Case 11 SBA Flashcards
(149 cards)
1
Q
What are the three paired salivary glands?
A
Parotid, submandibular, sublingual
2
Q
What percentage of saliva is secreted from the main three glands?
A
90%
3
Q
Describe the parotid glands
A
side of face by ears. Parotid duct passes through buccinator muscle and opens into the oral cavity on the inner surface of the cheek opposite the maxillary second molar. Mumps can cause swelling of this gland
4
Q
Describe the submandibular glands
A
under mandible. Submandibular duct (Wharton duct) travels between sublingual gland and genioglossus. Drains into the mouth through the sublingual caruncles located either side of the frenulum of the tongue
5
Q
Describe the sublingual glands
A
under tongue. 8-20 ducts of Rivinus drain the sublingual glands. Some form the sublingual duct of Bartholin and join the submandibular duct. Others drain into the mouth separately at the sublingual folds either side of the frenulum of the tongue
6
Q
Sialolithiasis
A
Salivary stones - calcified deposits that can block ducts causing pain and swelling of the affected gland. Can lead to inflammation and/or infection
7
Q
Who and where do salivary stones affect most?
A
Male
30-60
Submandibular gland (less common in parotid, rare in sublingual and other smaller glands)
8
Q
Treatments for sialolithiasis
A
hydration and stimulation of secretion to flush out smaller stones
massage to encourage stone expulsion
sialendoscopy
surgical removal of stones or gland
9
Q
Functions of saliva
A
Lubrication to facilitate mastication, swallowing, and speech
Digestion and absorption
Protection, oral and dental health
10
Q
Contents of saliva for lubrication
A
Fluid, mucus, proline-rich proteins
11
Q
Contents of saliva for digestion and absorption
A
alpha amylase - initiation of starch digestion
lingual lipase - initiation of lipid digestion
r-protein - haptocorrin, role in b12 absorption
12
Q
Contents of saliva for protection, oral and dental health
A
lysozyme breaks down bacteria walls
lactoferrin sequesters iron to stop bacterial growth and makes cell walls more permeable
slows down viral replication
IgA
thiocyanate
proline-rich proteins
mucus
fluid
HCO3-
13
Q
Why do bacteria proliferate overnight in the mouth?
A
Low rate of saliva production
14
Q
Xerostomia
A
dry mouth
15
Q
What causes salivary gland hypofunction?
A
decreased blood supply, secretory function, stimuli
Sjögren’s syndrome
Nerve damage
Drugs
16
Q
What can salivary gland hypofunction lead to?
A
dental caries, ulceration, infections, discomfort, speech difficulties, taste, chewing, swallowing
17
Q
Treatments of xerostomia
A
stimulate residual saliva, artificial saliva, and sugar free gum
18
Q
What are the secretory units in the salivary glands?
A
Acini - produce all the fluid
19
Q
Pathway from acinus to main duct in salivary glands
A
Acinus → intercalated duct → striated duct → intralobular duct → interlobular duct → lobar duct → main duct
20
Q
Histology of submandibular glands
A
acinar/serous cells and mucus secreting cells
21
Q
Histology of parotid glands
A
lots of serous/acinar cells
22
Q
Parotid saliva type and percentage secreted
A
Serous, 20-25%
23
Q
Sublingual saliva type and percentage secreted
A
Mucus/serous, <5%
24
Q
Submandibular saliva type and percentage secreted
A
Serous/mucus, 60-65%
25
Other smaller salivary glands saliva type and percentage secreted
Mucus, 10%
26
Functional unit of saliva glands and contents
Salivon
acinus, mucus cell, myoepithelial cells, serous cells
27
Phases of saliva secretion
primary secretion from acini and secondary ductular modification
28
Is saliva hypertonic, isotonic, or hypotonic compared to plasma?
Hypotonic
29
What is secreted in primary secretion of saliva?
Na, Cl, mucin glycoprotein, proline-rich protein, IgA
30
What is primary saliva secretion mainly driven by?
Na/K/2Cl transporter - the movement of chloride ions
31
How are chloride ions secreted in primary saliva secretion?
Down the concentration gradient through chloride channels that are mostly calcium controlled or ligand-gated. the opening of the channels is mostly controlled by ACh
32
What is secreted in secondary modification of saliva?
Lysozyme and potassium in intercalated duct
Potassium and HCO3 in striated and other ducts
33
What is reabsorbed in secondary modification of saliva?
Chloride and sodium ions in striated and other ducts
34
How are Na and Cl reabsorbed in secondary modification of saliva?
Na through ENaC, Cl through paracellular route
35
How does cystic fibrosis impact on saliva secretion and compositon?
CFTR involvement so cystic fibrosis would reduce the concentration of HCO3 in saliva but does not affect volume of saliva
36
Parasympathetic control of saliva production (which nerves and neurotransmitters)
CNVII (facial) controls sublingual and submandibular, CNIX (glossopharyngeal) controls parotid. Profuse secretion of watery saliva. ACh and VIP (vasoactive intestinal peptide) used.
37
Sympathetic control of saliva production
small volume of saliva rich in proteins and mucus. Norepinephrine
38
Cephalic control of saliva production
unconditioned and conditioned. Food or irritating substance in the mouth (reflex) or thought, sight, and smell of food (Pavlov)
39
Sympathetic and parasympathetic control of blood supply to salivary glands
parasympathetic vasodilation via ACh and VIP,
sympathetic vasoconstriction via norepinephrine, vasodilation via bradykinin
40
Intrinsic pacemaker in the stomach
Interstitial cells of Cajal generate a sub-threshold oscillating membrane potential (need stimuli to get contraction)
41
Gastro-gastric reflexes (antrum and reservoir)
enteric nervous system.
distention of reservoir stimulates antral contraction, distension of antrum leads to prolonged relaxation of reservoir
42
Major excitatory neurotransmitters in gastric emptying
ACh and gastrin
43
Major inhibitory neurotransmitters in gastric emptying
NO, VIP, and ATP
44
Intestinal brake mechanism
gastric emptying inhibited by stomach contents entering small intestine. controlled by release of intestinal hormones and entero-gastric reflexes.
45
Hormones involved in intestinal brake mechanism
Increased secretin from acid, increased CCK from fats, decreased gastrin from acid
46
Increase and decrease of which nervous systems leads to delayed gastric emptying?
Increased sympathetic activity and decreased parasympathetic activity leads to decreased gastric emptying. Enteric and vagus involvement.
47
Motility functions of the stomach
reservoir for ingested foodstuffs (upper stomach), initial breakdown/digestion of foodstuffs, controlled emptying of contents into intestines (lower stomach)
48
Mechanisms involved in stomach acting as a reservoir
Receptive relaxation and gastric accommodation. Both involve relaxation of fundus and proximal corpus
49
Receptive relaxation mechanism
LOS and proximal stomach relax in anticipation of contents. Vagovagal reflex.
50
Where is the vagovagal reflex and what does it control ?
afferent and efferent fibres of vagus nerve coordinate responses to gut stimuli via dorsal vagal complex in brain. Controls contraction of GI muscle layers in response to distension of the tract by food and allows for accommodation of large amounts of food in tract
51
Stages of mixing and emptying of stomach contents
Propulsion, grinding, retropulsion and then repeat
52
Stomach propulsion
peristaltic contraction propels material towards antrum and occlusion of pylorus
53
Stomach grinding
churning of trapped material in antrum, only particles <2mm can pass through
54
Retropulsion of stomach
most of the bolus is returned to gastric body to be broken down
55
Which type of meal leads to a feeling of satiety for longer and why?
Fat-rich as fatty acids trigger a strong intestinal brake response
56
Peristalsis
movement of contents along the oesophagus caused by a wave of relaxation followed by contraction of smooth muscle
57
Triggers of primary and secondary peristalsis
Primary = swallowing, secondary = presence of luminal contents
58
Voluntary swallowing reflex
voluntarily forming bolus in the mouth --> move tongue back and up --> tips bolus into the pharynx
59
Involuntary swallowing reflex
triggered by bolus exerting pressure on pharyngeal wall --> soft palate elevation --> inhibition of respiration as larynx raised and glottis closed --> upper oesophageal sphincter relaxes/opens --> oesophageal peristalsis --> lower oesophageal sphincter opens, and bolus enters stomach
60
Primary and secondary peristalsis of upper oesophagus
striated muscle so controlled by vagus nerve. excitatory ACh (nicotinic)
Primary = result of sequential activation of lower motor neurons in nucleus ambiguous
Secondary = mediated by central reflex
61
Peristalsis of lower oesophagus
smooth muscle
Primary = vagal nerves via enteric nervous system. Excitatory pathway originates in rostral dorsal motor nucleus of vagus (DMN), inhibitory in caudal DMN
Secondary = local reflex
62
Peristalsis local reflex
sensory neurons (mechanical and chemical) detect contents --> stretch receptors receive message and stretch --> firing of inhibitory motor neurons causing smooth muscle relaxation (oesophagus after area of detection) OR firing of excitatory motor neurons causing smooth muscle contraction (oesophagus before area of detection) --> stretch in next section of oesophagus and cycle repeats
63
Retching
dry heaves, chyme into oesophagus followed by immediate backflow, relaxation of distal and contraction of proximal oesophagus
64
Vomiting
forceful expulsion of GI contents, associated with contraction of intercostal muscles and increased intrathoracic pressure
65
What contracts to cause retching and vomiting?
Skeletal muscle, not the stomach
66
What is the vomiting reflex preceded by?
Retrograde peristaltic contractions originating in the jejunum
67
Vomiting reflex steps
Chyme forced from proximal small intestine into relaxed stomach through widely opened pylorus --> rhythmic respiratory movements against a closed glottis produce negative oscillations in intrathoracic pressure --> abdominal muscles and diaphragm contract, increasing intra-abdominal pressure --> contents moved out
68
Vomiting receptors in brain
Higher sensors - e.g. excessive stress
Chemical trigger zone - floor of fourth ventricle in medulla oblongata, afferent fibres that reach blood brain barrier and detect harmful substances in blood
69
What is the vomiting mechanism?
A defence mechanism
70
Labyrinthine receptors
In inner ear, play a part in motion sickness and vertigo. Vertigo can be caused by drugs and toxins which triggers vomiting
71
Vomiting receptors in GI tract
Touch in throat - stop swallowing harmful substances
Chemo in stomach - sense harmful substances
72
Vomiting receptors in GI tract
Touch in throat - stop swallowing harmful substances
Chemo in stomach - sense harmful substances
Mechano in stomach - detect abrasive substances
73
If the vomiting centre decides vomiting is the appropriate response, where does it send the signals?
Abdominal muscles, oesophageal muscles, oesophageal sphincters, and respiratory muscles.
74
Which muscles are involved in the elevation of the mandible?
temporalis, masseter, medial pterygoid
75
Which muscle is involved in retraction of the mandible?
Temporalis
76
Which nerve is responsible for taste on the anterior 2/3 of the tongue?
chorda tympani
77
What role do the ducts play in the formation of saliva?
Reabsorb electrolytes with the exclusion of water making saliva hypotonic
78
What is the role of R-protein (haptocorrin) produced by the salivary glands?
Binds to vitamin B12 protecting it from gastric acid
79
Which muscle is responsible for elevation of the soft palate?
Levator veli palatini
80
Which nerve inner ages the levator veli palatini?
Vagus
81
Innervation of soft palate muscles
All vagus except for tensor veli palatini which is trigeminal
82
Motor innervation of pharynx
vagus
83
What is achlorhydria and what can it lead to?
Reduced acid secretion
Decreased absorption of iron
84
What has both direct and indirect inhibitory effects on acid secretion by parietal cells?
Somatostatin
85
Three phases of gastric juice secretion
Cephalic, gastric, intestinal
86
What is the Cephalic gastric juice reflex?
Smell, taste, sight, thought, swallowing
87
What is the Cephalic phase of gastric juice secretion mediated by?
Vagus nerve and ACh release
88
What does the Cephalic phase of gastric juice secretion stimulate/
Insertion of primary vesicles
89
What percentage of gastric acid secretion is the Cephalic phase responsible for?
30%
90
What distends the intestines in the gastric phase of secretion?
Entry of food
91
What does distension of the intestines in the gastric phase stimulate the release of?
ACh (vago-vagal ENS)
92
What do partially digested proteins stimulate in the gastric phase?
G-cells and gastrin release
93
What inhibits the gastric phase of secretion?
Low intra-gastric pH particularly in natural regions stimulating somatostatin release from D cells
94
What percentage of gastric acid secretion is the gastric phase responsible for?
50-60%
95
What is the intestinal phase of gastric juice secretion?
Presence of amino acids and peptides in the small intestine
96
What is stimulated in the intestinal phase of gastric secretion?
Acid secretion from gastrin via G-cell stimulation
97
What inhibits the intestinal phase of gastric secretion?
Stimulation of endocrine cells to release enterogastrones
98
What percentage of gastric juice secretion is the intestinal phase responsible for?
5-10%
99
What has stimulatory direct or indirect effects on parietal cells?
Gastrin, histamine, ACh, gastrin-releasing peptide
100
Which cells produce gastrin?
G-cells
101
Which cells are responsible for histamine release in the GI tract?
Enterochromaffin (ECL)
102
What has direct or indirect inhibitory effects on the parietal cells in gastric juice secretion?
Somatostatin, cholecystokinin, secretin
103
Which cells produce somatostatin?
D cells
104
Which cells produce cholecystokinin in the GI tract?
I cells
105
Which cells produce secretin in the GI tract?
S cells
106
Describe the stimulation of the parietal cells for the control of gastric juice
ACh acts on M3 receptor which triggers insertion of tubular vesicles causing more proton pumps on the luminal surface
107
Describe the stimulation of ECL cells
ACh acts on M3 receptors which causes exocytosis of histamine vesicles. The histamine acts on H2 receptors causing more tubular vesicles to be inserted
108
Which receptor does gastrin bind to to stimulate ECL and parietal cells?
CCKb
109
Describe the inhibition of gastric juice secretion in the parietal cells
Parietal cells secrete acid. The acid inhibits G cells and has a positive effect on D cells - the somatostatin released inhibits the G cells further
110
Describe the inhibition of gastric juice secretion in the endocrine cells
Acid acts on the endocrine cells in the duodenum causing the release of enterogastrones which act on D cells increasing somatostatin
111
Name some enterogastrones
Secretin, enteroglucagon, cholecystokinin, peptide YY, somatostatin, neurotensin
112
Which cells secrete HCl in the stomach?
Parietal oxyntic
113
What actions does HCl have in the stomach?
Denatures proteins
Activates pepsinogen to pepsin
Solubilises and maintains iron in ferrous state for absorption
114
What can achlorhydria lead to?
Decreased iron absorption and anaemia
115
Which cells secrete pepsinogen?
Chief cells
116
What activates pepsinogen to pepsin?
Removal of a short peptide in acid conditions
117
What pH is optimal for pepsinogen?
3.5
118
What percentage of protein digestion is pepsin responsible for ?
<20%
119
Is pepsin essential? Why or why not?
No as pancreatic proteases can compensate
120
Which cells secrete gastric lipase?
Chief cells
121
What pH is optimal for gastric lipsae?
3-6
122
Action of gastric lipase?
Contributes to hydrolysis of lipids
123
What can gastric lipase partially compensate for?
Decreased pancreatic lipase secretion in pancreatic dysfunction
124
Which cells secrete intrinsic factor?
Parietal cells
125
Action of intrinsic factor
Binds to B12 and enables its absorption
126
Which cells secrete mucin in the stomach?
Mucus-secreting neck cells
127
Purpose of mucus in the stomach
Forms a barrier over the mucosal surface to protect it from gastric contents
Lubricates the mucosal surface to protect against abrasive effects of contents
128
Which cells secrete bicarbonate in the stomach?
Surface epithelial
129
Where is bicarbonate located in the stomach?
Trapped in the unstirred layer between the mucus blanket and the mucosal surface
130
Action of bicarbonate in the stomach?
Neutralises acid
Deactivates pepsin
131
What are the aims of the drugs used to treat gastritis, ulcers, and reflux disease?
Reduce acidity of stomach contents to prevent further damage and allow time for healing
132
Proton pump inhibitor examples?
Omeprazole, lansoprazole
133
Antacid examples
Aluminium hydroxide, sodium bicarbonate
134
H2 agonist in gastric disease example
Ranitidine
135
Describe the activation of parietal cells in the stomach
Tubular vesicles are inserted into the apical membrane and canaliculi are created which increases area exposed to the lumen
136
What do tubular vesicles contain?
Proton pumps
137
Anatomical barrier for gastric juice
Resistant epithelium - apical ,membrane and tight junctions
138
Physiological barrier for gastric juice
Mucus gel layer and bicarbonate microclimate
139
What stimulates mucus in the stomach?
Vagus nerve and irritation
140
What stimulates the protection of the gastric mucosa?
Presence of acid in the duodenum
Central and enteric nervous systems (ACh and VIP)
Prostaglandins
141
What inhibits the protection of the gastric mucosa?
COX inhibitors
H pylori
Alpha 2 adrenergic receptor stimulation
142
Gastritis
Inflammation of the lining of the stomach
143
Peptic ulcers
Open sores in the lining of the stomach or duodenum >5mm in diameter that extend into the submucosa
144
Erosions
Peptic ulcers <5mm or without depth
145
Causes of peptic ulcers and gastritis?
H pylori
Alcohol
NSAIDs
146
What causes mast cell damage in the mucosa?
Pepsin allowing H+ into the mucosa
147
Sensory innervation of nasopharynx
trigeminal
148
Sensory innervation of oropharynx
glossopharyngeal
149
Sensory innervation of layrngopharynx
vagus
