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Physiology 1 : GI > Functions and control of the alimentary tract > Flashcards

Functions and control of the alimentary tract Flashcards

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1
Q

What are the digestive functions of the stomach?

A

→ Accommodation and storage
→ Mechanical and enzymatic breakdown
→ Slow delivery of chyme to the duodenum

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2
Q

What does the vagal reflex inhibit?

A

→ Smooth muscle tone
→ Mechanoreceptors
→ Fundic relaxation

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3
Q

Where is the antral region?

A

→ Lower region of the stomach

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4
Q

What are physical properties of the antral region?

A

→ Thick and muscular

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5
Q

What does the antral region do?

A

→ Mixes/grinds food with gastric secretions

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6
Q

What does the stomach act as?

A

→ A reservoir for unmixed food

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7
Q

What allows a large volume of food to be stored in the stomach?

A

→ Fundus and the body of the stomach relax

→ 1.5 L storage

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8
Q

What two nerves are involved in receptive relaxation?

A

→ parasympathetic nerves

→ Vagus inhibitory nerves

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9
Q

How much gastric juice does the stomach store?

A

→ 2-3 L

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10
Q

What does gastric juice contain and what is the function of it?

A 
→ mucus
→ Pepsinogen 
→ intrinsic factor 
→Lipase 
→ helps in digestion + absorption of food
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11
Q

What does mucus do?

A

→ Acts as a lubricant by acting as a barrier that protects the stomach and colon especially from gastric acid

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12
Q

What does lipase do?

A

→ Converts triglycerides into fatty acids and glycerol

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13
Q

What does pepsin do?

A

→ Protein digestion

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14
Q

What is pepsin secreted by?

A

→ Secreted by chief cells or peptic cells

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15
Q

What is HCL secreted by?

A

→ Parietal cells

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16
Q

What is mucus secreted by?

A

→ Goblet cells or mucus cells

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17
Q

What are paracrine secretions?

A

→ Secreted from cells in the mucosa but the chemical acts locally on adjacent cells via interstitial fluid

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18
Q

What does somatostatin inhibit?

A

→ Gastric release in the stomach

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19
Q

What is somatostatin released by and what does it act on?

A

→ D cells and acts on G cells

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20
Q

Where are exocrine secretions secreted from?

A

→ Salivary glands
→ Gastric glands
→ Pancreas
→ Liver

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21
Q

What are endocrine secretions?

A

→ Hormones synthesized by ductless glands

→ Enter the bloodstream and travel to their target tissues where they bind to specific receptors to elicit their effects

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22
Q

What is gastrin secreted by?

A

→ G cells of the stomach

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23
Q

What are secretin and pancreozymin-cholecystokinin produced by?

A

→ Duodenal mucosa

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24
Q

Where is insulin secreted from?

A

→ Pancreas beta cells

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25
Where does absorption of fluid occur?
→ Small intestine + colon
26
What does the colon absorb and what does it produce?
→ Colon absorbs 90% of water reducing volume to 200ml of semi solid fecal matter
27
What produces mechanical degradation?
→ The gastric antrum
28
What mixes the lumen contents?
→ The small intestine
29
How do drugs and normal products of metabolism leave the body?
→ saliva → bile → feces → vomit
30
How does indigestible material leave the body?
→ Via feces
31
What does the gut epithelium act as and what is it exposed to?
→ Interface with the outside world | → Exposed to the external environment
32
What helps protect the gut from external pathogens?
→ Sight, smell and taste → Vomit reflex → Acid in the stomach kills most harmful bacteria → Mucus secretions → Natural bacteria flora prevent colonization by harmful bacteria → Aggregation of lymphoid tissue can mount a response against food-borne antigens → Peyer's patches
33
What is the liver involved in?
→ Carbohydrate, nitrogen and lipoprotein metabolism | → Production and excretion of bile + bilirubin
34
How can the gut initiate its own responses?
→ It has an enteric nervous system which can initiate its own responses to gut stimuli without higher functions of the brain
35
What are the contractions initiated by?
→ Excitatory reflexes and mediated by AcH or substance P
36
What are relaxation effects mediated by?
→ VIP or NO
37
What are splanchnic nerves?
→ Sympathetic
38
When does receptive relaxation occur?
→ Which happens by mechanical stimuli → Food is expected in the stomach → Sphincter relax to allow food to enter
39
When does adaptive relaxation occur and with what neurotransmitter?
→the food is within the stomach →NANC →Inhibitory AcH effect, preganglionic The factors that induce relaxation is not AcH itself the post-ganglionic is mediated by NO and VIP
40
What is feedback relaxation initiated by?
→CCK
41
Why is CCK being released?
→ Due to lipids being in the food
42
What does CCK do?
→ Decreases feeding because relaxation is occurring
43
What does CCK promote?
→ Bile secretion | → Gall bladder contracting
44
How does food move through the duodenum?
→ Ripples of contraction move the food towards the antrum (thicker muscle layer) →Pyloric sphincter is often relaxed but closes upon arrival of peristaltic wave →Repulsion of chyme causes the opening of pyloric sphincter →Small partially digested material is squirted through the pyloric sphincter into duodenum →Repulsion of antral contents backwards towards the body allows mixing/grinding
45
What is the sieving effect?
→ Viscous and solid matter are retained in the stomach →pylorus can detect the size of food particles, 1-2mm are passed through →anything larger goes back to the antrum for grinding.
46
When is somatostatin released?
→ When there is hypersecretion of acid
47
What does the vago-vagal reflex describe?
→ type of reflex in which both the afferent (“sensory”) and efferent (“motor”) axons are in the vagus nerve trunk
48
What kind of circuit is the vago-vagal reflex?
→ Reflex circuit within the GIT
49
What does the vago-vagal reflex control?
→control of responses to gut stimuli via the NTS and DMVN
50
When is the vago-vagal reflex active?
→ during the receptive relaxation of the stomach in response to swallowing
51
Where does the vago-vagal reflex go from and to?
→from stomach to brain and then back to stomach
52
What does the vago-vagal reflex promote?
→motility and acid secretion
53
What two nerve fibers are intrinsic to the gut and what are they for?
→Myenteric plexus - motor function | → Submucosal plexus - Intestinal secretions
54
What do the two plexuses do?
→ Reflexely regulate GI functions entirely within the wall of the gut →Mediated by enteric nervous system
55
How are the two plexuses connected to the CNS?
→ parasympathetic and sympathetic fibres
56
What are the neurotransmitters used in the plexuses?
→ ACh, NO, NA, 5-HT, GABA and ATP
57
Where are the two plexuses found?
→ The wall of the colon
58
What does parasympathetic activity do to the colon?
→ Increases the contraction of the proximal colon
59
What effects does the cholinergic innervation have on the auerbach plexus?
→ Increases gastric motility and secretion
60
What effects does adrenergic stimulation have on the Auerbach plexus?
→ Decrease in gastric motility and secretion
61
What does the rate of emptying depend on?
→ THe materials ability to be absorbed
62
How do carbohydrates, proteins and fats get emptied?
→ Carbohydrates are emptied quicker → Proteins have slow emptying → Fatty foods have even slower emptying
63
What is the result of having fatty foods in the duodenum?
→ Decrease in gastric emptying by increasing the contractility of the pyloric sphincter
64
What is peristalsis like in the large intestine compared to the small intestine?
→ Slower in the large intestine
65
What initiates contraction (peristalsis)?
→ Distension
66
How does the bolus get moved along?
→ Contractions are initiated by excitatory activity mediated by substance P and AcH → The circular muscles have to relax infront and contract behind →Longitudinal muscles are contracted
67
Where are Peyer's patches found?
→Lamina propria of the mucosa extend into the submucosa of the ileum

Physiology 1 : GI (15 decks)

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