MedYear2 Semester 1: Protein Processing Quiz
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Questions and Answers

What is the primary purpose of proteolysis in protein metabolism?

  • To synthesize proteins from amino acids
  • To convert glucose into amino acids
  • To degrade proteins into amino acids (correct)
  • To produce ammonia from amino acids

    • Which amino acid is linked to heart disease when elevated?

  • Methionine
  • Homocysteine (correct)
  • Serine
  • Glutamine

    • During amino acid catabolism, glucogenic amino acids can be converted into which of the following?

  • Ammonia
  • Urea
  • Acetyl CoA
  • Pyruvate (correct)

    • What is the role of transamination in amino acid metabolism?

    <p>It synthesizes amino acids from metabolic intermediates (A)</p> Signup and view all the answers

    In the urea cycle, what substance is primarily formed as a waste product?

    <p>Urea (A)</p> Signup and view all the answers

    Which amino acids are classified as essential amino acids?

    <p>Isoleucine, Leucine, Methionine (D)</p> Signup and view all the answers

    What is the end product of the synthesis of tyrosine from phenylalanine?

    <p>NADH (A)</p> Signup and view all the answers

    Which of the following amino acids is considered semi-essential?

    <p>Histidine (A)</p> Signup and view all the answers

    From which metabolic intermediate is serine synthesized?

    <p>3-phosphoglycerate (C)</p> Signup and view all the answers

    If dietary availability of phenylalanine is restricted, what happens to tyrosine?

    <p>It becomes an essential amino acid. (A)</p> Signup and view all the answers

    Which enzyme is responsible for synthesizing glutamine from glutamate?

    <p>Synthase (A)</p> Signup and view all the answers

    What condition results from an inability to synthesize tyrosine?

    <p>Phenylketonuria (PKU) (C)</p> Signup and view all the answers

    Which amino acid is synthesized from α-ketoglutarate in the transamination process?

    <p>Aspartate (C)</p> Signup and view all the answers

    What is the primary role of transaminase enzymes in the body?

    <p>Conversion of amino acids (D)</p> Signup and view all the answers

    Which of the following describes the identity of an amino acid?

    <p>Its R-group structure (D)</p> Signup and view all the answers

    Amino acids serve as precursors for all the following EXCEPT:

    <p>Lipids (B)</p> Signup and view all the answers

    What process is primarily responsible for the elimination of amino nitrogen from the body?

    <p>Ureogenesis (D)</p> Signup and view all the answers

    Which amino acid is a precursor for the synthesis of the neurotransmitter serotonin?

    <p>Tryptophan (A)</p> Signup and view all the answers

    How does the body utilize amino acids in energy-yielding metabolism?

    <p>They undergo oxidation to produce ATP. (D)</p> Signup and view all the answers

    Which of the following statements about essential amino acids is true?

    <p>They must be obtained from the diet. (A)</p> Signup and view all the answers

    What condition is exemplified by a defect in the urea cycle leading to accumulation of ammonia in the body?

    <p>Ornithine transcarbamylase deficiency (D)</p> Signup and view all the answers

    Which organ primarily provides amino acids to circulation in the fasting state?

    <p>Muscle (B)</p> Signup and view all the answers

    In the process of transamination, which molecule is typically the acceptor of the amino group?

    <p>α-ketoglutarate (D)</p> Signup and view all the answers

    What is the primary nitrogen disposal method in the body?

    <p>Urea cycle (D)</p> Signup and view all the answers

    Which enzyme is considered the rate-limiting step in the urea cycle?

    <p>Carbamoyl phosphate synthase I (C)</p> Signup and view all the answers

    What condition results from excess ammonia in the blood?

    <p>Hyperammonaemia (B)</p> Signup and view all the answers

    Which amino acid primarily acts as a 'collector' of amino groups during transamination?

    <p>Glutamate (C)</p> Signup and view all the answers

    What is the main effect of low energy levels on amino acid degradation?

    <p>Increases amino acid degradation (A)</p> Signup and view all the answers

    Which cycle facilitates the transport of nitrogen from muscle to the liver?

    <p>Glucose-alanine cycle (D)</p> Signup and view all the answers

    What is one of the major symptoms of hyperammonaemia?

    <p>Slurring of speech (D)</p> Signup and view all the answers

    Which amino acid is predominantly synthesized in muscle through transamination?

    <p>Alanine (B)</p> Signup and view all the answers

    A deficiency in which enzyme leads to the most common form of urea cycle disorder?

    <p>Ornithine transcarbamylase (A)</p> Signup and view all the answers

    Which of the following correctly describes the role of glutamate dehydrogenase?

    <p>Converts glutamate to α-ketoglutarate and releases ammonia (D)</p> Signup and view all the answers

    What is the primary purpose of the urea cycle?

    <p>To excrete nitrogenous waste as urea (D)</p> Signup and view all the answers

    What is the primary component of dietary lipids ingested by humans?

    <p>Triglycerides (A)</p> Signup and view all the answers

    What is the significance of short-chain fatty acids in lipid digestion?

    <p>They are water-soluble and easier to transport in the blood. (B)</p> Signup and view all the answers

    Which of the following best describes how lipids are emulsified for digestion?

    <p>By bile salts that create a stable suspension of droplets. (C)</p> Signup and view all the answers

    Which vitamins are classified as fat-soluble vitamins?

    <p>Vitamins A, D, E, and K (A)</p> Signup and view all the answers

    What mechanism facilitates the absorption of lipids in the digestive system?

    <p>Transport by specialized lipoproteins. (A)</p> Signup and view all the answers

    What impact does malabsorption syndrome have on lipid digestion?

    <p>It results in compromised nutrient absorption, including fats. (A)</p> Signup and view all the answers

    Which statement accurately reflects the process of lipid digestion?

    <p>Lipid emulsification occurs predominantly in the intestine. (C)</p> Signup and view all the answers

    What type of fatty acids must be obtained through diet because they are essential?

    <p>Essential fatty acids such as linoleic and linolenic (C)</p> Signup and view all the answers

    Which enzyme binds to the surface of lipid droplets to facilitate lipid digestion?

    <p>Pancreatic lipase (B)</p> Signup and view all the answers

    How do bile salts contribute to lipid digestion?

    <p>By creating micelles that enhance the absorption of lipids. (D)</p> Signup and view all the answers

    What is the role of co-lipase in lipid digestion?

    <p>To enhance the action of pancreatic lipase (D)</p> Signup and view all the answers

    What determines the caloric value of lipids in the diet?

    <p>Each gram of fat generates approximately 9 calories. (B)</p> Signup and view all the answers

    Which enzyme is secreted as an inactive precursor and activated by trypsin?

    <p>Phospholipase (D)</p> Signup and view all the answers

    What is the primary function of cholesterol esterase?

    <p>Removing one fatty acid from cholesterol esters (A)</p> Signup and view all the answers

    What compound is responsible for activating pro-colipase?

    <p>Trypsin (D)</p> Signup and view all the answers

    Which of the following best describes the structure of micelles?

    <p>Lipid particles ~4-6 nm in diameter (A)</p> Signup and view all the answers

    What characterizes free fatty acids and monoacylglycerols in terms of solubility?

    <p>They are insoluble in water (D)</p> Signup and view all the answers

    What is the end product of lysophospholipase activity?

    <p>Glycerophosphate and a fatty acid (D)</p> Signup and view all the answers

    Which gut hormone stimulates the contraction of the gallbladder and secretion of pancreatic enzymes?

    <p>Cholecystokinin (CCK) (B)</p> Signup and view all the answers

    What is the primary role of phospholipase in digestion?

    <p>Hydrolyzing phospholipids (D)</p> Signup and view all the answers

    What is the primary structural component of chylomicrons?

    <p>Apolipoprotein B-48 (C)</p> Signup and view all the answers

    How do short and medium-chain fatty acids primarily enter the bloodstream?

    <p>Directly via the hepatic portal vein (B)</p> Signup and view all the answers

    Which vitamins rely on fat absorption mechanisms for normal absorption?

    <p>Vitamins A, D, E, K (B)</p> Signup and view all the answers

    What happens to bile salts after their role in digestion?

    <p>They are recycled and re-absorbed in the ileum (B)</p> Signup and view all the answers

    Which component is NOT directly involved in the formation of mixed micelles?

    <p>Triglycerides (C)</p> Signup and view all the answers

    What percentage of chylomicrons is composed of lipids?

    <p>98-99% (A)</p> Signup and view all the answers

    Which process allows lipid breakdown products to enter enterocytes?

    <p>Simple diffusion or specific transporter proteins (B)</p> Signup and view all the answers

    What is the primary transportation mechanism for lipids within the lymphatic system?

    <p>Chylomicrons (D)</p> Signup and view all the answers

    What is a consequence of fat malabsorption in terms of vitamin absorption?

    <p>Vitamin deficiency syndromes (C)</p> Signup and view all the answers

    Which phase of chylomicron formation occurs at the rough endoplasmic reticulum?

    <p>Protein synthesis (B)</p> Signup and view all the answers

    What is the primary consequence of global malabsorption in a patient with celiac disease?

    <p>Weight loss and weakness (A)</p> Signup and view all the answers

    Which type of absorption impairment is characterized by deficiencies of specific nutrients such as vitamin B12?

    <p>Partial malabsorption (A)</p> Signup and view all the answers

    What role does indigestible material, often referred to as fiber, play in the gastrointestinal tract?

    <p>Facilitates movement through the GIT (C)</p> Signup and view all the answers

    Which condition is associated with inadequate mucosal surface due to flattening of the villi?

    <p>Celiac disease (B)</p> Signup and view all the answers

    What is a potential outcome of pancreatic insufficiency in the context of malabsorption?

    <p>Steatorrhea (visible fat in feces) (A)</p> Signup and view all the answers

    During anaerobic fermentation by intestinal flora, which type of gas is not produced?

    <p>Oxygen (A)</p> Signup and view all the answers

    Which of the following conditions is likely to lead to a loss of intrinsic factor, affecting vitamin B12 absorption?

    <p>Gastrectomy (A)</p> Signup and view all the answers

    What commonly accompanies malabsorption and is characterized by the presence of fat in feces?

    <p>Steatorrhea (B)</p> Signup and view all the answers

    In which scenario is an inflammatory response likely to cause malabsorption in the jejunum?

    <p>Acute salmonella infection (D)</p> Signup and view all the answers

    What specific factor is crucial for normal nutrient absorption in the GIT?

    <p>Integrity and normal structure of absorptive areas (B)</p> Signup and view all the answers

    What is the primary characteristic of the mucosa in the oesophagus?

    <p>It contains squamous epithelium and lamina propria. (A)</p> Signup and view all the answers

    Which of the following is NOT a common cause of dysphagia?

    <p>Lung infection (D)</p> Signup and view all the answers

    Barrett's oesophagus is defined as a condition where which type of tissue replaces the normal squamous epithelium?

    <p>Columnar epithelium (C)</p> Signup and view all the answers

    What are the structural layers of the oesophagus from innermost to outermost?

    <p>Mucosa, submucosa, muscle layer, adventitia (D)</p> Signup and view all the answers

    Which type of abnormality is often associated with pulmonary issues in infants?

    <p>Tracheoesophageal fistula (B)</p> Signup and view all the answers

    What distinguishes 'true' diverticula from 'false' diverticula?

    <p>True diverticula consist of all four layers. (D)</p> Signup and view all the answers

    Which type of hernia constitutes 95% of hiatus hernias?

    <p>Sliding (axial) hernia (C)</p> Signup and view all the answers

    What characterizes the functional obstruction seen in achalasia?

    <p>Failure of the lower esophageal sphincter to relax (D)</p> Signup and view all the answers

    Which condition is most often associated with tearing of the lower esophagus after severe vomiting?

    <p>Mallory-Weiss tear (A)</p> Signup and view all the answers

    What is a common infectious cause of secondary achalasia?

    <p>Trypanosoma infection (A)</p> Signup and view all the answers

    What histological feature is characteristic of reflux esophagitis?

    <p>Basal cell hyperplasia (A)</p> Signup and view all the answers

    What condition is characterized by dilated veins in the submucosa of the esophagus?

    <p>Oesophageal varices (C)</p> Signup and view all the answers

    Which anatomical feature marks the junction between the esophagus and the stomach?

    <p>Oesophagogastric junction (A)</p> Signup and view all the answers

    Which part of the oesophagus is primarily composed of squamous epithelium?

    <p>Mucosa (D)</p> Signup and view all the answers

    What is a common cause of dysphagia related to lesions outside the wall of the oesophagus?

    <p>Aortic aneurysm (A)</p> Signup and view all the answers

    Which condition is characterized by the abnormal growth of the oesophageal lining and is specifically defined as Barrett's oesophagus?

    <p>Metaplasia of the esophageal mucosa (C)</p> Signup and view all the answers

    What is one of the developmental abnormalities associated with the oesophagus commonly recognized?

    <p>Tracheoesophageal fistula (C)</p> Signup and view all the answers

    Which of the following is NOT a recognized category causing dysphagia?

    <p>Functional lesions (B)</p> Signup and view all the answers

    What distinguishes true diverticula from false diverticula?

    <p>True diverticula involve all four layers. (A)</p> Signup and view all the answers

    Which feature is characteristic of achalasia?

    <p>Aperistalsis in the esophagus. (D)</p> Signup and view all the answers

    What is the primary cause of Mallory-Weiss tears?

    <p>Severe vomiting leading to tearing of the lower esophagus. (C)</p> Signup and view all the answers

    Which abnormality is associated with esophageal varices?

    <p>Portal hypertension leading to dilated veins. (C)</p> Signup and view all the answers

    What is a common secondary cause of achalasia?

    <p>Diabetes mellitus. (A)</p> Signup and view all the answers

    Pulsion diverticula are primarily caused by what mechanism?

    <p>Increased abdominal pressure. (C)</p> Signup and view all the answers

    Which histological feature is NOT associated with reflux esophagitis?

    <p>Squamous cell carcinoma. (B)</p> Signup and view all the answers

    What anatomical separation is involved in a hiatus hernia?

    <p>Separation of the diaphragmatic crura. (B)</p> Signup and view all the answers

    What is the primary function of the submucosa in the esophagus?

    <p>Support connective tissue, blood vessels, and nerves (B)</p> Signup and view all the answers

    Which of the following conditions is most likely to cause dysphagia due to lesions affecting function?

    <p>Achalasia (C)</p> Signup and view all the answers

    Which structure provides connective tissue support to the esophagus?

    <p>Adventitia (A)</p> Signup and view all the answers

    What is the most common developmental abnormality of the esophagus?

    <p>Atresia/Fistula (D)</p> Signup and view all the answers

    Barrett's esophagus is defined primarily by which of the following pathological changes?

    <p>Replacement of squamous epithelium with columnar epithelium (A)</p> Signup and view all the answers

    What distinguishes a 'true' diverticulum from a 'false' diverticulum?

    <p>A 'true' diverticulum involves all four layers of the gastrointestinal wall. (C)</p> Signup and view all the answers

    Which of the following correctly describes the primary cause of achalasia?

    <p>Loss of inhibitory innervation to the lower esophageal sphincter. (C)</p> Signup and view all the answers

    What anatomical feature is MOST commonly associated with hiatus hernia?

    <p>Displacement of the diaphragmatic crura. (C)</p> Signup and view all the answers

    Which statement correctly describes the pathology of oesophageal varices?

    <p>They manifest primarily due to hypertension in the portal circulation. (A)</p> Signup and view all the answers

    What type of abnormality does a 'Mallory-Weiss' tear represent?

    <p>A longitudinal rupture in the lower oesophagus due to severe pressure. (D)</p> Signup and view all the answers

    Which statement best captures the histological features of reflux oesophagitis?

    <p>Hyperplasia of basal cells presents alongside elongated lamina propria papillae. (A)</p> Signup and view all the answers

    Which condition is commonly associated with viral causes for oesophageal inflammation?

    <p>Infective oesophagitis caused by viruses like herpes or CMV. (C)</p> Signup and view all the answers

    What role does traction play in the formation of diverticula?

    <p>Traction diverticula are linked to local pathology such as mediastinal adenopathy. (B)</p> Signup and view all the answers

    Study Notes

    Learning Objectives

    • Functions of amino acids: building blocks of proteins, precursors for hormones, neurotransmitters, and nucleic acids.
    • Distinction between essential (cannot be synthesized) and non-essential (can be synthesized) amino acids.
    • Importance of transaminase enzymes in amino acid metabolism and nitrogen transfer.
    • Amino acids serve as substrates in gluconeogenesis, ketogenesis, and energy-yielding pathways.
    • Ureogenesis is a crucial process for eliminating ammonia from the body.

    Amino Acid Structure

    • Composed of an α-carboxyl group, α-amino group, and a variable R-group determining identity.

    Functions of Amino Acids

    • Constituents of proteins such as enzymes, receptors, hormones, and transport proteins.
    • Source of smaller biologically active compounds like haem, nucleotides, and neurotransmitters.

    Protein Turnover and Pool

    • Total body protein ~12 kg with a daily turnover of ~100 g.
    • Amino acid levels maintained by muscle (release during fasting) and liver (urea cycle).

    Amino Acid Degradation

    • Amino acids classified into glucogenic (converted to glucose) or ketogenic (converted to ketone bodies).
    • Transamination involves transfer of an amino group between amino acids, catalyzed by aminotransferase enzymes.

    Transamination

    • Glutamate often acts as the amino group donor.
    • Equilibrium of reactions allows for both degradation and synthesis of amino acids.

    Glucose-Alanine Cycle

    • Muscle synthesizes alanine which is transported to the liver, converted to glucose via gluconeogenesis.

    Glutamate Dehydrogenase

    • Facilitates oxidative deamidation of glutamate to release ammonia and recycle α-ketoglutarate.
    • Reaction directionality depends on concentration of substrates and allosteric effects of energy levels.

    Ammonia and Its Toxicity

    • Ammonia is a neurotoxin, leading to hyperammonaemia, causing symptoms like slurring of speech and coma.
    • Primarily disposed of through conversion to urea in the liver via the urea cycle.

    Transport of Nitrogen to Liver

    • Glutamine synthetase combines glutamate with ammonia for transport; converted back in the liver.
    • Alanine transports nitrogen from muscle to liver for processing.

    Urea Cycle

    • Converts ammonia to urea in the liver through a series of enzymatic reactions.
    • Key enzymes include carbamoyl phosphate synthase (rate-limiting step) and ornithine transcarbamoylase.

    Ornithine Transacarbamoylase Deficiency

    • Most common urea cycle deficiency, X-linked, leading to hyperammonaemia with severe symptoms.
    • Treatment involves dietary management, medication for nitrogen excretion, or liver transplantation.

    Metabolism of Carbon Skeletons

    • Glucogenic amino acids feed into pathways for gluconeogenesis.
    • Ketogenic amino acids convert to ketone bodies, important in energy metabolism.

    Essential and Non-Essential Amino Acids

    • Eight essential amino acids include isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
    • Semi-essential amino acids for children: arginine and histidine.

    Biosynthesis of Amino Acids

    • Non-essential amino acids formed from metabolic intermediates or through transamination reactions.
    • Notable examples include glycine from serine and tyrosine from phenylalanine.

    Cysteine and Methionine

    • Cysteine synthesized from methionine and serine; linked to heart disease through homocysteine accumulation.

    Protein Metabolism Overview

    • Entails protein synthesis from amino acids and their degradation into amino groups and carbon backbones, feeding into various metabolic pathways including gluconeogenesis and the urea cycle.

    Digestion and Absorption of Lipids

    • Lipid ingestion ranges from 25 to 160 g/day, primarily as triglycerides, with some phospholipids and cholesterol esters.
    • Essential fatty acids include linoleic and linolenic, vital for health, along with fat-soluble vitamins A, D, E, and K.

    Lipid Properties

    • Most lipids are insoluble in water, necessitating emulsification to facilitate digestion and absorption.
    • Short-chain fatty acids (< 10 carbons) can dissolve in water, easing transport in the blood.

    Emulsification

    • Bile salts emulsify lipids by breaking large droplets into smaller ones (0.5 – 1.0 mm), enhancing enzyme access to substrates.
    • Emulsified lipid droplets create a larger interface with aqueous environments.

    Bile Acids and Enzymes

    • Bile salts are derived from cholesterol; they are crucial for lipid digestion.
    • Pancreatic lipase, along with co-lipase, enables efficient breakdown of lipids and overcomes bile-salt inhibition.
    • Cholesterol esterase cleaves fatty acids from cholesterol esters and hydrolyzes triacylglycerols and monoacylglycerols.
    • Phospholipase hydrolyzes phospholipids into lysophospholipids.

    Absorption Mechanisms

    • Lipid breakdown products diffuse across the unstirred layer and enter enterocytes via diffusion or fatty acid transport proteins.
    • Short- and medium-chain fatty acids (4-12 carbons) can pass directly into the portal circulation via albumin binding; no micelles needed.
    • Fat-soluble vitamins’ absorption hinges on intact lipid-digesting mechanisms.

    Role of Enterocytes

    • Breakdown products are resynthesized into triglycerides and chylomicrons in enterocytes, mainly composed of apolipoprotein B-48.
    • Chylomicrons are secreted into the lymphatic system and eventually enter the bloodstream, providing a milky appearance to lymphatic fluid known as chyle.

    Malabsorption Syndromes

    • Malabsorption can be global (e.g., celiac disease) or partial (e.g., vitamin B12 deficiency).
    • Common causes include pancreatic insufficiency, inadequate brush border enzymes, mucosal surface damage, inflammatory bowel disease, infections, and surgery.

    Symptoms and Investigation

    • Malabsorption results in weight loss, weakness, steatorrhea, intestinal discomfort, and diarrhea.
    • Investigations involve imaging, endoscopy, biopsy, and serum enzymes, particularly in pancreatitis cases.

    Summary of Digestion Phases

    • Mouth: Mastication, emulsification, and slight lipid digestion via lingual lipase.
    • Stomach: Continued digestion with gastric lipase.
    • Small Intestine: Primary digestion through pancreatic enzymes and emulsification with bile salts.

    Learning Outcomes

    • Understand normal anatomy of mouth, oesophagus, and stomach.
    • Differentiate between benign and malignant tumours in the oropharynx, oesophagus, and stomach.
    • Identify common conditions affecting the mouth.
    • Recognize causes of salivary gland enlargement.
    • Discover causes of oesophagitis and gastritis.
    • Define Barrett's oesophagus as a precancerous condition.

    Oesophageal Anatomy

    • Oesophagus is composed of four layers: mucosa (squamous epithelium), submucosa (connective tissue, blood vessels, nerves), muscle layer, and adventitia (connective tissue).

    Dysphagia (Difficulty Swallowing)

    • Caused by lesions categorized into:
      • Lumen lesions: Foreign bodies, carcinomas.
      • Wall lesions: Tumours, scleroderma, strictures.
      • External lesions: Tumours, aortic aneurysms, lymphadenopathy.
      • Functional lesions: Achalasia.

    Anatomic Disorders of the Oesophagus

    • Developmental Abnormalities:

      • Atresia/Fistula associated with pulmonary issues (tracheo-oesophageal fistula).

    • Acquired Abnormalities:

      • Diverticula: True (all layers) vs False (only mucosa and submucosa); can be caused by pressure (pulsion) or local pathology (traction).
      • Webs/Rings:
        • Webs are thin membranes (2-3mm).
        • Rings consist of mucosal, submucosal, and fibrous bands.

    • Hiatus Hernia:

      • Occurs in 1-20% of adults; separation of diaphragmatic crura.
      • Two patterns: Sliding (95%) and Paraoesophageal.

    Oesophageal Motor Disorders

    • Achalasia: Characterized by failure to relax the lower oesophageal sphincter.
      • Three abnormalities: Aperistalsis, incomplete relaxation during swallowing, increased resting tone of the lower sphincter.
      • Causes include neural imbalances (degenerative conditions, diabetes) and secondary infections (e.g., Trypanosoma, polio).

    Oesophageal Abnormalities

    • Oesophageal Perforation: Commonly arises from instrumentation or severe vomiting; can result in a Mallory-Weiss tear and mediastinitis.

    • Oesophageal Varices: Dilated veins in submucosa due to portal hypertension; prevalent in cirrhotic patients.

    Inflammatory Disorders

    • Infective:

      • Fungal (Candida albicans) and viral (Herpes, CMV) infections can cause oesophagitis.

    • Physical Causes:

      • Due to irradiation or ingestion of caustic agents.

    • Reflux Oesophagitis:

      • Associated with raised abdominal pressure, hiatus hernia, smoking, and alcohol consumption.
      • Histological features include basal cell hyperplasia, increased eosinophils, and elongated lamina propria papillae.

    Oesophagogastric Junction

    • Junction between the squamous mucosa of the oesophagus and glandular mucosa of the stomach, designed to protect against trauma.

    Learning Outcomes

    • Understand normal anatomy of mouth, oesophagus, and stomach.
    • Differentiate between benign and malignant tumours in the oropharynx, oesophagus, and stomach.
    • Identify common conditions affecting the mouth.
    • Recognize causes of salivary gland enlargement.
    • Discover causes of oesophagitis and gastritis.
    • Define Barrett's oesophagus as a precancerous condition.

    Oesophageal Anatomy

    • Oesophagus is composed of four layers: mucosa (squamous epithelium), submucosa (connective tissue, blood vessels, nerves), muscle layer, and adventitia (connective tissue).

    Dysphagia (Difficulty Swallowing)

    • Caused by lesions categorized into:
      • Lumen lesions: Foreign bodies, carcinomas.
      • Wall lesions: Tumours, scleroderma, strictures.
      • External lesions: Tumours, aortic aneurysms, lymphadenopathy.
      • Functional lesions: Achalasia.

    Anatomic Disorders of the Oesophagus

    • Developmental Abnormalities:

      • Atresia/Fistula associated with pulmonary issues (tracheo-oesophageal fistula).

    • Acquired Abnormalities:

      • Diverticula: True (all layers) vs False (only mucosa and submucosa); can be caused by pressure (pulsion) or local pathology (traction).
      • Webs/Rings:
        • Webs are thin membranes (2-3mm).
        • Rings consist of mucosal, submucosal, and fibrous bands.

    • Hiatus Hernia:

      • Occurs in 1-20% of adults; separation of diaphragmatic crura.
      • Two patterns: Sliding (95%) and Paraoesophageal.

    Oesophageal Motor Disorders

    • Achalasia: Characterized by failure to relax the lower oesophageal sphincter.
      • Three abnormalities: Aperistalsis, incomplete relaxation during swallowing, increased resting tone of the lower sphincter.
      • Causes include neural imbalances (degenerative conditions, diabetes) and secondary infections (e.g., Trypanosoma, polio).

    Oesophageal Abnormalities

    • Oesophageal Perforation: Commonly arises from instrumentation or severe vomiting; can result in a Mallory-Weiss tear and mediastinitis.

    • Oesophageal Varices: Dilated veins in submucosa due to portal hypertension; prevalent in cirrhotic patients.

    Inflammatory Disorders

    • Infective:

      • Fungal (Candida albicans) and viral (Herpes, CMV) infections can cause oesophagitis.

    • Physical Causes:

      • Due to irradiation or ingestion of caustic agents.

    • Reflux Oesophagitis:

      • Associated with raised abdominal pressure, hiatus hernia, smoking, and alcohol consumption.
      • Histological features include basal cell hyperplasia, increased eosinophils, and elongated lamina propria papillae.

    Oesophagogastric Junction

    • Junction between the squamous mucosa of the oesophagus and glandular mucosa of the stomach, designed to protect against trauma.

    Learning Outcomes

    • Understand normal anatomy of mouth, oesophagus, and stomach.
    • Differentiate between benign and malignant tumours in the oropharynx, oesophagus, and stomach.
    • Identify common conditions affecting the mouth.
    • Recognize causes of salivary gland enlargement.
    • Discover causes of oesophagitis and gastritis.
    • Define Barrett's oesophagus as a precancerous condition.

    Oesophageal Anatomy

    • Oesophagus is composed of four layers: mucosa (squamous epithelium), submucosa (connective tissue, blood vessels, nerves), muscle layer, and adventitia (connective tissue).

    Dysphagia (Difficulty Swallowing)

    • Caused by lesions categorized into:
      • Lumen lesions: Foreign bodies, carcinomas.
      • Wall lesions: Tumours, scleroderma, strictures.
      • External lesions: Tumours, aortic aneurysms, lymphadenopathy.
      • Functional lesions: Achalasia.

    Anatomic Disorders of the Oesophagus

    • Developmental Abnormalities:

      • Atresia/Fistula associated with pulmonary issues (tracheo-oesophageal fistula).

    • Acquired Abnormalities:

      • Diverticula: True (all layers) vs False (only mucosa and submucosa); can be caused by pressure (pulsion) or local pathology (traction).
      • Webs/Rings:
        • Webs are thin membranes (2-3mm).
        • Rings consist of mucosal, submucosal, and fibrous bands.

    • Hiatus Hernia:

      • Occurs in 1-20% of adults; separation of diaphragmatic crura.
      • Two patterns: Sliding (95%) and Paraoesophageal.

    Oesophageal Motor Disorders

    • Achalasia: Characterized by failure to relax the lower oesophageal sphincter.
      • Three abnormalities: Aperistalsis, incomplete relaxation during swallowing, increased resting tone of the lower sphincter.
      • Causes include neural imbalances (degenerative conditions, diabetes) and secondary infections (e.g., Trypanosoma, polio).

    Oesophageal Abnormalities

    • Oesophageal Perforation: Commonly arises from instrumentation or severe vomiting; can result in a Mallory-Weiss tear and mediastinitis.

    • Oesophageal Varices: Dilated veins in submucosa due to portal hypertension; prevalent in cirrhotic patients.

    Inflammatory Disorders

    • Infective:

      • Fungal (Candida albicans) and viral (Herpes, CMV) infections can cause oesophagitis.

    • Physical Causes:

      • Due to irradiation or ingestion of caustic agents.

    • Reflux Oesophagitis:

      • Associated with raised abdominal pressure, hiatus hernia, smoking, and alcohol consumption.
      • Histological features include basal cell hyperplasia, increased eosinophils, and elongated lamina propria papillae.

    Oesophagogastric Junction

    • Junction between the squamous mucosa of the oesophagus and glandular mucosa of the stomach, designed to protect against trauma.

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    Description

    Test your understanding of protein absorption and processing in the body. This quiz covers the functions and synthesis of amino acids, the role of transaminase enzymes, and the involvement of amino acids in metabolic pathways. Perfect for students in the GIHEP module at the Royal College of Surgeons in Ireland.

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