Gastrointestinal System Flashcards
What does the first law of thermodynamics state?
Energy can be neither created nor destroyed, only transferred
What does the body need energy for?
Contraction Accumulating molecules across concentration gradients waste disposal heat building and repairing
What is Gibbs free energy (-delta G)?
The difference in energy between the substrates and the product
If the product has more energy than the substrates, G is positive
Describe Gibbs in terms of positive and negative metabolism.
Negative G would be exergonic (giving off energy, i.e. breaking down ATP)
Positive G would be endergonic (i.e. if you want to MAKE ATP you need energy)
Is food breakdown exergonic or endergonic?
Exergonic, you are releasing energy
What does ATP consist of?
5-carbon ribose sugar
Adenine
3 phosphate groups
What type of chemical reaction occurs to release energy from ATP?
Hydrolysis removes the phosphate
How much ATP is typically turned over in a day for 1 person?
80kg
What processes give rise to Acetyl Co-enzyme A for glucose, fatty acids, and amino acids?
Glucose- glycolysis
Fatty Acids- beta-oxidation
Amino Acids- transamination, oxidative deamination,
What are the phases of Krebs?
Decarboxylation- Acetyl Co-A is condensed with oxaloacetate to form citrate, which is then decarboxylated into succinyl Co-A
Reduction- succinyl co-a aids in reducing NAD and FAD and will eventually form oxaloacetate
How many NADH and FADH2 molecules are reduced in one cycle of Krebs?
3 NADH
1 FADH2
They are then fed into the ETC
What is the purpose of the Electron Transport Chain?
To pump protons (H+) across the inner mitochondrial membrane, into the inter membrane space
How many electrons and protons are donated to the electron transport chain by NADH and FADH2?
NADH can donate 2 electrons, and 1 proton to ETC
FADH2 donates 1 electron and 1 proton
How do electrons move from 1 radox centre to the next?
Using either Quinone or Cytochrome C proteins
What happens to the electrons when they are passed to radox centre 4?
Donated to molecular oxygen to produce water
This is why oxygen is essential
How much ATP is created for each Acetyl Co-A enzyme entering TCA?
NADH yields 2.5 ATP
FADH yields 1.5
(3x2.5)+(1x1.5)= Total is therefore 10 ATP
What happens during glycolysis, and where does it occur?
In cytosol of cells
6 Carbon Glucose converted into 2, 3 carbon pyruvates
First stage- glucose converted into fructose 1,6-bisphosphate using 2 ATP
2nd Stage- 2 NADH and 4 ATP are produced while creating 2 pyruvates
What happens to pyruvate as it enters the mitochondria?
Acetyl dehydrogenase converts pyruvate into acetyl co-a by removing a carbon
This also produces NADH
How does the body store glucose, and what organ aids in this storage?
Glycogen formed by Liver
What enzyme is responsible for the breakdown of fats?
Triglycerides are broken down by lipase into fatty acids, which are then moved into the body
How are fatty acids carried throughout the body?
Albumin (most prolific plasma protein)
Where does beta oxidation of fatty acids occur?
Mitochondrial matrix
What reactions occur to allow fatty acid transport into the mitochondria?
1- Acyl CoA synthase adds acyl CoA to fatty acid, creating Fatty Acyl CoA which can move across outer mito membrane
2- CoA is removed in intermembrane space, and carnitine is added, creating fatty acyl carnitine which can then move across inner mito membrane
3- Once in matrix, carnitine is replaced by acyl to create fatty acyl coa, which can be metabolized.
How much energy do you yield in beta-oxidation of fatty acyl coa?
For every beta-oxidation, you get: 1 Acetyl CoA 1 NADH 1 FADH Acetyl CoA can then feed into Krebs (3 NADH, 1 FADH2)
What happens in the stages of protein breakdown?
Transamination- removal of amino acid R group, and adding it onto a keto acid (typically alpha-ketoglutamate), forming an oxaloacetate/pyruvic acid (alpha-ketoacid) and a glutamate.
Alpha-ketoacid can then be utilized in ketogenic reaction (forming fatty aids, or acetyl coa), or glucogenic reaction (forming glucose, or pyruvates) which can be fed into krebs.
Deamination- glutamate is oxidized using nadp, to form alpha-ketoglutarate (process releases ammonia) . Alpha-ketoglutarate will undergo further processes to yield oxaloacetate/glutamate which can be fed into krebs
All these reactions are reversible
What does it mean for an amino acid to be ketogenic of glucogenic?
It can form a fatty acid (leucine or lysine) or a glucose molecule after transamination and deamination
How can you calculate energy requirements for a person?
Basal Energy Expenditure
a.k.a. basal metabolic rate
What structures form a triglyceride and how does it different from a phospholipid?
Glycerol backbone with 3 fatty acids
Phospholipid has glycerol, 2 fatty acids, and a phosphate group that has been modified with an alcohol
What are monosaccharides?
Glucose
Fructose
Galactose
How are disaccharides formed? Name 3 common ones as well as their monomers
Monosaccharides joined by glyosidic bond
Common; Sucrose (glucose + fructose), maltose (glucose + glucose), Lactose (glucose + galactose)
What are 2 common polysaccharides and how are they formed?
Starch, formed from amylose (alpha 1,4 glyosidic bonds) and amylopectin (alpha 1,4 glycosidic bonds with some alpha 1,6 glycosidic bonds)
Fibre- beta 1,4 links, cannot be digested
What is amylase and where is it produced?
Production: parotid, sublingual, and submandibular salivary glands as well as in the pancreas
Begins break down of carbohydrates, while moistening food
What is lingual lipase and where is it produced?
Production: parotid, sublingual, and submandibular salivary glands
Begins break down of lipids, while moistening food
What is the role of chief cells and where are they found?
Secrete pepsinogen (inactive ) for protein breakdown, which is converted to active pepsin form by acid Found below base of gastric mucosal pit
What is the role of parietal cells and where are they found?
Secrete hydrochloric acid which denatures proteins and activates pepsinogen (by opening and cleaving it)
Found in the neck of the gastric pit
What is an endopeptidase?
Cleaves the ends of peptide bonds
What is a zymogen?
An inactive enzyme, also called proenzyme
What is the pancreas responsible for in digestion?
Exocrine: secretes pancreatic juice consisting of alkali substances, like bicarbonate (inactivates pepsin and adjusts pH to optimal level (alkali)), water and enzymes for digestion into duodenum
Endocrine: insulin and glucagon secretion
What proteolytic and non-proteolytic enzyme are released via the pancreas?
Proteolytic (all listed released as zymogens): Trypsin Chymotrypsin Carboxypeptidase Elastase Non-proteolytic: Alpha-amylase Lipase Ribonuclease Deoxyribonuclease Phospholipase
What is the role of bile and what produces it?
Produced by liver, released by the gallbladder
Emulsifies fats so they can be used, solubilizes them for transport
Bile salts aid in absorption
How are bile salts formed?
Bile acids derived from cholesterol
Synthesized in hepatocyte into cholic acid or Chenodeoxycholic acid, which are conjugated with either glycine or taurine
Amphipathic (amino acid conjugate is hydrophilic, cholesterol portion is hydrophobic)
What is the duodenum responsible for?
Duodenum
-Chyme neutralized
-Mix secretions
-Absorption (minimal)
More Digestion:
-produces more enzymes for digestion (enterokinase (protease that activates trypsin which can activate all other proteolytic zymogens))
-Brush border enzymes (not free, tethered to plasma membrane, disaccharides and peptidases that cleave peptides and breakdown carbohydrates further)
What is the jejunum responsible for?
Completing breakdown
Nutrient absorption
What is the ileum responsible for?
Nutrient absorption
What is starch broken down into when met by alpha amylase in the mouth, and further enzymes in the small intestines?
Maltotriose, Maltose, and Dextrose
In duodenum: Brush border breaks down disaccharides (using maltase, lactase, and sucrase)
Where does most lipid digestion happen? Include enzymes
Duodenum
Pancreatic Lipase breaks down lipids into monoglycerides and fatty acids
Phospholipase digests phospholipids into lysolectithen and fatty acids
What are chylomicrons?
They are formed from larger (>12 carbons) fatty acid micelles, and proteins.
They enter the lymphatics capillaries (lacteals) to thoracic duct where it is emptied into the blood stream
Small micelles move directly via exocytosis into the capillaries.
How are monosaccharides absorbed?
Glucose and Galactose- SGLT1- sodium dependent co-transport (sodium is moved into cell with glucose and galactose)
Fructose- Glut 5- facilitated diffusion across apical membrane
On basolateral membrane all use glut 2 transporter
How are peptides transported from the lumen of the GI to the capillaries?
Sodium-dependent amino acid co-transporters move amino acids through apical surface with sodium.
Di and Tri are co-transported with hydrogen, and further digested within the cell by peptidase.
Basolateral transport is facilitated diffusion into capillaries
What are some signs of bulimia nervosa?
Low potassium (caused by purging)
Decaying enamel
Binge eating accompanied with compensatory behaviours
Patient preoccupied with weight
What are some treatments for bulimia nervosa?
Offered guided self help
Considered for individual cognitive behavioural focused (eating centre focused)
Think about relapse prevention
Involve other family members in support-Family (especially for young patients) Therapy over 6 months
What is cognitive behavioural therapy?
Thoughts, behaviours, physical reactions, moods, and situations are all intrinsically linked.
If we change one, like restricting food (behaviour), in turn it will change physical reaction
This therapy looks to address these factors and track what is going on to shape a better mental state.
What is binge eating disorder?
It is essentially binging; Eating until uncomfortably full Eating more quickly than usual Eating a lot when not hungry Eating alone because embarrassed Feeling bad/guilty after eating
What is management for binge eating disorder?
Self help offered
Offering group based CBT
What is the criteria for anorexia nervosa?
Patient has very low body weight
Preventing any weight gain
Weight is important to the person’s self-evaluation
May have other signs (Russell’s Sign (skin lesions on hand))
What is the management for anorexia nervosa?
CBT-ED shown to be most useful
Family therapy if acceptable
What is Avoidant / Restrictive Food Intake Disorder?
Abnormal eating that results in insufficient intake of food
Significant weight loss, impact on functionality
Pattern of eating doesn’t reflect concerns about body weight and shape (making it quite different from anorexia)
What are Other Feeding Disorders?
When a person doesn’t strictly fit into the boxes of one given disorder.
What is MARSIPAN?
Management of Really Sick Patients with Anorexia Nervosa
Arose due to inefficient treatment (i.e. NICE) for very severe patients, and issue with things like re-feeding, non-adherence to nutritional treatment, and under-feeding syndrome.
What are the layers, moving from lumen outwards (becoming more deep), of the alimentary canal?
Mucosa (epithelium, Lamina Propria, and Muscularis Mucosa), then
Submucosa (dense irregular connective tissue, blood vessels, nerve)
Muscularis Propria (inner circular and outer longitudinal smooth muscle layers)
Adventitia/ Serosa (Adventitia found in upper oesophagus in chest and thorax, and ascending/descending colon and rectum, everywhere else is serosa)
How does the epithelial layer change throughout the alimentary canal moving from mouth to colon?
Oesophagus- stratified squamous
Stomach- simple columnar epithelium
GI- Simple columnar epithelium with villi
Colon- simple columnar epithelium
What are some characteristics specific to each region of the small intestines?
Duodenum has pancreatic and liver secretions
Jejunum has the crypts of the gland of Lieberkühn (dips in mucosa)
Ileum has peyer’s patches (immune system, collection of lymphoid follicles preventing harmful bacterial growth)
How does the muscularis mucosa change within the oesophogus?
top 1/3- skeletal
middle 2/3- skeletal and smooth
bottom 3/3- smooth
What organs are found in the right and left hypochondrium’s of the abdomen?
Liver
3- spleen and stomach
What organs are found in the epigastric of the abdomen?
duodenum, liver, gallbladder, pancreas and stomach.
What organs are found in the left and right lumbar regions of the abdomen?
4-ascending colon, kidney
6-descending colon, left kidney
What organs are found in the umbilical region of the abdomen?
stomach, head of pancreas, duodenum, transverse colon, lower aspects of right and left kidneys
What organs are found in the right and left ileac fossa regions of the abdomen?
7- caecum, appendix, part of ascending colon
9- sigmoid colon, descending colon,
What organs are found in the suprapubic of the abdomen?
Bladder, uterus, prostate, parts of intestine (i.e. ileum)
Describe the anatomical features of the stomach, moving from superior to inferior.
Cardiac Sphincter Fundus (where air collects) Cardia (beside the heart) Body (forms bulk) Pylorus (end) Pyloric Sphincter Curvatures of stomach; greater (where fatty tissue attaches) and lesser
What is Pyloric stenosis, and how does it typically present?
Typically in new born babies
Sphincter is thicker and narrower, reducing food movement and secretions from the stomach into the duodenum.
Typically presents as vomiting with no bile.
What are rugae?
Folds in stomach that increase surface area.
Allow for distention and reduction when little food.
What are the layers of the muscular propria in the stomach?
Innermost Oblique
Inner Circular
Outer longitudinal
What cells are typically found within the mucosa of the stomach?
Chief Cells release pepsinogen Endocrine Cells- produce gastrin (which stimulates parietal cells) Parietal Cells (secretes hydrochloric acid which will break down pepsinogen to active pepsin) Mucous cells (secrete mucous to protect mucosal lining)
Where are villi found, and how much do they increase size?
Increase by 30x
Found primarily in the jejunum and ileum, and lesser in the duodenum.
What are some important features of the duodenum?
12 finger breadths long
Villi
Receives chyme
Brunner’s Glands (secrete bicarbonate (alkaline) to reduce acid)
Receives Common Bile Duct-controlled Sphincter of Oddi, secretions move through Major duodenal papilla (bile secretions for fat absorption, pancreatic juices)
What specializations are present in the small intestines?
Plica- folds seen with naked eye
Lymph nodules
Mucosa with Epithelium forming brush border and lacteals, arteries and veins
What is found deep to the serosa of the small intenstines?
Mesentery - holds things in place
Where is the liver and what does it do?
Largest gland of body (1.5kg)
Right hypochondrium
4 lobes
Produces bile which is stored in gallbladder (leaves via cystic duct)
Detoxification and processes everything,
Regulates blood glucose
synthesizes protein (clotting factors)
Activates hormones (i.e. insulin)
Drug metabolism
Receives blood from hepatic artery from celiac trunk, as well as blood from hepatic portal vein (75% of deoxygenated blood into liver)
Common hepatic duct from right and left hepatic duct carry bile to gallbladder
What anatomical features surround the start and end of the colon?
Caecum and anal canal
Why is the caecum important?
It is a reservoir for chyme from terminal ileum
Contains appendix
How is the large intestines sectioned? Include distinctive levels and quadrants.
Ascending- from caecum to hepatic flexure
Transverse- from hepatic flexure to splenic flexure. Least fixed, and intraperitoneal
Descending- from splenic flexure, retroperitoneal, located anteriorly to left kidney.
Sigmoid colon- 40 cm long, in left lower quadrant of abdomen. From left ileac fossa to level of 3rd sacral vertebra.
What are some specialized features of the large intestines?
Teania coli- incomplete longitudinal bands on outer portion of ascending, transverse, and descending colon
Haustrations- ring like pouches, or contractions of circular muscle
Appendices Epiploicae- pouches of peritoneum (fatty tags) on transverse and sigmoid colon. Not on rectum
What specialized cells are found within the colon
Goblet cells- mucous secretion
Describe the arterial blood supply of GI.
Abdominal aorta divides into 3 main branches Coeliac artery (foregut)- oesophagus, stomach, liver, spleen, first 1/2 of duodenum Superior Mesenteric Artery (midgut)- Last 1/2 of duodenum, jejunum, ileum, caecum, appendix, ascending colon, first 1/2 or 2/3 of transverse colon Inferior Mesenteric Artery (hindgut)- Last 1/3 of transverse colon, descending colon, sigmoid colon, rectum
What is the venous drainage for the colon?
Inferior Mesenteric vein- drains hindgut
Superior Mesenteric vein- drains midgut
IMV meets with splenic vein, moves laterally to meet SMV, forming portal vein
Portal vein drains unpaired abdominal organs (i.e. spleen, gut)
Portal vein moves into liver, detoxified, blood then moves out through hepatic vein to the heart.
Describe the venous return of our lower limbs.
Femoral vein collects blood from lower limbs
When crossing passed groin, becomes external ileac vein.
External and internal ileac veins join to form common ileac vein
Left and right common ileac vein join to form inferior vena cava
Right gonadal vein directly joins into IVC, left gonadal vein joins left renal vein, and both renal veins join IVC. Hepatic vein also joins.
What is dysphagia?
Difficulty swallowing
