Physiology of mastication, swallowing & GI tract motility Flashcards Preview

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Flashcards in Physiology of mastication, swallowing & GI tract motility Deck (70):
1

What is the Digestion tract?

Series of Organs running from Mouth to Anus (Oral to Aboral)

2

How is the digestive tract separated?

By the use of Sphincters

3

What is the function of the Mouth and Oropharynx?

Chop food, lubricate it, start carbohydrate and fat digestion, propel food to oesophagus

4

What is the function of the Oesophagus?

Transportation of food to the stomach

5

What is the function of the stomach?

-Stores food temporarily.
- Continues with digestion
-Initiates protein digestion
- Delivery of Chyme to the small intestine

6

What is the function of the small intestine?

Principal site of absorption of nutrients

7

What is the function of the Large intestine?

- Reabsorb fluids and electrolytes
- Stores faecal matter before regulated expulsion

8

What are the accessory structures of the Digestive tract?

- Salivary glands
- Pancreas
- Liver and Gall bladder (Hepatobiliary system)

9

What are the parts of the small intestine?

Duodenum
Jejunum
Ileum

10

What part of the pancreas is used in the digestive system?

Exocrine Pancreas

11

What sphincter prevents reflux?

The lower Oesophageal sphincter

12

What are the basic digestive processes?

Motility
Secretion
Digestion
Absorption

13

What is motility?

This is the mechanical activity that involves smooth muscle. This includes:
Propulsive movement
Mixing Movements
Tonic contractions

14

What parts of digestive system bring about motility throughout the digestive tract?

Mouth
Pharynx
Upper Oesophagus
External anal sphincter

15

What causes secretion form the accessory structures for digestion?

Hormonal or Neural signals

16

What do digestive secretions contain?

Water
Electrolytes
Organic compounds (enzymes, bile, mucus)

17

What is digestion?

The breakdown of biochemical foodstuffs from large indigestible units into smaller soluble units

18

How are Carbohydrates broken down?

Carbohydrates are broken down into Monosaccharides by Amylases and Disaccharidases

19

How are proteins broken down?

Proteins are broken down into amino acids, dipeptides and tripeptides by Proteases and Dipeptidases

20

How are fats broken down?

Fats are converted into Monoglycerides and three fatty acids by Lipases

21

What is Absorption?

The Transfers of absorbable products of digestion from the digestive tract to the blood or lymph

22

What are the layers of the digestive tract wall?

Innermost: Mucosa
Submucosa
Muscularis Externa
Serosa

23

What is contained in the mucosa layer of the digestive tract wall?

Epithelial Cells
Exocrine cells
Endocrine cells
Lamina Propria
Muscularis mucosa

24

What is contained in the submucsoa layer?

• connective tissue
• larger blood and lymph vessels
• nerve network – submucous plexus

25

What is the serosa?

The series is the outermost layer of the digestive tract wall. It is fibrous in nature and secrets secretes serous fluid which allows organs to move against each other.

26

How is Gastrointestinal motility achieved?

Activity of smooth muscle

27

What does the circular muscle contraction do to the lumen of the digestive tract?

Lumen becomes narrower and longer

28

What does contraction of the longitudinal muscle cause to the lumen of the digestive tract?

Lumen becomes shorter and fatter

29

What allows the spread of electrical activity in the GI tract?

Gap junctions

30

What do the Gap junctions allow do for the signal?

Allows spread of electrical current to all cells and allows them to work as a syncytium

31

Describe the electrical activity in the stomach, small intestine and large intestines?

Spontaneous electrical activity that occurs as slow slaves

32

What shape are gap junctions?

They are spindle and allows cells to be attached to all of their neighbours

33

What produces the slow waves in the digestive tract?

Interstitial cells of Cajal - These are pacemarker cells

34

Describe contraction in terms of electrical current the digestive tract?

Contraction can only occur if the slow wave amplitude is sufficient to trigger the action potential

35

What is the upstroke of the action potential mediated by in the digestive tract?

Mediated by voltage-activated Ca 2+ channels

36

What is the downstroke of the action potential mediated by

Mediated by K+ voltage activated channels

37

How is the force of contraction determined in terms of action potentials for the digestive tract?

Force is related to the number of action potential/ the length of burst of the discharged that are above the threshold.

38

Where are the Interstitial cells of Cajal located?

Located in the Longitudinal and circular muscle of the submucosa

39

How many contractions/ slowness does the stomach have per minute?

3 slow waves per minute

40

How many contractions/ slowness does the small intestine have per minute?

1-12 per minute
8 in the terminal ileum

41

Describe the difference in slow waves in the part of the small intestine?

The slow waves are less in the distal small intestine than the proximal intestine. This means there is a net movement forwards in the small intestine

42

Describe the difference in slow waves in the parts of the large intestine?

The slow waves are less in the distal large intestine than the proximal intestine. This means there is a net movement backwards in the large intestine

43

What is the number of slow waves of the large intestine per minute?

8 waves per minute

44

Where are the cell bodies of the enteric nervous system located?

The cell bodies are located within the Myenteric Plexus and the Submucous Plexus

45

How are the ganglia in the enteric nervous system in the intestine connected?

Connected by the interganglionic fibre tracts

46

Describe the overall regulation of the go tracts nervous system?

It is auto regulated through the enteric nervous system. However there is extrinsic modifying factors from the central nervous system and hormones

47

What is the parasympathetic innervation for the digestive tract?

Vagal nerves and sacral nerves. This is a vagalsacral outflow

48

What are the effects of the parasympathetic system on the GI tract?

Increased secretions, Increased blood flow and smooth muscle contraction

Causes relaxation of some sphincters

49

What is the sympathetic innervation of the GI tract

Thoraco-lumbar outflow

50

Where does the sympathetic system synapse to the ganglia?

In the pervertebral ganglia:
Celiac
Super messenteric
Inferior messenteric

51

What is the effect of the sympathetic system on the GI tract?

Decreased motility, secretion and blood flow.

52

Describe the pathway for a nerve reflex

Sensory neruone to Interneurone to Effector neurone

53

What is an example of a local reflex?

Peristalsis

54

What is an example of a short reflex?

Intestino-Intestinal Inhibitory Reflex

55

What is an example of a long reflex?

Gastroileal relfex

56

What is Peristalsis?

A wave of contraction that normally proceeds along the gut in an aboral direction

57

Describe the mechanism of Peristalsis?

Muscle contractions behind the bolus of food. Longitudinal muscle relaxes and release of VIP and NO from the inhibitory motor-neurone. The circular muscle contracts and releases ACh and substance from excitatory motor-neurone.

Muscle relaxes infant of the bolus of food. Longitudinal muscle contracts due to release of ACh and substance P. The circular muscle relaxes due to release of VIP and NO

58

What is segmentation?

This is mixing or churning movements, rhythmic contractions of circular muscle layer that mix and divide luminal contents.

59

Where are tonic contractions found and what are they?

Tonic contractions are found in the sphincters of the GI - they are sustained contractions.

60

What is the function of the Upper oesophageal sphincter?

Relaxes to allow swallowing. It closes during inspiration

61

What is the function of the Lower oesophageal sphincter?

Relaxes to permit entry of food to the stomach and closes to prevent reflux of the gastric contents

62

What is the function of the pyloric sphincter?

Regulated gastric emptying and usually prevents duodenal gastric reflux

63

What is the function f the Ileocecal sphincter?

Regulates the flow from the ileum to the colon

64

What are the 6 sphincters of the GI tract?

Upper Oesophageal sphincter
Lower Oesophageal sphincter
Pyloric sphincter
Ileocecal sphincter
Internal sphincter
External sphincter

65

What are the parts of the mouth?

Lips
Teeth
Palate
Uvula
Tongue
Pharynx

66

What is the medical term for swallowing?

Deglutition

67

What are the two phases of deglutition?

Oropharyngeal stage
Oesophageal stage

68

Describe the stages of the oropharyngeal stage of deglutition?

Bolus formed in the mouth
Tongue forces bolus into pharynx
Pressure stimulates pharyngeal pressure receptors
Afferent impulse to the swallowing centre in the medulla
Efferent initiate an all or nothing response - signal may fire or not fire
Upper oesophageal sphincter opens
Good passes through pharynx into the oesophagus

69

What happens to the larynx and the vocal cords during swallowing?

The larynx is elevated and the vocal cords close across the larynx

70

Describe the oesophageal stage of deglutition

Circular fibres behind bolus squeeze bolus down towards stomach

Longitudinal fibres in front of bolus shorten distance of travel

Lower oesophageal sphincter opens within 2-3 s of the initiation of a swallow (closes after passage of bolus to prevent reflux)