W1 L1 - Intro To Gut Physiology And Function Flashcards
What’s pharmacokinetics (PK)
what the drug does to the body
what’s pharmacodynamics (PD)
what the drug does to the body
what does ADME stand for
Absorption
Distribution
Metabolised
Excretion
System involved in Absorption
GI tract
System involved in Distribution
Circulatory
Organ involved in Metabolised
Liver
Organ involved in Excretion
Kidneys
which route of administration is the most convenient and cost-effective
oral
Functions of the GI system (4)
- Digestion of food
- Absorption of nutrients and drugs
- Elimination
- Mechanical + chemical breakdown of food into small molecules to be absorbed into the circulatory system for distribution throughout body
4 Regions of the GI tract
- mouth
- oesophagus
- stomach
- small intestine
4 Accessory organs
- salivary glands
- liver
- gall bladder
- pancreas
3 Regions of the digestive system
- mouth
- oesophagus
- stomach
function of mouth
saliva breaks up food particles
function of oesophagus (1)
- transport of food to stomach
- entry to stomach via sphincter
function of stomach (3)
- secretion of gastric juices for chemical digestion
- mechanical break up the food
- mixing of food + gastric juices
2 types of transmucosal tablets
- sublingual
- buccal
By which 2 mechanisms are drug molecules released from mucosal membrane to blood vessel and describe them
- transcellular - through cell
- paracellular - between cells
What’s peristalsis
involuntary contraction and relaxation of longitudinal and circular muscles throughout the digestive tract
Role of the stomach in food and drug absorption (2)
- gastric juices - HCl (controlled by vagus nerve + hormone gastrin) and digestive enzymes
- initiates the digestion of proteins (pepsin)
Example of chemical digestion
HCl + pepsin
Example of mechanical digestion
peristalsis
Types of cells in gastric gland (5)
- surface mucous cell
- mucous neck cell
- parietal cell
- chief cell
- enteroendocrine cell
what do surface mucus cells and neck cells secrete
- bicarbonate
- gastric mucus (glycoprotein)
functions of gastric mucus (2)
- lubricates stomach lining
- protects stomach wall from pH
what do parietal cells produce
- HCl
- castle intrinsic factor
function of HCl in stomach (2)
- lowers pH to around 2
- pepsinogen splits into pepsin which then hydrolyses protein peptides into smaller peptides
function of intrinsic factor
- helps absorb B-12
What do chief cells release (2)
- pepsinogen
- gastric lipase
function of gastric lipase
Gastric lipase breaks down short + medium chain fats
Role of stomach in food and drug absorption (2)
- mucus coating - lubricates and protects epithelial surface against pepsin
- formation of chyme
what’s chyme
thick semi fluid mass of partially digested food formed in stomach/ small intestine
what’s gastric emptying
movement of food to small intestine
what delays gastric emptying and affects rate of absorption
presence of food in stomach
other factors that affect gastric emptying (7)
- volume of meal
- Kcal contents
- Fat content
- Protein content
- Liquid/solid state
- Sex
- Particular disease states
Parts of small intestine (3)
- duodenum
- jejunum
- ileum
role of small intestine (5)
- completes digestion of nutrients in chyme
- major site of absorption of different nutrients
- major site of absorption of orally administered drugs
- site of first-pass metabolism of drugs
- movement of food residues to the large intestine
small intestine is a major site of absorption due to…
- large SA and high perfusion (the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue)
- exposure to enzymes and solubilisers
- receives secretion from liver and pancreas
what makes SA of small intestine large
- highly convoluted, circular folds
- villi
- micro villi
Why is large surface area so important for drug absorption after oral administration?
large SA for
- passive diffusion
- paracellular and transport facilitated
what are enterocytes
- simple epithelial cells which line the inner surface of the small and large intestines
- contain metabolic enzymes
- site of intestinal first pass
where does blood perfusing the intestine go
liver via hepatic portal vein
where does drug go after passing through liver
- drug goes into systemic circulation
what’s coeliac disease (3)
- chronic autoimmune disorder of small intestine
- inflammation process triggered by consumption of gluten-containing food
- causes atrophy of villi in the small intestinal epithelium
Role of liver secretions
- xenobiotics metabolised
- secrets bile, enters duodenum via hepatic duct
- stored in gall bladder between meals
- important for digestion of lipids
role of pancreas secretions
- proteolytic enzymes (trypsin and chymotrypsin for protein digestion)
- lipase for lipid digestion
- HCO3- neutralises stomach acid
what does bile do
- breaks down fats into fatty acids which can be absorbed by digestive tract
amylase role
starch to disaccharide (maltose, lactose)
role of enzymes in small intestine epithelial cells
disaccharide to monosaccharide (glucose, galactose)
role of pepsin
peptide to peptide fragments
role of trypsin and chymotripsin
peptide fragment to a a (actively transported to epithelial cells)
what are lipids digested to
fatty acids
how are lipids digested
- Emulsification (bile salts) – formation of small lipid droplets
- Pancreatic lipase breaks down triglyceride to monoglycerides and fatty acids
- micelle formation for transportation of lipids
- lipid digestion completed in small intestine
role of large of intestine
- water + chyme absorbed from chyme
- little absorption of drug minerals
- mixing and propulsion of contents
- indigestible residue and liquid eliminates as faecal waste
role of bacteria in distal intestine
- ferment carbs and proteins escaping into absorbable energy
- ability to metabolise drugs and xenobiotics
what’s the gut-brain axis
- the network of nerves that connect your brain and gut and send signals back and forth
- brain influences GI physiology, motility, mucin production
- GI influences brain, behaviour and mood
