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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
Where are proteins absorbed?
by specific receptors for 99% of ingested proteins
26
Where are lipids digested?
**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
Where are lipids absorbed?
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
Overview of digestion and absorption:
29
Where are vitamins absorbed?
**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
How is vit. B12 metabolized?
31
Where are minerals absorbed?
**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
What is the job of the colon?
**NO ENZYMES** Absorbs water (sodium pump) Secretes mucus for lubrification
33
How does the colon move things?
**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
What is the main function of the rectum?
**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
What is defecation and how does it work?
**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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