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I've got kidney disease > Lecture 26 > Flashcards

Lecture 26 Flashcards

1
Q

What are the functions of chewing?

A
  • mechanical digestion - ingestion
  • mixing food with saliva - tasting
  • stimulus for cephalic phase
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2
Q

How is swallowing controlled?

A
  • voluntarily (via skeletal muscle)
  • through the involuntary reflex (via the brainstem - this is initiated by having a food bolus in your mouth, the stimulation of taste centres make the rhythm and the strength is due to the consistency of the bolus)
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3
Q

What is swallowing?

A

This is the rapid transfer of food from the mouth to the stomach

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4
Q

Swallowing converts the mouth and pharynx pathway from what to what?

A

From a gas transfer function to a food transfer function

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5
Q

Swallowing prevents what?

A

Reflux

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6
Q

What are three things that happen in the process of swallowing?

A
  • oral events
  • initiation of the swallowing reflex
  • a cascade of sequential events in the pharynx and the oesophagus
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7
Q

What are the oral events that occur in the process of swallowing?

A
  • initiation by stretch receptors
  • soft palate
  • epiglottis
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8
Q

What happens in the soft palate during swallowing?

A

It is pushed upward which prevents the food from entering the nasal passage

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9
Q

What happens to the epiglottis during swallowing?

A

It moves down to cover the entrance to the trachea. This is to stop food going into the trachea but also to stop acid from getting into the trachea

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10
Q

What happens when there initiation by stretch receptors?

A

Food is forced into the pharynx by the tongue. This activates stretch receptors to trigger the brainstem which will generate a response.

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11
Q

What are the three oesophageal events that occur during swallowing?

A
  • the upper oesophageal sphincter
  • the lower oesophageal sphinter
  • oeosophagus
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12
Q

What happens to the upper oesophageal sphincter during swallowing?

A

it relaxes (opens) which allows the food to enter the oesophagus

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13
Q

What happens to the lower oesophageal sphincter during swallowing?

A

It opens (relaxes) at the start of swallowing. Food enters the stomach and the sphincter closes after the peristalsis wave

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14
Q

What happens to the oesophagus during swallowing?

A

The smooth muscle contracts and the peristaltic wave pushes the food towards the stomach. This lasts about 9 seconds.

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15
Q

There is peristalsis starting in the skeletal muscle of the oesophagus and then this transitions into the smooth muscle. True or false?

A

true

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16
Q

What stays open foe the entire duration of the peristaltic wave down the oesophagus?

A

the lower oesophageal sphincter

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17
Q

Do we have voluntary or involuntary control of swallowing? Explain this.
How are they coordinated?

A

both
The swallowing and the oral events are voluntary and this sets up a whole lots of cascade events that are involuntary
They are coordinated with the swallowing centre in the brainstem in response to this stretch.

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18
Q

Does swallowing involve skeletal or smooth muscle?
Describe this
What are they controlled by?

A

both
All of the pharyngeal muscles are skeletal muscles and are controlled directly by the swallowing centre. The upper part of the oesophagus is also skeletal muscle and this is also controlled directly by the swallowing centre. There is a specific transition zone to smooth muscle and this is controlled by the ENS which is modulated by the swallowing centre

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19
Q

Arrival of food in the oesophagus initiates what?

A

A primary peristaltic wave which sweeps food down the oesophagus towards the stomach.

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20
Q

If the food is not cleared from the oesophagus by the primary peristaltic wave, what happens?

A

There is feedback to the swallowing centre so there is a secondary peristaltic wave. This is repeated until all the food is cleared.

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21
Q

What two events occur at the same time as the initiation of swallowing?

A
  • relaxation of the lower oesophageal sphincter

- relaxation of the proximal stomach

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22
Q

Why is important that there is relaxation of the lower oesophageal sphincter at the same time as the initiation of swallowing?

A

To allow the passage of food into the stomach

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23
Q

Why is important that there is relaxation of the lower proximal stomach at the same time as the initiation of swallowing?

A

This is receptive relaxation which reduces the stomach pressure below the oesophageal pressure so that the food goes into the stomach. It also limits gastric reflux

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24
Q

At the initiation of swallowing, what opens?

A

The upper oesophageal sphincter

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25
Q

What happens at the same time as the upper oesophageal sphincter is open?

A

The lower oesophageal sphincter relaxes and depressurises

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26
Q

The stomach starts relaxing at the start of the swallow and its tone remains relaxed until well after the lower oesophageal sphincter is shut. There is a little increase in pressure to keep the pressure in the oesophagus higher than in the stomach. After this, the stomach regains some tone. True or false?

A

True

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27
Q

What is the purpose of receptive relaxation in the act of swallowing?

A

It decreases pressure in the stomach below the oesophageal pressure when the sphincters are open in order to prevent reflux.

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28
Q

What is heartburn?

A

This is reflux of acid chyme into the oesophagus which causes irritation to the oesophageal mucosa

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29
Q

What are 5 causes of heartburn?
• Abnormal relaxation of __________ esophageal sphincter
• Lack of _______ ________ or gastric __________ in the _________
• Conditions that increase _______ pressure
• Excessive gastric ________
• Infection with ________. ________

A
  • Abnormal relaxation of lower esophageal sphincter
  • Lack of Receptive Relaxation or gastric accommodation in the stomach
  • Conditions that increase gastric pressure
  • Excessive gastric secretion
  • Infection with H. pylori
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30
Q

What are 4 treatments of heartburn?

A 
• Antacids (neutralize gastric HCl)
• Antihistamines & proton pump inhibitors
(stop HCl production)
• Lifestyle modifications (E.g. diet)
 • Surgery (depends on cause)
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31
Q

What role for the upper oesophageal sphincter play in the anti-reflux role?

A

it is an additional barrier to reflux
it only opens for a shirt time at the start of the swallowing process so if the lower process fails, the chyme is not going t be getting into the pharynx or respiratory tract

32
Q

What role does the lower oesophageal sphincter have to prevent reflux?

A

When you are not swallowing, it is a high pressure zone so the pressure is actively maintained higher in the oesophagus and lower in the stomach.

33
Q

What role does the lower oesophageal sphincter have to prevent reflux?

A

When you are not swallowing, it is a high pressure zone so the pressure is actively maintained higher in the oesophagus and lower in the stomach.

34
Q

What role does the stomach have to prevent reflux?

A

There are storage functions that maintain pressure as the volume increases eg.

  • receptive relaxation (reduction of gastric tone with swallowing)
  • gastric accommodation (reflex relaxation of proximal stomach with gastric distension)
35
Q

What are the three main types of gastric motility?

A
  • storage
  • retropulsion
  • controlled delivery to the duodenum
36
Q

What is the purpose of the storage gastric motility pattern?

A

this is to allow food entry during swallowing (the accommodating increases the volume during a meal)

37
Q

What is the purpose of the retropulsion gastric motility?

A

This combines peristaltic contraction (pushing food forward) and pyloric sphincter contraction (pushes food back) for a mixing function

38
Q

What is the purpose of the controlled delivery to the duodenum gastric motility pattern?

A

This is changing the contraction and relaxation of the pyloric sphincter. It is initially closed which allows mixing to occur. There is then short period of opening which allows entry of food to match the capacity (volume and secretion rate)

39
Q

What are the three regions of the stomach called? What parts make up each of these regions?

A
  • proximal stomach: fundus, proximal body and the site of storage
  • transitional area: mid body
  • distal stomach: distal body and pylorus
40
Q

What is the purpose of the distal stomach?

A

movement, mechanical breakdown, controlled release to the small intestine

41
Q

What is the cardia?

A

This is the most proximal part of the stomach - it is where the chyme first enters the stomach

42
Q

What happens in the proximal stomach?

A

This is an area where there is active modulation of muscle tone both when swallowing and not so that you maintain the pressure gradient for food to enter

43
Q

What does storage in the stomach allow for?

A

to accommodate food without changes in pressure

44
Q

What is receptive relaxation?

A

Reduction of gastric tone with swallowing

45
Q

What is gastric accommodation? How does this happen?

A

The stomach distends with more and more chyme.
Through short local reflexes, the receptors in the ENS will feedback to the ENS and then the smooth muscle will relax.
This also occurs through a long reflex - the ENS is communicating with afferent branches of the autonomic nervous system (CNS) than back to the ENS through the autonomic nervous system to generate a response. This is the vago/vagal reflex as the autonomic nerves run through the vagus nerve.

46
Q

Peristalsis occurs in the stomach and is coordinated with what to do what?

A

the pyloric sphincter to do retropulsion for mechanical breakdown of the chyme.

47
Q

Describe the phasic peristaltic contractions in the stomach

A

This begins 5-10 mins before the arrival of food. They spread from the greater curvature towards the pylorus.
From 0-60 mins there is gentle ripples and then from 60-300 mins there is increased intensity

48
Q

How is the peristalsis in the stomach regulated/controlled?

A

The duration and intensity depends on the consistency and composition of food:

  • particulate vs homogenised food
  • fat content
  • it is related to gastric emptying (there is information from the stomach and feedback from the small intestine)
49
Q

Describe the process of retropulsion in the stomach

A

• Initiated 5-10 mins after gastric distension
• Happens when the pyloric sphincter contracts at
the same time as peristaltic contractions occur
• Results in a backwards (retrograde) flow of content
toward the fundus

50
Q

What is the function of retropulsion?

A

• Mixes gastric contents with secretions to produce chyme
• Mechanically reduce size of food particles
- rebounding wave of retropulsion
- sieve effect of pyloric sphincter

51
Q

How is retropulsion in the stomach regulated/controlled?

A

This is during the gastric phase - the chemical and stretch receptors initiate a response in the stomach contents

52
Q

What are the three phases of gastric motility?

A
  • cephalic stage
  • gastric phase
  • intestinal phase
53
Q

Describe the cephalic phase

A

This prepares the stomach for the arrival of food

54
Q

During the cephalic phase, in response to the presence of food in the mouth, chewing or swallowing, the CNS does what three things?

A
  • inhibits muscles in the body of the stomach by modulating the ENS (through receptive relaxation and accommodation)
  • there is low level stimulation of antral contractions by modulation of the ENS
  • the pyloric sphincter is kept mainly closed
55
Q

Describe the low level stimulation of antral contraction by modulation of the ENS during the cephalic phase

A

This activates muscular contractions in preparation for food. You slowly start ramping up the amplitude of contractions by making sure they are over the threshold for a longer period of time with each signal from the ICoC. It also stimulates the release of gastrin from the G cells which has an important role in the regulation of the gastric secretion

56
Q

Why is the pyloric sphincter mainly closed during the cephalic phase?

A

because it prevents the release of material to the intestines

57
Q

What is the gastric phase mediated by? Give examples

A

Receptors in the stomach wall such as mechanoreceptors responding to the distention of the stomach wall by food and chemoreceptors response to presence of products of digestion (eg. amino acids and peptides)

58
Q

During the gastric phase, what do the mechanoreceptors and the chemoreceptors stimulate?

A
  • intrinsic reflexes involving the ENS

- extrinsic reflexes such as the vago/vagal reflexes which can mediate the activity of the ENS

59
Q

During the gastric phase, what do the reflexes do?

A

They inhibit the tone in the proximal stomach to accommodate food (gastric accommodation) and stimulate contraction in distal stomach through the release of ACh and substance P and the stimulation of G cells to release gastrin. The pyloric sphincter remains closed

60
Q

During the gastric phase, what is different about the activity f the proximal and distal parts of the stomach?

A
  • proximal: there is gastric accomodation

- distal: there is an increase in peristalsis for retropulsion (via ACh)

61
Q

What happens during the intestinal phase?

A

There is controlled delivery of food from the stomach to the duodenum and the duodenum controls gastric emptying to match capacity

62
Q

Why is it important that there is controlled delivery of food from the stomach to the duodenum during the intestinal phase?

A

This ensures that the food s processed correctly in the stomach and it matches the delivery of the food to the small intestine with its ability to handle the food

63
Q

What is meant by the fact that during the intestinal phase, the intestine matches delivery of food to the small intestine to its ability to handle the food?

A

The physical properties of the food would change so if you want to increase of decrease the release of chyme according to the physical properties so that the duodenal enzymes and bicarbonate can process it

64
Q

During the intestinal phase, the pyloric sphincter is open more during which wave?

A

The peristaltic wave (depending on the rate of release)

65
Q

What is inhibited during the intestinal phase?

A

duodenal contractions

66
Q

What effects the rate of gastric emptying?

A
  • the size of the meal (larger is faster, due to the stretching of the stomach wall)
  • composition of the meal (higher energy is slower, liquid meals is faster, isosmotic is faster than the hyperosmotic or hypo-osmotic)
67
Q

Why is an isosmotic meal emptied faster than a hyperosmotic or hypo-osmotic meal?

A

Because you don’t need as many secretions to alter the osmolarity so the enzymes in the small intestine can still work

68
Q

What happens during the intestinal phase?

A

Stretch, acid, osmolarity, nutrients is detected by receptors in the small intestine. The receptors can activate the ENS which can activate the CNS or directly activate the smooth muscle cells. The peristalsis in the stomach will be slowed down or sped up depending on whether you want faster or slower release. The hormones such as secretin, CCK and GIP tend to slow down release and so you get adrenaline and NO that decrease the motility of the stomach. But you can get signals such as ACh to increase peristalsis if you want to increase the release to the duodenum. If you want to slow down release to the duodenum, you need to decrease smooth muscle and increase the contraction of the sphincter.

69
Q

What is the purpose of the duodenum?

A

This delivers digestive enzymes from the pancreas and neutralises the acid to make food safe for the intestinal epithelia, allowing for contact digestion and absorption

70
Q

Why is initially the delivery to the duodenum limited?

A

it ensures effective gastric digestion
the initial delivery was slow so that all the receptors can judge what there is and send feedback from the stomach. As the duodenum gets information, he has enteroendocrine cell, which give feedback mechanisms so more chyme release

71
Q

At the start of the intestinal phase, the chyme moves from the stomach to match the capacity of duodenum. Describe this

A

Tonic proximal stomach contraction
Phasic distal stomach contraction
Controlled inhibition of the pyloric sphincter
(periodically lets chyme through)

72
Q

Describe segmentation in the small intestine

A

• Most common fed (postprandial) motility pattern
• Circular muscle contraction in segments
• Aids digestion by mixing secretions
• Aids contact digestion and absorption by exposing
contents to small intestinal epithelial layer

73
Q

Describe peristalsis in the small intestine

A

• Infrequent
• Ascending circular muscle contraction
• Descending circular muscle relaxation
• Longitudinal muscle shortening (contraction)
• Absorption at more distal sites
• Transfer of waste to large intestine
Magnitude of contractions regulated by ENS reflexes (with input from CNS). Frequency of contraction determined by the interstitial cells of Cajal (not regulated)

74
Q

Describe the storage in the large intestine

A
  • large intestinal transit is slow (24-48 hrs)
  • This inactivity enhances water absorption
  • Segmentation (Mixing) occurs during storage
  • Short duration contractions – circular muscle
  • Turnover of contents aids absorption
75
Q

Describe peristalsis in the large intestine

A
  • high intensity contractions

* propel contents into rectum

76
Q

Describe the elimination (defecation) in the large intestine

A

• Relaxation of internal anal sphincter – smooth muscle.
• The rectoanal inhibitory reflex prevents spontaneous opening of
external anal sphincter.
• External anal sphincter is under conscious control - skeletal
muscle – relaxes when defecation is appropriate.
• Valsalva maneuver – closing the airway while exhaling to increase force of elimination

I've got kidney disease (43 decks)

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