Enteroendocrine cells secrete various hormones. However, not all stomach glands contain every type of cell. Gastric juice is made up of water, electrolytes, hydrochloric acid, enzymes, mucus, and intrinsic factor. Hydrochloric acid is a strong acid secreted by the parietal cells, and it lowers your stomach's pH to around 2.
Hydrochloric acid converts pepsinogen into pepsin and breaks various nutrients apart from the food you eat. It also kills bacteria that comes along with your food.
Pepsinogen is secreted by chief cells, and when it's in the presence of hydrochloric acid, it's converted to pepsin. Pepsin breaks apart tertiary and secondary protein structures to make it easier for the digestive enzymes in the small intestines to work later.
Gastric lipase is another digestive enzyme made by the chief cells. It helps break down short and medium chain fats. Amylase is also found in gastric juices, but it isn't made by the stomach.
This enzyme comes from saliva and travels along with the bolus into the stomach. Amylase breaks down carbohydrates, but it doesn't have much time to work on the stomach because the acidity stops it.
That's okay, though, because your small intestine introduces more amylase later on. The mucus is secreted by the neck cells and helps coat and protect your stomach lining from the acid environment.
Intrinsic factor is secreted by parietal cells and is necessary for your body to absorb vitamin B This is essential for healthy nervous system function and blood cell production. Your stomach muscles squeeze and churn to mix the bolus with all of these digestive juices. The liquid mixture is called chyme. When it's ready, your stomach squirts the chyme into the small intestine where digestion continues and absorption of those all-important nutrients occurs.
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Food is enclosed in your stomach by two circular muscles, known as sphincters. As soon as food enters your stomach, your stomach lining releases enzymes that start breaking down proteins in the food. Your stomach lining also secretes hydrochloric acid, which creates the ideal conditions for the protein-digesting enzymes to work. The potent hydrochloric acid kills bacteria, protecting your body from harmful microbes which can enter your body in food.
Your stomach protects itself from being digested by its own enzymes, or burnt by the corrosive hydrochloric acid, by secreting sticky, neutralising mucus that clings to the stomach walls. If this layer becomes damaged in any way it can result in painful and unpleasant stomach ulcers. Waves of muscular contraction along your stomach wall, known as peristalsis, break food down into smaller pieces, mix it with fluids secreted from your stomach lining and move it through your stomach.
This creates a mixture that resembles thick cream. When food has been broken down sufficiently, small amounts are squirted out of your stomach into your small intestine for further processing. This normally occurs within four hours of eating a meal, but can take six or more hours if your meal has a high fat content.
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