Mouth to Stomach: Starting the Breakdown

The Story

Digestion begins before the first swallow. In the mouthThe opening of the digestive tract where food enters and mastication begins., teeth shear and grind food into smaller pieces – mechanical digestion – while the salivary glands flood it with saliva, whose enzyme amylase starts breaking down starch and whose mucus binds the result into a slippery bolusA rounded mass of food mixed with saliva that is ready for swallowing.. The tongue pushes that bolus to the pharynxThe muscular passageway connecting the mouth to the esophagus and larynx., and swallowing becomes briefly involuntary: the epiglottisA flap of cartilage that covers the trachea during swallowing to prevent food from entering the airw folds down over the larynxThe voice box; contains vocal cords and connects the pharynx to the trachea. so food takes the correct fork into the esophagusThe muscular tube that transports food from the pharynx to the stomach via peristalsis. rather than the airway. The esophagus then delivers it to the stomach not by gravity but by peristalsis Rhythmic contractions of smooth muscle that move food through the digestive tract. – which is why a person lying flat, or an astronaut, still swallows successfully.

The stomach is a muscular bag that mixes and marinates. Gastric pits in its lining release hydrochloric acidA substance that releases hydrogen ions (H⁺) in solution., bringing the contents to a pHA measure of hydrogen ion concentration in a solution. near 2, and the enzyme pepsin, which begins dismantling proteinsLarge molecules made of amino acids with various functions in the body.; the churning produces a soupy mixture called chymeA semi-fluid mixture of partially digested food and digestive juices that moves from the stomach int. A thick layer of mucus and bicarbonate(HCO₃⁻) – A crucial buffer in blood that helps maintain pH balance; formed when carbon dioxide normally shields the stomach’s own wall from this acid. When that defense is overwhelmed – by reflux of acid up into the esophagus, or by the bacterium Helicobacter pylori or NSAIDs eroding the lining – the result is heartburn or a peptic ulcer. Stina’s chronic heartburn belongs to this everyday category of upper-GI trouble; importantly, it is not the source of her attacks, and learning to separate the two is part of reading her chart correctly.

From Stina’s chart: Stina has chronic heartburn and was treated for years with acid-suppressing drugs – a reminder that the upper tract has its own everyday problems, separate from her attacks.