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D1 Spring - Physiology Exam 6 > 4/22: Overview, Saliva, Mastication, and Swallowing > Flashcards

4/22: Overview, Saliva, Mastication, and Swallowing Flashcards

1
Q

What are the two components of the digestive system?

A
  1. Alimentary canal (GI tract)
  2. Accessory organs
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2
Q

What is the alimentary canal?

A
  • Mouth to anus
  • lumen contents considered outside body
  • 30 feet in length
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3
Q

What are the accessory organs?

A
  • not part of GI tract
  • produce substances secreted into tract
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4
Q

What substances are secreted into the tract by the accessory organs?

A
  • salivary glands
  • exocrine pancreas
  • liver and gall bladder
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5
Q

What are the 6 functions of the GI system?

A
  1. Digestion
  2. Secretion
  3. Absorption
  4. Motility
  5. Excretion
  6. Defense
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6
Q

What is digestion?

A

Breakdown ingested molecules into building blocks

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7
Q

What are the two types of digestion?

A
  1. Mechanical
  2. Chemical
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8
Q

What things are secreted in the GI tract?

A

Digestive enzymes
Acid/base
Bile

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9
Q

What are processes that assist with absorption in the GI tract?

A

Passive and active transport processes

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10
Q

What is the function of absorption?

A

Moves substances from lumen of gut to blood

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11
Q

What is the function of motility in the GI tract?

A
  • mixing
  • mechanical digestion
  • move material through tract (propulsion)
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12
Q

What is the function of excretion in the GI system?

A
  • removal of metabolic waste
  • very little true waste in feces (bile pigments)
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13
Q

What is the function of defense in the GI system?

A

Gut associated lymphoid tissue

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14
Q

What are ingested nutrients?

A

Carbohydrates
Fats
Proteins
DNA, RNA
Water
Electrolytes
Vitamins

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15
Q

What are other ingested substances into the GI tract?

A

Pathogens
Alcohol
Drugs (Licit, illicit)
Toxins
Coins, toys, bugs

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16
Q

What are the 4 layers of the GI tract wall?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa
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17
Q

Describe the mucosa of the GI tract

A
  • simple columnar epithelium
  • lamina propria
  • muscularis mucosa (movement of villi)
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18
Q

Describe the submucosa of the GI tract

A
  • CT layer
  • blood and lymph vessels
  • submucosal plexus
    (network of neurons, projections to luminal surface cells, muscularis mucosa, and to myenteric pelxus)
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19
Q

Describe the muscularis externa of the GI tract

A
  • Circular muscle
  • Longitudinal muscle
  • myenteric plexus
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20
Q

Describe the serosa of the GI tract wall

A
  • CT covering
  • support GI tract in abdominal cavity
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21
Q

What kind of NS does the GI tract have?

A

Enteric NS = submucosal and myenteric pelxus
- little brain

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22
Q

Describe the epithelial layer of the GI tract

A

➢ Simple Columnar (microvilli)
➢ Goblet Cells
➢ Enteroendocrine cells (base of villi)
➢ Stem cells

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23
Q

What is the tremendous surface area available used for?

A

absorption of materials from lumen

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24
Q

What is used for surface area absorption?

A
  1. Circular folds
  2. Villi
  3. Microvilli (brush border)
    - increases SA 600x over flat surface
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25
Q

What is found in the inside villus of the GI tract?

A
  • lacteals (lymph vessels)
  • capillary network
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26
Q

What is the function of the circular muscle?

A

Contraction narrows lumen

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27
Q

What is the function of the longitudinal muscle?

A

Contraction shortens tube

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28
Q

What is the myenteric plexus?

A
  • network of neurons
  • input from autonomic NS
  • projections to submucosal plexus, circular, and longitudinal muscle
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29
Q

What do control systems regulate?

A

Conditions in lumen of tract (not ECF conditions)

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30
Q

What are control mechanisms governed by?

A

Volume and composition of luminal contents

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31
Q

Where are endocrine cells located?

A

Scattered in gut mucosa

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32
Q

What are specialized cells?

A

Endocrine cells (one cell - one hormone (mostly)

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33
Q

What do cells “taste”?

A

Luminal contents

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34
Q

What are paracrine cells similar to?

A

Endocrine

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35
Q

Where are paracrine cells released into?

A

interstitial fluid, diffuses to target (may “overflow” into the circulation)

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36
Q

What are two established gut paracrine factors?

A

Histamine (ECL cell)
Somatostatin (D cell)

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37
Q

What is the sympathetic nervous system inhibitory to?

A

Digestive function

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38
Q

What fibers are in the sympathetic portion of the gut?

A

Mainly postganglionic

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39
Q

What fibers are in the parasympathetic portion of the gut?

A

Preganglionic

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40
Q

Where do the myenteric plexus neurons extend?

A

The entire length of GI tract

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41
Q

What does the myenteric plexus control?

A

Muscle of muscularis externa

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42
Q

What happens when the myenteric plexus is stimulated?

A
  1. Increase tone of gut wall
  2. Increase intensity of rhythmic contractions
  3. Slight increase in rate of rhythmic contractions
  4. Increase conduction velocity of electrical waves along gut wall
  5. Inhibition of sphincter
    contraction
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43
Q

What does the submucosal plexus control function of?

A

Each minute segment of tract

44
Q

What is the local control of the submucosal plexus?

A
  • intestinal secretions
  • absorption
  • contraction of mucosal muscle
45
Q

Describe skeletal muscle of the gut

A

Voluntary, striated

46
Q

What are organs that deal with skeletal musculature?

A

mouth, oropharynx, upper esophageal sphincter, upper 1/3 of esophagus,
external anal sphincter

47
Q

What is skeletal musculature controlled by?

A

Somatic MN – CN XII (tongue), V (chewing), IX, X
(swallowing); Pudendal n. – ext. anal sphincter

48
Q

Describe smooth muscle of the gut

A

Involuntary, unstriated

49
Q

What are organs that deal with smooth musculature?

A

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

50
Q

What is smooth gut muscle controlled by?

A

Autonomic NS

51
Q

Describe the sympathetic control of smooth muscle

A

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

52
Q

Describe the parasympathetic control of smooth muscle

A

(vagus, pelvic) - pre-ganglionic fibers (ACh) act
locally, postganglionic fibers are part or ENS

53
Q

What are the actions of the parasympathetic smooth muscle of the gut?

A

actions are stimulatory or inhibitory, depending on final neurotransmitter released

54
Q

What is smooth gut musculature controlled by?

A

Endocrine and paracrine factors

55
Q

What are examples of patterns of motility?

A
  • Chewing
  • Swallowing
  • Esophageal transport
  • Gastric storage, trituration, emptying
  • Vomiting
  • Gallbladder storage, emptying
  • Small intestinal mixing & transport
  • Colonic storage, defecation
56
Q

What is the importance of the portal vein?

A

Collects all venous outflow from most GI organs

57
Q

Where does all portal outflow go to?

A

Liver before entering vena cava

58
Q

What is “scanned” by liver?

A

Nutrients, hormones, drugs, and toxins

59
Q

What are the two types of saliva?

A
  1. Serous
  2. Mucous
60
Q

Describe serous saliva

A

Watery secretion containing ptyalin (α amylase)

61
Q

What does serous saliva do?

A

Moisten and dissolve food
Small amount of chemical digestion

62
Q

Describe mucous saliva

A

Thick secretions containing mucin

63
Q

What is the function of mucous saliva?

A

Lubrication and protection of surfaces

64
Q

What are the type of salivary glands?

A
  1. Parotid - Serous Gland
  2. Submandibular - Mixed
  3. Sublingual - Mixed
  4. Many tiny buccal glands - Mucus
65
Q

What are the components of saliva?

A

Water
Bicarbonate
Mucins
Amylase
Lysozyme, lactoferrin, IgA
Epidermal and nerve growth factors

66
Q

What is the function of water?

A

Facilitates taste and dissolution of nutrients, aids in swallowing

67
Q

What is the function of bicarbonate?

A

Neutralizes refluxed gastric acid

68
Q

What is the function of mucins?

A

Lubrications

69
Q

What is the function of amylase?

A

Starch digestion

70
Q

What is the function of lysozyme, lactoferrin, and IgA?

A

Innate and acquired immunity

71
Q

What is the function of epidermal and nerve growth factors?

A

Mucosal growth and protection

72
Q

What do acinar cells form?

A

Unit called an acinus with a small central lumen

73
Q

What do acinar cells secrete?

A

isosmotic serous saliva (chloride, bicarbonate and potassium ions (Na+ and water follow passively,
enzymes)

74
Q

What do mucous cells secrete?

A

Mucous

75
Q

What do myoepithelial cells do?

A

Contract to move saliva into and through ducts

76
Q

What do intercalated duct cells move?

A

Saliva out of acini

77
Q

What do intercalated duct cells prevent?

A

Backflow of saliva into acini

78
Q

What do striated ducts (interlobular) contain?

A

Tight junctions

79
Q

What do striated ducts (interlobular) cells modify?

A

Saliva (Na+ and Cl reabsorbed; K+ and HCO3- secreted)

80
Q

What is the predominate regulator of saliva production?

A

Parasympathetic NS

81
Q

What receptors work with the parasympathetic NS?

A

Ach/Muscarinic receptors

82
Q

What is parasympathetic NS control of saliva critical for?

A
  • Critical for initiation of saliva secretion
  • Critical for sustaining high levels of saliva secretion
83
Q

What happens as flow rate increases?

A
  • Less time for ductal modification
  • Saliva more closely resembles the plasma
  • Becomes more basic
84
Q

What is reflex activation of parasympathetic which stimulates saliva production?

A
  • Taste (especially sour) and tactile stimuli (presence of smooth objects) on tongue
    surface
  • Smell of food (especially if it is a food that is not liked)
  • Ingestion of irritating foods
  • Nausea
85
Q

What is the role of sympathetic NS (NE/adrenergic receptors) for saliva secretion?

A

Minor role
Potentiates parsympathetic effects

86
Q

What glands is unstimulated salivation produced by?

A

69% submandibular glands
26% parotid glands
5% sublingual glands

87
Q

What is unstimulated salivation inhibited by?

A
  1. Fear
  2. Sleep
  3. Fatigue
  4. Dehydration
88
Q

What glands are stimulated salivation produced by?

A

69% Parotid
26% submandibular
5% sublingual

89
Q

What is stimulated salivation stimulated by?

A
  1. Autonomic (primarily
    parasympathetic)
  2. Thinking/seeing/smelli
    ng food
  3. Conditioned salivation
  4. Chewing
  5. Nausea
90
Q

What are rates of saliva production not dependent on?

A

age, flow rates remain constant in spite of acinar degeneration

91
Q

What is xerostomia?

A

Feeling of dry mouth

92
Q

What are causes of xerostomia?

A
  • Polypharmacy (>4 drugs/day)
  • Anxiety and depression (and medications used for
    treatment)
  • Insufficient hydration
  • Radiation to the head and neck
  • Sjogren syndrome
93
Q

What is sjogren’s syndrome?

A
  • Autoimmune destruction of mucous membranes and
    moisture-secreting glands
  • Decreased production of tears and saliva
  • Dry eyes and mouth
94
Q

What can xerostomia cause?

A

➢ Increased caries due to reduced oral clearance of sugars, dietary acids, oral
bacteria
➢ Halitosis
➢ Disrupted sleep due to dry mouth; wake up to sip water and moisten mouth
➢ Difficulty lubricating and swallowing food
➢ Dry mouth (feel thirsty, dry, cracked lips)
– Burning mouth sensation
– Dry/sore oral mucosa
➢ Impaired sense of tastes
➢ Heartburn
– Low saliva; decreased buffering
– Loss of protective growth factors in saliva
– Lengthened healing time for ulcers

95
Q

What is management for xerostomia?

A
  • Avoid acidic, spicy,
    crunchy and coarse
    foods.
  • Alcohol-free toothpastes
    and rinses.
  • Oral moisturizers, sips of
    water, sugarless chewing
    gum.
  • Sialogogues such as
    pilocarpine and
    cevimeline before meals
    (cholinergic agonists)
96
Q

What is mastication?

A

Rhythmic opening and closing of mandible that is coordinated with
tongue movements

97
Q

What are functions of mastication?

A
  1. Prepare food bolus for swallowing
  2. Initiate digestive and metabolic activities
98
Q

Describe mechanical digestion

A

Reduce particle size
- Break up cells
- Break up indigestible cellulose
- Increase surface area/decrease particle size for mixing with digestive
enzymes

99
Q

Describe the mix of food with saliva

A

(serous and mucous)
- Chemical digestion (mainly carbohydrates)
- Sufficient plasticity
- Surface lubrication
- Cohesive structure

100
Q

Describe the initiation of digestive and metabolic activities

A
  • Digestion of carbohydrates in mouth
  • Initiate reflexes to prepare digestive tract for incoming food
101
Q

What are the three stages of deglutition?

A
  1. Voluntary stage
  2. Pharyngeal stage
  3. Esophogeal stage
102
Q

Describe the voluntary stage of deglutition

A
  • Initiate swallowing reflex
  • Bolus of food moved into
    pharynx by tongue
  • Stimulates epithelial
    swallowing receptor area
103
Q

Describe the pharyngeal stage of deglutition

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 (Respiration inhibited for < 2 sec.)
  • Upper Esophageal Sphincter (UES; Pharyngoesophageal Sphincter) relaxes
104
Q

Describe the esophageal stage of deglutition

A
  • Coordinated muscle contractions to move bolus through esophagus into
    stomach (aborally).
  • ≈ 10 sec
105
Q
A

D1 Spring - Physiology Exam 6 (6 decks)

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