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Human Nutrition > Lecture 3: Digestion, Absorption, and Transport > Flashcards

Lecture 3: Digestion, Absorption, and Transport Flashcards

1
Q

Digestion

A

The process of breaking down food
into individual molecules small enough to be
absorbed through the intestinal wall

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2
Q

Absorption

A

The process of moving nutrients
from the gastrointestinal (GI) tract into the
circulatory system

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3
Q

Transport

A

The process of moving absorbed
nutrients throughout the body through the
circulatory and lymph systems

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4
Q

Elimination

A

The excretion of undigested and
unabsorbed food through the feces

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4
Q

Main Organs

A

Mouth
Esophagus
Stomach
Small intestine
Large intestine

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5
Q

Accessory Organs

A

Salivary glands
Liver
Pancreas
Gallbladder

They are outside the GI tract but aid in digestion

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6
Q

Sphincters

A

allows food to pass from one organ to the next

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7
Q

Where does digestion begin?

A

Mouth

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8
Q

Mechanical Digestion

A

Breaking down food through
chewing, grinding, squeezing, and moving food
through the GI tract by peristalsis and segmentation

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9
Q

Chemical Digestion

A

Breaking down food through
enzymatic reactions

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10
Q

Saliva

A
  • Dissolves small food particles
  • Contains the enzyme amylase, which begins to break
    down carbohydrates à chemical digestion
  • In adults, no other chemical digestion takes place in
    the mouth
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11
Q

Bolus

A

Once food has been
adequately chewed and
moistened, the tongue rolls
it into a bolus and it enters
the pharynx to be swallowed

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12
Q

Epiglottis

A

Closes off the trachea and prevent choking

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13
Q

Esophagus

A

transports food and fluids to the
stomach

Bolus enters esophagus

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14
Q

Upper esophageal sphincter

A

Allows the bolus of food to enter the esophagus

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15
Q

Lower esophageal sphincter (LES)

A

Allows the bolus of food to enter the stomach

The LES relaxes after swallowing to allow the bolus to enter the stomach

The LES contracts to prevent stomach contents from returning to the esophagus

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16
Q

Stomach

A

Stores, mizes and prepares food for digestion

  • Chemical digestion à mixes food with gastric juices
    to break it down into smaller pieces
  • Mechanical digestion à muscles of the stomach mix,
    churn, and push the contents with the gastric juices
  • Empty: holds 1 cup
  • Fully expanded: up to 1 gallon
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17
Q

Chyme

A
  • the semiliquid, partially digested food mass
    that leaves the stomach and enters the small intestine
  • Approximately 1 tsp of chyme leaves the stomach
    and enters the small intestine every 30 seconds
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18
Q

Pyloric Sphincter

A

the gateway for chyme to enter the small intestine from the stomach

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19
Q

Three segments of small intestine

A

Duodenum: 10 inches long
Jejunum: 8 feet long
Ileum: 12 feet long

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20
Q

Digestion in small intestine

A
  • Mechanical digestion à muscular contractions push
    chyme forward
  • Chemical digestion à digestive secretions break down
    nutrients
  • The contact time in the small intestine is 3 to 10 hours,
    depending on the food eaten
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21
Q

Structure of the small intestinal wall

A

surface contains circular folds, villi, and microvilli

All help increase surface area to help maximize absorption

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22
Q

Three segments of Large Intestine

A

Cecum: beginning of large intestine
Colon: largest part of the large intestine
Rectum: Final 8-inch portion of the large intestine

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23
Q

Large Intestine

A

Absorbs water and some nutrients

Chyme enters large intestine through the ileocecal valve

is 5 feet long and 2.5 inches in diameter

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24
Q

Purpose of Large Intestine

A
  • Site of water, sodium, potassium, and chloride
    absorption
  • Bacteria produce vitamin K, thiamin, riboflavin, biotin,
    and vitamin B12
  • Only biotin and vitamin K can be absorbed
  • Bacteria in the colon ferment some undigested and
    unabsorbed carbohydrates into simpler compounds,
    methane gas, carbon dioxide, and hydrogen.
  • Fermented fiber produces short-chain fatty acids
  • 1 liter of fluid material is gradually reduced to 200
    grams of brown fecal material
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25
Q

Purpose of the end of the Large Intestine

A
  • The intestinal matter passes through the large
    intestine in 12 to 70 hours, depending on the
    person’s health, age, diet, and fiber intake
  • Stool is propelled through the large intestine until it
    reaches the rectum, the 8-inch portion of the large
    intestine
  • Anus is the opening of the rectum, or end of the GI tract
  • The final stage of defecation is under voluntary control
    ~Influenced by age, diet, prescription medications,
    health, and abdominal muscle tone
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26
Q

Salivary Glands

A
  • Dissolve small food particles to ease the
    process of swallowing food
  • The body produces 1 quart of saliva per day
  • Saliva contains water, mucus, electrolytes,
    and a few enzymes
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27
Q

Liver

A
  • Largest internal organ in the body à 3
    pounds
  • Major player in the digestion, absorption,
    and transport of nutrients
  • Essential in carbohydrate metabolism
  • Makes proteins
  • Manufactures bile salts used to digest fats
  • Site of alcohol metabolism
  • Removes and degrades toxins and excess
    hormones
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28
Q

Gallbladder

A
  • Receives bile from the liver via the common
    hepatic duct
  • Concentrates bile
  • Releases bile into the small intestine via the
    common bile duct
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29
Q

Pancreas

A
  • Endocrine function: Releases hormones to
    maintain blood glucose levels
  • Exocrine function: Secretes digestive
    enzymes into the small intestine
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30
Q

How is food propelled through GI tract

A

Peristalsis
Segmentation

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31
Q

Peristalsis

A

Squeezes food forward through the GI tract
* Mechanical digestion

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32
Q

Segmentation

A

Shifts food back and forth along the GI tract in the intestines
* Allows contact with surface of small and large intestines and increases absorption

33
Q

How is food chemically digested?

A
  • Digestive enzymes and other substances
  • Regulated by hormones
  • Completed by the time the food reaches the
    large intestine
34
Q

What aids food in chemical digestion?

A

Enzymes

35
Q

Enzymes

A

Proteins that drive the process of digestion by catalyzing (speeding up) hydrolysis

36
Q

Hydrolysis

A
  • Chemical reaction that uses water to split chemical
    bonds of digestible nutrients
  • The hydroxyl group (OH) from water joins one
    molecule while the hydrogen ion (H) joins the other
    molecule
37
Q

The three conditions required for enzymes to work

A
  1. Presence of compatible enzyme and nutrient
  2. pH of surrounding environment must fall within a certain range
  3. Must have optimal environment temperature
37
Q

The three conditions required for enzymes to work

A
  1. Presence of compatible enzyme and nutrient
    ~Enzymes are compatible only with a specific
    compound or nutrient (substrate)
  2. pH of surrounding environment must fall within a certain range
    ~Most active and efficient within a certain range of
    acidity and alkalinity
  3. Must have optimal environment temperature
    ~Enzyme activity is slowed with too low a temperature and stopped when the temperature is too high.
38
Q

Where does majority of nutrient absorption take place?

A

Small intestine

39
Q

Methods of Absorption

A

Passive Diffusion
Facilitated diffusion
Active Transport
Endocytosis

40
Q

Passive Diffusion

A

Nutrients move from high concentration to low concentration
– no energy required
– e.g. water, small lipids

41
Q

Facilitated Diffusion

A

Nutrients move from high concentration to low concentration with the help of a carrier protein
– no energy required
– E.g. fructose

42
Q

Active Transport

A

Nutrients move from low concentration to high concentration with the help of a carrier protein
– energy required
– E.g. glucose, amino acids

43
Q

Endocytosis

A

Cell forms a vesicle to surround and engulf a nutrient
– E.g. whole proteins such as immunoglobulins in breast milk

44
Q

Where does most of fluid absorption occur?

A

Large Intestine

45
Q

Fluid Absorption

A
  • The majority of nutrients have been absorbed when chyme enters the large intestine
  • Water and sodium are absorbed in the large intestine
  • The same mechanisms used in the small intestine are also used in the large intestine
    ~Water: Passive diffusion
    ~Sodium: Active transport
46
Q

What can influence digestion and absorption?

A

Psychological influences
Chemical influences
Bacterial influences

47
Q

Psychological influences

A

Taste, smell, presentation of food, expectations that food tastes good, environment

48
Q

Chemical influences

A

Preparation of food, digestibility, temperature

49
Q

Bacterial influences

A

Amount of stomach acid, microbes in large intestine

50
Q

What can increase satiety?

A

Fat
Protein
Fiber and whole grains
Water

51
Q

Regulation of Digestion

A

Endocrine system and Nervous system work together to coordinate digestion, absorption, and excretion of waste
products

52
Q

What is digestion controlled by?

A

Enteric nervous system

53
Q

Enteric Nervous System

A
  • a meshwork of nerve fibers that innervate the GI
    tract, pancreas, and gallbladder
    ~Monitor stomach contractions after eating
    ~Monitor secretions of the cells in the GI tract
54
Q

How does the nervous systems communicate with GI tract?

A

Extrinsic nerves
Intrinsic nerves

55
Q

Extrinsic Nerves

A
  • Communicate changes in the GI tract and
    stimulate motility
  • Originate in the brain or spinal cord
56
Q

Intrinsic Nerves

A
  • Receive the message from the extrinsic
    nerves and respond by stimulating the
    release of digestive juices
  • Interwoven in the linings of the esophagus,
    stomach, and small and large intestines
57
Q

Hormones

A

Regulates digestion by controlling:
* The release of gastric and pancreatic secretions
* Peristalsis
* Enzyme activity

58
Q

Enterogastrones

A

produced and secreted by cells lining the stomach and small intestine
~Influence GI motility, stomach emptying, gallbladder
contraction, intestinal absorption, and hunger
~Release is stimulated by the types of food passing
through the digestive tract

59
Q

Key Hormones

A

Gastrin
Secretin
Cholecystokinin
Gastric inhibitory peptide (GIP)
Ghrelin
PYY

60
Q

Gastrin

A

Stimulates HCl production and the release
of gastric enzymes
* Lowers pH

61
Q

Secretin

A

Stimulates the pancreas to release
bicarbonate in the small intestine
* Raises pH

62
Q

Cholecystokinin (CCK)

A

Stimulates the pancreas to release lipase and the gallbladder to release bile
* Slows gastric motility

63
Q

Gastric inhibitory peptide (GIP)

A

Inhibits gastric motility and stomach secretions

64
Q

Ghrelin

A

Increases hunger

65
Q

PYY

A

Decreases hunger

66
Q

How are nutrients transported throughout the body?

A
  • Nutrients are absorbed into the bloodstream or lymphatic
    system.
  • The waste products that remain after nutrient
    absorption are removed by the excretory
    system
  • The kidneys filter the blood, allowing waste
    products to be concentrated in the urine and
    excreted
67
Q

Water soluble nutrients

A

~Absorbed into the cardiovascular system through the hepatic portal vein to the liver
-Carbohydrates, amino acids, and water-soluble vitamins

68
Q

Fat-soluble Nutrients

A

Absorbed into the lymphatic system
~Fat-soluble vitamins, long-chain fatty acids, and
proteins
-Too large to be transported via the capillaries

69
Q

Common Digestive Disorders

A

Range from minor to serious in nature

  • Heartburn
  • Esophageal cancer
  • Belching
  • Gastroenteritis
  • Ulcers
  • Gallbladder disease
  • Flatulence
  • Diarrhea/constipation
  • Hemorrhoids
  • Irritable bowel syndrome
  • Ulcerative colitis
  • Crohn’s disease
  • Colon cancer
  • Celiac disease
70
Q

Gastroesophageal Reflux Disease (GERD)

A

Esophageal problem

Most commonly known as indigestion or acid reflux

  • The lower esophageal sphincter doesn’t close
    properly, allowing HCl from the stomach to flow into
    the esophagus.
  • Leads to chronic heartburn and stomach acid reflux
  • Factors generally associated with GERD include:
    ~Chocolate, fatty foods, coffee, soda, onions, garlic
    ~Smoking, being overweight or obese, drinking alcohol,
    wearing tight-fitting clothing, eating large evening meals,
    reclining after eating
  • Dietary changes, behavior modification, antacids,
    prescription drugs, or surgery may help
71
Q

Ulcers

A

Disorder of the Stomach

  • A sore or erosion in the lining of the lower region of
    the stomach or upper part of the duodenum
  • Helicobacter pylori, a bacterium, is often involved in
    the creation of ulcers
  • Common symptoms are vomiting, fatigue, bleeding,
    general weakness, and burning pain
  • Treatment can include prescription drugs, dietary
    changes, and/or surgery
  • An untreated ulcer can result in peritonitis (a scar
    tissue that can obstruct food and cause vomiting and
    weight loss, and greater risk for stomach cancer)
72
Q

Gallstones

A

Gallbladder Disease

  • Diagnosed most frequently in women and older Americans
  • Obesity and rapid weight loss are contributing factors
  • An unhealthy gallbladder can create gallstones
    ~Stones are formed from cholesterol in the gallbladder
    or bile duct
    ~Treatment includes surgery for gallbladder removal,
    prescription medication, shock-wave therapy, or a
    combination of therapies
    ~The body eventually adapts to the removal of the
    gallbladder by secreting bile directly into the duodenum
73
Q

Celiac Disease

A

Intestinal Disorder

  • A genetic autoimmune disorder that causes damage to the small intestine when foods containing gluten are consumed
  • Causes the small intestinal villi to flatten out, causing nutrient malabsorption
  • Caused by an abnormal reaction to the protein
    gluten, found in rye, wheat, and barley
  • Symptoms
    ~Reoccurring abdominal bloating
    ~Cramping and/or gas
    ~Diarrhea
    ~Foul-smelling stools
    ~Weight loss
    ~Anemia
    ~Bone or joint pain
  • Increases risk for osteoporosis, diminished
    growth, seizures
  • Diagnosis is made with a blood test and tissue
    biopsy of the small intestine
  • Treatment
  • Strict gluten-free diet
74
Q

Irritable bowel syndrome (IBS)

A

Intestinal Disorders

Changes in colon rhythm
* Those with IBS experience an over-response to colon stimuli,
resulting in alternating patterns of diarrhea, constipation, and
abdominal pain
* Exact cause unknown
* Treatment may include increased dietary fiber, stress management, medications, FODMAP diet, probiotics

75
Q

Diarrhea

A

Intestinal Disorder

The passage of watery, loose stools more than three times a day
~Generally the result of bacterial, viral, or parasitic infections that cause food and fluids to pass too quickly through the colon
-Chronic diarrhea may be the sign of a more serious problem
-Untreated diarrhea can lead to malnutrition

  • Diarrhea can lead to dehydration and
    potentially death, particularly in children and
    the elderly
  • Treated with fluid and electrolyte replacement
76
Q

Constipatio

A

Intestinal Disorders

Infrequent passage of dry, hardened stools

Often due to insufficient fiber or water intake
* Other causes include stress, inactivity, smoking
cessation and various illnesses
* Treatment
~Exercise, normal eating patterns, and proper rest
~Laxatives should be used sparingly, as they can
cause dehydration, salt imbalances, and laxative
dependency
~Avoid enemas

77
Q

Diverticulosis

A

Intestinal Disorders

  • Small pouches develop along the large intestine
  • May become infected (diverticulitis)
  • Often caused by chronic constipation
  • May be a chronic condition
  • Worsened by low-fiber diets
78
Q

Hemorrhoids

A

Intestinal Disorders

Swelling of the veins of the rectum and anus

  • Can lead to bleeding, itching, and/or pain
  • Cause unknown
    ~Straining to pass dry stools, pregnancy, constant
    constipation or diarrhea, and aging contribute
  • Treatment: increased dietary fiber and fluid
    intake
    ~Itching and pain can be relieved through use of
    creams, ice packs, and soaking in a warm bath
    ~Severe cases may require surgery
79
Q

Ulcerative Colitis and Crohn’s Disease

A

Type of Inflammatory Bowel Disease (IBD):

  • Chronic inflammation of the GI tract, resulting in ulcers
  • Tends to run in families
  • No known cause or cure
  • Treatment includes drug therapy and surgery
80
Q

Colon Cancer

A

Intestinal Disorders

The third leading cause of cancer death, but one of the most curable cancers if detected early

  • Begins with polyps on the lining of the colon that
    are often small, benign, and can be surgically
    removed
    ~Polyps can develop into cancerous tumors if not
    detected early
  • Treatment includes radiation, chemotherapy, or
    surgery
  • Survival rates vary depending on age, treatment
    response, and stage of cancer diagnosis

Human Nutrition (6 decks)

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