The GIT Flashcards
1
Q
The gastrointestinal tract is approximately …meters in an adult
A
4.5
2
Q
What are the 4 key processes of the GIT?
A
Motility
* Digestion
* Secretion
* Absorption
3
Q
What are the 6 steps on the GIT in order?
A
- Ingestion
- Motility
- Digestion
- Secretion
- Absorption
- Defecation
4
Q
Pair the parts of the GIT with their function:
- Oral cavity, pharynx,
oesophagus, anal canal - Stomach
- Small intestine
- Large intestine
A. Absorptive
B. Protective
C. Absorptive/protective
D. Secretory
A
1B, 2D, 3A & 4c
5
Q
Which of the following is NOT composed of simple squamous epithelium?
- Oral cavity, pharynx,
oesophagus, anal canal - Stomach
- Small intestine
- Large intestine
A
1 is composed of stratified squamous epithelium
6
Q
In which parts of the GIT does food get propelled forward?
A
Esophagus
Stomach
Small & Large intestines
7
Q
In peristalsis which of the following comes first?
A. Contraction of circulatory muscles
B. Contraction of longitudinal muscles
A
A.
8
Q
In peristalsis circulatory muscles contract ahead/behind the food bolus whilst longitudinal muscles contract ahead/behind the food bolus
A
behind
ahead
9
Q
Segmentations occurs in which parts of the GIT?
A
The small and large intestine
10
Q
T or F
Segmentation is slow
A
T
11
Q
T or F
Segmentation is not mechanical digestion
A
F
12
Q
There are 9-12 contractions per minute in the small/large intestine and 3-12 contractions per minute in the small/large intestine
A
small
large
13
Q
Which function of the GIT am I?
- Mixes chyme with digestive secretions
- Increases exposure to
epithelium for absorption
A
Segmentation
14
Q
Involuntary control of the GIT can be caused by…
A
External stimuli
Long reflexes
15
Q
Examples of voluntary control of the GIT are…
A
Ingestion & swallowing
Defecation (some)
16
Q
Internal stimulation of the GIT tract activates what 3 types of receptors?
A
Chemoreceptors,
osmoreceptors,
mechanoreceptors
17
Q
What are the effectors of the GIT tract?
A
Smooth muscle
or glands
18
Q
What in the saliva can break down carbohydrates?
A
salivary amylase
19
Q
What in the saliva can break down lipids?
A
lingual lipase
20
Q
The oral cavity performs what four things for the GIT?
A
- Ingestion and sensory analysis (pressure, temp and taste) before swallowing
- Mastication (mechanical digestion) – teeth, tongue, and palatal surfaces
- Lubrication – mixing with mucus and salivary secretions (mucins)
- Limited digestion of carbohydrates &
lipids (immediate chemical digestion)
21
Q
What is the pH of lingual lipase?
A
pH 3.0 – 6.0
22
Q
Match the oral cavity glands with their functions:
- Parotid gland
- Submandibular gland
- Sublingual gland:
A. Salivary amylase → starch breakdown
B. Mucus → buffering & lubrication
C. Buffers, glycoproteins (mucin) + salivary amylase
A
1A, 2C and 3B
23
Q
Saliva is …% water
A
99.4
24
Q
Other than water, what is saliva composed of?
A
Electrolytes, antibodies, buffers (pH 7.0),
mucins, enzymes, immunoglobulins, lysozomes
25
What can activate the salivary centre in the medulla?
The cerebral cortex (upon seeing, smelling or thinking about food)
Pressure receptors and chemoreceptors in the mouth
26
What events take place when the salivary centre in the medulla is activated?
The medulla activates autonomic nerves which activate salivary glands which increases salivary secretion
27
What nerves innervate the taste buds?
Trigeminal (CN V), Facial (CN VII) & Glossopharyangeal (CN
IX)
28
T or F
There aren't chemoreceptors on taste buds
F
28
During the buccal phase of digestion afferent signals are sent to the swallowing centre via
... and ... nerves
Trigeminal & Glossopharyngeal
29
Is the pharyngoesophageal sphincter closed or open when swallowing?
closed
30
Efferent signals via ... and ... nerves mediate peristaltic contractions in
esophagus muscles
Vagus & Glossopharyngeal
31
The Body of the stomach is also known as the...
oxyntic mucosa
32
Which part of the stomach has the most gastric glands?
the body/oxyntic mucosa
33
Temporary storage of the stomach ranges from ...mL to ...L
50
1.5
34
What does the stomach secrete?
HCl, pepsinogen, intrinsic factor, gastric lipase
35
What does the stomach secrete to break down proteins?
HCl and pepsin
36
What does the stomach secrete to break down fats?
gastric lipase
37
Chyme is composed of...
bolus + gastric secretions
38
What does the stomach absorb?
Some absorption – water, ions, alcohol (lipid soluble), aspirin (weak acid,
lipid soluble)
39
How does gastic mixing occur?
When the pyloric sphincter closes abruptly chyme is disrupted and slushes backwards
40
What three exocrine cells aid in chemical digestion?
Mucous cells
* Parietal cells
* Chief cells
41
Match the cell to its secretion:
A. Mucous cells
B. Parietal cells
C. Chief cells
1. HCl, intrinsic factor
2. pepsinogen, gastric lipase
3. mucous
A3, B1, C2
42
Exocrine cells are stimulated by...
* Vagus & intrinsic nerves
* pH of lumen
* Distension from presence of bolus
* Chemical contents (proteins)
43
Enterochromaffin-like (ECL) cells secrete
... and are stimulated by what two things?
histamine
* Triggered by gastrin
* Increases Chief & Parietal cell activity
44
G Cells secrete ... (acts via bloodstream) and are stimulated by what two things?
gastrin
* Mediated by Vagus nerve & presence of proteins
* Increases Chief & Parietal cell activity
45
D Cells secrete ... and are stimulated by what two things?
somatostatin
* Stimulated by acid accumulation in duodenum
* Decreases Chief, Parietal & ECL cell activity
46
List the three Regenerative (stem) cells/Entero-endocrine cells (regulation) of the GIT
D cells
G cells
ECL cells
47
... acid maintains stomach lumen and provides non-specific disease resistance by destroying most ingested pathogens
Hydrochloric
48
H+ and Cl ions are
released as ...
and combined in ...
as HCl
ions
lumen
49
T or F
HCl is critical for enzyme activation
T
50
... converts pepsinogen (secretes by chief cells) to pepsin (active enzyme)
HCl
51
Pepsin is a ... enzyme –
digests proteins
proteolytic
52
The mucous in the gut provides protection from what?
Protection from acidic
environment and pepsin
53
Stomach activity involves three phases – ..., ... and ...
Mediated by ..., ... and ... factors
Cephalic, Gastric & Intestinal
Neural, hormonal and local
54
Acetylcholine (Ach) is released by .... in the stomach, under control of .... & ...
intrinsic nerve plexuses
short local reflexes
vagus nerve
55
Gastrin (G cells) require .... for release, stimulates ... and ... cell activity
vagal stimulation
chief and parietal
56
Histamine (ECL cells) – released in response to ..., secondary stimulant of ... and ... cells
gastrin
chief and parietal
57
Somatostatin (D cells) – released in response to ... accumulation in the ...
... affect on ..., ... and ... cells
acid
duodenum
duodenum
inhibitory
parietal, G & ECL
58
... receptors are responsible for distension and emptying of stomach and duodenum
Stretch
59
Stretch receptors are located in the ....
small intestine
60
Enterogastrones (CCK, secretin) – presence of ... in duodenum, ... affect on .... and ....
chyme
inhibitory
gastric secretions and motility
61
The ... phase of gastric secretion is short (minutes) whilst the ... and ... phases are long (hours)
cephalic
gastric and intestinal
62
Which mechanisms does the body use in order to prepare the stomach for the arrival of food?
The CNS uses the vagus nerve to stimulate the submucosal plexus, which then stimulates the mucous, chief, parietal and g cells to secrete their respective products (gastric juices). (Enteric neural stimulation of gastric cells)
63
(referring to the mechanics of the gastric phase of digestion)
Distension is detected by ... receptors and alerts the ... plexus
An elevated pH detected by ...receptors and alerts the ... plexus
Partially digested peptides promote ... cells to secrete more ...
stretch
myenteric
chemo
submucosal
G
gastrin
64
During the gastric phase of digestion the presence of partially digested peptides promote G cells to secrete more gastrin. What effects does gastrin then have on the stomach?
It encourages chief and parietal cells to secrete more pepsinogen and HCL and enhances gastric motility
65
During the gastric phase of digestion distention and an elevated pH are detected by stretch and chemoreceptors. What effects does this then have on the stomach?
The stretch and chemoreceptors send messengers to the submucosal and myenteric plexuses which then increase stomach contractions and promote gastric secretions from chief, parietal, mucous and G cells
66
During the intestinal phase of digestion ... and ... trigger the enterogastric reflex
distension
low pH
67
During the intestinal phase of digestion a low pH triggers ... cells to release ...
D
somatostatin
68
The presence of lipids and carbohydrates in the stomach triggers the release of ... and ... which then inhibit the activity of ... and ... cells and peristalsis
CCK and GIP
chief and parietal
69
A decreased pH in the stomach triggers the release of ..., ... and ....which then inhibit the activity of ... and ... cells and peristalsis
secretin
CCK and GIP
chief and parietal
70
What are the 3 actions of the intestinal phase of digestion?
* ↓ gastric contractility & gastrin secretion
* Stimulation of accessory organs
71
... and ... stimulate accessory organ
functions
CCK
Secretin
72
What effects does secretin have on the liver?
Increase bile, HCO3
production
73
Presence of ..., ... and ...
stimulate release of enterogastrones
lipids, proteins & carbs
74
T or F
Choleocystokinin (CCK) and secretin stimulate accessory organ functions
T
75
What are the 6 steps of the accessory organs?
1- Chyme enters duodenum
2- CCK & secretin
released
3- CCK causes pancreas to secrete digestive enzymes.
Secretin causes pancreas to secrete HCO3 & mucous
4- Secretin causes liver to increase bile and HCO3 production
5- CCK causes gallbladder to contract and relax sphincter so bile enters duodenum
6- Secretion of digestive
enzymes, buffers & bile for
chemical digestion in SI
76
What effect does secretin have on the liver?
Increase bile, HCO3
production
77
What effect does CCK have on the gallbladder?
Contract gallbladder
Relax sphincter
Bile enters duodenum
78
What effect does CCK have on the pancreas?
Causes the pancreas to secrete digestive enzymes
79
What effect does secretin have on the pancreas?
Causes the pancreas to secrete HCO3 & mucous
80
What is the endocrine proportion of the pancreas called?
The islets of Langerhans
81
T or F
Endocrine glands have local effects
Exocrine glands have systemic effects
F
vice versa
82
What two cells compose the exocrine portion of the pancreas?
Duct and acinar cells
83
What do duct cells secrete?
Water, ions, HCO3
84
What do acinar cells secrete?
Digestive enzymes
85
What are the 2 endocrine hormones of the pancreas?
insulin and glucagon
86
What function do the products secreted by duct cells perform?
Neutralise acid in the duodenal lumen
87
What function do the products secreted by acinar cells perform?
They digest fat, protein and carb products in
duodenal lumen
88
T or F
The vagus nerve stimulates acinar cells during the cephalic phase of gastric function
T
89
Pancreatic nucleases break down ... into ...
nucleic acids (DNA/RNA)
nucleotides
89
Pancreatic lipase breaks down ... into ...
Lipids (triglycerides) → fatty acids, monoglycerides
90
Pancreatic amylase breaks down ... into ...
Starch, glycogen (carbs) → tri/disacchirides
91
What proteolytic enzymes in the pancreas break down proteins into di/tripeptides?
* Trypsinogen (inactive form)
* Chymotrypsinogen
* Pro-carboxypeptidase
92
What comprises the biliary system?
Liver & gallbladder & ducts
93
What comprises the hepatic blood supply?
The hepatic artery and hepatic portal vein
94
T or F
The liver is composed of 3 lobes
F
2 (left and right)
95
What are sinusoids?
“Leaky capillaries”
Highly permeable
endothelium – rapid and
rich blood supply to
hepatocytes
Waste removal – Kupffer
cells engulf & destroy old
RBCs, bacteria
Drain into central vein
96
What are the functions of the liver?
* Carbohydrate, lipid and protein metabolism
* Store vitamins (A, D, K) and minerals (iron, zinc, magnesium)
* Phagocytosis of RBC, WBC and bacteria
* Processing of hormones and drugs
* Bile salt and bile production (increased upon secretin stimulation)
97
What are bile canaliculi?
Collection of bile
secreted by
hepatocytes
98
What sphincter connects the bile duct and the pancreatic duct to the duodenum?
Hepatopancreatic
sphincter
(sphincter of Oddi)
99
What sphincter appears on the bile duct just before the hepatopancreatic sphincter?
Sphincter of common
bile duct
(sphincter of Boyden)
100
What is bile composed of?
* Water & ions – to dilute & buffer acids in chyme
* Bilirubin – from haemoglobin
* Cholesterol
* Bile salts – made from cholesterol
101
What drains into gallbladder via cystic duct?
* Storage of bile – capacity for 40-70mL
* Concentrates bile – osmotic efflux of water
* Releases bile upon digestive need – neural &
hormonal stimulation
102
Bile is produced in the ..., stored in the ...
liver
gallbladder
103
Bile secretion triggered during ... phase of gastric function
Intestinal
104
T or F
The liver creates bile continuously
T
105
T or F
Bile becomes more concentrated the longer it stays in the gallbladder
T
106
When chyme is present in the duodenum, CCK is released. What effects does this have on the gallbladder?
CCK triggers dilation of the hepatopancreatic sphincter and contraction of the gallbladder. This ejects bile into the duodenum through the duodenal ampulla
107
In the lumen of the digestive tract, bile salts break down lipid droplets by ...
emulsification
108
...% of bile salts are re-absorbed at the terminal ileum
95
109
What accessory organ of the GIT is the major site of chemical digestion and 90% of all nutrient absorption?
The small intestine
110
The small intestine extends from the ... to the ...
pyloric sphincter (stomach-SI junction)
ileocecal sphincter (SI-LI junction)
111
What are the 3 segments of the small intestine and their respective lengths?
* Duodenum – first 25 cm, site of accessory organ
secretions
* Jejunum – 2.5 m, site of most chemical digestion &
nutrient absorption!
* Ileum – 3.5 m, longest and final portion before large intestine
112
What are the secretory cells of the mucosal layer of the small intestine?
* Brush border cells – enzymes for chemical digestion
* Goblet cells – mucins to buffer acidic content
* Paneth cells – antimicrobial peptides,
immunomodulating proteins to regulate the gut microbiome (gut immunity)
* Submucosal glands – mucous, HCO3
113
T or F
Stem cells aren't present in the mucosal layer of the small intestine
F
114
T or F
Digestion begins prior to the small intestine
T
115
T or F
Solely chemical digestion facilitates the breakdown of chyme contents into simplest units
F
Chemical AND mechanical digestion facilitates breakdown of
chyme contents into simplest units
116
Nutrients have to cross what TWO membranes to be absorbed?
* From the lumen across gut epithelium
* Across basolateral membrane into capillaries/lacteal
117
Fructose is absorbed across the gut lumen via facilitated diffusion by ...
GLUT5
118
Glucose is absorbed across the gut lumen via what two methods?
Sodium-linked cotransport & secondary active
transport
119
Glucose, galactose and glucose are transported into blood capillaries by ...
GLUT2
120
What is enterokinase?
A protease of the intestinal brush border that specifically cleaves the acidic propeptide from trypsinogen to yield active trypsin.
121
Which brush border enzymes convert small peptides → amino acids?
Aminopeptidase and dipeptidase
122
Which intracellular enzymes convert small peptides → amino acids?
intracellular peptidase
123
Which proteolytic enzyme converts large → small polypeptides?
Chymotrypsin
124
Which proteolytic enzyme converts small polypeptides → amino acids?
Carboxypeptidase
125
Which proteolytic enzyme activates other peptidases?
Trypsinogen (in its active form trypsin)
126
What modes of transport help amino acids cross the gut epithelium?
Sodium-linked cotransport & secondary active transport
127
What facilitates the transportation of sodium peptides across the gut epithelium?
Sodium-linked tertiary active transport
Na+
-H+ counter-transport: Na+ into cell down
conc gradient; H+ out of cell against conc
gradient
* Peptides co-transported with H+ down conc
gradient into cell
128
Bile salts used to package simple fats into ...
micelles
129
Bile salts bind to & break apart large fat ...
globules
130
T or F
Lipids passively diffuse across the gut epithelium
T
131
Lipids coagulate with lipoproteins to become...
Chylomicrons
132
How to chylomicrons leave the epithelial cells of the villus and enter the central lacteal ducts via what process?
exocytosis
133
What are the 3 main functions of the large intestine?
Absorption
Storage of waste
Defecation
134
... cells of the intestinal
glands have local reflexes in response to friction from the passing faecal matter
Goblet
135
What is the outer longitudinal muscle of the externa muscalaris called?
Taeniae coli
136
T or F
The Taeniae coli is organised as 4 individual “bands” along length
of colon
F
3
137
What part of the large intestine is formed by tonic contraction of inner,
circular muscle layer?
Haustra
138
T or F
Haustra are segmented pouches separated by
haustral folds
T
139
What is meant by the words 'Haustral "shuffle"'
The haustral shuffle is how motility works along the large intestine wherein phasic contraction of circular muscle at adjacent sections churns contents. Slow progression (shuffle) along colon length, ~ every 30 mins
140
What is the gastro colon -colic reflex?
Progressive, powerful, sweeping (mass) contractions at colon sections
141
How many gastro colon -colic reflex does a human have each day?
3-4
142
Feces are stored in the .... until defecation
distal portion (sigmoid
colon)
143
How are stretch receptors in the rectum stimulated and what nerve is innovated?
When feces move into and distend the rectum, stimulating stretch receptors that send signals via afferent fibers to spinal cord neurons.
144
During defecation a spinal reflex is initiated in which
... motor (efferent)
fibers stimulate contraction of the
... and ...., and
relaxation of the ....
parasympathetic
rectum and sigmoid colon
internal anal sphincter
145
If it is convenient to defecate, voluntary ... neurons are ..., allowing external anal sphincter to relax so feces may pass
motor
inhibited
146
T or F
Messages from the motor
nerve to the external
anal sphincter are voluntarily controlled
T
147
T or F
When it comes to defecation neural stimulation is voluntarily controlled whilst neural inhibition is involuntarily controlled
F
Vice versa
148
T or F
Messages through the motor nerve to the internal anal sphincter sent via the parasympathetic nervous system are voluntary
F
Involuntary
