There are four basic stages to the digestive process: First, food is ingested through the mouth and enters the tubular channel called the alimentary canal, also called the gastrointestinal tract. The gastrointestinal (GI) tract extends from the mouth to the anus, and includes the mouth, esophagus, stomach, small intestine, and large intestine. Second, as food passes down the GI tract it is digested, or broken down into smaller units. Third, these smaller units of nutrients are then absorbed, meaning that they pass into the bloodstream or lymphatic system, which transports them throughout the body. Lastly, anything left over is excreted through the opening (the anus) at the other end. (INFOGRAPHIC 3.2)

Question 3.2

The primary function of the digestive system is to digest, or break down, the nutrients in our foods into compounds that are small enough to be taken up into our body. The inside space of the GI tract is called the lumen, which is lined with a layer of mucosal cells called the mucosa, so named because it is protected by a layer of thick fluid called mucus. Mucosal cells allow our body to absorb nutrients, so that they can be transported by the blood or lymph to where they are needed.

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Over time, the digestive problems caused by celiac disease can predispose individuals to an early death, as Murray discovered in his research. Between 1948 and 1952, a group of researchers collected blood samples from young Air Force recruits in Wyoming—roughly 9,000 in total. Afterward, one of the researchers stuck the thousands of samples in the back of a freezer in Ohio, where drops of water from a condenser created a frozen, hermetic seal over the container, preserving them perfectly. Decades later, they were passed on to Murray, who tested them for levels of certain types of antibodies that indicate the body is reacting to gluten. Among other things, Murray discovered that men who carried the antibodies as young recruits were several times more likely to have died over the subsequent decades than men who didn’t.

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What goes wrong, digestively, in patients with celiac disease and how does this threaten their long-term health? Let’s walk through the digestive process in greater detail to find out.

As mentioned, the GI tract extends from the mouth to the anus and includes the mouth, esophagus, stomach, small intestine, and large intestine. Because many of these organs fold over onto themselves within the body, the entire GI tract is much longer than it appears—in fact, it extends for approximately 8 to 9 meters (26 to 30 feet).

The digestive system includes the organs of the GI tract and accessory organs: the salivary glands, liver, gallbladder, and pancreas, all of which secrete fluids containing a variety of agents, such as enzymes and acids, that aid in digestion. (INFOGRAPHIC 3.3)

Question 3.3