Oesophageal Sphincter Anatomy Quiz
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Questions and Answers

What is the primary function of the upper oesophageal sphincter (UOS)?

  • Prevent air from entering the oesophagus during breathing and stop backflow into the pharynx (correct)
  • Prevent gastric reflux
  • Separate the oesophagus from the stomach
  • Facilitate the movement of food into the stomach

    • Where is the lower oesophageal sphincter (LOS) located?

  • At the junction of the oesophagus and pharynx
  • Below the diaphragm
  • At the top of the oesophagus
  • At the gastro-oesophageal junction (GOJ) (correct)

    • What is the main role of the diaphragm in relation to the lower oesophageal sphincter (LOS)?

  • To relax the LOS
  • To increase the motility of the oesophagus
  • To support and maintain the tone of the LOS (correct)
  • To separate the oesophagus from the trachea

    • What is the typical distance from the incisors to the gastro-oesophageal junction (GOJ) during an upper endoscopy?

    <p>40 cm</p> Signup and view all the answers

    Which of the following is true about the upper oesophageal sphincter (UOS)?

    <p>It prevents the backflow of food and liquids into the pharynx.</p> Signup and view all the answers

    What is the primary function of the fundus in the stomach?

    <p>To store undigested food and gases released during digestion</p> Signup and view all the answers

    Which part of the stomach is responsible for mixing food with digestive juices to form chyme?

    <p>Body</p> Signup and view all the answers

    What is the function of the antrum in the stomach?

    <p>To grind food and regulate its passage to the small intestine</p> Signup and view all the answers

    The pyloric sphincter serves what main purpose?

    <p>To regulate the flow of partially digested food into the duodenum and prevent backflow</p> Signup and view all the answers

    Which of the following correctly describes the location of the fundus?

    <p>The uppermost part of the stomach, next to the diaphragm</p> Signup and view all the answers

    What is the approximate length of the duodenum?

    <p>30 cm</p> Signup and view all the answers

    What initiates the digestion process in the duodenum?

    <p>Reception of partially digested food from the stomach</p> Signup and view all the answers

    Which structure is responsible for allowing bile and pancreatic enzymes to enter the duodenum?

    <p>Major duodenal papilla</p> Signup and view all the answers

    What function does the duodenal bulb serve in the digestive process?

    <p>Transition zone for chyme from the stomach</p> Signup and view all the answers

    The Ligament of Treitz marks the boundary between which two segments of the small intestine?

    <p>Duodenum and jejunum</p> Signup and view all the answers

    Which section of the small intestine is primarily responsible for most nutrient absorption?

    <p>Jejunum</p> Signup and view all the answers

    What is the main function of the ileum?

    <p>To absorb vitamin B12 and bile salts</p> Signup and view all the answers

    Which structure prevents the backflow of contents from the large intestine into the small intestine?

    <p>Ileocaecal valve</p> Signup and view all the answers

    In which part of the small intestine does the mixing of chyme with digestive juices primarily occur?

    <p>Duodenum</p> Signup and view all the answers

    How does the structure of the jejunum aid in nutrient absorption?

    <p>It has a highly folded surface with many villi to increase surface area.</p> Signup and view all the answers

    In which quadrant of the abdomen is the liver primarily located?

    <p>Right upper quadrant</p> Signup and view all the answers

    What key role does bile produced by the liver play in digestion?

    <p>Digesting and absorbing fats in the small intestine</p> Signup and view all the answers

    What is the primary function of Kupffer cells in the liver?

    <p>Filtering blood and breaking down bacteria and foreign particles</p> Signup and view all the answers

    Which of the following vitamins is not stored in the liver?

    <p>Vitamin C</p> Signup and view all the answers

    How does the liver contribute to the body's blood clotting process?

    <p>By producing proteins necessary for blood clotting</p> Signup and view all the answers

    Which types of cells in the Islets of Langerhans produce hormones that regulate blood glucose levels?

    <p>Alpha and beta cells</p> Signup and view all the answers

    Which enzyme is specifically responsible for the digestion of fats in the human body?

    <p>Lipase</p> Signup and view all the answers

    What is the role of the common bile duct in relation to the pancreas?

    <p>To merge with the main pancreatic duct before entering the duodenum</p> Signup and view all the answers

    Which hormone produced by alpha cells decreases blood glucose levels?

    <p>Glucagon</p> Signup and view all the answers

    Which of the following enzymes is NOT secreted by the pancreas?

    <p>Pepsin</p> Signup and view all the answers

    What is the primary function of the common bile duct?

    <p>To carry bile from the liver and gallbladder to the duodenum</p> Signup and view all the answers

    Which duct connects the gallbladder to the common bile duct?

    <p>Cystic duct</p> Signup and view all the answers

    What is the role of the Ampulla of Vater?

    <p>To form a shared opening for the pancreatic duct and common bile duct</p> Signup and view all the answers

    The Sphincter of Oddi controls the flow of which substances into the duodenum?

    <p>Bile and pancreatic enzymes</p> Signup and view all the answers

    Where is the head of the pancreas located?

    <p>In the curve of the duodenum</p> Signup and view all the answers

    What is the function of the gallbladder?

    <p>To store and concentrate bile produced by the liver</p> Signup and view all the answers

    Which structure prevents the backflow of intestinal contents into the pancreatic and bile ducts?

    <p>Sphincter of Oddi</p> Signup and view all the answers

    What substance does the gallbladder primarily store?

    <p>Bile produced by the liver</p> Signup and view all the answers

    What is the main function of the caecum?

    <p>To connect the small intestine to the colon and absorb fluids and salts</p> Signup and view all the answers

    Which part of the colon forms the hepatic flexure?

    <p>Between the ascending and transverse colon</p> Signup and view all the answers

    What is the primary function of the transverse colon?

    <p>To continue the absorption and fermentation process</p> Signup and view all the answers

    Which colon segment connects directly to the rectum?

    <p>Sigmoid colon</p> Signup and view all the answers

    Where is the splenic flexure located?

    <p>Between the transverse colon and descending colon</p> Signup and view all the answers

    What is the main role of the rectum?

    <p>To store and expel feces during defecation</p> Signup and view all the answers

    The anus is part of which system?

    <p>Digestive system</p> Signup and view all the answers

    The appendix is attached to which area of the colon?

    <p>Caecum</p> Signup and view all the answers

    What is the main structural component of the serosa layer of the GI tract?

    <p>Connective tissue and epithelium</p> Signup and view all the answers

    How does the muscularis mucosae contribute to the digestive process?

    <p>By enhancing the absorption process through slight movements</p> Signup and view all the answers

    Which layer of the GI tract is responsible for peristalsis?

    <p>Muscularis</p> Signup and view all the answers

    What is found in the submucosa layer of the GI tract?

    <p>Submucosal plexus (Meissner's plexus)</p> Signup and view all the answers

    What role does the myenteric plexus play in the GI tract?

    <p>It controls GI motility between muscle layers</p> Signup and view all the answers

    Which layer of the GI tract directly contacts food?

    <p>Mucosa</p> Signup and view all the answers

    Which of the following is NOT a component of the mucosa layer?

    <p>Myenteric plexus</p> Signup and view all the answers

    What action do the circular muscles perform within the muscularis layer?

    <p>Contracts behind a food bolus to push it forward</p> Signup and view all the answers

    What is the primary role of the mesentery?

    <p>To attach the intestines to the posterior abdominal wall and support them</p> Signup and view all the answers

    Which of the following describes a key function of the mesentery?

    <p>Provides a pathway for blood vessels, lymphatic vessels, and nerves</p> Signup and view all the answers

    How does the mesentery contribute to the blood supply of the intestines?

    <p>It allows oxygenated blood to be supplied to the intestines and nutrient-rich blood to be carried to the liver</p> Signup and view all the answers

    What role do the lymphatic vessels in the mesentery play?

    <p>They absorb and transport fats and play a role in immune functions</p> Signup and view all the answers

    The mesentery helps maintain communication between the intestines and the nervous system through:

    <p>Nerves</p> Signup and view all the answers

    Which of the following is NOT a function of the mesentery?

    <p>Secreting digestive enzymes</p> Signup and view all the answers

    What structural characteristic of the mesentery aids in its functions?

    <p>Dense connective tissue framework</p> Signup and view all the answers

    Which description best encapsulates the relationship between the mesentery and intestinal health?

    <p>It is crucial for maintaining structural integrity and nutrient transport.</p> Signup and view all the answers

    Which artery is primarily responsible for supplying blood to the stomach, spleen, and liver?

    <p>Coeliac artery (Celiac trunk)</p> Signup and view all the answers

    What does the superior mesenteric artery (SMA) supply blood to?

    <p>Most of the small intestine and part of the large intestine</p> Signup and view all the answers

    Which artery supplies blood to the descending colon, sigmoid colon, and rectum?

    <p>Inferior mesenteric artery (IMA)</p> Signup and view all the answers

    Which artery specifically provides blood to the liver?

    <p>Hepatic artery</p> Signup and view all the answers

    Which branch of the coeliac artery is responsible for supplying blood to the spleen?

    <p>Splenic artery</p> Signup and view all the answers

    The pancreaticoduodenal arteries supply blood to which specific structures?

    <p>Duodenum and pancreas</p> Signup and view all the answers

    Which artery branches from the superior mesenteric artery (SMA) to supply the appendix?

    <p>Appendicular artery</p> Signup and view all the answers

    The jejunal and ileal arteries are branches of which major artery?

    <p>Superior mesenteric artery (SMA)</p> Signup and view all the answers

    Which vein is responsible for draining blood from the kidneys into the Inferior Vena Cava (IVC)?

    <p>Renal vein</p> Signup and view all the answers

    Into which structure does the right gonadal vein drain directly?

    <p>Inferior Vena Cava (IVC)</p> Signup and view all the answers

    Where typically does the left gonadal vein drain before reaching the IVC?

    <p>Left renal vein</p> Signup and view all the answers

    Which vein is responsible for returning blood from the liver to the IVC?

    <p>Hepatic vein</p> Signup and view all the answers

    What two veins unite to form the common iliac veins?

    <p>Internal and external iliac veins</p> Signup and view all the answers

    Which vein drains blood from the diaphragm and contributes to the IVC?

    <p>Phrenic vein</p> Signup and view all the answers

    Where does the left adrenal (suprarenal) vein typically empty?

    <p>Left renal vein</p> Signup and view all the answers

    What is the main function of the Inferior Vena Cava (IVC)?

    <p>To drain deoxygenated blood from the lower body and return it to the heart</p> Signup and view all the answers

    What organ does the hepatic portal vein primarily supply blood to?

    <p>Liver</p> Signup and view all the answers

    Which two veins converge to create the hepatic portal vein?

    <p>Superior mesenteric vein and splenic vein</p> Signup and view all the answers

    From which organs does the splenic vein primarily drain blood?

    <p>Spleen, portions of the stomach, and pancreas</p> Signup and view all the answers

    Which vein does the inferior mesenteric vein typically merge with before entering the hepatic portal vein?

    <p>Splenic vein</p> Signup and view all the answers

    Which vein is responsible for draining blood from the small intestine, cecum, and ascending colon?

    <p>Superior mesenteric vein</p> Signup and view all the answers

    What is the primary purpose of the blood carried by the hepatic portal vein?

    <p>To transport nutrient-rich blood from the digestive organs to the liver for processing</p> Signup and view all the answers

    The inferior mesenteric vein primarily drains blood from which regions of the intestine?

    <p>Descending colon, sigmoid colon, and rectum</p> Signup and view all the answers

    Which vein does NOT contribute directly to the hepatic portal vein's formation?

    <p>Hepatic vein</p> Signup and view all the answers

    What percentage of blood supply to the liver is provided by the hepatic portal vein?

    <p>70%</p> Signup and view all the answers

    Which blood vessel carries nutrient-rich blood from the gastrointestinal tract to the liver?

    <p>Hepatic portal vein</p> Signup and view all the answers

    What percentage of the liver's oxygen requirement is supplied by the hepatic artery?

    <p>30%</p> Signup and view all the answers

    Which vessel drains deoxygenated blood from the liver to the Inferior Vena Cava?

    <p>Hepatic vein</p> Signup and view all the answers

    What primary function does the hepatic portal vein serve in hepatic circulation?

    <p>Carries nutrient-rich blood for processing</p> Signup and view all the answers

    The hepatic vein connects the liver to which major blood vessel?

    <p>Inferior Vena Cava (IVC)</p> Signup and view all the answers

    Which statement about the hepatic artery is true?

    <p>It provides oxygen-rich blood to the liver.</p> Signup and view all the answers

    What is the percentage of blood supplied to the liver by the hepatic artery?

    <p>30%</p> Signup and view all the answers

    What are the primary blood vessels that supply blood to the liver?

    <p>Hepatic portal vein and hepatic artery</p> Signup and view all the answers

    What are hepatic sinusoids?

    <p>Specialized capillaries in the liver where blood from the hepatic artery and portal vein mix</p> Signup and view all the answers

    What happens after blood passes through the hepatic sinusoids?

    <p>It collects in hepatic venules that channel it toward larger hepatic veins</p> Signup and view all the answers

    The hepatic veins drain blood into which structure?

    <p>Inferior Vena Cava (IVC)</p> Signup and view all the answers

    Which of the following best describes the role of the liver in processing blood received from the hepatic portal vein?

    <p>Processes and detoxifies substances absorbed from the digestive tract</p> Signup and view all the answers

    What is the significance of the mixing of blood in the hepatic sinusoids?

    <p>It facilitates metabolic functions by combining oxygen-rich and nutrient-rich blood</p> Signup and view all the answers

    What is the final step in the hepatic circulation before blood re-joins systemic circulation?

    <p>It enters systemic circulation through the hepatic veins</p> Signup and view all the answers

    What role does the liver play regarding toxins absorbed from the digestive tract?

    <p>It breaks down and converts toxins into harmless substances</p> Signup and view all the answers

    What function does the liver serve in relation to the nutrients absorbed from the digestive tract?

    <p>It processes nutrients to convert them into usable forms for the body.</p> Signup and view all the answers

    Which component of the liver is primarily responsible for producing bile?

    <p>Hepatocytes</p> Signup and view all the answers

    What role do Kupffer cells specifically play in the liver?

    <p>They are involved in phagocytizing pathogens and debris in the blood.</p> Signup and view all the answers

    How does the liver effect changes in blood glucose levels?

    <p>It maintains glucose levels by synthesizing and breaking down glycogen.</p> Signup and view all the answers

    Which of the following statements about detoxification in the liver is incorrect?

    <p>The liver excretes toxins directly into the bloodstream.</p> Signup and view all the answers

    What is the primary role of the hepatic sinusoids in the liver?

    <p>They facilitate the interaction between blood and liver cells for processing.</p> Signup and view all the answers

    Which of the following substances is NOT processed by the liver?

    <p>Excess carbon dioxide</p> Signup and view all the answers

    After processing in the liver, blood leaves through which structure?

    <p>Central vein</p> Signup and view all the answers

    What is portal hypertension?

    <p>Increased pressure in the portal vein system due to resistance in the liver</p> Signup and view all the answers

    What is the most common cause of portal hypertension?

    <p>Cirrhosis</p> Signup and view all the answers

    Esophageal and rectal varices can occur due to portal hypertension because:

    <p>Blood is rerouted to other veins, leading to swelling and fragility</p> Signup and view all the answers

    Ascites is characterized by:

    <p>Fluid buildup in the abdominal cavity</p> Signup and view all the answers

    Why does ascites develop in patients with portal hypertension?

    <p>High portal pressure and low albumin levels in the blood</p> Signup and view all the answers

    Which of the following can be a cause of portal vein thrombosis?

    <p>Blood clot formation in the portal vein</p> Signup and view all the answers

    What is a significant clinical complication associated with esophageal varices?

    <p>Life-threatening bleeding if the varices rupture</p> Signup and view all the answers

    What role do low albumin levels play in the development of complications in portal hypertension?

    <p>They impair water retention in blood vessels, leading to ascites</p> Signup and view all the answers

    What is the primary function of lymph in the body?

    <p>To collect and transport excess interstitial fluid from tissues back to the bloodstream</p> Signup and view all the answers

    Which type of cell is predominantly found in lymph and is essential for immune responses?

    <p>Lymphocytes</p> Signup and view all the answers

    Through which structures does lymph pass that help filter harmful substances and house immune cells?

    <p>Lymph nodes</p> Signup and view all the answers

    The thoracic duct empties lymph into which blood vessel?

    <p>Left subclavian vein</p> Signup and view all the answers

    What is the primary role of the right lymphatic duct?

    <p>To drain lymph from the right upper part of the body into the right subclavian vein</p> Signup and view all the answers

    Which of the following best describes the lacteals?

    <p>Lymphatic capillaries in the small intestine that absorb fats and proteins</p> Signup and view all the answers

    How does the lymphatic system contribute to fluid homeostasis?

    <p>By absorbing excess tissue fluid and returning it to the bloodstream</p> Signup and view all the answers

    What is the main function of lymph nodes in the lymphatic system?

    <p>To filter pathogens and foreign particles from lymph</p> Signup and view all the answers

    What area of the body does the right lymphatic duct drain?

    <p>The right upper quadrant, including the right side of the head, neck, arm, and thorax</p> Signup and view all the answers

    Where does the right lymphatic duct empty lymph into the bloodstream?

    <p>Right subclavian vein</p> Signup and view all the answers

    The thoracic duct drains lymph from which areas of the body?

    <p>The left upper quadrant and both lower quadrants of the body</p> Signup and view all the answers

    Where does the thoracic duct empty lymph into the bloodstream?

    <p>Left subclavian vein</p> Signup and view all the answers

    The cisterna chyli is:

    <p>A dilated sac in the abdomen where the thoracic duct begins</p> Signup and view all the answers

    What is a primary function of lymphatic drainage?

    <p>To maintain fluid balance by returning excess interstitial fluid to the bloodstream</p> Signup and view all the answers

    Which duct is responsible for draining the lower body?

    <p>Thoracic duct</p> Signup and view all the answers

    Which of the following represents a clinical significance of understanding lymphatic drainage?

    <p>It helps identify lymphatic disorders and potential treatments.</p> Signup and view all the answers

    What is the Enteric Nervous System (ENS) often referred to as?

    <p>The “gut brain”</p> Signup and view all the answers

    What is the primary function of sensory neurons in the Enteric Nervous System?

    <p>To detect changes in the gut environment</p> Signup and view all the answers

    Which of the following best describes the role of motor neurons in the ENS?

    <p>To control smooth muscle contraction and secretion in the GI tract</p> Signup and view all the answers

    The sympathetic nervous system (SNS) affects the GI system by:

    <p>Decreasing GI motility and secretion and increasing sphincter tone</p> Signup and view all the answers

    What function does the parasympathetic nervous system (PNS) serve in the GI system?

    <p>It promotes digestion by increasing GI motility and secretion</p> Signup and view all the answers

    Which nerve is primarily involved in parasympathetic stimulation of the GI system?

    <p>Vagus nerve</p> Signup and view all the answers

    What activities are controlled by voluntary nerves in the GI system?

    <p>Control of the external anal sphincter and mastication</p> Signup and view all the answers

    The interaction between the enteric nervous system (ENS) and central nervous system (CNS) is characterized by what?

    <p>The ENS can function autonomously but is modulated by the CNS</p> Signup and view all the answers

    What is the primary function of enteric hormones in the GI tract?

    <p>To act as messengers that control gastric secretion and motility</p> Signup and view all the answers

    Which hormone stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder?

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

    Amylase is an enzyme that breaks down which type of molecule?

    <p>Complex carbohydrates into smaller sugars</p> Signup and view all the answers

    What is the role of peptidases in the digestive system?

    <p>To break down proteins into peptides and amino acids</p> Signup and view all the answers

    Which enzyme is responsible for breaking down fats into fatty acids and glycerol?

    <p>Lipase</p> Signup and view all the answers

    Bile acids are important for which digestive process?

    <p>Fat emulsification for easier digestion</p> Signup and view all the answers

    Which molecule is essential for vitamin B12 absorption in the small intestine?

    <p>Intrinsic factor</p> Signup and view all the answers

    Oligosaccharidases function primarily to:

    <p>Further break down smaller carbohydrates into simpler sugars for absorption</p> Signup and view all the answers

    What is the primary purpose of mastication?

    <p>To increase the surface area of food for enzyme action by breaking it into smaller pieces</p> Signup and view all the answers

    Which enzyme found in saliva begins the digestion of carbohydrates?

    <p>Salivary amylase</p> Signup and view all the answers

    What type of fluid produced by the sublingual and submandibular glands helps in forming a bolus?

    <p>Mucus and serous fluid</p> Signup and view all the answers

    The parotid gland releases saliva through which duct?

    <p>Parotid/Stensen’s duct</p> Signup and view all the answers

    The function of mucus in saliva is to:

    <p>Bind food particles together and act as a lubricant for easy swallowing</p> Signup and view all the answers

    Salivary amylase breaks down which type of molecule?

    <p>Polysaccharides (complex starches) into simpler sugars</p> Signup and view all the answers

    Which salivary gland contributes the most to the production of mucus in saliva?

    <p>Submandibular gland</p> Signup and view all the answers

    What is the main role of serous fluid in saliva?

    <p>To aid in lubrication and provide a medium for enzymes to act on food</p> Signup and view all the answers

    What role does the tongue play in the oropharyngeal phase of swallowing?

    <p>It pushes the food bolus toward the back of the mouth for swallowing</p> Signup and view all the answers

    What is the primary function of the valleculae during the swallowing process?

    <p>Small spaces at the base of the tongue that help organize the bolus</p> Signup and view all the answers

    What is the function of the epiglottis during the oropharyngeal phase of swallowing?

    <p>To prevent food from entering the trachea by folding over it</p> Signup and view all the answers

    How does the pharyngeal wall contribute to the swallowing process?

    <p>It moves forward to help propel the bolus into the esophagus</p> Signup and view all the answers

    In what manner does the oropharyngeal phase of swallowing start?

    <p>Voluntary but transitions to an involuntary reflex</p> Signup and view all the answers

    Which of the following is not involved in the oropharyngeal phase of swallowing?

    <p>Peristaltic movement in the esophagus</p> Signup and view all the answers

    What is the role of the epiglottis in protecting the airway during the oropharyngeal phase?

    <p>It closes the trachea to prevent aspiration</p> Signup and view all the answers

    What anatomical change occurs when the pharyngeal wall contracts during swallowing?

    <p>It creates a pathway for food to enter the esophagus</p> Signup and view all the answers

    What is the primary function of the upper oesophageal sphincter (UOS) during swallowing?

    <p>To relax and permit the bolus to move into the esophagus</p> Signup and view all the answers

    How does gravity influence the oesophageal phase of swallowing?

    <p>It assists the food bolus movement especially when upright</p> Signup and view all the answers

    What is the significance of the lower oesophageal sphincter (LOS) closing after the food bolus has entered the stomach?

    <p>To ensure food does not return to the pharynx</p> Signup and view all the answers

    Which type of muscle contractions are primarily responsible for the movement of the food bolus through the esophagus?

    <p>Peristaltic muscle contractions</p> Signup and view all the answers

    What kind of control does the autonomic nervous system exert on the oesophageal phase of swallowing?

    <p>Involuntary control facilitating the swallowing process</p> Signup and view all the answers

    What could occur if the lower oesophageal sphincter does not close properly following swallowing?

    <p>Acid reflux into the esophagus</p> Signup and view all the answers

    In which way does the food bolus rely on gravity during the oesophageal phase?

    <p>It facilitates movement towards the stomach when standing or sitting.</p> Signup and view all the answers

    What happens to the upper oesophageal sphincter (UOS) once the food bolus passes through?

    <p>It closes to prevent backflow into the pharynx.</p> Signup and view all the answers

    What is the typical pH range of gastric juice?

    <p>1.5 to 3.5</p> Signup and view all the answers

    Which enzyme produced by the stomach is primarily responsible for protein digestion?

    <p>Pepsin</p> Signup and view all the answers

    What regulatory molecule does the stomach produce to stimulate acid production?

    <p>Gastrin</p> Signup and view all the answers

    The mechanical action of the stomach includes mixing food with gastric juice to form:

    <p>Chyme</p> Signup and view all the answers

    The stomach pushes chyme toward the pylorus to:

    <p>Propel chyme into the duodenum for further digestion</p> Signup and view all the answers

    Which of the following substances is absorbed in the stomach?

    <p>Alcohol and lipid-soluble drugs</p> Signup and view all the answers

    What is the primary function of gastric juice?

    <p>To chemically break down food, especially proteins, with digestive enzymes and acid</p> Signup and view all the answers

    The stomach’s mechanical function of mixing and propulsion helps:

    <p>Combine food with gastric juice for efficient digestion</p> Signup and view all the answers

    What is the primary role of gastrin in digestion?

    <p>To stimulate the production of gastric juice by increasing HCl secretion</p> Signup and view all the answers

    Which hormone released by enteroendocrine cells is primarily responsible for signaling hunger?

    <p>Ghrelin</p> Signup and view all the answers

    How does histamine play a role in the digestive process in the stomach?

    <p>It promotes the secretion of HCl by parietal cells.</p> Signup and view all the answers

    What stimulates an increase in ghrelin levels?

    <p>Before meals to signal hunger</p> Signup and view all the answers

    Which cells in the stomach primarily release gastrin?

    <p>G cells</p> Signup and view all the answers

    What effect does gastrin have on the digestive system?

    <p>Promotes acid secretion in the stomach</p> Signup and view all the answers

    Which of the following hormones acts directly on parietal cells to enhance acid production?

    <p>Gastrin</p> Signup and view all the answers

    Why is histamine essential for digestion in the stomach?

    <p>It stimulates HCl secretion for optimal enzyme function.</p> Signup and view all the answers

    What is the primary substance secreted by chief cells in the stomach?

    <p>Pepsinogen</p> Signup and view all the answers

    Pepsinogen is activated to pepsin in the presence of which substance?

    <p>Hydrochloric acid (HCl)</p> Signup and view all the answers

    What is the role of pepsin in the digestive process?

    <p>It begins the digestion of proteins by breaking them into smaller peptides.</p> Signup and view all the answers

    Where are chief cells located in the stomach?

    <p>In the gastric glands of the stomach lining</p> Signup and view all the answers

    The conversion of pepsinogen to pepsin is an example of:

    <p>Zymogen activation</p> Signup and view all the answers

    Which cells in the stomach secrete hydrochloric acid (HCl) that activates pepsinogen?

    <p>Parietal cells</p> Signup and view all the answers

    Why is pepsin secreted as pepsinogen and not in its active form?

    <p>To prevent the digestion of the stomach’s own cells</p> Signup and view all the answers

    What happens to proteins after they are partially digested by pepsin in the stomach?

    <p>They move to the small intestine for further digestion and absorption.</p> Signup and view all the answers

    What is one of the main substances produced by parietal cells?

    <p>Intrinsic factor</p> Signup and view all the answers

    What is the purpose of intrinsic factor produced by parietal cells?

    <p>To aid in the absorption of vitamin B12 in the ileum</p> Signup and view all the answers

    How does hydrochloric acid (HCl) produced by parietal cells aid in digestion?

    <p>It activates pepsinogen into pepsin</p> Signup and view all the answers

    Which condition can result from a deficiency in intrinsic factor?

    <p>Pernicious anemia</p> Signup and view all the answers

    What function does hydrochloric acid (HCl) serve in the stomach?

    <p>Creates an optimal pH for digestive enzymes and denatures proteins</p> Signup and view all the answers

    The secretion of hydrogen ions by parietal cells is mainly facilitated by which mechanism?

    <p>Proton pump (H+/K+ ATPase)</p> Signup and view all the answers

    How does HCl contribute to the stomach’s defense against pathogens?

    <p>It kills ingested bacteria by creating an acidic environment</p> Signup and view all the answers

    Which part of the small intestine is responsible for absorbing vitamin B12 with the help of intrinsic factor?

    <p>Ileum</p> Signup and view all the answers

    Which receptor on the parietal cell surface is stimulated by histamine to increase HCl secretion?

    <p>H2 receptor</p> Signup and view all the answers

    What action does gastrin have when it binds to its receptor on parietal cells?

    <p>Promotes the release of HCl by stimulating the proton pump</p> Signup and view all the answers

    Acetylcholine (ACh) released from the vagus nerve primarily acts on which cells to enhance acid secretion?

    <p>Parietal cells</p> Signup and view all the answers

    What is the primary function of carbonic anhydrase in parietal cells?

    <p>To catalyze the formation of carbonic acid</p> Signup and view all the answers

    The H+/K+ ATPase (proton pump) is responsible for transporting which ions?

    <p>H+ into the gastric lumen and K+ into the cell</p> Signup and view all the answers

    What physiological process is known as the alkaline tide?

    <p>Efflux of bicarbonate into the bloodstream in exchange for Cl- ions</p> Signup and view all the answers

    What role do chloride ions play in HCl secretion?

    <p>Combine with H+ ions to form HCl</p> Signup and view all the answers

    What is the outcome when carbonic anhydrase facilitates the formation of carbonic acid in parietal cells?

    <p>Increase in H+ concentration</p> Signup and view all the answers

    What part of the brainstem controls the vomiting reflex?

    <p>Medulla oblongata</p> Signup and view all the answers

    What type of receptors does the chemoreceptor trigger zone (CTZ) primarily contain?

    <p>5HT3 (serotonin), D2 (dopamine), and histamine</p> Signup and view all the answers

    Which receptor type is most commonly targeted by antiemetic drugs for treating chemotherapy-induced nausea?

    <p>5HT3 (serotonin)</p> Signup and view all the answers

    Which sphincter relaxes to enable the expulsion of stomach contents during vomiting?

    <p>Lower esophageal sphincter (LOS)</p> Signup and view all the answers

    The vagus nerve is responsible for transmitting vomiting signals from which parts of the body?

    <p>The stomach and intestines to the brain</p> Signup and view all the answers

    What can trigger vomiting by engaging higher brain centers?

    <p>Sounds, odors, sights, or strong emotions</p> Signup and view all the answers

    Which inner ear structure is involved in detecting motion changes and can cause motion sickness?

    <p>Labyrinths</p> Signup and view all the answers

    Which action does NOT occur during the vomiting reflex?

    <p>Tightening the pyloric sphincter</p> Signup and view all the answers

    Which of these food types takes the longest to exit the stomach?

    <p>Fatty foods</p> Signup and view all the answers

    During the intestinal phase, what triggers the secretion of bicarbonate?

    <p>Chyme entering the duodenum</p> Signup and view all the answers

    What is the primary function of bile during digestion?

    <p>To emulsify fats for improved digestion</p> Signup and view all the answers

    Which small intestine section is primarily involved in nutrient absorption?

    <p>Jejunum</p> Signup and view all the answers

    What influence does the rate of stomach emptying have?

    <p>It impacts blood sugar levels and feelings of fullness.</p> Signup and view all the answers

    What initiates the start of the intestinal phase of digestion?

    <p>Chyme reaches the duodenum</p> Signup and view all the answers

    Which food type usually has an intermediate rate of digestion and stomach emptying?

    <p>Proteins</p> Signup and view all the answers

    Which organ plays a crucial role in neutralizing stomach acid during the intestinal phase?

    <p>Pancreas</p> Signup and view all the answers

    Which cells in the liver are responsible for producing bile?

    <p>Hepatocytes</p> Signup and view all the answers

    What is the main function of bile salts?

    <p>To emulsify fats and aid in their absorption</p> Signup and view all the answers

    Which hormone stimulates the release of bile upon the entry of fatty food into the duodenum?

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

    The common bile duct transports bile from the liver and gallbladder to which structure?

    <p>Duodenum</p> Signup and view all the answers

    Which pancreatic enzyme is responsible for breaking down carbohydrates?

    <p>Pancreatic amylase</p> Signup and view all the answers

    Pancreatic peptidases such as trypsin are secreted as inactive zymogens and are activated in which part of the digestive system?

    <p>Duodenum</p> Signup and view all the answers

    What role does bicarbonate secreted by the pancreas play in digestion?

    <p>It neutralizes stomach acid to create a suitable pH for enzyme function.</p> Signup and view all the answers

    Which component of bile is a byproduct of red blood cell breakdown?

    <p>Bilirubin</p> Signup and view all the answers

    What is the main reason for the presence of plicae circulares in the small intestine?

    <p>To increase the surface area and slow down chyme movement for better absorption</p> Signup and view all the answers

    Where are villi found in greatest abundance in the small intestine?

    <p>Duodenum and jejunum</p> Signup and view all the answers

    What is the specific role of microvilli in nutrient absorption?

    <p>To form the brush border, increasing surface area and aiding in digestion and absorption</p> Signup and view all the answers

    The combination of plicae circulares, villi, and microvilli primarily serves what function?

    <p>To increase the surface area for efficient nutrient absorption</p> Signup and view all the answers

    What major function do lacteals perform in the small intestine?

    <p>To absorb fats and transport them into the lymphatic system</p> Signup and view all the answers

    What primarily forms the brush border noted in the small intestine?

    <p>Microvilli on epithelial cells</p> Signup and view all the answers

    How do villi specifically contribute to the absorption of nutrients?

    <p>By increasing surface area and containing blood and lymphatic vessels for nutrient transport</p> Signup and view all the answers

    What is a primary characteristic of the small intestine's structural adaptations that support nutrient absorption?

    <p>The large internal surface area due to folds and projections</p> Signup and view all the answers

    Which enzyme is responsible for starting the breakdown of starch in the mouth?

    <p>Salivary amylase</p> Signup and view all the answers

    What is the primary enzyme that facilitates carbohydrate digestion within the small intestine?

    <p>Pancreatic amylase</p> Signup and view all the answers

    What is the end product when disaccharides are broken down by disaccharidases?

    <p>Monosaccharides</p> Signup and view all the answers

    Which transporter facilitates the absorption of glucose and galactose in enterocytes?

    <p>Sodium-Glucose Co-Transporter (SGLT-1)</p> Signup and view all the answers

    What mechanism is used for the absorption of fructose into enterocytes?

    <p>Facilitated diffusion using GLUT-5 transporter</p> Signup and view all the answers

    After absorption, how do monosaccharides leave enterocytes to enter the bloodstream?

    <p>GLUT-2 transporter</p> Signup and view all the answers

    What major vessel carries glucose to the liver post-absorption?

    <p>Portal vein</p> Signup and view all the answers

    In the liver, how is glucose primarily utilized?

    <p>Stored as glycogen or utilized for ATP production</p> Signup and view all the answers

    Which enzyme is primarily responsible for initiating protein digestion in the stomach?

    <p>Pepsin</p> Signup and view all the answers

    In what form is trypsin secreted by the pancreas?

    <p>Inactive form as trypsinogen</p> Signup and view all the answers

    Where does the activation of trypsinogen to trypsin occur?

    <p>Duodenum (small intestine)</p> Signup and view all the answers

    What is the role of peptidases located on the brush border of the small intestine?

    <p>To convert oligopeptides into amino acids</p> Signup and view all the answers

    What mechanism do enterocytes use to absorb amino acids?

    <p>Sodium-dependent co-transporters</p> Signup and view all the answers

    How do amino acids enter the bloodstream after being absorbed by the enterocytes?

    <p>Facilitated diffusion through the basolateral membrane</p> Signup and view all the answers

    What are the main functions of amino acids in the body once absorbed?

    <p>Protein synthesis and energy production</p> Signup and view all the answers

    What condition can impair protein digestion in the stomach?

    <p>Decreased production of pepsin due to hypochlorhydria</p> Signup and view all the answers

    What is the primary function of bile salts in the digestion of fats?

    <p>To emulsify fats into smaller droplets for easier digestion</p> Signup and view all the answers

    What products are formed when pancreatic lipase acts on emulsified fats?

    <p>Fatty acids and glycerol</p> Signup and view all the answers

    Which structure is responsible for transporting fatty acids and glycerol to the intestinal mucosa?

    <p>Micelles</p> Signup and view all the answers

    Inside enterocytes, fatty acids and monoglycerides are reassembled into which type of molecule?

    <p>Triglycerides</p> Signup and view all the answers

    Where are chylomicrons secreted for transport after fat absorption?

    <p>The lacteals (lymphatic vessels)</p> Signup and view all the answers

    What type of substances does the hydrophobic core of micelles contain?

    <p>Non-polar fatty acids and monoglycerides</p> Signup and view all the answers

    How do bile salts influence the structure of micelles?

    <p>They create a hydrophilic surface for interaction with the intestinal environment.</p> Signup and view all the answers

    What is the primary purpose of transporting chylomicrons through the lymphatic system after absorption?

    <p>Transporting and distributing dietary fats to body tissues</p> Signup and view all the answers

    What form must non-haem iron be converted to for better absorption?

    <p>Ferrous Fe²⁺</p> Signup and view all the answers

    Which vitamin is crucial for the conversion of non-haem iron from Fe³⁺ to Fe²⁺?

    <p>Vitamin C</p> Signup and view all the answers

    In which part of the small intestine does iron primarily get absorbed?

    <p>Duodenum</p> Signup and view all the answers

    Where is Vitamin B12 absorbed after binding to intrinsic factor?

    <p>Terminal ileum</p> Signup and view all the answers

    Which of the following foods is considered a rich source of Vitamin B12?

    <p>Meat, eggs, and milk</p> Signup and view all the answers

    Why is water reabsorption in the large intestine important?

    <p>It maintains body hydration and electrolyte balance.</p> Signup and view all the answers

    What primarily contributes to the formation of feces in the large intestine?

    <p>Undigested food and bacteria</p> Signup and view all the answers

    What is one of the essential functions of the bacterial flora in the large intestine?

    <p>They produce vitamins and aid in fermentation.</p> Signup and view all the answers

    Which part of the body initiates the defecation reflex?

    <p>The rectum via stretch receptors</p> Signup and view all the answers

    Which sphincter is automatically relaxed during defecation?

    <p>Internal anal sphincter</p> Signup and view all the answers

    How does an individual exert voluntary control over the defecation process?

    <p>By controlling the external anal sphincter</p> Signup and view all the answers

    What could be a consequence of impaired water reabsorption in the large intestine?

    <p>Increased fecal mass and diarrhea</p> Signup and view all the answers

    What role do bacteria play in the digestion process within the large intestine?

    <p>They synthesize certain fatty acids.</p> Signup and view all the answers

    Study Notes

    Upper Oesophageal Sphincter (UOS)

    • Prevents air from entering the oesophagus during breathing.
    • Stops backflow of food and liquids into the pharynx.

    Lower Oesophageal Sphincter (LOS)

    • Located at the gastro-oesophageal junction (GOJ).
    • Prevents gastric reflux.

    Diaphragm and LOS

    • Supports and maintains the tone of the LOS.

    Distance from Incisors to GOJ

    • 40 cm during upper endoscopy.

    Stomach Structure and Function

    • The fundus is the uppermost part of the stomach located next to the diaphragm. It stores undigested food and gases released during digestion.
    • The body of the stomach is responsible for mixing food with digestive juices, forming chyme.
    • The antrum is the lower part of the stomach that grinds food and regulates its passage to the small intestine.
    • The pyloric sphincter acts as a valve between the stomach and the duodenum. It regulates the flow of partially digested food into the duodenum and prevents backflow.

    Duodenum

    • The duodenum is the first part of the small intestine.
    • It's approximately 30 cm long.
    • It receives partially digested food (chyme) from the stomach and begins the digestion process.
    • The duodenal bulb marks the transition zone for chyme entering from the stomach.
    • The major duodenal papilla is the opening where bile and pancreatic enzymes enter the duodenum.
    • The ligament of Treitz separates the duodenum from the jejunum.

    Small Intestine Sections

    • The jejunum is primarily responsible for nutrient absorption.
    • The ileum is responsible for absorbing vitamin B12 and bile salts.
    • The ileocecal valve prevents the backflow of content from the large intestine into the small intestine.
    • The duodenum is where the mixing of chyme with digestive juices primarily occurs.
    • The jejunum has a highly folded surface with many villi to increase surface area for nutrient absorption.

    Liver Location

    • The liver is primarily located in the right upper quadrant of the abdomen.

    Liver Functions

    • Bile Production: The liver produces bile, which is essential for digesting and absorbing fats in the small intestine.
    • Blood Filtration: Kupffer cells in the liver filter blood and break down bacteria and foreign particles.
    • Vitamin Storage: The liver stores vitamins A, D, E, K, and B12.
    • Blood Clotting: The liver produces proteins necessary for blood clotting.
    • Nutrient Metabolism: The liver converts glycogen to glucose (gluconeogenesis) and vice versa (glycogenesis). This process helps regulate blood sugar levels.

    Pancreas Structure and Function

    • Pancreas - Located within the abdomen behind the stomach and plays a role in both digestion and blood sugar regulation.
    • Exocrine function: Produces digestive enzymes released into the duodenum.
    • Endocrine function: Produces hormones that regulate blood sugar levels.
    • Acinar cells: The exocrine cells of the pancreas responsible for producing digestive enzymes like amylase, lipase, and proteases secreted through the pancreatic duct into the duodenum.
    • Islets of Langerhans: Found within the pancreas containing the endocrine cells (alpha and beta cells).
    • Alpha cells: Secrete glucagon, a hormone responsible for increasing blood glucose levels.
    • Beta cells: Secrete insulin, a hormone that lowers blood glucose levels by facilitating glucose uptake by body cells.
    • Pancreatic duct: Transports pancreatic enzymes through the pancreas and joins with the common bile duct to release its contents into the duodenum.
    • Common bile duct: Carries bile from the gallbladder to the duodenum for fat digestion.

    Common Bile Duct (CBD)

    • Carries bile from the liver and gallbladder to the duodenum where it aids digestion.

    Cystic Duct

    • Connects the gallbladder to the common bile duct.

    Ampulla of Vater

    • Shared opening or junction for the common bile duct and the pancreatic duct.
    • This is where the combined secretions enter the duodenum.

    Sphincter of Oddi

    • A muscle that regulates the flow of bile and pancreatic enzymes into the duodenum.
    • Prevents backflow of intestinal contents into the pancreatic and bile ducts.

    Head of the Pancreas

    • Situated in the curve of the duodenum.

    Gallbladder

    • Serves as a storage and concentrating unit for bile.
    • Bile is produced in the liver.

    The Colon and its Parts

    • The caecum connects the small intestine to the colon and absorbs fluids and salts.
    • The hepatic flexure is the bend between the ascending and transverse colon.
    • The appendix is attached to the caecum.
    • The transverse colon continues the absorption and fermentation process.
    • The sigmoid colon connects to the rectum.
    • The splenic flexure is located between the transverse colon and descending colon.
    • The rectum stores and expels feces during defecation.
    • The anus is the final part of the digestive system.

    Layers of the GI Tract

    • The mucosa is the innermost layer of the GI tract and is responsible for absorption and secretion.

    • The mucosa is made up of:

    • Epithelium: The lining that comes into contact with food.

    • Lamina propria: Connective tissue that supports the epithelium and contains blood vessels, lymph vessels, and nerves.

    • Muscularis mucosae: A thin layer of muscle that creates slight movements, helping dislodge food particles and enhance absorption.

    • The submucosa is a layer of connective tissue that lies beneath the mucosa.

    • The submucosa contains:

    • Blood vessels and lymphatics that supply the GI tract.

    • The submucosal plexus (Meissner's plexus): A network of nerves that controls the secretions of the GI tract.

    • The muscularis is a layer of muscle that lies beneath the submucosa.

    • The muscularis contains:

    • Circular muscle: Contracts behind a food bolus to push it forward.

    • Longitudinal muscle: Contracts along the length of the GI tract, aiding in peristalsis.

    • Myenteric plexus (Auerbach's plexus): A network of nerves that controls GI motility.

    • The serosa is the outermost layer of the GI tract.

    • This layer of connective tissue and epithelium protects the GI tract and reduces friction with other organs.

    • The serosa is also responsible for secreting lubricating fluid.

    Mesentery: Structure and Function

    • The mesentery is a double layer of peritoneum that connects the intestines to the posterior abdominal wall.
    • It plays a vital role in supporting and anchoring the intestines.
    • The mesentery acts as a pathway for crucial structures:
      • Blood Vessels: Oxygenated blood is delivered to the intestines, and nutrient-rich blood is transported to the liver through vessels within the mesentery.
      • Lymphatic Vessels: Absorb and transport fats, contributing to the immune system's functions.
      • Nerves: Facilitate communication between the intestines and the nervous system, enabling proper digestive processes.
    • The mesentery is NOT involved in producing digestive enzymes. That function is performed by the pancreas and other digestive glands.

    Arterial Supply to Abdominal Organs

    • Coeliac artery (Celiac trunk) supplies blood to the stomach, spleen, and liver
    • Superior mesenteric artery (SMA) supplies blood to most of the small intestine (jejunum and ileum) and part of the large intestine (cecum, ascending colon, transverse colon)
    • Inferior mesenteric artery (IMA) supplies blood to the descending colon, sigmoid colon, and rectum
    • Hepatic artery primarily supplies the liver
    • Splenic artery is a branch of the coeliac artery and supplies blood to the spleen
    • Pancreaticoduodenal arteries supply blood to the duodenum and pancreas
    • Appendicular artery is a branch of the superior mesenteric artery that supplies blood to the appendix
    • Jejunal and ileal arteries are branches of the superior mesenteric artery that supply blood to the jejunum and ileum, respectively

    Veins Draining to the Inferior Vena Cava (IVC)

    • Renal Veins: Directly drain blood from the kidneys into the IVC
    • Right Gonadal Vein: Drains directly into the IVC
    • Left Gonadal Vein: Typically drains into the left renal vein before reaching the IVC
    • Hepatic Vein: Responsible for returning blood from the liver to the IVC
    • Common Iliac Veins: Formed by the union of internal and external iliac veins
    • Phrenic Vein: Drains blood from the diaphragm and contributes to the IVC
    • Left Adrenal (Suprarenal) Vein: Typically empties into the left renal vein
    • Inferior Vena Cava (IVC): Main function is to drain deoxygenated blood from the lower body and return it to the heart

    Hepatic Portal Vein

    • Carries nutrient-rich blood from digestive organs to the liver for processing.
    • Formed by the superior mesenteric vein and splenic vein.
    • The inferior mesenteric vein joins the splenic vein before entering the hepatic portal vein.

    Superior Mesenteric Vein

    • Drains blood from the small intestine, cecum, and ascending colon.

    Splenic Vein

    • Drains blood from the spleen, parts of the stomach, and pancreas.

    Inferior Mesenteric Vein

    • Drains blood from the descending colon, sigmoid colon, and rectum.

    Hepatic Vein

    • Does NOT contribute to the formation of the hepatic portal vein.
    • Carries deoxygenated blood from the liver to the heart.

    Hepatic Circulation

    • Hepatic portal vein: Supplies 70% of the liver's blood.
    • Hepatic portal vein: Carries nutrient-rich blood from the gastrointestinal tract and spleen to the liver for processing.
    • Hepatic portal vein: Provides 50% of the liver's oxygen requirement.
    • Hepatic artery: Supplies 30% of the liver's blood.
    • Hepatic artery: Carries oxygen-rich blood to the liver.
    • Hepatic vein: Drains deoxygenated blood from the liver into the Inferior Vena Cava (IVC).
    • Hepatic vein: Connects the liver to the Inferior Vena Cava (IVC).

    Hepatic Circulation: Blood Flow in the Liver

    • Hepatic Portal Vein and Hepatic Artery are the two main blood vessels supplying the liver.
    • Hepatic portal vein: carries nutrient-rich, oxygen-poor blood from the digestive tract.
    • Hepatic artery: carries oxygen-rich blood from the heart.
    • Hepatic sinusoids: specialized capillaries within the liver where blood from the portal vein and hepatic artery mix.
    • Hepatic sinusoids act as mixing chambers for blood, enabling metabolic functions.
    • Blood then collects in hepatic venules, which channel it towards larger hepatic veins.
    • Hepatic veins drain blood into the Inferior Vena Cava (IVC), returning it to the heart.
    • The liver's crucial role: processing and detoxifying substances absorbed from the digestive tract.
    • The liver's unique dual blood supply allows it to efficiently perform its diverse metabolic functions.

    Liver Functions: Key Roles and Components

    • Liver's Role in Detoxification: The liver is a crucial filter for toxins, neutralizing them before they can circulate within the body.
    • Liver's Role in Drug Metabolism: The liver plays a vital role in breaking down medicines into usable or inactive forms, ensuring safe processing and elimination.
    • Kupffer Cells: These specialized cells in the liver are responsible for clearing harmful substances like microorganisms, debris, and dead cells from the bloodstream.
    • Hepatic Sinusoids: These intricate blood channels allow for direct interaction between blood and hepatocytes, facilitating detoxification and metabolism processes.
    • Storing Glucose: The liver stores glucose as glycogen, regulating blood sugar levels.
    • Lack of Digestive Enzyme Production: Unlike some other digestive organs, the liver does not produce digestive enzymes.
    • Blood Flow and Central Veins: Once cleansed and processed within the liver, blood flows into the central vein and exits through the hepatic vein.

    Portal Hypertension

    • Portal hypertension is a condition where there is increased pressure in the portal vein system.
    • This increase in pressure is usually caused by resistance in the liver, hindering blood flow.
    • Cirrhosis is the most common cause of portal hypertension.
    • Portal hypertension leads to the development of esophageal and rectal varices.
    • Varices are swollen and fragile veins that can rupture due to increased pressure, leading to life-threatening bleeding.
    • Ascites is the accumulation of fluid in the abdominal cavity, a common complication of portal hypertension.
    • This occurs due to high pressure in the portal vein system and low albumin levels in the blood.
    • Portal vein thrombosis can occur when a blood clot forms inside the portal vein.
    • Portal hypertension is a serious complication associated with advanced liver disease, potentially leading to fatal complications.

    Lymph and the Lymphatic System

    • Lymph is a fluid that circulates throughout the body.
    • Primary Function of Lymph: Collects and transports excess interstitial fluid (fluid between cells) from tissues back to the bloodstream.
    • Lymphocytes are the predominant cell type found in lymph, vital for immune responses.
    • Lymph Nodes are structures that filter harmful substances (pathogens) from lymph and house immune cells.
    • Thoracic Duct: The main lymphatic vessel that empties lymph into the left subclavian vein, carrying it back into the circulatory system.
    • Right Lymphatic Duct: Drains lymph from the right upper part of the body into the right subclavian vein.
    • Lacteals: Lymphatic capillaries in the small intestine that absorb fats and proteins, contributing to fat transport.
    • Fluid Homeostasis: The lymphatic system contributes to maintaining fluid balance by absorbing excess tissue fluid and returning it to the bloodstream.
    • Lymph Nodes play a crucial role in the immune system by filtering lymph and identifying/responding to pathogens.

    Lymphatic Drainage and Main Ducts

    • The lymphatic system plays a crucial role in fluid balance by collecting excess interstitial fluid and returning it to the bloodstream.

    • Two primary lymphatic ducts, the right lymphatic duct and the thoracic duct, drain lymph from different areas of the body.

    • The right lymphatic duct drains the right upper quadrant of the body, including the right side of the head, neck, arm, and thorax. It empties into the right subclavian vein.

    • The thoracic duct, the larger of the two, drains lymph from the left upper quadrant and both lower quadrants of the body. It originates in the abdomen as a dilated sac called the cisterna chyli and empties into the left subclavian vein.

    • Understanding lymphatic drainage is essential for diagnosing and treating conditions such as lymphedema, a swelling caused by lymphatic fluid buildup, and cancer metastasis, the spread of cancer cells through the lymphatic system.

    Enteric Nervous System (ENS)

    • Often referred to as the "gut brain"
    • Responsible for controlling the digestive system
    • Has sensory neurons, motor neurons, and interneurons
    • Sensory neurons detect changes within the gut environment like pH levels and stretching
    • Motor neurons control contractions of smooth muscle and secretion of digestive fluids
    • Plays a role in regulating blood flow to the GI tract

    Sympathetic Nervous System (SNS)

    • Part of the autonomic nervous system
    • Impacts the digestive system
    • Decreases GI motility and secretion, increasing sphincter tone
    • This is a "fight or flight" response that prioritises other bodily functions

    Parasympathetic Nervous System (PNS)

    • Part of the autonomic nervous system
    • Promotes digestion by increasing GI motility and secretion
    • This response supports "rest and digest" functions

    Vagus Nerve

    • The primary nerve involved in parasympathetic stimulation of the GI system
    • Controls muscles and glands in the gut, along with the sensation of hunger and satiety

    Voluntary Nerves

    • Control the external anal sphincter and mastication
    • Enable conscious control of swallowing and chewing

    Communication

    • The ENS operates autonomously but communicates with the CNS
    • This is to ensure an integrated response to stimuli, ensuring proper functioning of the body as a whole

    Enteric Hormones

    • Function: Control gastric secretion and motility.
    • Act as messengers in the gastrointestinal tract.

    Cholecystokinin (CCK)

    • Function: Stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder.

    Amylase

    • Function: Breaks down complex carbohydrates into smaller sugars.

    Peptidases

    • Function: Break down proteins into peptides and amino acids.

    Lipase

    • Function: Breaks down fats into fatty acids and glycerol.

    Bile Acids

    • Function: Aids in the emulsification of fats for easier digestion.

    Intrinsic Factor

    • Function: Essential for vitamin B12 absorption in the small intestine.

    Oligosaccharidases

    • Function: Further breakdown of smaller carbohydrates into simpler sugars for absorption.

    The Mouth in Digestion

    • Mastication, chewing, breaks food into smaller pieces, increasing surface area for enzyme action.
    • Saliva, produced by salivary glands, is essential for initial food digestion.
    • Salivary amylase, an enzyme in saliva, begins the breakdown of complex carbohydrates (starches) into simpler sugars.
    • Three major salivary glands:
      • Parotid gland: Produces serous fluid, released through Parotid/Stensen's duct.
      • Submandibular gland: Produces both serous fluid and mucus, contributing most to mucus production.
      • Sublingual gland: Produces mostly mucus.
    • Saliva's composition:
      • Serous fluid: Lubricates food, provides medium for enzymes.
      • Mucus: Binds food particles, forming a bolus for easy swallowing.
    • Bolus: A soft, moist mass of food formed by mixing food with saliva, ready for swallowing.

    Oropharyngeal Phase of Swallowing

    • The oropharyngeal phase of swallowing is the second stage of the swallowing process, following the oral phase.
    • The oropharyngeal phase begins voluntarily but quickly transitions to an involuntary reflex.
    • This phase involves the coordinated movement of the tongue, epiglottis, pharyngeal wall, and valleculae to propel the food bolus into the esophagus.
    • The tongue pushes the bolus backward against the palate and into the pharynx.
    • The valleculae are small spaces at the base of the tongue that help organize the food bolus and direct it towards the pharynx.
    • The epiglottis folds over the trachea preventing food from entering the trachea.
    • The pharyngeal wall contracts and moves forward, propelling the bolus into the esophagus.
    • The oropharyngeal phase does not include peristaltic movement, as that occurs in the esophageal phase.

    Oesophageal Phase of Swallowing

    • Upper oesophageal sphincter (UOS) relaxes to allow the food bolus to pass from the pharynx into the oesophagus
    • Peristaltic muscle contractions move the food bolus through the oesophagus
    • Lower oesophageal sphincter (LOS) opens to allow the bolus into the stomach and then closes to prevent acid reflux
    • The oesophageal phase is under involuntary control by the autonomic nervous system
    • The UOS closes after the bolus passes to prevent backflow of food into the throat
    • Gravity assists in the movement of the bolus through the oesophagus, especially when upright
    • If the LOS does not close properly after food enters the stomach, it can lead to acid reflux or gastroesophageal reflux disease (GERD)

    Stomach Functions in Digestion

    • Gastric Juice: Highly acidic with a pH range of 1.5 to 3.5, essential for chemical digestion in the stomach.
    • Pepsin: A key enzyme in gastric juice that breaks down proteins.
    • Gastrin: A regulatory molecule produced by the stomach that stimulates acid production.
    • Chyme: A semi-liquid mixture of food and gastric juice formed through the stomach's mechanical action of mixing.
    • Pylorus: The opening between the stomach and the small intestine. The stomach pushes chyme towards the pylorus to propel it into the duodenum, the first part of the small intestine, for further digestion.
    • Stomach Absorption: The stomach primarily absorbs alcohol and lipid-soluble drugs.
    • Gastric Juice Function: Key role in chemical breakdown of food, particularly proteins, using digestive enzymes like pepsin and the acidic environment.
    • Mechanical Mixing and Propulsion: Essential for combining food with gastric juice, promoting efficient digestion within the stomach.

    Enteroendocrine Cells and Digestive Hormones

    • Enteroendocrine cells are specialized cells found in the lining of the gastrointestinal tract.
    • They release hormones that regulate various aspects of digestion.
    • These hormones act on other cells in the digestive system, influencing processes like acid production, enzyme secretion, and nutrient absorption.

    Gastrin

    • Gastrin is released by G cells in the stomach.
    • It stimulates the production of gastric juice by increasing hydrochloric acid (HCl) secretion from parietal cells.
    • This acidic environment is crucial for optimal digestion in the stomach.

    Histamine

    • Histamine, also released in the stomach, directly promotes HCl secretion by binding to receptors on parietal cells.
    • It plays a vital role in maintaining the acidic pH necessary for digestive enzymes to function effectively in the stomach.

    Ghrelin

    • Ghrelin, often referred to as the "hunger hormone," is produced in the stomach and released before meals.
    • It signals the brain's hypothalamus to stimulate appetite and promote food intake.
    • Ghrelin levels typically increase before meals and decrease after eating.

    Cholecystokinin (CCK)

    • Cholecystokinin (CCK) is released from enteroendocrine cells in the small intestine.
    • It stimulates the gallbladder to release bile, which aids in fat digestion.
    • CCK also slows down gastric emptying, allowing for better nutrient absorption in the small intestine.

    Chief Cells and Pepsinogen

    • Chief cells are located in the gastric glands of the stomach lining.
    • They secrete pepsinogen, an inactive precursor of the enzyme pepsin.
    • Pepsinogen is activated into pepsin in the presence of hydrochloric acid (HCl).
    • HCl is secreted by parietal cells, located in the stomach lining.
    • Pepsin is a digestive enzyme that breaks down proteins into smaller peptides.
    • Pepsinogen is secreted in an inactive form to prevent the digestion of the stomach's own cells.
    • The conversion of pepsinogen to pepsin is an example of zymogen activation.
    • Pepsin further digests proteins in the stomach, before they are passed to the small intestine for further digestion and absorption.

    Parietal Cells

    • Parietal cells are specialized cells located in the stomach lining
    • Their primary function is to secrete hydrochloric acid (HCl) and intrinsic factor

    Hydrochloric Acid (HCl)

    • HCl is a strong acid that plays a crucial role in digestion
    • It activates pepsinogen into pepsin, a digestive enzyme that breaks down proteins
    • It denatures proteins, making them easier to digest
    • It creates an acidic environment that kills ingested bacteria and other pathogens

    Intrinsic Factor

    • Intrinsic factor is a glycoprotein essential for the absorption of vitamin B12 in the ileum
    • Vitamin B12 is vital for the production of red blood cells
    • A deficiency in intrinsic factor leads to pernicious anemia, a condition characterized by a lack of red blood cells

    Proton Pump (H+/K+ ATPase)

    • The secretion of hydrogen ions (H+) by parietal cells is facilitated by a proton pump
    • This pump uses energy from ATP to move H+ ions from the parietal cells into the stomach lumen

    Regulation of Parietal Cell Function

    • The secretion of HCl and intrinsic factor is regulated by various factors, including:
      • Gastrin: A hormone released by the stomach that stimulates acid production
      • Acetylcholine: A neurotransmitter released by the vagus nerve that also stimulates acid production
      • Histamine: A paracrine factor released by other stomach cells that enhances the response of parietal cells to gastrin and acetylcholine

    Disorders of Parietal Cells

    • Disorders affecting parietal cells can lead to various digestive problems, including:
      • Achlorhydria: A condition where the stomach produces very little or no HCl
      • Pernicious anemia: A condition caused by a deficiency in intrinsic factor, leading to vitamin B12 malabsorption

    Parietal Cell HCl Secretion

    • Histamine, gastrin, and acetylcholine (ACh) stimulate HCl secretion from parietal cells
    • Histamine binds to the H2 receptor on parietal cells, promoting HCl secretion
    • Gastrin binds to its receptor on parietal cells, promoting HCl secretion by stimulating the proton pump
    • Acetylcholine (ACh) released from the vagus nerve binds to receptors on parietal cells, enhancing acid secretion
    • Carbonic anhydrase catalyzes the formation of carbonic acid (H2CO3) from CO2 and H2O in parietal cells
    • Carbonic acid (H2CO3) dissociates into H+ and bicarbonate (HCO3-) ions
    • The H+/K+ ATPase (proton pump) actively pumps H+ ions into the gastric lumen and K+ ions into the cell
    • Bicarbonate (HCO3-) ions move into the bloodstream in exchange for Cl- ions, resulting in the alkaline tide (temporary increase in blood pH)
    • Cl- ions combine with H+ ions in the gastric lumen to form HCl
    • HCl in the stomach activates pepsinogen into pepsin and kills ingested bacteria

    Vomiting Reflex and Triggers

    • The medulla oblongata, located in the brainstem, controls the vomiting reflex.
    • The chemoreceptor trigger zone (CTZ), located in the medulla oblongata, detects signals from the blood and plays a crucial role in triggering vomiting.
    • The CTZ contains 5HT3 (serotonin), D2 (dopamine), and histamine receptors. These receptors are targeted by antiemetic drugs to reduce vomiting.
    • 5HT3 (serotonin) receptor antagonists are commonly used to prevent chemotherapy-induced nausea.
    • During vomiting, the lower esophageal sphincter (LOS) relaxes, allowing the expulsion of stomach contents.
    • The vagus nerve transmits signals related to vomiting from the stomach and intestines to the brain.
    • Vomiting can be triggered by higher brain centers, such as the sight, smell, or thought of something unpleasant.
    • The labyrinths in the inner ear are responsible for detecting changes in motion, which can lead to motion sickness.
    • During the vomiting reflex, the nasal cavity and glottis close, the diaphragm and abdominal wall muscles contract, and the lower esophageal sphincter relaxes. The pyloric sphincter does not tighten.

    Stomach Emptying Rate

    • Carbohydrates leave the stomach fastest
    • Fatty foods take the longest to leave the stomach (3-6 hours).
    • Proteins have an intermediate emptying rate

    Intestinal Phase

    • Begins when chyme enters the duodenum from the stomach.
    • The duodenum coordinates digestive enzyme secretion and nutrient absorption.
    • Pancreas secretes bicarbonate to neutralize stomach acid
    • Bile is secreted by the liver and stored by the gallbladder, and it emulsifies fats for better digestion.

    Stomach Emptying and its Impact

    • The rate at which food leaves the stomach impacts blood sugar levels and satiety.

    Liver, Bile, and Pancreatic Enzymes in Digestion

    • Hepatocytes, cells within the liver, are responsible for producing bile.
    • Bile is a fluid that is stored and concentrated in the gallbladder.
    • Bile salts play a crucial role in emulsifying fats, breaking them down into smaller droplets, which increases their surface area for digestion by enzymes.
    • The presence of fatty food in the duodenum triggers the release of **Cholecystokinin (CCK) **, a hormone that stimulates the gallbladder to release stored bile into the duodenum.
    • The common bile duct (CBD) serves as a conduit for bile transportation from the liver and gallbladder to the duodenum.
    • Pancreatic enzymes play a key role in digestion and are secreted by the pancreas.
    • Pancreatic amylase is responsible for breaking down carbohydrates.
    • Pancreatic peptidases like trypsin are secreted in their inactive form as zymogens. They are activated in the duodenum by enterokinase, an enzyme secreted by the intestinal lining.
    • Bicarbonate is a crucial component of pancreatic secretions, helping to neutralize stomach acid, creating the optimal pH environment for the function of digestive enzymes.
    • Bilirubin, a component of bile, is a byproduct of red blood cell breakdown. It is produced in the spleen and is transported to the liver for elimination.

    Small Intestine Adaptations for Nutrient Absorption

    • Plicae Circulares: Circular folds in small intestine lining, increasing surface area and slowing down chyme movement for optimal absorption.
    • Villi: Finger-like projections extending from the intestinal lining, increasing surface area further and containing blood and lymphatic vessels for nutrient transport.
    • Microvilli: Tiny projections on epithelial cells lining the villi, forming the "brush border" and aiding in digestion and absorption.
    • Lacteals: Lymphatic vessels within each villus, responsible for absorbing fats (lipids) and transporting them into the lymphatic system.
    • Brush Border: Formed by microvilli, responsible for increasing surface area and facilitating digestion and absorption.
    • Duodenum and Jejunum: Contain the most villi, showcasing their importance in nutrient absorption.
    • Submucosa: The layer beneath the mucosa, not directly involved in increasing surface area for absorption.

    Carbohydrate Digestion and Absorption

    • Salivary amylase: Begins starch and glycogen breakdown in the mouth.
    • Pancreatic amylase: Continues carbohydrate digestion in the small intestine.
    • Disaccharidases (e.g., sucrase, lactase, maltase): Located on the brush border of the small intestine, break down disaccharides into monosaccharides.
    • Glucose and galactose: Absorbed into enterocytes via sodium-glucose co-transporter (SGLT-1), an active transport process.
    • Fructose: Absorbed into enterocytes via facilitated diffusion using GLUT-5 transporter.
    • Exit from enterocytes: Monosaccharides leave enterocytes and enter capillaries using GLUT-2 transporter.
    • Glucose transport to the liver: Primarily transported to the liver via the portal vein.
    • Liver function with glucose: Stores glucose as glycogen and uses it for ATP production.

    Protein Digestion

    • Pepsin is the main enzyme responsible for protein digestion in the stomach.
    • Pepsin is secreted as an inactive precursor called pepsinogen, which is activated by hydrochloric acid (HCl) in the stomach.
    • The pancreas secretes trypsinogen, an inactive form of the trypsin enzyme.
    • Trypsinogen is activated to trypsin in the duodenum (small intestine) by the enzyme enteropeptidase.
    • Trypsin further breaks down proteins into smaller peptides.
    • Peptidases, located on the brush border of the small intestine, further break down oligopeptides into individual amino acids.
    • Amino acids are then absorbed into the enterocytes (cells lining the small intestine).
    • Amino acid absorption primarily occurs via sodium-dependent co-transporters, which require energy.
    • Amino acids leave the enterocytes and enter the bloodstream via facilitated diffusion through the basolateral membrane.

    Amino Acid Functions

    • Amino acids are used for protein synthesis, building and repairing tissues.
    • They also contribute to energy production and are crucial for various other cellular functions.

    Protein Digestion Disorders

    • Hypochlorhydria (reduced stomach acid production) can impair protein digestion due to decreased pepsin activation.
    • Conditions affecting the pancreas (e.g., pancreatitis) can reduce trypsinogen secretion, leading to impaired protein digestion in the small intestine.

    Fat Digestion and Absorption

    • Bile salts are produced in the liver and stored in the gallbladder. They emulsify fats, breaking them down into smaller droplets, increasing the surface area for digestion by enzymes.
    • Lipase is an enzyme produced by the pancreas. It breaks down emulsified fats into fatty acids and glycerol.
    • Micelles are tiny spheres formed in the small intestine. They have a hydrophilic (water-loving) outer layer composed of bile salts and a hydrophobic (water-fearing) core holding fatty acids and monoglycerides. Micelles transport these products to the intestinal mucosa for absorption.
    • Enterocytes are cells lining the small intestine. They absorb fatty acids and monoglycerides, reassembling them into triglycerides.
    • Chylomicrons are lipoprotein particles formed inside enterocytes. They transport triglycerides and other lipids from the intestines to the rest of the body through the lymphatic system.
    • Chylomicrons enter the bloodstream via the lymphatic vessels and distribute dietary fat to tissues for energy storage and other functions.

    Iron Absorption

    • Haem iron, derived from animal sources like meat, fish, and poultry, is readily absorbed.
    • Non-haem iron, found in plant-based foods, needs to be converted from Fe³⁺ to Ferrous Fe²⁺ for better absorption.
    • Vitamin C plays a crucial role in promoting this conversion.
    • Iron is predominantly absorbed in the duodenum.

    Vitamin Absorption

    • Folic acid is primarily absorbed in the jejunum.
    • Vitamin B12 requires intrinsic factor for absorption, which takes place in the terminal ileum.
    • Fat-soluble vitamins (A, D, E, K) are absorbed with the help of bile acid secretion.
    • Vitamin B12 is a key nutrient found in meat, eggs, and milk.

    Water Reabsorption

    • The large intestine is responsible for reabsorbing water, which is crucial for maintaining electrolyte balance and overall body hydration.

    Composition of Feces

    • Feces, the waste product eliminated from the body, is primarily composed of undigested food and bacteria.

    Role of Bacteria in the Large Intestine

    • The large intestine harbors a diverse population of bacteria, known as gut flora.
    • These bacteria have a vital role in producing essential vitamins and aiding in the fermentation of undigested food.

    Defecation Process

    • The defecation reflex, the process of eliminating waste, is initiated when stretch receptors within the rectum detect the presence of feces.

    Sphincter Control During Defecation

    • The internal anal sphincter, a muscle controlling the anus, automatically relaxes when the defecation reflex is triggered.
    • This relaxation allows for the passage of feces.

    Voluntary Control

    • Individuals can exert voluntary control over defecation by consciously controlling the external anal sphincter, a muscle that surrounds the internal anal sphincter.
    • This control allows for the timing of defecation.

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    Test your knowledge on the anatomy and function of the upper and lower oesophageal sphincters. This quiz covers their roles in breathing, preventing reflux, and their anatomical measurements. Perfect for students of human anatomy and physiology!

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