Upper GI Disorder: Gastric system Flashcards
What are examples of some GI tract disorders?
Gastroesophageal Reflux Disease (GORD) Peptic Ulder Disease (PUD) Duodenal Ulcer Nausea Emesis IBS Diarrhoea Constipation
What are the main sites for therapeutic intervention in GI system?
Stomach Oesophagus Mouth Pancreas Liver Large intestine Small intestine
What are the accessory organs within the mouth?
Salivary Glands
Teeth
Oral cavity
What is the function of the mouth?
Ingestion and fragmentation of food
What is oral ulceration?
Break in oral epithelium, which exposes the nerve endings
What can cause oral ulceration?
Chemical/physical injury Infections Drugs Malignancy Systemic disease
What is Stomatitis?
Inflammation of the lining of any soft tissues in the mouth
What can cause Stomatisis?
Poor oral hygiene Poorly fitted dentures Heart burns Drugs Allergy Infection
What is Leukoplakia?
Painless white patches on the side of the mouth
What is Dysphagia?
Difficulty swallowing
What is the function of the Oesophagus?
Contracts rhythmically to propel food towards stomach
What is the function of the Upper Oesophageal Sphincter (UOS)?
It prevents air entering the oesophgus and oesophgopharyngeal reflux
What is the function of the Lower Oesophageal Sphincter (LOS)?
Prevents gastroesophageal reflux. The high intraluminal pressure keeps it closed until food needs to be dumped.
What are some dysfunctional physiologies and diseases of oesophagus?
GORD- Obesity, Medication, Spicy, acidic, Smoking
Hiatal hernia
Motility disorders
What are some examples motility disorders?
Achalasia
Diffuse oesophageal Spasm
Hypercontraction
Ineffective oesophageal Motility
What is Achalasia?
Inadequate LOS relaxation
What is Diffuse oesophageal Spasm?
Uncoordinated contraction
What is Dyspepsia?
Upper GI tract
Includes heartburn, abdominal discomfort, eructation, nausea
What is Peptic ulceration?
Benign lesion of gastric/duodenal mucosa at a site where mucosa is exposed to acif and pepsin
What are symptoms of dyspepsia?
Epigastric pain
Commonly vommitting
How is GORD caused?
Exposure of ‘unprotected’’ oesophageal epithelium to acid
Transient LOS relaxation in absence of swallowing
What are the three distinct types of GORD?
Non-erosive reflux disease
Erosive oesophagitis
Barrett’s oesophagus
What is Non-erosive reflux disease?
Heartburn
What is Erosive oesophagitis?
Acute inflammatory response
What is Barrett’s oesophagus?
Metaplasis of mucosa
Which one of the three types of GORD, poses a risk of cancer?
Barrett’s oesophagus
What are the acid secreting cells in the oxyntic gland area?
Mucous cells
Chief cells
Parietal cells
ECL cells
What are the secreting cells in the pyloric gland area?
Mucous cells
G cells
D cells
No parietal cells
Why are there no parietal cells in the pyloric gland area?
Not necessary to secret HCL at the bottom of the stomach
Function of the mucous cells
Secrete mucous
Function of chief cells
Secrete pepsinogen
Function of ECL cells
Secrete histamine
Function of parietal cells
Secrete HCl
Function of D cells
Secrete somatostatin
Function of G cells
Secrete gastrin
How many litres of HCl is secreted per day by parietal cells?
1-2 L
What concentration is the HCl?
150-160 mM
What are the three positive factors in HCl acid production?
Gastrin
ACh
Histamine
What is the one negative regulator in HCl production?
D cells
What receptor does ACh bind to in the acid secretion pathway?
M3 receptor
What receptor does Gastrin bind to in the acid secretion pathway?
Cholecystokinin B (CKKB/CKK2) receptor
What receptor does Histamine bind to in the acid secretion pathway?
H2 receptor
Which pathway does ACh and Gastrin carry out acid secretion?
Act through G-coupled receptors
Increase in Ca2+ and diacylglycerol via PLC, IP3 pathway.
Which pathway does Histamine carry out acid secretion?
G-coupled receptor to increase cAMP.
MOST powerful stimulus for HCl secretion
What are the three phases of Acid Secretion Stimulation?
1) Celiac phase
2) Gastric phase
3) Intestinal phase
What is the Celiac phase?
The Sight/Smell/Thought of food
What is the Gastric phase?
When food is in the stomach and there is continuous secretion of HCl and pepsin
Higher pH
What is the Intestinial phase?
Chyme enters duodenum
Duodenal stimulation of hormones
Lower pH stimulates D cell activity
Stomach distnetion via vagovagal reflex increases parietal cell acid by? (4 steps)
1) Direct stimulation of ECl to release histamine
2)Direct stimulation of G cells to release gastrin via GRP.
3)Inhibition of somatostatin release from D cells in antrum
4)Pyloric antrum exposure to peptides- G cells release gastrin
>HCl by direct stimulation G cells and ECL histamine release
What happens when there is too much acid?
Stimulation of D cells to release somatostatin and inhibits gastrin release to limit acid secretion.
What are the 6 steps of HCl secretion?
1) CO2 diffuses into parietal cell from plasma
2) Combines with water to form carbonic acid
3) Carbonic acid dissociates into carbonate ions and H+ ions
4) H+/K+ ATPase actively transports H+ out, K+ in
5) K+ is recycled to gastric lumen via K+ channel
6) Cl- exists passively from cell via Cl- channel
How does Mucosal Protection from HCl happen?
1) Vagal stimulation and irritation stimulate gastric mucous cells –> mucin
What do gastric surface epithelial cells release?
HCO3-
What stimulates epithelial cells?
ACh
HCl
PGs
What happens to HCO3- released by Gastric epithelial surface cells?
Accumulate near the cell surface.
What happens to mucin produced by the epithelial cells?
They are cleaved by pepsin
