week 10 - disorders of the GI system Flashcards
What is the function of the digestive system?
To digest food from a high molecular weight to a low molecular weight.
To absorb substances across the GI tract wall
What is the tube wall of the entire GI system made of?
- Mucosa - made up of epithelium, its function is absorption and has gland cells for secretion
- Sub mucosal plexus - Has nerves to regulate the gut
- Smooth muscle - Circularly orientated structure
- Myenteric Plexus - Contains more neurones
- Smooth Muscle within Serosa - Longitudinally orientated structure
What are the 2 movements of the GI tract?
Rhythmic Segmentation
Propulsive Peristalsis
What is rhythmic segmentation?
Nonadjacent segments of intestine contract and relax alternately to mix the chyme
What is propulsive peristalsis ?
wave of contraction followed by wave of relaxation to move food down the GI tube
What are the 3 sphincters of the GI system and what are the functions of all 3?
- Lower oesophageal
2.Pyloric - Ileocecal
The function is to ensure food travels in one direction and to prevent reflux
Give a brief summary of the hormone gastrin ?
Gastrin is released by g cells in the stomach.
Stimulates motility and stimulates the release of acid in the stomach (response to food)
Give a brief summary of the hormone secretin in the GI system?
Secretin is secreted by S cells in duodenum when there is low pH in the duodenum
Give a brief summary of the hormone CCK in the GI system?
CCK is secreted by the intestines in response to fat/protein rich chyme.
It allows for the slowing down of gastric emptying so food can be digested.
Involved in satiety (feeling full) by feeding back to the brain to inhibit appetite
Give a brief summary of the hormone leptin in the GI system?
It is a hormone produced by fat cells.
If you have more body fat, you have more leptin.
Leptin travels from bloodstream to hypothalamus where it suppresses your appetite.
Therefore, if you have more leptin due to more body fat then you have less food intake
What happens if you have a leptin secretion deficiency?
Suffer from hyperplasia, obesity
Give a brief summary of the hormone ghrelin in the GI system?
Ghrelin signals hunger.
Made by endocrine cells of the GI tract.
It acts on receptors of the hypothalamus to signal hunger.
What can happen if you have high levels of ghrelin?
Can lead to Prader Willis syndrome - leads to a voracious appetite, obesity as the high ghrelin levels keep signalling hunger
Give a brief summary of the peptide YY3-36 in the GI system?
Produced by the stomach cells.
Reduces ghrelin secretion
Give a brief summary of the CB1 receptor in the GI system?
Has effects similar to cannabis
If it is activated to results in a reduction in satiety signals. Relaxation, pain reduction effects.
What are the 3 ways examine the GI tract?
- Endoscopy:
examines the upper respiratory tract - Colonoscopy:
Examines the lower GI tract - X-rays:
The patient swallows barium as barium allows clear visualisation of the GI tract as it is a contrast medium
What can happen if the hypothalamus is damaged as it plays a key role in the GI system?
Can result in very rapid weight gain.
Hypothalamus cam be damaged by surgery, radiation, aneurysm, head trauma etc
What else can disrupt the control system of the GI tract?
Endocrine disorders:
Cushings
Hypothyroidism
Pituitary disease/hypothalamic malfunction
PCOS
Drugs that interact with metabolism:
Corticosteroids
Some antidepressants/sedatives
Insulin
What are some causes of problems of the GI system?
Non modifiable causes:
Genetics
Modifiable causes:
Diet
Cirrhosis in the liver caused by alcohol
Travel resulting in woes/amoebas
Medical procedures like drugs/radiotherapy
What are the 3 classifications of GI disorders?
- Motility disorders
- Disorders of secretion
- GI manifestations of systemic disease
What are the symptoms of GI disorders?
Visceral pain
Dysphagia
Nausea/vomiting
GI bleeding
Dyspepsia
Anorexia-weight loss
Constipation/diarrhoea
How can vomiting be induced by the brain?
- The medullary vomiting centre stimulates the oesophageal muscle diaphragm to contract
- Stimulates the respiratory muscle to reflex stomach/gut contents.
This can all be activated by emotions, drugs, touch receptors in throat
What is oesophageal dysphagia?
It is when you have difficulty swallowing due to blockages within the oesophagus, inflammation, GORD.
Or caused by blockages that put pressure on the outside of the oesophagus like tumours etc
What is PRE oesophageal dysphagia?
Difficulty swallowing due to lack of control of muscles that are involved in swallowing caused by Parkinsons etc
What is GORD (gastroesophageal reflux disease)?
It is when the LOS (lower oesophageal sphincter) which usually prevents acid reflux by staying closed, opens which causes acid reflux back up the oesophagus, damaging the oesophagus causing GORD
How can you treat GORD?
You need to reduce acid secretion via proton pump inhibitors or histamine antagonists
Give a brief summary of Barretts’s oesophagus
What factors can lead to the development of GORD?
