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Department of foreign language
PRESENTATION
The theme: Great discoveries in the digestive system. Diseases of digestive system
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Plan
Description of the digestive system
Diseases of the digestive system
Used literature
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Description of the digestive system
Also known as the gastrointestinal (GI) tract, the digestive
system begins at the mouth, includes the esophagus, stomach,
small intestine, large intestine (also known as the colon) and
rectum, and ends at the anus. The entire system — from mouth
to anus — is about 30 feet (9 meters) long, according to the
American Society of Gastrointestinal Endoscopy (ASGE).
Digestion begins with the mouth. Even the smell of food can
generate saliva, which is secreted by the salivary glands in the
mouth, contains an enzyme, salivary amylase, which breaks
down starch. Teeth, which are part of the skeletal system, play
a key role in digestion. In carnivores, teeth are designed for
killing and breaking down meat. Herbivores’ teeth are made for
grinding plants and other food to ease them through the
digestion process
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Swallowing pushes chewed food into the
esophagus, where it passes through the
oropharynx and hypopharynx. At this point, food
takes the form of a small round mass and
digestion becomes involuntary. A series of
muscular contractions, called peristalsis,
transports food through the rest of the system.
The esophagus empties into the stomach,
according to the National Institutes of Health
(NIH).
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The stomach’s gastric juice, which is primarily a mix of hydrochloric acid and pepsin, starts breaking down
proteins and killing potentially harmful bacteria, according to ASGE. After an hour or two of this process, a
thick semi-liquid paste, called chyme, forms.
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At this point the pyloric sphincter valve opens and
chyme enters the duodenum, where it mixes with
digestive enzymes from the pancreas and acidic bile
from the gall bladder, according to the Cleveland
Clinic. The next stop for the chyme is the small
intestine, a 20-foot (6-meter) tube-shaped organ,
where the majority of the absorption of nutrients
occurs. The nutrients move into the bloodstream and
are transported to the liver.
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The liver creates glycogen from sugars and
carbohydrates to give the body energy and converts
dietary proteins into new proteins needed by the
blood system. The liver also breaks down unwanted
chemicals, such as alcohol, which is detoxified and
passed from the body as waste, the Cleveland Clinic
noted.
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Whatever material is left goes into the large intestine. The
function of the large intestine, which is about 5 feet long (1.5
meters), is primarily for storage and fermentation of
indigestible matter. Also called the colon, it has four parts: the
ascending colon, the transverse colon, the descending colon
and the sigmoid colon. This is where water from the chyme is
absorbed back into the body and feces are formed primarily
from water (75 percent), dietary fiber and other waste
products, according to the Cleveland Clinic. Feces are stored
here until they are eliminated from the body through
defecation.
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Many symptoms can signal problems with the GI tract,
including: abdominal pain, blood in the stool, bloating,
constipation, diarrhea, heartburn, incontinence, nausea and
vomiting and difficulty swallowing, according to the NIH.
Among the most widely known diseases of the digestive system
is colon cancer. According to the Centers for Disease Control
(CDC), 51,783 Americans died from colon cancer in 2011 (the
most recent year for available data). Excluding skin cancers,
colon and rectal cancer, or colorectal cancer, is the third most
common cancer diagnosed in both men and women in the
United States, according to the American Cancer Society.
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Polyp growth and irregular cells, which may or may not be
cancerous, are the most common development paths for
colorectal cancers (also referred to as CRC), and can be
detected during a routine colonoscopy, according to Dr. John
Marks, a gastroenterologist affiliated with the Main Line Health
health care system.
“ The best news is that, if caught early enough, they can also be
removed during the colonoscopy — eliminating the possibility
that they grow further and become cancer,” Marks said.
For those patients whose cancer has already spread, there are
various minimally invasive surgical options that have extremely
good prognoses. It is recommended that asymptomatic
patients without a family history begin getting tested regularly
between the ages 45 and 50, according to Marks. “Symptoms
which may suggest that you need a colonoscopy at an earlier
age include rectal bleeding and stool/bowel habit changes
which last for more than a few days.”
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While CRC gets a great deal of attention, many diseases
and conditions of the digestive system — including
irritable bowel syndrome, diverticulitis, GERD (acid reflux)
and Crohn’s disease — can be chronic and are difficult to
diagnose and treat, according to Dr. Larry Good, a
gastroenterologist affiliated with South Nassau
Communities Hospital. “With many of these diseases,
blood work and colonoscopies all looks normal, so there
is an absence of red flags.”
Many of the diseases of the digestive system are tied to
the foods we eat, and a number of sufferers can reduce
their symptoms by restricting their diets, Good said. “Of
course no one wants to hear that they can’t eat certain
foods, but many times, eliminating acidic things from the
diet, such as tomatoes, onions, and red wine, can have an
impact,” Good said.
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Used literature
https://www.livescience.com/22367-digestive-system.html
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