Gastrointestinal Science Flashcards
(316 cards)
1
Q
Name the two directions of food movement in the GI tract.
A
Aboral (oral to anal) and oral (anal to oral)
2
Q
Name the organs of the alimentary tract and the accessory GI organs.
A
Tongue, pharynx, oesophagus, stomach, liver, gall bladder, pancreas, duodenum, jejunum, ileum, caecum, colon, appendix, rectum, anus, salivary glands, biliary tree
3
Q
What is the purpose of the mouth and oropharynx?
A
Chops and lubricates food, and begins digestion of carbohydrates
4
Q
What are the two main purposes of the stomach?
A
Physical and chemical digestion
5
Q
Describe the makeup of the small intestine.
A
Duodenum, jejunum, ileum. Connects by the caecum
6
Q
Describe the makeup of the large intestine.
A
Connects by caecum. Then appendix, colon
7
Q
Name the two components of the rectum and describe the purpose of the rectum and anus.
A
Sigmoid and descending.
Regulates expulsion of faeces
8
Q
What are the accessory structures of the GI tract?
A
Liver, gallbladder, salivary glands, pancreas
9
Q
Name the histological layers of the GI tract.
A
Mucosa (epithelium (NOT endo), lamina propria), submucosa, muscularis externa (circular and longitudinal muscle)
10
Q
Name the two nerve plexuses of the GI tract. Where are they located?
A
Submucous (submucosal), myenteric (muscularis externa)
11
Q
What are the four functions of the GI tract?
A
Motility (movement), secretion, digestion, absorption
12
Q
Describe the muscle makeup of the alimentary tract.
A
Smooth muscle except at the extreme ends of the tract (oral and anal) where it is skeletal
13
Q
Describe how muscle in the GI tract allows motility.
A
By circular muscle (makes lumen longer/narrower), longitudinal (shorter/fatter), very outer musclaris externa (change in absorptive area, mixing)
14
Q
What is the name of food when it reaches the duodenum?
A
Chyme
15
Q
What is the name of the pacemaker cells of the alimentary canal?
A
Interstital cells of Cajal
16
Q
Which cellular component allows spread of action potential in the gut?
A
Gap junctions
17
Q
Describe how an action potential is created in the gut.
A
‘Slow waves’ are constantly being created by pacemaker cells. When they reach above the membrane potential threshold they fire calcium APs
18
Q
Describe the effect of prolonged firing of APs.
A
Greater force, which means greater muscle tension
19
Q
Which stimuli increase the ‘resting potential’ of ICC action potentials, making it more likely for the threshold to be reached?
A
Neuronal, hormonal, mechanical
20
Q
Describe the parasympathetic supply of the gut.
A
Vagus nerve, and sacral nerves S2 - S4
21
Q
Describe the effects of parasympathetic and sympathetic supply to the alimentary tract.
A
Parasympathetic - increases digestion/secretion, relaxes sphincters/stomach.
Sympathetic - increases sphincter tone, decreases blood flow/secretion
22
Q
What are the main purposes of the GI plexuses?
A
Myenteric - motility and sphincter control
Submucous - epithelium, blood vessels
23
Q
Name the three components of GI reflex circuits.
A
Sensory, interneurons, effectors
24
Q
Name the three types of GI reflex circuit.
A
Local, short, long
25
What is the name of a reflex which takes place entirely within the vagus nerve?
Vaso-vagal
26
What is glycogenesis?
Formation of glycogen
27
What is glycogenolysis?
Splitting of glycogen to form glucose
28
What is gluconeogenesis?
Formation of glucose from amino acid, glycerol, or lactic acid precursors
29
Describe the difference between glycogen stored in the liver and muscle cells.
In the liver it is used to regulate blood sugar. In muscle it is not available to the blood stream, just for glycolysis
30
Name and describe the two types of link in glycogen.
Alpha 1-4 glycosidic = straight chain
| Alpha 1-6 glycosidic = branches
31
Which enzyme attaches primers to glucose residues for binding to glycogen?
Glycogenin
32
Name the intermediates of the metabolic pathway for glycogenesis.
G6P, G1P, UDP-glucose, [glucose]n+1
33
Name the three main enzymes in glycogenesis.
Glucophosphomutase, UTP-glucose phosphorylase, glycogen synthase
34
Name the main enzyme in glycogenolysis.
Glycogen phosphorylase (although many other enzymes are required to debranch glycogen)
35
Name the three main enzymes in gluconeogenesis, and which reactions they catalyse.
Phosphenol pyruvate carboxy kinase (PEPCK); pyruvate -> phosphenol pyruvate
Fructose-1,6-phosphatase (F1,6bP -> F6P)
Glucose-6-phosphatase (G6P -> glucose)
36
Which enzymes do the gluconeogenesis enzymes bypass?
Pyruvate kinase, phosphofructokinase, hexokinase
37
What is the name of the cycle which converts muscle lactic acid back to glucose?
Cori cycle
38
Why is fat an essential energy source?
Stores lots of energy, provides essential fatty acids, and for fat-soluble vitamins (A, D, E, K)
39
What is an essential fatty acid?
One the body needs but cannot synthesise
40
What are the chemical properties of lipids, TAGs, and fatty acids?
Non-polar, usually straight chain, usually cis, compact, alipathic (doesn't form rings)
41
Name the three main fatty acids and their configuration.
Palmitic acid (16:0), Stearic acid (18:0), Oleic acid (18:1)
42
What are the alpha, beta, and omega carbons of fatty acids?
Alpha - adjacent to the carbon of the carboxyl group
Beta - adjacent to alpha
Omega - furthest from carboxyl group
43
Describe the process by which fat is absorbed into the mucosa.
TAGs degraded by lipases to fatty acids. These bind with monoacylglycerols, crossing the membrane to form TAGs again. These bind with other lipids/proteins to form chylomicrons
44
Describe the first stage of energy release from fatty acids (i.e. cytoplasmic).
Fatty acid + CoA -> acyl-CoA.
Acyl-CoA + carnatine -> acyl-carnatine + CoA
Acyl-carnatine crosses the mitochondrial matrix
45
Describe the second stage of energy release from fatty acids (i.e. mitochondrial matrix).
Acyl-carnatine + CoA -> acyl-CoA + carnatine
| Acyl-CoA -> acetyl-CoA, FADH2, NADH, shortened acyl-CoA
46
Name the process by which acyl-CoA is transported into the mitochondrial matrix.
The carnatine shuttle
47
By which process is acyl-CoA broken down in the mitochondrial matrix?
Beta oxidation
48
What is the main purpose of ketones in respiration?
Can be converted to acetyl-CoA in starvation/diabetes
49
What are the clinical signs of ketone use in respiration?
Severe acidosis, breath smells of acetone
50
How are fatty acids created from acetyl-CoA?
Citrate transports to cytoplasm. Acetyl-CoA carboxylase converts to malonyl-CoA. This, plus NADH and fatty acid synthase creates fatty acids.
51
Which two substances promote acetyl-CoA carboxylase?
Insulin and citrate
52
Which three substances inhibit acetyl-CoA carboxylase?
Glucagon, adrenaline, palmitoyl-CoA
53
Under which conditions is lipogenesis most likely to occur?
The fed state, with a supply of carbohydrates, energy, and citrate
54
How are excess fatty acids stored?
In adipose, by VLDL
55
Why are amino acids that are not in use degraded?
There is no way to store them
56
Where in the GI tract are proteins degraded, how, and what into?
Stomach - proteolytic enzymes, and single amino acids or di-/tripeptides
57
When may degradation of proteins pose a problem to the liver?
High concentrations of nitrogen in side groups - NH4+/NH3 is toxic
58
Describe the transamination stage of amino acid catabolism.
An alpha-amino acid transfers the alpha-group to ketoglutarate, forming an alpha-keto acid. Also formed is glutamic acid
59
How is glutamic acid (the product of deamination) tranferred to the liver?
As alanine (w/ pyruvate) or glutamine (with NH4+)
60
Describe the de-amination step of amino acid catabolism.
Glutamate breaks off NH4+ (NAD accepting an electron to become NADH). A ketoglutarate is also formed
61
Describe the reactants and products of the urea cycle.
Reactants - NH4+, aspartic acid, ATP
| Products - urea, fumerate, carbon skeletons
62
Describe how carbon skeletons of the urea cycle may be used.
Ketogenic - forms acetyl-CoA or fatty acids
| Glucogenic - forms pyruvate or glucose
63
What is the name of the condition that blocks degradation of phenylalanine and tyrosine?
Alcaptonuria
64
Describe maple syrup urine disease.
Urine smells of maple syrup. Blocks valine, isoleucine, and leucine. Treated by diet, otherwise mental/physical retardation occurs
65
Describe phenylketouria.
Buildup of phenylalanine. Can cause severe mental retardation. Limit phenylalanine in the diet
66
How may a urea cycle defect be treated?
Drugs that remove nitrogen, gene therapy, low protein diet
67
What is the epithelium of the oral cavity and oropharynx?
Stratified squamous
68
What is the epithelium of the nasal cavity and nasopharynx?
Respiratory - keratinized pseudostratified columnar
69
Name the four papillae of the tongue.
Fungiform, circumvallate, foliale, filiform
70
Name the main feature of the posterior 1/3 of the tongue.
Associated with lymphoid aggregates
71
Name the four tonsils.
Palatine, lingual, tubual, pharyngeal
72
Name the three areas of the stomach.
Cardia, body, pylorus
73
Describe the difference between the epithelium of the isthmus and fundus of the stomach.
Isthmus mostly parietal cells
| Fundus mostly chief cells
74
Describe the gastric pits of the cardia, fundus, and pylorus.
Cardia - deep, loose, tortous
Fundus, shallow, straight, long
Pylorus - deep, branched, coiled, high density
75
Describe how the pyloric sphincter differs from the pylorus.
More smooth muscle
76
Describe the two main features of the small intestine's epithelium.
Microvili, crypts of Lieberkuhn
77
Where are Brunner's glands, and what do they do?
Duodenum. Protect duodenum from gastric juices and neutralise chyme
78
What are Peyer's patches?
Gut-associated lymphoid tissue (GALT)
79
Name two unique cells found in the crypts of Lieberkuhn.
Paneth cells - immune role
| Stem cells - replenish the epithelium
80
Name the five main type of cell found in the small intestine.
Enterocyte, enteroendocrine, goblet, Paneth, stem
81
What two main types of cell are found in the colon?
Absorptive and goblet (lubricates)
82
Describe the smooth muscle alignment in the colon.
Not continuous - three strips teniae coli
83
How does the appendix's histology differ from the colon?
Fewer crypts. Circular lymphoid tissue
84
Describe the epithelium of the anal canal.
Non-keratinized stratified squamous (becomes keratinized after the anus)
85
What is the main endothelium of the liver?
Simple squamous, fenestrated
86
Name the main components of the hepatic lobules.
Portal tracts/triads, sinusoids, space of Disse, Kupffer cells, hepatocytes, hepatic stellate cells
87
Describe the composition of the portal tract/triad.
Hepatic artery, portal vein, and bile duct
88
What is the purpose of hepatic stellate cells?
Makes connective tissue and stores vitamin A
89
What are Kupffer cells?
Macrophages in the liver
90
Describe the composition of bile.
Bilrubin (pigment of Hb that makes faeces brown), and bile salts
91
Which liver cells modify bile?
Cholangiocytes
92
Which cellular structures allow movement of bile?
Bile canaliculi
93
Describe the epithelium of the gall bladder.
Simple columnar
94
How does the gall bladder get rid of bile?
Pumps Na/Cl between epithelial cells. Osmotic pressure change causes water to rush in and remove bile
95
Which two main factors stimulate gallbladder action?
Vagus nerve, hormone cholecystokinin
96
What is the name for gallstones?
Cholecystitis
97
Describe the white blood cell components at each end of the pancreas. Why is this the case?
Basal end - basophilic, due to much RER
| Apical end - eosinophilic, due to zymogen
98
How does the digestive cascade begin?
An enteropeptidase converts trypsinogen to trypsin
99
What is the name of pancreatic duct cells in the cavity (acini)?
Centroacinar cells
100
Where does the pancreas join the duodenum?
Hepatopancreatic ampulla (of Vater)
101
Which group of joints open the mouth?
Temporomandibular joints (TMJs)
102
Name the four TMJs. Which opens the mouth?
Medial pterygoid, lateral pterygoid, temporous, masseter. Lateral pterygoid opens
103
Describe the classification of teeth.
Upper jaw is maxillary, lower is mandibular.
| 1, 2: Incisors. 3: canine. 4, 5: premolar. 6,7,8: molar.
104
Which cranial nerves supply general sensation of the mouth?
CN V2 (maxillary trigeminal) and CN V3 (mandibular trigeminal)
105
Name the three salivary glands.
Parotid, sublingual, submandibular.
106
What is the name for the gums?
Gingiva
107
Describe the routes of the 2nd and 3rd division of the trigeminal nerve.
2 -> pons, foramen rotundum, face
| 3 -> pons, foramen ovale, TMJs
108
Name the four tongue muscles.
Palatoglossus, styloglossus, hypoglossus, genioglossus
109
Describe the nerve supply of the tongue.
Anterior 2/3: general sens V3, special sens VII
Posterior 1/3: general & special sens both IX
Tongue muscles (except palatoglossus) supplied by XII
110
Describe the route taken by cranial nerve VII, the facial nerve.
Pontomedullary junction, temporal bone via internal acoustic meatus, stylomastoid foramen, anterior tongue with muscles for facial expression and mouth
111
Name CN IX and XII.
IX - glossopharyngeal (tongue and pharynx)
| XII - hypoglossal (tongue muscle)
112
Describe the muscle and nerve anatomy of the oesophagus.
Circular constrictor muscles overlap each other. All connect to the midline raphe. X supplies voluntary. IX and X supply involuntary. Plexus is present
113
Name the three types of GI contraction.
Cervical (head), thoracic, diaphragmatic
114
Describe the two sphincters of the oesophagus.
Top sphincter - anatomical. Bottom - z line, physiological. Intragastric pressure < intrathoracic pressure
115
Which condition will reduce efficacy of the oesophageal lower sphincter?
A hernia
116
Describe how food is swallowed. Also give the cranial nerves involved.
Lips close (VII), bolus pushed to oesophagus (XII), soft palate and larynx elevate (X), oesophagus contracts (IX, X), the pharynx raises and shortens, and peristalsis occurs
117
What are the three general areas of the GI tract, derived from embryological origin?
Foregut (up to pylorus, 1/2 pancreas), midgut (to proximal end of transverse colon, 1/2 pancreas), hindgut (descending colon to anus)
118
Name the nine areas on the 'chest grid'.
Top row - hypochondrium, epigastric (RH, E, LH)
Middle - lumber (flank), umbilical (RL, U, LL)
Bottom - iliac fossa, pelvic (RI, P, LI)
119
Give descriptive words for the peritoneum.
Thin, transparent, semi-permeable
120
Name the three categories of peritoneal organ.
Intraperitoneal (entirely visceral), retroperitoneal (visceral in anterior only), mesentery (double visceral wrap)
121
Where does communication between the greater and lesser stomach sac occur?
Omental foramen
122
Which nerve fibres do visceral afferents travel back to the CNS with?
Sympathetic
123
Name the visceral afferent spinal outlets for the three Gi categories.
Foregut - T6-9, Midgut - T 8-12, Hindgut - T10 - L2
124
Name the four fibres in which somatic motor, somatic sensory, and sympathetic fibres are conveyed in.
Thoracoabdominal, subcostal, iliohypogastric, ilioinguinal (7-11th ICs, T12. two halves of L1)
125
Describe the progression of pain felt in appendicitis.
Dull and aching to sharp stabbing in right inguinal area
126
What is ascites?
Collection of fluid in the peritoneal cavity.
127
Which procedure should be used to treat ascites? Why must care be taken?
Paracentesis ('abdominocentesis'). Must drain lateral to rectus sheath, to avoid inferior epigastric artery
128
What is the name for pain that comes and goes?
Colicky pain
129
Which four factors should be considered when assessing pain?
Location, character (visceral, somatic), referral pattern, and timing
130
At which levels are the abdominal organs supplied by sympathetic nerves?
T5 - L2
131
Describe how the sympathetic supply reaches the organs of the abdomen from the CNS.
Abdominopelvic splanchnic nerves -> prevertebral ganglia -> periarterial plexus (hitches a ride)
132
How does the adrenal gland's sympathetic innervation differ from normal sympathetic supply? Where?
No synapse at the ganglia, synapses directly with cells. T10 - L1
133
Where are foregut, midgut, and hindgut pain typically felt?
Epigastric, umbillical, pelvic
134
Name the main regions of the stomach. What are the two halves called?
Fundus, body, antrum, pylorus. Orad, caudad
135
How does activity of the orad stomach break down food?
Weak tonic contractions with low amplitude. Minimal mixing.
136
What may increase or decrease rate of orad contractions?
Vagal increases, gastrin decreases
137
How does activity of the caudad stomach break down food?
Slow waves that reach potential. Retropulsion against the pylorus breaks down food (faster velocity) and allows it to pass through
138
What is the name for the wave that passes from caudad stomach through to the duodenum?
The antral wave (/pump)
139
Which three factors change rate of caudad stomach antral waves?
Rate of emptying, distension, consistency
140
Which factors decrease rate of stomach emptying?
Neurons and hormones (fat, acid), hypertonicity, distention
141
Name the two types of epithelium in the stomach regions and which cells they primarily are composed of.
Orad - oxyntic, parietal
| Caudad - pyloric, chief
142
Which chemicals may the orad stomach epithelium secrete?
HCl, peptinogen and pepsin, intrinsic factors, gastroferrin, mucus
143
Which chemicals may the pyloric stomach epithelium secrete?
Gastrin (increasing HCl), somatostatin (decreasing HCl),mucus
144
There are two pathways of secreting H for HCl in the stomach - direct and indirect. Briefly describe them.
Direct - ACh, gastrin, or histamine may act directly on mucosal cells, or ACh/gastrin may act on ECLs to activate histamin release
145
What is the name of a chemical which promotes secretion from a cell?
A secretagogue
146
Which chemicals prevent H+ secretion from the stomach epithelium?
Somatostatin and prostaglandin
147
By which chemical pathways do the secretagogues for H+ in the stomach epithelium act?
ACh/gastrin - IP3 and PIP2
| Histamine - adenylyl cyclase
148
Name the three secretory phases. Describe them.
Cephalic - ACh, gastrin, and histamine released
Gastric - distension causes secretion.
Intestinal
149
Which factors will decrease acid secretion in the stomach?
Food buffers, pH, D cell inhibition
150
Which channels are involved for H+ secretion in the stomach?
K+, Cl- (CFTR), Na/K ATPase, H/K ATPase, Cl-/HCO3 symporter
151
What is segmentation?
Contraction of the circular muscle in the intestine to divide chyme into segments, breaking it down
152
What is the mechanism of segmentation? What may affect its rate?
Slow wave thresholds - gastroileal reflex, or autonomic innervation triggers and increases/decreases respectively
153
Which two main hormones trigger H+ release in the stomach?
Gastrin and secretin
154
Which two main hormones inhibit gastric emptying?
Gastric inhibitory peptide (GIP), and glucose-like protein 1 (GLP1).
155
Which hormones trigger the MMR, and appetite respectively?
Motilitin, ghrelin
156
Describe the actions of the stomach hormone cholecystokinin (CCK).
Inhibits gastric emptying, pancreatic enzymes, and Oddi sphincter tone. Promotes secretion and bile
157
Which factors promote succus entericus, and which inhibits it?
Distension, irritation, gastrin, CCK, secretin, vagal activity increase, sympathetic activity decreases
158
What are the two components of succus entericus, and where do they come from?
Mucus, aqueous salt
| Goblet cells, crypts of Lieberkuhn
159
Which channel proteins are mainly associated with succus entericus release?
Na/K ATPase, Na/K/2Cl cotransporter, CFTR
160
What is the name of the electrical activity of peristalsis?
Migrating motor complex
161
What is the main purpose of the migrating motor complex?
A housekeeping function - cleans up
162
Which factors may promote peristalsis, and which supress or inhibit it?
Promotes - motilitin
Suppresses - gastrin, CCK
Inhibits - vagus, eating
163
Describe the difference between the exocrine and endocrine pancreas.
Exocrine - digestive juices containing proteases, lipases, amylases etc from acinar (centroacinar) cells
Endocrine - glucagon/insulin from islets of Langerhans
164
What is the purpose of pancreatic duct cells?
Secrete alkaline HCO3-, neutralising chyme and protecting the mucosa from self-digestion
165
Name the five main proteases.
Elastin, chymotrypsin, trypsin, carboxypeptidase A & B
166
Name the two stages of assimilation.
Digestion and absorption
167
Briefly describe the breakdown of carbohydrate.
Starch -> oligosaccharides (alpha-amylase) -> monosaccharides (oligosaccharidase)
168
Describe the actions of the carbohydrate-lytic enzymes.
Alpha-amylase breaks alpha 1-4 glycosidic links internally. Oligosaccharidases break terminal a 1-4 links
169
Name four of the main oligodendrocytes.
Maltose, sucrose, isomaltase (all faster than absorption) lactase (slower than absorption)
170
Name the main entry and exit channels of glucose in enterocytes.
Entry - SGLT1 (Na/glucose symporter), GLUT5 (fructose entry), GLUT2 (all exit)
171
Briefly describe the breakdown of protein.
Protein -> peptides (HCl, pepsin) -> oligopeptides (trypsin, chymotrypsin, elastase, carboxypeptidase A/B) -> amino acids (membrane protein)
172
Describe the difference between endopeptidases and exopeptidases.
Endo- break down to 2-6 peptide chain
Exo- break down to single amino acids.
Trypsin, chymotryspin, elastase are endo
Carboxypeptidase A/B are exo-
173
Describe the movement of amino acids in enterocytes at the apical and basolateral membranes.
Apical - 7 methods (5 require Na)
| Basolateral - bidirectional. 3 efflux 2 influx
174
How are di/tri/tetrapeptides absorbed in the enterocyte?
Absorbed by H+ methods, degraded within the cell
175
Name the two main enzymes associated with lipolysis.
Gastric and pancreatic lipase
176
Describe how most lipids/fats are broken down outside enterocytes.
Micelle formation. Outer lipids hydrolysed by pancreatic lipase, replaced by inner lipids, shrinking micelle
177
When fats have been broken down, they typically have around 12 carbons. What happens to those > 12, and < 12?
< 12 - diffusion
| > 12 - chylomicron storage
178
Describe the role of bile salts in fat degradation.
Bile salts increase surface area, but block access by lipases - colipase fixes this
179
Describe the problems that may arise from lack of bile salts.
Steahorroea (fat in stool), and fat-soluble vitamin deficiency
180
Which drugs should be used to treat hypercholesterolaemia?
Ezetimbe - NPC1LP1, statins
181
Why is iron important physiologically?
Component of Hb (2/3 of body store)
182
How is iron absorption/degradation matched?
By the duodenum
183
Describe the problems caused by a lack/excess of iron.
Anaemia, toxicity to the liver, heart, pancreas
184
Describe briefly the absorption of Fe3+ into enterocytes.
Absorped by channel protein, (can be stored by apoferratin), exits by ferraportin. Transported across by mobilfarrin. Reduced by a factor to Fe2+
185
Name the reduction factors for Fe3+.
HCl, vitamin C, Dctyb (duodenal cytochrome B), gastroferrin
186
Describe how haem may be degraded in enterocytes.
Degradation to Fe2+ and bilverdin by haem oxidase
187
Which factor increases absorption of iron, and which decreases ferraportin expression?
Absorption - blood loss
| Ferraportin - hepcidin
188
Describe vitamin B12.
Not water soluble. Not in vegetables - vegans may suffer from insufficiency
189
Which three factors do fat-soluble vitamins require to be absorbed?
Bile secretion, intact mucosa, mixed micelles
190
Describe the absorption of calcium in enterocytes.
Passively absorbed (paracellular), actively (transcellular). Mostly active in chyme. Regulated by 1,25-dihydroxyvitamin D (calcitrol) and parathyroid
191
Describe where each layer of GI histology originates embryologically.
Visceral mesoderm - lamina propria, muscularis mucosae, muscularis externa, CTs
Endoderm - epithelium, associated ducts/glands
Neural crest - ENS, Meissner's, Auerbach's plexuses
192
Which embryo landmarks does the intestinal mesentry originate from?
(Ventral) falciform ligament, lesser omentum
| (Dorsal) mesogastrium, mesoduodenum, mesocolon
193
When are the oesophagus, circular muscle, and longitudinal muscle formed?
Week 4, 5, 8
194
Describe what occurs during week 4 of gastrointestinal development.
Caudal foregut dilates. Dorsal border grows and rotates 90 degrees
Duodenum formed from caudal foregut (1, 2) and cranial midgut (3, 4)
195
Describe how the liver is developed during embryological growth.
Liver bud -> mesoderm of the septum transversum, which forms haematopoetic, Kupffer, and connective cells
Endoderm -> hepatocytes, biliary tree
196
Describe how the pancreas is developed during embryological development.
Dorsal pancreatic bud -> dorsal duct -> main duct
Ventral swaps sides (R->L) and becomes retroperitoneal
Ventral is bilobed, wrapping round and forming the annular pancreas
197
Describe the formation and development of the spleen during embryological development.
W5, from mesoderm. Haemopoetic then lymphatic
| Lobes becomes notches
198
Describe the development of the midgut through embryological growth.
(bottom half of duodenum to proximal 2/3 colon)
w4 - yolk sac communicates with midgut. YS narrows to form the vitelline duct.
Rotates out as an outgrowth to form structures
w10 - re-entry (small intestine first, caecum last)
199
Name the main defects that can occur with midgut development.
Meckel's diverticulum
| Vitelline cyst/fistula
200
Which embryological structure forms the perineal body, anal membrane, and anorectal canal?
The cloaca and cloacal membrane (hindgut)
201
Name the main defects that can occur with anal formation.
Urorectal, rectovaginal, and rectoperineal fistulas.
202
Name the three main organs associated with bile and their role in this system.
Spleen (formation of bilirubin), liver (converts to bile), gallbladder (stores/concentrates bile)
203
Why is bile important?
To aid in absorption of fats in the small intestine.
204
What is the name of the major artery which supplies the foregut organs? How does it divide?
The celiac trunk - splenic, left gastric, hepatic trifurcation
205
The celiac trunk trifurcates. What does each division then bifurcate to?
Gastroduodenal and superior pancreatico-duodenal
206
Describe the spleen.
Intraperitoneal. Pain felt in left hypogastric region. Ribs 9-11. Moves with respiration
207
Describe the blood supply of the stomach.
L/R gastric arteries (lesser curvature)
L/R gastro-omental arteries (greater curvature)
Both sets anastamose.
208
What is the name of the vessel that supplies the gallbladder with blood? Where does it arise?
The cystic artery. The right hepatic artery
209
Describe the pain supply around the gallbladder.
Visceral afferents T6-9. Pain felt in epigastic/hypogastric regions (+/- referral to right shoulder)
210
Describe the division of the liver.
```
4 anatomical (L/R/quadrate/caudate)
8 functional (I-VIII), each with own vessel set
Segmentectomy can be performed
```
211
Describe the most common cause of hepatomegaly.
Increased central venous pressure means backup through IVC and hepatic veins. No valves
212
Name the two pouches surrounding the liver.
Hepatorenal (Morison's), subphrenic
213
Name the main veins surrounding the liver.
Splenic, inferior/superior mesenteric, hepatic portal vein, IVC (see notes for assembly)
214
Name the three main ligaments surrounding the liver, and what they attach to.
Coronary - diaphragm
Falciform - anterior abdominal wall
Ligamentum teres - umbilical vein remnant
215
What is the difference between paracellular and transcellular transport?
Transcellular occurs through cells, paracellular through tight junctions
216
Lymphoid tissue is typically found in two different types in GI tissue. Describe these.
Scattered - typically crypts
| Organised - Peyer's patches
217
Describe the process by which T cell activation of dendritic cells causes them to migrate to the lumen.
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T cells (guided by CCR7, L-selectin)
Paracellular transport
Maturation of dendrites (a4B2, CCR9)
Drains to thoracic duct
Attaches by MaDCAM1
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218
Which feature of dendrites allows greater neutralisation of pathogens in the GI tract?
Extension across cells into the lumen
219
Describe the composition of the humoural response in the GI mucosa.
80% IgA (a J dimer), 15% IgM, 5% IgG
220
Describe, in general, non-specific terms, the role of commensals in the GI tract.
Assist in hyporegulation of immune/T cells, prevents maturation of dendrites
221
Describe the specific pathway in which T cells cause genetic transcription of immune factors.
T cells activate IKK pathway
This phosphorylates IaB
This moves NFaB into the nucleus to bind to DNA
222
Which specific chemicals do commensal organisms in the GI tract release to downregulate NFaB and dendrite maturation?
NFaB -> PPARgamma
IaB -> don't need to know (just be aware)
Dendrites -> PGE2, TGF-B, TSLP
223
How can T cells destroy virally infected GI mucosal cells?
MHC class I, perforin/granzyme/FAS-ligand paths
224
How can non-specific (innate) immune cells stimulate a response locally in the GI tract?
PRRs trigger the NFkB path, releasing chemokines, cytokines, and defensins
225
Describe the relationship between dendrites and activation of T cells.
Immature dendrites activate TH3/Treg
| Mature dendrites activate TH1/TH2
226
Describe the role of TH2 cells in GI mucosal immunity.
Activates eosinophils, mast cells, and stimulates B cells to release IgE. Can also stimulate repair/mucus secretion in mucosal cells
227
Describe the role of TH1 cells in GI mucosal immunity.
Stimulates B cells to produce IgG2a, activates macrophages
228
Describe what occurs when mucosal immunity is disregulated.
Infected macrophages travel to lymph nodes, infecting CD4 cells, spreading the infection.
229
Describe the mechanism of food allergy.
Type I hypersensitivity. Cross-linking of IgE on mast cells with specific food antigens.
230
Describe the effects of general and local histamine release.
General -> systematic anaphylaxis
| Local -> acute uritcaria (hives)/wheal and flare
231
What is the primary GI response to asthma and seasonal rhinoconjunctivitis?
Mucus secretion
232
How does Coeliac's cause malnutrition? Which specific immune components does this involve?
Damage to the small intestine
| Gamma interferon from gluten specific T cells -> IL-15 -> proliferating IEL, killing epithelial cells
233
What two tests should be used for diagnosing of Coelic's disease?
Biopsy (gold standard, especially in paeds)
| Serology useful for IgA levels
234
Describe the immunologic effects of Crohn's disease.
Distal ileum/colon (although all GI tract can be affected)
| Focal/discontinous inflammation with deep, eroding fissures (+/- granulomas)
235
Which specific immune components are present in Crohn's disease?
TH1, gamma interferon, IL-12, TNF alpha
236
Describe the immunologic effects of ulcerative colitis.
Starts at rectum, moves proximally
Can result in arthritis/uveitis/skin lesions
Distorted crypts, monocyte/neutrophil/plasma cell infiltration
237
How should Crohn's and ulcerative colitis be treated?
With NSAIDs and immunosupressive drugs
238
What do the following crypt cells secrete: chief, D cell, G cell, enterochromoffin-like cell (ECL), parietal, mucus?
Chief - pepsinogen, D - somatostatin, G - gastrin, ECL - histamine, parietal - HCl, mucus - mucus and bicarbonate
239
Describe how the crypts of Lieberkuhn are kept at a pH of 6-7 while the stomach is at a pH of 1.
Mucus/bicarbonate layer secreted by mucus cells
240
Is crypt secretion typically paracrine, exocrine, or endocrine?
Paracrine
241
Name the receptors that histamine, ACh, gastrin, and somatostatin affect.
H2, M3, CCK2, SSRT2
242
Describe the mechanism by which antacids can reduce indigestion.
Binds H+/HCO3- to form H2O/CO2, buffering HCl
243
Describe the mechanism of, indication of, and effects of misoprostol.
Prostaglandin E1 analogue.
Indicated for peptic ulcers.
Can cause abdominal pain, diarrhoea, and induce labour
244
Name three prostaglandin E1 analogues, other than misoprostol.
Lanzoprasole, ameprazole, pantoprazole
245
Describe the mechanism and effects of proton pump inhibitors.
Irreversibly binds H+/K+ ATPase.
Indicated for peptic ulcers.
Can increase pH, leading to impaired stomach defences
246
Describe how the treatment of H. pylori should occur with benign peptic ulcer formation.
PPIs and abx
| clarithromycin, amoxicillin/metronidazole
247
Name the five types of anti-emetic, and which receptor they target.
Anti-histamines (H1, brain). Anti-muscarinics (M1, brain). 5-HT3 antagonists (5-HT3 receptor). Dopamine antagonists (D2). Neurokinin-1 antagonists (NK1)
248
Describe anti-diarrhoeal drugs.
Electrolyte replacment. Binds to u-opiate receptors.
| Can be combined with atropine.
249
Name the three main laxatives.
Lspagula husk, lactulose, senna-stimulant purgative
250
How is the iliocaecal sphincter opened?
The gastroileal reflex, driven by CCK and gastrin. Opened when duodenum is distended (and closed when colon distended).
251
Name the main cause of appendicits.
Faecalith
252
Name the ions secreted and absorbed by the colon.
Absorbed - Na, Cl, H2O
| Secreted - K, HCO3, mucus
253
Which features of the colon assist in absorption of ions?
Folds, crypts, microvilli.
| Goblet cells, which secrete trefoil protein and glycosaminoglycans (host defence)
254
Which three methods does the colon have to move material along its length?
Haustration (like segmentation, but slower, to allow absorption). Peristalsis-like movement 1-3 times a day (gastrocolic response), defaecation
255
What are the main advantages of colon commensal bacteria?
Competes with pathogens, motility/mucosal integrity, vitamin K synthesis, activates some IBD drugs
256
What is the name of air expelled through the anus? Where can it arise from?
Flatus - swallowed air or indigestable carbohydrates
257
Give the main symptoms and treatment of IBS.
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Diarrhoea, constipation, abdominal pain.
Symptomatic relief (linaclotide constipation, amitriptyline for pain)
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258
Give the five main functions of the liver.
Metabolism of carbohydrates, fats, and proteins. Stores vitamins and glycogen. Kupffer cells - immunity/bilirubin breakdown
259
Name the many components of liver primary juice.
Cholic, chenodeoxycholic acids, electrolytes (Na/K/Ca/Cl/HCO3), lipids, phospholipids, cholesterol, IgA, bilirubin, metabolic waste
260
What is the name of the ducts in which liver primary juice run to bile ducts?
Canaliculi
261
Cholelithiasis is formation of gallstones in the liver tracts. Describe treatment.
Laparascopic cholecystectomy, analgesia, atropine/GTN for biliary spasm
262
By which process do bile salts/acids return to the liver?
Enterohepatic recycling
263
Describe how some bile salts may be degraded to bile acids in the GI tract.
Bacteria can dehydroxylate
264
What are bile salt/acid sequestrants?
Resins. Stop bile salt/acid being reabsorbed by binding.
265
Name the three main bile acid/salt sequestrants/resins.
Colveselam, colestepol, colestyramine
266
Name the set of enzymes in the liver responsible for most metabolism reactions.
Cytochrome P450 (CCY)
267
Describe cytochrome P450 enzymes.
A family of monooxygenases in the liver ER
268
What is hepatic encephalopathy?
Failure of the urea cycle to degrade ammonia. Toxic buildup leads to incoordination, drowsiness, coma, cerebral oedema, and death.
269
Describe the metabolism of aspirin in the liver.
Aspirin (drug) -> salicylic acid (derivative) -> glucuronide (conjugate)
270
How should hepatic encephalopathy be treated?
With lactulose or antibiotics
271
Describe the bile flow from liver and gallbladder to the duodenum.
R + L hepatic ducts -> common hepatic
CH + cystic -> common bile duct
CBD + common pancreatic -> ampulla of Vater
272
Name the three main sphincters in the bile flow.
Bile duct sphincter, pancreatic sphincter, sphincter of Oddi
273
Which investigation may be used to visualise the biliary tree?
Endoscopic retrograde cholangiopancreatotography
274
Describe the main cause of extra/post-hepatic obstructive jaundice.
Gallstones/carcinoma in the head of the pancreas, causing bile to back up to the liver (forcing bilirubin into the blood)
275
Name the four areas of the pancreas.
Head, uncinate process, body, tail
276
Name the main cause of pancreatic pain. Where does it present in the patient?
Pancreatitis - epigastric/umbillical regions
277
The duodenum and pancreas have an intimate relationship. Describe the vasculature between them.
Superior and inferior gastropancreatic arteries (from common hepatic and superior mesenteric respectively)
278
Name the four areas of the duodenum.
Superior -> descending -> horizontal -> ascending
279
Describe the main difference between the epithelium of the jejunum and the ileum.
Jejunum -> plicae circularis
| Ileum -> much smoother
280
Where does the duodenum become the jejunum?
At the duodenaljejunal (one word) fixture
281
Describe how chylomicrons are transported to venous circulation.
Through lacteals -> left venous angle
282
Name the four main lymphatic systems of the GI tract.
Celiac, superior mesenteric (midgut), inferior mesenteric (hindgut), lumbar
283
Name the eight main components of the liver function test.
```
Liver - AST/ALT
Biliary - ALP/GGT
Pancreas -amylase/lipase
Prothrombin time (PT)
Bilirubin (conjugated/unconjugated)
```
284
Of the enzymes in the liver function test, which are more specific? To where?
ALT - liver/hepatocytes
GGT - biliary tree
Lipase - pancreas (amylase also salivary)
285
Which clotting factors does the liver produce?
I, II, V, VII, IX, X, XII, XIII (1, 2, 5, 7, 9, 10, 12, 13)
286
What are the three causes of malabsorption?
Luminal digestion, mucosal disease, structural disease
287
Name the specific disease states that cause malabsorption.
Coeliac, lactase malabsorption, tropical sprue, Whipple's, Crohn's, Parasites, bacterial overgrowth
288
Name some causes of malnutrition.
Disease, hospital admission, chronic, acute, psychosocial
289
What are the symptoms of malnutrition?
Impaired immune response, fatigue, water/electrolyte disturbances, thinness, history weight loss, loose clothes, swallowing
290
What is the main tool for malnutrition, and describe it?
MUST - BMI/% weight loss/acute effects
291
Name the two types of tube feeding.
Enteral (nasogastric, nasojejunal, percutaneous)
| Parenteral (specialist and expensive)
292
What is the name of the site where fluid can collect next to the colon?
Paracolic gutters
293
Name the three main cavities in the peritoneal cavity.
Supracolic, infracolic, paracolic gutters
294
The position of the appendix is variable. In which position is it usually found?
Retrocaecal
295
What is the name of the point at which the appendicel orifice can be palpated?
McBurney's point
296
Which component allows movement of the sigmoid colon?
Mesentery
297
Describe the arterial supply of the GI tract from the abdominal aorta.
Celiac trunk, SMA, IMA
Splits into left common iliac, right common iliac
Lateral branches to kidneys/adrenal glands etc.
298
What is the name of the anastamosis between the SMA and IMA?
Anastomosis of Drummond
299
Name the three venous anastamoses between hepatic and systemic flow.
Ligamentum teres, distal oesophagus, rectum/anal canal
300
What is the name of the muscle which forms the pelvic floor? Which three muscles are these split into?
Levator ani -> iliococcygeus, pubococcygeus, puborectalis
301
Describe the two nerve supplies to the levator ani.
Nerve to levator ani
| Pudendal (S2, 3, 4)
302
What is the name of the division between the colon and rectum? What anatomical level does it occur?
Rectosigmoid junction, S3
303
What is the name of the division between the rectum and anus?
Pectinate line
304
Describe the three main sphincters of the anal canal.
Internal -> sup 2/3 -> symp/para
External -> inf 1/3 -> pudendal/distension
Puborectalis -> voluntary
305
Give the anatomical landmarks of the 1. sympathetic supply, 2. somatic motor supply, 3. parasympathetic.
1. T12-L2, 2. S2-4, 3. S2-4
306
Describe the course of the pudendal nerves.
Branch of sacral plexus -> greater sciatic foramen
307
Describe the embryonic layers as divided by the pectinate line.
Visceral and parietal
308
Name the three main abdominal lymph nodes.
Internal, external, and common iliac
309
Name the fat and loose connective tissue around the anus that communicates posteriorly.
Ischioanal fossae
310
Describe the linea alba and linea semilunaris.
Linea alba - from xiphoid to pubic symphesis
| Linea semilunaris - lateral to anterior abdomen
311
Name the five layers of muscle in the abdomen and their muscle fibre orientation.
External oblique (hands in pockets), internal oblique (hands on chest), transversalis abdominus (horizontal), transversalis fascia, parietal peritoneum
312
Where are the sites of direct and indirect inguinal hernias?
Direct - Hesselbach's triangle
| Indirect - inguinal canal
313
What is the name of the structure that connects the inguinal canal to the skin?
The gubernaculum
314
What is the name of the area of innate weakness in femoral hernias?
Myopectineal orifice
315
Name the dimensions of the inguinal canal.
Superior - conjoint tendon (internal oblique + transversus abdominus)
Inferior - inguinal ligament
Anterior - external oblique
Posterior - transversalis fascia
316
When does a hernia become a medical emergency?
When it becomes strangulated.
