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🚌 GI Flashcards

i ignored the notes part

1
Q

What happens after a vagotomy?

A

vagal nerves cut ∴ ↓accommodation + gastric compliance

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2
Q

What happens to food after accommodation?

A

moved from gastric reservoir ➩ antral pump –> Stomach thrown➩ folds –> mix/grind of chyme–>squirt food via sphincter

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3
Q

How is food moved ➩ antral pump?

A
  • Tonic contraction = produced by fundus pacemaker cells mins-hrs
  • Peristaltic 🌊 in body
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4
Q

What does proximal stomach do?

A

relaxes to store food at low p whilst broken down acid, enzymes, 𝔼,mechanically

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5
Q

Why is gastric emptying regulated?

A

Coordinates mechanical/chemical breakdown with absorption
Reduces swamping of duodenum with acidic chyme
Particles that are large cannot pass the pylorus

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6
Q

What’s gastric stasis (gastroparesis)?

A

chronic condition when stomach cannot empty normally –>food pass slowly

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7
Q

How’s gastric motility/emptying regulated?

A

Excitatory reflex from stomach

❌ reflex from small intestine

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8
Q

What’s the excitatory reflex?

A

food causes distention–> excitatory reflex–>food ➩ distal stomach–>antral pump switched ON + intensified to prolong relaxation..

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9
Q

What’s the ❌ reflex?

A

from antrum descending❌ reflex causes pyloric relaxation- NO/VIP–> antral contraction –> food➩pylorus–> food is the duodenal stimuli–> sends ascending excitatory reflex causing pyloric contractions so closed until chyme neutralised

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10
Q

What’s reciprocal vagal control?

A

accomodation ⇶Ach–>contractions + NANC ⇶⇑VIP/NO–> relax

emptying ↑cholingeric + ↓NANC

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11
Q

What’s gastric emptying dependent on?

A

Propulsive force by tonic contractions

Stomach’s ability to differentiate food + their components- liq/solid

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12
Q

Liq emptying?

A

🏃‍♂️disperse, no lag time, pass in spurts, if ↑nutrient then retained longer

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13
Q

Solid emptying?

A

2 phases: lag time+ linear phase
Liq part emptied + solid retained in proximal stomach
Trituration of larger particles →small 2mm
60min

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14
Q

What does lag time depend on?

A

particle size

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15
Q

Fatty foods emptying?

A

Liq at body temp∴float on top of liquid layer∴SLOW

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16
Q

Indigestible solids emptying?

A

Not emptied in immediate post-prandial period

MMC activity

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17
Q

Determinants of motility rate?

A

Food : carb>🐟>fat>indigestible
Osmotic p of duodenal contents : hyperosmolar chyme ↓ gastric emptying
Vagal innervation > over-distension : ↓motility
Hormones(somatostatin, secretin, CCK, GIP): ❌ emptying
Injury + infections : ↓ motility

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18
Q

What controls gastric motility myogenically?

A

Intestinal Cajal Cells

Basic Electrical Rhythm

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19
Q

What’s ICC?

A

Specialised pacemaker cells located in the wall of stomach, small+large intestine
Membranes undergo rhythmic depolarisation + repolariation which creates BER

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20
Q

What’s BER?

A

determines the ƒ of the contractions in the GI, when at max it produces smooth muscle cell contraction so depolarises + contracts rhythmically when exposed to hormonal signals

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21
Q

Process of myogenic control of motility?

A

ICC in fundus produce depolarisation from RMP–> ripples move to antrum - BER 3 waves/min

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22
Q

What ↓BER?

A

Sympathetic - NA/A on the GI smooth muscle
Depolarisation of GI smooth muscle by Ca/Na influx
Repolarisation of GI smooth muscle by K+ efflux

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23
Q

What ↓ fundic motor activity?

A 
GRP
Cholecystokinin (CCK)
Secretin
VIP
Somatostatin
Glucagon
Duodenal distension, duodenal acid
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24
Q

What ↑ fundic motor activity?

A

Motilin

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25
What ↑ intestinal motility?
CCK, gastrin, motilin | serotonin, insulin
26
What ↓ intestinal motility?
Secretin
27
What are the -ve feedback systems of gastric emptying?
Antral over-distension: Vago-vagal reflex | Duodenal over-distension + chemical stimulation: Vago-vagal reflex + hormones
28
Types of motility control along alimentary tract?
Segmentation Peristalsis Migrating Motor Complex MMC Mass movements
29
Phases of motor activity?
I: quiescence/quiet period <12hrs II: irregular propulsive contractions III: burst of uninterrupted phasic contractions (peristaltic rush)
30
What's segmentation + process?
Contractions churn + propel food ➩ anus Originates in ICC-->÷ -->sub÷ of chyme w contents∴ contact w intestinal walls for absorption--> slow migration of chyme ➩ ileum Duodenum/jejunum: 10-12 contractions/min Ileum: 8-9 contractions/min
31
What's peristalsis + process?
Spreads food allowing 𝔼 to mix + global movement | Propagating contractions of sucessive sections of circular muscle--> relaxation where bolus moving-VIP/NO
32
How to regulate peristalsis?
neural reflexes - Sensory neurones detect stimulation of the bolus via cholinergic interneurones -->❌ motor neurones ⇶ VIP/NO-->relax circular in front of bolus - Excitatory motor neurones ⇶ Ach/Substance P-->contracts behind bolus
33
What's MMC?
Highly organised motor activity,cyclically recurring seq of events between meals when 'empty' -phase III
34
Process of phase III?
From lower stomach-->burst of high ƒ, large amplitude contractions migrating along intestine then die out 90-120min intervals
35
Functions of MMC?
“Intestinal housekeeper” Removes indigestible out stomach ∵ contractions + wide sphincter Removes dead epithelial cells by abrasion Prevents 🐛 overgrowth Prevents colonic 🐛entering small intestine
36
Control of MMC?
?-Stomach cells produce “slow 🌊” --> contractions are coordinated by ICC--> initiated by the vagus in upper GI -Cyclical secretion of MOTILIN from stomach + duodenum
37
What's the motor activity when fed?
``` Segmentation Peristaltic contractions (slow waves) ```
38
What does large intestine do?
Absorption of H2O+ions-->🐛-->storage of waste-->elimination
39
What are 'fermenting chambers'?
allow the hydrolysis of fibre + indigestible
40
Features of motility in the large intestine?
Intensive missing Fermentation Slow propagating- slow aboral flow
41
Function of taenia coli longitudinal muscle?
Segmental/haustral contractions-mix contents
42
Peristalsis in large intestine?
slow, moves contents ➩anus, distension initiates contraction
43
How is mass movement in large intestine?
powerful contraction of mid-transverse colon that sweeps colon contents ➩ rectum-for colonic evacuation
44
What's diarrhoea?
frequent (>3x/day) liq faeces
45
What's constipation?
difficulty opening + emptying bowels hard faeces
46
Functions of alimentary?
Absorption of nutrients, salts and water Absorption of fluid ⇶small intestine back➩blood Absorption by transport of ions Colon absorbs 90% of the H2O from the contents -->semi-solid material ~200ml
47
Diff between Marasmus vs Kwashiorkor
- Undernourishment -->sig low weight for child's age | - Insufficient 🐟-E malnutrition -->oedema, irritability, enlarged liver w fatty infiltrates
48
What are villus cells?
Involved with ABSORPTION +⇶HCl for gastric use
49
What are crypt cells?
Base of villus, involved in SECRETION,defence,signalling,replenish epithelial cells up the villi by stem cells
50
What mediates intestinal digestion + absorption?
Enterocytes-villus + crypt
51
🚌 methods across enterocytes?
``` Transcellular= transport of solutes by a cell via cell eg glucose from lumen to extracellular fluid via epithelial cells Paracellular= passage of Na+,Cl-,H2O between cells via tight junctions, passive, variable, regulated ```
52
What's carb digestion + absorption?
Only monosaccharides absorbed Complex carbs→disaccharides by amlyases Specific brush border enzymes convert di→ mono (eg glucose +galactose
53
E value of carb?
17.5 kJ/g
54
Where does carb digestion occur?
intestinal lumen + brush border
55
Types of brush border 𝔼 for carb?
Sucrase: sucrose→glucose + fructose Glucoamylase : glucose oligomers → glucose Lactase : lactose→ galactose + glucose
56
Types of intestinal lumen 𝔼 for carb?
salivary + pancreatic amylase
57
What are glucose oligomers?
molecular complex that has few monomer units eg maltotriose (trisaccharide)
58
What's maltotriose?
has 3 glucose linked w α-1,4 glycosidic bonds + produced by α-amylase on amylose in starch
59
How's glucose + galactose absorbed via enterocytes?
🏃‍♂️ by luminal glucose carrier system actively
60
How's fructose + mannose absorbed via enterocytes?
slowly by GLUT 5 on basolateral membrane
61
Process of glucose + galactose absorption?
Cytoplasmic Na+ pumped out via basolateral membrane (close to the blood)-->intracellular electrochemical gradient-->Na+ enters enterocytes w glucose via glucose/Na+ co transporter SGLT1-->Glucose enters blood via GLUT-2
62
What's a competitive ❌ of glucose 🚌?
Galactose
63
Process of fructose absorption?
GLUT5 + GLUT2 on enterocyte-->GLUT 5 on basolateral membrane
64
What's mannose?
Sugar monomer of the aldohexose series of carbs
65
What digests 🐟?
pepsin: →polypeptides
66
What digests polypeptides?
pancreatic proteases: →di-/tri-peptides
67
What digests di-peptides?
di-peptidases: →AA
68
Why is diffusion is more vital for the basolateral transport of AA?
basolateral membrane more permeable to AA than brush border membrane
69
What do cytoplasmic peptidases do?
cleave the di-peptides →AA
70
Where does 🐟 digestion occur + how?
-Intestinal lumen–pepsins +pancreatic proteases :proteins →oligopeptides+AA -Brush border–specific peptidases : oligopeptides→ di/tripeptides + AA (absorbed → enterocytes) -Enterocytes–cytoplasmic peptidases : di/tripeptides → AA --> pass→ blood
71
What are the mechanisms of 🐟 absorption?
- AA 🚌on a Na+/AA carrier like glucose,(separate carriers for diff AAs) --> AT from enterocyte→blood --> 🚌liver via portal vein - Some di-/tri-peptides 🚌using H+ grad
72
What are diff types of dietary lipids?
TG 90%, phospholipids, cholesterol, fat soluble vitamins A,D,E,K
73
Where's lipid digestion?
Mouth: salivary lipase | SMALL INTESTINE
74
Why's TG dissolved in aq before digestion?
Lipases are soluble so TG emulsified by chyme
75
Optimal lipid in diet?
20% - fish + olive oil
76
What digests lipids?
Gastric lipase 10-30% of fats | pancreatic lipase rest
77
What facilitates digestion + absorption of lipids?
Emulsification | Micelle formation
78
Where does emulsification happen?
In duodenum by bile salts
79
Process of emulsification?
Bile emulsification --> emulsion droplets--> pancreatic lipase binds to the hydrophilic+emulsion droplets bind to the hydrophobic region of the colipase-->digestion of emulsion droplets
80
Function of sphincter of oddi?
Controls the flow of bile + pancreatic juice via ampulla of Vater
81
Where do bile salts come from?
Bile salts produced in liver, stored in gallbladder, comes down common bile duct, joins w pancreatic duct which ⇶pancreatic lipase + colipase
82
Function of colipase?
dissolves lipid in aq ∵ amphipathic-hydrophilic + hydrophobic regions
83
How fat droplets broken down?
muscular actions-->bile salts (prevents combining)
84
How micelles formed?
bile salts form a layer of phospholipids around digested lipids
85
Why micelles?
200x smaller than emulsion droplets so small enough to fuse w enterocytes via pinocytosis
86
What's a micelle?
lipid∞arranged in spherical form in aq | Bile salts, monoglycerides,free FA, cholesterol, vit A,D,K
87
What happens after micelle fuses w enterocyte?
- Short chain free FA enter portal vein, combine w bile in the liver to form more micelles via lipases - FA + monoglycerides = TGC, packaged w cholesterol, phospholipids, apolipoproteins ➩ chylomicrons-->🚌 to lymph
88
How chylomicrons enter the lymph?
via lacteals--> 🚌via lymph vessels➩blood(via thoracic duct near the neck connect w left subclavian vein)→ wall of capillaries →FA → liver + fat cells
89
Function of lipoprotein?
allow fats to move through the H2O inside+outside cells
90
Types of lipoprotein?
``` LDL = has ↑fat, 🚌 fats → adipose tissue, clogs HDL = carries fats to liver for recycling + excretion ```
91
Role of albumin?
FA 🚌to target cells
92
What happens if there's absorption of many chylomicrons?
lymph draining from the small intestine looks milky
93
What leads to fat malabsorption
gallstones, pancreatitis, Crohn's,liver disease
94
Where are triacylglycerols of chylomicrons + VLDL hydrolysed?
Golgi by lipase
95
What's Steatorrhoea?
fatty stools which smell and float Intestinal discomfort Body is deprived of fat-soluble nutrients, e.g. Vits A, D, E, K

GI (15 decks)

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