Digestive System

Cards (44)

  • Upper Gastro Intestinal Tract (GIT)
    • Oesophagus
    • Stomach
    • Duodenum
  • Oesophagus
    1. Continuous with the laryngeal part of the pharynx at the level of the C6 vertebra
    2. Passes through the posterior mediastinum in the thorax
    3. Enters the abdomen through a hole in the diaphragm at the level of the tenth thoracic vertebra (T10)
    4. Usually about 25cm, but extreme variations have been recorded ranging 10-50 cm long depending on individual height
    5. Divided into cervical, thoracic, and abdominal sections
  • Inferior pharyngeal constrictor muscle

    Only allows entry into the oesophagus when swallowing or vomiting
  • Layers of oesophageal wall
    • Mucosa
    • Lamina propria
    • Muscularis mucosae
    • Submucosa
    • Muscularis propria
  • Oesophageal constrictions
    • The oesophageal inlet where the pharynx joins the oesophagus, behind the cricoid cartilage (14-16cm from the incisor teeth)
    • Where its anterior surface is crossed by the aortic arch and the left bronchus (25-27 cm from the incisor teeth)
    • Where it pierces the diaphragm (36-38 cm from the incisor teeth)
  • Gastro-oesophageal Junction

    The junction between the oesophagus and the stomach is not actually considered a valve, although it is sometimes called the cardiac sphincter, cardia or cardias
  • Peristaltic wave
    In much of the gastrointestinal tract, smooth muscles contract in sequence to produce a wave which forces a bolus of food to move through the tract
  • Common Diseases
    • Acute oesophageal necrosis
    • Achalasia
    • Barrett's oesophagus
    • Chagas disease
    • Oesophageal atresia
    • Oesophageal cancer
    • Hiatus Hernia
    • Neurogenic dysphagia
  • Barrett's Oesophagus
    Refers to an abnormal change (metaplasia in the cells of the lower portion of the oesophagus) where normal squamous epithelium lining the oesophagus is replaced by goblet cells (cells usually found lower in the gastrointestinal tract)
  • Heartburn
    Can erode lining which leads to Barrett's oesophagus
  • Barrett's oesophagus
    Considered premalignant condition as it is associated with increased risk of oesophageal adenocarcinoma
  • Diagnosis of Barrett's oesophagus
    1. Endoscopy
    2. Oesophagogastroduodenoscopy --> fibre optic cable inserted through the mouth --> examines oesophagus, stomach and duodenum --> small biopsy taken
  • Biopsy classification
    • Non-dysplastic
    • Low grade dysplasia
    • High grade dysplasia
    • Frank carcinoma
  • Gastro-oesophageal Reflux Disease (GORD)

    Chronic symptom of mucosal damage caused by stomach acid coming up from the stomach into the oesophagus
  • Causes of GORD
    • Abnormal relaxation of the lower oesophageal sphincter, normally holds the top of the stomach closed
    • Impaired expulsion of gastric reflux from the oesophagus
    • A hiatus hernia
  • Symptoms of GORD
    • Heartburn
    • Regurgitation
    • Difficulty swallowing (dysphagia)
    • Pain with swallowing/sore throat (odynophagia)
    • Increased salivation
    • Nausea
    • Chest pain, often mimicking early heart attack symptoms
  • Injuries from GORD
    • Reflux oesophagus - Necrosis of oesophageal epithelium causing ulcers near junction of stomach and oesophagus
    • Oesophageal strictures - The persistent narrowing of the oesophagus caused by reflux-induced inflammation
    • Barrett's oesophagus - Intestinal metaplasia of distal oesophagus
    • Oesophageal adenocarcinoma - A rare form of cancer
  • Hiatus Hernia
    • Most common is sliding hiatus hernia (95%)
    • Second kind is rolling (paraoesophageal)
  • Diagnosis of Hiatus Hernia
    Upper GI series, endoscopy or high resolution manometry
  • Chronic reflux
    Can severely injure the oesophagus and can lead to cancer
  • Types of oesophageal cancer
    • Squamous cell carcinoma
    • Adenocarcinoma
  • Treatment of oesophageal cancer
    1. Small and localised tumours are treated surgically
    2. Larger tumours tend not to be operable and treated with palliative care
    3. Growth can be delayed with chemotherapy, radiotherapy or a combination
  • Prognosis of oesophageal cancer

    Depends on extent of disease and other medical problems, but is generally fairly poor
  • Stomach enzymes
    Have an optimum condition - work at a specific pH and temperature better than any other
  • Stomach acid
    • Does not break down food molecules, rather it provides an optimum pH for the reaction of enzyme pepsin and kills many microorganisms that are ingested with the food
    • Can also denature proteins. Process of reducing polypeptide bonds and disrupting salt bridges - causes a loss of secondary, tertiary or quaternary protein structure
  • Layers of stomach wall
    • Serous membrane
    • Muscular coat
    • Submucosa
    • Mucosa
  • Helicobacter pylori
    • Gram -ve
    • Microaerophilic bacterium
    • Present in patients with chronic gastritis and gastric ulcers
    • Also linked to development of duodenal ulcers and stomach cancer
  • Risks for individuals infected with H. pylori
    • 10-20% lifetime risk of developing peptic ulcers
    • 1-2% risk of acquiring stomach cancer
  • Inflammation of the pyloric antrum
    More likely to lead to duodenal ulcers
  • Inflammation of the corpus
    Leads to gastric ulcers and gastric carcinomas
  • Ammonia
    Biochemicals --> ulcers
  • Small intestine
    • Duodenum
    • Jejunum
    • Ileum
  • Duodenum
    • Largely responsible for breakdown of food in small intestine using enzymes
    • The villi have a leafy-looking appearance; there is a histologically identifiable structure the Brunner's glands, which secrete mucus found in the duodenum only
    • Wall is composed of a very thin layer of cells forming muscularis mucosae
  • Jejunum
    • Mid-section of intestine, connecting duodenum to the ileum
    • Has many large circular folds in its submucosa called plicae circulares plus villi to increase SA of part of GI tract
    • Epithelial cells that line the villi have microvilli (much longer than that of the duodenum and ileum)
    • Products of digestion are absorbed into the bloodstream and enter the liver via the hepatic portal vein
    • Contains very few Brunner's glands or Peyer's patches
  • Ileum
    • Absorbs vitamin B12 and bile salts and leftover products of digestion not absorbed by jejunum
    • Epithelial cells that line these villi possess even larger numbers of microvilli. - extremely large SA both for absorption of enzyme molecules and products of digestion
    • Only the ileum has abundant Peyer's patches - unencapsulated lymphoid nodules that contain large numbers of lymphocytes and immune cells
  • Differences between Jejunum and Ileum
    • Jejunum has less fat inside its mesentery and is typically of larger diameter
    • Ileum has Peyer's patches
    • Villi of the jejunum look like long, finger-like projections, and are a histologically identifiable structure
  • Coeliac Disease
    • An autoimmune disorder of the small intestine
    • Caused by a reaction to gliadin, a prolamin (gluten protein)
    • Genetics
  • Symptoms of Coeliac Disease
    • Diarrhoea
    • Abdominal pain
    • Lactose intolerance
    • Increased risk of malignancies
  • Marsh classification
    Classic pathology changes of coeliac disease in the small bowel are categorised by this, which over time has been modified to a number of stages
  • Large intestine
    • Caecum
    • Colon
    • Sigmoid