Gastrointestinal system Flashcards
(154 cards)
1
Q
functions of gastrointestinal system
A
Digestion - To process food
Absorption - Transfer of nutrients to circulation
2
Q
2 groups of organs in GI
A
Digestive tract
Accessory organs - salivary glands, gallbladder, liver, pancreas
3
Q
Describe the pharynx
A
Muscular tube approxiamately 12-15cm. It is responsible partly for food to pass through as well as air.
4
Q
Describe the oesophagus
A
Muscular tube and varies in length from approx 20-25cm. Extends from the pharynx and reaches down to the stomach. Passes behind the heart and trachea.
5
Q
Describe the stomach
A
Muscular organ located on upper left side of abdomen (left hypochondrium and epigastric regions). It secretes acid and enzymes that will start digestion.
6
Q
Describe the small intestine
A
3 parts from start to end;
- duodenum, jejunum, and ileum.
As you move from D to I you progress from digestion to more adsorption. In the duodenum you have secretions from the pancreas and also bile.
7
Q
Describe lamina propria
A
Thin layer of loose connective tissue which lies beneath the epithelium. It contains inflammatory cells and provides support and nutrients to the overlying epithelium.
8
Q
Describe muscularis mucosae
A
Next deep layer to the lamina propria and is composed of smooth muscle and is continuous all the way through the entire length of the GI tract
9
Q
Describe the submucosa
A
Deep to the muscularis mucosae. It is composed of dense irregular connective tissue and contains many blood vessels nerves and also lymphatic vessels.
10
Q
Describe the muscularis propria
A
AKA the muscularis externa
comprised of inner circular muscle and is responsible for peristalsis
11
Q
Describe the adventitia
A
Outer layer of fibrous connective tissue surrounding an organ.
gut = oral cavity
oesophagus = upper end
ascending or descending colon and rectum.
AKA serosa
Serosa is the part of the tissue that is fixed. It allows for reduction of friction.
12
Q
Order os structures of GI tract histology
A
deep to superficial
Mucosa
Submucosa
Muscularis propria (externae)
Adventitia/Serosa
13
Q
What are Meissner’s and Auerbach’s plexus
A
Nerve plexuses
14
Q
function of Brunner’s glands
A
Secretes bicarbonate ions to neutralise the acid of the stomach
found in duodenum
15
Q
describe peyer’s patches
A
Lymphoid follicles and form part of the immune function preventing the growth of dangerous bacteria
found in ileum
16
Q
Describe the layout of the abdomen
A
9 regions with 2 subcostal (horizontal) lines and two mid-clavicular (vertical) lines
- Right hypochondrium
- epigastric
- Left hypochondrium
- right lumbar
- umbilical
- left lumbar
- right iliac fossa
- suprapubic
- left iliac fossa
17
Q
What is contained in the right hypochondrium
A
liver
18
Q
What is contained in the epigastric
A
Duodenum, liver, gall bladder, pancreas, stomach
19
Q
What is contained in the left hypochondrium
A
spleen, stomach
20
Q
What is contained in the right lumbar
A
ascending colon, kidney
21
Q
What is contained in the umbilical
A
stomach, head of pancreas, small intestine (duodenum), transverse colon, lower aspects of r and l kidneys
22
Q
What is contained in the left lumbar
A
descending colon, left kidney
23
Q
What is contained in the right iliac fossa
A
caecum, appendix, part of ascending colon
24
Q
What is contained in the suprapubic
A
bladder, uterus, parts of small intestine (ileum)
25
What is contained in the left iliac fossa
sigmoid colon, descending colon
26
structure between stomach and duodenum of small intestine
pyloric sphincter
27
name the areas of the stomach
cardia - area at which food first enters
fundus - top area
body - middle section
pylorus - lower section
28
Describe the greater omentum
Fatty tissue that attaches to the greater curvature
29
Describe pyloric stenosis
affects the pyloric sphincter and presents with projectile vomiting
30
What are rugae
folds of the stomach that can be seen with the naked eye. They help increase surface area and allow for folding of the organ
31
3 layers of stomach wall from deep to superficial
Oblique muscle layer
circular muscle layer
Longitudinal muscle layer
32
Function of the muscle layers in stomach
Help with churning/mixing stomach contents called the chyme
33
Describe Endocrine cells
Within mucosa
Produce Gastrin
This stimulates the parietal cells to produce hydrochloric acid (breaks down pepsinogen into pepsin produced by chief cells
34
Function of mucous and surface mucous cells
Protect the mucosa
35
Describe villi
Finger-like projections that are well designed to increase surface area. They aid in digestion and absorption.
They number 10-40 per square millimetre of tissue. Most prevalent ate the beginning of the small intestine and diminish in number towards the end of the tract. They range in length from about 0.5 to 1mm
36
epithelia of the small intestine
simple columnar
37
describe the duodenum
recieves Chyme
Short length
Contains Brunner's glands (alkaline scretion)
Recieves common bile duct via sphincter of Oddi (surrounding the major duodenal papilla)
Ends at duodenojejunal junction
38
epithelium of stomach
simple columnar
39
structure of serosa
2 layers of mesothelium
double fold around the serosa and hold it in the abdominal cavity ?
40
Describe the pancreas
'dual purpose' gland
2 broad functions - hormonal (endocrine) and digestive (exocrine)
41
somatostatin
helps to reduce acid secretion and slows down digestive process
comes from delta cells
42
insulin
promotes glucose absorbtipn from blood into liver, skeletal muscle and fat cells. This enables the conversion to glycogen
comes from beta cells
43
glucagon
converts stored glycogen into glucose for release into the bloodstream when levels are low.
comes from alpha cells
44
Functions of the liver
Produces bile
Detoxifies and processes everything absorbed from the GIT
Regulates glucose in the blood
Synthesises proteins including the clotting factors and platelet regulations
Inactivates hormones and drugs
45
Blood supply to liver
Dual supply
75% = hepatic portal vein via the gut, spleen and related organs
25% = hepatic arteries
46
4 lobes of the liver
right main lobe (anterior)
left main lobe (anterior)
caudate lobe (superior posterior)
quadrate lobe (inferior posterior)
47
describe the large intestine
5 parts
- caecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
48
describe the caecum
located between the ileum and the ascending colon
reservoir for chyme
right iliac fossa of abdomen
intraperitoneal
49
ileocaecal valve
between caecum and ilium
prevents reflux of large bowel contents into the ileum during peristalsis and functions passively
50
ascending colon
retroperitoneal structure that ascends superiorly from the caecum
51
transverse colon
extends from the right colic flexure to the spleen.
least fixed part of the colon variable in position
intraperitoneal
52
descending colon
moves inferiorly towards the pelvis
retroperitoneal in majority of induviduals
located anteriorly to the left kidney
53
sigmoid colon
40cm long
located in left lower quadrant of abdomen
extends from left iliac foass to the level of the S3 vertebra
54
hepatic flexure
When the colon meets the right lobe of the liver it turns 90 degrees to move horizontally. This point marks the start of the transverse colon
55
Splenic flexure
When colon turns another 90 degrees after transverse colon to point inferiorly
AKA left colic flexure
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Taenia coli
3 longitudinal bands of smooth muscle on the outside of the ascending, transverse and descending colon.
incomplete layers of longitudinal muscle
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haustra
circumferential contraction of the inner muscular layer of the colon
ring-like circular muscle
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Appendice epiploicae
pouches of peritoneum filled with fat
mainly on transverse and sigmoid colon
not on rectum
59
function of goblet cells
produce mucous
60
blood supply of the GIT
3 main vessels all arising from abdominal aorta
Coeliac trunk (foregut)
Superior mesenteric artery (mid gut)
Inferior mesenteric artery (hind gut)
61
Foregut supplies
the oesophagus (lower portion), stomach, liver, spleen and first half of duodenum
62
midgut supplies
the last half of the duodenum, jejunum, ileum, caecum, appendix, ascending colon and first half to 2/3 of the transverse colon
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hindgut supplies
last 1/3 of the transverse colon, descending colon, sigmoid colon and rectum
64
venous drainage of GIT
Portal venous drainage for the unpaired abdominal organs
Femoral veins drain the lower limb
Internal iliac veins drain the pelvis
Renal veins drain the kidneys
Hepatci vein is the main vein draining the liver
65
"Define metabolism
Sum of all the chemical reactions in which energy is made available and consumed in the body
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"What do we need energy for
"
Contraction of muscle - movement
Accumulation of ions and molecules against conc gradients
Biosynthesis - building of tissues
Waste disposal
Heat generation
67
"exergonic defintion
"
Gives out energy
negative delta G
68
"define endergonic
"
requires energy to take place
positive delta G
69
"amphabolic reaction
"
Includes both anabolic and catabolic reactions
70
"2 phases of TCA cycle
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Decarboxylating (citrate to succinyl CoA)
Reductive (succinyl CoA to oxoloactetate)
71
"For every molecule of Coenzyme A that enters TCA cycle, what is produced
"
1 GTP (equivelant to 1 ATP)
3 NADH
1 FADH2
(each NADH oxidised by the ETC yields 2.5 ATP and each oxidised FADH2 yields 1.5 ATP)
72
"describe energy investment phase
"
2 ATP into 2 ADP
73
"describe energy pay-off phase
"
4 ADP into 4 ATP
2 NAD+ into 2 NADH
74
"Describe what happens to glycolysis under anaerobic conditions
"
Pyruvate is converted into lactate
This regenerates NAD+ (oxidised form) to keep glycolysis going
Fermentation of pyruvate into lactate removes a proton from NADH which produces NAD+ allowing glyoclysis to take place and prevent cell death.
This allows cells to synthesis a small energy source of 2 ATP
75
"What happens after glycolysis under aerobic conditions
"
Pyruvate is transported into the mitochondrion and converted to acetyl-CoA by pyruvate dehyrdogenase
This reaction also produces 1 molecule of carbon dioxide and 1 molecule of NADH
Coenzyme A is required for this reaction
76
"Describe the process of fatty acid breakdown
"
1. Fatty acids and glycerol are released from triglyceride stores in adipose tissue via the action of lipase enxymes
2. Transported in blood as a complex with albumin, taken up by cells for oxidation
3. fatty acid modification and entry to mitochondria
4. Beta-oxidation leading to ATP formation
77
"Is fatty acid breakdown endogonic or exogonic
"
endogonic - requires 2 molecules of ATP
78
"Describe how fatty acids are trasnported past the mitochondrial membranes
"
It can get through the first easily but in order to get through the second Fatty acyl coenzyme A must have its coenzyme A removed and cartinine added while it goes through the first.
the fatty Acyl cartinine is then able to transfer through the inner mitochondrial membrane and here its cartinine is removed and coenzyme A is replaced
CARTININE SHUTTLE
79
"describe fatty acid degradation (beta oxidation)
"
beta oxidation cleaves an acid between the alpha and beta carbons to produce as many molecules of coenzyme A as the structure will allow.
(ie, in a 16 carbon acid, 8 coenzyme A molecules are produced)
Each time this takes place it also produces 1 molecule NADH, 1 molecule FADH2 and 1 molecule H
(however, for the last cleavage, 2 Acetyle CoA are produced for only 1 of each the molecules above)
80
"Describe protein metabolism (transanimation and deanimation)
"
Transanimation:
1 amine group is added to alpha-ketoglutarate which transfroms it into glutamate. New alpha-ketoacid also produced.
deanimation:
occurs in liver
Amino group is removed, side production of ammonium. Neurotoxic so broken down by cells and removed in urea
81
"Glucogenic amino acid
"
break down products form glucose
- pyruvate
- oxaloacetate
intermediates of TCA
82
"ketogenic amino acids
"
break down forms fatty acids
- Acetyle Coenzyme A
- Acetoacetyle CoA
only examples include leucine and lysine
83
"Metabolic adaptations to starvation
"
Fat - triacylglycerols in adipose tissue is sufficient to prolong life for 3 months
Protein - provides approx 14 days worth of energy but is spared as long as possible to permit mobility
84
"what is the BEE
"
basal energy expendicture
represents the energy required to maintain basic functions when the person is lying down, relaxed (but not asleep), in normal ambient temperature
85
"Major causes of fatigue in running different distances
"
100-200m = phosphocreatine depletion
400-800m = ^^ and proton accumulation
1500 = proton accumulation
5000-42200 = glycogen depletion
86
Sources of saturated dietary fats
Mainly animal foods such as meat, fat, butter, cheese and cream
87
Sources of unsaturated dietary fats
Mainly from plants
olive and rape seed, nuts
88
Sources of cholesterol
dietary fats
Plants and animals
Dairy products
palm and coconut oil
89
9 essentail amino acids
phenylalanine
valine
tryptophan
threonine
isoleucine
methionine
histidine
leucine
lysine
## Footnote
percy vance tries to impres me, he looks ludicrous
90
Examples of monosaccharides
glucose, fructose, galactose
91
examples of disaccharides
Sucrose = glucose + fructose
Maltose = glucose + glucose
Lactose = glucose + galactose
92
example of polysaccharide
starch
- amylose linear
alpha(1->4) glycosidic bond
- amylopectine branched
alpha(1->4) glycosdic and alpha (1->6) glycosidic bond
93
Define digestion
Process by which food is broken down into components simple enought o be absorbed in the intestine
94
salivary secretion production
Parotid, submandibular and sublingual salivary glands
95
function of salivary secretions
moistens food
starts the digestion of carbohydrates alpha-amylase
96
2 cell types in stomach involved in digestion
Chief cells: secrete pepsinogen
Parietal cells: hyrdochloric acid secretion
97
What is a zymogen
Inactive pro-enzymes
98
Proteolytic enzymes in pancreatic secretions
trypsin
Chrymotrypsin
carboxypeptidase
elastase
phospholipase
## Footnote
tigers can carve extravagant pictures
99
non-proteolytic enzymes in pancreatic secretions
alpha-amylase
lipase
ribonuclease
deoxyribonuclease
## Footnote
All lions relish deer
100
role of bile
emulsification of fats
aids absorption of fats by forming complexes called micelles
101
activation of pancreatic zymogen
Enterokinase in the duodenum cleaves a part of trypsinogen and turns it into trypsin.
Activated trypsin goes on to activate all the other proteolytic enzymes in pancrease
102
brush border enzymes
not free in intestinal luman
tethered to plasma membrane of the enterocyte
this plasma membrane contains microvilli (brush border)
enzymes include peptidases, lactase, sucrase and maltase
103
Describe digestion in the mouth
Mastication breaks up food and moistens it
The remaining substance = bolus
carbohydrates: Starch broken down by alpha-amylase into maltotriose, maltose and alpha-limit dextrin
proteins: nothing
lipids: lingual lipase present
104
describe food breakdown in the stomach
food bolus enters via oesophagus and meets gastric juice
once mixed with gastric juice = chyme
carbohydrates: nothing
proteins: HCl denatures proteins and activates pepsin (endopeptidase that cleaves proteins to smaller peptides)
lipids: gastric lipase present
105
describe digestion in the duodenum
chyme mixes with pancreatic juice and bile
slightly alkaline
carbohydrates: alpha-amylase digests starch
brush border disaccharides into monosaccharides
proteins: cleaved by trypsinchymotrypsin, elastase, carboxypeptidases to produce increasingly smaller peptides
brush border peptidases produce dipeptides
lipids: pancreatic lipase digests lipids to monoglycerides and fatty acids. Phospholipase digests phospholipds to lysolecithin and fatty acids
106
describe lipid absorbtion
micelles diffuse to apical brush border where the lipids are released from the micelle and diffused down their conc gradient into the cell.
If fatty acid short = into bloodstream
rest = packaged into lipid carrying particles called chylomicron
chylomicrons move to basal lateral membrane and exit via exocytosis. too larger to enter vascular capilallries and are taken up by lacteals
107
how are glucose and galactose absorbed
sodium-dependent cotransporter called SGLT1
108
how is fructose absorbed
facilitated diffusion via gLUt 5 transporter
109
how are monosaccharides released from epithelial cell in small intestine into blood
via GLUT 2 transporters
110
how are amino acids absorbed
sodium-dependent transporters
111
how are dipeptides and tripeptides absorbed
hydrogen ion co-transporters
112
how are amino acids released from intestinal epithelium into blood
facilitated diffusion
113
how are dipeptides and tripeptides released into blood from intestinal epithelium
they diffuse out themelves
114
what is the function of bicarbonate present in pancreatic juice
neutralises chyme
115
How prevalent are eating disorders in the UK
approx 1.25million cases in 2022
25% of these are males
116
Describe Bulimia Nervosa
* Recurrent overeating
* Accompanied by attempts to compensate eating - overexercise or vomiting
* Not significantly underweight
117
Describe Anorexia Nervosa
* A significant low body weight
* Accompanied by persitant pattern of behaviours to prevent weight restoration
118
Describe binge eating disorder
* Frrequent and recurring episodes of binge eating without compensatory behaviours
119
Describe Avoidant and Restrictive Food Intake Disorder (ARFID)
* Abnormal eating or feeding that results in the intake of insufficient quantity or variety of food
* Significant weight loss/failure to gain weight/nutritional deficiencies/dependence on nutritional supplements or tube feeding
* Not concerned about body shape/weight
120
Describe other specified feeding or eating disorders (OSFED)
* Abnormal eating or feeding behaviours
* Dont fulfil diagnostic requirements for another disorder
* Symptoms result in significant damage to health
* distress impairment in personal/family/social/educational/occupational or other areas of functioning
121
what are the 3 subtypes of ARFID
1. Fear of consequences (chocking or being sick)
2. People with sensory sensitivity
3. Lack of interest in food
122
how prevalent are mental health disorders across the world
1 in 8 people
anxiety and depression are the most common
123
How can ATP be replenished
* anaerobic metabolism of CHO to lactate (glycolysis)
* aerobic metabolism of CHOfat and/or protein (in mitochondria)
124
What tissues are dependent on glucose
1. Erythrocytes (no mitochondria)
2. 2. Brain (fatty acids cant pass blood-brain barrier quickly)
125
4 Reasons for why some starches are slowly digested
* trapped in intact starch granules/plant cell wall structure
* resistant to amylase as 3D structure too tightly packed
* associated with dietary fibre - slows absorbtion/digestion as increases gut content viscosity
* CHO foods containing high levels of fat may have delayed gastric emptying
126
idea behind and calculation for glycaemic index
compares a certain amount og carbohydrate to an equal amount og glucose and seeing how quickly you absorb them
glycaemic index = area under curve over 2 hours for food containing 50g carbohydrate DIVIDED BY area under curve for 50g glucose MULTIPLIED BY 100
127
Plasma glucose concentration
tightly regulated and maintained between concentrations of 4-5mM (in fasted state). Can raise to 8-12 mM after a meal
128
Function of GLUTs 1-5
Sugar transport down concentration gradients by facilitated diffusion
GLUT 1,2,3,4: glucose
GLUT 3,5: fructose
GLUT 1,2,3: galactose
129
Functions of SGLT1 and 2
Sodium linked glucose transporter
Transport glucose against concentration gradient using energy provided by cotransport of Sodium. Required in intestine to absorb from lumen and kidney to reabsorb from filtrate
130
Major sites of expression of GLUTs 1-5
1. ubiquitous (all tissues)
2. liver, small intestine, kidney
3. brain, placenta and testes
4. skeletal and cardiac muscle, adipocytes
5. small intestine, sperm
131
Describe how GLUT 4 is different to the other GLUTs
Insulin responsive
The other GLUTs are on the plasma membrane
GLUT 4 is found in vesicles which move to the plasma membrane and fuse with it when insulin is present. Afterwards they are endocytosed.
132
What can you synthesise from plasma glucose
Pentoses
ATP
Fatty acids
Triglycerides
133
what catalyses phosphorylation of glucose
hexokinases I - IV
134
describe hexokinases I - IV
Hexokinases I - III
- expressed in all tissues
- has low Km
- is inhibited by G6P (feedback inhibition)
Hexokinase IV
- expressed by beta-cells of pancreas and liver
- has high Km
- enzyme synthesis regulated
135
function of phophofructokinase
Activity determines whether G6P from hexokinase/glucokinase used for glycolysis or other purposes
Inhibited by ATP and citrate (downstream products)
136
Describe glycolysis
used 2ATP and generates 4ATP and 2 NADH
phosphofructokinase is the commited step for glycolysis
NADH must be used so that NAD+ is replenished
- under aerobic conditions NADH can be used to make more ATP in mitochondria
- under anaerobic conditions get lactate formation and no more ATP
137
What happens to fructose in glycolysis
* converted to fructose-1-phosphate by fructokinase
* F1P is converted to DHAP and glyceraldehyde-3-phosphate
* DHAP and G3P are intermediates of glycolysis
138
what happens to galactose in glycolysis
converted to glucose-1-phosphate then G6P by a number of steps
139
Fates of pyruvate
* lactate (anaerobic)
* Pyruvate: acetyle-CoA (occurs in mitochondria by Pyruvate dehydrogenaseproduce CO2 and NADH and H+
* Aerobic: NADH and Acetyl-CoA used in TCA cycle)
140
what converts NADH to NAD+ in lactate production
Lactate dehydrogenase
141
What does pyruvate dehyrogenase enxyme require for its activity
Vitamins as co-factors such as thiamine
142
What is GTP
very similar to ATP
granosine instead of adenine
143
Difference between liver and muscle glycogen
Glycogen in muscle cannot be broken down back into glucose as it uses the glycogen itself, whereas liver simple stores it
144
What is synthesised in the pentose phosphate pathway
NADPH
(required for generation of lipids by reductive biosynthesis)
(required for reduction of glutathione (antioxidant))
Ribose 5-phosphate
(formation of nucleotides (DNA, RNA))
145
Process of Glycogenesis
Glucose-6P
-> Glucose-1P (via phosphoglutamase)
-> UDP-Glucose (via G1P uridyltransferase)
-> Glycogen
146
Process of glycogenolysis
Glycogen
-> Glucose-1P (via glycogen phosphorylase)
-> Glucose-6P (via phosphoglucomutase)
-> Glucose (via glucose-6-phosphatase)
147
Hormonal regulation of glycogen synthesis
Glucagon and Noradrenaline
- Increase glycogen phosphorylase activity rapidly
- Inhibit glycogen synthase activity rapidly
Insulin
- Increase glycogen synthase activity rapidly
- Inhibit glycogen phosphorylase activity rapidly
148
Define gluconeogenesis
the synthesis of glucose from a non carbohydrate (nonhexose) source
- Lactate
- Pyruvate
- Glycerol
- Certain amino acids
149
3 irreversible reactions in glycolysis
hexokinase/Glucokinase
Phosphofructokinase
Pyruvate kinase
150
How does the liver bypass irreversible reactions during gluconeogenesis
Hexokinase bypassed by glucose 6-phosphatase
PFK bypassed by fructose -1,6-bisphosphatase
pyruvate kinase bypassed by pyruvate carboxylase and PEPCK (phosphoenolpyruvate carboxykinase)
151
What can liver do that muscle cant to create glucose
Produce Glucose 6-phosphatase which acts as a reversible bypass to convert glucose 6-phosphate into glucose
152
Substrates for gluconeogenesis
lactate - converted to pyruvate first
glycerol - converted to DHAP (dihydroxyacetone phosphate) intermediate in glycolysis
Amino acids - converted into pyruvate or various in TCA cycle intermediates (depending on side chain)
153
Why acn you not use fatty acids for gluconeogenesis
Fatty Acids are metabolised into acetyl Coenzyme A which is then used by TCA cycle to make ATP. Here 2 CO2 are produced and so you lose the carbons on th fatty acids and they cannot be contributed to glucose carbons
154
How is gluconeogenesis stimulated in the liver
Glucagon decreases levels of glucokinase and increases G6Pase and PEPCK activity
It also rapidly inhibits PFK activity
and rapidly inhibits pyruvate kinase activity
Insulin inhibits all these actions and suppressed gluconeogenesis
