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Physiology > GI I - Overview Saliva, Mastication, and Swallowing > Flashcards

GI I - Overview Saliva, Mastication, and Swallowing Flashcards

1
Q

where is the alimentary canal located

A

mouth to anus

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2
Q

what are the lumen contents in the alimentary canal considered

A

outside of body

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3
Q

how long is the alimentary canal

A

30 feet

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4
Q

what do accessory organs in the digestive system do

A

-produce substances secreted into tract
-not considered part of GI tract

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5
Q

what are the accessory organs of the GI tract

A

-salivary glands
-exocrine pancreas
-liver and gall bladder

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6
Q

what are the 6 functions of the GI system

A

-digestion
-secretion
-absortption
-motility
-excretion
-defense

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7
Q

describe the function of digestion of the GI tract

A

breakdown ingested molecules into building blocks

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8
Q

what are the two types of digestion

A

mechanical and chemical

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9
Q

what does the GI system secrete

A

-digestive enzymes
-acids/bases
-bile

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10
Q

describe absorption in the GI system

A
  • passive and active processes
    -moves substances from lumen of gut to blood
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11
Q

describe motility in the GI system

A

-mixing
-mechanical digestion
-move material through tract

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12
Q

describe excretion of the GI tract

A

-removal of metabolic waste
-very little true waste in feces except bile pigments

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13
Q

what is the defense function of the GI tract

A

gut associated lymphoid tissue

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14
Q

what are the 4 layers of the GI tract wall from innermost to outermost

A

-mucosa
- submucosa
- muscularis externa
- serosa

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15
Q

describe what the mucosa layer contains

A

-simple columnar epithelium
-lamina propria
- muscularis mucosa

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16
Q

what does the muscularis mucosa do

A

movement of villi

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17
Q

describe the submucosal layer

A

-CT layer
- blood and lymph vessels
- submucosal plexus

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18
Q

what is the submucosal plexus

A
  • network of neurons
    -projections to luminal surface cells, muscularis mucosa, and to myenteric plexus
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19
Q

what does the muscularis externa contain

A

-circular muscle
- longtiudinal muscle
- myenteric plexus

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20
Q

what does contraction of the circular muscle in the muscularis externado

A

contraction narrows lumen

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21
Q

what does contraction of the longitudinal muscle in the muscularis externa do

A

contraction shortens tube

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22
Q

what is the myenteric plexus

A

-network of neurons extending entire length of GI tract
- input from autonomic NS
- projections to submucosal plexus, circular, and longitudinal muscle

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23
Q

describe the serosa layer

A

-CT covering
- support GI tract in abdominal cavity

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24
Q

what makes up the enteric nervous system

A

the submucosal plexus and myenteric plexus

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25
Q

what does the epithelial layer consist of

A

-simple columnar with microvilli
- goblet cells
-enteroendocrine cells
-stem cells

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26
Q

what structures increase surface area in the epithelium

A

-circular folds
-villi
- microvilli- brush border

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27
Q

what are inside the villi

A

-lacteals (lymph vessels)
- capillary network

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28
Q

how much do the structures in the epithelial layer increase the SA

A

600x over flat surface

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29
Q

what are the modes of communication utilized by the GI system

A

-endocrine
-paracrine
-neurocrine
-immune/juxtacrine

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30
Q

what are examples of immune/juxtacrine cells

A

ECL cells and D cells

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31
Q

what do control systems regulate in the GI tract

A

conditions of the lumen NOT the ECF conditions

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32
Q

what are control mechanisms governed by

A

volume and composition of luminal contents

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33
Q

what does afferent (sensory) innervation respond to

A

stretch, inflammation, nutrients, endocrine factors

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34
Q

where are afferent synapses located

A

in enteric nervous system, prevertebral ganglia, spinal cord and brainstem

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35
Q

what nerve is mainly afferent to brainstem

A

vagus

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36
Q

what are the innervations of efferent signals (secretomotor)

A

-somatic
- sympathetic
- parasympathetic

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37
Q

what nerves do somatic efferent

A

CN 12 (tongue) , 5 (chewing), and 10 (swallowing, and pudendal nerve

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38
Q

describe sympathetic efferent function, the NT, and the effect

A

post ganglionic fibers (NE) to enteric nervous system, vasculature, ducts, parenchyma
-inhibitory

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39
Q

describe parasympathetic efferent function, nerves used, and effect

A

-ENS functions as post ganglionic fibers
- vagus, pelvic nerves
-actions are stimulatory or inhibitory depending on final NT receptor

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40
Q

describe the fiber types of sympathetic and parasympathetic neurons in the ENS

A

-sympathetic: postganglionic
- parasympathetic: preganglionic

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41
Q

what NT do preganglionic neurons in the PNS use? postganglionic?

A

pre: AcH
post: ACh, amines, NO, peptides

42
Q

what does the myenteric plexus control and what does it do when stimulated

A

controls muscularis externa
- increases tone of gut wall
- increase intensity of rhythmic contractions
-slight increase in rate of rhythmic contractions
- increase conduction velocity of electrical waves along gut wall
- inhibition of sphincter contraction

43
Q

what does the submucosal plexus control and what does it do when stimulated

A
  • controls function of each segment of tract
  • intestinal secretions
  • absorption
    -contraction of mucosal muscle
44
Q

where are endocrine cells located

A

scattered in gut mucosa

45
Q

what are endocrine cells

A

specialized cells that mostly secrete one hormone and are localized to specific regions of the gut

46
Q

what do paracrine factors do

A
  • released into ISF, diffuses to target
47
Q

what are the 2 gut paracrine factors

A
  • histamine (ECL cell)
  • somatostatin (D cell)
48
Q

what is histamine released by

A

gastrin

49
Q

what is somatostatin released by

A

luminal H+

50
Q

what are the patterns of motility

A

-chewing
-swallowing
-esophageal transport
- gastric storage, trituration, emptying
- vomiting
- gallbladder storage, emptying
- small intestine mixing and transport
- colon storage, defecation

51
Q

describe the skeletal gut musculature and where its located in the GI tract

A
  • voluntary, striated
  • mouth, oropharynx, upper esophageal sphincter, upper 1/3 of esophagus, external anal sphincter
52
Q

where is smooth muscle located in the GI tract

A
  • lower 2/3 of esophagus, stomach, small intestine, large intestine, gallbladder, biliary and pancreatic ducts
53
Q

what does the portal vein do

A
  • collects all venous outflow from most GI organs
54
Q

where does portal outflow go and why

A

to liver before entering vena cava to scan for nutrients, hormones, drugs and toxins

55
Q

what are the types of saliva

A

serous and mucus

56
Q

describe serous saliva and its function

A
  • watery secretion containing ptyalin (alpha amylase)
    -moisten and dissolve food
  • small amount of chemical digestion
57
Q

describe mucus saliva and its function

A

-thick secretions containing mucin
- lubrication and protection of surfaces

58
Q

what are the salivary glands and the type of saliva it secretes

A
  • parotid: serous
  • submandibular: mixed
  • sublingual: mixed
  • many tiny buccal glands: mucus
59
Q

what are the components of saliva and function of each

A
  • water: taste and dissolution of nutrients, aids in swallowing
  • bicarbonate: neutralizes refluxed gastric acid
  • mucins: lubrication
  • amylase: starch digestion
  • lysozyme, lactoferrin, IgA: innate and acquired immunity
  • epidermal and nerve growth factors
60
Q

how much saliva is produced a day

A

up to 1.5 L

61
Q

what controls saliva secretion

A

neural reflex control

62
Q

what are the structures in salivary glands

A
  • intercalated ducts
  • striated ducts
  • acinar cells
  • mucous cells
  • myoepithelial cells
63
Q

what do intercalated duct cells do

A
  • move saliva out of acini
  • prevent backflow of saliva into acini
64
Q

what do striated ducts (interlobular) do and what are they made of

A
  • columnar epithelial cells
    -tight junctions
  • modify saliva: Na+ and Cl- reabsorbed; K+ and HCO3- secreted
65
Q

describe acinar cells and their function

A
  • pyramidal in shape
  • form an acinus with a small central lumen
  • secrete serous saliva
66
Q

describe mucous cells and their function

A
  • columnar in shape
  • organized into tubules
    -secrete mucus
67
Q

describe myoepithelial cells and their function

A
  • around the serous acini
  • contract to move saliva into and through the ducts
68
Q

describe the role of the PNS in the control of saliva secretion

A
  • main regulator of saliva production
  • critical for initiation of saliva secretion
  • critical for sustaining high levels of saliva secretion
  • vasodilation of blood vessels supplying salivary glands
  • causes up to 20x increase in saliva production by acinar cells
69
Q

what are the stimuli for PNS stimulated saliva production

A
  • taste (especially sour) and tactile stimuli (presence of smooth objects) on tongue surface
  • smell of food (especially if it is not liked)
  • ingestion of irritating foods
    -nausea
70
Q

what is the role of the sympathetic nervous system in control of saliva secretion

A

-minor role
-enhances parasympathetic effects

71
Q

as saliva flow rate increases:

A
  • less time for ductal modification
    -saliva more closely resembles the plasma
  • becomes more basic
72
Q

what glands are responsible for unstimulated saliva production and what percentage of each

A
  • 69% submandibular glands
  • 26% parotid glands
  • 5% sublingual glands
73
Q

what glands are responsible for stimulated saliva production and what percentage of each

A
  • 69% parotid
  • 26% submandibular
  • 5% sublingual
74
Q

what is saliva production inhibited by

A

-fear
-sleep
-fatigue
- dehydration

75
Q

what is saliva production stimulated by

A

-autonomic
- thinking/seeing/ smelling food
- conditioned salivation
- chewing
- nausea

76
Q

rates of saliva production are not dependent on ____, flow rate remain constant in spite of ____.

A

age; acinar degeneration

77
Q

what is xerostomia

A

subjective feeling of a dry mouth

78
Q

what are the most common causes of xerostomia

A

-polypharmacy ( more than 4 drugs)
- anxiety and depression (and meds used for tx)
- insufficient hydration
- radiation to head and neck
- sjogren syndrome

79
Q

what happens in sjogren syndrome

A
  • autoimmune destruction of mucous membranes and moisture secreting glands
  • decreased production of tears and saliva
  • dry eyes and mouth
80
Q

what are the effects of xerostomia

A
  • increased caries
  • halitosis
  • disrupted sleep
  • difficulty lubricating and swallowing food
  • dry mouth
  • burning mouth
    -dry/sore oral mucosa
  • impaired sense of tastes
  • heartburn
81
Q

how does xerostomia cause heart burn

A
  • low saliva; decreased buffering
  • loss of protective growth factors in saliva
  • lengthened healing time for ulcers
82
Q

how is xerostomia managed

A
  • avoid acidic, spicy, crunchy and coarse foods
  • alcohol free toothpastes and rinses
  • oral moisturizers, sips of water and sugarless chewing gum
  • sialogogues such as pilocarpine and cevimeline before meals (cholinergic agonists)
83
Q

what is mastication

A
  • rhythmic opening and closing of mandible that is coordinated with tongue movements
84
Q

what are the functions of mastication

A
  • prepare food bolus for swallowing
  • initiate digestive and metabolic activities
85
Q

how is the food bolus prepared for swallowing

A
  • mechanical digestion
  • mix food with saliva
86
Q

what does mechanical digestion do

A
  • break up cells
  • break up indigestible cellulose
  • increase surface area/ decrease particle size for mixing with digestive enzymes
87
Q

what does mixing food with saliva do

A
  • chemical digestion
  • sufficient plasticity
  • surface lubrication
  • cohesive structure
88
Q

how does mastication initiate digestive and metabolic activities

A
  • digestion of carbohydrates in the mouth
  • initiate reflexes to prepare digestive tract for incoming food
89
Q

what are the 3 stages of deglutition (swallowing)

A

-voluntary stage
- pharyngeal stage
-esophageal stage

90
Q

what happens during the voluntary stage of swallowing

A
  • initiate swallowing reflex
  • bolus of food moved into pharynx by tongue
  • stimulates epithelial swallowing receptor area
91
Q

what happens during the pharyngeal stage of swallowing

A

-involuntary reflex- mediated by contraction of skeletal muscles
- mediated by swallowing center in brainstem
- soft palate pulled upward and closes off nasopharynx
- epiglottis closes off trachea and respiration is inhibited for 2 sec
- UES relaxes

92
Q

what happens during the esophageal stage of swallowing and how long does it last

A

-coordinated muscle contractions to move bolus through esophagus into stomach
- 10 sec

93
Q

what does aborally mean

A

away from mouth
- AKA caudad

94
Q

what are the two types of peristalsis and define each

A
  • primary: continuation of peristaltic wave initiated during pharyngeal phase of swallowing (8-10 sec)
  • secondary: activated by esophageal distension from retained food in esophagus or low pH
95
Q

what are the functions of sphincters and peristalsis

A
  • transport of solids and liquids from pharynx to stomach
  • prevents air intake from UES
  • prevents reflux from LES
96
Q

what is the swallowing center in the brain stem

A

DVC

97
Q

what is primary peristalsis defined as

A

-wave of relaxation in front of bolus
- wave of contraction behind bolus

98
Q

what is the function of secondary peristalsis

A

-clearing a bolus that was not wholly expelled by primary wave
- removing any gastric contents that reflux back into the lower esophagus

99
Q

describe the state of the upper and lower esophageal sphincters between swallows

A

closed and both are tonic

100
Q

when does the UES relax

A

during swallow

101
Q

when does the LES relax

A

as peristaltic wave approaches

102
Q

what is GERD and what is it treated by

A
  • reflux of gastric contents into esophagus
  • common and potentially disabiling
    -treated by inhibiting gastric acid secretion

Physiology (41 decks)

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