GI Flashcards
(218 cards)
1
Q
How is swallowing initiated?
A
pressure receptors in the walls of the pharynx are stimulated by food, drink forced into the rear of the mouth by the tongue
2
Q
Which nerve innervates the nasopharynx?
A
Maxillary nerve (V2 (second branch of trigeminal nerve (V))
3
Q
Which nerve innervates the oropharynx?
A
The glossopharyngeal nerve (IX)
4
Q
Which nerve innervates the laryngopharynx?
A
Vagus nerve (X)
5
Q
Is stage 1 of swallowing voluntary or involuntary?
A
Voluntary.
6
Q
What happens in stage 1 of swallowing?
A
Food is compressed against the roof of the mouth and is pushed to the oropharynx by the tongue.
7
Q
Is stage 2 of swallowing voluntary or involuntary?
A
Involuntary.
8
Q
What happens in stage 2 of swallowing?
A
The nasopharynx closes off due to soft palate elevation. The trachea is closed off by the epiglottis. Elevation of the hyoid bone shortens and widens the pharynx.
9
Q
Is stage 3 of swallowing voluntary or involuntary?
A
Involuntary.
10
Q
What happens in stage 3 of swallowing?
A
The pharyngeal constrictor muscles sequentially contract producing peristaltic waves. This propels the bolus of food down the Oesophagus. This is followed by depression of the hyoid bone.
11
Q
Name 6 muscles/groups of muscles that are involved in swallowing.
A
- Buccinator.
- Suprahyoids.
- Muscles of the palate.
- Muscles of the floor of the mouth.
- Infrahyoids.
- Pharyngeal constrictor muscles.
12
Q
Which muscle(s) manipulate food in chewing. Elevate the hyoid bone and flatten the floor of the mouth?
A
Buccinator and Suprahyoids.
13
Q
What is the function of the muscles of the soft palate in swallowing?
A
They act to tense and elevate the soft palate.
14
Q
What is the function of the muscles of the floor of the mouth in swallowing?
A
They raise the hyoid bone and larynx.
15
Q
What is the function of the infrahyoid?
A
To depress the hyoid bone and larynx.
16
Q
What is the function of the pharyngeal constrictor muscles?
A
They contract sequentially producing peristaltic waves which drive food into the oesophagus.
17
Q
What is the pathway of the gag reflex?
A
- irritation of the oropharynx causes a reflex arc between the glossopharyngeal (IX) and the vagus (X) nerves
18
Q
What is the function of saliva?
A
- lubricant for mastication
- maintains oral pH through the bicarbonate buffer system (pH7.4)
- releases digestive enzymes ( alpha-amylase)
- Has a role in immunity through washing food particles which may have been used by bacteria for metabolic support
19
Q
How much saliva on average is secreted in adults?
A
800-1500ml
20
Q
What is the pH range of saliva
A
6.2-7.4
21
Q
Name 4 factors that can affect the composition of saliva.
A
- Stimulus.
- Age.
- Gender.
- Drugs.
5 flow rate
22
Q
Do parotid glands have mainly serous or mainly mucous acini?
A
Mainly serous acini.
23
Q
Do sublingual glands have mainly serous or mainly mucous acini?
A
Mainly mucous acini.
24
Q
Do submandibular glands have mainly serous or mainly mucous acini?
A
They have serous and mucus acini.
25
What is serous acini secretion composed of?
alpha amylase - this is needed for starch digestion.
26
What is mucous acini secretion composed of?
Mucin - needed for lubrication.
27
Do minor glands have mainly serous or mucous secretions
predominantly mucous, but some are serous like Von Ebner's gland under the circumvallate papillae
28
give the three ways defence is provided for the oral cavity?
- Mucosa: a physical barrier
- Salivary glands: washes away food particles that may be used by pathogens for metabolic support
- Palatine tonsils act as the surveillance system for the immune system
29
Which salivary glands are continuously active?
Submandibular, sublingual & minor glands
30
Which salivary gland becomes the main source of saliva when stimulated?
Parotid gland
31
Describe the appearance of serous acini
- Dark staining
| - small central duct
32
Describe the appearance of mucous acini
- Pale staining 'foamy' appearance
| - large central duct
33
What is the epithelium lining of intercalated ducts?
Simple cuboidal epithelium.
34
What is the function of intercalated ducts?
They connect acini to larger striated ducts.
35
What are interlobular ducts split into?
- intercalated duct cells
| - striated duct cells
36
What is the importance of the striated duct basal membrane being highly folded?
It is folded into microvilli for the active transport of HCO3- against its concentration gradient.
37
Which organelle is present in high concentration in the microvilli of the striated duct cells?
mitochondria - for active transport energy
38
Name 2 ions that striated ducts secrete.
K+ and HCO3-
39
Name 2 ions that striated ducts reabsorb.
Na+ and Cl-
40
Is saliva hypotonic or hypertonic?
Hypotonic - water reabsorption and ion secretion.
41
what proportion of salivary flow do the minor glands account for?
20%
42
Where might we find minor glands?
lips, cheeks, hard and soft palate and the tongue
43
where does the parotid duct drain in the oral cavity?
adjacent to the second upper molar
44
What is the sympathetic sensory innervation of the parotid gland?
Mandibular branch of the trigeminal nerve V3
45
What is the parasympathetic innervation of parotid gland?
glossopharyngeal nerve (IX) -stimulates secretion
46
Name three structures passing through the parotid gland?
- External carotid artery
- Retromandibular vein
- Facial nerve (VII - exits the skull through the
stylomastoid foramen) - supplies the muscles of
facial expression
47
Where does the submandibular gland (Wharton's duct) empty in the oral cavity?
- In the floor of the mouth
| - empties at the sublingual papillae
48
What is the parasympathetic innervation of the submandibular gland
```
chorda tympani branch of the
facial nerve (VII)
```
49
What is the sympathetic innervation of the submandibular gland?
```
lingual nerve which is derived from the
facial nerve (VII)
```
50
Which is the smallest pair of salivary glands
sublingual glands
51
Which duct do the sublingual glands use to enter the oral cavity?
- Submandibular duct (Wharton's duct)
52
What is the parasympathetic innervation of the sublingual gland
```
chorda tympani branch of the
facial nerve (VII)
```
53
What is the sympathetic innervation of the submandibular gland?
```
lingual nerve which is derived from the
facial nerve (VII)
```
54
Do minor salivary glands have branching networks of draining ducts?
No, they each have their own simple duct
55
What do mucous cells in the stomach secrete
alkaline mucous - protective mechanism
56
What do parietal cells secrete?
gastric acid (HCI) and intrinsic factor
57
what do chief cells secrete?
pepsinogen
58
What do enterochromaffin-like (ECL) cells secrete?
Histamine
59
What do G cells secrete?
Gastrin
60
What do D cells secrete?
Somatostatin
61
Describe the stomach's epithelial layer
Epithelial layer invaginates the mucosa - forming tubular glands
62
Which cells are most abundant in the upper part of the stomach?
- parietal cells
- chief cells
- mucous cells
63
Which cells are most abundant in the lower part of the stomach close to the antrum?
G cells which secrete gastrin
64
describe how parietal cells secrete gastric acid
- origin of H+ is CO2
- CO2 and H2O from respiration are converted into carbonic acid (H2CO3) via enzyme carbonic anhydrase
- Dissociates and produces H+ and HCO3-
- H+ pumped into lumen using H+/K+ ATPase pumps on the luminal surface
- K+ diffuse back into stomach lumen via K+ channels
- THe bicarbonate is secreted into capillary for exchange with Cl-
- Cl- can then enter the stomach by diffusing through cl- channels
- combines with H+ to form HCI
65
What ions are exchanged on the side of the parietal cell in contact with the capillaries?
Cl- is pumped into the parietal cell and HCO3- moves out of the parietal cell into the capillary.
66
On average, how much gastric acid do we secrete a day?
2L
67
What are the 4 phases important in regulating gastric acid secretion? Do these phases turn secretion on or off?
1. Cephalic phase - turning ON.
2. Gastric phase - turning ON.
3. Gastric phase - turning OFF.
4. Intestinal phase - turning OFF.
68
What happens during the cephalic phase?
- Initiated by the sight, smell, taste of food and chewing
- Acetyl choline is released
- ACh acts indirectly on parietal cells, triggering the release of GASTRIN and indirect release of histamine
- Both gastrin & histamine increase the number of H+/K+-ATPase pumps on the
the plasma membrane of the parietal cell
- Net effect = increased acid production
69
What occurs in the gastric ON phase?
- once food has reached the stomach
- initiated by gastric distention and presence of amino acids and peptides
- gastrin released - indirect release of histamine
- both act on parietal cells
- both increase the number of H+/K+-ATPase pumps on the
the plasma membrane of the parietal cells.
- Net effect = increased acid production
70
What occurs in the Gastric OFF phase?
- low luminal pH directly inhibits gastrin release and therefore histamine too.
- Low pH results in somatostatin release, inhibits parietal cell activity
-
71
How does the presence of proteins lead to increased acid production in the stomach?
- Protein direct stimulus for gastrin release
- reducing the amount of H+
- increased pH results In less somatostatin secretion
- more parietal cells activity
72
What occurs in the intestinal phase?
- occurs in the duodenum
- Initiated by; duodenal distension, low pH, hypertonic solutions, the presence of
amino acids & fatty acids
- trigger release of enterogastrones, Secretin and CCK
- both inhibit gastrin release and promote somatostatin release
- also trigger short and long neural pathways which reduce Ach release
- reduced acid secretion
73
Which parasympathetic neurotransmitter is involved in the regulation of gastric acid secretion?
Ach (+)
74
Which hormone is involved in the regulation of gastric acid secretion?
gastrin (+)
75
Which paracrine molecules are involved in the regulation of gastric acid secretion?
histamine (+) & somatostatin (-)
76
Which enterogastrones are involved in the regulation of gastric acid secretion?
secretin (-) &
| CCK (-)
77
Define ulcer
An ulcer is a breach in a mucosal surface
78
Name 3 things that can cause peptic ulcers.
1. Helicobacter pylori.
2. NSAIDs.
3. Chemical irritants e.g bile salts and alcohol
79
describe how Helicobacter pylori can cause peptic ulcers
- lives in gastric mucus
- secretes urease
- splits urea into ammonia and CO2
- ammonia + H+ = ammonium
- ammonium is toxic to the gastric mucosa and less mucous is produced
- proteases and phospholipase can attack the gastric epithelium
- results in inflammatory response
80
describe how NSAIDs can cause peptic ulcers
- Mucus requires prostaglandins for production
- Cyclo-oxygenase 1 is needed for prostaglandin synthesis.
- NSAIDs inhibit COX-1
- reduced mucosal defence
81
How can chemical irritants cause peptic ulcers?
They wash away the alkaline mucus resulting in reduced protection
82
Name 2 drugs that can be used to reduce gastric acid secretion.
1. Proton pump inhibitors.
| 2. H2 receptor antagonists.
83
Name 4 protective mechanisms of gastric mucosa
* Alkaline mucus on the luminal surface
* Tight junctions between epithelial cells
* Replacement of damaged cells - stem cells at the base of pits to produce new cells
* Feedback loops
84
What is the precursor molecule for pepsin?
pepsinogen
85
What activates pepsinogen?
Low pH.
86
which neurotransmitter mediates the release of pepsinogen?
Ach - via enteric nervous systems
87
describe how pepsinogen is activated?
- Initially gastric acid cleaves pepsinogen into pepsin
- when pepsin has been made the pepsin itself can cleave pepsinogen into pepsin
- positive feedback loop
88
What can be released in the duodenum to irreversibly inactivate pepsin?
HCO3-
89
What enzyme is responsible for protein digestion in the stomach?
Pepsin.
90
What enzymes are responsible for protein digestion in the small intestine?
Pancreatic proteases.
91
What are the 2 types of pancreatic proteases?
1. Endopeptidases.
| 2. Exopeptidases.
92
Give 2 examples of an endopeptidase.
1. Trypsin.
| 2. Chymotrypsin.
93
Give 2 examples of an exopeptidase.
1. Carboxypeptidases.
| 2. Aminopeptidases.
94
What is the function of endopeptidases?
They break peptide bonds between non-terminal amino acids.
95
What is the function of exopeptidases?
They break peptide bonds between terminal amino acids and so form monomers.
96
Which type of pancreatic protease can form monomers?
Exopeptidases.
97
what is the volume of an empty stomach and a full stomach?
empty: 50ml
full: 1.5 litres with little increase in luminal pressure
98
What is receptive relaxation?
Smooth muscle in the body and fundus of the stomach relaxes prior to the arrival of food, this allows the stomach volume to increase. There is afferent input from Cn 10. NO and serotonin also influence relaxation.
99
Where do peristaltic waves begin?
gastric body
100
Where in the stomach are peristaltic contractions the most powerful?
gastric antrum
101
Why is the pyloric sphincter closed as the peristaltic wave reaches it?
This prevents chyme entering the duodenum and so the gastric contents are forced back and mixed together in the body of the stomach.
102
On average, how many peristaltic waves are there a minute?
3 (slow repol/depol cycles).
103
which cells are responsible for determining the frequency of peristaltic waves?
Interstitial cells of Cajal in the muscular propria - longitudinal muscle layer
104
How can the threshold potential become easier to reach for the interstitial cells of Cajal?
The threshold potential can be altered by the enteric nervous system
105
Name 2 factors that can increase the strength of peristaltic contractions.
1. Gastrin.
| 2. Gastric distension.
106
Name 5 factors that can decrease the strength of peristaltic contractions.
1. Duodenal distension.
2. Low pH in duodenum lumen.
3. Increased duodenal osmolarity.
4. Increased sympathetic action.
5. Decreased parasympathetic action.
107
which part of the small intestine absorbs the most amount of water?
jejunum
108
what proportion of total water is reabsorbed?
98%
| 2% excreted in stools
109
how is water reabsorbed in the small intestine?
- epithelial membrane of small intestine is very permeable to water
- Na+ ( most abundant ion in chyme) is actively transported from lumen into cells
- lowers water potential
- water enters cells
110
Where does Cl- and HCO3- reabsorption mainly take place?
In the ileum and colon.
111
What is the mechanism for Cl- and HCO3- reabsorption?
Cl- is actively reabsorbed in exchange for HCO3-. The intestinal contents, therefore, become more alkaline.
112
How is potassium reabsorbed?
through passive diffusion
113
Briefly describe how lipids are absorbed?
- mechanical disruption of large droplets
- emulsifying agent from phospholipids and bile salts
- prevents reaggregation of large droplets
- pancreas secretes colipase
- holds lipase on the surface of the droplet
- Further bile salts convert into micelles
- in the small intestine - the resynthesis of TG at SER
- processed in Golgi to form chylomicrons
- exocytosis into the interstitial fluid
- then enter the lacteals - lymphatic vessels
- chylomicrons can also contain fat-soluble vitamins cholesterol and phospholipids
114
How are chylomicrons formed?
Triglycerides, phospholipids and cholesterol combine with proteins inside the epithelial cell forming chylomicrons.
115
What is the function of mixed micelles?
Lipid transport systems.
116
The end products of fat digestion combine with bile salts and cholesterol to form what?
Mixed micelles.
117
What protein binds pancreatic lipase to the surface of the lipid?
Co-lipase. This is essential, pancreatic lipase can not work without it.
118
What digests lipids in the small intestine?
Pancreatic lipases.
119
What is the advantage of emulsifying lipids?
It increases the SA for digestion and so digestion is more efficient.
120
What emulsifies lipids?
Bile salts.
121
Where are fat-soluble vitamins absorbed?
ileum
122
Where are water-soluble vitamins absorbed
jejunum with B12 as the exception
123
How is vitamin B12 absorbed?
It binds to a protein, intrinsic factor. It is then absorbed in the terminal ileum via endocytosis.
124
what is vitamin b12 needed for?
DNA synthesis therefore erythrocyte formation
125
Is vitamin A fat or water soluble?
fat soluble
126
What are the functions of vitamin A?
Vitamin A is needed for cellular growth and differentiation. It is also important for eyesight and lymphocyte production.
127
Name 3 sources of vitamin A.
1. Oily fish.
2. Dairy.
3. Liver
128
Is vitamin C fat or water soluble?
Water soluble
129
What are the functions of vitamin C?
Synthesis of collagen, neurotransmitters and carnitine. It has an antioxidant ability and can absorb non-haem iron.
130
Name 4 sources of vitamin C.
1. Citrus fruits.
2. Green leafy veg.
3. Potatoes.
4. Kidney.
131
Are B vitamins fat or water soluble?
Water soluble.
132
What are B vitamins important for?
Cell metabolism and energy production.
133
what do we mean by 'essential amino acids?
We cannot manufacture them
134
What are proteins digested into?
Dipeptides, tripeptides and amino acids.
135
What is the optimum pH for pepsin action?
1.6 - 3.2
136
What does pepsin break proteins into?
Peptide fragments.
137
By what process are the products of protein digestion absorbed into the intestinal epithelial cells?
Secondary active transport coupled to H+ or Na+.
138
What are the end products of starch digestion?
Maltose!
| Also maltotriose, glucose polymers and alpha-dextrins.
139
What enzyme digests starch in the small intestine?
Pancreatic amylase.
140
Where is the first site of starch digestion?
In the mouth via salivary amylase.
141
Briefly describe starch digestion.
Begins in the mouth via salivary amylase. In the small intestine pancreatic amylases catalyse alpha 1-4 linkages forming maltose. The end products are further broken down by enzymes e.g. maltase on the luminal membrane; this forms monosaccharides. The products diffuse into the cell
through sodium-glucose co-transporter
facilitated diffusion into the blood on basolateral surface
142
what is the optimal pH for salivary amylase?
6.7
143
How long do glycogen stores in a 70Kg adult last?
About 12 hours.
144
How long do lipid stores in a 70Kg adult last?
3 months.
145
Define BMR.
The energy needed to stay alive at rest, usually 24kcal/kg/day.
146
Where is Vit A stored?
in ito cells in the space of Disse in the liver
147
What are the consequences of vitamin A deficiency?
Night blindness, growth retardation, increased susceptibility to infection.
148
What are the consequences of vitamin C deficiency?
Weakness, shortness of breath, aching, bleeding gums, thickening of skin.
149
What is the role of Vit D?
intestinal Ca2+ absorption
150
What is the role of Vit E
Antioxidant
151
Where does the foregut begin and end?
Mouth to the major duodenal papilla. (In the embryo - oropharyngeal membrane to the liver bud).
152
Where does the midgut begin and end?
Major duodenal papilla to 2/3 along the TC. (In embryo - liver bud to 2/3 along TC).
153
Where does the hindgut begin and end?
Distal 1/3 of TC to anal canal. (In embryo - distal 1/3 of TC to cloacal membrane).
154
Why are the foregut, midgut and hindgut divisions different in the adult compared to in the embryo?
It changes due to the formation of the ampulla of vater.
155
Why is the stomach the shape it is?
Due to differences in growth rates. The greater curvature grows faster than the lesser curvature.
156
Why does the left vagus nerve become the anterior vagal trunk and the right vagus become the posterior vagal trunk?
Due to the 90 degrees clockwise rotation of the stomach in its longitudinal axis.
157
What does the dorsal mesentery become?
The greater omentum.
158
What does the ventral mesentery become?
The lesser omentum.
159
What are the 5 stages of midgut development?
1. Elongation.
2. Herniation.
3. Rotation.
4. Retraction.
5. Fixation.
160
What connects the midgut to the yolk sac?
The Vitelline duct.
161
What happens in the elongation stage of midgut development?
Rapid elongation forms the primary intestinal loop. The proximal part of the loop forms the small intestine and the distal part forms the large intestine up to 2/3 TC.
162
What happens in the herniation stage of midgut development?
The rapid growth of the intestinal loop means it is pushed into the extra embryonic cavity in the umbilical cord.
163
What happens in the rotation stage of midgut development?
The elongated intestinal loop rotates 270 degrees anticlockwise.
164
What happens in the retraction stage of midgut development?
In the 10th week the herniated midgut returns into the expanded abdominal cavity. Th jejunum is first to return.
165
What happens in fixation of midgut organs?
This is when some regions of the gut lose their dorsal mesentery. These regions become retroperitoneal.
166
What are the 4 layers of the GI tract?
1. An innermost mucosa.
2. A sub-mucosa.
3. An external muscle coat (muscularis externa)
4. A serosa.
167
What is the innermost mucosa layer composed of?
- A folded epithelium.
- Lamina propria (connective tissue).
- Muscularis mucosa (ring of smooth muscle).
168
What is the submucosa layer composed of?
Loose connective tissue containing glands and lymph tissue. Many blood vessels and a rich plexus of nerves that is part of the enteric nervous system (Meissner's plexus) are also found in the submucosa.
169
What is the muscular externa composed of? What is its function?
Composed of 2 layers of smooth muscle: circular and longitudinal. Nerves that are part of the enteric nerve plexus are also present here (Aurebach's plexus). Contraction of the muscle helps to break down and food and propel it along the GI tract.
170
What is the serous layer composed of?
Composed of a simple squamous epithelium that covers the outside surface of the gut tube facing the peritoneal cavity.
171
What enzyme are parietal cells abundant in?
Carbonic anhydrase.
172
Give 5 functions of hepatocytes.
1. Creation and storage of energy in the form of glycogen.
2. Synthesise and secrete plasma proteins.
3. Remove amino groups from amino acids for the production of urea. (Deamination).
4. Uptake, synthesis and excretion of bilirubin and bile acids.
5. Detoxification and inactivation of drugs and toxins.
173
What are the 2 key stages for fat digestion?
1. Emulsification.
| 2. Triglyceride hydrolysis.
174
Where in the layers of the GI tract would Meissner's plexus be found?
In the submucosa.
175
Where in the layers of the GI tract would Auerbach's plexus be found?
In the muscularis externa between the circular and longitudinal layers of muscle.
176
Name the abdominal retroperitoneal organs.
Supradrenal glands, Aorta, IVC, Duodenum (except cap), Pancreas (except tail), Ureters, Colon (ascending and descending), Kidneys, Oesophagus, Rectum.
177
Name the abdominal intraperitoneal organs.
Spleen, Small intestine, Appendix, Liver, Transverse colon, Stomach, Sigmoid colon.
178
What is the arcuate line?
The lower limit of the posterior rectus sheath.
179
What happens to the posterior rectus sheath below the arcuate line?
It is absent. The rectus abdominis is in direct contact with the transversalis fascia.
180
What envelopes the rectus abdominis above the arcuate lin
It is enveloped by the internal oblique aponeurosis.
181
What is the anterior layer of rectus sheath formed from?
External oblique aponeurosis and the anterior lamina of the internal oblique aponeurosis.
182
What is the posterior layer of the rectus sheath formed from?
The posterior lamina of the internal oblique aponeurosis and the transversus abdominis aponeurosis.
183
What forms the anterior rectus sheath below the rectus abdominis?
The external oblique, internal oblique and transversus abdominis aponeurosis' all form the anterior rectus sheath. There is no posterior rectus sheath.
184
What vertebral level does the umbilicus mark when lying down?
L3.
185
What abdominal plane would you refer to when carrying out a lumbar puncture?
The intercristal plane. It joins the highest points of the pelvis posteriorly and marks the space between L4 and L5.
186
Describe 2 ways in which the transpyloric plane can be drawn.
1. The midpoint between the suprasternal notch and the pubic symphysis.
2. Connects the two points marked by the insertion of the rectus sheath into the costal margin.
187
Name 3 structures that cross the transpyloric plane.
1. The pylorus of the stomach.
2. The gall bladder.
3. The pancreas.
188
At what vertebral level is the transpyloric plane?
L1
189
What is the intercristal plane?
It connects the highest points of the pelvis at the lower back.
190
At what vertebral level is the intercristal plane?
L4/5.
191
What is the intertubercular plane?
A line that joins the tubercles of the iliac crests.
192
At what vertebral level is the intertubercular plane?
L4.
193
What is the subcostal plane?
A plane parallel to the lowest points of the costal margins.
194
At what vertebral level is the subcostal plane
L2
195
Where is the swallowing centre found?
Medulla
196
Give 3 functions of HCl in the stomach.
1. Solubilisation of food particles.
2. Kills microbes.
3. Activates pepsinogen forming pepsin.
197
What type of cells are secretin and CCK?
enterogastrones
198
Chief cells secrete pepsinogen and and an enzyme. What is the enzyme?
gastric lipase
199
What mechanism speeds up the digestion of fats?
Emulsification - the surface area for lipase action is increased.
200
Name 4 molecules to make up micelles.
1. Fatty acids.
2. Monoglycerides.
3. Bile salts.
4. Phospholipids.
201
Which molecule is produced that aids absorption of lipids into cells?
miscelles
202
What is the function of micelles?
They are lipid transport systems. They move to the epithelial brush border and release the fatty acids and monoglycerides for absorption.
--
203
What happens to the fatty acids and monoglycerides inside the intestinal epithelial cells?
They are re-synthesised into triglycerides in the smooth ER.
204
Why are fatty acids and monoglycerides re-synthesised into triglycerides inside the intestinal epithelial cells?
To maintain the concentration gradient for further absorption of fatty acids and monoglycerides.
205
Inside the intestinal epithelial cell, triglycerides combine with other lipids e.g. cholesterol to form what molecules?
Chylomicrons.
206
What are the functions of chylomicrons?
Chylomicrons move through the lymphatics and the blood stream to tissues.
207
What can cause pernicious anaemia?
If you have low levels of intrinsic factor you will have B12 deficiency. This will mean fewer RBC's will be formed leading to pernicious anaemia.
208
What can cause Barrett's oesophagus?
GORD
209
Describe Barrett's oesophagus.
When the stratified squamous oesophageal epithelium changes to a simple columnar one at the lower end of the oesophagus. This can be caused by prolonged acid reflux from the stomach.
210
What is the function of the Vagus nerve in regards to parietal cells?
The vagus nerve stimulates the release of Ach which then acts on the parietal cells to increase HCl production.
211
Name 3 organs that secrete digestive enzymes.
1. Stomach.
2. Pancreas.
3. Salivary glands.
212
What structure, visible microscopically, is primarily responsible for absorption?
Villi.
213
Name 3 physical mechanisms of absorption.
1. Endocytosis.
2. Diffusion/facilitated diffusion.
3. Active transport.
214
Name 2 diseases that can cause malabsorption.
1. Crohn's disease - loss of plicae circulares.
| 2. Coeliac disease - vili atrophy.
215
What muscles contributes to the upper oesophageal sphincter?
Cricopharyngeus.
216
Where are the stem cells that replace the epithelium located?
The base of crypts.
217
Which papillae do not bear taste buds?
Filiform papillae.
218
Does the oesophagus have a serosa layer?
No!
