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Y1 Nutrition & metabolism > Digestion & Absorption > Flashcards

Digestion & Absorption Flashcards

1
Q

Digestive system key features/

A
  • One long tube
  • Mucosa
  • Secretion & absorption
  • Muscle
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2
Q

6 process of digestive system

A
  • Ingestion
  • Secretion
  • Motility
  • Digestion
  • Absorption
  • Defaecation
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3
Q

Digestive system organs

A
  • Mouth
  • Salivary glands
  • Stomach
  • Pancreas
  • Gall bladder
  • Liver
  • Small intestine
  • Large intestine
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4
Q

Oral cavity

A
  • Mouth & pharynx
  • Mastication (chewing)
  • Voluntary & involuntary
  • Teeth (mechanical digestion)
  • Saliva (enzymes)
  • Tongue (mix, swallow)
  • Deglutition
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5
Q

Saliva

A
  • 3 glands provide 95% (1L per day)

- is mainly water, electrolytes, proteins (immunoglobin A, lysozyme), enzymes (amylase, lipase), lubrication

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6
Q

Salivary gland secretion function

A 
- Acinar (mucous cells)
secretion isotonic with plasma
- cells in the gland ducts actively reabsorb Na+ & Cl- & secrete some k+ & hco3- (alkaline = protection from acidic food)
- duct is impermeable to water
- Hypotonic salvia for lubricant
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7
Q

3 stages of swallowing

A
  • Buccal phase (bolus to back of throat)
  • Pharyngeal phase (bolus enters oesophagus, respiratory pathway closed)
  • Oesophageal phase (bolus moves down the oesophagus by peristalsis)
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8
Q

Oesophagus structure & role

A
  • mucosa, submucosa, 2 layers of muscle, circular then longitudinal
  • move food from mouth to stomach 4-8s (by peristalsis = circular muscle contracts longitudinal relaxes in progressive reoccurring wave
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9
Q

Oesophageal sphincter (role)

A
  • sphincter at the top of the stomach controlling what enters
  • closes when stomach is mixing to prevent acid reflux
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10
Q

Stomach structure (4 Parts)

A

Cardia - connected to stomach at the top
Fundus - above to the left of cardia, main storage
Body - mixing
Pylorus - connects to duodenum controls flow to small intestine
- can hold 6L

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11
Q

3 functions of the stomach

A
  • a reservoir
  • create chyme (acidic paste like soup) w/ gastric juice ( 3 waves a min)
  • regulating emptying of stomach
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12
Q

Absorption in stomach

A
  • some water & alcohol absorbed here

- order of foods leading stomach: carbs, proteins, lipids

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13
Q

Secretion in stomach

A 
Pepsinogen - chief cells
Lipases - chief cells
Intrinsic factor from parietal cells
HCL from parietal cells
ions mucus (mucous cells) (HCL activates pepsinogen)
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14
Q

mucus cells in stomach

A

they release mucus & bicarbonate ions (prevents damage from acidic environment)

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15
Q

3 phase of gastric secretion - Cephalic phase

A

Cephalic phase - 30% of response (happens before food arrives from taste & smell = gastrin = gastric juice secretion)

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16
Q

3 phase of gastric secretion - Gastric phase

A

Gastric phase - 60% response, ^ gastric juice, protein digestion

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17
Q

3 phase of gastric secretion - Intestinal phase

A

Intestinal phase - chyme entering duodenum, remove peptide fragements, decrease ph (duodenum distends = hormone release)

18
Q

3 accessory organs -

A
  • Pancreas, liver, gallballder
19
Q

Pancreas role

A
  • Endocrine cells produce hormones
  • Exocrine cells release digestive juice(caused by CCK+) - neutralises acids and stops pepsin
  • Enzymes - 50% CHO, 50% pro, 80-90% fat
20
Q

Liver role

A
  • Portal vein brings blood from digestive tract to pancreas/liver
  • Bile production
  • Metabolism (glucose/glycogen)
  • Processes drugs & hormones (detoxification)
21
Q

Pancreas role (bile)

A
  • Stores & concentrates bile (release stimulated by secretin & CCK)
  • 90% bile salts reabsorbed & recycled
  • Organ can be removed = 40% less lipids absorbed
22
Q

Small intestine role, structure

A
  • 3 parts - site of digestion & absorption
  • Mucosal lining
  • 2 layers of muscle
23
Q

Small intestine adaptations

A
  • Large SA
  • Villi, microvilli maximises absorption
  • Replaced 2-5 days
24
Q

Small intestine peristalsis

A
  • circular & longitudinal muscle can move food over short distances
  • Segmentation helps with mixing with pancreatic secretions
  • pacemaker cells keep bolus moving
  • intrinsic enteric NS (myogenic) detects stretch =
    ^ contractions
25
Q

Large intestine role, structure

A
  • Ileocecal sphincter (ileum to cecum)
  • reabsorb water
  • store faeces
  • bacterial fermentation
  • mass movement only 2-3 times a day
  • chyme here for 3-10 hours
26
Q

Timings of the whole system

A

Mouth -> stomach = 10 seconds
stomach = 2-4 hours
intestine = 3-10 hours
total = 24-72 hours

27
Q

Carbohydrate enzymes

A
  • Complex carbs digested (poly, tri, disaccharides must be hydrolysed to mono)
  • enzymes = glycosidases or carbohydrase’s
28
Q

Carb digestion

A
  • starts in mouth but most done in SI w/ pancreatic alpha amylase
  • mechanical & some chemical breakdown in mouth, none in stomach (acid)
  • lots in duodenum w/ debranching enzymes
29
Q

Carb absorption

A
  • Glucose & galactose facilitated with sodium through SGLT1 (sodium pumped into lumen to maintain gradient)
  • Fructose though glut 5 into intestinal wall
  • all 3 through GLUT 2 into blood (travels to liver)
30
Q

Protein digestion - stomach

A
  • HCL (from parietal cells) helps break down structure
  • Primary protease = Pepsin (active in stomach from inactive form - pepsinogen)
  • produces tripeptides
31
Q

protein digestion - SI

A
  • Pancreas secretes proteases (trypsin - also an activator)
  • enzymes also breakdown the gut lining for replacement
  • produces dipeptides & peptides
32
Q

Endo & exopeptidases

A

Endo - interior bonds

Exo - exterior bonds

33
Q

Protein absorption

A
  • Amino acids absorbed into capillary by sodium co transport or via diffusion
  • further breakdown will occur in the epithelial cell if required
34
Q

Fat digestion locations

A

mouth - lingual lipase (from serous gland)
stomach - 10-30% from gastric lipase
Duodenum - lipases, bile salts (CCK), bicarbonate
- Triglycerides broken into monoglycerides & fatty acids

35
Q

Fat digestion - Bile salts

A
  • Fats are hydrophobic
  • bile salts emulsifies fats -increases SA
    Enzymes - esterase’s, lipase, phospholipase, cholesterol esterase break down the triglycerides, phospholipids, sterols
36
Q

Fat absorption - short chains

A
  • short chain fatty acids (SCFA) diffuse into portal vein to bind with albumin
37
Q

Fat absorption - longer chains

A
  • Packaged into micelles which are absorbed into epithelial wall
  • packaged back into triglycerides (w/ fatty acids) and then into chylomicrons (/w Golgi body proteins)
  • Chylomicrons drain into the lacteal & are transported away
38
Q

Alcohol

A

in stomach alcohol dehydrogenase produces acetaldehyde (less intoxicating)
- food longer in stomach (eg because of a fatty meals) = less intoxicating because less alcohol in blood

39
Q

Vitamin absorption

A
  • Fat soluble - A,D,E,K follow fats to lymph system

- Water soluble diffuse straight across or actively transport depending on concentration

40
Q

Water absorption

A 
8 litres absorbed a day
6 litres secreted into GI tract
90% in SI
10% in LI
water follows osmotic gradient (hypotonic = ^ absorption)
Failure to absorb = diarrhoea

Y1 Nutrition & metabolism (11 decks)

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