Gastrointestinal tract Flashcards
How many portions of fruit or veg should you eat a day
5
Whats happening in energy intake (EI)
fat
alcohol
carbohydrate
protein
what is happening in energy expenditure (EE)
basal metabolic rate (BMR)
Thermogenesis
Physical activity
What BMI is classed as underweight
<18.5 kg/m^2
What BMI is classed as normal
18.5-24.9 kg/m^2
What BMI is classed as overweight
25-29.9 kg/m^2
What BMI is classed as obese
30-39.9 kg/m^2
What BMI is classed as morbidly obese
> 40 kg/m^2
What are some obesity contributors
endocrine disorders psychological cultural psychiatric disorders environmental disorder environmental factors genetics medications
What are some generic obesity treatment options
lifestyle changes
pharmacotherapy
bariatric surgery
What are things to do with lifestyle changes for managing weight
reduced energy diet
increased physical activity
What things does pharmacotherapy do
appetite suppressants
Fat absorption inhibitors
What things does bariatric surgery do
gastric band
gastric bypass
sleeve gastrectomy
Symptoms of malnutrition
loss of appetite weight loss (unintentional 5-10% of bodyweight in 3-6 months) tiredness reduced ability to perform normal tasks reduced physical performance altered mood poor concentration poor growth in children
Define digestion
processes by which foodstuffs are degraded to produce smaller molecules that can be absorbed
Define absorption
processes by which nutrient molecules are absorbed by cells that line the GI tract and enter the bloodstream
Define protection
the processes by which lining of the GI tract is protected from damage during digestion of foodstuffs
Layers that make up the GI tract (from middle to outward (abdomen))
mucosa epithelium lamina propia muscular mucosae submucosa muscular externa serosa
What is GALT
gut associated lymphoid tissue
What are lymph nodes or GALT important in
recognising foodstuffs and protecting against infection
Where are glands in submucosa located
at the bottom of the oesophagus and bottom of the small intestine (duodenum)
What are the submucosa glands in the duodenum known as
brunners gland
What is the myenteric plexus also known as and where is it located
Auerbach’s plexus
located in submucosa throughout the GI tract
What is the submucosal plexus also known as and where is it located
meissners plexus
found in small and large intestine
What are the 5 major sites of GI secretions
salivary glands gastric glands exocrine pancreas liver-biliary system small intestine
Total amount of GI secretions a day
6-7L a day
What do GI secretions contain
enzymes, ions, water, and mucus
Function of GI secretions
breakdown large compounds, regulate pH, dilute and protect
What does endocrine do
release of a transmitter into blood for delivery to distant target cell
What does paracrine do
release of a transmitter from a sensor cell to affect adjacent target cells without entering the blood or activating neurones
What does neuronal refer to
electrical signalling via neurons
What cells produce gastrin and where are they located
G cells located in the stomach
What cells produce cholecystokinin (CCK) and where are they located
I cells located in the small intestine
What cells produce secretin and where are they located
S cells located in the small intestine
What cells produce glucose-dependent insulinotropic peptide (GIP) and where are they located
K cells located in the small intestine
What cells produce somatostatin and where are they located
D cells located in the stomach, pancreatic islets and small intestine
Three phases of GI control
cephalic
gastric
intestinal
What is the cephalic phase
sight, smell, taste and chewing
What is the gastric phase
distention and acidity
What is the intestinal phase
distention, acidity and osmolarity
Three functions of motor activity
non propulsive movements (segmentation)
peristaltic movements
reservoir function
What are the two types of muscle contraction and how long do they typically last
phasic (seconds)
tonic (minutes-hours)
What are sphincters
specialised circular muscles that separate two adjacent compartments of the GI tract
What does antegrade mean
regulate forwards
what does retrograde movement mean
reverse movement
Location of sphincters
upper oesophageal sphincter (UES) lower oesophageal sphincter (LES) pyloric sphincter iliocecal sphincter internal and external anal sphincter sphincter of odd
What happens in the swallowing reflex
food goes to touch receptors (back of tongue) which goes to the medulla and lower pons
This stimulates the vagus nerve to the oesophagus and cranial nerves to the pharynx and upper oesophagus
3 Phases of swallowing
oral phase (voluntary phase)
pharyngeal phase
oesophageal phase
What is the oral phase of swallowing
tongue presses food against hard palate
bolus is forced into the pharynx and stimulates touch receptors
What happens in the pharyngeal phase of swallowing
soft palate elevates
epiglottis closes trachea
upper oesophageal sphincter relaxes
What happens in the oesophageal phase of swallowing
upper oesophageal sphincter closes
peristalsis starts
What is peristalsis
the sequential contraction of ring of muscle
What happens during vomiting
forced inspiration occurs against a closed epiglottis
diaphragm is lowered
decreases intrathoracic pressure
as a consequence intraabdominal pressure increases
reflex relates the upper oesophageal sphincter
Describe peristalsis in the stomach
contractions begin in the corpus and travel towards the pylorus (propulsion)
they increase in force and velocity as they approach the gastroduodenal junction
mixing (grinding) occurs mainly in the antrum
retropulsion is very effective at mixing and breaking down gastric content
Non-propulsive movements motility in the small intestine
most frequent type of movements in the small intestine
caused by rhythmic contraction and relaxation of the muscular externa
effectively mixes chyme and brings digested nutrients into contact with the mucosal surface
Peristalsis in the small intestine
occurs at low frequency
caused by contraction of successive sections of muscularis externa
propels chyme for a short distance, allowing time for digestion and absorption
Functions of colonic contractions in the large intestine
mixing the chyme, to improve the absorption of water and salts from the colon
kneading the semisolid contents
moving the contents towards the anus (5-10cm an hour)(termed segmentation)
mass peristalsis in the large intestine
specialised type of movement
1-3 times a day, move the colonic contents towards the anus
What happens in defaecation
distention of rectum
relaxation of internal and external anal sphincter
contraction of abdominal wall muscles and relaxation of pelvic wall muscles
flexure of hips and descent of pelvic floor
Four functions of liver and gallbladder
metabolism
synthetic function
biliary system
storage
What does the liver store
glycogen
Another word for aminotransferases
transaminases
What is ALT
alanine aminotransferase
What does raised levels of ALT suggest
sign of hepatocellular damage
Where should aminotransferases be
in hepatocytes not bloodstream
What is the synthetic function of the liver
albumin
clotting factors
acute phase proteins - CRP (C-reactive protein)
What percentage does albumin make up of plasma proteins
50%
Reference range of albumin
35-45g/L
What is albumin a main factor in
maintaining oncotic pressure
Causes of hypoalbuminaemia
liver disease
nephrotic syndrome
malnutrition
burns
What does low albumin cause
peripheral oedema
What is cholestasis
malabsorption of vitamin K
What are bile acids synthesised from
cholesterol
Salivary secretion from parotid gland
serous (watery) secretion rich in ⍺-amylase
Salivary secretion from submandibular and sublingual glands
seromucous secretion
3 roles of stomach in digestion
reservoir - gastric motility
digests proteins - pepsins
essential for the absorption of vitamin b12-intrinsic factor
Composition of gastric secretions
HCl, pepsins, intrinsic factors, mucus and HCO3-
What are ECLs
entrochromatin like cells
What do ECLs secrete
histamine
What do mucus neck cells secrete
mucus
optimal pH of pepsins
<3
Functions of HCl
promotes the activation and activity of pepsins
kills and inhibits microorganisms
stimulates secretions in the small intestine
What regulates mucus and HCO3-
acetylcholine and prostaglandins
describe the secretions from the pancreas
1.5 litres a day
pH: 7.8-8.4
composed of salts and enzymes
Describe the secretions from the liver
0.5 litres a day
pH: 7.4
composed of bile acids, cholesterol and phospholipids
Describe the secretions from the small intestine
1 litre a day
pH: 7.6
composed of mucus enteropeptidase, salt and water
Endocrine pancreatic secretions
insulin and glucagon
exocrine pancreatic secretions
salts and water, enzymes
Functions of pancreatic juice
salts and water (HCO3-, NaCl, H2O): create the right environment for enzymes to work
enzymes: important for digestion of all major classes of foodstuffs
What do enzymes are in pancreatic juice and what do they do
proteases- digest proteins
lipases- digest fats
⍺-amylase - digest carbohydrates
Where are secretions of the liver specifically secreted from and where are they stored
secreted from hepatocytes
stored in gallbladder
what do bile acids, cholesterol and phospholipids form
micelles for the absorption of fatty acids
What does the enterohepatic circulation do
control of bile synthesis and secretion
what happens if blood glucose drops below 2mM
brain becomes starved of fuel
What do humans synthesise glucose from
pyruvate, glycerol and amino acids
what is gng
gluconeogenesis
Where is the main site for gng
the liver
Can we use lactate to synthesise glucose
yes
What does GNG cost
4 ATP, 2 GTP, and 2 NADH per glucose molecule
What is glycogen synthase activated for
to convert excess glucose into glycogen
What is glycogen phosphorylase activated for
to convert glycogen into glucose-1-phosphate
what is glycogen synthase activated by
glucose and glucose-6-phosphate
What is glycogen phosphorylase activated by
AMP (Adenosine monophosphate) and Ca2+ in muscle
What hormones are glycogen synthase and glycogen phosphorylase under the control of
insulin, glucagon and adrenaline
When does homeostasis occur
when metabolite concentrations are at a steady state
Average half-life in days of following tissues: liver, kidney, heart, brain, muscle
liver-0.9 kidney-1.7 heart-4.1 brain-4.6 muscle-10.7
what is hexokinase inhibited by
glucose-6-phosphate
what is phosphofructokinase inhibited by
ATP
What does AMPK do generally speaking
shifts metabolism away from energy consuming synthetic pathways
What does AMPK do in extra hepatic tissues
shifts the metabolism towards the use of fatty acids
What does AMPK do in the liver
triggers GNG to provide glucose for the brain and slows synthetic pathways
What does AMPK do in the brain
stimulates feeding behaviour to provide more dietary fuel
What is AMPK activated by
AMP, by the sympathetic nervous system, exercise and by peptide hormones produced in adipose tissue
Where does one-third of our energy needs come from
dietary triglycerides
What are fats used for
long-term energy needs
what’re glucose and glycogen used for
short-term energy needs
Where are dietary fatty acids absorbed
in the vertebrate small intestine
What do intestinal lipases do
degrade triglycerides
what are chylomicrons
the product of triglycerides and cholesterol and apolipoproteins
What do chylomicrons do
move through lymphatic system and bloodstream to tissues
how are fatty acids transported into the mitochondria
the carnitine shuttle
Stages of the carnitine shuttle
stage 1: β oxidation. Fatty acids are oxidised two carbons at a time and combine with CoA to form acetyl-CoA, and high energy electrons in the form of NADH and FADH2
Stage 2: Acetyl CoA enters the citric acid cycle and is used to form NADH and FADH2
Stage 3: the high energy electrons in NADH and FADH2 are used to synthesise ATP in oxidative phosphorylation
What three ketone bodies are produced in the liver
acetoacetate, β-hydroxybutryate, and some acetone
What are ketone bodies a major fuel source for
the heart, skeletal muscle and kidneys
What vitamins are fat soluble
A, B-12, D,E,K
Function of vit A
rhodopsin, retinoic acid/antioxidant
Function of vit C
collagen synthesis/antioxidant
Function of vit D
calcium absorption/antioxidant
Function of vit E
Mixed/antioxidant
Function of Vit K
formation of blood clotting factors/coenzyme
Function of thiamine B1
precursor of dehydrogenase cofactor
Function of riboflavin B2
precursor of FAD/FADH2
Function of niacin B3
precursor of NAD and NADP
Function of vit B6
cofactor in amino acid metabolism
Function of biotin
cofactor of carboxylases
Function of pantothenic acid (formation of B3 and B5)
precursor of CoA
Function of folic acid
DNA synthesis, etc.
Function of cobalamin B12
DNA synthesis, etc.
