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Digestivo > Motility > Flashcards

Motility Flashcards

1
Q

Layers GI tract

A

Serosa
Muscularis externa: circular, longitudinal
Submucosa: muscularis mucosae
Mucosa
Mucosal glands

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2
Q

Innervation GI tract

A

S fibers = postganglionic
PS fibers = preganglionic
Afferent fibers

Myenteric plexus (Auerbach)
Submucosal plexus (Meissner)

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3
Q

Myenteric plexus location

A

Between circular and longitudinal layers of muscularis externa (interconnected by fibers that convey the AP)

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4
Q

Myenteric plexus modulators

A

Mechanoreceptors through ANS

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5
Q

Behavior of GI smooth muscle cells

A

Spike depolarization
Plateau depolarization
Slow waves - at rest

Depolarization: Ca influx // Hyperpolarization: K efflux

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6
Q

Causes of depolarization

A

Mechanic distension
Ach
Hormones

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7
Q

Causes for hyperpolarization

A

NA
A+NA

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8
Q

Patterns of contraction

A

Slow waves —> rhythmic contractions (rest)
Tonic contractions —> sustained, non rhythmic, segmental

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9
Q

S vs PS innervation

A

S inhibits peristalsis —> A, NA
PS stimulates peristalsis —> Ach

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10
Q

Functions myenteric and submucosal plexus

A

Myenteric p: motility
Submucosal p: activates gland secretion + vasoconstr / dilation of vessels

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11
Q

Effects myenteric plexus

A

Excitation (Ach) in muscularis externa
Relaxation (VIP) os sphincters and iliocecal valve

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12
Q

Effects submucosal plexus

A

(Local, region-specific effect)

Contraction submucosal plexus
Local secretion and absorption

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13
Q

Types of movement

A

Mixing contractions (segmentation)
Propulsive contractions

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14
Q

Mixing contraction (segmentation)

A

(Also propulsive but less effective)

Mix and spread the chyme —> increase absorption
Segmentation = subchymes
Alternative contractions = chymes are mixed

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15
Q

Propulsive contractions

A

Mediated by PS nerves in myenteric plexus
Upstream contraction and down stream relaxation
Displace the chyme (prox tube rapidly, distal tube slower)

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16
Q

Oral phase

A

Chewing / mastication
Homogenization (chemical and mechanical)
Taste-sensory inputs

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17
Q

Muscles of the oral phase and innervation

A

Jaw elevators
- temporal
- masseter

Jaw depressors
- lat and med pterygoideus
- digastric
- mylohyoid
- geniohyoid

Innervation: V3 (mandibular nerve)

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18
Q

Chemical homogenization occurs due to

A

Salivary glands —> amylase
- sublingual and submaxilary glands (VII CN)
- parotid gland (IX CN)

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19
Q

Mechanical homogenization occurs due to

A

Intrinsic lingual muscles (XII CN)
- sup longitudinal
- vertical
- transverse
- inf longitudinal

Extrinsic lingual muscles
- Genioglossus
- Hyoglossus
- Styloglossus
- Geniohyoid

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20
Q

Touch innervation (tongue)

A

Post 1⁄3 → IX CN
Ant 2⁄3 → branch of the mandibular nerve V3 (Lingual nerve)

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21
Q

Taste innervation (tongue)

A

Beginning of the pharynx → X CN, vagal branch (int laryngeal n)
Post 1⁄3 → IX CN
Ant 2⁄3 → branch from VII CN (Chorda tympani)

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22
Q

Pharyngeal phase

A

Movement of the bolus oropharynx —> esophagus.
Involuntary

3 functions:
1. Coordination of the passage of the bolus.
2. Preventing food from entering the nasopharynx
3. Preventing food from entering the lungs

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23
Q

Pharyngeal phase I: events

A

Elevation of the uvula
Elevation of the palate
Tension of the palate

Result: nasopharynx is sealed off

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24
Q

Pharyngeal phase I: muscles

A

Palate elevator (Levator veli palatini)
Tensor veli palatini.

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25
Q

Pharyngeal phase I: innervation

A

Sensory fibers: IX CN —> senses food presence = reflex starts

Motor fibers: X, V3 CN —> stimulates muscles

26
Q

Pharyngeal phase II: events

A

Elevation pharynx + larynx
(due to muscles longitudinal layer)

27
Q

Pharyngeal phase II: muscles

A

Constrictors/outer circular muscles (X CN)
- Superior constrictor
- Middle constrictor
- Inferior constrictor

Elevators/inner longitudinal layer:
- Stylopharyngeus (IX CN)
- Salpingopharyngeus (X CN)
- Palatopharyngeus (X CN)

28
Q

Pharyngeal phase III: events

A

Adduction of the vocal cords
Deglutition apnea
Epiglottis closure
Elevation and anteversion of the larynx

29
Q

Pharyngeal phase IV: events

A

Pharyngeal peristalsis: propulsion of the bolus
Relaxation of the upper esophageal sphincter

30
Q

Pharyngeal phase IV: muscles

A

Outer circular muscles: superior, middle and inferior pharyngeal constrictors (pharyngeal peristalsis)

31
Q

Esophageal phase

A

Bolus is forced inferiorly from pharynx —> esophagus

32
Q

Esophageal phase I: EVENTS

A

Primary esophageal peristalsis
Secondary esophageal peristalsis

33
Q

Primary esophageal peristalsis: muscles

A

Striated muscle in upper thirds (IX and X CN)
Smooth muscle in inferior third (myenteric plexus, X CN)

34
Q

Primary esophageal peristalsis: innervation

A

CNS is required for activation of primary peristalsis, BUT peristalsis can also occur independently from it

There is central but also peripheral neurogenic control.

35
Q

Secondary esophageal peristalsis: definition

A

If the bolus cannot be moved through primary esophageal peristalsis.

Activated through the firing of local mechanoreceptor (distension —> bolus)

36
Q

Secondary esophageal peristalsis: events

A

Above the bolus level: circular layer contraction, longitudinal layer relaxation

Below the bolus level: circular layer relaxation, longitudinal layer contraction

37
Q

Secondary esophageal peristalsis: neurotransmitters

A

Relaxation: VIP (vasoactive intestinal polypeptide) + NO
Activators: Ach and substance P.

38
Q

Esophageal phase II: events

A

Relaxation + opening of lower esophageal sphincter (cardias)

39
Q

Esophageal phase II: important structures

A

Costal diaphragm
Phreno-esophageal membrane

(Closure of cardias: physiological sphincter)

40
Q

Gastric motility: innervation

A

PS: hypothalamus - dorsal vagal nucleus - X CN
S: greater splanchnic nerves - synapse in celiac ganglion

PS stimuli: touch and taste (tongue), smell, sight of food,…
S stimuli: stress, fight-flight response

41
Q

Stomach functions

A

Storage

Mixing of food with gastric secretions
- Propulsion
- Grinding
- Retropulsion

Emptying

42
Q

Functions of each stomach portion

A

Oral portion (fundus) -> receives the bolus, storage and some digestion.
Caudal portion (body and antrum) -> digestion + propulsion.

43
Q

Mixing vs propulsion waves

A

Mixing waves = slow waves. From body to antrum

Propulsion waves = spikes. From antrum to pylorus

44
Q

Vagal reflex

A
  1. Bolus = distension of stomach walls -> mechanoreceptors Myenteric plexus -> info to CNS
  2. PS reflex through X CN -> slow waves, segmentation movement → mixing
  3. Antrum: propulsion waves (spike) push the chyme from antrum to pylorus = closed -> allows + mixing and chyme formation
  4. Relaxation in the pylorus (X CN) = chyme continue its way (depends on hormones)
45
Q

Gastric emptying - stimulus

A

Gastric factors:
- Gastric food volume.
-↑ gastrin secretion (by G cells in antrum)

46
Q

Effects of gastric factors

A

Pyloric sphincter relaxation
- Pyloric pump activation
- Secretion of gastric acidic juices (HCl) (by stomach gastric glands)

47
Q

Inhibition of gastric emptying

A

Duodenal factors (too much chyme -> regulate pyloric function to protect itself)
- Duodenal distension
- Toxic components
- Chyme acidity
- Osmolarity
- Protein/fat rich chyme

48
Q

Mechanism of gastric emptying

A

Entero-gastic reflexes:
- Myenteric plexus
- S nervous system (extrinsic nerves)
- Inhibitory reflex of the vagus
- Hormonal mechanisms
- CCK (jejunum)in response to fat rich chyme
- Secretin (duodenal mucosa) in response to acid
- Gastric inhibitory peptide (GIP) in response to fat & carbohyd rich chyme

49
Q

Effects inhibition of entero-gastric reflexes

A

Increase tone (contraction) of the pyloric sphincter
Inhibit pyloric pump (therefore inhibit emptying)

50
Q

Neuro-hormonal mechanism of entero-gastric axis (tabla)

A
51
Q

Cells that protect gastric mucosa

A

Principal/Mucus cells —> bicarbonate mucus
Parietal cells —> chloridric acid
Endocrine cells

52
Q

Protection mechanism of the gastric mucosa

A

Bicarbonate mixes with the protons of the acid content of the stomach and becomes water, neutralizing and protecting the lining.

53
Q

Motility small intestine

A

Segmentation movements
Propulsion
Migrating motor complex
Ileocecal valve

54
Q

Segmentation movements of the small intestine

A

Mixing of the chyme with bile, pancreatic and intestinal fluids
Increases the absorption surface
Antrograde and retrograde movements

55
Q

Propulsion in small intestine

A

Only anterograde

Stimulated by the PS nerves (stretching and irritants)
Inhibited by S nerves (fight-flight response)

56
Q

Migrating motor complex

A

During fasting
Cleans the remaining food, dead cells, bacteria,…
Slow waves induced by motilin (endocrine cells in intest crypts)

57
Q

Iliocecal valve (motility of the small intestine)

A

Always closed.
Opened by the presence of Gastrin -> gastroileal reflex -> activates the ileocecal reflex

58
Q

Motility of large intestine

A

Austrae contractions
Peristalsis de Masa

59
Q

Austrae contractions

A

Stimulus = stretching / distension
Segmentation movements by tinae coli when there is food.
Ascendent and transverse colon
Increases the absorption surface

60
Q

Peristalsis de Masa

A

Stimulated by stretching + irritants and gastro-colic reflex
Small propulsion movements, continuous and directed towards the rectum.
Transverse and descending colon
During and after meals
Increase the absorption surface

61
Q

Defecation reflex

A

Stimulus = distension of the sigmoid colon + rectum.

Pathway:
Distension of the rectum -> sensory neurons through pelvic splanchnic nerves -> dorsal horn of the spinal cord - reflex -> efferent fibres of these same S2-S4 PS nerves
from the ventrolateral horn -> propulsion (contractions)

Conscious relaxation:
- External muscles of the sphincter at the anus
- Regular, voluntary motor neurons (ventral horn)

Digestivo (4 decks)

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