Digestive
Processes
Digestion is a primary function for all living things and is not only
essential to life but its quality will play a major role in our overall
health and resistance to disease. Until recently it was thought that unless
a medical problem existed the digestive system was functioning normally.
We now know that this complex process can be affected by many internal
and external factors and digestive problems are the starting point for
a host of serious conditions and diseases. Approximately 40% of the population
suffers from some digestive complaint making digestive problems the leading
cause of hospitalization in the US. One of the most serious consequences
of untreated digestive symptoms is Colon Cancer, the third most frequent
cancer in the US. The digestive system not only sustains us with the nutrients
we need but acts as the second most important (after the skin) element
of our immune systems.
The food we consume is not in a form that
the body can use as nourishment. It must be broken down into smaller molecules
of nutrients before these nutrients can be absorbed into the blood and
carried to cells throughout the body. Digestion is this process of breaking
down food into its smallest parts so that the body can use them to build
and nourish cells and to provide energy. In this section we will look
at how this process occurs.
Digestive
Tract
The process
of digestion takes place through both physical and chemical transactions.
In the physical sense, food moves through the tract at a pace slow enough
for each organ to perform its specific function and prepare the food for
the next organ, but fast enough for proper absorption to take place. In
a chemical sense, food particles are broken down to allow for passage
from the tract into the bloodstream. The main part of the digestive breakdown
takes place in the digestive (or gastrointestinal) tract which is a series
of hollow organs joined in a long, twisting tube (about 30 feet long)
that begins with the mouth and ends with the anus. The intestinal tract
is located in the body’s abdomen and consists of the mouth, esophagus,
stomach, small intestine, large intestine and rectum and anus. Food is
moved through the esophagus, stomach and intestine by a wave like movement
called peristalsis. In peristalsis the muscle of each organ produce a
narrowing or contraction that pushes the food and fluid in front of it
slowly down the length of the organ and into the next organ. As the food
is being moved through the digestive tract tiny glands in the mucosa or
lining of the digestive organs secrete enzymes and other substances which
help to digest the food.
Mouth
and Throat
The process of breaking down food begins in the mouth where even at the
thought of food 6 salivary glands located around the mouth and face start
producing enzymes that can digest starches. When we consume food the teeth
chew it into smaller particles and it is coated with saliva containing
these enzymes. Some salivary enzymes also attack and protect us against
harmful bacteria which can be contained in the food. Once the food is
chewed it is swallowed and enters the esophagus. Although we are able
to start swallowing by choice, once the swallow begins, it becomes involuntary
and proceeds under the control of the nerves.
Esophagus
The esophagus or gullet, the organ into which the swallowed food is pushed,
is a muscular tube connecting the throat above with the stomach below.
Food is pushed through the esophagus by the muscle contractions of peristalsis.
At the junction of the esophagus and stomach, there is a ring like 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.
Stomach
Once the food mass is transferred to the stomach the thick muscles of
the stomach walls contract to mash the food into a soupy mixture. At the
same time
Hydrochloric Acid (HCI) is secreted providing the highly acidic environment
necessary for the enzyme pepsin to break down proteins. The acidity also
helps prevent infection by destroying most parasites and bacteria. Very
little actual absorption is occurring at this point. The mucous cells
of the stomach can absorb some water, short-chain fatty acids and certain
drugs such as alcohol and aspirin but the main function of the stomach
is preparation of the food for digestion by mixing and liquefying it,
breaking down protein and eliminating harmful bacteria and parasites.
Small
Intestine
The small intestine resembles a coiled hose of about 20 feet in length.
The interior walls of the small intestine are lined with finger like projections
called villi that actually absorb the nutrients. After the stomach empties
the food mixture into the small intestine, the juices of two other digestive
organs mix with the food to continue the process of digestion. One of
these organs is the pancreas. It produces a juice that contains a wide
array of enzymes to break down the carbohydrate, fat, and protein in food.
The other, the liver, produces yet another digestive juice--bile. The
bile is stored between meals in the gallbladder. At mealtime, it moves
from the gallbladder into the bile ducts and into the intestine. The bile
acids dissolve fats so they can be further digested by enzymes from the
pancreas and from the lining of the intestine itself. At this point the
food mixture or “chime” makes up about 60% of the mass that
traveling through the intestinal tract. The rest of the mixture is made
up of mucous and bacteria. Here in the small intestine is where the absorption
phase of digestion takes place. 90% of nutrients such as minerals, vitamins,
carbohydrates and proteins, fat, cholesterol and bile salts, are absorbed
and transferred into the bloodstream at this stage of the digestive process
Large
Intestine
The remaining (and if the digestive tract is healthy) largely indigestible
mixture is then moved into the 5 foot long large intestine or colon where
liquid is extracted any remaining nutrients are absorbed and feces are
formed. 2/3 of stool is water, undigested fiber and food products and
1/3 is dead bacteria which naturally live in the colon. Bacteria play
an essential role in digestion. A substantial percentage live in the large
intestine which could contain as much as 4 lbs. of bacteria. The healthy
digestive system should have a ratio of at least 80-85% good and neutral
bacteria and not more that 15-20% pathogenic or harmful bacteria. The
good bacteria are called “flora” or “probiotics”
and act to:
· produce enzymes that help digest foods
· produce vitamin B, A & K
· produce lactic acid to help acidify the colon
· fight pathogenic bacteria and prevent infection
· produce organic acids that may help with fecal elimination by
peristalsis
· produce short-chain fatty acids which help rebuild intestinal
cells.
Rectum
and Anus
The end of the large intestine and the next part of the tract, the rectum,
store the stool until these are finally squeezed through a ring of muscle,
the anus, and eliminated from the body in a bowel movement.
Click on links below
for additional information on:
Digestive Problems
Relief from Digestive Symptoms
Irritable Bowel Syndrome
Diarrhea
Constipation
Probiotics
Digestive Enzymes
Fiber
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