Digestive
System
What happens during digestion
How digestion works
Digestive system problems
In digestion, foods are broken down and absorbed as
nourishment or eliminated as waste
• Digestive system functions can be divided into three
main processes:
• Digestion is the mechanical and chemical breakdown of
foods within the stomach and intestines for use by the
body’s cells
• Absorption is the passage of digested food from the
digestive tract into the cardiovascular system
• Elimination is the body’s expulsion of undigested food
or body wastes
The digestive system consists of the mouth, esophagus,
stomach, and intestines.
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Digestion includes two processes: mechanical process – chewing, mashing
and breaking food down; chemical process involves secretions process
involves secretions produced by digestive organs
Teeth – break the food you eat into smaller pieces; mastication – process
of chewing prepares food to be swallowed
Salivary glands – produce digestive juices, saliva contains an enzyme that
begins to break down the starches and sugars in food into smaller particles
Tongue – prepares chewed food for swallowing for shaping it, uvula small
flap of tissue at the back of mouth, prevents food from entering the nasal
passages; epiglottis, tissue covering the throat, prevents food from entering
the respiratory system
Esophagus – muscular tube about 10-inches long, connects pharynx with
stomach, food moves through the esophagus, stomach and intestine
through peristalsis a series of involuntary muscle contractions that moves
food through digestive system (begins as soon as food is swallowed)
sphincter muscle – circular muscle at the entrance of stomach, allows food
to move from the esophagus into the stomach
• Stomach is hollow, sac-like organ enclosed in a wall of
muscle, flexible, can expand when you eat and has three
task:
• Mixing foods with gastric juices – secretions from the
stomach lining that contain hydrochloric acid and pepsin,
an enzyme that digests protein; hydrochloric acid kills
bacteria taken in with food and creates an acidic
environment for pepsin to do its work; mucus produced
by the stomach forms a protective lining so that the
gastric juices do not harm stomach
• Storing partially digested food and liquid – stomach
holds the food for further digestion before it is moved into
the small intestine
• Moving food into the small intestine – food is digested
in the stomach, it is converted to chyme, a creamy, fluid
mixture of food and gastric juices, peristalsis moves the
chyme into the small intestine through an opening
controlled by another sphincter muscle
• Pancreas produces enzymes that break down the
carbohydrates, fats, and proteins in food, glands in the wall of
the intestine produce other enzymes help this process
• Liver process digestive juice – bile – yellow-green, bitter fluid
important in the breakdown and absorption of fats, bile is
stored in gallbladder between meals, bile acids dissolve the
fats inot the watery contents of the intestine, after fat is
dissolved, it is digested by enzymes from the pancreas and
lining of the intestine
• Small intestine is 20 to 23 feet in length and 1 inch in
diameter; has three parts: duodenum, the jejunum and ileum
• About 90% of all nutrients are absorbed through the small
intestine, inner wall of small intestine contains fingerlike
projections called villi - lined with capillaries that absorb the
nutrients, unabsorbed material leaves the small intestine in
the form of liquid and fiber, moves by peristalsis into large
intestine
• Undigested parts of food – fiber or roughage – pass into the
colon or large intestine, it is about 2.5 inches in diameter and
5 to 6 feet in length, function is to absorb water, vitamins and
salts and to eliminated waste
Digestive problems range from indigestion to acute conditions that
require immediate medical attention.
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Maintain a healthy digestive system eat low-fat, high-fiber foods, wash
hands before preparing or eating meals, eat slowly and chew food
thoroughly, drink at least eight 8-ounce glasses of water a day
• Functional problems:
Indigestion – discomfort in the upper abdomen, sometimes with gas and
nausea, causes by eating to much food, eating too quickly, eating spicy or
high-fat foods or having a stomach disorder or stress
Constipation – causes the feces to become dry and hard, making bowel
movements difficult, causes by not drinking enough water or not consuming
enough fiber to move wastes
Heartburn – burning sensation in the center of the chest may rise up to the
throat, results from acid reflux, or backflow of stomach acid in the
esophagus, caused by using tobacco, alcohol and aspirin, or eating spicy or
greasy foods.
Gas – produced from breakdown of food is normal, excessive gas results in
cramps or an uncomfortable feeling of fullness in the abdomen
Nausea – feeling of discomfort that sometimes precedes vomiting, motion
sickness, pathogens some medications and dehydration
Diarrhea – frequent passage watery feces, caused by bacterial or viral
infections, some medications, a change in eating style, overeating,
emotional turmoil or nutritional deficiencies, dehydration may result with
some episodes.
• Structural problems: some are temporary or easily treated, others
are serious and require immediate medical attentions
tooth decay – makes it difficult to chew food, brushing and flossing
daily can prevent this, along with regular checkups.
gastritis – inflammation of the mucous membrane that lines the
stomach, increase in the production of stomach acid, use of tobacco
or alcohol, bacterial or viral infections, some medications
peptic ulcer – a sore in the lining of the digestive tract, caused by a
bacterial infection or overuse of aspirin, ulcers can cause stomach
bleeding
Gallstones – form when cholesterol in bile crystallizes, they block the
bile duct between the gallbladder and small intestine
Lactose intolerance – inability to digest lactose (type of sugar in milk
and other dairy products) if you are this you do not produce enough
lactase
Appendicitis – inflammation of the appendix, 3-to-4 inch tube at tip of
the large intestine, caused by a blockage or bacterial infection
colitis – inflammation of the large intestine or colon,
caused by bacterial or viral infection
colon cancer – second leading cause of cancer death,
develops in the lowest part of the colon, near the rectum,
a low-fat, high-fiber eating plan decreases risk
hemorrhoids – veins in the rectum and anus may become
swollen and inflamed, occur with constipation, during
pregnancy, and after childbirth
Crohn’s disease – inflammation of the lining of the
digestive tract, cause is unknown, seems to be
associated with immune system problems
cirrhosis – scarring of the liver tissue, caused by
prolonged heavy alcohol use, lead to liver failure and
even death