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MD1 GI - EXAM 1 > Physiologie digestive > Flashcards

Physiologie digestive Flashcards

1
Q

What are the functions of the esophagus?

A

Secretion of bicarbonate and lubricant (submucosal glands)

Absorption: N/A

Motility: swallowing and peristalsis —> transfer and transport of the bolus

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2
Q

How does swallowing work?

A

Function: transport and protection of airways

Uses striated skeletal muscles —> voluntary

  • Initiated voluntarily but completed by reflexes
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3
Q

Which nerves control swallowing?

A

9: mostly sensory, taste in the 1/3 posterior portion of tongue, motor of the stylopharyngeal muscle

10: (vagus nerve)

  • sensory: pharynx, larynx, organs of the GI tract, taste
  • motor: soft palette, pharynx and phonation

12: activates muscles in tongue which propulses bolus to pharynx

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4
Q

What are the phases of swallowing?

A
  1. phase volontaire: bolus to the palate
    • (preliminary inspiration)
  2. phase pharyngée:
    • reflex: cranial nerves (9, 10, 12) —> 26 mucles
    • soft palette closes nasopharynx
    • epiglottis closes larynx
    • vocal cords close (can’t talk when swallowing)
    • relaxation of the superior esophageal sphincter (cricopharyngeal muscles)
    • irreversible propagation of the peristaltic wave
    • relaxation of the lower esophageal sphincter
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5
Q

How does peristalsis in the esophagus work?

A

Sequential relaxation and contraction —> involuntary propulsion of bolus orchestrated by reflexes (intermuscular plexus)

Around 4cm/s

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6
Q

What are the 3 kinds of peristaltic waves?

A
  1. primary peristaltic wave: peristalsis initiated by swallowing
  2. secondary peristaltic wave: if something is stuck… wave around the bolus, forcing it further down the esophagus, and these secondary waves continue indefinitely until the bolus enters the stomach
  3. tertiary peristaltic wave: dysfunctional and involves irregular, diffuse, simultaneous contractions
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7
Q

What are the functions of the stomach? (6)

A
  1. storage: diameter can change to accommodate food
  2. sterilization using gastric acid
  3. chemical digestion: acid, pepsin
  4. mechanical digestion: trituration
  5. timed optimal emptying into small intestine through pylorus
  6. appetite: ghrelin hormone, vagus nerve
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8
Q

What is secreted into the stomach by the parietal cells?

A

HCl and F.I (B12)

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9
Q

What is secreted into the stomach by the cellules principales?

A

pepsinogen, lipase

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10
Q

What is secreted into the stomach by goblet cells?

A

Mucus

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11
Q

What is secreted in the stomach by G cells? (hormone)

A

Gastrin which stimulates acid production

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12
Q

What is secreted in the stomach by ECL cells? (hormone)

A

Histamine

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13
Q

What is secreted in the stomach by D cells? (hormone)

A

Somatostatin (dodo)

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14
Q

What is secreted in the stomach by P/D cells? (hormone)

A

Ghrelin

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15
Q

How are gastric cells regulated?

A

3 ways: can also be modulated by drop in pH

  1. neurocrine: ACh and NA
  2. endocrine: gastrin and ghrelin
  3. paracrine: histamine and somatostain
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16
Q

How does gastric motility work?

A

3 steps:

  1. Relaxation réceptive
  2. Trituration
  3. Contrôle de la vidange gastrique
17
Q

How are things absorbed in the small intestine?

A

Trans or paracellular absorption

Cells: enterocytes, linked together by jonctions serrées

18
Q

How does the small intestine have such a large surface area?

A

La surface de contact des entérocytes avec le contenu luminal est décuplée par :

  1. Bordure en brosse : la membrane cellulaire de chaque entérocyte du grêle est augmentée par une multitude de micro-villosités.
  2. Villosités : une organisation des entérocytes en longues villosités qui baignent dans le chyme
  3. Plis circulaires : la surface de la muqueuse forme des plis circulaires dans le tube musculaire du grêle.
  4. La longueur du tube : la longueur du tube digestif excède de beaucoup la distance de la bouche à l’anus.
19
Q

What are the roles of the apical surface of enterocytes? (2)

A

release of peptidase and disaccharidase

transporters for simple/double sugars, simple amino acids, di and tripeptides, vitamins, biliary salts and fatty acids

20
Q

What are the roles of the cytoplasm of enterocytes?

A

further breaking down some di and tripeptides

location for assembly of chylomicrons

21
Q

What are the roles of the basolateral surface of enterocytes?

A

Location of Na+/K+ ATPase

22
Q

Where are carbohydrates digested?

A
  1. mouth —> salivary amylase (20-40%)
  2. intestinal lumen —> pancreatic amylase (60-80%)
  3. bordure en brosse intestinale —> dissacharides
    1. lactase: lactose into glucose and galactose
    2. sucrase: sucrose into glucose and fructose
    3. isomaltase: maltose into 2x glucose
23
Q

Where are “carbs” absorbed?

A

Once broken down into simple sugars, absorbed completely in proximal small intestine and then passed through systemic circulation to liver

24
Q

Where are proteins digested?

A

stomach: hydrolyzed by HCl and pepsin

intestinal lumen:

  1. pancreatic juices: trypsin and chymotrypsin
  2. bordure en brosse: peptidase
  3. intracellular: cytoplasmic peptidase
25
Q

Where are proteins absorbed?

A

by specific receptors for 99% of ingested proteins

26
Q

Where are lipids digested?

A

mouth —> lingual lipase (minor)

stomach —> gastric lipase (minor)

pancreas —> pancreatic lipase (MAJOR)

liver —> bile (bile salts and cholesterol)

intestinal lumen —> pancreatic lipase

  1. triglycerides —> AG + glycerol
  2. cholesterol and phospholipids —> cholesterol ester hydrolase and phospholipase (degradation products)
  3. bile salts emulsify fats and create micelles in order to emulsify them

and then all transported to bordure en brosse

27
Q

Where are lipids absorbed?

A
  1. brought by micelles to bordure en brosse
  2. transferred into cytoplasm and reformed into triglycerides and cholesterol
  3. transported into lymphatic vessels by lipoproteins and chylomicrons NOT IN BLOOD THEREFORE NOT TO LIVER RIGHT AWAY
  4. absorbed in medial and distal small intestine and bile salts in the terminal ileum

95% of lipids ingested are absorbed

28
Q

Overview of digestion and absorption:

A
29
Q

Where are vitamins absorbed?

A

Liposoluble (A, D, E, K):

  • Absorbed with lipids due to pancreatic enzymes and formation of micelles

Hydrosoluble (B1, B2, B3, B6, B12, C, Biotin, Pantothenic Acid):

  • Absorbed in proximal small intestine
30
Q

How is vit. B12 metabolized?

A
31
Q

Where are minerals absorbed?

A

Ca2+

  • transcellular and paracellular when in high concentrations
  • active transport in duodenum and jejunum

Mg+

  • paracellular in ilium

Fe2+

  • only 10-20% absorbed… happens in duodenum and proximal colon
32
Q

What is the job of the colon?

A

NO ENZYMES

Absorbs water (sodium pump)

Secretes mucus for lubrification

33
Q

How does the colon move things?

A

NOT PERISTALSIS

Two arrangements of muscles:

  1. circular muscles —> creates haustrations (segmentations)
  2. longitudinal muscles —> creates 3 teniae coli

Intermittent contractions of the long sections of the colon —> 2-3 days for fecal matter to pass through

Ileocecal valve (between ilium and colon) is unidirectional

34
Q

What is the main function of the rectum?

A

Evacuation/continence

The rectum is sensitive —> tension receptors

  1. besoin exonérateur: perception conscience
  2. accomodation: relaxation réceptive
  3. réflexe recto-anal inhibiteur: évaluation (intrinsèque)
  4. réflexe recto-anal excitateur: continence (moelle, acquis)
35
Q

What is defecation and how does it work?

A

Conscious decision to release fecal matter when socially acceptable

how?

  • relaxation of puborectal muscles
  • relaxation of internal and external sphincters
  • contraction of rectum
  • valsalva stays voluntary —> PUSH

MD1 GI - EXAM 1 (15 decks)

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