Podcast
Questions and Answers
What is the primary purpose of proteolysis in protein metabolism?
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?
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?
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?
What is the role of transamination in amino acid metabolism?
In the urea cycle, what substance is primarily formed as a waste product?
In the urea cycle, what substance is primarily formed as a waste product?
Which amino acids are classified as essential amino acids?
Which amino acids are classified as essential amino acids?
What is the end product of the synthesis of tyrosine from phenylalanine?
What is the end product of the synthesis of tyrosine from phenylalanine?
Which of the following amino acids is considered semi-essential?
Which of the following amino acids is considered semi-essential?
From which metabolic intermediate is serine synthesized?
From which metabolic intermediate is serine synthesized?
If dietary availability of phenylalanine is restricted, what happens to tyrosine?
If dietary availability of phenylalanine is restricted, what happens to tyrosine?
Which enzyme is responsible for synthesizing glutamine from glutamate?
Which enzyme is responsible for synthesizing glutamine from glutamate?
What condition results from an inability to synthesize tyrosine?
What condition results from an inability to synthesize tyrosine?
Which amino acid is synthesized from α-ketoglutarate in the transamination process?
Which amino acid is synthesized from α-ketoglutarate in the transamination process?
What is the primary role of transaminase enzymes in the body?
What is the primary role of transaminase enzymes in the body?
Which of the following describes the identity of an amino acid?
Which of the following describes the identity of an amino acid?
Amino acids serve as precursors for all the following EXCEPT:
Amino acids serve as precursors for all the following EXCEPT:
What process is primarily responsible for the elimination of amino nitrogen from the body?
What process is primarily responsible for the elimination of amino nitrogen from the body?
Which amino acid is a precursor for the synthesis of the neurotransmitter serotonin?
Which amino acid is a precursor for the synthesis of the neurotransmitter serotonin?
How does the body utilize amino acids in energy-yielding metabolism?
How does the body utilize amino acids in energy-yielding metabolism?
Which of the following statements about essential amino acids is true?
Which of the following statements about essential amino acids is true?
What condition is exemplified by a defect in the urea cycle leading to accumulation of ammonia in the body?
What condition is exemplified by a defect in the urea cycle leading to accumulation of ammonia in the body?
Which organ primarily provides amino acids to circulation in the fasting state?
Which organ primarily provides amino acids to circulation in the fasting state?
In the process of transamination, which molecule is typically the acceptor of the amino group?
In the process of transamination, which molecule is typically the acceptor of the amino group?
What is the primary nitrogen disposal method in the body?
What is the primary nitrogen disposal method in the body?
Which enzyme is considered the rate-limiting step in the urea cycle?
Which enzyme is considered the rate-limiting step in the urea cycle?
What condition results from excess ammonia in the blood?
What condition results from excess ammonia in the blood?
Which amino acid primarily acts as a 'collector' of amino groups during transamination?
Which amino acid primarily acts as a 'collector' of amino groups during transamination?
What is the main effect of low energy levels on amino acid degradation?
What is the main effect of low energy levels on amino acid degradation?
Which cycle facilitates the transport of nitrogen from muscle to the liver?
Which cycle facilitates the transport of nitrogen from muscle to the liver?
What is one of the major symptoms of hyperammonaemia?
What is one of the major symptoms of hyperammonaemia?
Which amino acid is predominantly synthesized in muscle through transamination?
Which amino acid is predominantly synthesized in muscle through transamination?
A deficiency in which enzyme leads to the most common form of urea cycle disorder?
A deficiency in which enzyme leads to the most common form of urea cycle disorder?
Which of the following correctly describes the role of glutamate dehydrogenase?
Which of the following correctly describes the role of glutamate dehydrogenase?
What is the primary purpose of the urea cycle?
What is the primary purpose of the urea cycle?
What is the primary component of dietary lipids ingested by humans?
What is the primary component of dietary lipids ingested by humans?
What is the significance of short-chain fatty acids in lipid digestion?
What is the significance of short-chain fatty acids in lipid digestion?
Which of the following best describes how lipids are emulsified for digestion?
Which of the following best describes how lipids are emulsified for digestion?
Which vitamins are classified as fat-soluble vitamins?
Which vitamins are classified as fat-soluble vitamins?
What mechanism facilitates the absorption of lipids in the digestive system?
What mechanism facilitates the absorption of lipids in the digestive system?
What impact does malabsorption syndrome have on lipid digestion?
What impact does malabsorption syndrome have on lipid digestion?
Which statement accurately reflects the process of lipid digestion?
Which statement accurately reflects the process of lipid digestion?
What type of fatty acids must be obtained through diet because they are essential?
What type of fatty acids must be obtained through diet because they are essential?
Which enzyme binds to the surface of lipid droplets to facilitate lipid digestion?
Which enzyme binds to the surface of lipid droplets to facilitate lipid digestion?
How do bile salts contribute to lipid digestion?
How do bile salts contribute to lipid digestion?
What is the role of co-lipase in lipid digestion?
What is the role of co-lipase in lipid digestion?
What determines the caloric value of lipids in the diet?
What determines the caloric value of lipids in the diet?
Which enzyme is secreted as an inactive precursor and activated by trypsin?
Which enzyme is secreted as an inactive precursor and activated by trypsin?
What is the primary function of cholesterol esterase?
What is the primary function of cholesterol esterase?
What compound is responsible for activating pro-colipase?
What compound is responsible for activating pro-colipase?
Which of the following best describes the structure of micelles?
Which of the following best describes the structure of micelles?
What characterizes free fatty acids and monoacylglycerols in terms of solubility?
What characterizes free fatty acids and monoacylglycerols in terms of solubility?
What is the end product of lysophospholipase activity?
What is the end product of lysophospholipase activity?
Which gut hormone stimulates the contraction of the gallbladder and secretion of pancreatic enzymes?
Which gut hormone stimulates the contraction of the gallbladder and secretion of pancreatic enzymes?
What is the primary role of phospholipase in digestion?
What is the primary role of phospholipase in digestion?
What is the primary structural component of chylomicrons?
What is the primary structural component of chylomicrons?
How do short and medium-chain fatty acids primarily enter the bloodstream?
How do short and medium-chain fatty acids primarily enter the bloodstream?
Which vitamins rely on fat absorption mechanisms for normal absorption?
Which vitamins rely on fat absorption mechanisms for normal absorption?
What happens to bile salts after their role in digestion?
What happens to bile salts after their role in digestion?
Which component is NOT directly involved in the formation of mixed micelles?
Which component is NOT directly involved in the formation of mixed micelles?
What percentage of chylomicrons is composed of lipids?
What percentage of chylomicrons is composed of lipids?
Which process allows lipid breakdown products to enter enterocytes?
Which process allows lipid breakdown products to enter enterocytes?
What is the primary transportation mechanism for lipids within the lymphatic system?
What is the primary transportation mechanism for lipids within the lymphatic system?
What is a consequence of fat malabsorption in terms of vitamin absorption?
What is a consequence of fat malabsorption in terms of vitamin absorption?
Which phase of chylomicron formation occurs at the rough endoplasmic reticulum?
Which phase of chylomicron formation occurs at the rough endoplasmic reticulum?
What is the primary consequence of global malabsorption in a patient with celiac disease?
What is the primary consequence of global malabsorption in a patient with celiac disease?
Which type of absorption impairment is characterized by deficiencies of specific nutrients such as vitamin B12?
Which type of absorption impairment is characterized by deficiencies of specific nutrients such as vitamin B12?
What role does indigestible material, often referred to as fiber, play in the gastrointestinal tract?
What role does indigestible material, often referred to as fiber, play in the gastrointestinal tract?
Which condition is associated with inadequate mucosal surface due to flattening of the villi?
Which condition is associated with inadequate mucosal surface due to flattening of the villi?
What is a potential outcome of pancreatic insufficiency in the context of malabsorption?
What is a potential outcome of pancreatic insufficiency in the context of malabsorption?
During anaerobic fermentation by intestinal flora, which type of gas is not produced?
During anaerobic fermentation by intestinal flora, which type of gas is not produced?
Which of the following conditions is likely to lead to a loss of intrinsic factor, affecting vitamin B12 absorption?
Which of the following conditions is likely to lead to a loss of intrinsic factor, affecting vitamin B12 absorption?
What commonly accompanies malabsorption and is characterized by the presence of fat in feces?
What commonly accompanies malabsorption and is characterized by the presence of fat in feces?
In which scenario is an inflammatory response likely to cause malabsorption in the jejunum?
In which scenario is an inflammatory response likely to cause malabsorption in the jejunum?
What specific factor is crucial for normal nutrient absorption in the GIT?
What specific factor is crucial for normal nutrient absorption in the GIT?
What is the primary characteristic of the mucosa in the oesophagus?
What is the primary characteristic of the mucosa in the oesophagus?
Which of the following is NOT a common cause of dysphagia?
Which of the following is NOT a common cause of dysphagia?
Barrett's oesophagus is defined as a condition where which type of tissue replaces the normal squamous epithelium?
Barrett's oesophagus is defined as a condition where which type of tissue replaces the normal squamous epithelium?
What are the structural layers of the oesophagus from innermost to outermost?
What are the structural layers of the oesophagus from innermost to outermost?
Which type of abnormality is often associated with pulmonary issues in infants?
Which type of abnormality is often associated with pulmonary issues in infants?
What distinguishes 'true' diverticula from 'false' diverticula?
What distinguishes 'true' diverticula from 'false' diverticula?
Which type of hernia constitutes 95% of hiatus hernias?
Which type of hernia constitutes 95% of hiatus hernias?
What characterizes the functional obstruction seen in achalasia?
What characterizes the functional obstruction seen in achalasia?
Which condition is most often associated with tearing of the lower esophagus after severe vomiting?
Which condition is most often associated with tearing of the lower esophagus after severe vomiting?
What is a common infectious cause of secondary achalasia?
What is a common infectious cause of secondary achalasia?
What histological feature is characteristic of reflux esophagitis?
What histological feature is characteristic of reflux esophagitis?
What condition is characterized by dilated veins in the submucosa of the esophagus?
What condition is characterized by dilated veins in the submucosa of the esophagus?
Which anatomical feature marks the junction between the esophagus and the stomach?
Which anatomical feature marks the junction between the esophagus and the stomach?
Which part of the oesophagus is primarily composed of squamous epithelium?
Which part of the oesophagus is primarily composed of squamous epithelium?
What is a common cause of dysphagia related to lesions outside the wall of the oesophagus?
What is a common cause of dysphagia related to lesions outside the wall of the oesophagus?
Which condition is characterized by the abnormal growth of the oesophageal lining and is specifically defined as Barrett's oesophagus?
Which condition is characterized by the abnormal growth of the oesophageal lining and is specifically defined as Barrett's oesophagus?
What is one of the developmental abnormalities associated with the oesophagus commonly recognized?
What is one of the developmental abnormalities associated with the oesophagus commonly recognized?
Which of the following is NOT a recognized category causing dysphagia?
Which of the following is NOT a recognized category causing dysphagia?
What distinguishes true diverticula from false diverticula?
What distinguishes true diverticula from false diverticula?
Which feature is characteristic of achalasia?
Which feature is characteristic of achalasia?
What is the primary cause of Mallory-Weiss tears?
What is the primary cause of Mallory-Weiss tears?
Which abnormality is associated with esophageal varices?
Which abnormality is associated with esophageal varices?
What is a common secondary cause of achalasia?
What is a common secondary cause of achalasia?
Pulsion diverticula are primarily caused by what mechanism?
Pulsion diverticula are primarily caused by what mechanism?
Which histological feature is NOT associated with reflux esophagitis?
Which histological feature is NOT associated with reflux esophagitis?
What anatomical separation is involved in a hiatus hernia?
What anatomical separation is involved in a hiatus hernia?
What is the primary function of the submucosa in the esophagus?
What is the primary function of the submucosa in the esophagus?
Which of the following conditions is most likely to cause dysphagia due to lesions affecting function?
Which of the following conditions is most likely to cause dysphagia due to lesions affecting function?
Which structure provides connective tissue support to the esophagus?
Which structure provides connective tissue support to the esophagus?
What is the most common developmental abnormality of the esophagus?
What is the most common developmental abnormality of the esophagus?
Barrett's esophagus is defined primarily by which of the following pathological changes?
Barrett's esophagus is defined primarily by which of the following pathological changes?
What distinguishes a 'true' diverticulum from a 'false' diverticulum?
What distinguishes a 'true' diverticulum from a 'false' diverticulum?
Which of the following correctly describes the primary cause of achalasia?
Which of the following correctly describes the primary cause of achalasia?
What anatomical feature is MOST commonly associated with hiatus hernia?
What anatomical feature is MOST commonly associated with hiatus hernia?
Which statement correctly describes the pathology of oesophageal varices?
Which statement correctly describes the pathology of oesophageal varices?
What type of abnormality does a 'Mallory-Weiss' tear represent?
What type of abnormality does a 'Mallory-Weiss' tear represent?
Which statement best captures the histological features of reflux oesophagitis?
Which statement best captures the histological features of reflux oesophagitis?
Which condition is commonly associated with viral causes for oesophageal inflammation?
Which condition is commonly associated with viral causes for oesophageal inflammation?
What role does traction play in the formation of diverticula?
What role does traction play in the formation of diverticula?
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.
