GI anatomy overview (lecture) Flashcards
(136 cards)
1
Q
What is the mouth otherwise referred to as?
A
Oral cavity
Buccal cavity
2
Q
What type of epithelium is the “oral mucosa”?
A
stratified squamous epithelium
(Thick and resistant to abrasion)
3
Q
Where is the oral mucosa found?
A
Lining the oral cavity
4
Q
What are childhood “milk” teeth called?
A
Deciduous teeth
5
Q
What does the oral mucosa produce and secrete?
A
Defensins to inhibit bacterial growth
6
Q
What is the role of defensins produced by the oral muscosa?
A
Inhibit bacterial growth
7
Q
How many deciduous teeth does a child have?
A
20
8
Q
When do deciduous teeth come in?
A
First 6-24 months of life
9
Q
What are adult teeth called?
A
Permanent teeth
10
Q
At what age should all deciduous teeth have been replaced, roughly?
A
Approx 12 yrs old
11
Q
What is the bony ridge called that hold the sockets of the teeth?
A
Alveolar ridge of the maxilla (top) and mandible (bottom)
12
Q
How many permanent teeth does an average person have?
A
32
13
Q
How many incisors are in an adult mouth?
A
8
- 4 top (2 each side)
- 4 bottom (2 each side)
14
Q
What is the action of incisors?
A
Slice and cut
15
Q
How many canines does an adult mouth have?
A
4
- 2 top (1 each side)
- 2 bottom (1 each side)
16
Q
What is the action of canines?
A
Tear and rip
17
Q
How many premolars are in an adult mouth?
A
8
- 4 top (2 each side)
- 4 bottom (2 each side)
18
Q
What is the action of premolars?
A
Grind and crush
19
Q
How many molars does an adult mouth have?
A
12
- 6 top (3 each side)
- 6 bottom (3 each side)
20
Q
What is the action of molars?
A
Grind and crush (mainly grind)
21
Q
What are cavities?
A
Gradual demineralisation of enamel
22
Q
What causes cavities?
A
Acid production from bacteria in plaque
23
Q
What is the formula for types of teeth in 1 quadrant of the mouth (e.g the top left side) ?
A
2I, 1C, 2PM, 3M
2 incisors
1 canine
2 premolars
3 molars
24
Q
Name the 4 types of teeth in an adult mouth…
A
- incisors
- canines
- premolars
- molars
25
Name the teeth in 1 quadrant of the mouth in order, front to back…
- central incisor
- lateral incisor
- cuspid (canine)
- first premolar (bicuspid)
- second premolar (bicuspid)
- first molar
- second molar
- third molar
26
What is another name for cavities?
Dental caries
27
What can missing teeth cause?
Excessive wear on the corresponding teeth above/below the abscess
28
What are the 3 main salivary glands?
Parotid
Sublingual
Submandibular
29
What % of saliva is water?
Approx 99%
30
Is saliva acidic, neutral or alkaline?
Slightly acidic (pH 6.75 - 7) to provide optimal conditions for enzyme action
31
What enzymes does saliva contain?
- lipase
- alpha-amylase
- lysozyme
32
What does saliva contain?
- water (99%)
- lipase
- amylase
- lysozyme
- mucoproteins (mucin for lubrication)
- immunoglobulins (esp, IgA)
- electrolytes
- calcium and phosphate (dental repair)
33
Which immunoglobulin is most abundant in saliva?
IgA
34
What approximate pH is saliva at?
6.75 - 7
35
Which element in saliva acts to lubricate the passage of food ?
Mucoprotiens (mucin)
36
Where are the salvatory nuclei located?
Pons and medulla
37
What type of receptors in the mouth stimulate watery saliva production ?
Mechanoreceptors
Chemoreceptors
38
Which type of receptors trigger saliva production when non-food objects enter the mouth?
Mechanoreceptors
39
What is the composition like of saliva produced in reaction to:
a) non-food stimuli ?
b) food stimuli ?
High **water** content = **non-food** stimuli
High **enzyme** content = **food** stimuli
40
Name the 2 intrinsic nerve plexuses in control of gut function …
**Myenteric** nerve plexus
**Submucosal** nerve plexus
41
Are the myenteric/submucosal nerve plexuses sympathetically or parasympathetically innervated?
Parasympathetic innervation
42
Which cranial nerve regulates the enteric nervous system (ENS)?
CN X = **Vagus**
43
What are the 3 divisions of the autonomic nervous system ?
Sympathetic NS
Parasympathetic NS
Enteric NS
44
What is the Enteric Nervous System (ENS) ?
The nervous system exclusively influencing the GI system
45
What are the 2 principle components of the enteric nervous system ?
- **myenteric** (Auerbach's) plexus
- **submucosal** (Meissner's) plexus
46
What is the function of the myenteric plexus?
**Controls digestive tract motility**
Increase muscular tone/**strength**/velocity of muscular contractions in **peristalsis**
47
What is the function of the submucosal plexus?
**Controls absorption**
Controls localised secretions, local muscular action, blood flow and, therefore, absorption of nutrients
48
What are the layers of the wall of the GI tract?
- lumen of GI tract
- mucosa
- submucosa (containers submucosal plexus)
- muscularis externa (circular muscular layer -> myenteric plexus -> longitudinal muscular layer)
- serosa
49
What 2 layers make up the muscularis externa in the GI tract wall?
- circular muscular layer (inner)
- longitudinal muscular layer (outer)
50
What action does contraction of the circular muscular layer have in the gut?
Squeezes gut contents
51
What action does contraction of the longitudinal muscular layer have in the gut?
Shortens that portion of the gut
52
Are the smooth muscle layers in the gut (muscularis externa) regulated or spontaneously active?
Smooth muscle in the gut is **spontaneously** active
*regulated by enteric or extrinsic neurones*
53
What are the pace maker cells of the gut called?
Interstitial cells of cajal (found in circular smooth muscle)
54
Where are the pacemaker cells (cells of cajal) found in the gut lining?
In the circular muscle layer of the muscularis externa
55
What can a loss of interstitial cells of cajal result in?
Gut motor dysfunction disorders
56
How long is the average oesophagus in adults?
Approx. **25cm** long
*(Pharynx to stomach)*
57
What structures are contained within the submucosal layer of the GÌ tract?
- blood vessels
- lymphatics
- nerves
- lymphoid tissue
- mucus glands
58
Which sections of the oesophagus are voluntary/involuntary with regards to innervation of muscularis externa muscle?
- first 1/3 = voluntary **skeletal** muscle (decide to swallow)
- last 1/3 = involuntary **smooth** muscle (food pushes through involuntarily)
- middle third = mixed
59
What is adventitia?
The outer layer of fibrous connective tissue surrounding an organ
60
What is the outer layer of the oesophagus mainly made up of?
**Adventitia** fixed to adjacent structures via connective tissue
*(fibrous connective tissue)*
61
Which part of the oesophagus is cover with serosa (rather than adventitia?)
Serosa = past the diaphragm
62
Is the oesophagus held open or closed during relaxation periods?
The oesophagus is closed until food/an object pushes through it
63
What is the mucosa like within the oesophagus?
Highly folded (when oesophagus is closed)
64
What kind of epithelium is found in the oesophagus?
Stratified squamous epithelium
*resists abrasion*
65
What is the epithelium like in the GI tract after the oesophagus (at gastro-oesophageal junction) ?
Columnar epithelium (glandular)
66
What is a condition called that is seen in some patients prior to developing oesophageal cancer?
Barrett's oesophagus
67
What is Barrett's Oesophagus?
Unusual change of the epithelium within the oesophagus (from normal stratified to the columnar epithelium seen in gastric tract) **due to to repeated damage from gastric reflux**
68
What can cause Barrett's Oesophagus ?
Acid/gastric reflux
69
Which *general* part of the stomach undergoes peristalsis?
Lower part of stomach
70
Which valve in the stomach acts in response to peristalsis?
Pyloric valve
71
What features of the stomach cause vigorous churning and slow gastric emptying of the stomach?
- peristalsis
- pyloric valve
72
What are the longitudinal mucosal folds called in the stomach ?
Rugae
73
Are the stomach's mucosal and submucosal layers thin or thick?
Thick
74
What is one factor that controls the rate of gastric emptying of the stomach?
The caloric value of the contents in the duodenum
(duodenum = the next part of GI tract connected to stomach)
75
Which valve separates the stomach and the duodenum?
Pyloric valve / pylorus
76
What is the period/state between meals called?
**Inter**digestive state
77
When does the migrating motor complex (MMC) occur?
Between meals, in the interdigestive state
78
How long can it take for the migrating motor complex (MMC) to pass along the small intestine?
Up to 2 hours
79
What is the role of the migrating motor complex (MMC) ?
“House keeping” role = sweeps undigested material through the gut after eating
80
What is the migrating motor complex (MMC)?
Small irregular contractions of the small intestine during a period of ‘fasting’
81
What acts as a signal to **stop** the migrating motor complex (MMC)?
Release of **gastrin** and **cholecystokinin** in response to **eating**
*eating triggers peristalsis which is better suited to nutrient absorption*
82
Where is gastrin released from ?
The stomach
83
What is gastrin?
Peptide hormone that aids in gastric motility
84
Where is cholecystokinin (CCK) released from ?
The small intestine
85
What is cholecystokinin (CCK)?
A peptide hormone that stimulates fat and protein digestion
86
Which peptide hormone is a potent inhibitor of gastric emptying? What is it responding to?
Cholecystokinin (CCK)
*Stops gastric emptying in response to high caloric value in the duodenum*
87
What are the 3 parts of the small intestine in order?
- **duodenum** (closest to stomach)
- **jejunum**
- **ileum**
88
What are the parts of the large intestine, in order ?
- cecum
- ascending colon
- transverse colon
- descending colon
- rectum
- anus
89
What is another term for the large intestine?
The colon
90
Which part of the colon has the longest transit time?
The **transverse** colon
91
What is the average transit time in the colon?
2-3 days !
92
Is the colon active:
a) constantly ?
b) spontaneously ?
c) during eating ?
d) during fasting ?
The colon is active **constantly**
93
Haustral contractions Vs peristalsis in the colon?
Haustral contractions
= circular muscle contractions every 20/25 mins
= move food along the colon, from one haustra (pocket/bulge) to the next
= slow and continuous
Peristalsis
= circular + longitudinal muscle contractions 1/2 times a day
= shifts formed faecal matter from colon to rectum/anus
= relatively fast/forceful and infrequent
94
What does contraction of **circular** muscles in the colon cause?
Haustra = the rippled-looking bulges/pockets of the gut that are full of food
95
What is a haustrum?
A pocket in the colon formed by circular muscle contraction on either side of food
*gives the colon it’s rippled/bulging appearance*
96
What is the gastrocolic reflex ?
Powerful **propulsive contractions** are initiated **in the colon** when food enters the stomach
*= dispels waste products to allow space for the new food entering*
97
Where is gastrin produced/secreted?
**Pyloric antrum** (just before the valve)
98
Which cells produce gastrin in the stomach?
G cells
99
What are the functions of the stomach ?
- mix food
- act as a reservoir
- synthesise intrinsic factor
- start digestion (activates enzymes)
- destroy some bacteria/pathogens
- absorb some water, alcohol and B12
100
What is the only essential function of the stomach ?
Synthesis of **intrinsic factor**
(Intrinsic factor allows B12 absorption)
101
What does intrinsic factor do?
Allows for **B12 absorption** in the intestines
102
What is the rough pH of the stomach?
pH 1 - 2
(very acidic)
103
Which acid is found in the stomach?
Hydrochloric acid
104
Where is the majority of alcohol absorbed in the GI tract?
Duodenum and jejunum
(Small intestine)
105
Name the **exo**crine and **endo**crine gastric (stomach) secretions …
EXOcrine secretions:
- hydrochloride acid
- mucus
- Pepsinogen
- intrinsic factor
ENDOcrine secretions:
- gastrin
- somatostatin
106
What do goblet cells secrete in the stomach?
Alkaline mucus
*(to protect the epithelium from acidic conditions within stomach)*
107
What do mucous cells secrete in the stomach?
- Mucus
- Pepsinogens
108
What do parietal cells secrete in the stomach?
- gastric acid
- intrinsic factor
109
What do chief cells secrete in the stomach?
- pepsin
- gastric lipase
110
What do G cells secrete in the stomach?
Gastrin
111
What do D cells secrete in the stomach? Where are they found?
Secrete: somatostatin
Found: in antrum (close to pyloric valve)
112
What is the function of hydrochloric acid in the stomach?
- **kills pathogens**/bacteria
- **initiates digestion**
- **produces pepsin** from pepsinogen precursor
113
What is the function of mucus in the stomach?
Protects mucosal surface from damage caused by HCl
114
What is the function of pepsinogen in the stomach?
Precursor of the endopeptidase pepsin
115
What is the function of intrinsic factor in the stomach?
- Important in the absorption of B12 (in the gut)
- important in erythropoeisis
116
What is the function of gastrin in the stomach?
Stimulates gastric acid production for digestion
117
What is the function of somatostatin in the stomach?
Inhibits release of gastrin
118
What is an endopeptidase? Function?
An enzyme that **hydrolyses the inner bonds** between amino acids (rather than the terminal/end bonds) **= shortens amino acid chains**
119
Stimulation of which nerve increases pepsinogen secretion in the stomach?
Vagus nerve
(CN X)
120
Which neurotransmitter acts to increase pepsinogen secretion via CN X ?
Acetylcholine
121
Which chemicals act as stimulants for the secretion of hydrochloric acid (HCl) in the stomach?
- **acetylcholine** (via vagal input)
- **gastrin** (from G cells)
- **histamine** (from enterochromaffin cells)
- other hormones
122
Stimulation of which nerve can increase secretion of HCl in the stomach?
Vagus nerve
(CN X)
123
What are the factors/chemicals that inhibit gastric acid secretion?
- somatostatin
- secretin
- gastric inhibitory peptide (acts on parietal cells)
124
What are the 3 phases of gastric acid secretion called?
1. Cephalic phase (40%)
2. Gastric phase (50%)
3. Intestinal phase (10%)
125
Roughly what % of gastric acid secretion occurs in the cephalic phase?
40%
126
Roughly what % of gastric acid secretion occurs in the gastric phase?
50%
127
Roughly what % of gastric acid secretion occurs in the intestinal phase?
10%
128
Which phase(s) of gastric acid secretion is/are vagally (CN X) mediated ?
Cephalic phase
Gastric phase
129
What factors trigger the Cephalic phase of gastric acid secretion?
Thought, smell, sight and taste of food
130
How does the Cephalic phase result in gastric acid secretion?
- Thought/sight/taste/smell of food releases Acetylcholine (via vagus nerve)
- ACh stimulates parental cells and G cells to release gastrin
131
How does the gastric phase result in gastric acid secretion?
- Distension, reflex activation of enteric neurones and vagal outflow stimulates parietal cells and G cells to secrete gastrin + gastric acid
*- digested proteins in stomach stimulate G cells too*
132
How does the intestinal phase result in gastric acid secretion?
Amino acids in the blood (from protein digestion) directly stimulate parietal cells to produce gastric acid
133
What are the 2 mechanisms that inhibit gastric acid secretion ?
1. Gastric mechanism
2. Duodenal mechanism
134
How does the **gastric mechanism** of inhibiting gastric acid secretion work?
- if proteins are in the stomach they create a buffer to keep lumen pH > 3 (normal)
- as stomach empties, lumen pH falls **below pH 3**
- **stimulates D cells** to **release somatostatin** to inhibit gastrin release
135
How does the **duodenal mechanism** of inhibiting gastric acid secretion work?
*as stomach empties into duodenum lumen pH falls*
1. acidification of duodenal lumen stimulates **secretin release** (inhibits gastrin secretion)
2. acidification of duodenal lumen + presence of fatty acids and salt **release gastric inhibitory peptide** which acts on parietal cells to inhibit HCL secretion
136
List the 6 major GI hormones and where they’re produced…
1. Gastrin // G cells in antrum of stomach
2. Motilin // duodenum
3. Gastric inhibitory peptide (GIP) // small intestine
4. Cholecystokinin (CCK) // small intestine
5. Secretin // small intestine
6. Vasoactive intestinal peptide (VIP) // glands and nerves
