Gastrointestinal System Functions and Regulation
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Questions and Answers

Which nutrient is absorbed via a Na+-independent process in the small intestine?

  • Sucrose
  • Fructose (correct)
  • Galactose
  • Glucose

What is the primary function of mucosal protectants?

  • To increase gastric emptying time
  • To support the mucus layer protecting the gastric mucosa (correct)
  • To stimulate gastric acid production
  • To enhance the absorption of nutrients in the intestines

What is a consequence of vagotomy affecting the small intestine?

  • Delayed gastric emptying (correct)
  • Decreased absorption of vitamins
  • Improved pancreatic exocrine secretions
  • Increased gastric acid secretion

What is the mechanism of action for sucralfate?

<p>It polymerizes at pH &lt; 4 to form a sticky layer on ulcers (C)</p> Signup and view all the answers

What is the primary effect of duodenal reflux in patients with a gastric remnant?

<p>Higher risk of developing gastric cancer (C)</p> Signup and view all the answers

Which type of antacid is likely to form a sticky protective barrier in the stomach?

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

Which element is NOT mentioned as part of the absorption in the small intestine?

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

What can stimulate the vomiting reflex?

<p>Excessive distension of the stomach or duodenum (B)</p> Signup and view all the answers

Which transport mechanism is involved in the absorption of glucose and galactose in the small intestine?

<p>Active transport via Na+/K+ ATPase (A)</p> Signup and view all the answers

What role does misoprostol play in gastric protection?

<p>It prevents ulcer formation by increasing mucosal blood flow (D)</p> Signup and view all the answers

Why have surgical treatments for peptic ulcers become less common?

<p>The advent of proton pump inhibitors (PPIs) (A)</p> Signup and view all the answers

What neurotransmitters are involved in the vomiting reflex as mediated by the vomiting center in the medulla?

<p>Motor impulses along cranial nerves and intercostals (C)</p> Signup and view all the answers

Which of the following is NOT a cause of vomiting?

<p>Increased gastric motility (A)</p> Signup and view all the answers

What is a physiological effect of terminal ileal resection regarding bile salt absorption?

<p>Loss of bile salt reabsorption (C)</p> Signup and view all the answers

Which enzyme is responsible for activating lipolytic enzymes?

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

What condition can result from vitamin B12 deficiency due to terminal ileal resection?

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

Which enzyme cleaves triglycerides into free fatty acids and glycerol?

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

What is commonly associated with loss of enterohepatic circulation after terminal ileal resection?

<p>Increased risk of cholesterol gallstones (D)</p> Signup and view all the answers

How does trypsin affect proteolytic enzymes?

<p>Activates them from their inactive forms (C)</p> Signup and view all the answers

The presence of which enzyme indicates starch digestion in the small intestine?

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

What consequence does impaired fat emulsification lead to?

<p>Increased risk of nutrient deficiencies (B)</p> Signup and view all the answers

What is the primary function of glycogenolysis in the liver?

<p>To convert glycogen back to glucose during high energy demand (B)</p> Signup and view all the answers

Which substance is produced from the degradation of amino acids by the liver?

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

In which stage does the liver perform the first hydroxylation in vitamin D activation?

<p>Hydroxylating cholecalciferol to form 25-hydroxycholecalciferol (C)</p> Signup and view all the answers

What is the main role of the liver in lipid metabolism?

<p>Converting glucose to fatty acids for storage (C)</p> Signup and view all the answers

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

<p>Production of ammonia (D)</p> Signup and view all the answers

What happens to ammonia produced during amino acid metabolism in the liver?

<p>It is converted into urea (B)</p> Signup and view all the answers

Which hormone is NOT detoxified by the liver?

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

Which product is formed after the second stage of detoxification in the liver?

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

What is the primary function of the small bowel?

<p>Absorption of nutrients (A)</p> Signup and view all the answers

Which of the following fluid volumes is absorbed by the small bowel?

<p>8-9 L (C)</p> Signup and view all the answers

Which component is primarily secreted by the gallbladder?

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

During fat absorption, which of the following is NOT a direct product of lipid digestion?

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

Which process is primarily used to transport lipids across the intestinal membrane?

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

What is secreted by the pancreas into the gastrointestinal tract?

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

What component of the small bowel primarily facilitates the absorption of fats?

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

What type of compounds does the stomach absorb mainly?

<p>Fat-soluble compounds (A)</p> Signup and view all the answers

What substance is bilirubin conjugated to in hepatocytes to become water-soluble?

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

What is a consequence of pancreatectomy regarding malnutrition?

<p>Inadequate breakdown of protein and lipids (D)</p> Signup and view all the answers

Which hormones promote the release of bile according to their stimuli?

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

What is the primary physiological effect of the loss of pancreatic function?

<p>Fatty stools due to inadequate fat digestion (A)</p> Signup and view all the answers

What is the process by which the majority of bile acids are recycled back to the liver?

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

What pigment is responsible for giving feces their brown color?

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

Which component is NOT associated with the excretion of bile?

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

What happens to a portion of urobilinogen in the intestine?

<p>Some is reabsorbed and some is excreted. (C)</p> Signup and view all the answers

Secretin from the duodenal mucosa is released in response to ______ in the duodenum.

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

Tight epithelial junctions prevent acid from reaching deeper ______ in the gastric mucosa.

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

Fatty food in the duodenum leads to the release of ______ and GIP.

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

Prostaglandin E secretion has a protective role by increasing the thickness of the ______ layer in the stomach.

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

Intrinsic factor (IF) binds to vitamin ______ for absorption in the ileum.

<p>B12</p> Signup and view all the answers

The main functions of the stomach are storage, mixing, and ______ of food into the intestine.

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

The stomach has a resting volume of around ______ mL.

<p>50</p> Signup and view all the answers

As the stomach is distended, parasympathetic input from the vagus nerve inhibits muscle ______.

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

Iron is absorbed in the duodenum and jejunum in the ______ form.

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

Absorption of amino acids is facilitated by a ______ cotransport system.

<p>Na+</p> Signup and view all the answers

Fluids secreted into the GI tract amount to approximately ______ L daily.

<p>8–9</p> Signup and view all the answers

A majority of amino acids are absorbed in the ______ small intestine.

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

The three types of movement in the small bowel are segmentation, peristalsis, and ______.

<p>migrating motility complex</p> Signup and view all the answers

Calcium absorption is dependent on a ______-binding protein in intestinal cells.

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

Gastric acid is responsible for converting iron to the ______ form.

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

A small amount of fluid, only ______ to 200 mL, is excreted in the faeces each day.

<p>100</p> Signup and view all the answers

Saliva is secreted by several glands, including the parotid, submandibular, and ______ glands.

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

The ______ phase is characterized by involuntary actions that prevent food from entering the nasopharynx.

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

Salivary amylase initiates the digestion of ______ in the mouth.

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

The oesophageal sphincter has a pressure of approximately ______ mmHg.

<p>15–25</p> Signup and view all the answers

Saliva functions include lubrication for swallowing, ______, and antibacterial action.

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

If food does not enter the stomach, the resulting distension triggers a ______ wave.

<p>secondary peristaltic</p> Signup and view all the answers

The ______ phase of swallowing is ensured by peristalsis that moves food into the stomach.

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

Lysozyme and IgA found in saliva provide an ______ action against bacteria.

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

The absorption of Na+ is coupled with the absorption of glu- ______ in adjacent segments.

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

Peristalsis is a propulsion movement triggered by ______.

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

Fat-soluble vitamins (A, D, E and K) are absorbed within the ______ created during fat absorption.

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

The ______ muscle contracts, allowing the circular muscle to also contract midway.

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

Peristaltic contractions propel food a few centimeters and are part of the ______ mechanism.

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

The movements of segmentation and peristalsis are intrinsic and result from the basal electrical ______ in the intestine.

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

Anions such as Cl− are generally absorbed by electro-chemical ______ created by Na+ absorption.

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

The absorption of water is a result of the osmotic ______ established by nutrient absorption.

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

The destruction of ageing red blood cells takes place in the ______.

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

Bilirubin is poorly soluble and is transported to the liver bound to ______.

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

In the intestine, bacteria convert bilirubin to ______.

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

Removal of the pancreas leads to inadequate digestion of protein and lipids, resulting in ______ stools.

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

Enterohepatic circulation involves >90% of secreted bile acids being reabsorbed from the ______.

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

The pigment responsible for giving feces their brown color is ______.

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

The inadequate breakdown of protein due to pancreatic loss leads to ______ and insufficient fat digestion.

<p>progressive weight loss</p> Signup and view all the answers

The remaining 5-10% of bile acids, altered by bacterial flora, are excreted as ______.

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

The absorption of fat-soluble vitamins A, D, E, and K is reduced due to the return of bile acids to the ______.

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

Malabsorption leads to failure to neutralize gastric chyme and results in deficiencies of ______, Ca2+, and PO4−.

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

Secretion of the bicarbonate-rich fluid is stimulated by ______, gastrin, and glucagon.

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

The liver functions in the handling of dietary carbohydrates, protein, and ______.

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

CCK stimulates the contraction of the gall bladder and the release of ______ into the duodenum.

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

Flashcards

Mucosal Protectants

Substances that help protect the stomach lining (mucosa).

Sucralfate

A mucosal protectant that forms a layer over ulcers to protect them.

Bismuth Chelate

A mucosal protectant that also kills H. pylori bacteria.

Misoprostol

A prostaglandin that helps protect the stomach by increasing mucus and blood flow.

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Antacids

Alkaline substances that neutralize stomach acid.

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Vomiting Reflex

A coordinated response involving the brain (medulla) and muscles to expel stomach contents.

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Vomiting Causes

Various triggers, including stomach/duodenum distension, motion sickness, pain, or harmful substances.

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Gastro-esophageal sphincter

A muscle that controls the opening between the stomach and esophagus.

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Small Intestine Absorption

The small intestine absorbs nutrients, fluids, electrolytes, vitamins, and iron/calcium salts.

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Carbohydrate Absorption

Glucose and galactose are absorbed via a sodium-dependent process, while fructose uses a sodium-independent process.

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Sodium-Dependent Absorption

A process where sodium helps transport molecules like glucose and galactose across intestinal cells.

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Absorption process (small intestine)

Process of moving substances from the small intestine into the bloodstream for use by the body.

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Glucose and Galactose absorption

These sugars are absorbed from the small intestine into the bloodstream using a sodium cotransport mechanism.

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Small bowel's primary function

The small bowel's main job is to absorb nutrients from the food we eat.

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Small bowel's absorption features

The small bowel has several characteristics that make it great at absorbing nutrients, including a large surface area due to villi and microvilli and efficient blood supply.

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Fat absorption process

Fat absorption is a multi-step process involving breakdown into smaller molecules, formation of micelles, diffusion across the gut wall, and repackaging into chylomicrons.

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Micelles

Tiny spheres formed in the small intestine to help transport fatty acids and monoglycerides across the gut wall.

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Chylomicrons

Tiny packages that transport absorbed fats from the small intestine to the rest of the body.

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Lacteals

Tiny lymphatic vessels in the small intestine that absorb chylomicrons carrying absorbed fats.

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Why is the small bowel good at absorbing nutrients?

The small bowel has a large surface area due to villi and microvilli and a good blood supply, making it efficient at absorbing nutrients.

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What happens to fats during absorption?

Fats are broken down into smaller molecules (monoglycerides and fatty acids), packaged into micelles for transport across the gut wall, and then repackaged into chylomicrons for delivery to the body.

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Impaired Fat Emulsification

A condition where fats are not properly broken down into smaller droplets in the small intestine, hindering digestion and absorption.

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Trypsin's Role

Trypsin is a crucial digestive enzyme, responsible for activating other key digestive enzymes in the small intestine, allowing for the breakdown of proteins into smaller peptides.

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Dumping Syndrome

A condition where food rapidly empties from the stomach into the small intestine, often leading to discomfort, nausea, and diarrhea.

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Terminal Ileum Resection Effects

Removal of the terminal ileum, the final part of the small intestine, can lead to various digestive and nutritional issues, including bile salt malabsorption, vitamin B12 deficiency, and potential changes in gut flora.

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Bile Salt Reabsorption

The terminal ileum plays a crucial role in reabsorbing bile salts, essential for fat digestion and the enterohepatic circulation.

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Vitamin B12 Deficiency

Resection of the terminal ileum can lead to vitamin B12 deficiency, as this part of the intestine is where it is absorbed.

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Amylase's Role

Amylase is a digestive enzyme that breaks down starches into smaller sugars, primarily in the small intestine.

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Lipolytic Enzymes

These enzymes are crucial for breaking down fats and are activated by trypsin. They include lipase, co-lipase, phospholipase A2, and cholesterol esterase.

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Bilirubin's journey

Bilirubin, a breakdown product of heme, is released from the spleen, transported to the liver bound to albumin, conjugated with glucuronic acid, and excreted in bile.

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Bilirubin's fate in the intestines

Bacteria in the intestines convert bilirubin into urobilinogen, some of which is reabsorbed and excreted in urine or bile, while the rest becomes stercobilin and urobilin, giving feces their brown color.

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What happens in pancreatic resection?

The pancreas produces critical digestive enzymes. Without it, malnutrition ensues due to inadequate digestion of protein and fats, leading to weight loss, fatty stools, and flatulence.

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Bile secretion: Enterohepatic circulation

Over 90% of bile acids are reabsorbed from the intestine, returned to the liver, and reused. This process is essential for efficient fat digestion.

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Bile secretion: Other factors

Besides enterohepatic circulation, other factors independently influence bile secretion.

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Glycogenolysis

The process where glycogen (stored glucose in the liver) is broken down into glucose, releasing it into the bloodstream for energy.

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Protein Synthesis by Liver

The liver is responsible for synthesizing most of the proteins in our blood (like albumin), non-essential amino acids, and many clotting factors.

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Gluconeogenesis

The process of creating glucose from non-carbohydrate sources (like amino acids) in the liver, especially useful during prolonged exercise or starvation.

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Vitamin D Activation (Liver Role)

The liver plays the first step in activating vitamin D, converting it to 25-hydroxycholecalciferol. This is then further activated by the kidney.

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Detoxification in Liver

The liver is the body's main detoxification center, processing and neutralizing a wide range of substances: hormones, drugs, toxins.

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Lipid Metabolism (Liver Role)

The liver is involved in various stages of lipid (fat) metabolism: converting glucose to fatty acids for storage, releasing fatty acids when needed.

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Ammonia Conversion to Urea

The liver converts toxic ammonia from amino acid breakdown into urea, which is then excreted by the kidneys.

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Stercobilinogen

A breakdown product of bilirubin, produced by bacteria in the intestines. It gives feces its brown color.

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What is the function of the pharyngeal phase in swallowing?

The involuntary phase where the superior constrictor muscle raises the soft palate to prevent food from entering the nasopharynx, initiates a wave of contraction (peristalsis) to push food through the upper esophageal sphincter, and inhibits respiration to prevent food entering the respiratory system.

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What is the function of the esophageal phase in swallowing?

The wave of contraction initiated by the superior constrictor in the pharynx continues down the esophagus, propelling the food into the stomach. A secondary peristaltic wave is triggered if the food fails to enter the stomach.

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What is the function of the esophageal sphincter?

Acts as a physiological sphincter (no anatomical distinction) to prevent gastric juices from refluxing back into the esophagus, maintaining a high pressure zone (15–25 mmHg) in the region 2 cm above and 2 cm below the diaphragm.

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What are the roles of saliva?

Saliva, secreted by various glands (parotid, submandibular, sublingual), performs multiple functions: lubrication for swallowing, facilitating taste, antibacterial action with lysozyme and IgA, and initiating starch digestion with salivary amylase.

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Saliva: Parotid gland

Secretes a watery saliva lacking mucus, accounting for approximately 25% of total saliva production. Contains salivary amylase and IgA.

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Saliva: Submandibular gland

Produces a viscous saliva (mixed serous and mucosal), accounting for about 70% of total saliva secretion.

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Saliva: Sublingual gland

Contains mucoproteins and accounts for only 5% of total saliva secretion.

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What are the functions of saliva?

Saliva, a mixture of secretions from different glands, plays a vital role in lubrication for swallowing, facilitating taste, providing antibacterial action with lysozyme and IgA, and initiating carbohydrate digestion with salivary amylase.

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What does secretin do in the duodenum?

Secretin is a hormone released from the duodenal mucosa in response to acidic chyme entering the duodenum. It inhibits gastrin release, reducing gastric acid secretion.

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How do tight junctions protect the stomach?

Tight junctions between epithelial cells of the stomach lining prevent acid from reaching deeper tissues, protecting them from damage.

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What is the enterogastric reflex?

The enterogastric reflex refers to the action of hormones released in the duodenum in response to food, particularly fats, which inhibit gastric activity.

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What is intrinsic factor?

Intrinsic factor (IF) is a protein secreted by parietal cells in the stomach. It binds to vitamin B12, facilitating its absorption in the ileum.

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What are the phases of gastric secretion?

Gastric secretion is regulated in three phases: cephalic, gastric, and intestinal. Each phase involves different stimuli and mechanisms.

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How does the stomach store food?

The stomach's fundus and body act as a storage area, accommodating large volumes of food with minimal pressure increase due to vagal nerve inhibition of muscle contraction.

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What is the role of the antrum and pylorus in gastric motility?

The antrum and pylorus are responsible for mixing and propelling food into the duodenum.

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Iron Absorption

Iron is absorbed in the small intestine in the ferrous (Fe2+) form. Gastric acid converts it to this form and it is then absorbed by a protein called transferrin.

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Calcium Absorption

Calcium absorption in the small intestine depends on a calcium-binding protein. Vitamin D increases the levels of this protein, boosting calcium absorption when blood levels are low.

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Small Intestine Movement

The small intestine moves food in three ways: segmentation for mixing, peristalsis for pushing, and migrating motility complex (MMC) for cleaning during fasting.

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Amino Acid Absorption

Amino acids are absorbed in the small intestine using a sodium cotransport system.

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Fluid Balance in the GI Tract

The GI tract handles a large volume of fluid, with only a small amount excreted in feces. Most ingested and secreted fluid is reabsorbed.

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Small Intestine: Primary Function

The primary function of the small intestine is to absorb nutrients from digested food.

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Small Intestine: Absorption Features

The small intestine has several characteristics that make it great at absorbing nutrients, including a large surface area due to villi and microvilli, and a good blood supply.

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Small Intestine: Role in Bacterial Metabolism

Unabsorbed nutrients that reach the large bowel are metabolized by the resident bacterial flora.

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What is chyme?

Chyme is the partially digested, semi-liquid food mass that moves from the stomach into the small intestine.

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How does peristalsis propel food?

Peristalsis is a wave-like muscle contraction that propels food through the digestive tract. It involves the coordinated contraction and relaxation of circular and longitudinal muscles.

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What is the MMC?

The migrating motor complex (MMC) is a series of contractions that sweep the small intestine clean of any remaining food debris, preventing bacterial overgrowth.

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How are fat-soluble vitamins absorbed?

Fat-soluble vitamins (A, D, E, K) are absorbed within micelles formed during fat absorption. These micelles help transport the vitamins across the intestinal wall.

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What is the role of Na+ in nutrient absorption?

Sodium (Na+) plays a key role in nutrient absorption. It helps transport sugars (glucose and galactose) and amino acids across the intestinal wall.

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How is water absorbed in the small intestine?

Water absorption in the small intestine is driven by the osmotic gradient created by the absorption of nutrients and electrolytes.

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What are the roles of aldosterone and motilin?

Aldosterone stimulates active sodium (Na+) absorption, while motilin may be involved in triggering the migrating motor complex (MMC).

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What are the movements of segmentation and peristalsis?

Segmentation is a rhythmic contraction and relaxation of intestinal muscles that mixes chyme with digestive juices. Peristalsis propels food forward through the digestive tract.

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Bile Acid Recirculation

The process where bile acids are reabsorbed from the small intestine, transported back to the liver, and reused for fat digestion. This cycle is crucial for efficient fat absorption.

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Liver's Role in Bile Production

The liver produces bile, a fluid containing bile acids, which helps emulsify fats in the small intestine, making them easier to digest and absorb.

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Factors Affecting Bile Secretion

Besides bile acid recirculation, other factors independently influence bile secretion, including water, electrolytes (like sodium and bicarbonate), and hormones (like secretin, gastrin, and glucagon).

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Liver's Metabolic Functions

The liver plays a critical role in various metabolic processes, including carbohydrate, protein, and lipid metabolism. It also detoxifies harmful substances.

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CCK's Role in Bile Release

Cholecystokinin (CCK) is a hormone that stimulates the contraction of the gallbladder, releasing bile into the duodenum for fat digestion.

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Bilirubin Breakdown

Bilirubin, a pigment from broken down red blood cells, is processed in the liver. It's converted to a water-soluble form and excreted in bile. In the intestines, bacteria transform it into urobilinogen, which is reabsorbed and excreted in urine or bile, and stercobilinogen, which gives feces their brown color.

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Pancreatic Resection Effects

Removal of the pancreas disrupts digestion. Key digestive enzymes are lost, leading to malnutrition, weight loss, and fatty stools. Without pancreatic enzymes, proteins and fats can't be efficiently broken down.

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Enterohepatic Circulation

Most bile acids are reabsorbed in the intestine and return to the liver for reuse. This recycling system helps with fat digestion.

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CCK and Secretin

Hormones, CCK and Secretin, are released in the small intestine and regulate pancreatic secretions. CCK triggers enzyme-rich fluid release, while Secretin stimulates bicarbonate-rich fluid release.

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What stimulates CCK release?

CCK, a hormone involved in digestion, is released from the duodenal mucosa when lipids, peptides, and amino acids are present. It signals the pancreas to release digestive enzymes.

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What stimulates Secretin release?

Secretin, a digestive hormone, is released from the duodenal mucosa when acidic chyme enters the small intestine. It tells the pancreas to release bicarbonate-rich fluid to neutralize the acid.

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Study Notes

Gastrointestinal System Functions

  • Oral cavity: Teeth crush and tear food, tongue forms a bolus, saliva initiates carbohydrate digestion
  • Pharynx and esophagus: Convey food from mouth to stomach
  • Stomach: Stores, mechanically and chemically digests food, regulates chyme passage, secretes intrinsic factor
  • Small bowel: Majority of food digestion and absorption occurs
  • Large bowel: Water removal from undigested food, stores in rectum, vitamin K and B vitamins produced by bacteria
  • Liver: Carbohydrate, protein, and lipid metabolism, creates plasma proteins, clotting factors, detoxifies and eliminates waste, toxins
  • Gallbladder: Stores and concentrates bile
  • Pancreas: Exocrine and endocrine functions, secretes digestive enzymes

Nervous and Hormonal Regulation

  • Myenteric (Auerbach's) plexus: Between circular and longitudinal muscle layers, motor function
  • Submucosal (Meissner's) plexus: Within submucosa, sensory function
  • Enteric nervous system: Responds to gut transmitters (e.g., cholecystokinin, substance P, VIP, somatostatin), responsible for most gut secretion and motility.
  • Extrinsic nervous system: Sympathetic (vasoconstriction, inhibits secretion, sphincter contraction, ↓ motility) and parasympathetic (increases secretion, sphincter relaxation, ↑ motility).
  • Hormones and neurotransmitters: Regulate GI motility and secretion (e.g., gastrin, secretin, CCK, pancreatic polypeptide, GIP, motilin, enteroglucagon, neurotensin).

Oral Cavity, Pharynx, and Oesophagus

  • Chewing: Teeth cut, grind, tear food, mix with saliva and mucus for swallowing
  • Saliva: Secretion from parotid, submandibular, and sublingual glands. Function in lubrication, speech, taste, and antibacterial action (enzymes like amylase)

Swallowing

  • Oral phase: Voluntary pushing of food bolus to oropharynx
  • Pharyngeal phase: Involuntary, pushes food into esophagus, and prevents food from entering nasopharynx
  • Oesophageal phase: Peristalsis moves food to stomach
  • Oesophageal sphincter: High-pressure region preventing gastric reflux (between esophagus and stomach)

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Gastrointestinal System PDF

Description

Test your knowledge on the functions of the gastrointestinal system and its regulatory mechanisms. This quiz covers the roles of various organs, including the stomach, liver, and pancreas, as well as the nervous and hormonal regulation involved in digestion. Perfect for students studying human anatomy and physiology.

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