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Digestivo > Motility > Flashcards

Motility Flashcards

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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
Pharyngeal phase I: innervation
Sensory fibers: IX CN —> senses food presence = reflex starts Motor fibers: X, V3 CN —> stimulates muscles
26
Pharyngeal phase II: events
Elevation pharynx + larynx (due to muscles longitudinal layer)
27
Pharyngeal phase II: muscles
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
Pharyngeal phase III: events
Adduction of the vocal cords Deglutition apnea Epiglottis closure Elevation and anteversion of the larynx
29
Pharyngeal phase IV: events
Pharyngeal peristalsis: propulsion of the bolus Relaxation of the upper esophageal sphincter
30
Pharyngeal phase IV: muscles
Outer circular muscles: superior, middle and inferior pharyngeal constrictors (pharyngeal peristalsis)
31
Esophageal phase
Bolus is forced inferiorly from pharynx —> esophagus
32
Esophageal phase I: EVENTS
Primary esophageal peristalsis Secondary esophageal peristalsis
33
Primary esophageal peristalsis: muscles
Striated muscle in upper thirds (IX and X CN) Smooth muscle in inferior third (myenteric plexus, X CN)
34
Primary esophageal peristalsis: innervation
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
Secondary esophageal peristalsis: definition
If the bolus cannot be moved through primary esophageal peristalsis. Activated through the firing of local mechanoreceptor (distension —> bolus)
36
Secondary esophageal peristalsis: events
Above the bolus level: circular layer contraction, longitudinal layer relaxation Below the bolus level: circular layer relaxation, longitudinal layer contraction
37
Secondary esophageal peristalsis: neurotransmitters
Relaxation: VIP (vasoactive intestinal polypeptide) + NO Activators: Ach and substance P.
38
Esophageal phase II: events
Relaxation + opening of lower esophageal sphincter (cardias)
39
Esophageal phase II: important structures
Costal diaphragm Phreno-esophageal membrane (Closure of cardias: physiological sphincter)
40
Gastric motility: innervation
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
Stomach functions
Storage Mixing of food with gastric secretions - Propulsion - Grinding - Retropulsion Emptying
42
Functions of each stomach portion
Oral portion (fundus) -> receives the bolus, storage and some digestion. Caudal portion (body and antrum) -> digestion + propulsion.
43
Mixing vs propulsion waves
Mixing waves = slow waves. From body to antrum Propulsion waves = spikes. From antrum to pylorus
44
Vagal reflex
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
Gastric emptying - stimulus
Gastric factors: - Gastric food volume. -↑ gastrin secretion (by G cells in antrum)
46
Effects of gastric factors
Pyloric sphincter relaxation - Pyloric pump activation - Secretion of gastric acidic juices (HCl) (by stomach gastric glands)
47
Inhibition of gastric emptying
Duodenal factors (too much chyme -> regulate pyloric function to protect itself) - Duodenal distension - Toxic components - Chyme acidity - Osmolarity - Protein/fat rich chyme
48
Mechanism of gastric emptying
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
Effects inhibition of entero-gastric reflexes
Increase tone (contraction) of the pyloric sphincter Inhibit pyloric pump (therefore inhibit emptying)
50
Neuro-hormonal mechanism of entero-gastric axis (tabla)
51
Cells that protect gastric mucosa
Principal/Mucus cells —> bicarbonate mucus Parietal cells —> chloridric acid Endocrine cells
52
Protection mechanism of the gastric mucosa
Bicarbonate mixes with the protons of the acid content of the stomach and becomes water, neutralizing and protecting the lining.
53
Motility small intestine
Segmentation movements Propulsion Migrating motor complex Ileocecal valve
54
Segmentation movements of the small intestine
Mixing of the chyme with bile, pancreatic and intestinal fluids Increases the absorption surface Antrograde and retrograde movements
55
Propulsion in small intestine
Only anterograde Stimulated by the PS nerves (stretching and irritants) Inhibited by S nerves (fight-flight response)
56
Migrating motor complex
During fasting Cleans the remaining food, dead cells, bacteria,... Slow waves induced by motilin (endocrine cells in intest crypts)
57
Iliocecal valve (motility of the small intestine)
Always closed. Opened by the presence of Gastrin -> gastroileal reflex -> activates the ileocecal reflex
58
Motility of large intestine
Austrae contractions Peristalsis de Masa
59
Austrae contractions
Stimulus = stretching / distension Segmentation movements by tinae coli when there is food. Ascendent and transverse colon Increases the absorption surface
60
Peristalsis de Masa
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
Defecation reflex
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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