[block]0[/block]PART 1: Our Digestive System
Our digestive system consists of many organs and parts. Each performs its own function while interacting in harmony with others every time we eat. These interesting and complex organs and parts turn the food we eat into specific components we need to fuel, build, maintain, repair, regulate, and protect our bodies.
Muscles, nerves, reflexes, enzymes, and hormones of the digestive tract all work together to change our food into nutrients that can be absorbed into our main transport systems: our bloodstream and our lymph system. These two transport systems then carry fresh supplies of nutrients throughout our body to nourish every individual cell.
Our brain monitors our nutritional needs and employs a hunger mechanism to alert us when fresh food is needed. Hunger causes appetite which is the desire for food. The tempting sight, smell, taste and expectation of food stimulate involuntary sensory nerves. By reflex action, these nerves cause muscle and sensory activity in various digestive organs. Salivary glands begin to secrete saliva as stomach glands and muscles become active.
How Digestion Works – A Walk Through…
First we chew our food. After we chew it, our throat swallows it, and our esophagus transports it to our stomach. Our stomach dissolves and sends it on to our small intestine, where it is digested and absorbed into our blood and lymph systems. Our small intestine then sends the undigestible substances to our large intestine where water is absorbed. Normal bacteria living there go to work on the residue to extract more nutrients, while producing nourishment for our colon and substances for our body. The waste is then sent on to our rectum, which forms it. Finally, our anus expels it.
Now, that we have the basics of digestion, let’s take a closer look. The following is based in part on an excerpt from the The National Digestive Diseases Information Clearinghouse.
Movement of Food Through the System
The first major muscle movement occurs when food or liquid is swallowed. Although we are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.
The large, hollow organs of the digestive system contain muscle that enables their walls to move. The movement of organ walls can propel food and liquid and also can mix the contents within each organ. Typical movement of the esophagus, stomach, and intestine is called peristalsis.
The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.
The esophagus is the organ into which the swallowed food is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike valve closing the passage between the two organs. However, as the food approaches the closed ring, the surrounding muscles relax and allow the food to pass.
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