GI I - Overview Saliva, Mastication, and Swallowing Flashcards
1
Q
where is the alimentary canal located
A
mouth to anus
2
Q
what are the lumen contents in the alimentary canal considered
A
outside of body
3
Q
how long is the alimentary canal
A
30 feet
4
Q
what do accessory organs in the digestive system do
A
-produce substances secreted into tract
-not considered part of GI tract
5
Q
what are the accessory organs of the GI tract
A
-salivary glands
-exocrine pancreas
-liver and gall bladder
6
Q
what are the 6 functions of the GI system
A
-digestion
-secretion
-absortption
-motility
-excretion
-defense
7
Q
describe the function of digestion of the GI tract
A
breakdown ingested molecules into building blocks
8
Q
what are the two types of digestion
A
mechanical and chemical
9
Q
what does the GI system secrete
A
-digestive enzymes
-acids/bases
-bile
10
Q
describe absorption in the GI system
A
- passive and active processes
-moves substances from lumen of gut to blood
11
Q
describe motility in the GI system
A
-mixing
-mechanical digestion
-move material through tract
12
Q
describe excretion of the GI tract
A
-removal of metabolic waste
-very little true waste in feces except bile pigments
13
Q
what is the defense function of the GI tract
A
gut associated lymphoid tissue
14
Q
what are the 4 layers of the GI tract wall from innermost to outermost
A
-mucosa
- submucosa
- muscularis externa
- serosa
15
Q
describe what the mucosa layer contains
A
-simple columnar epithelium
-lamina propria
- muscularis mucosa
16
Q
what does the muscularis mucosa do
A
movement of villi
17
Q
describe the submucosal layer
A
-CT layer
- blood and lymph vessels
- submucosal plexus
18
Q
what is the submucosal plexus
A
- network of neurons
-projections to luminal surface cells, muscularis mucosa, and to myenteric plexus
19
Q
what does the muscularis externa contain
A
-circular muscle
- longtiudinal muscle
- myenteric plexus
20
Q
what does contraction of the circular muscle in the muscularis externado
A
contraction narrows lumen
21
Q
what does contraction of the longitudinal muscle in the muscularis externa do
A
contraction shortens tube
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
23
Q
describe the serosa layer
A
-CT covering
- support GI tract in abdominal cavity
24
Q
what makes up the enteric nervous system
A
the submucosal plexus and myenteric plexus
25
what does the epithelial layer consist of
-simple columnar with microvilli
- goblet cells
-enteroendocrine cells
-stem cells
26
what structures increase surface area in the epithelium
-circular folds
-villi
- microvilli- brush border
27
what are inside the villi
-lacteals (lymph vessels)
- capillary network
28
how much do the structures in the epithelial layer increase the SA
600x over flat surface
29
what are the modes of communication utilized by the GI system
-endocrine
-paracrine
-neurocrine
-immune/juxtacrine
30
what are examples of immune/juxtacrine cells
ECL cells and D cells
31
what do control systems regulate in the GI tract
conditions of the lumen NOT the ECF conditions
32
what are control mechanisms governed by
volume and composition of luminal contents
33
what does afferent (sensory) innervation respond to
stretch, inflammation, nutrients, endocrine factors
34
where are afferent synapses located
in enteric nervous system, prevertebral ganglia, spinal cord and brainstem
35
what nerve is mainly afferent to brainstem
vagus
36
what are the innervations of efferent signals (secretomotor)
-somatic
- sympathetic
- parasympathetic
37
what nerves do somatic efferent
CN 12 (tongue) , 5 (chewing), and 10 (swallowing, and pudendal nerve
38
describe sympathetic efferent function, the NT, and the effect
post ganglionic fibers (NE) to enteric nervous system, vasculature, ducts, parenchyma
-inhibitory
39
describe parasympathetic efferent function, nerves used, and effect
-ENS functions as post ganglionic fibers
- vagus, pelvic nerves
-actions are stimulatory or inhibitory depending on final NT receptor
40
describe the fiber types of sympathetic and parasympathetic neurons in the ENS
-sympathetic: postganglionic
- parasympathetic: preganglionic
41
what NT do preganglionic neurons in the PNS use? postganglionic?
pre: AcH
post: ACh, amines, NO, peptides
42
what does the myenteric plexus control and what does it do when stimulated
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
what does the submucosal plexus control and what does it do when stimulated
- controls function of each segment of tract
- intestinal secretions
- absorption
-contraction of mucosal muscle
44
where are endocrine cells located
scattered in gut mucosa
45
what are endocrine cells
specialized cells that mostly secrete one hormone and are localized to specific regions of the gut
46
what do paracrine factors do
- released into ISF, diffuses to target
47
what are the 2 gut paracrine factors
- histamine (ECL cell)
- somatostatin (D cell)
48
what is histamine released by
gastrin
49
what is somatostatin released by
luminal H+
50
what are the patterns of motility
-chewing
-swallowing
-esophageal transport
- gastric storage, trituration, emptying
- vomiting
- gallbladder storage, emptying
- small intestine mixing and transport
- colon storage, defecation
51
describe the skeletal gut musculature and where its located in the GI tract
- voluntary, striated
- mouth, oropharynx, upper esophageal sphincter, upper 1/3 of esophagus, external anal sphincter
52
where is smooth muscle located in the GI tract
- lower 2/3 of esophagus, stomach, small intestine, large intestine, gallbladder, biliary and pancreatic ducts
53
what does the portal vein do
- collects all venous outflow from most GI organs
54
where does portal outflow go and why
to liver before entering vena cava to scan for nutrients, hormones, drugs and toxins
55
what are the types of saliva
serous and mucus
56
describe serous saliva and its function
- watery secretion containing ptyalin (alpha amylase)
-moisten and dissolve food
- small amount of chemical digestion
57
describe mucus saliva and its function
-thick secretions containing mucin
- lubrication and protection of surfaces
58
what are the salivary glands and the type of saliva it secretes
- parotid: serous
- submandibular: mixed
- sublingual: mixed
- many tiny buccal glands: mucus
59
what are the components of saliva and function of each
- 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
how much saliva is produced a day
up to 1.5 L
61
what controls saliva secretion
neural reflex control
62
what are the structures in salivary glands
- intercalated ducts
- striated ducts
- acinar cells
- mucous cells
- myoepithelial cells
63
what do intercalated duct cells do
- move saliva out of acini
- prevent backflow of saliva into acini
64
what do striated ducts (interlobular) do and what are they made of
- columnar epithelial cells
-tight junctions
- modify saliva: Na+ and Cl- reabsorbed; K+ and HCO3- secreted
65
describe acinar cells and their function
- pyramidal in shape
- form an acinus with a small central lumen
- secrete serous saliva
66
describe mucous cells and their function
- columnar in shape
- organized into tubules
-secrete mucus
67
describe myoepithelial cells and their function
- around the serous acini
- contract to move saliva into and through the ducts
68
describe the role of the PNS in the control of saliva secretion
- 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
what are the stimuli for PNS stimulated saliva production
- 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
what is the role of the sympathetic nervous system in control of saliva secretion
-minor role
-enhances parasympathetic effects
71
as saliva flow rate increases:
- less time for ductal modification
-saliva more closely resembles the plasma
- becomes more basic
72
what glands are responsible for unstimulated saliva production and what percentage of each
- 69% submandibular glands
- 26% parotid glands
- 5% sublingual glands
73
what glands are responsible for stimulated saliva production and what percentage of each
- 69% parotid
- 26% submandibular
- 5% sublingual
74
what is saliva production inhibited by
-fear
-sleep
-fatigue
- dehydration
75
what is saliva production stimulated by
-autonomic
- thinking/seeing/ smelling food
- conditioned salivation
- chewing
- nausea
76
rates of saliva production are not dependent on ____, flow rate remain constant in spite of ____.
age; acinar degeneration
77
what is xerostomia
subjective feeling of a dry mouth
78
what are the most common causes of xerostomia
-polypharmacy ( more than 4 drugs)
- anxiety and depression (and meds used for tx)
- insufficient hydration
- radiation to head and neck
- sjogren syndrome
79
what happens in sjogren syndrome
- autoimmune destruction of mucous membranes and moisture secreting glands
- decreased production of tears and saliva
- dry eyes and mouth
80
what are the effects of xerostomia
- increased caries
- halitosis
- disrupted sleep
- difficulty lubricating and swallowing food
- dry mouth
- burning mouth
-dry/sore oral mucosa
- impaired sense of tastes
- heartburn
81
how does xerostomia cause heart burn
- low saliva; decreased buffering
- loss of protective growth factors in saliva
- lengthened healing time for ulcers
82
how is xerostomia managed
- 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
what is mastication
- rhythmic opening and closing of mandible that is coordinated with tongue movements
84
what are the functions of mastication
- prepare food bolus for swallowing
- initiate digestive and metabolic activities
85
how is the food bolus prepared for swallowing
- mechanical digestion
- mix food with saliva
86
what does mechanical digestion do
- break up cells
- break up indigestible cellulose
- increase surface area/ decrease particle size for mixing with digestive enzymes
87
what does mixing food with saliva do
- chemical digestion
- sufficient plasticity
- surface lubrication
- cohesive structure
88
how does mastication initiate digestive and metabolic activities
- digestion of carbohydrates in the mouth
- initiate reflexes to prepare digestive tract for incoming food
89
what are the 3 stages of deglutition (swallowing)
-voluntary stage
- pharyngeal stage
-esophageal stage
90
what happens during the voluntary stage of swallowing
- initiate swallowing reflex
- bolus of food moved into pharynx by tongue
- stimulates epithelial swallowing receptor area
91
what happens during the pharyngeal stage of swallowing
-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
what happens during the esophageal stage of swallowing and how long does it last
-coordinated muscle contractions to move bolus through esophagus into stomach
- 10 sec
93
what does aborally mean
away from mouth
- AKA caudad
94
what are the two types of peristalsis and define each
- 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
what are the functions of sphincters and peristalsis
- transport of solids and liquids from pharynx to stomach
- prevents air intake from UES
- prevents reflux from LES
96
what is the swallowing center in the brain stem
DVC
97
what is primary peristalsis defined as
-wave of relaxation in front of bolus
- wave of contraction behind bolus
98
what is the function of secondary peristalsis
-clearing a bolus that was not wholly expelled by primary wave
- removing any gastric contents that reflux back into the lower esophagus
99
describe the state of the upper and lower esophageal sphincters between swallows
closed and both are tonic
100
when does the UES relax
during swallow
101
when does the LES relax
as peristaltic wave approaches
102
what is GERD and what is it treated by
- reflux of gastric contents into esophagus
- common and potentially disabiling
-treated by inhibiting gastric acid secretion
