Initial Processing Digestion begins in the mouth, where mechanical breakdown through chewing combines with chemical digestion by salivary enzymes. The tongue forms food into a bolus while mixing it with saliva containing amylase, which begins carbohydrate breakdown. After swallowing, the esophagus moves food to the stomach through coordinated mu

Red Blood Cells Erythrocytes, or red blood cells, specialize in oxygen transport throughout the body. These unique cells lack nuclei to maximize hemoglobin capacity, the protein responsible for binding oxygen. Each cell contains approximately 280 million hemoglobin molecules, giving blood its red color. Red blood cells live about 120 days, with

Inhalation Mechanics Breathing begins when the diaphragm contracts and moves downward while external intercostal muscles lift the rib cage. These actions increase the chest cavity volume, creating negative pressure that draws air into the lungs. Air moves through the airways - nose or mouth, pharynx, larynx, trachea, and bronchi - before reachin

Electrical Initiation The heartbeat begins in the sinoatrial node (SA node), the heart's natural pacemaker located in the right atrium. This specialized tissue generates electrical impulses that trigger each heartbeat. The electrical signal spreads through the atria, causing them to contract and push blood into the ventricles. The signal then tr