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32 Cards in this Set

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Describe the properties of the enteric nervous system and its relationship to the autonomic nervous system
The enteric nervous system comprises of more nerve cells than the entire spinal cord. The neurons are collected into 2 types of ganglia, the myenteric plexus found between the inner and outer layers in the muscularis externa and the submucosal plexus. The enteric system communicates with the CNS via ANS, parasympathetic branch eg vagus nerve and sympathetic branches eg prevertebral ganglia but can also work independently from the CNS to control peristalsis, blood flow and the secretion of enzymes. They also receive sensory information from the gut epithelium and from stretch receptors in the wall of the tract.
Describe hiatus hernia.
A hiatus hernia is a protrusion of part of the stomach through the oesophageal hiatus of the diaphragm into the inferior mediastinum. The hernias occur most often after middle age due to weakening of the diaphragm muscle and thus widening of the oesophageal hiatus.
There are 2 main types of hiatus hernia.
Sliding hiatal hernia: this is the most common form and involves the abdominal oesophagus, cardia and parts of the fundus of the stomach sliding superiorly through the oesophageal hiatus into the thorax. This occurs especially in the supine position or when a person bends down. The clamping of the right crus of the diaphragm on the oesophagus is weak so reflux is common.
Paraesophageal hiatal hernia: the cardia of the stomach stays in the same position so there is no reflux but part of the fundus within a pouch of peritoneum extends through the oesophageal hiatus anterior to the oesophagus.
The lower oesophageal sphincter is described as a physiological sphincter. Name the mechanisms that help to prevent stomach contents refluxing into the oesophagus
1. The right crus of the diagphragm loops around the oesophagus and acts as an anatomical sphincter during inspiration.
2. The acute angulation of the oesophagus as it enters the stomach cardia produces a valve like effect.
3. The mucosal folds at the oesophagogastric junction also act like a valve
4. The positive intra-abdominal pressure compresses the walls of the the abdominal oesophagus preventing reflux.
Describe heartburn
Heartburn or pyrosis is the most common type of oesophageal discomfort or substernal pain. The burning sensation in the abdominal part of the oesophagus is usually the result of regurgitation of food or gastric fluid in the lower oesophagus. It may also be associated with hiatal hernia ( sliding not paraoesophageal)
What is a pylorospasm? Which age group is this common?
Pylorospasm is a spasmodic contraction of the pylorus which sometimes occurs in infants between 2-12 weeks. It is characterised by the failure of smooth muscle encircling the pyloric canal to relax normally so food does not pass easily from stomach to duodenum and the stomach becomes overly full. This results in discomfort and vomiting.
Describe congenital hypertrophic pyloric stenosis.
Hypertrophy of the smooth muscle surrounding the pyloric canal occurs narrowing the canal. This prevents the stomach from emptying and it may dilate and projectile vomiting may occur. Forceful or long term vomiting can result in a Mallory weiss tear of the oesophagus near the gastroesophageal junction. This could result in metabolic alkalosis and hypokalaemia. It is more common in males.
Define peptic ulceration and state where they are most common.
Peptic ulceration is the lesion of the mucosa lining the pyloric canal. in the stomach or the duodenumIn the stomach ulcers are mainly found on the lesser curvature. In the duodenum they are mainly found in the first part due to the acidic chyme not yet being neutrilised as bile and pancreatic secretions do not enter the duodenum until the 2nd part. Ulceration in 2nd part suggests pancreatic disease or zollinger elison syndrome. In zollinger elison syndrome there is a gastrin producing adenoma in the pancreas or duodenum which therefore increases acid secretion causing multiple peptic ulcers.
Zollinger elison syndrome should be investigated if multiple peptic ulcers, ulcers distal to duodenum or family history of peptic ulcers. symptoms are abdominal pain, dyspepsia, chronic diarrhoea due to inactivated of pancreatic enzymes and damage to intestinal mucosa. test fasting gastin levels and check for hypochlorhydria eg in chronic atrophic gastritis as this also will cause raised gastrin levels.
What structure lies behind the duodenum and why is this clinically relevant?
The gastroduodenal artery lies behind the 1st part of the duodenum and so if an ulcer there erodes posteriorly it may damage the artery. This artery branches to form the right gastroepiploic artery which follows the greater curvature of the stomach and forms the superior pancreaticoduodenal artery which supplies the duodenal cap and the head of the pancreas.
An adult can add up to 14l of fluid to their GI tract per day, where does the fluid come from?
Saliva, gastric secretions, water by osmosis from ECF in the duodenum, bile, pancreatic secretions,
Describe volvulus of the sigmoid colon.
The sigmoid colon is much more mobile than other parts of the colon and so rotation and twisting can result in a volvulus where there is an obstruction of the lumen of the descending colon. This could lead to constipation and ischaemia of the looped part of the sigmoid colon resulting in fecal impaction, an immovable collection of hardened faeces.
What are diverticula?
Diverticula are outpouches of a hollow structure of the body. True diverticulas involve all of the layers of the structure where as false diverticulas do not have muscular layers or adventitia. Diverticulas in the GI tract are therfore false diverticula as they only contain the mucosa and submucosa and not the adventitia/serosa.
Describe appendicitis, what are the most common causes?
The appendix is a blind ended tube extending from the caecum. It has a large amount of lymphoid tissue. Appendicitis is inflammation and swelling of the appendix and is quite common. In young people it commonly arises due to hyperplasia of lymphatic follicles in the appendix which occlude the lumen. In older people the most common way is for a fecalith ( stone made of faeces) to block the lumen so that excretions from the lumen cannot escape. The appendix swells and stretches the visceral peritoneum.
Describe the pain of appendicitis. Give examples of diseases which mimic appendicitis.
The pain is initially vague and felt in the periumbilical region. It later worsens and relocates to the right iliac fossa at the mcburney’s point.
Meckels diverticula and mesenteric adenitis can mimic pain felt in appendicitis
What are haemorrhoids?
Haemorrhoids are rectal veins in the lower portion of the rectum or anus which are physiological and help with stool control. They become pathological when they are dilated. They result from increased pressure in the veins of the anus, commonly caused by straining during bowel movements, pregnancy and from portal venous hypertension. The patient may complain of itchy anus, bleeding in stools, pain especially while sitting down or opening bowels. If they occur above the dentate line ( internal haemorrhoids) they are relatively painless and present with some rectal bleeding.
If they occur below the dentate line they are external hemorrhoids with can be very painful as the nervous innervation is somatic.
Injecting or banding haemorrhoids above the dentate line is accepted practice as this will be painless. If either are performed below the dentate line it will be extremely painful and not tolerated.
• The upper rectum is supplied by the branches of the inferior mesenteric artery via the superior rectal branch and receives a nerve supply from the visceral pelvic splanchnic nerves arising from the sympathetic chain and S2, 3 & 4, thus pain is dull and poorly located. Venous drainage is into the portal system via the inferior mesenteric vein with lymphatic drainage to the mesenteric nodes.
• The lower rectum is supplied by the inferior rectal artery a branch of the internal iliac artery and receives a nerve supply from the inferior rectal nerve, a somatic nerve arising from the pudendal nerve, thus pain is sharp and well defined. Venous drainage is into the systemic circulation via the internal iliac vein and lymphatic drainage is to the iliac and inguinal nodes.

Above the dentate line, mucosa is lined with glandular columnar epithelium and below it is lined by stratified squamous.
What symptoms might someone with troublesome haemorrhoids complain of?
Anal itching, bleeding in stools, pain especially while sitting and when opening bowels. Treatment with corticosteroid creams.
Define achalasia.
Achalasia is when the lower oesophageal sphincter fails to relax completely and thus open. This results in dysphagia, vomiting and sometimes chest pain.
Describe the oesophagus.
The oesophagus is 25cm long and starts from the cricopharyngeal sphincter and terminates at the cardiac orifice of the stomach. At the oesophageal gastric junction the pink stratied squamous epithetlium changes to a red columnar gastric eptihelium. From incisor teeth to the cardia of the stomach, the length is 40cm which is relevant when inserting a nasopharyngeal tube. The upper 2/3 comprises of striated skeletal muscle and its blood supply is from the inferior thyroid artery and drains into the inferior thryoid vein and branches of azygos vein. The lower 1/3 comprises of smooth muscle and is supplied by left gastric artery of celiac trunk and the left inferior phrenic artery and drains into the left gastric vein which empties into the portal venous system. Therefore portosystemic shunting through these anastomoses can take place during portal venous hypotension and cause oesophageal varices.
What are the functions of saliva?
- Aids swallowing by formation of bolus
- Protection of oral environment by producing a moist and alkaline environment, preventing dental caries, mucosal decay or infections
- Releases enzymes for digestion of carbohydrates.
Saliva protects the mouth by being wet, bacteriostatic (stops bacteria from reproducing), alkaline and having high calcium concentration, which prevents destruction of teeth by acid. It also lubricates food for mastication and swallowing by being wet and mucus. It also starts digestion by containing amylases, breaking down large polysaccaharides into mono-saccharides and oligosaccharides
Define dysphagia.
Dysphagia is difficulty swallowing. It may be caused by anaesthesia, neurological deficits, oesophageal muscular problems or obstruction by a tumour. Liquids are harder to swallow thus drinks are sometimes thickened to ease the process.
Describe Oropharyngeal dysphagia.
Orophayngeal dysphagia is difficulty in swallowing liquids.

There must be a neurological problem affecting the swallowing centre in the medulla oblongata.
- Bulbar palsy – the medulla is directly damaged and the lower cranial nerves 4, 5 &7. This is very rare eg guillian barre syndrome.
- Pseudobulbar palsy – there is a problem with the connections between the cerebral cortex and the medulla. This is more common eg stroke, MS, parkinsons.

The swallowing reflex is usually triggered by fluid and food hitting receptors in the palate and anterior pharynx. This signals the medulla oblongata which stimulates breathing to stop so that food and fluid do not go down the trachea, raises larynx, closes glottis, opens upper oesophageal sphincter.
The food bolus moves down the oesophagus by peristalsis. The inner circular smooth muscle contracts to form a ram behind the bolus and the longitudinal smooth muscle contracts the squeeze the bolus down the tube. The transit time to the stomach is about 9secs.
Describe oesophageal dysphagia.
Oesophageal dysphagia is difficulty in swallowing solids.
There must be a physical blockage or narrowing of the oesophagus which obstructs the passage of the bolus.
- Oesophageal adenocarcinoma/squamous cell carcinoma
- Carcinoma of cardiac part of stomach preventing the opening of the lower oesophageal sphincter
- Cancers outside of the oesophagus obstructing the oesophagus
- Cancer of the oropharynx
- Strictures of the oesophagus caused by chronic acid reflux
Define achalasia.
Achalasia is a failure of the lower oesophageal sphincter to relax, which results in dysphagia. The cause is thought to be lack of some inhibitory neurones at the LOS or damage to these neurones which upsets the excitatory/inhibitory neurotransmission. It is rare.
Define oesophageal varices.
Oesophageal varices are dilated mucosal submucosal veins in the oesophagus that occur due to portal venous hypertension as a result of a Porto-systemic anastomosis in this area. Blood from the oesophagus normally drains into the Portal venous system via the Left gastric vein and into the systemic system via the Azygos vein. In Portal hypertension the blood which would normally drain through the left gastric vein is redirected through veins in the oesophageal mucosa directly to the Azygos vein. These mucosal veins are normally present, but not dilated. When they are dilated they are termed varices. The vessels can rupture and cause haemotomesis.
What is a Mallory weiss tear?
A Mallory weiss tear is a tear of the mucosa at gastroesophageal junction. It is caused by forceful or long term vomiting or coughing where the increased pressure in the oesophagus, causes the mucosa to tear. The tear may bleed leading the haematomesis and malaena.
What are the consequences of repeated vomiting? What changes would you see on a blood test?
Prolonged and excessive vomiting depletes the body of water (dehydration), and may alter the electrolyte status.
Gastric vomiting leads to the loss of acid (protons) and chlorine directly. This results in increased levels of HCO3- in the blood causing hypochloremic metabolic alkalosis. The alkalosis is worsened by the parietal cells increasing formation of acid and alkali. The HCO3- enters the blood and would then enter the duodenum at the ampulla of vater, (the alkaline tide) but due to no acid being present in the duodenum, the alkali remains in the blood. Hypokalemia may also result due to H ions being pumped out from cells in exchange for K ions.
Due to the loss of intake of food the individual may eventually become cachectic. A less frequent occurrence results from a vomiting of intestinal contents, including bile acids and HCO3-, which can lead to metabolic acidosis.

So overall a blood test may show: High Ph, low potassium, low chlorine and dehydration.
Explain some common upper GI causes of bleeding.
Causes of GI bleeding are acute/ chronic peptic ulceration, Mallory weiss tear, oesophageal varices, upper GI cancers, and erosive gastritis. Peptic and gastric ulcers can cause haematemesis.
Explain some common lower GI causes of bleeding
Colonic carcinoma, diverticular disease, crohns disease, ulcerative colitis, angiodysplasia – small vascular malformation of the gut, haemorrhoids
WHAT IS A MECKELS DIVERTICULUM?
A diverticulum ( an unsual extension) of the ileum caused by persistence of part of the yolk stalk (vitilline tract) . It runs along the antimesenteric border and can be memorised by the rules of 2s: it is 2inches long, 2 feet from the ileocoecal junction, occurs in 2% of the population, is symptomatic in 2% of the population, 2 years is the most common age for clinical presentation.
The diverticulum may be free or may be attached to the umbilicus. Its mucosa is mainly ileal but it may contain areas of acid producing gastric tissue, pancreatic tissue or jejuna or colonic mucosa. The meckel diverticulum may become inflamed and mimic the pain of appendicitis (first vague pain in periumbilicus area and then severe pain lower right quadrant, the mcburney point).
what is SMA syndrome?
Superior mesenteric artery syndrome is when a patient dramatically loses weigth and the duodenum can become partially or completely obstructed by external compression from the aorta ( posteriorly) and the SMA anteriorly.
which site is the mot common for diverticular disease? explain why this is? are they true or false divertula?
The sigmoid colon is the most common site for diverticula to form. This is because overtime the combination of fecal stagnation and frequent straining causes weaker parts of the colon to give way a protrude outwards to form a diverticulum. The diverticulum comprises of only mucosa and submucosa and is therefore a false diverticula. To prevent diverticulosis, adopt squatting position. In 3rd world countried where they don't have sitting toilets and so must squat, the prevalence of diverticulosis is very low.
The kink in the sigmoid colon prevents emptying into rectum. When squatting, the left thigh rises the colon anteriorly so it easily empties into the rectum. When sitting the puborectal muscles pull on the rectum to maintain continence. When squatting the muscle relaxes and straightens the pathway to anus.
Define malena and give an example of when it might occur.
Malena is a black, sticky, tar-y stool. It is produced when there is bleeding into the bowel, eg from peptic ulcers. The haem is oxidised which causes the black colour. People may also have malena if they are on iron tablets.
Describe pain felt from injury to foregut, midgut and hindgut structures.
Intraperitoneal structures are surrounded by visceral peritoneum. When visceral peritoneum is inflamed or infected, they do not have specific pain receptors to relay these innervations to the CNS and instead accompany the sympathetic afferent fibres which produce a vague pain in the appropriate dermatome unlike parietal peritoneum which have specific somatic pain fibres.
Where the vague pain is felt along the midline is decided on whether the organ derives from foregut, midgut or hindgut. A foregut derivative will cause pain in the epigastric area. A midgut derivative will produce pain in the peri-umbilicus area. A hindgut derivative will produce pain in the hypogastric/supra pubic area.