Gastrointestinal system Flashcards
(149 cards)
1
Q
What are sorbitol, xylitol and mannitol?
A
Sugar alcohols
2
Q
What is the function of soluble fibre?
A
Binds to water in the colon and swells - helping transit through the colon
3
Q
What is the function of insoluble fibre?
A
Slows reabsorption of bile acids therefore reducing cholesterol absorption
Blunts blood glucose response
4
Q
What health problems does higher fibre intake reduce risk of?
A
heart disease
stroke
type 2 diabetes
colon cancer
5
Q
What is the average amount of fibre suggested to consume in a day?
A
30g
6
Q
What is the average amount of protein suggested to consume in a day?
A
50g
7
Q
What are the reasons protein is important in each of these instances?
Structural, transport, hormonal, enzymes, immune function, buffering action
A
Structural - collagen, actin, myosin
Transport - carriers, haemoglobin, lipoproteins
Hormonal - insulin, peptides
Enzymes - metabolic pathways
Immune function - antibodies
Buffering action - albumin in blood pH
8
Q
What are the 8 essential amino acids?
A
Lysine
Leucine
Isoleucine
Valine
Phenylalanine
Methionine
Threonine
Tryptophan
9
Q
What are the 3 non essential amino acids?
A
Glutamic acid
Alanine
Aspartic acid
10
Q
Name two essential fatty acids
A
Linoleic acid (omega 6)
Alpha-linoleic acid (omega 3)
11
Q
Name the 5 classes of lipoproteins?
A
Chylomicrons
Very low density lipoproteins
Low density lipoproteins
High density lipoproteins
Lipoprotein (a)
12
Q
What are the function of chylomicrons?
A
Transport dietary lipids to peripheral tissues and liver
13
Q
What is the function of VLDLs?
A
Transports lipids from the liver to peripheral tissues
14
Q
What is the function of LDLs?
A
Transports cholesterol to peripheral tissues and liver
15
Q
What is the function of HDLs?
A
Removes cholesterol from peripheral tissues to the liver
16
Q
What is the function of albumin?
A
Transports free fatty acids from adipose tissue to peripheral tissues
17
Q
Which vitamins are fat soluble?
A
ADEK
18
Q
What is the role of Vitamin B1/ Thiamine?
A
Cofactor in decarboxylation reactions
19
Q
What is the effect of a deficiency in Vitamin B1/ Thiamne?
A
Beri-Beri - muscle weakness, nerve damage, can affect heart
20
Q
What is the role of Vitamin B2/ Riboflavin?
A
constituent of cofactors, involved in metabolism of fats, carbohydrates, proteins
21
Q
What is the effect of a deficiency in Vitamin B2/ Riboflavin?
A
Very rare - cofactors bind tightly to enzymes and efficiency conserved
22
Q
What is the role of vitamin B3/ Niacin?
A
Constituent of cofactors e.g. NADH
23
Q
What is the effect of a deficiency in vitamin B3/ niacin?
A
Pellagra - diarrhoea, depression, dermatitis, death
24
Q
What is the role of vitamin B5/ pantothenic acid?
A
Constituent of coenzyme A - energy metabolism, fat metabolism
25
What is the effect of a deficiency in vitamin B5/ pantothenic acid?
Unknown as found in almost all foods
26
What is the role of vitamin B7/ Biotin?
Prosthetic group
Acts as carrier for CO2 in carboxylation reactions e.g. fat synthesis
27
What is the effect of a deficiency in vitamin B7/Biotin?
Very rare
28
What is the role of vitamin B6/Pyridoxal phosphate?
Cofactor for enzymes involved in protein metabolism, haem synthesis, neurotransmitter synthesis, modulates steroid hormone action
29
What is the effect of a deficiency in vitamin B6/pyridoxal phosphate?
Irritability, depression, confusion
Inflammation of the tongue or mouth
30
What is the role of vitamin B9/ folic acid?
1-C transfers in DNA synthesis
31
What is the effect of a deficiency in vitamin B9/folic acid?
Neural tube defects, macrocytic anaemia
32
What is the effect of a deficiency in vitamin B12/cobalamin?
Macrocytic anaemia
Irreversible neurological damage
33
What is the role of Vitamin C?
Collagen synthesis
Antioxidant
34
What is the effect of a deficiency in vitamin C?
Scurvy (weakened collagen)
35
What is the role of vitamin A?
Vision (rod cell function)
Transcriptional regulator
Antioxidant
36
What is the effect of a deficiency in vitamin A?
blindness
susceptibility to infection
birth defects
37
What is the role of Vitamin D?
Bone formation and maintenance
Immune regulation
Cell differentiation
Muscle function
38
What is the effect of a deficiency in vitamin D?
Rickets in children
Osteomalacia in adults
39
What is the role of Vitamin E?
Antioxidant - prevents lipid oxidation in membranes
40
What is the effect of a deficiency in Vitamin E?
fat malabsorption - causes neurological problems
41
What is the role of vitamin K?
cofactor for enzymes in the clotting cascade
42
What is the effect of a deficiency in vitamin K?
Bleeding
(babies given vitamin K at birth)
43
Which mineral has the following functions?..
-bone and teeth formation
-muscle contraction
-nerve signalling
-regulates blood clotting
Calcium
44
Which mineral has the following functions?..
-bone and teeth formation
-energy metabolism
-cell membrane function
-ATP production
Phosphorous
45
Which mineral has the following functions?..
-enzyme function
-muscle relaxation
-nerve transmission
-cofactor for many enzymes
-regulates blood sugar
magnesium
46
Which mineral has the following functions?..
-fluid balance
-nerve impulse transmission
-blood pressure regulation
-maintains electrolyte balance
Sodium
47
Which mineral has the following functions?..
-fluid balance
-muscle contraction
-nerve impulse transmission
-maintains electrolyte balance
-blood pressure regulation
potassium
48
Which mineral has the following functions?..
-oxygen transport
-red blood cell production
iron
49
Which mineral has the following functions?..
-immune function
-cell growth and development
-wound healing
zinc
50
Which mineral has the following functions?..
-antioxidant defence
-iron metabolism
-connective tissue health
copper
51
Which mineral has the following functions?..
-antioxidant defence
-thyroid hormone metabolism
Selenium
52
Which mineral has the following functions?..
-thyroid hormone production
iodine
53
Which mineral has the following functions?..
-enzyme function
-antioxidant defence
-bone health
manganese
54
Which mineral has the following functions?..
-glucose metabolism
-insulin sensitivity
chromium
55
What are the NHS guidelines concerning vitamin D?
All adults and children above 4 should consider taking 10mcg vitamin D during autumn/winter
56
What are the NHS guidelines concerning folic acid?
pregnant women should take 400mcg of folic acid every day prenatally until 12 weeks
57
What are the NHS guidelines concerning salt?
No more than 6g per day
58
What are the NHS guidelines concerning multivitamins?
All children aged 6 months to 5 years should have vitamin supplements containing vit A,C,D
59
What are the causes of deficiencies?
Social
Medical
Restricted diets
Malabsorption
Chronic blood loss
Pregnancy (incr. req.)
60
What is kwashiorkor caused by?
Protein deficiency
61
What is goitre caused by?
iodine deficiency
62
What is acrodermatitis enteropathica caused by?
Zinc deficiency
63
What percentage of patients weigh less on discharge from hospital?
70%
64
What are the 6 functions of the GI tract?
Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion
65
What are mesenteries?
Layers of peritoneum that suspend the organs, support them and keep them from tangling
66
Why is peritoneal fluid necessary?
Provides lubrication
Permits organs to move against each other without friction
67
What structures are contained within the mesenteries?
Blood vessels
Nerves
Lymphatics
68
Which artery from the aorta supplies which part of the gut?
Foregut - coeliac trunk
Midgut - superior mesenteric artery
Hindgut - inferior mesenteric artery
69
Where does the blood from the GI tract largely drain into?
Hepatic portal vein
70
Describe the major layers of the digestive tract from innermost to outermost
Mucosa —> submucosa —> muscularis externa —> serosa
71
What are the different types of intercellular junctions?
Tight junctions
Adherents junction
Desmosome
Gap junctions
Hemidesmosome
Actin-linked cell-matrix adhesion
72
How are solutes and H2O moved across epithelial cells?
Absorption - from external to internal compartment
Secretion - from internal to external compartment
73
Explain how the enteric nervous system innervates the gut
Contains myenteric and submucosal plexi
Modulated by input from autonomic NS
-myenteric (regulates motility)
-submucosal (regulated secretions and blood flow)
74
Which muscles are involved in mastication?
Temporalis
Masseter (insert pic)
75
Which cells mediate slow waves?
Interstitial cells of Cajal
76
Explain how the gut is externally innervated
By the autonomic nervous system (sympathetic and parasympathetic) to stimulate and inhibit digestion
77
What are the major salivary glands?
Parotid gland (big one)
Sublingual gland
Sub mandibular gland
78
What is the role of saliva?
Lubrication and cleaning
Facilitation of taste
Protection against acid and bacteria
Digestion
79
How is saliva production regulated?
Both parasympathetic and sympathetic
Triggered by:
- local stimuli
- central stimuli
- relflex
80
How is saliva produced and what is this?
Picture shows a salivon
Initial isotonic fluid containinf NaCl, protein and mucus is passed along a duct.
Salt re4absorption and HCO3 secretion leads to a hypertonic, alkaline fluid
81
Which salivary gland does this refer to?
- largest salivary gland
- predominantly serous secretion
- around 50% of salivary volume
- main source of salivary amylase and proline-rich proteins
- parasympathetic supply via CN IX
- sympathetic supply from superior cervical ganglion
Parotid gland
82
Which salivary gland does this refer to?
- mixed serous and mucus secretion
- about 45% of salivary volume
- main source of lysozyme and lactoperoxidase
- parasympathetic supply via CN VII
- sympathetic supply from superior cervical ganglion
submandibular gland
83
Which salivary gland does this refer to?
- predominantly mucous secretion
- about 5% of salivary volume
- main source of lingual lipase
- parasympathetic supply via CN VII
- sympathetic supply from superior cervical ganglion
sublingual gland
84
what is the optimum pH of amylase and the pH at which it denatures?
optimum = 7
denatured = 4
85
What is the function of lingual lipase?
- and what is its optimum pH?
Cleaves the outer fatty acids off triglycerides, leaving diacyl glycerol
optimum pH = 4
86
What are the three types of papillae?
foliate
circumvallate
fungiform
87
What type of cells line the oesophagus?
stratified squamous epithelium
88
How is the oesophagus innervated?
by fibres from the oesophageal plexus
89
What is the cephalic phase of GI activty?
- First part of the digestive process
- Mediated by the parasympathetic nervous system
- combination of stimuli, some conscious, some not
90
What parts of the GI tract mark the start and end of the foregut?
mouth to 1st half duodenum
91
What parts of the GI tract mark the start and end of the midgut?
2nd half duodenum to 2/3 along transverse colon
92
What parts of the GI tract mark the start and end of the hindgut?
distal 1/3 transverse colon to superior 2/3 of rectum
93
Is the epithelial lining of the GI tract derived from the endoderm, mesoderm or ectoderm?
endoderm
94
What are the smooth muscle and connective tissue of the GI tract derived from?
Visceral mesoderm
95
After the vitelline arteries stop supplying the yolk sac and supply the gastrointestinal tract instead, what 3 arteries do they become?
Coeliac trunk
superior mesenteric artery
inferior mesenteric artery
96
The dorsal and ventral mesenteries connect organs to what?
Dorsal mesenteries - posterior body wall
Ventral mesenteries - anterior body wall
97
What is this?
An acquired hiatal hernia
98
What is polyhydramnios?
Too much amniotic fluid
99
Why is the stomach shaped as it is?
The dorsal wall grows faster during development forming greater curvature
100
What is the space behind the stomach, liver and spleen called?
lesser peritoneal sac
101
What is the epiploic foramen?
A narrow opening that connects greater and lesser sacs
102
When the dorsal mesentery (attached to stomach) reflects back and forms an extension of the lesser sac - what is it then called?
The greater omentum
103
What is pyloric stenosis?
narrowing pf the pyloric sphincter caused by hypertrophy of smooth muscle
104
How common is pyloric stenosis?
Affects 1 in 500 births
More common in males than females 5:1
105
What are the signs of pyloric stenosis?
palpable pyloric mass
projectile vomiting
visible peristalsis
106
What part of the gut is the entrance of the common bile duct in?
foregut
107
Explain what is happening here in the recanalisation of the gut tube?
- Apoptosis of the epithelium occurs weeks 6-8 creating vacuoles
- vacuoles unite to fully recanalise the gut tube by week 9
- epithelial lining undergoes further differentiation creating villi
108
What has happened to the gut tube here?
Duplication of GI tract
109
What has happened to the gut tube here?
Stenosis and blockage pf the gut tube due to incomplete recanalisation
110
What are the parts of the small intestine called?
Duodenum
Jejunum
Ileum
111
What is the function of the crypts of lieberkuhn?
They secrete bicarbonate-rich fluid
112
Explain the process of peristalsis
1. Circular muscles cntract behind the bolus while circular muscles ahead relax
2. longitudinal muscles ahead of bolus contract
3. wae of contraction in circular muscles forces bolus forward
113
What is segmentation in the gut?
Alternate contractions of neighbouring segments
- churn and fragment the bolus
- mix contents with intestinal secretions
114
When the gut is empty, how often are migrating motor complexes generated and why?
every 90 minutes
thought to keep the gut clean, prevent reflux and reduce bacterial growth
115
What hormones are secreted in the small intestine from the crypts of Lieberkuhn - from APUD cells?
- CCK from I cells
- secretin from S cells
- motilin from M cells
- Gastrin from G cells
116
Broadly, how are carbohydrates digested?
Soluble amylases break internal a1,4 bonds
Remaining short chain carbohydrates are broken down by specific enzymes on the bush border membrane
117
How are glucose and galactose absorbed?
actively by SGLT1
118
How is fructose absorbed?
passively by GLUT5
119
Describe how proteins are digested
- pepsin (15%) in stomach
- enterokinase secreted by crypt cells activated pancreatic enzymes
- endopeptidases (trypsin, chymotrypsin, elastase)
- exopeptidases (carboxypeptidases)
- actively taken up by sodium linked transporters
- endocytosis
120
Describe how lipids are digested
- bile salts break up lipid droplets increasing surface area
- pancreatic lipase cleaves 2 fatty acids leaving monoglycerides
- bile salts solubise them forming micelles
- inside cell, triglycerides are resynthesised and packaged into chylomicra for exocytosis
121
What happens to bile salts after they are used?
95% recycled
actively absorbed in distal ileum
5% lost in faeces as deconjugated by bacteria
122
How is calcium absorbed?
actively in duodenum
regulated by vitamin D
reabsorbed paracellulary in small bowel
123
How is vitamin B12 absorbed?
absorbed only when bound to intrinsic factor
124
What do the following pancreatic enzymes become when activated in the small intestine?
- trypsinogen
- chymotrypsinogen
- proelastase
- procarboxypeptidase A
- procarboxypeptidase B
- trypsin
- chmotrypsin
- elastase
- carboxypeptidase A
- carboxypeptidase B
125
What is DIOS?
Distal Intestinal Obstruction Syndrome
126
Why is DIOS common in people with cystic fibrosis?
Thick sticky mucus causes a blockage in the intestines
127
Why is increased weight with cystic fibrosis so dangerous?
Risk factors for colorectal cancer
Obesity may increase risk
Insulin resistance
128
What fraction of people are carriers for the mutated CFTR gene?
1 in 25
129
What is creon and what is it given for?
Combination of lipase, amylase and proteases
Given for pancreatitis
130
What ligament divides the liver?
The falciform ligament
131
What is ratio of mass from right to left side of the liver?
7:3
132
Explain the livers dual blood supply?
20% hepatic artery
80% hepatic portal vein
133
What makes up the portal triad?
Arteriole, portal vein, bile duct
134
What cell types are in the liver?
Hepatocytes 80%
Endothelial cells
Cholangiocytes
Kupffer cells
Hepatic sellate cells
135
What are the livers key roles?
Digestion
Biosynthesis
Energy metabolism
DetoXification
136
What happens if the liver is damaged?
Excess fluid in the abdomen
137
Describe the livers role as a blood glucose buffer
After a meal when blood glucose increases
Excess glucose is stores as glycogen in the muscle and the liver
138
What is the livers role in protein metabolism?
Synthesis of 90% of plasma proteins
Synthesis of clotting factors
Synthesis of dietary non essential amino acids
139
What is transamination and how does it work?
Occurs in the liver
exchange of the amine group on an amino acid for the ketone group on another one
140
What is deamination and how does it work?
Conversion of amino acid into corresponding ketoacid
141
What are xenobiotics?
Potentially toxic with no nutritional value
142
What is the role of endothelial cells in the liver?
Lining blood vessels and sinusoids
143
What is the role of cholangocytes in the liver?
Lining biliary structures
144
What is the role of kupffer cells in the liver?
Fixed phagocytes
145
What is the role of hepatic stellate cells in the liver?
Vitamin A storage cells
May be activated to a fibrogenic myofibroblastic phenotype
146
147
What test do we do to see if the pancreas is functioning properly?
Faecal elastase
Look at calprotectin (inflammatory marker)
148
Why is there an increased risk of cancer with cystic fibrosis?
CFTR is a tumour supressor gene
149
