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Nutrition 1 (Semester I) > 5a. Digestion & Health - Digestive System > Flashcards

5a. Digestion & Health - Digestive System Flashcards

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1
Q

What are the three primary functions of the digestive system?

A

Digestion
Absorption
Excretion

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2
Q

What constitutes digestion?

A

Mechanical - chewing, peristalsis

Chemical - gastric juices, pancreatic enzymes, bile & enterocyte enzymes

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3
Q

Where does most absorption occur?

A

Small intestine

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4
Q

Where are most substances absorbed into?

A

Blood

Lymph

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5
Q

How are waste materials excreted?

A

As faeces
Via urine
Skin
Lungs

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6
Q

Which elements make up the digestive tract?

A 
Mouth
Pharynx
Oesophagus
Stomach
Small/large intestine
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7
Q

Which elements make up accessory organs?

A 
Salivary glands
Pancreas
Liver
Gall bladder
Biliary tract
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8
Q

Which is the first location in the GI tract where digestion occurs?

A

Mouth/oral cavity

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9
Q

What is the process of digestion in the mouth?

A

Chewing breaks down food into smaller chunks

Triggers the salivary glands to release saliva

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10
Q

Why is saliva important in digestion?

A

Contains enzyme amylase that breaks down polysaccharides (starches found in foods)

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11
Q

How often should food be chewed?

A

Up to 20 times per bite

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12
Q

What happens the more you chew?

A

More amylase is released

The more carbs can be broken down and made available to the body

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13
Q

Why should you avoid drinking with meals?

A

Drinking dilutes saliva and gastric juices

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14
Q

What does diluted digestive juices result in?

A

Fewer nutrients being made available to the body

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15
Q

What is the optimal pH for salivary amylase to function?

A

6.8

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16
Q

What happens to amylase once it reaches the stomach?

A

Denatured by stomach acid

Becomes inactive once the bolus arrives in the stomach

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17
Q

What happens to carbs not broken down in the mouth?

A

They remain unutilised as the small intestine can only absorb single sugars

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18
Q

What can challenge the optimal saliva pH?

A

Excess acidity in body tissues which are excreted via saliva

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19
Q

What does the lowering of salivary pH do?

A

Impairs the functionality of salivary amylase

Impacts the digestion of carbs in the oral cavity

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20
Q

What factors can lower pH in the mouth?

A 
Refined sugars
Meat
Dairy
Processed foods
Alcohol
Coffee
Chewing gum
Cigarettes
Chronic stress
Sedentary lifestyle
Heavy metal exposure e.g. fillings
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21
Q

How does digested food enter the stomach?

A

Through the lower oesophageal sphincter (cardiac sphincter)

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22
Q

What happens when food enters the stomach?

A

Food stretches the stomach
Stimulates the enteric nerves in stomach wall
And release of hormone gastrin
Both stimulate peristalsis leading to release and formation of gastric juices containing HCI and digestive enzymes
Stomach churns the bolus, mixing it with gastric juices to break down food

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23
Q

Which digestive enzymes are released from the stomach wall?

A

Pepsinogen

Gastric lipase

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24
Q

What is pepsinogen?

A

Inactive enzyme which becomes active when exposed to HCl

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25
What does pepsinogen convert to?
Pepsin (the active form)
26
What does pepsin do?
Breaks down proteins into smaller protein chains
27
What does gastric lipase do?
Breaks down lipids
28
What substances can the stomach absorb?
Water Alcohol Iodine Fluoride
29
What happens to the substances which are absorbed by the stomach?
They enter the venous circulation and escorted to the liver by the portal vein to be processed
30
What is the pH of HCl?
2-3
31
Which nutrients are needed to make HCl?
Zinc | B6
32
What are food sources of zinc?
``` Nuts Seeds (esp pumpkin) Eggs Fish Meat Oysters ```
33
What are food sources of B6?
``` Whole grains Sunflower seeds Legumes Walnuts Green vegetables Carrots Potatoes Avocado Fish ```
34
What function does stomach acid have?
Breaks down proteins (pepsin) Breaks down fats (lipase) Triggers release of pancreatic juice and bile into the duodenum Eliminates micro-organisms - bacteria. viruses, fungi
35
What can low HCl production in the stomach be caused by?
``` Chronic stress Low B6 and zinc Medications e.g. PPIs Chronic H. pylori Ageing AI gastritis ```
36
What can low HCl lead to?
Poor protein digestion
37
What can poor protein digestion result in?
Protein putrefaction in SI
38
What does protein putrefaction create?
Compounds called polyamines
39
Which pathology are polyamines implicated in?
Colorectal cancer
40
What does undigested food in the SI do to bacteria?
Allows it to proliferate
41
Which pathology is caused by a proliferation of bacteria in the SI?
SIBO
42
What can low HCl do to the production of intrinsic factor?
Reduces production
43
What can low intrinsic factor compromise?
B12 absorption
44
How can low stomach acid present within 1-2 hrs after meals?
Bloating Belching Flatulence
45
How can low stomach acid present after eating?
Abdominal pain Fullness Foul smelling stools
46
How can you increase stomach acid?
``` Apple cider vinegar in a little water before meals Zinc and B6-rich foods Avoid overeating Bitter foods and herbs Eat fermented vegetables ```
47
Examples of bitter foods
Rocket Artichoke Watercress Chicory
48
Examples of bitter herbs
Gentian Barberry bark Dandelion Goldenseal
49
What is released as chyme is drip fed through the pyloric sphincter into the duodenum?
CCK | cholecystokinin
50
What is CCK?
Hormone released from the duodenal wall
51
What are the functions of CCK?
Triggers release of pancreatic juice Triggers release of bile Induces sense of satiety
52
What triggers the release of CCK?
Presence of proteins and/or fats in the chyme
53
What is the pH of chyme?
2
54
What neutralises chyme in the duodenum?
Bicarbonate
55
Where is the bicarbonate to neutralise the chyme released from?
Liver | Pancreas
56
What is the pH of the duodenum?
6.5
57
What is the main function of the SI?
Digestion | Absorption
58
What percentage of nutrients are absorbed in the SI?
90%
59
What are the three regions of the SI?
Duodenum Jejunum Ileum
60
What mainly happens in the duodenum?
Digestion
61
What mainly happens in the jejunum?
Absorption
62
What mainly happens in the illeum?
Absorption of B12
63
What feature does the SI have to aid absorption?
Villi
64
What do villi contain?
Blood capillaries | Lymphatic capillaries
65
What is the brush border also known as?
Microvilli
66
How are the nutrients absorbed in the SI?
Through the microvilli
67
What are attached to the microvilli to aid absorption?
Brush border enzymes
68
What are the names of the brush border enzymes?
Sucrase Maltase Lactase Dipeptidase
69
What are the functions of maltase, sucrase and lactase?
Break down double-chained sugars into single sugars | e.g. glucose, fructose, galactose
70
What is the function of dipeptidase?
Breaks down proteins into amino acids
71
In what form do carbs, proteins and fats need to be in to be able to be digested?
In their simplest forms | e.g. single chains
72
What determines if macronutrients are able to be broken down into their simplest forms?
Optimal function of the mouth, stomach, pancreas and gallbladder
73
Once absorbed by the microvilli, where do carbs and proteins go?
Through blood capillaries to the liver
74
Once absorbed by the microvilli, where do lipids go?
Through lymphatic capillaries
75
What is the exocrine function of the pancreas?
To produce enzymes that digest carbs, proteins and fats
76
Where are the pancreatic enzymes secreted into?
SI as part of pancreatic juice
77
Which pancreatic enzyme digests carbs?
Pancreatic amylase
78
Which pancreatic enzyme digests fats?
Pancreatic lipase
79
Which pancreatic enzymes digest proteins?
Proteases - trypsin, chymotrypsin
80
How is the pancreas connected to the duodenum?
Pancreatic duct
81
What happens in the intestines if pancreatic enzyme production is poor?
Foods ferment
82
What symptoms are a result of foods fermenting in the intestines?
Bloating Flatulence Abdominal pain Weight loss
83
What happens to digestive enzymes if eating too often and too much?
They get used up
84
What is the result of digestive enzymes being used up due to overeating?
Not all food is digested - malnutrition and bodily dysfunctions
85
What happens to organs such as the pancreas and stomach during overeating?
They are put under stress to produce digestive juices Capacity gets depleted Energy used to produce digestive enzymes is directed away from healing/repair
86
What percentage of daily energy expenditure is used by individuals eating a well balanced, nutritious diet to digest and absorb food?
10%
87
What percentage of daily energy expenditure is used by individuals eating dense forms of protein (meat/soya) and junk food to digest and absorb food?
50%
88
What are the implications of overeating and the excessive ingestion of animal proteins?
Compromises other bodily functions | Leads to fatigue, reduced immunity
89
What should individuals do to support digestive health?
Don't eat more than 3 meals a day Avoid overeating and snacking between meals Don't drink with meals
90
What did Bernard Jensen discover about overeating?
Undigested materials are stored in the mucus-secreting lining of the intestines Impairs the absorption and delivery of nutrients to body tissues The thicker the lining of undigested materials, the worse the absorption of nutrients
91
What can a lining of undigested materials lead to?
Parasites Candida Under-nourished body tissues and organs
92
How can we support the body's detoxification of wastes so they don't linger in the intestines?
Detoxification Intermittent fasting Dietary changes + vegetable broths
93
What is the function of the gallbladder?
Stores and releases bile
94
Where is bile initially produced?
Liver
95
What does bile consist of?
Water Bile salts Cholesterol Bilirubin
96
Outline the movement of bile from the liver to the SI?
Moves from liver to gallbladder via bile ducts | Moves from gallbladder to SI via common bile duct
97
What initiates the release of bile into the duodenum?
Ingestion of fats
98
Functions of bile
Breaks down lipids into smaller molecules, increasing surface area for pancreatic lipase Stimulates peristalsis Excretes detoxified products from the liver Excretes excess cholesterol
99
What are the implications of poor bile flow?
Affects fat digestion | Affects body's ability to eliminate toxins via bowel
100
Explain biliary tree
``` Bile is carried from hepatic ducts into gallbladder via cystic duct Upon CCK stimulation, gallbladder contracts and ejects bile Pancreatic duct (carrying pancreatic juices) meets the common bile duct and carries both through the sphincter of Oddi into duodenum ```
101
What is the adequate production and release of bile and pancreatic juice dependent upon?
Sufficient water consumption
102
What can stimulate the release of pancreatic juice and bile?
Bitters
103
Which vein transports all nutrients and toxins from the GIT to the liver?
Portal vein
104
How much blood does the liver filter every minute?
1.4 litres
105
Examples of nutrients stored by the liver
Carbs Fats Vits A, D, E, K, B12 Iron
106
Examples of liver functions
Detoxification | Deactivating hormones
107
Pathways that toxins can enter the liver
Lungs Skin GIT
108
Pathways that toxins can exit the liver
Lungs Skin Bowels Kidneys
109
What can impair liver detoxification?
``` Lack of essential nutrients Trans fats Heavy metals Alcohol Caffeine Pesticides ```
110
What happens to toxins that are only partially broken down?
They get recirculated
111
What happens during Phase 1 of liver detoxification?
Volatile toxins are converted into smaller, more stable water-soluble substances CYP450 enzymes create an active binding site on the toxin or hormone so it can be conjugated
112
What happens to the toxin once Phase 1 of detoxification is complete?
The toxin gets oxidised
113
What is created from the oxidation of the toxins at the end of the Phase 1 detoxification?
Free radicals
114
What is needed to neutralise the free radicals formed from the oxidisation of toxins during Phase 1 detoxification?
Antioxidants
115
What is needed to support the antioxidants neutralising the free radicals during Phase 1 detoxification?
Optimal digestion to ensure co-factors and AO are liberated from food
116
What happens during Phase 2 of liver detoxification?
Conjugation Chemical groups are bound to reactive toxins to make them safe and excretable The bound toxins are then pumped into the blood or bile for excretion mostly via the kidneys or bowels
117
Which nutrients are required for Phase 2 detoxification?
Sulphur Magnesium B vits
118
Food sources of sulphur
Garlic | Onions
119
Which herbs can support liver detoxification?
Dandelion Milk thistle Liquorice root
120
Which is the key AO needed for neutralising free radicals during liver detoxification?
Glutathione
121
Which proteins is glutathione made from?
Cysteine Glutamine Glycine
122
Which valve does any remaining undigested material go through to enter the LI?
Ileocaecal valve
123
What happens in the LI?
Final stages of digestion and absorption
124
How is digestion undertaken in the LI?
By microflora
125
What is produced by goblet cells in the LI?
Mucus
126
Are there any digestive enzymes in the LI?
No
127
What are the four regions of the LI?
Caecum Colon Rectum Anal canal
128
What is attached to the caecum?
Appendix
129
What does the appendix contain?
Immune tissue | Reservoir for beneficial gut bacteria
130
Regions of the colon
``` Ascending colon Hepatic flexure Transverse colon Splenic flexure Descending colon ```
131
Sphincters of the anal canal
Involuntary internal sphincter | Voluntary external sphincter
132
Four vitamins absorbed in the duodenum
Vits A, D, E, K
133
Four minerals absorbed in duodenum
Magnesium Iron Copper Selenium
134
Four vitamins absorbed in the jejunum
Vits A, D, E, K
135
Four minerals absorbed in the jejunum
Magnesium Iron Chromium Zinc
136
Four nutrients absorbed by the ileum
B12 | Vits C, D, K
137
Four nutrients absorbed by the LI
Water Sodium Potassium Chloride
138
Where can GALT clusters be found?
``` Tonsils Oesophagus Stomach SI Appendix ```
139
Which immunoglobulin is secreted into the GIT mucosa?
IgA
140
What reduces IgA production?
Stress
141
Functions of the LI microflora
``` Final stages of nutrient extraction Synthesises biotin and vit K2 Support intestinal barrier Protection from pathogens Regulates appetite Regulates mood ```
142
What happens during the final stages of nutrient extraction in the LI?
Microbial fermentation of remaining carbs and amino acids
143
What are the by-products of microbial fermentation in the LI?
Methane Hydrogen Hydrogen sulphide
144
What can excess flatulence with a strong odour indicate?
Poor digestion
145
What does the GI mucosal membrane protect against?
Ingested toxins Pathogens Undigested food
146
What happens to the GI mucosal membrane when damaged?
Tight junctions (that keep out toxins, pathogens, undigested food) become leaky allowing these larger molecules to enter circulation
147
What can be the result of gut bacteria abnormally entering the blood via a leaky gut
Excessive immune responses including allergies and autoimmunity
148
Examples of what can damage the intestinal barrier
``` Poor nutrition Heavy metals Drugs Stress Dysbiosis Candida overgrowth Alcohol Smoking Radiation/chemo Early weaning ```
149
How does the typical Western diet of refined sugars, trans fats, concentrated proteins and low fibre influence the diversity and dominant species in the gut microflora?
Makes the strains pathogenic
150
What does a diverse gut microflora help to support?
Immune system
151
What is the meaning of 'dysbiosis'?
Imbalance of the colonies of the gut microflora, leading to a disruption in health
152
What conditions can be associated with gut dysbiosis?
``` Vit/mineral insufficiencies Malabsorption of carbs/fats IBDs e.g. Crohn's Colorectal cancer AZD Parkinsons AI, allergies, intolerances Obesity Mood disorders ```
153
What are the physiological effects of eating junk food?
Gut dysbiosis - inflammation, reduced immunity, leaky gut Spikes in blood glucose - T2D, PCOS, obesity, acne CVD Vit/mineral deficiencies Addictive eating behaviour
154
What is the migrating motor complex (MMC)?
Pattern of electromechanical activity in the smooth muscle between the stomach and distal ileum during the periods between meals
155
What is the role of the MMC?
Sweeps residual undigested material through the digestive tube
156
How does the MMC sweep through residual undigested material?
Opens the pyloric sphincter | Increases gastric, biliary and pancreatic secretions
157
What role do the gastric, biliary and pancreatic secretions increased during the MMC help with?
Cleansing of the MMC | Assist in preventing SIBO
158
How can you support the functioning of the MMC?
Avoid overeating Minimise heavier proteins (animal based + soya) Leave longer gaps between meals Chew better Intermittent fasting Optimise sleep Stimulate the PSNS using diaphragmatic breathing Pro-kinetics (ginger, artichoke) and bitters before meals
159
What substances are key for the elimination of wastes via the bowels?
Water | Fibre
160
Which substances can also optimise bowel elimination?
Psyllium husk Aloe Linseed
161
What is the benefit of insoluble fibre?
Bulks up stool | Used for diarrhoea
162
What is the benefit of soluble fibre?
Softens stool | Used for constipation
163
What is considered the brain of the gut?
Enteric nervous system
164
What makes up the enteric nervous system?
Myenteric plexus | Submucosal plexus
165
What does the myenteric plexus govern?
GIT peristalsis
166
What does the submucosal plexus govern?
Digestive secretions
167
What is the role of the vagus nerve?
Stimulating activity in the digestive system
168
Where is the vague nerve located?
Extends from the head and travels through the thorax and diaphragm Innervates the digestive organs, connecting the brain and gut
169
When is vagus nerve activity suppressed?
During periods of chronic stress
170
When is vagus nerve activity enhanced?
With diaphragmatic breathing
171
What is the gut-brain axis
Brain and gut share many nerve endings and chemical transmitters Nearly every chemical that controls the brain has been identified in the GIT
172
What percentage of serotonin is produced in the gut?
95%
173
What is the function of serotonin?
``` Peristalsis Secretion Sensation Mood (hence link between gut health and depression) ```
174
How can dysbiosis affect serotonin production?
Affects the availability of tryptophan and co-factors needed for serotonin production
175
What is mindful eating?
Noticing your thoughts, feelings and sensations when eating
176
What are the implications of poor digestion?
Less nutrient absorption Fermentation of undigested food Retention of undigested materials in intestines Increased toxaemia
177
How is vit B12 absorbed in the body?
Bound to a protein called R-protein The complex enters duodenum and then split by pancreatic proteases which digest the R-protein The released B12 then binds to IF (produced by parietal cells in stomach) The B12-IF complex is absorbed in terminal ileum into blood
178
What can impair B12 absorption?
Poor gastric function Poor pancreatic function Damage to ileum
179
How is vit D3 synthesised from sunlight?
UV rays (sunlight) + provitamin D (skin cells) = cholecalciferol (D3)
180
What is needed to synthesise vit D?
Cholesterol
181
Which mineral converts vit D3/2 from sunlight/food in the liver and kidneys?
Magnesium
182
What can impair vit D synthesis?
Alcohol Drugs Coffee Refined sugars
183
What is the role of vit D in the digestive system?
Increases intestinal absorption of calcium and phosphorus Maintains calcium balance (with K2) Helps regulate bacterial species in intestines
184
What is needed to help absorb dietary vit D?
Healthy fats
185
How is digestive health crucial for bone health?
SI responsible for the absorption of Na, P, Mg, K + amino acids needed to build collagen Intestinal microflora produces K2 which causes calcium deposition in bones. Dysbiosis can result in osteoporosis
186
What is needed to absorb calcium from food?
Calcitriol
187
How is digestive health crucial to muscle health?
``` Ca - for muscle contraction Mg - for muscle relaxation Fe - helps deliver O2 to muscles Na/K - for nerve stimulation of muscles Amino acids - for muscle growth and maintenance ```
188
How is muscle health affected by poor absorption of key nutrients?
``` Muscle weakness Aching Cramping Fatigue Pain ```
189
How is muscle health also crucial in supporting digestive health?
Diaphragmatic movements provide a visceral massage on the abdominal digestive organs Stimulates the release of serotonin (promoting digestion and nutrient absorption)
190
Which foods are similar to haemoglobin so can be used as 'blood builders'?
Chlorophyll-rich foods e.g. green leafy veg Chlorella Spirulina
191
What is needed to aid the effective absorption of iron?
Stomach acid | Vit C
192
If the mineral supply to support the heart is depleted, where does the heart get its minerals from?
Bones Muscles Gums Arteries
193
What can using mineral stores from the bones, muscles, gums and arteries lead to?
Osteoporosis Cramps Receding gums Cellulite
194
How does the endocrine system support the digestive system?
``` Hormones released from GIT: Stimulate pancreatic juice and bile flow (CCK) Stimulate satiety (CCK) Stimulate gastric activity (Gastrin) Stimulate hunger (Ghrelin) Sugar absorption/storage (Insulin) ```
195
How does the digestive system support the endocrine system?
Provides nutrients for thyroid health | e.g. iodine, tyrosine, selenium, zinc
196
How is the nervous system supported by the digestive system?
Electrical activity relies on Na, K, Cl and Ca Neurotransmitter synthesis e.g. dopamine requires tyrosine, iron, B1, B3, B6 Axon myelination - B12
197
How can the nervous system be affected if digestive health is poor?
Tingling Numbness Loss of balance Pain
198
What are the dietary risk factors for cancer?
``` Red meats Refined sugars Low fibre Dairy (esp cow) Burnt, starchy food N-nitroso compounds Table salt Pesticides Artificial sweeteners ```

Nutrition 1 (Semester I) (15 decks)

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