NUTR 2105 Lecture Notes - Lecture 3: Heartburn, Small Intestine, Peristalsis
1 May 2018
School
Department
Course
Professor
Process and organs involved in digestion?
Digestion: process of breaking down food into individual molecules small
enough to be absorbed through intestinal wall
○
Absorption: process of moving nutrients from GI tract into circulatory
system
○
Transport: process of moving absorbed nutrients throughout body through
the circulatory and lymph systems
○
Elimination: excretion of undigested and unabsorbed food through feces
Organs of GI tract:
Made of 5 organs:
Mouth
Mechanical digestion: chewing, grinding,
squeezing, and moving food through GI tract
through peristalsis and segmentation
◊
Chemical digestion: breaking down food through
enzymatic reactions
Saliva
Dissolves small food particles
–
Contains the enzyme amylase which
breaks down carbs
Prevents cavities
w
–
}
Once food is chewed and moistened, tongue
rolls it into a bolus and it enters pharynx to
be swallowed (enters esophagus)
}
◊
®
Esophagus
Transports food and fluids to stomach
◊
2 sphincters in esophagus:
Upper esophageal sphincter: allows the
bolus of food to enter esophagus
}
Lower esophageal sphincter (LES): allows the
bolus of food to enter stomach
When relaxes: acid reflux (heart burn)
–
}
◊
®
Stomach
mixes food w/ various gastric juices to chemically
break it down into smaller pieces
◊
Mechanical digestion when muscles mix, churn,
and push contents w/ gastric juices
◊
When empty stomach holds 1 cup but can expand
up to holding 1 gallon
◊
Chyme: the semiliquid, partially digested food
mass that leaves the stomach and enters the small
intestine
Pyloric sphincter is the gateway for food for
this passage
}
◊
®
Small intestine
Where most of the action takes place
Mechanical and chemical digestion
Muscular digestion to push chyme
forward
–
Digestive secretions break down
nutrients
–
}
Surface is lined w/ villi to maximize
absorption
}
Contact time is 3 to 10 hours depending on
food eaten
}
◊
3 segments (don't really need to know)
Duodenum
}
Jejunum
}
Ileum
}
◊
®
Large intestine
Most absorption is already done at this point
Absorbs water and some nutrients though
(water, sodium, potassium, and chloride)
}
◊
Chyme enters the large intestine through the
ileocecal valve
◊
3 segments (whole thing is 5 feet long and 2.5
inches)
Cecum: beginning part
}
Colon: largest part
}
Rectum: final 8- inch part
}
◊
Intestinal matter spends 12 to 70 hours in large
intestine depending on the person's health, age,
diet, and fiber intake
◊
®
□
Sphincters allow food to pass from one organ to the next□
Accessory organs outside the GI tract aid in digestion (by
secreting digestive juices)
Salivary glands
Dissolve small food particles to ease the process of
swallowing food
◊
Contains water, mucus, electrolytes, and a few
enzymes
◊
®
Liver
Largest internal organ in the body (weighing 3
pounds)
◊
Major player in digestion, absorption, and
transport of nutrients
◊
Essential in carb metabolism
◊
Makes proteins
◊
Produces bile (salts) which digest fat
◊
Site of alcohols metabolism and removes and
degrades toxins and excess hormones
◊
®
Gallbladder
Receives bile from liver via common hepatic duct1.
Concentrates bile2.
Releases bile into small intestine via common bile
duct
3.
®
Pancreas
Endocrine function: releases hormones to
maintain blood glucose levels
◊
Exocrine function: secretes digestive enzymes into
the small intestine
◊
®
□
§
○
-
Food is propelled through GI tract by strong muscular contractions
2 primary contractions:
Peristalsis: squeezes food forward through the GI tract
Mechanical digestion□
§
Segmentation: shifts food back and forth along the GI tract in the
intestines
Allows contact w/ surface of small and large intestines and
increases absorption
□
§
○
-
How food is chemically digested
Enzymes are proteins that drive the process of digestion
Catalyze (speed up) hydrolysis which the chemical reaction that uses
water to split chemical bonds of digestible nutrients
§
3 conditions required for enzymes to work:
Compatible enzyme and nutrient 1.
The pH of surrounding environment must be in a correct range
If not, enzyme activity is decreased or halted b/c enzyme
(protein) will be denatured
a)
2.
Temp must be optimal
Same as 2aa)
3.
§
○
Secretions of the GI tract
HCl:
Secreted in stomach□
Denature/ activate proteins/ enzymes□
§
Mucus
Protection from acid (stomach and SI)□
§
Bicarbonate- will ask what it does
Secreted by pancreas□
Neutralize acidic chyme (raise pH) ** will ask if raise or lower
pH
□
§
Bile
Produced in liver□
Emulsifies (like kind of mixing oils) fat for digestion□
§
○
How nutrients are absorbed
In small intestine
Passive diffusion: nutrients move high to low concentration, no
energy required
□
Facilitated diffusion: nutrients move high to low concentration
w/ the help of a carrier protein; no energy required
□
Active transport: nutrients move low to high concentration w/
the help of a carrier protein; energy required
□
Endocytosis: cell forms a vesicle to surround and engulf a
nutrient
□
§
In large intestine
Majority of nutrients absorbed when chyme enters large
intestine
Water and salt absorbed in large intestine
®
Some mechanisms in small intestine also used in large
intestine
Water: passive diffusion
◊
Sodium: active transport
◊
®
□
§
○
-
How hormones and N.S. regulate digestion
By controlling:
Release of gastric and pancreatic secretions
§
Peristalsis
§
Enzyme activity
§
○
Enterogastrones are produced and secreted by the cells lining the stomach
and small intestine
Influence GI motility, stomach emptying, gallbladder contraction,
intestinal absorption, and hunger
§
Release of hormones is stimulated by types of foods passing through
digestive tract
§
○
Types of hormones
Gastrin: stimulates HCl production and release of gastric enzymes
§
Secretin: stimulates pancreas to release bicarbonate to small
intestine (increases pH)
§
Cholecystokinin (CCK): when fat, stimulates pancreas to release
lipase and gallbladder to release bile
§
Gastrin inhibitory peptide (GIP): inhibits gastric motility and stomach
secretions
§
○
N.S. communicates w/ GI tract
Tells you when to eat and drink, and when to stop
Extrinsic nerves:
Communicate changes in GI tract and stimulate mobility
®
Originate in brain or spinal cord
®
□
Intrinsic nerves:
Receive message from extrinsic nerves and respond by
stimulating release of digestive juices
®
Interwoven in linings of esophagus, stomach, and small
and large intestines
®
□
§
2 main hormones
Ghrelin: triggers hunger
When people go on diets, this increases
®
□
PYY: satiety/ fullness hormone□
§
○
-
How nutrients transported through body:
Water-soluble nutrients absorbed into cardiovascular system through
hepatic portal vein to liver
Carbs, amino acids, water-soluble vitamins
§
○
Fat-soluble nutrients absorbed into lymphatic system
Fat-soluble vitamins, long-chain fatty acids, and proteins that are too
big to be transported via capillaries
§
○
Waste products removed via excretory system
○
Kidneys filter blood, allowing waste products to be concentrated in urine
and excreted
○
-
Common digestive disorders
Esophageal problems
Gastroesophageal reflux disease (GERD) aka indigestion or acid reflux
LES (lower esophageal sphincter) doesn't close properly, or
relaxes, and allows HCl from stomach into esophagus
□
Behavior modifications
Change what eat (sometimes take tums), or even
eliminate certain foods
□
Smoking and drinking relaxes LES (lower esophageal
sphincter)
□
Also wearing tight clothes, like skinny jeans□
Don't lay down after eat, or if you do prop yourself up□
□
§
Esophageal cancer
One of the most common cancers of digestive tract□
More common in males over 50, living in urban areas, who
smoke and drink heavily
□
Treatment: typical cancer treatment□
§
○
Disorders of stomach
Belching (burping)
Swallowing amounts of air
Eating too fast, drinking soda, anxiety, chewing gum,
smoking
□
□
§
Stomach flu
Symptoms: nausea, vomiting, diarrhea, and abdominal
cramping
□
Treatment: rest, rehydration, and eating soft foods□
§
Foodborne illness
Consuming food or drink w/ a pathogenic microbe such as E.
Coli, Salmonella, or Campylobacter
□
Most are self-limiting and need rest and rehydration□
§
Ulcers
Sore or erosion in lining of lower region of stomach or upper
part of duodenum
□
Helicobacter pylori, bacterium, often involved□
Symptoms: fatigue, bleeding, general weakness, burning pain□
Treatment: rx drugs, dietary changes, and/ or surgery□
If untreated: peritonitis, scar tissue can obstruct food and
cause vomiting and weight loss, and greater risk for cancer
□
§
Gallbladder disease
Most often in woman and older Americans□
Can create gallstones□
§
Celiac disease
Autoimmune disorder to small intestine when consume gluten
Causes villi to flatten out, causing nutrient malabsorption□
□
Can lead to increased risk for osteoporosis, diminished growth,
seizures
□
Diagnosis via blood test and tissue biopsy of small intestine□
Only treatment is cutting out all gluten□
§
○
Other kinds of intestinal disorders
Flatulence: release of gas
Via
Foods high in fiber and starch□
Eating quickly□
Drinking carbonated beverages□
Lack of exercise□
Smoking□
□
§
Diarrhea
Treatment: fluid and electrolyte replacement□
§
Constipation
Treatment: exercise, normal eating patterns, and rest□
Laxatives used sparingly□
§
Hemorrhoids: swelling of veins of rectum and anus
Cause is unknown□
Treatment includes fiber and fluid intake□
§
Irritable bowel syndrome (IBS)
Having GI issues but not really sure what so lumped together□
§
Ulcerative colitis
Chronic inflammation of large intestine, resulting in ulcers in
lining of colon
□
Hereditary□
In men and women, beginning ages 15-30□
No cause or cure□
Treatment: drug therapy and surgery□
§
Crohn's disease: similar to ulcerative colitis, but ulcers can occur
throughout GI tract
No cause or cure□
Treatment: drug therapy or possibly surgery□
§
Colon cancer: third leading cause of cancer death, but most curable if
caught early
Begins w/ polyps (clump of cells in colon that mostly are small
and benign but can turn into cancer), that can be surgically
removed
□
Treatment: typical cancer treatment□
Survival depends on age, treatment response, and stage of
cancer diagnosis
□
§
○
-
NUTR 2105 Chpt. 3
Monday, January 22, 2018
2:13 PM
Process and organs involved in digestion?
Digestion: process of breaking down food into individual molecules small
enough to be absorbed through intestinal wall
○
Absorption: process of moving nutrients from GI tract into circulatory
system
○
Transport: process of moving absorbed nutrients throughout body through
the circulatory and lymph systems
○
Elimination: excretion of undigested and unabsorbed food through feces
Organs of GI tract:
Made of 5 organs:
Mouth
Mechanical digestion: chewing, grinding,
squeezing, and moving food through GI tract
through peristalsis and segmentation
◊
Chemical digestion: breaking down food through
enzymatic reactions
Saliva
Dissolves small food particles
–
Contains the enzyme amylase which
breaks down carbs
Prevents cavities
w
–
}
Once food is chewed and moistened, tongue
rolls it into a bolus and it enters pharynx to
be swallowed (enters esophagus)
}
◊
®
Esophagus
Transports food and fluids to stomach
◊
2 sphincters in esophagus:
Upper esophageal sphincter: allows the
bolus of food to enter esophagus
}
Lower esophageal sphincter (LES): allows the
bolus of food to enter stomach
When relaxes: acid reflux (heart burn)
–
}
◊
®
Stomach
mixes food w/ various gastric juices to chemically
break it down into smaller pieces
◊
Mechanical digestion when muscles mix, churn,
and push contents w/ gastric juices
◊
When empty stomach holds 1 cup but can expand
up to holding 1 gallon
◊
Chyme: the semiliquid, partially digested food
mass that leaves the stomach and enters the small
intestine
Pyloric sphincter is the gateway for food for
this passage
}
◊
®
Small intestine
Where most of the action takes place
Mechanical and chemical digestion
Muscular digestion to push chyme
forward
–
Digestive secretions break down
nutrients
–
}
Surface is lined w/ villi to maximize
absorption
}
Contact time is 3 to 10 hours depending on
food eaten
}
◊
3 segments (don't really need to know)
Duodenum
}
Jejunum
}
Ileum
}
◊
®
Large intestine
Most absorption is already done at this point
Absorbs water and some nutrients though
(water, sodium, potassium, and chloride)
}
◊
Chyme enters the large intestine through the
ileocecal valve
◊
3 segments (whole thing is 5 feet long and 2.5
inches)
Cecum: beginning part
}
Colon: largest part
}
Rectum: final 8- inch part
}
◊
Intestinal matter spends 12 to 70 hours in large
intestine depending on the person's health, age,
diet, and fiber intake
◊
®
□
Sphincters allow food to pass from one organ to the next□
Accessory organs outside the GI tract aid in digestion (by
secreting digestive juices)
Salivary glands
Dissolve small food particles to ease the process of
swallowing food
◊
Contains water, mucus, electrolytes, and a few
enzymes
◊
®
Liver
Largest internal organ in the body (weighing 3
pounds)
◊
Major player in digestion, absorption, and
transport of nutrients
◊
Essential in carb metabolism
◊
Makes proteins
◊
Produces bile (salts) which digest fat
◊
Site of alcohols metabolism and removes and
degrades toxins and excess hormones
◊
®
Gallbladder
Receives bile from liver via common hepatic duct1.
Concentrates bile2.
Releases bile into small intestine via common bile
duct
3.
®
Pancreas
Endocrine function: releases hormones to
maintain blood glucose levels
◊
Exocrine function: secretes digestive enzymes into
the small intestine
◊
®
□
§
○
-
Food is propelled through GI tract by strong muscular contractions
2 primary contractions:
Peristalsis: squeezes food forward through the GI tract
Mechanical digestion□
§
Segmentation: shifts food back and forth along the GI tract in the
intestines
Allows contact w/ surface of small and large intestines and
increases absorption
□
§
○
-
How food is chemically digested
Enzymes are proteins that drive the process of digestion
Catalyze (speed up) hydrolysis which the chemical reaction that uses
water to split chemical bonds of digestible nutrients
§
3 conditions required for enzymes to work:
Compatible enzyme and nutrient 1.
The pH of surrounding environment must be in a correct range
If not, enzyme activity is decreased or halted b/c enzyme
(protein) will be denatured
a)
2.
Temp must be optimal
Same as 2aa)
3.
§
○
Secretions of the GI tract
HCl:
Secreted in stomach□
Denature/ activate proteins/ enzymes□
§
Mucus
Protection from acid (stomach and SI)□
§
Bicarbonate- will ask what it does
Secreted by pancreas□
Neutralize acidic chyme (raise pH) ** will ask if raise or lower
pH
□
§
Bile
Produced in liver□
Emulsifies (like kind of mixing oils) fat for digestion□
§
○
How nutrients are absorbed
In small intestine
Passive diffusion: nutrients move high to low concentration, no
energy required
□
Facilitated diffusion: nutrients move high to low concentration
w/ the help of a carrier protein; no energy required
□
Active transport: nutrients move low to high concentration w/
the help of a carrier protein; energy required
□
Endocytosis: cell forms a vesicle to surround and engulf a
nutrient
□
§
In large intestine
Majority of nutrients absorbed when chyme enters large
intestine
Water and salt absorbed in large intestine
®
Some mechanisms in small intestine also used in large
intestine
Water: passive diffusion
◊
Sodium: active transport
◊
®
□
§
○
-
How hormones and N.S. regulate digestion
By controlling:
Release of gastric and pancreatic secretions
§
Peristalsis
§
Enzyme activity
§
○
Enterogastrones are produced and secreted by the cells lining the stomach
and small intestine
Influence GI motility, stomach emptying, gallbladder contraction,
intestinal absorption, and hunger
§
Release of hormones is stimulated by types of foods passing through
digestive tract
§
○
Types of hormones
Gastrin: stimulates HCl production and release of gastric enzymes
§
Secretin: stimulates pancreas to release bicarbonate to small
intestine (increases pH)
§
Cholecystokinin (CCK): when fat, stimulates pancreas to release
lipase and gallbladder to release bile
§
Gastrin inhibitory peptide (GIP): inhibits gastric motility and stomach
secretions
§
○
N.S. communicates w/ GI tract
Tells you when to eat and drink, and when to stop
Extrinsic nerves:
Communicate changes in GI tract and stimulate mobility
®
Originate in brain or spinal cord
®
□
Intrinsic nerves:
Receive message from extrinsic nerves and respond by
stimulating release of digestive juices
®
Interwoven in linings of esophagus, stomach, and small
and large intestines
®
□
§
2 main hormones
Ghrelin: triggers hunger
When people go on diets, this increases
®
□
PYY: satiety/ fullness hormone□
§
○
-
How nutrients transported through body:
Water-soluble nutrients absorbed into cardiovascular system through
hepatic portal vein to liver
Carbs, amino acids, water-soluble vitamins
§
○
Fat-soluble nutrients absorbed into lymphatic system
Fat-soluble vitamins, long-chain fatty acids, and proteins that are too
big to be transported via capillaries
§
○
Waste products removed via excretory system
○
Kidneys filter blood, allowing waste products to be concentrated in urine
and excreted
○
-
Common digestive disorders
Esophageal problems
Gastroesophageal reflux disease (GERD) aka indigestion or acid reflux
LES (lower esophageal sphincter) doesn't close properly, or
relaxes, and allows HCl from stomach into esophagus
□
Behavior modifications
Change what eat (sometimes take tums), or even
eliminate certain foods
□
Smoking and drinking relaxes LES (lower esophageal
sphincter)
□
Also wearing tight clothes, like skinny jeans□
Don't lay down after eat, or if you do prop yourself up□
□
§
Esophageal cancer
One of the most common cancers of digestive tract□
More common in males over 50, living in urban areas, who
smoke and drink heavily
□
Treatment: typical cancer treatment□
§
○
Disorders of stomach
Belching (burping)
Swallowing amounts of air
Eating too fast, drinking soda, anxiety, chewing gum,
smoking
□
□
§
Stomach flu
Symptoms: nausea, vomiting, diarrhea, and abdominal
cramping
□
Treatment: rest, rehydration, and eating soft foods□
§
Foodborne illness
Consuming food or drink w/ a pathogenic microbe such as E.
Coli, Salmonella, or Campylobacter
□
Most are self-limiting and need rest and rehydration□
§
Ulcers
Sore or erosion in lining of lower region of stomach or upper
part of duodenum
□
Helicobacter pylori, bacterium, often involved□
Symptoms: fatigue, bleeding, general weakness, burning pain□
Treatment: rx drugs, dietary changes, and/ or surgery□
If untreated: peritonitis, scar tissue can obstruct food and
cause vomiting and weight loss, and greater risk for cancer
□
§
Gallbladder disease
Most often in woman and older Americans□
Can create gallstones□
§
Celiac disease
Autoimmune disorder to small intestine when consume gluten
Causes villi to flatten out, causing nutrient malabsorption□
□
Can lead to increased risk for osteoporosis, diminished growth,
seizures
□
Diagnosis via blood test and tissue biopsy of small intestine□
Only treatment is cutting out all gluten□
§
○
Other kinds of intestinal disorders
Flatulence: release of gas
Via
Foods high in fiber and starch□
Eating quickly□
Drinking carbonated beverages□
Lack of exercise□
Smoking□
□
§
Diarrhea
Treatment: fluid and electrolyte replacement□
§
Constipation
Treatment: exercise, normal eating patterns, and rest□
Laxatives used sparingly□
§
Hemorrhoids: swelling of veins of rectum and anus
Cause is unknown□
Treatment includes fiber and fluid intake□
§
Irritable bowel syndrome (IBS)
Having GI issues but not really sure what so lumped together□
§
Ulcerative colitis
Chronic inflammation of large intestine, resulting in ulcers in
lining of colon
□
Hereditary□
In men and women, beginning ages 15-30□
No cause or cure□
Treatment: drug therapy and surgery□
§
Crohn's disease: similar to ulcerative colitis, but ulcers can occur
throughout GI tract
No cause or cure□
Treatment: drug therapy or possibly surgery□
§
Colon cancer: third leading cause of cancer death, but most curable if
caught early
Begins w/ polyps (clump of cells in colon that mostly are small
and benign but can turn into cancer), that can be surgically
removed
□
Treatment: typical cancer treatment□
Survival depends on age, treatment response, and stage of
cancer diagnosis
□
§
○
-
NUTR 2105 Chpt. 3
Monday, January 22, 2018 2:13 PM
Process and organs involved in digestion?
Digestion: process of breaking down food into individual molecules small
enough to be absorbed through intestinal wall
○
Absorption: process of moving nutrients from GI tract into circulatory
system
○
Transport: process of moving absorbed nutrients throughout body through
the circulatory and lymph systems
○
Elimination: excretion of undigested and unabsorbed food through feces
Organs of GI tract:
Made of 5 organs:
Mouth
Mechanical digestion: chewing, grinding,
squeezing, and moving food through GI tract
through peristalsis and segmentation
◊
Chemical digestion: breaking down food through
enzymatic reactions
Saliva
Dissolves small food particles
–
Contains the enzyme amylase which
breaks down carbs
Prevents cavities
w
–
}
Once food is chewed and moistened, tongue
rolls it into a bolus and it enters pharynx to
be swallowed (enters esophagus)
}
◊
®
Esophagus
Transports food and fluids to stomach
◊
2 sphincters in esophagus:
Upper esophageal sphincter: allows the
bolus of food to enter esophagus
}
Lower esophageal sphincter (LES): allows the
bolus of food to enter stomach
When relaxes: acid reflux (heart burn)
–
}
◊
®
Stomach
mixes food w/ various gastric juices to chemically
break it down into smaller pieces
◊
Mechanical digestion when muscles mix, churn,
and push contents w/ gastric juices
◊
When empty stomach holds 1 cup but can expand
up to holding 1 gallon
◊
Chyme: the semiliquid, partially digested food
mass that leaves the stomach and enters the small
intestine
Pyloric sphincter is the gateway for food for
this passage
}
◊
®
Small intestine
Where most of the action takes place
Mechanical and chemical digestion
Muscular digestion to push chyme
forward
–
Digestive secretions break down
nutrients
–
}
Surface is lined w/ villi to maximize
absorption
}
Contact time is 3 to 10 hours depending on
food eaten
}
◊
3 segments (don't really need to know)
Duodenum
}
Jejunum
}
Ileum
}
◊
®
Large intestine
Most absorption is already done at this point
Absorbs water and some nutrients though
(water, sodium, potassium, and chloride)
}
◊
Chyme enters the large intestine through the
ileocecal valve
◊
3 segments (whole thing is 5 feet long and 2.5
inches)
Cecum: beginning part
}
Colon: largest part
}
Rectum: final 8- inch part
}
◊
Intestinal matter spends 12 to 70 hours in large
intestine depending on the person's health, age,
diet, and fiber intake
◊
®
□
Sphincters allow food to pass from one organ to the next
□
Accessory organs outside the GI tract aid in digestion (by
secreting digestive juices)
Salivary glands
Dissolve small food particles to ease the process of
swallowing food
◊
Contains water, mucus, electrolytes, and a few
enzymes
◊
®
Liver
Largest internal organ in the body (weighing 3
pounds)
◊
Major player in digestion, absorption, and
transport of nutrients
◊
Essential in carb metabolism
◊
Makes proteins
◊
Produces bile (salts) which digest fat
◊
Site of alcohols metabolism and removes and
degrades toxins and excess hormones
◊
®
Gallbladder
Receives bile from liver via common hepatic duct
1.
Concentrates bile
2.
Releases bile into small intestine via common bile
duct
3.
®
Pancreas
Endocrine function: releases hormones to
maintain blood glucose levels
◊
Exocrine function: secretes digestive enzymes into
the small intestine
◊
®
□
§
○
-
Food is propelled through GI tract by strong muscular contractions
2 primary contractions:
Peristalsis: squeezes food forward through the GI tract
Mechanical digestion
□
§
Segmentation: shifts food back and forth along the GI tract in the
intestines
Allows contact w/ surface of small and large intestines and
increases absorption
□
§
○
-
How food is chemically digested
Enzymes are proteins that drive the process of digestion
Catalyze (speed up) hydrolysis which the chemical reaction that uses
water to split chemical bonds of digestible nutrients
§
3 conditions required for enzymes to work:
Compatible enzyme and nutrient 1.
The pH of surrounding environment must be in a correct range
If not, enzyme activity is decreased or halted b/c enzyme
(protein) will be denatured
a)
2.
Temp must be optimal
Same as 2aa)
3.
§
○
Secretions of the GI tract
HCl:
Secreted in stomach□
Denature/ activate proteins/ enzymes□
§
Mucus
Protection from acid (stomach and SI)□
§
Bicarbonate- will ask what it does
Secreted by pancreas□
Neutralize acidic chyme (raise pH) ** will ask if raise or lower
pH
□
§
Bile
Produced in liver□
Emulsifies (like kind of mixing oils) fat for digestion□
§
○
How nutrients are absorbed
In small intestine
Passive diffusion: nutrients move high to low concentration, no
energy required
□
Facilitated diffusion: nutrients move high to low concentration
w/ the help of a carrier protein; no energy required
□
Active transport: nutrients move low to high concentration w/
the help of a carrier protein; energy required
□
Endocytosis: cell forms a vesicle to surround and engulf a
nutrient
□
§
In large intestine
Majority of nutrients absorbed when chyme enters large
intestine
Water and salt absorbed in large intestine
®
Some mechanisms in small intestine also used in large
intestine
Water: passive diffusion
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Sodium: active transport
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How hormones and N.S. regulate digestion
By controlling:
Release of gastric and pancreatic secretions
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Peristalsis
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Enzyme activity
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Enterogastrones are produced and secreted by the cells lining the stomach
and small intestine
Influence GI motility, stomach emptying, gallbladder contraction,
intestinal absorption, and hunger
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Release of hormones is stimulated by types of foods passing through
digestive tract
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Types of hormones
Gastrin: stimulates HCl production and release of gastric enzymes
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Secretin: stimulates pancreas to release bicarbonate to small
intestine (increases pH)
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Cholecystokinin (CCK): when fat, stimulates pancreas to release
lipase and gallbladder to release bile
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Gastrin inhibitory peptide (GIP): inhibits gastric motility and stomach
secretions
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N.S. communicates w/ GI tract
Tells you when to eat and drink, and when to stop
Extrinsic nerves:
Communicate changes in GI tract and stimulate mobility
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Originate in brain or spinal cord
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Intrinsic nerves:
Receive message from extrinsic nerves and respond by
stimulating release of digestive juices
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Interwoven in linings of esophagus, stomach, and small
and large intestines
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2 main hormones
Ghrelin: triggers hunger
When people go on diets, this increases
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PYY: satiety/ fullness hormone□
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How nutrients transported through body:
Water-soluble nutrients absorbed into cardiovascular system through
hepatic portal vein to liver
Carbs, amino acids, water-soluble vitamins
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Fat-soluble nutrients absorbed into lymphatic system
Fat-soluble vitamins, long-chain fatty acids, and proteins that are too
big to be transported via capillaries
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Waste products removed via excretory system
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Kidneys filter blood, allowing waste products to be concentrated in urine
and excreted
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Common digestive disorders
Esophageal problems
Gastroesophageal reflux disease (GERD) aka indigestion or acid reflux
LES (lower esophageal sphincter) doesn't close properly, or
relaxes, and allows HCl from stomach into esophagus
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Behavior modifications
Change what eat (sometimes take tums), or even
eliminate certain foods
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Smoking and drinking relaxes LES (lower esophageal
sphincter)
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Also wearing tight clothes, like skinny jeans□
Don't lay down after eat, or if you do prop yourself up□
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Esophageal cancer
One of the most common cancers of digestive tract□
More common in males over 50, living in urban areas, who
smoke and drink heavily
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Treatment: typical cancer treatment□
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Disorders of stomach
Belching (burping)
Swallowing amounts of air
Eating too fast, drinking soda, anxiety, chewing gum,
smoking
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Stomach flu
Symptoms: nausea, vomiting, diarrhea, and abdominal
cramping
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Treatment: rest, rehydration, and eating soft foods□
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Foodborne illness
Consuming food or drink w/ a pathogenic microbe such as E.
Coli, Salmonella, or Campylobacter
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Most are self-limiting and need rest and rehydration□
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Ulcers
Sore or erosion in lining of lower region of stomach or upper
part of duodenum
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Helicobacter pylori, bacterium, often involved□
Symptoms: fatigue, bleeding, general weakness, burning pain□
Treatment: rx drugs, dietary changes, and/ or surgery□
If untreated: peritonitis, scar tissue can obstruct food and
cause vomiting and weight loss, and greater risk for cancer
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Gallbladder disease
Most often in woman and older Americans□
Can create gallstones□
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Celiac disease
Autoimmune disorder to small intestine when consume gluten
Causes villi to flatten out, causing nutrient malabsorption□
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Can lead to increased risk for osteoporosis, diminished growth,
seizures
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Diagnosis via blood test and tissue biopsy of small intestine□
Only treatment is cutting out all gluten□
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Other kinds of intestinal disorders
Flatulence: release of gas
Via
Foods high in fiber and starch□
Eating quickly□
Drinking carbonated beverages□
Lack of exercise□
Smoking□
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Diarrhea
Treatment: fluid and electrolyte replacement□
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Constipation
Treatment: exercise, normal eating patterns, and rest□
Laxatives used sparingly□
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Hemorrhoids: swelling of veins of rectum and anus
Cause is unknown□
Treatment includes fiber and fluid intake□
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Irritable bowel syndrome (IBS)
Having GI issues but not really sure what so lumped together□
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Ulcerative colitis
Chronic inflammation of large intestine, resulting in ulcers in
lining of colon
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Hereditary□
In men and women, beginning ages 15-30□
No cause or cure□
Treatment: drug therapy and surgery□
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Crohn's disease: similar to ulcerative colitis, but ulcers can occur
throughout GI tract
No cause or cure□
Treatment: drug therapy or possibly surgery□
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Colon cancer: third leading cause of cancer death, but most curable if
caught early
Begins w/ polyps (clump of cells in colon that mostly are small
and benign but can turn into cancer), that can be surgically
removed
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Treatment: typical cancer treatment□
Survival depends on age, treatment response, and stage of
cancer diagnosis
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NUTR 2105 Chpt. 3
Monday, January 22, 2018 2:13 PM
Document Summary
Digestion: process of breaking down food into individual molecules small enough to be absorbed through intestinal wall. Absorption: process of moving nutrients from gi tract into circulatory system. Transport: process of moving absorbed nutrients throughout body through the circulatory and lymph systems. Elimination: excretion of undigested and unabsorbed food through feces. Mechanical digestion: chewing, grinding, squeezing, and moving food through gi tract through peristalsis and segmentation. Chemical digestion: breaking down food through enzymatic reactions. Contains the enzyme amylase which breaks down carbs w. Once food is chewed and moistened, tongue rolls it into a bolus and it enters pharynx to be swallowed (enters esophagus) Upper esophageal sphincter: allows the bolus of food to enter esophagus. Lower esophageal sphincter (les): allows the bolus of food to enter stomach. Stomach mixes food w/ various gastric juices to chemically mixes food w/ various gastric juices to chemically break it down into smaller pieces.
