What is digestion?
Process of breaking down macromolecules to allow absorption
What is absorption?
Process of moving nutrients and water across a membrane
How can digestion take place?
Mechanically: Chewing, gastric churning, peristalsis OR enzymatically
What happens after ingestion?
Either direct excretion/absorption OR digestion
What are the components of the GIS?
Parotid gland, sublingual gland, submandibular gland, oesophagus, liver, stomach, gall bladder, pancreas, duodenum, jejenum, ileum, appendix, ascending colon, descending colon, sigmoid colon, rectum, anus
What are some diseases specific to each part of the GI system?
Main: LIVER - hence hepatology
What is disease burden - the checklist?
Burden to the patient, economy, population, society
What are the different classes of symptoms that can be caused by GIT diseases?
General, Upper GI, hepatobiliary, mid GI, lower GI
What are some general symptoms of GIT diseases?
Anorexia, weight loss, anaemia
What are some UGI symptoms?
Haematemesis, melaena, N and V, Dysphagia, odynophagia, heartburn, Acid regurgitation, belching, chest pain, epigastric pain
What are some hepatobiliary symptoms?
RUQ pain, Biliary colic, Jaundice, Dark urine, pale stool, abdominal distention
What are some mid GI symptoms?
Abdominal pain, steatorrhea, diarrhoea, abdominal distention
What are some lower GI symptoms?
Abdominal pain, bleeding, constipation, diarrhoea, incontinence
Why is incontinence important?
A patient won't want to share that they are incontinent - embarrassing
What are the 4 places that show signs due to GIS disease?
General, hands, abdomen, anus and rectum
What signs are generally visible?
Cachexia, obesity, lymphadenopathy, anaemia, jaundice
What are some signs on the hands?
Koilinychia, leuconychia, clubbing, dupytrens contracture, tachycardia, tremor
What are some signs of the abdomen?
Organ enlargement, mass, tenderness, distension
What are some signs of the anus and rectum?
Haemorrhoids, fistula, fissure, rectal masses or proctitis
What investigations can be used for the GI systems?
History, Basic physical examination, Haematology/biochem/microbio (blood test, tumour markers, urea, etc), procedures (x-ray, mri, colonoscopy)
What is the biggest specific killer of people in UK, wrt GID?
What is the biggest portion of systemic cancers in the UK?
What position is GI most likely to cause problems and lead to death?
4th (don't need to know but to appreciate)
What is happening to the trend of alcoholic liver disease vs. liver cancer?
Alcoholic liver disease is high among younger populations, and decreases with age BUT liver cancer increases with age, affecting the older generations
In which sex, is alcoholic liver disease and liver cancer more common?
Which GI cancers are common?
Colorectal (2nd), Prostate(3rd), Oesophagus, pancreas, stomach (6th), liver (13th) [oral cancer commonish]
What are some prevalent inflammatory conditions that are burden?
Ulcerative colitis (1/500)
Crohn's disease (1/1000)
Coeliac disease (1/87)
Gastro-oesophageal reflux disease
How is ulcerative colitis treated and what causes it?
Treated: colectomy, Cause: thought to be autoimmune
What causes coeliac disease?
What are some pancreatic conditions?
What is acute pancreatitis?
Blockage of the pancreatic duct causes back up of pancreatic enzymes, causing severe inflammation - mild->life-threatening
What is chronic pancreatitis?
Permanent damage to pancreas, alcohol excess is the main cause and can greatly impair quality of life
What kind of infections can occur in the GIS?
Bacterial - Helicobacter pylori (nausea, bloating, weight loss), E. coli (Nausea, diarrhoea, cramps)
Virus - Norovirus (N, V, D)
How does H. pylori affect people globally?
Infects around 60% of people - 85% have no problems, 14% peptic ulcers, 1% gastric adenocarcinoma/lymphoma
What are GI disease risks based on?
Mainly on environment - energy intake, staple foods
What are the different effects on the economy from GID?
Mortality and lost years, absence from work, morbidity, NHS prescription costs, QALY, DALY
What do QALY and DALY mean?
Quality and Disability adjusted life years
What kind of healthcare costs are there (GI burden)?
In-patients, out-patients, primary care, community health and social care
What kind of other costs are there (GI burden)?
NHS costs and non-working costs
What are the costs of dyspepsia?
Only 2% consult GPs and 40% of adults suffer from it - OTC drugs
What is a cost effective screening programme in the UK - to do with GID?
Bowel cancer screening
What are the 4 detrimental social aspects of GID?
Dietary limitation (intolerances), flatulence (sound and smell), treatment (smell/slight), incontinence (soiling)
Which GI cancer has the poorest survival rate?
What is the most common cause of GI-related death in a 75 year old man?
What is the layer plan of the gut wall?
Mucosa (epithelium, lamina propria, muscularis mucosae), Submucosa (connective tissue w/nerve plexus), Muscularis (smooth muscle w/nerve plexus), serosa/adventitia (connective tissue +/- epithelium)
What is the structure of the oesophagus?
Starts at C5, passes through the thorax into the abdomen, close to the heart, laryngeal nerves
What is the purpose of the oesophagus?
Conduit for food, drink and swallowed secretions from pharynx to stomach
What are some complications of the place where the oesophagus is placed?
Close to the pericardium, so a rupture could lead to acidic contents/bacteria entering into the thorax and causing infections; also close to the recurrent laryngeal nerves, which could be damaged during surgery
What is the structure/function relationship of the oesophagus' epithelium?
It is non-keratinising, stratified squamous - very robust, as needs to protect underlying structures and deal with wear and tear - secrete mucous to help with bolus lubrication
What is the structure/function relationship of the oesophageal sphincters?
Upper/lower oesophageal sphincters - tonically active (need swallowing to open)
LOS needed to stop negative pressure drawing up the acid from stomach and UOS needed to close so breathing can occur
What is the structure of the oesophagus muscles?
Skeletal, transition between skeletal/smooth and then smooth - there is NO VOLUNTARY CONTROL
What is the process of swallowing and how is it controlled?
The swallowing centre in the brain sends a signal to open both sphincters, and when the bolus passes the UOS, it closes. The LOS stays open until the bolus has entered the stomach
How does peristalsis occur?
Smooth muscle - particularly circular muscle - immediately above bolus is contracted, below bolus is relaxed - longitudinal helps, but mainly circular
What are secondary peristaltic waves?
If the bolus hasn't reached the stomach and it is detected by the oesophagus, another wave of contraction is sent down the oesophagus, so the bolus can reach the stomach
What is the gastro-oesophageal junction?
Joining of oesophagus with stomach - where the LOS is to prevent reflux (prevented by diaphragm)
What is the LOS?
It is the diaphragm, assisting circular muscle at lower end of oesophagus
How does the level of the GOJ help to prevent reflux?
Negative pressure in thorax vs positive pressure in stomach would lead to acid being drawn up the oesophagus
What is a histological feature that can be seen at the GOJ?
Epithelial transition from stratified squamous to simple columnar AND gastric folds (rugae) are present in the stomach
What is the purpose of the epithelial transition in the GOJ?
Change in function as in stomach it has to be more secretory rather than protective
Why are the gastric folds present in the stomach?
Allows for huge changes of surface area - to expand and contract as required
How does belching work?
The OS are both opened and the pressure in the oesophagus causes the air to be pushed out - not pushing out by the stomach
What is the function of the stomach?
Break down food into smaller particles; holds food and releases at steady rate into duodenum; kills parasites and certain bacteria
What are the types of cell in the stomach lining?
Simple columnar, which invaginate into mucosa - tubular glands
What are the regions in the stomach and what do they produce?
Cardia and Pyloric regions - Mucus
Body and fundus - Mucus, HCl, pepsinogen
Antrum - Gastrin