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The essential components of the human cardiovascular system are the heart, blood and blood vessels. It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated; and the systemic circulation, a "loop" through the rest of the body to provide oxygenated blood.
Bone is not a static part of the body — it's constantly being resorbed (broken down) and formed throughout your life. Your entire skeleton is replaced about every decade, according to the NIH. During your childhood and teenage years, bone formation occurs more quickly than bone resorption, resulting in growth. You reach your maximum bone density and strength around age 30, after which bone resorption slowly overtakes bone formation. Osteoporosis develops when there's an abnormal imbalance between bone resorption and formation — that is, resorption occurs too quickly, or formation too slowly.
Upper gastrointestinal bleeding (sometimes upper GI, UGI bleed, Upper gastrointestinal hemorrhage, gastrorrhagia) refers to bleeding in the upper gastrointestinal tract, commonly defined as bleeding arising from the esophagus, stomach, or duodenum. In fact, the proportion of UGIB cases caused by peptic ulcer disease has declined, a phenomenon that is believed to be due to the use of proton pump inhibitors (PPIs) and H pylori therapy. Duodenal ulcers are more common than gastric ulcers, but the incidence of bleeding is identical for both.