The Gastrointestinal System Flashcards
(111 cards)
1
Q
What is the basic overall function of digestive system?
A
- Digestion
- Absorption
- Motility
- Secretion
- Excretion
2
Q
What is digestion?
A
Chemical and mechanical breakdown of large food particles into particles small enough to be absorbed
3
Q
What is absorption?
A
Movement of organic substrates, electrolytes, vitamins and water across digestive epithelium into blood
4
Q
What is motility?
A
Smooth muscle contraction - movement and mixing
5
Q
What is secretion?
A
Of water, mucus, acids, enzymes, buffers and salts
6
Q
What is excretion?
A
Of wast material
7
Q
What are the different forms of motility along the length of GI tract?
A
- Peristalsis
- Segmentation contractions
- Migration motility complex
- Haustral contraction
8
Q
Where does peristalsis motility occur?
A
Oesophagus and stomach
9
Q
Where does segmentation contractions occur?
A
Small intestine
10
Q
Where does migrating motility complex occur?
A
Small intestine
11
Q
Where does haustral contraction occur?
A
Large intestine
12
Q
What does the GI tract consist of?
A
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
- Anus
13
Q
What are the four-layer structure of the GI tract wall?
A
- Mucosa
- Submucosa
- Muscularis
- Serosa
14
Q
What is the mucosa?
A
- Contains epithelial cell layer, connective tissue, muscular mucosa
- Mucus-associated lymphoid tissue
15
Q
What is submucosa?
A
-Connective tissue containing nerves, blood vessels and glands
16
Q
What is muscular?
A
-Circular and longitudinal layers of smooth muscle, nerves
17
Q
What is serosa?
A
-Lubricating outer layer of connective tissue connected to mesentery
18
Q
How much salivary is produced by the salivary glands each day?
A
1.0-1.5
19
Q
What are the different types of salivary glands?
A
- Parotid salivary glands
- Sublingual salivary glands
- Submandibular salivary glands
20
Q
How much salivary is produced by Parotid salivary glands?
A
25%
21
Q
How much salivary is produced by sublingual salivary glands?
A
5%
22
Q
How much salivary is produced by submandibular salivary glands?
A
70%
23
Q
What are the four major roles of the salivary?
A
- Moisten and lubricates food = mucus
- Initiate digestion of polysaccharides (amylase) and lipids (lipase)
- Dissolve food
- Antibacterial actions
24
Q
What is a bolus?
A
Round mass of substances
25
What is bolus pushed into pharynx by?
Tongue
26
What is swelling reflex initiated by?
Pharyngeal stretchreceptors
27
What does the swelling reflex do?
- Ensures bolus does not enter nasal cavity or trachea
| - Voluntary initiation then unstoppable
28
How is the bolus move down the Oesophagus?
-Peristalticontraction of circular and longitudinal muscle layers
29
Where does the bolus move go after Oesophagus?
-Diaphragm into abdominal cavity
30
What are the major functions of the stomach?
- Storage of ingested food
- Mechanical breakdown of ingested food (chyme)
- Disruption of chemical bonds in food material by acid and enzymes
- Secretion (gastric juice)
31
What are the key regions of the stomach?
- Cardiac sphincter
- Cardia
- Fundus
- Body
- Antrum
- Pylorus sphincter
- Rugae
32
What is the does fungus act as?
Pacemaker cell
33
Where can you find oxyntic gland?
Body of stomach
34
What does the oxyntic gland release?
Stomach acids
35
Where can you find antrum gland?
Antrum
36
What does the antrum gland release?
Regulatory hormones influence gastric acid
37
What does the rugae allow?
Deep folds permits of 20-fold expansion in volume without increase in intragastric pressure
38
Where do you find gastric glands?
Gastric pits
39
What is gastrin?
Hormone that stimulates gastric acid secretion and motility and so is released into mucosal blood vessels
40
What do parietal cells release?
HCl acid
| Intrinsic factor
41
What do chief cell release?
Pepsinogen
42
What do G cells and D cells release?
Gastrin
| Somatostatin
43
What is the function of gastric acid?
- Kill ingested bacteria
- Denatures proteins
- Facilitates action of gastric lipase
- Converts pepsinogen to pepsin
44
What does the small intestine allow?
Continued digestion and absorption of nutrients
45
What % of nutrient absorption occurs in small intestine?
90%
46
Where does the main absorption occur in the small intestine?
Duodenum and jejunum
47
What are the three sections of the small intestine?
- Duodenum
- Jejunum
- Ileum
48
What are adaptions of the small intestine?
- Villi and microvilli
| - Brush border enzymes
49
What does villi and microvilli do?
Increase surface area of small intestine up to 600 times
50
What do brush border enzymes contribute to the small intestine?
- Cell membrane proteins within brush border microvilli of epithelial cells
- Digest CHOs and peptides in contact with brush border
- Complete the digestion process directly before absorption
51
What are the accessory organs of the GI tract?
Liver, Gall bladder and pancreas
52
What does prancrease secrete?
- Trypsin
- Lipase
- Amylase
- Ribonuclease
- Deoxyribonuclease
- Bicarbonate
53
What does the liver and gall bladder secretion?
Bile
54
What does bile contain?
- Bile salts
- Lecithin
- Bicarbonate ions
- Cholesterol
- Bile pigments
- Trace metals
55
What does bile aid?
Digestion and absorption of lipids
56
What two processes does bile aid?
- Emulsification
| - Formation of micelles
57
How are bile recycled back to the liver?
Hepatic portal system
58
What does the large intestine consist of?
- Colon
- Cecum
- Appendix
- Rectum
59
What is the function of large intestine?
- Reabsorption of water and some nutrients
| - Storage and compaction of faecal material prior to defecation
60
What is defecation reflex?
Mass movement of faeces, stretch of rectum, internal anal sphincter relax and contraction f rectum and sigmoid colon
61
What happens if external anal sphincter is relaxed?
Defecation occurs
62
Are there more or less bacteria in your gut than cells in your body?
More
63
How many different species of bacteria in you gut?
1000s
64
What are the functions gut microbiome?
- Metabolise, digest, fermet CHOSs and lipids
- Synthesis vitamins
- Protect the gut from invasion by pathogens and educate you immune system
65
What are the neuronal regulation that controls the digestive system?
- Intrinsic nerve plexuses
- Extrinsic nerves
- Smooth muscle 'pacemaker'
66
How does intrinsic nerve plexuses control the digestive system?
- Enteric nervous system
- Myenteric plexus = controls mainly smooth muscle contraction
- Submucosal plexus = controls mainly GI secretions and blood flow
67
How does extrinsic nerve control the digestive system?
-Parasympathetic and sympathetic influence on motility and secretion
68
How does smooth muscle pacemaker control the digestive system?
GI tract basic electrical rhythm generated by pacemaker cells within muscularis
69
What are the 3 phases of regulating gastric acid secretion and stomach emptying?
- Cephalic
- Gastric
- Intestinal
70
Give a summary of the cephalic phase:
- Initiated by smell/taste
- Mediated via enteric and parasympathetic nervous system
- Ghrelin
- Gastric secretion and motility
71
Give a summary of the gastric phase:
- Initiated in stomach
- Mediated via enteric and parasympathetic nervous systems and hormone gastrin
- Gastric secretions and motility
72
Give a summary of the intestinal phase:
Initiated in duodenum
- Mediated mainly by inhibitory hormones
- Slows gastric emptying to optimise digestion and absorption with small intestine
73
What is gherkin?
-Hunger hormone released from stomach and acts on hypothalamus to stimulate appetite, gastric secretion and motility
74
In the cephalic phase, what does the parasympathetic and submucosal plexus stimulate?
Mucus, pepsinogen and HCl production
75
In the gastric phase, what happens with the arrival of food?
- Increase in secretions and contractility
| - Histamine stimulates parietal cells to release more HCl in response to PNS and gastrin
76
What inhibits gastric acid secretion or gastric emptying?
- Cholecystokinin
- Secretin
- Somatostatin
- Leptin
77
What does cholecystokinin do?
Release by I cells in small intestine, stimulates pancreatic secretions and gall bladder contraction
78
What does secretin do?
Released by S cells in response to low pH, stimulates pancreatic and bile secretions
79
What does somatostatin do?
Released by D cells, inhibits everything
80
What does leptin do?
Released from adipose tissue and acts on hypothalamus to suppress appetite and regulate adipose tissue mass
81
What factors within duodenum that inhibit stomach motility and secretion?
- Duodenal distension
- Irritation of duodenum mucosa
- Increase in fats and proteins
- Increase in acidity
- Increase in osmolarity
82
How long does it take for transit though stomach?
1-4 hours
83
How long does it take for transit through small intestine?
3-5 hours
84
How long does it take for transit through large intestine?
30-50 hours
85
What is pernicious anaemia?
- Loss of parietal cells due to auto immune attach of stomach mucosa means no intrinsic factor and vitamin B12 deficiency
- Leads to life-threatening anaemia if not treated
86
What does an intrinsic factor form a complex with?
Vitamin B12
87
What is vitamin B12?
Large water soluble vitamin
88
What must vitamin B12 mind to?
An intrinsic factor
89
What is vitamin absorbed via?
Terminal ileum by endocytosis
90
How is gastric acid produced?
- CO2 + H20 --> H2CO3 catalysed by carbonic anhydrase in parietal cells
- H2CO3 dissociates to HCO3- and H+
- H+ enter gastric lumen via proton pump whilst K+ enters parietal cells
- Antiporters passivley transport HCO3- in exchange for Cl-
- K+ and Cl- passively transport into gastric lumen
- H+ and Cl- --> HCl
91
How is gastric acid production regulated?
- Vagus nerve = release acetylcholine to M3 receptor (more insertion of proton pumps of lumen membrane of parietal cells)
- Distention on G cell detected by buffer action (increase pH which increase gastric acid production)
- PNS releases gastrin releasing peptide binds to receptor on G cell to release gastrin into blood which passes to material cell binding to CCKB
- Gastrin released into blood also releases histamine from ECL cell which binds to H2 which enhance the effect of Act and gastrin
92
What protects the stomach mucosa from gastric acid?
Gastric mucosal barrier
93
When are mucosal cells replaced?
Every 3 days
94
What is the gastric mucosal barrier?
- Layer of bicarbonate-rich mucus
- Luminal membranes impermeable to H+ ion
- Tight junctions between mucosal cells
95
When can peptic ulcers arise?
- Stomach mucosal lining is broken
- Acid refluxes up into oesophagus
- Excess acid enters duodenum
96
What does treatment of peptic ulcers include?
- Antibiotics
- Proton pump inhibitors
- Selective H2 histamine receptor antagonists
97
Does gastrin increase or decrease HCL secretion?
Increase
98
Does histamine increase or decrease HCL secretion?
Increase
99
Does acetylcholine increase or decrease HCL secretion?
Neural
100
Does somatostatin increase or decrease HCL secretion?
Decrease
101
Does cholecystokinin increase or decrease HCL secretion?
Decrease
102
Rhythmic contraction of the smooth muscle layer within the GI tract wall
propels foodstuffs distally from the oesophagus through the intestines.
Which neural system normally regulates this form of motility within the
digestive system?
```
A.The central nervous system
B.The somatic nervous
system
C.The myenteric plexus
D.The parasympathetic
nervous system
E.The submucosal plexus
```
C
103
Which of the following hormone & gastric acid secretion states
(+ = increased, - = decreased) is typically seen during the cephalic
phase of gastric secretions?
```
A. +ghrelin, +gastrin,
+somatostatin,
+gastric acid
B. +ghrelin, -gastrin,
-somatostatin,
+gastric acid
C.+ghrelin, +gastrin,
-somatostatin,
+gastric acid
D.+ghrelin, -gastrin,
-somatostatin,
-gastric acid
```
C
104
```
Which of the following cells within
gastric pits release intrinsic factor?
A. Chief cells
B. Parietal cells
C. D cells
D. G cells
E. ECL cells
```
B
105
In relation to the control of gastric acid secretion, which of the following
statements is/are correct?
```
A. The proton pump secretes H+
ions across the basolateral
membrane of parietal cells
B. Histamine acts on H2 receptors
on chief cells to stimulate acid
release
C. Vagal nerve stimulation of
parietal cells leads to a decrease
in acid secretion
D. Endocrine stimulation of parietal
cells leads to acid secretion
E. Paracrine stimulation of parietal
cells leads to acid secretion
```
D and E
106
```
Which of the following
statements relating to gastric acid release are true?
A. Gastric acid is released in
response to protein arriving
within the stomach
B. Gastrin is an important
paracrine mediator of gastric
acid release
C. The parasympathetic nervous
system can increase gastric
acid release indirectly via
gastrin
D. H2 receptor agonists are
used as antacids in the
treatment of stomach ulcers
```
A and C
107
```
Which of the following statements
relating to gastric emptying is correct?
A. Gastric emptying is controlled
mainly by the autonomic
nervous system
B. An increase in osmolaritY within the duodenum speeds
up gastric emptying
C. Gastric emptying is controlled
mainly by the release of
gastrin and somatostatin from
the stomach mucosa
D.Gastric emptying is influenced
primarily by regulators
released from the duodenum,
which are mainly inhibitory
```
D
108
Which of the following statements is correct?
```
A. The gall bladder synthesises
and stores bile between
meals
B. The hormones secretin and
CCK promote pancreatic
secretions
C. Bile contains digestive
enzymes that target proteins,
fats and carbohydrates
D. Pancreatic and biliary
secretions are stimulated by
an increase in pH within the
duodenum
```
B
109
Enteropeptidase
facilitates the activation of which proteolytic enzymes
within the duodenum?
```
A. The activation of pepsin
from pepsinogen
B. The activation of trypsin
from trypsinogen
C. The activation of
chymotrypsin from
chymotrypsinogen
D. The activation of
carboxypeptidase from
procarboxypeptidase
E. All of the above
```
B, C and D
110
Which of the following statements relating to
absorption is correct?
A. Most nutrients are absorbed across the
membranes of GI epithelial cells by passive
transport down concentration gradients
B. Digestion by secreted enzymes alone is
normally sufficient to produce molecules
that are small enough to be absorbed
C. Lipids are absorbed from the GI lumen into
GI epithelial cells in the form of
chylomicrons
D. Amino acids rely on active secondary
transport to cross the intestinal epithelium
D
111
Which of the following types of motility is/are typically found
within the large intestine?
```
A. Peristalsis
B. Segmentation
C. Haustral contractions
D. Mass movements
E. All of the above
```
C and D
