GI Flashcards
Describe the brief role of the mouth and oesophagus in digestion.
Mastication (chew)
Salivation
- protect mouth
- lubricate food
- starts digestion
Swallowing
-forms bolus
What is the role of the stomach in digestion?
Stores food
Mixes and disrupts
- secretes acids and enzymes to break down tissues and disinfect
- now called CHYME
What does the duodenum do to chyme in digestion?
Dilutes and neutralises it
What is the role of the small intestine in digestion?
Absorbs nutrients and electrolytes
Absorbs MOST water
What is the role of the large intestine in digestion?
Small bit of water absorption
Sloooow transit
Faeces form and accumulate in descending and sigmoid colon
Is chyme hypertonic, hypotonic or isotonic?
Hypertonic
What is the name of the subdivision of the autonomic ns that controls the GI tract?
Enteric nervous system
What is dysphagia?
Difficulty swallowing
What type of tumour affects the superior oesophagus and which inferiorly?
Superior-squamous cell carcinoma
Inferior-adenicarcinoma
A defect in which sphincter causes reflux?
Lower oesophageal sphincter
What causes Barrett’s oesophagus and what metaplasia occurs?
Reflux
Stratified squamous to simple gastric columnar (stomach epithelial)
What causes oesophageal varices?
Cirrhosis causing overload in venous portal system
-blood diverted to to oesophagus through connecting vessels leading to dilation of submucosal veins in lower oesophagus
What causes peptic ulceration?
Irritation from gastric acid
How can you tell if someone has pancreatitis?
Release of amylase into bloodstream
What causes pre and post hepatic jaundice?
Pre-excess Hb breakdown
Post-blockage of bile duct causing backing up of bile containing bilirubin
How are gallstones formed and what type of pain do they produce?
Precipitation of cholesterol and bile acids in gallbladder
If moving around can cause biliary colic
At what vertebral level does appendicitis visceral pain occur?
T10 level of umbilicus
What condition causes blood to be present in stools due to inflammation of anal vessels?
Haemorrhoids
What is prolapse?
Organs falling out of place e.g. Rectum
Define sigmoid colon diverticulum
Most common place due to high vasculature and weak area
Pouch formation due to high pressure
What is meckels diverticulum? List five features
Small outpouching from small intestine formed as a remnant of vitelline duct Present in: -2 yr olds -2% population -2:1 ratio of male to female
Site for ectopic gastric secretion causing irritation
- 2 feet proximal to ileocecal valve
- 2 inches in length
What 2 structures run through the inguinal canal in males and females?
Both-ilioinguinal nerve
Male-spermatic cord
Female-round ligament of uterus
Name the borders of hesselbachs triangle.
Inferior-inguinal ligament
Medial-lateral border of rectus abdominis
Lateral-inferior epigastric artery
Where do epigastric hernias occur?
Midline between xiphoid process and umbilicus through linea alba
What are the lateral and medial borders of the femoral canal?
Lateral-femoral vein
Medial-lacunar ligament
Where can a femoral hernia protrude to and what gender are they more common in and why?
Saphenous opening
Females-wider pelvis
What are the borders of the inguinal canal?
Roof-internal oblique and transversus abdominus
Floor-inguinal ligament
Anterior-aponeurosis of external oblique
Posterior-transversalis fascia
What cells produce HCL?
Parietal
What do chief cells produce?
Pepsinogen and gastric lipase
What cells produce mucous in the stomach?
Surface and neck mucous cells
What type of cells produce gastrin?
G cells
What do enterochromaffin like cells (ECL) produce? What other type of cell also produces the same substance as ECL cells?
Histamine
Mast cells
What cells produce somatostatin?
D cells
Parietal cells have many mitochondria allowing them to produce a lot of H+ ions. These shouldn’t stay within cells, so how is H+ excreted?
Invagination in cell wall with cannaliculi
Contain proton pump which pumps h+ out against conc gradient making it an energy intensive process
What three things stimulate parietal cell secretions?
Gastrin, Ach, histamine (gah!!)
What inhibits gastrin release?
Low Ph in stomach (neg feedback)
Digestion is aided by which part of the autonomic nervous system?
Parasympathetic
What, about food, stimulates Ach release? Give three
Sight of food
Smell of food
Swallowing
Distension of stomach
How does arrival of food at the stomach stimulate gastrin release?
Slightly alkali and buffers Ph causing it to rise and thus gastrin disinhibited
Give two occasions when gastrin secretion is reduced.
Chyme enters intestine (food no longer buffers PH and it decreases)
Hormones CCK and GiP (gastric inhibitory polypeptide)
What two substances act on parietal cells BUT also upregulate histamine action on parietal cells?
Gastrin
Ach
Name two ways acid secretion can be inhibited and give a named example for each.
Histamine H2 receptors
Cimetidine (removes amplification by Ach and gastrin)
PPI
Omeprazole (stops excretion of H+ ions from parietal cells)
How does mucus prevent dissolving of stomach mucosa?
Sticky and basic
Stops ions moving through it easily
H+ reacts with basic groups on mucus and secreted HCO3-
What is the PH around surface cells of stomach?
Well above 6
What stimulates HCO3- and mucus secretion from surface and neck cells?
Prostaglandins
What three things breach the stomachs defences and why?
Alcohol disssolves mucus and so acid attacks stomach
H pylori infect surface cells, reducing mucus and HCO3- secretion
NSAIDS inhibits prostaglandins reducing defences
What does breaching of the stomachs defences result in?
Peptic ulcers
How would you treat peptic ulcers and breaching of the stomachs defences?
That h pylori with antibiotics
Use acid secretion methods (H2 antagonist and PPis)
How does the vagus nerve asssist in limiting reflux?
Relaxes stomach wall as food passes down oesophagus
Pressure does not increase in stomach, allowing large meals to be consumed
Name the two types of muscle in the stomach
Circular and longitudinal
What causes the peristalsic contractions in the stomach?
Pacemaker cells in cardia region causes peristaltic contractions towards pylorus
What three things slow gastric emptying?
Fat, low PH and hypertonicity in duodenum
