that alerts you to changes in your environment. Skin has two main functions: protection and communication. It provides protection by preventing contact with harmful chemicals and physical forces such as heat and cold. Communication through skin color helps you identify friends, foes, and potential mates. The color of your skin varies depending on which part of the electromagnetic spectrum you are responding to. Redness or pinkness indicates you are receiving ultraviolet (UV) radiation, which is necessary for life but can be harmful if exposure is too long. White or bluish colors indicate you are seeing near-infrared radiation, which is below the visible light range and is used primarily by plants for photosynthesis. Black or dark brown colors indicate you are detecting far-red and red light, which are required for plant growth and development but not for human activity.
Oxygen is needed by cells to produce energy using an enzyme called oxidase. There are two forms of oxidase: cytochrome c oxidase and NADH oxidase.
The pulmonary artery transports deoxygenated blood to the lungs, where it exchanges oxygen for carbon dioxide. The left atrium This chamber gets oxygenated blood from the lungs' pulmonary veins and pumps it to the left ventricle. The left ventricle The main pumping chamber of the heart sends oxygenated blood through the aorta out to the rest of the body.
The right atrium This chamber gets oxygenated blood from the lungs' pulmonary veins and pumps it into the right ventricle. The right ventricle The main pumping chamber of the heart sends oxygenated blood through the pulmonary vein out to the lungs.
Both atria Heart chambers that receive oxygenated blood from the lungs via the pulmonary artery. The right atrium pumps this blood into the right ventricle, which in turn pumps it into the pulmonary artery when it contracts. The left atrium serves a similar function with respect to the left ventricle.
Both ventricles Main pumping chambers of the heart that send oxygenated blood out to the rest of the body via the aorta and major blood vessels.
The mitral valve controls the flow of oxygenated blood from the left atrium to the left ventricle. It does so by opening when there is an increase in pressure within the left atrium caused by contraction of the myocardium (muscle of the heart).
The right atrium takes oxygen-depleted blood from the body via the superior and inferior vena cava and pumps it to the right ventricle. The tricuspid valve permits oxygen-depleted blood from the right atrium to pass forward to the right ventricle. The pulmonary valve allows only oxygen-rich blood to leave the right ventricle and enter the pulmonary artery. The pulmonary vein then carries this blood to the lungs for replacement with new blood cells.
In severe cases of hypoxia, such as those resulting from high altitude exposure or lung disease, more than one round of breathing is required before enough oxygen reaches the blood to cause tissue damage. This is called "superimposed" or "recapillary" hypoxia.
The human body has a number of adaptations that allow it to function under low oxygen conditions. The most important is the use of oxygen stores in form of hemoglobin in red blood cells. When these are used up, people will eventually become unconscious even when exposed to air with less than 10% oxygen. However something worse can happen if you stay out in these conditions for too long...
People who work or travel above about 5,000 feet (1,524 m) experience milder effects of high altitude because more oxygen is available at higher elevations. At greater heights, however, severe effects occur because there is not enough oxygen at lower levels of activity.
The arteries (red) transport oxygen and nutrients from your heart to the tissues of your body. The veins (blue) transport oxygen-depleted blood back to the heart. The aorta, the major artery that exits the heart, is the starting point for arteries. As it branches into smaller arteries called arterioles, these vessels supply oxygen and nutrients to larger areas of tissue until they reach capillaries at the end of each branch. Here, blood flows through tiny holes called pores to pick up oxygen and deliver it to cells. Capillaries are connected by an extensive network of small vessels called venules. Venules merge together to form larger veins that return blood to the heart.
Arteries are hollow tubes that carry blood away from the heart. Arteries are made up of three layers: an intima, media, and adventitia. The intima is the layer closest to the heart; it contains endothelial cells (flat cells that line all blood vessels). The media consists of smooth muscle cells wrapped around bundles of collagen fibers. The adventitia provides support for the artery and contains fibroblasts that produce more collagen to create a stronger vessel wall.
Veins are the blood vessels that carry blood back to the heart. Veins consist of two thick layers: an intima and a muscular layer. The intima is similar to that of an artery; it contains endothelial cells (flat cells that line all blood vessels).
The circulatory system transports waste and supplies oxygen and nutrients to cells. The heart alternately pumps oxygenated and deoxygenated blood. There are three types of blood vessels: arteries, capillaries, and veins. Arteries carry oxygenated blood from the heart to other organs or to the lungs, where carbon dioxide is removed and fresh air is supplied through the process of breathing. Veins return blood to the heart from other tissues where it was needed. Capillaries are very small blood vessels that connect arteries and veins. They provide a continuous flow of blood between the two groups of vessels. The word "capillary" comes from a Latin word meaning "little jar," because these vessels were originally thought to be filled with fluid.
Oxygen and nutrients are transported to cells by means of carrier proteins called globulins. These proteins bind to specific receptors on the surface of cells. Once a protein has bound its cargo, it can be released into the bloodstream at a later time when another cell needs it. Human serum albumin is the major plasma protein that carries oxygen and nutrients to cells. It is also responsible for removing toxic substances from cells. Albumin has a high affinity for fatty acids and drugs and can therefore remove them from the body. Other important carriers include transferrin for iron, vitamin B12, and insulin.
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