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Human bio > Digestion and Microbes > Flashcards

Digestion and Microbes Flashcards

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1
Q

body composition with microbes by weight, number of cells, and genetic information

A

2% bacteria by weight
70% bactera by number of cells
99% bacteria by genes

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2
Q

microbe types of harmful relationships with humans

A

Amensal: microbe never establishes a sustainable population in or on human body

Pathogen

parasites

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3
Q

commensal relationship description

A

Their presence is not associated with disease.

Their absence is not associated with any change.

Commensal microbes may have:
‘Bad’/‘Good’ community state

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4
Q

good/bad community state

A

‘Bad’ community state: loss of health benefits for the host human

‘Good’ community state: delivers health benefits for the host human.

Change in microbial community is a risk factor for modern chronic diseases Most non-infectious chronic diseases are associated with microbe differences.

Change in microbial community activity state is strongly correlated with change in physiological health state of the host

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5
Q

mutualistic relationship description

A

a microbe must be essential for human health – no known mutualistic species of microbe whose presence is essential for human health

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6
Q

microbe locations

A

Stomach: Continually exposed to microbes, but very few actually grow there

Distal Small intestine (mainly ileum)
Site of stable occupation by microbes. Lower numbers than colon.

Large intestine (colon)
Has distinct conditions for microbial growth and far higher microbe cell density than ileum

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7
Q

microbe functions

A

Epithelial cell surface development

Gut vascularization

Maturation of gut tissues (EEC, GALT, ENS):

Immune functions
GALT (Gut-associated lymphoid tissue)

Endocrine functions
EEC (Entero-endocrine cells)

Neural functions
ENS (Enteric nervous system)

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8
Q

absence of microbes effects

A

Reduced digestive capacity

No adaptive immunity

Metabolic regulation is different – altered neuro-endocrine signalling pathways

Cognitive functions & mood are different – underdeveloped enteric nervous system

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9
Q

how do gut microbiomes influence the ability of animals to get enough food to live?

A

Quantity - Less food is eaten by animals that are colonized.

Quality - The diet fed to germ-free animals requires vitamin supplementation and a simple carbohydrate profile

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10
Q

what gets processed in colon?
[Hint: ai ai ee]

A

food that is:

Indigestible - chemically inaccessible to human enzymes (e.g. non-starch polysaccharides)

Inaccessible – particle structure prevents enzyme access (e.g. intact corn kernel)

Excess – exceeded digestion/absorption capacity of small intestine

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11
Q

why are most non-starch polysaccharide carbohydrates from plants ‘digestion resistant’?

A

presence of fibre

Plant cell walls are made of digestion resistant polysaccharides (e.g. cellulose, xylan).

Some storage polysaccharides of plants are also digestion-resistant (e.g. inulin, arabinogalactans)

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12
Q

how are microbes useful for digestion?

A

Microbes have a more variety of carbohydrate- degrading enzymes than humans

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13
Q

what can animal ezymes digest?

A

most fats and proteins in diet, but only a limited range of carbohydrates (starch and glycogen)

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14
Q

what are SCFAs?

A

SCFA (short chain fatty acids) are fermentation metabolites that are continuously produced during growth and are valuable energy sources for animals

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15
Q

what % of calories do humans absorb via colon microbes?

A

10 – 15% of calories absorbed via colon microbes

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16
Q

what type of metabolism do gut microbes perform?

A

fermentative metabolism

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17
Q

what phyla are most gut microbes from?

A

Bacteroidetes (10-90% of all cells)
Firmicutes (10-90% of all cells)

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18
Q

what does fermentation metabolism do?

A

converts simple carbs to carbon dioxide, hydrogen gas, and other ions (eg. acetate, propionate, mixed SCFAs)

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19
Q

what is sulfate reduction?

A

a specialised respiratory metabolism which converts SO4 and SCFA into CO2 and H2S

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20
Q

what factors influence our health in relation to microbial metabolites?

A

Food items/diet

Microbial activity

Types of microbes

Adaptive response

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21
Q

what factors influence microbiome management

A

nutrient type and amount determines population sie and activity of microbes (eg. fibre-digesting, etc)

other microbes - competition

immunity - Defence against pathogens involve:
1. Colonization resistance - normal microbes exclude pathogen
2. Barrier functions - mucin layer and epithelium.
3. Immune response functions

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22
Q

does the lumen or lamina propria tolerate bateria?

A

lumen yes, lamina propria no

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23
Q

immune functions down-regulation purpose and consequences

A

To avoid collateral damage to our cells

Increased susceptibility to infections and cancer are outcomes of weak immune response or immunodeficiency

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24
Q

immune functions up-regulation purpose for microbes

A

To exclude microbes from our body

Allergies, Autoimmunity and Inflammatory Bowel Disorders are diseases of inability to regulate immune response

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25
what influences immune tone?
signals from the gut microbiome that impact maturation of regulatory T and B cells
26
long-term/chronic diseases' main cause (even after initial infection is gone)
failure to regulate inflammatory response
27
complex and resolvable immune response to microbes [hint: DAMPs and MAMPs]
DAMPs - pro-inflammatory signals from cell damage (if microbe present or not) MAMPs - pro-inflammatory signals from microbes (including commensals)
28
what is dysbiosis?
diseases of a poorly functioning symbiosis, involving: “loss of resident microbe functions” – most notably contributions to regulation of immune tone “intolerance of normal microbes” – most notably chronic low grade intestinal inflammation
29
microbe exposure vs age
foetus: not exposed postnatal development occurs at the same time as microbe exposure
30
when does microbiome development end?
childhood (school age)
31
functions of digestive system
Ingestion Intake of food into the mouth Secretion Cells of the GI tract and accessory glands secrete acid, buffers, enzymes, hormones, mucus Motility Mixing and propulsion resulting from contractions and relaxation of muscle fibres Digestion (Chemical and mechanical) Breakdown of food into absorbable components. Mechanical digestion involves the physical breakdown of food into smaller particles Chemical digestion assisted via enzymatic activity to form absorbable compounds Absorption Mainly in small intestine Molecules pass into blood or lymph Protection Mucus & acidic fluid protect against pathogens Elimination Removal of wastes as faeces
32
4 Organic compounds
carbohydrates, proteins, lipids, nucleic acids
33
what gets absorbed from carbohydrates?
monosaccharides (mostly glucose)
34
what gets absorbed from proteins?
amino acids
35
what gets absorbed from lipids (mostly triglycerides)?
fatty acids
36
digestive system structures
Gastrointestinal tract (alimentary canal): Oral cavity Oesophagus Stomach Small + large intestines Accessory organs: Teeth Tongue Salivary glands Liver Gallbladder pancreas
37
4 layers of GI tract
mucosa, submucosa, muscularis externae, serosa/adventitia
38
function of mucosa
absorption (high SA) epithelium stops microbes from entering
39
function of submucosa
nutrient exchange (blood vessels for transport to the body)
40
Muscularis externae function
Contains layers of smooth muscle for peristalsis pushes food down 2 layers of muscle
41
Serosa/adventitia function
Allows for gliding movement between GI tract and other organs
42
oral cavity function
salivary amylase digests starch to maltose ingetsed food --> bolus (ball of food) for ease of swallowing physical immunity: lysosyme in saliva breaks down bacterial cell walls
43
oesophagus function
propels bolus to stomach via peristalsis
44
peristalsis definition
involuntary constriction and relaxation of muscles to move food
45
oesophagus muscle type distribution
top: skeletal bottom: smooth
46
stomach function
pepsin breaks down protein into peptides NO water reabsorption
47
stomach contractions speed reasons and effects
slow - peristaltic contractions push bolus towards pylorus (~3 contractions/min) restricted flow rate - pylorus allows 1/10 of chyme it holds to pass through pyloric valve per contraction. The rest is pushed back up (retropulsion) for further mechanical and chemical digestion reason: this is slow to prevent rapid water movement from blood to intestinal lumen due to osmosis and to allow chyme acidity to neutralise contractions close pyloric valve and remaining contents are propelled back (retropulsion)
48
pylorus location
most muscular part of stomach (towards the end)
49
stomach sphincters (muscular valves) and their functions
prevention of backflow Gastro-oesophageal sphincter Pyloric sphincter
50
HCl function in stomach
HCl in gastric juice (secreted by gastric glands) denatures proteins and converts pepsinogen to pepsin
51
what happens to pepsinogen in stomach
Activated to pepsin in the presence of HCl Not pepsin permanently as gastric juice is very acidic and would degrade the stomach lining
52
what are rugae
Folds of stomach's mucosa Increases SA for contact between bolus and gastric juices
53
where are gastric glands
columns of specialised cells extending from mucosa to submucosa
54
elements of gastric juice
gastrin (stimulates HCl and pepsinogen secretion) pepsinogen HCl bicarbonate-rich mucous (prevents acid corrosion and stomach wall protein digestion) intrinsic factor (for transport and B12 absorption in small intestine)
55
small intestine regions and lengths [hint: a DJ I think is cool]
Duodenum, 20-25 cm, closest to stomach Jejunum, ~2.5 m Ileum, ~3 m, closest to the large intestine
56
where does small intestine's ileum join the large intestine's caecum?
at ileocecal sphincter
57
villi
Specialised features of small intestine increase surface area for absorption finger-like projections of mucosa layer into the lumen
58
microvilli
Specialised features of small intestine increase surface area for absorption hair-like projections of enterocytes (absorptive cells) found on villi
59
small intestine function
digestion of organic compounds (Carbohydrates, proteins/peptides, lipids, and nucleic acids)
60
where does digestion mainly occur in small intestine? [hint: D for digestion]
duodenum
61
small intestine movement of chyme [hint: J for jolt]
peristalsis (~16 contractions/min) in the jejunum: localised contractions and relaxations move chyme back and forth a few centimetres, promoting mixing and absorption of nutrients and water
62
what does the small intestine absorb
products of protein and carbohydrate digestion electrolytes/ions + water vitamins
63
bile function
formation of micelles with water-insoluble products of lipid digestion, cholesterol, fat-soluble vitamins for suspension in chyme purpose: so lipids do not float and be eliminated in faeces Fatty acids in micelle then transferred to enterocytes (absorptive cells)
64
large intestine regions [hint: CCRAC]
caecum, colon, rectum, anal canal
65
large intestine digestion
resident bacteria Insoluble carbohydrates --> short-chain fatty acids (SCFAs) via fermentation
66
large intestine absorption
remaining water and electrolytes, vitamins made by resident bacteria, insoluble carbs that have become SCFAs
67
bile production
liver secretes bile gallbladder stores and concentrates bile by absorbing water and ions
68
large intestine movement of chyme
Haustral contractions localise chyme Occurs every ~30min and each contraction lasts ~1min Aids with mixing and water & electrolyte absorption
69
peristalsis frequency in large intestine
3-4 times/day Allows for mass movement of content towards rectum
70
pancreas exocrine cells secretion [hint: PLAN the enzymes]
Exocrine cells secrete pancreatic juice made from: Water Bicarbonate ions (neutralises HCl from stomach) Pancreatic proteases Pancreatic amylase, lipases, nucleases
71
jejunum absorption (small intestine)
carbs, amino acids/peptides 80% electrolytes 90% water
72
ileum absorption (small intestine)
lipids (transported by micelles)
73
where is amylase found?
oral cavity (saliva) and duodenum (small intestine)
74
digestive enzyme names and production
Carboxypeptidase is released by the pancreas. Pepsin is released in the stomach Sucrase and lactase are released in the small intestine. Amylase is released in saliva and small intestine

Human bio (9 decks)

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