Gastrointestinal System Flashcards
What is the primary function of the digestive system?
To break down food into smaller molecules that can be absorbed and used by the body.
What are the main components of the digestive system?
The mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus, as well as accessory organs such as the liver, pancreas, and gallbladder.
What is peristalsis?
Coordinated muscle contractions that propel food through the digestive tract.
What are sphincters and what is their role?
Muscular rings that control the flow of food between different sections of the digestive tract.
What are the four main layers of the GI tract wall?
Mucosa, Submucosa, Muscularis externa, Serosa
What is the function of the omentum?
A double layer of peritoneum that connects the stomach to other abdominal organs, providing support and protection.
What is the role of the enteric nervous system (ENS)?
To control the movement and function of the digestive system, often referred to as the “second brain” of the gut.
What are the two main branches of the autonomic nervous system that regulate digestion?
The sympathetic and parasympathetic nervous systems.
How does the sympathetic nervous system affect digestion?
It generally inhibits digestive processes, diverting blood flow away from the digestive system during times of stress or danger (“fight-or-flight” response).
How does the parasympathetic nervous system affect digestion?
It stimulates digestive processes, promoting digestion and absorption of nutrients (“rest-and-digest” response).
What are the two main plexuses of the ENS?
The myenteric (Auerbach’s) plexus and the submucosal (Meissner’s) plexus.
What is the function of the myenteric plexus?
Primarily controls the motility of the GI tract.
What is the function of the submucosal plexus?
Primarily regulates secretions and blood flow in the GI tract.
Name some major neurotransmitters involved in the ENS.
Acetylcholine, dopamine, serotonin (5-HT), norepinephrine, vasoactive intestinal peptide (VIP), and nitric oxide.
What is the role of commensal bacteria in the gut?
They aid in digestion, nutrient absorption, and protection against harmful bacteria.
What is the approximate volume of fluid processed by the GI tract daily?
Approximately 8.5 liters.
What is the net driving force for water movement in the GI tract?
Pnet = ΔP – Δπ (where ΔP represents the hydrostatic pressure difference and Δπ represents the osmotic pressure difference).
Appendix is thought to be leftover from the __________.
cecum
What is the primary force driving water movement across epithelia in the GI tract?
The osmotic pressure difference (Δπ).
How is water movement regulated in the GI tract?
Primarily by regulating the movement of solutes.
What is the role of cholecystokinin (CCK)?
A hormone that stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder.
What is the role of Gastric Inhibitory Peptide (GIP)?
A hormone that inhibits gastric acid secretion and stimulates insulin release.
True or False: Bacterial cells in a human outnumber human cells in said human.
True
What are the general functions of the upper GI tract?
Ingestion, initial digestion, and propulsion of food.
What are the general functions of the small intestine?
Primary site of nutrient absorption
What are the general functions of the large intestine?
Absorption of water and electrolytes, formation and storage of feces.
Where is the pyloric sphincter located and what is its function?
Located between the stomach and the small intestine, controlling the flow of chyme from the stomach into the duodenum.
Where is the ileocecal valve located and what is its function?
Located between the small intestine and the large intestine, preventing backflow of fecal material into the small intestine.
What are some potential diseases of the GI tract?
Gastroesophageal reflux disease (GERD), peptic ulcer disease, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and colorectal cancer.
What are some potential therapeutic approaches for GI disorders?
Lifestyle modifications, medications (e.g., antacids, proton pump inhibitors, antidiarrheals), and surgery.
What does cholera toxin activate?
CFTR
A majority of ________ (type of neurotransmitter) is used in the gastrointestinal system.
serotonin
What is the role of the central timing network (CTN) in chewing?
The CTN in the pontine & medullary brain stem is responsible for the rhythmic pattern of chewing.
How is chewing regulated?
Chewing is regulated by sensory feedback from the mouth and jaw muscles, which modulates the activity of the CTN.
What is the approximate daily volume of saliva production?
Saliva production is approximately 1.5 L per day.
List the accessory organs involved in upper GI processes.
Salivary glands are the accessory organs in the upper GI tract.
Name the three major salivary glands.
The three major salivary glands are the parotid, submandibular, and sublingual glands.
What are the primary constituents of saliva?
Saliva consists of water, electrolytes, enzymes like amylase, and mucus.
Blockage of the parotid salivary ducts can cause _________, which is a common ailment in the elderly.
swelling
What is the basic chemical formula of starch?
The basic chemical formula of starch is (C6H10O5)n.
What is the function of salivary amylase?
Salivary amylase initiates the digestion of starch, breaking it down into smaller sugar molecules.
What are the key functions of saliva?
Saliva lubricates food for swallowing, dissolves food for taste, initiates starch digestion, and helps maintain oral hygiene by neutralizing acids and washing away food debris.
What is the first enzyme encountered in the GI system?
Amylase (technically any in the saliva, but he emphasized this one)
What is Sjogren’s syndrome?
Sjogren’s syndrome is an autoimmune disorder characterized by chronic inflammation of the salivary and lacrimal glands, leading to dry mouth and eyes.
The submandibular gland contributes ____% of total saliva.
71%
Describe the osmolarity of saliva as it is initially secreted from the acini.
Saliva is initially secreted as an isosmotic fluid from the salivary acini.
Which receptors mediate the parasympathetic regulation of salivary secretion?
M1 and M3 muscarinic receptors on acinar cells mediate parasympathetic regulation of salivary secretion.
True or False: In humans, lingual lipase is a relatively minor portion of digestion.
True (it’s fine if you don’t have it)
What is the role of Ca2+ signaling in the regulation of salivary fluid secretion?
Increased intracellular Ca2+ levels activate ion channels and transporters, driving the secretion of electrolytes and water into the acinar lumen.
Which ion channel plays a primary role in saliva secretion?
CaCC (TMEM1) is the primary ion channel driving salivary secretion.
What is the role of the salivary ducts in modifying the composition of saliva?
Salivary ducts reabsorb Na+ and Cl- while secreting K+ and HCO3-, resulting in hypotonic saliva.
Saliva that leaves the salivary glands is _______osmotic (hyper/hypo) to plasma.
hypo
Which transporter is involved in bicarbonate secretion in salivary ducts?
The SLC26s transporter family is involved in bicarbonate secretion in salivary ducts.
How does the sympathetic nervous system regulate salivary secretion?
Sympathetic stimulation, acting via β1-adrenergic receptors, primarily increases amylase secretion and also causes vasoconstriction.
What is an example of an experiment that demonstrates the cephalic phase?
Pavlov’s dog (salivation)
What is the medical term for excessive drooling during sleep?
Sialorrhea is the medical term for excessive drooling during sleep.
Explain why drooling can occur during sleep.
Drooling during sleep can occur due to reduced swallowing frequency while saliva production continues at a baseline rate.
What is the primary function of the esophagus?
The esophagus transports food from the pharynx to the stomach.
What is a hiatal hernia?
A hiatal hernia occurs when the upper part of the stomach protrudes through the diaphragm into the chest cavity.
What is the role of the nucleus tractus solitarius (NTS) in swallowing?
The NTS in the brainstem receives sensory input from the pharynx and esophagus, coordinating the swallowing reflex.
Why have saliva produced also in the sympathetic response?
To fight physically (via biting, evolutionarily) and to fight off infection
Describe the two main vagal efferent pathways involved in esophageal motility.
The vagus nerve has two pathways: an excitatory pathway using acetylcholine and an inhibitory pathway using nitric oxide.
What is the function of the lower esophageal sphincter (LES)?
The LES prevents the reflux of stomach contents into the esophagus
What is transient LES relaxation (TLESR)?
TLESR is a brief relaxation of the LES that can allow for the expulsion of gas from the stomach but may also contribute to acid reflux.
True or False: More saliva is produced during sleep.
False, less is produced (you also swallow less, hence drooling can occur)
How is the LES regulated?
The LES is regulated by a balance of excitatory and inhibitory neural inputs, as well as hormonal and myogenic factors.
Which neurotransmitter is involved in the inhibitory pathway of esophageal peristalsis?
Nitric oxide is the primary inhibitory neurotransmitter in esophageal peristalsis.
What happens to the distribution of excitatory and inhibitory innervation along the length of the esophagus?
Excitatory innervation decreases distally, while inhibitory innervation increases distally in the esophagus.
How does the changing distribution of innervation contribute to peristalsis?
The gradient of innervation ensures that contraction occurs sequentially along the esophagus, propelling food toward the stomach.
What is the role of the dorsal motor nucleus in esophageal peristalsis?
The dorsal motor nucleus of the vagus nerve contains preganglionic neurons that control both excitatory and inhibitory pathways involved in esophageal peristalsis.
What is the purpose of stratified squamous epithelial cells in the esophagus?
Protection (similar to skin, can lose top layer due to abrasion and still have layers)
In the DMN, the _________ is an excitatory pathway while the _________ is an inhibitory pathway.
rostral, caudal
What is the primary function of the stomach?
The stomach stores food, mixes it with gastric secretions, and begins the process of protein digestion.
What are the key regions of the stomach?
The stomach is divided into the fundus, body, antrum, and pylorus.
What are rugae?
Rugae are folds in the stomach lining that allow for expansion as the stomach fills with food.
What are the major cell types found in the gastric glands?
The gastric glands contain mucous cells, parietal cells, chief cells, and enteroendocrine cells.
What is the role of surface mucus cells?
Surface mucus cells secrete mucus and bicarbonate, which protect the stomach lining from the acidic environment.
What is the primary function of parietal cells?
Parietal cells secrete hydrochloric acid (HCl) and intrinsic factor.
Describe the process of HCl production in parietal cells.
Parietal cells use carbonic anhydrase to convert carbon dioxide and water into carbonic acid, which then dissociates into H+ and HCO3-. H+ ions are actively pumped into the stomach lumen by the H+/K+ ATPase pump, while HCO3- is exchanged for Cl- across the basolateral membrane. Cl- then enters the lumen through Cl- channels, combining with H+ to form HCl.
What is the role of intrinsic factor?
Intrinsic factor is necessary for the absorption of vitamin B12 in the small intestine.
What are the three phases of HCl secretion regulation?
The three phases are the cephalic phase, gastric phase, and intestinal phase.
Describe the cephalic phase of HCl secretion.
The cephalic phase is triggered by the sight, smell, taste, or thought of food, and is mediated by vagal nerve stimulation, which releases acetylcholine (ACh) and gastrin-releasing peptide (GRP). ACh stimulates parietal cells directly, while GRP stimulates gastrin release from G cells. Gastrin further enhances HCl secretion.
Describe the gastric phase of HCl secretion.
The gastric phase is initiated by the presence of food in the stomach, leading to distension and the release of gastrin and histamine.
Describe the intestinal phase of HCl secretion.
The intestinal phase begins when chyme enters the small intestine. Initially, it stimulates HCl secretion, but as digestion progresses, it inhibits HCl secretion through the release of hormones like secretin and gastric inhibitory peptide (GIP)
How is parietal cell HCl production inhibited?
HCl production is inhibited by negative feedback mechanisms involving somatostatin and prostaglandins. Low pH in the stomach stimulates somatostatin release, which inhibits gastrin release. Prostaglandins also inhibit acid secretion and stimulate mucus and bicarbonate production.
What is the role of chief cells?
Chief cells secrete pepsinogen, the inactive precursor to the enzyme pepsin.
How is pepsinogen activated?
Pepsinogen is activated to pepsin by the low pH in the stomach lumen. Pepsin then autocatalytically activates more pepsinogen.
What is the function of pepsin?
Pepsin is a proteolytic enzyme that initiates protein digestion in the stomach.
What is gastric accommodation?
Gastric accommodation refers to the relaxation of the stomach fundus in response to food intake, allowing the stomach to expand without significant increases in intragastric pressure. This process is mediated by vagal reflexes and the release of nitric oxide.
How does the stomach mix food with gastric juices?
The stomach mixes food with gastric juices through peristaltic contractions that originate in the pacemaker region of the stomach. These contractions propel food towards the pylorus, where it is mixed with gastric secretions and gradually emptied into the duodenum.
What factors influence the rate of gastric emptying?
The rate of gastric emptying is influenced by factors such as the volume and composition of the chyme, as well as hormonal and neural signals from the duodenum.
What is the role of the pyloric sphincter?
The pyloric sphincter regulates the flow of chyme from the stomach into the duodenum.
Describe the process of the vomiting reflex.
The vomiting reflex is a complex process coordinated by the vomiting center in the medulla oblongata. It is triggered by various stimuli, including toxins, motion sickness, and distension of the stomach or duodenum. The reflex involves a sequence of events, including nausea, retching, and forceful expulsion of stomach contents through the mouth.
What is an anastomosis?
An anastomosis is a surgical connection created between two tubular structures, such as blood vessels or loops of intestine. In the context of the GI tract, an anastomosis may be created after surgical removal of a portion of the intestine.
What are enteroendocrine cells?
Enteroendocrine cells are specialized cells in the gastric mucosa that release hormones, including gastrin, histamine, and somatostatin, which regulate various aspects of gastric function.
What is the role of histamine in gastric acid secretion?
Histamine, released from enterochromaffin-like (ECL) cells, acts as a potent stimulator of parietal cell HCl secretion.
What is the effect of NSAIDs on parietal cell function?
Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis, which can reduce mucus and bicarbonate production, potentially increasing the risk of gastric ulcers.
What is the role of somatostatin in regulating gastric function?
Somatostatin, released from D cells in the stomach, acts as a general inhibitor of gastric function, suppressing HCl secretion, gastrin release, and pepsinogen secretion.
What is Zollinger-Ellison syndrome?
Zollinger-Ellison syndrome is a rare condition characterized by gastrin-secreting tumors, leading to excessive HCl production and severe peptic ulcers.
What are some common therapeutic approaches to managing gastric acid-related disorders?
Therapeutic approaches include lifestyle modifications, antacids, H2 receptor blockers, proton pump inhibitors, and in some cases, surgery.
What is gastroparesis?
Gastroparesis is a condition characterized by delayed gastric emptying, often due to nerve damage or other factors that disrupt normal stomach muscle function.
What are some potential complications of chronic vomiting?
Chronic vomiting can lead to dehydration, electrolyte imbalances, malnutrition, and esophageal damage.
The two parts of the omentum are known as the _______ omentum and the _________ omentum.
lesser, greater
Name the types of bacteria found in the stomach.
Lactobacillus, Candida, Streptococcus, Helicobacter pylori, Peptostreptococcus
Approximately how many bacteria live in the stomach?
0-100 (1E2)
Name the types of bacteria found in the colon.
Bacteroides, Bifidobacterium, Clostridium coccoides, Clostridium leptum/Fusobacterium
Approximately how much bacteria live in the colon?
10E11
What are the four major functions of the digestive system (broad summary)?
Digestion, Absorption, Secretion, Motility
What are the two types of muscle (shape) that are found throughout the GI system?
Circular, longitudinal
_________ muscle exists between the Myenteric plexus and the Submucosal plexus.
Circular
What class of macromolecules are gastrin, CCK, secretin, and GIP?
Peptides
Where is gastrin produced?
Antrum of stomach
Where is CCK produced?
Small intestine
Where is secretin produced?
Small intestine
Where is GIP produced?
Small intestine
What are the factors that inhibit gastrin release in the stomach?
Acid in the stomach; somatostatin
Gastrin ________(inhibits/stimulates) acid secretion in the stomach.
stimulates
CCK _________(inhibits/stimulates) acid secretion in the stomach.
inhibits
Secretin __________(inhibits/stimulates) acid secretion in the stomach.
inhibits
Secretin __________(inhibits/stimulates) motility in the stomach.
inhibits
CCK __________(inhibits/stimulates) motility in the stomach.
inhibits
Gastrin __________(inhibits/stimulates) motility in the stomach.
inhibits
Gastrin __________(inhibits/stimulates) motility in the small intestine.
stimulates (ileum)
Gastrin __________(inhibits/stimulates) mass movement in the large intestine.
stimulates
CCK __________(inhibits/stimulates) enzyme secretion in the pancreas.
stimulates
CCK _________(inhibits/stimulates) contraction of the gallbladder.
stimulates
CCK _________(constricts/relaxes) the Sphincter of Oddi.
relaxes
GIP ___________(inhibits/stimulates) insulin secretion in the pancreas.
stimulates
Secretin ___________(inhibits/stimulates) bicarbonate secretion in the pancreas.
stimulates
Secretin ___________(inhibits/stimulates) bicarbonate secretion in the liver.
stimulates
In regards to bicarbonate secretion in the pancreas, CCK potentiates ________’s actions.
secretin
In regards to bicarbonate secretion in the liver, CCK potentiates _________’s actions.
secretin
In regards to enzyme secretion in the pancreas, secretin potentiates _______’s actions.
CCK
Cholecystokinin (CCK) _______(increases/decreases) enzyme secretion in the pancreas and ________(increases/decreases) contraction in the gallbladder.
increases, increases
Gastric Inhibitory Peptide (GIP) _________(increases/decreases) fluid absorption when acting in an exocrine manner, and ________(increases/decreases) insulin release when acting in an endocrine manner.
decreases, increases
Gastrin-releasing peptide ________(increases/decreases) gastrin release.
increases
Guanylin ________(increases/decreases) fluid absorption.
increases
Motilin ________(increases/decreases) smooth muscle contraction.
increases
Peptide YY _________(increases/decreases) vagally-mediated acid secretion, and _________(increases/decreases) enzyme and fluid secretion.
decreases, decreases
Substance P acts as a __________.
neurotransmitter
Secretin _________(increases/decreases) fluid secretion by pancreatic ducts, __________(increases/decreases) gastric acid secretion, and ________(increases/decreases) gastrin release.
increases, decreases, decreases
Somatostatin __________(increases/decreases) fluid absorption, _________(increases/decreases) fluid secretion, _________(increases/decreases) smooth muscle contraction, _________(increases/decreases) endocrine and exocrine secretions, and _________(increases/decreases) bile flow.
increases, decreases, increases, decreases, decreases
VIP __________(increases/decreases) smooth muscle relaxation, __________(increases/decreases) secretion by the small intestine, and ________(increases/decreases) secretion by the pancreas.
increases, increases, increases
What does neurotensin do?
Vasoactive stimulation of histamine release
What are the stimuli for release of gastrin?
Amino acids, peptides in stomach; parasympathetic nerves
What are the stimuli for release of CCK?
Amino acids, fatty acids in small intestine
What are the stimuli for release of secretin?
Acid in small intestine
What are the stimuli for release of GIP?
Glucose, fat in the small intestine
What percentage of blood flow to the liver comes from the portal vein?
Approximately 72%
Which major blood vessels supply the liver?
The portal vein and the hepatic artery
What are the three main functions of the liver?
Metabolic regulation, detoxification, and protein synthesis
What is the structural and functional unit of the liver?
The hepatic lobule
What does Metabolic Regulation mean (in regards to the liver)?
Processing nutrients, producing bile, and storing vitamins and minerals.
What does Detoxification mean (in regards to the liver)?
Filtering toxins from the blood
What does Protein Synthesis mean (in regards to the liver)?
Producing proteins essential for blood clotting and other bodily functions.
Describe the flow of blood through a hepatic lobule.
Blood flows from the portal vein and hepatic artery through sinusoids to the central vein.
What are the major cell types found in a hepatic lobule?
Hepatocytes, Kupffer cells, and endothelial cells
What is the primary function of hepatocytes?
Hepatocytes are the metabolic “factories” of the liver, responsible for most of the liver’s functions.
What is the function of Kupffer cells?
Kupffer cells are macrophages that engulf and destroy bacteria, cellular debris, and other foreign substances in the liver.
What is unique about the endothelial cells lining the hepatic sinusoids?
They are fenestrated, meaning they have pores that allow for easy exchange of substances between the blood and hepatocytes.
What is bile?
A yellow-green fluid produced by the liver that aids in the digestion and absorption of fats.
What are the main components of bile?
Bile salts, cholesterol, bilirubin, and water
What is the function of bile salts?
Bile salts emulsify fats, breaking them down into smaller droplets for easier digestion and absorption.
Where are bile acids synthesized?
In the hepatocytes from cholesterol
Describe the pathway of bile synthesis and secretion.
Bile acids are synthesized from cholesterol in hepatocytes, then transported into bile canaliculi and through the biliary tree to the gallbladder for storage or to the duodenum for use in digestion.
What is the function of the gallbladder?
The gallbladder stores and concentrates bile.
What hormone stimulates the gallbladder to contract and release bile?
Cholecystokinin (CCK)
What is the enterohepatic circulation of bile acids?
The process by which bile acids are reabsorbed from the intestine and returned to the liver for reuse.
What transporter protein is responsible for the uptake of bile acids from the blood into hepatocytes?
The Sodium/Taurocholate Co-transporting protein (NTCP)
What transporter protein is responsible for the secretion of bile salts from hepatocytes into bile canaliculi?
The bile salt export pump (BSEP)
What is the consequence of inhibition of the BSEP transporter?
Inhibition of BSEP can lead to the buildup of bile salts in the liver, causing cholestasis.
What are the two main types of gallstones?
Cholesterol stones and pigment stones
What is the most common type of gallstone?
Cholesterol stones, making up around 80% of cases
What are pigment stones made of?
Bilirubin and calcium
What is litholysis?
The dissolution of gallstones using solvents.
What is jaundice?
A yellowish discoloration of the skin and eyes caused by elevated levels of bilirubin in the blood.
What is cholestasis?
A reduction or stoppage of bile flow.
What are cholangiocytes?
The epithelial cells lining the bile ducts.
What is the function of cholangiocytes?
Cholangiocytes modify the composition of bile by secreting bicarbonate and water.
What transporter is involved in bicarbonate secretion by cholangiocytes?
The cystic fibrosis transmembrane conductance regulator (CFTR)
What hormone stimulates bicarbonate secretion by cholangiocytes?
Secretin
What is the role of the hepatic nervous system?
It regulates liver function in response to various stimuli, including nutrient intake, hormone levels, and stress.
What are the two branches of the autonomic nervous system that innervate the liver?
The sympathetic and parasympathetic nervous systems
What is the effect of sympathetic stimulation on hepatic blood flow?
Sympathetic stimulation causes constriction of hepatic sinusoids, diverting blood flow away from the liver.
What is the effect of parasympathetic stimulation on hepatic blood flow?
Parasympathetic stimulation causes relaxation of hepatic sinusoids, increasing blood flow to the liver.
What neurotransmitters are released by the sympathetic and parasympathetic nerves in the liver?
Sympathetic nerves release norepinephrine and epinephrine, while parasympathetic nerves release acetylcholine.
How does the liver sense lipid levels?
The liver senses lipid levels through mechanisms that are not fully understood, possibly involving protein kinase C (PKC).
What is the consequence of hepatic lipid sensing?
Hepatic lipid sensing can lead to increased glucose production and decreased glycogenesis, potentially contributing to insulin resistance.
What is the role of vagal afferent nerves in hepatic lipid sensing?
Vagal afferent nerves transmit signals from the liver to the hypothalamus, which then regulates glucose metabolism.
How does hepatic lipid sensing conflict with lipid sensing in the GI tract and brain?
Hepatic lipid sensing reduces the inhibitory effects of insulin on glucose production, while lipid sensing in the GI tract and brain promotes insulin sensitivity.
What are the potential implications of hepatic lipid sensing for insulin resistance?
Hepatic lipid sensing may contribute to the development of insulin resistance by promoting glucose production and inhibiting insulin’s effects on the liver.
What are the “Ins” of a hepatic lobule?
Portal vein and hepatic artery
What are the “Outs” of a hepatic lobule?
Central vein and bile ductule
What is the function of the space of Disse?
It is a space between the sinusoidal endothelial cells and the hepatocytes where exchange of substances occurs.
What is the significance of the fenestrated endothelium of the hepatic sinusoids?
The fenestrations allow for the passage of large molecules, such as proteins and lipoproteins, between the blood and the hepatocytes.
What are the consequences of hepatic circulation regarding liver functions?
The unique circulation exposes the liver to a wide range of nutrients, toxins, and hormones, enabling its diverse metabolic, detoxification, and protein synthesis functions.
What is the effect of hepatic denervation?
It disrupts the neural control of liver function and can lead to alterations in glucose and lipid metabolism.
What is the role of the vagus nerve in liver function?
The vagus nerve carries parasympathetic signals that stimulate hepatic blood flow and glucose uptake.
What are the potential therapeutic targets for liver diseases related to bile secretion?
Potential targets include the transporter proteins involved in bile acid uptake and secretion, such as NTCP and BSEP.
What is the endocrine function of the pancreas?
The endocrine pancreas secretes hormones, such as insulin and glucagon, into the bloodstream.
Where is the pancreas located?
The pancreas is located in the upper abdomen, behind the stomach.
What are the main pancreatic enzymes involved in protein digestion?
Trypsin and chymotrypsin
Where are trypsin and chymotrypsin activated?
They are activated in the small intestine.
What are zymogens?
Zymogens are inactive precursors of enzymes.
Why are pancreatic enzymes secreted as zymogens?
To prevent them from digesting the pancreas itself.
What activates trypsinogen to trypsin?
Enterokinase, an enzyme found in the intestinal brush border, activates trypsinogen to trypsin.
What other enzymes does trypsin activate?
Trypsin activates other pancreatic zymogens, including chymotrypsinogen, proelastase, and procarboxypeptidase.
What is the main pancreatic enzyme involved in fat digestion?
Pancreatic lipase
Where is pancreatic lipase active?
It is active in the duodenum.
What is the function of colipase?
Colipase helps pancreatic lipase bind to fat droplets in the presence of bile salts.
What is the function of phospholipase A2?
Phospholipase A2 cleaves fatty acids from the sn-2 position of phospholipids.
What is a common fatty acid found at the sn-2 position of phospholipids?
Arachidonic acid, a precursor to eicosanoids
What is the function of pancreatic amylase?
Pancreatic amylase breaks down starch into smaller sugar molecules.
What is the function of bicarbonate in pancreatic juice?
Bicarbonate neutralizes the acidic chyme entering the duodenum from the stomach.
How is pancreatic juice secretion regulated?
Pancreatic juice secretion is regulated by both neural and hormonal mechanisms.
What are the main hormones that stimulate pancreatic secretion?
Secretin and cholecystokinin (CCK)
What stimulates secretin release?
The presence of acid in the duodenum stimulates secretin release.
What effect does secretin have on the pancreas?
Secretin stimulates the pancreatic duct cells to secrete bicarbonate-rich fluid.
What stimulates CCK release?
The presence of fats and proteins in the duodenum stimulates CCK release.
What effect does CCK have on the pancreas?
CCK stimulates the pancreatic acinar cells to secrete digestive enzymes.
What role does the vagus nerve play in pancreatic secretion?
The vagus nerve provides parasympathetic stimulation to the pancreas, increasing enzyme and bicarbonate secretion.
What are the three phases of pancreatic secretion?
Cephalic, gastric, and intestinal phases
What triggers the cephalic phase of pancreatic secretion?
The sight, smell, or thought of food triggers the cephalic phase.
What mediates the cephalic phase of pancreatic secretion?
The vagus nerve mediates the cephalic phase.
What triggers the gastric phase of pancreatic secretion?
Distension of the stomach triggers the gastric phase.
What mediates the gastric phase of pancreatic secretion?
Both neural and hormonal mechanisms mediate the gastric phase.
What triggers the intestinal phase of pancreatic secretion?
The entry of chyme into the duodenum triggers the intestinal phase.
What mediates the intestinal phase of pancreatic secretion?
The hormones secretin and CCK primarily mediate the intestinal phase.
What is the migrating motor complex (MMC)?
The MMC is a pattern of peristaltic contractions that sweeps through the digestive tract between meals.
What is the function of the MMC?
The MMC helps clear the stomach and small intestine of undigested food debris and bacteria.
What happens to the MMC during feeding?
Feeding terminates the MMCs
What are the two phases of the MMC cycle?
Phase I, a prolonged quiescent period, and Phase II, a period of increasing contractions
What is the role of motilin in the MMC?
Motilin, a hormone, is thought to initiate the MMC.
What are the main functions of pancreatic fluid secretion?
○ Provides a medium for the transport of enzymes.
○ Neutralizes acidic chyme.
○ Helps lubricate the intestinal lining.
What are the main transporters involved in pancreatic fluid secretion?
The main transporters include the CFTR channel and SLC26A3/6.
What is the role of CFTR in pancreatic fluid secretion?
CFTR is a chloride channel that allows for the movement of chloride ions into the pancreatic duct lumen, driving water secretion.
What is the role of SLC26A3/6 in pancreatic fluid secretion?
SLC26A3/6 are anion exchangers that transport bicarbonate into the duct lumen.
How does flow rate affect pancreatic secretion composition?
At high flow rates, pancreatic juice is rich in bicarbonate, while at low flow rates, it is more concentrated with enzymes.
What is the difference between gastric lipase and pancreatic lipase?
Gastric lipase works in the acidic environment of the stomach, while pancreatic lipase is optimal in the neutral-to-alkaline environment of the duodenum.
How does the regulation of pancreatic secretion integrate with the regulation of the stomach and liver?
Hormonal signals like secretin and CCK, as well as neural input from the vagus nerve, coordinate the functions of the stomach, liver, and pancreas to optimize digestion.
What is the role of GRP in pancreatic secretion?
Gastrin-releasing peptide (GRP), released by vagal nerves, stimulates both enzyme and bicarbonate secretion from the pancreas.
What are the effects of sympathetic stimulation on pancreatic secretion?
Sympathetic stimulation primarily affects the endocrine pancreas, decreasing insulin and increasing glucagon release, and may have a tonic inhibitory effect on exocrine secretion.
What is the significance of vagal circuits being separate for exocrine and endocrine pancreatic function?
This separation allows for fine-tuned control of both digestive enzyme release and hormone secretion, tailoring the pancreatic response to specific physiological needs.
What are the major functions of the small intestine?
○ Segmentation: Mixing chyme with digestive juices
○ Peristalsis: Propelling chyme through the intestine
○ Digestion: Completing the breakdown of carbohydrates, proteins, nucleic acids, and lipids
○ Absorption: Absorbing around 90% of nutrients and water
What is the approximate length and surface area of the human small intestine?
The human small intestine is about 6 meters (19 feet) long and has a surface area of approximately 200 square meters, which is about the size of a singles tennis court.
How does the structure of the small intestine contribute to its function?
The small intestine has a highly folded luminal surface with villi and microvilli that greatly increase its surface area for absorption; The presence of crypts between the villi houses stem cells for cell renewal and contains various cell types for secretion and absorption.
What are the major cell types found in the small intestine and their functions?
● Enterocytes: Responsible for absorption of nutrients and water
● Goblet cells: Secrete mucus for lubrication and protection
● Enteroendocrine cells: Secrete hormones that regulate digestion and absorption
● Paneth cells: Secrete antimicrobial peptides for defense against pathogens
Describe the two main types of intestinal motility and their functions.
● Segmentation: Involves rhythmic contractions of circular muscles that mix the chyme with digestive juices and decrease the unstirred layer, enhancing contact with the absorptive surface. It occurs primarily after eating.
● Peristalsis: Involves coordinated contractions of circular and longitudinal muscles that propel the chyme through the intestine. Upstream, circular muscles contract while longitudinal muscles relax. Downstream, circular muscles relax and longitudinal muscles contract.
What are migrating motor complexes (MMCs)?
MMCs are patterns of motility that occur during fasting periods to clear the small intestine of residual contents. They consist of three phases.
What is Phase I of MMCs?
Prolonged quiescent period with little to no contractions.
What is Phase II of MMCs?
Increasing contraction frequency and intensity.
What is Phase III of MMCs?
Peak mechanical activity with strong, repetitive contractions
_________ terminates MMCs.
Eating
Where in the small intestine does the majority of nutrient absorption occur?
The majority of nutrient absorption occurs in the jejunum, the middle section of the small intestine.
How are proteins absorbed in the small intestine?
Luminal digestion, Brush border digestion, Absorption
What is luminal digestion?
Proteins are initially broken down into peptide fragments by pancreatic enzymes like trypsin and chymotrypsin in the duodenum.
What is brush border digestion?
Further breakdown into smaller peptides and amino acids occurs at the brush border of enterocytes by peptidases.
Amino acids are absorbed into _________ via specific transporters, often coupled with sodium. Di- and tri-peptides are absorbed via a proton-coupled transporter.
enterocytes
Amino acids are transported out of enterocytes into the blood capillaries of the _____.
villi
What is lysinuric protein intolerance?
Lysinuric protein intolerance is a rare genetic disorder characterized by defective transport of dibasic amino acids (lysine, arginine, ornithine) in the small intestine and kidneys. This leads to protein intolerance, growth retardation, and other complications.
In the small intestine, carbohydrates are broken down into disaccharides and then monosaccharides by __________ amylase and brush border enzymes like lactase, sucrase, and maltase.
pancreatic
Only ________________ (glucose, galactose, fructose) can be absorbed by enterocytes. Glucose and galactose are absorbed via SGLT1 (sodium-glucose cotransporter 1), while fructose is absorbed via GLUT5 (glucose transporter 5).
monosaccharides
Monosaccharides are transported out of enterocytes into the blood capillaries of the villi via ______.
GLUT2
What is lactose intolerance?
Lactose intolerance occurs when the small intestine does not produce enough lactase, the enzyme that breaks down lactose (milk sugar) into glucose and galactose.
How does lactose intolerance affect carbohydrate absorption?
Undigested lactose cannot be absorbed and causes symptoms like bloating, gas, and diarrhea.
How does lactase deficiency affect the levels of hydrogen in the breath?
In individuals with lactase deficiency, undigested lactose is fermented by bacteria in the colon, producing hydrogen gas. This leads to elevated levels of hydrogen in the breath.
How does lactase deficiency affect the levels of glucose in the breath?
Since glucose is not absorbed from lactose, blood glucose levels do not rise as much after consuming lactose in lactase-deficient individuals.
How are lipids absorbed in the small intestine?
Emulsification, luminal digestion, micelle formation, diffusion into enterocytes, re-esterification, transport into lymph
What are chylomicrons, and what is their function?
Chylomicrons are lipoprotein particles composed of triglycerides, phospholipids, cholesterol, and proteins; They transport dietary lipids from the intestines to other tissues in the body via the lymphatic system.
What is the role of ApoB48 in lipid absorption?
ApoB48 is a protein essential for the assembly and secretion of chylomicrons in enterocytes.
Without ApoB48, lipid absorption is severely impaired, leading to a condition called ______________.
abetalipoproteinemia
What are VLDLs, and how are they related to lipid transport?
VLDLs (very-low-density lipoproteins) are lipoprotein particles synthesized in the liver that transport triglycerides from the liver to other tissues.
Name some key apolipoproteins in lipid transport.
ApoB100, ApoC-2, ApoE
What is the function of ApoB100?
Binds to LDL receptors on cells, facilitating the uptake of LDL cholesterol. High levels can contribute to atherosclerosis.
What is the function of ApoC-2?
Activates lipoprotein lipase on the surface of blood vessels, which breaks down triglycerides in chylomicrons and VLDLs, releasing free fatty acids for cells to use.
What is the function of ApoE?
Binds to receptors on hepatocytes, triggering the uptake and clearance of chylomicron remnants and other lipoproteins. Essential for the normal breakdown of triglyceride-rich lipoproteins.
Most absorbed nutrients, including monosaccharides and amino acids, enter the blood capillaries of the villi and are transported to the liver via the ___________.
hepatic portal vein
Chylomicrons, carrying dietary lipids, are too large to enter blood capillaries and are instead transported into lymphatic vessels (________) within the villi. They eventually enter the bloodstream via the thoracic duct.
lacteals
How is vitamin B12 absorbed in the small intestine?
Vitamin B12 requires intrinsic factor (IF), a protein secreted by parietal cells in the stomach, for absorption.
In the small intestine, IF binds to B12, forming a complex that is recognized and absorbed by receptors in the ______ (the last part of the small intestine).
ileum
Calcium absorption occurs primarily in the duodenum and is regulated by ______________.
vitamin D
Calcium enters enterocytes through calcium channels (_______) and is transported across the cell by calbindin, a calcium-binding protein.
TRPV6
At high _________ calcium concentrations, some calcium is absorbed passively between cells.
luminal
Calcium is transported out of enterocytes into the blood by a ________ pump (PMCA1b) and a _______-_______ exchanger (NCX1).
calcium, sodium-calcium
Folate is also known as vitamin ___.
B9
Folate exists in food as __________ forms (PteGlu7) that need to be broken down to ____________ forms (PteGlu1) before absorption.
polyglutamate, monoglutamate
PteGlu1 is absorbed via a proton-coupled transporter (PCFT) in the _______.
jejunum
What are the consequences of impaired bile acid circulation?
Malabsorption of fats, Steatorrhea, Deficiencies in fat-soluble vitamins
What is steatorrhea?
Excess fat in the stool.
What are the potential causes of intestinal motility disorders?
Nerve damage, muscle dysfunction, hormonal imbalances, electrolyte disturbances, medications, stress and other psychological factors
What are some potential disease states associated with the small intestine?
Celiac disease, Crohn’s disease, Irritable bowel syndrome (IBS), Short bowel syndrome, Small intestinal bacterial overgrowth (SIBO), Lactose intolerance
The small intestine receives ______ from the stomach through the pyloric sphincter and delivers it to the large intestine through the _______- valve.
chyme, ileocecal
The small intestine receives digestive secretions from the _________ (enzymes and bicarbonate) and _______ (bile) that are essential for digestion and absorption.
pancreas, liver
What is the role of the ileocecal valve?
The ileocecal valve is a sphincter located at the junction of the small intestine (ileum) and the large intestine (cecum). It controls the flow of contents from the small intestine into the large intestine and prevents backflow from the colon into the ileum.
What are the potential consequences of rapid transit times through the small intestine?
Can lead to diarrhea and malabsorption as there is insufficient time for complete digestion and absorption of nutrients.
What are the potential consequences of slow transit times?
Can lead to constipation and increased bacterial fermentation of undigested food in the colon, causing bloating and gas.
What is the significance of the large surface area of the small intestine?
The large surface area, created by villi and microvilli, is crucial for maximizing nutrient absorption. It allows for a greater contact area between the chyme and the absorptive surface of the enterocytes.
How does the small intestine contribute to immune function?
GALT (gut-associated lymphoid tissue), Secretion of antimicrobial peptides, Production of IgA antibodies
What is the role of the unstirred layer in nutrient absorption?
The unstirred layer is a thin layer of fluid that lies adjacent to the intestinal epithelium. It can act as a barrier to diffusion, slowing down the movement of nutrients from the bulk chyme to the absorptive surface of the enterocytes. Segmentation contractions help to disrupt this layer, enhancing nutrient absorption.
How is water absorbed in the small intestine?
Water absorption in the small intestine occurs primarily through osmosis, following the movement of solutes like sodium and glucose. As solutes are absorbed into enterocytes, they create an osmotic gradient that draws water from the intestinal lumen into the cells and then into the blood.
How does the small intestine adapt to changes in nutrient intake?
Altering enzyme expression, Modifying transporter expression, Adjusting villi height and microvilli density
The pH of the small intestine is slightly __________ due to the bicarbonate secretions from the pancreas.
alkaline (around 7-8)
The process by which intestinal cells release fluid into the lumen is known as intestinal ______.
fluid secretion
The major driving force for intestinal fluid secretion is the movement of the ______ ion.
chloride
While the small intestine primarily functions in nutrient absorption, the colon focuses on the absorption of ______ and electrolytes.
water
The small intestine uses a mechanism involving SGLT1 to absorb glucose, while the colon relies on ______.
SCFA/HCO3- exchanger, MCT1, MCT4, SMCT1, SMCT2, non-ionic diffusion, paracellular pathway diffusion
The colon plays a crucial role in maintaining the body’s electrolyte balance by absorbing ______.
sodium
The human gut is home to a vast community of microorganisms known as the intestinal ______.
microbiome
Bacteria residing in the human gut that provide benefits to their host are called ______.
commensal bacteria
Commensal bacteria contribute to human health by producing essential vitamins like ______ and ______.
vitamin K, biotin
Commensal bacteria in the gut play a crucial role in breaking down complex carbohydrates into ______, which serve as an energy source for colonocytes.
short-chain fatty acids (SCFAs)
An imbalance in the composition of the gut microbiota is termed ______.
microbial dysbiosis
Microbial dysbiosis has been linked to several health problems, including ______, ______, and ______.
inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), obesity
The process of eliminating waste products from the body through the rectum and anus is known as ______.
defecation
The movement of fecal matter towards the rectum is facilitated by powerful contractions in the colon known as ______.
mass movement
The ______ anal sphincter, composed of smooth muscle, relaxes involuntarily during the defecation reflex.
internal
Distension of the ______ triggers the defecation reflex.
rectum
The ______ anal sphincter, made of skeletal muscle, is under voluntary control and can be consciously relaxed to allow defecation.
external
The ______ maneuver, which involves increasing abdominal pressure, aids in the expulsion of feces.
Valsalva
The large intestine is approximately ______ feet long.
8
The right colon is responsible for the ______ of ingested material.
absorption
The left colon functions in the ______ and elimination of waste products.
storage
The large intestine receives approximately ______ mL of chyme per day.
1500
The large intestine is characterized by pouches called ______ that help with the mixing and movement of fecal matter.
haustra
The inner lining of the colon contains numerous ______ that secrete mucus to lubricate and protect the intestinal wall.
goblet cells
The colon plays a crucial role in the absorption of ______ and ______, which are essential for maintaining electrolyte balance.
water, electrolytes
One of the primary functions of the colon is the absorption of ______, making the feces semi-solid.
water
The colon absorbs sodium ions through various mechanisms, including ______.
ENaC (Epithelial Sodium Channel)
Chloride ions are absorbed in the colon primarily through the ______ exchanger.
Cl-/HCO3-
The colon secretes ______ ions into the lumen to help neutralize the acidic environment created by bacterial fermentation.
bicarbonate
Short-chain fatty acids, produced by the fermentation of carbohydrates by gut bacteria, are a major source of ______ for colonocytes.
energy
True or False: There are three general categories for types of diarrhea.
True; Secretory, Mal-absorptive, Osmotic
The three most abundant SCFAs in the colon are ______, ______, and ______.
acetate, propionate, butyrate
SCFAs have various beneficial effects on the colon, including promoting ______ health and reducing ______.
epithelial, inflammation
Colonic bacteria play a crucial role in the breakdown of undigested carbohydrates, producing ______.
short-chain fatty acids
________ used a non-absorptive oil in cooking their chips in order to make them lower calories; this led to diarrhea and required disclaimers.
Pringles
Some beneficial bacteria in the colon, such as ______ and ______, contribute to gut health and immune function.
Lactobacillus, Bifidobacterium
Diarrhea, characterized by loose, watery stools, can be caused by an imbalance in the colon’s ______ and ______ processes.
absorptive, secretory
Secretory diarrhea occurs when the colon secretes excessive amounts of ______ into the lumen, often due to bacterial toxins or inflammation.
fluid
Malabsorptive diarrhea results from the impaired absorption of nutrients and water, commonly caused by conditions like ______.
celiac disease
Osmotic diarrhea is triggered by the presence of poorly absorbed substances in the colon, such as ______, drawing water into the lumen.
lactose
The invaginations in the lining of the colon responsible for fluid and electrolyte secretion are called ______.
crypts of Lieberkuhn
True or False: Cells in the colon start as secretory and later become absorptive.
True (differentiation)
The crypts of Lieberkuhn contain specialized cells that secrete ______ into the lumen, contributing to the fluidity of the intestinal contents.
mucus, water, electrolytes
The rectum is a muscular chamber that serves as a temporary storage site for ______.
feces
The anal canal, the final part of the large intestine, is controlled by two sphincters: the ______ anal sphincter and the ______ anal sphincter.
internal, external
DRA is expressed in ________ colon cells.
absorptive
.
Foods or food components with medicinal properties are known as ______.
nutriceuticals
______, a type of nutriceutical, are non-digestible fibers that promote the growth of beneficial bacteria in the gut.
Prebiotics
______, another type of nutriceutical, are live microorganisms that, when consumed, confer health benefits to the host.
Probiotics
Mast cells, immune cells residing in the gut, release inflammatory mediators upon activation, contributing to the development of conditions like ______.
inflammatory bowel disease (IBD), irritable bowel syndrome (IBS)
Bacterial infections, such as ______, can trigger mast cell activation in the gut, leading to inflammation and diarrhea.
Clostridioides difficile (C. difficile) [ aka c. diff ]
Intestinal gas, primarily produced by bacterial fermentation in the colon, consists mainly of ______, ______, ______, and ______.
nitrogen, oxygen, carbon dioxide, hydrogen, methane
___% of body’s serotonin is present in the colon.
98
True or False: Commensal bacteria can create neurotransmitters.
True
In the colon, short-chain fatty acids (SCFAs) are absorbed through several mechanisms, including the ______ exchanger.
SCFA/HCO3-
True or False: The uterus is a sterile environment.
False! Lactobacillus is actually involved in implantation
The colon absorbs SCFAs via MCT1 and MCT4 transporters, which are coupled to ______ ions.
H+
SMCT1 and SMCT2, responsible for SCFA uptake in the colon, are coupled to ______ ions.
Na+
SCFAs can also be absorbed in the colon through ______ diffusion and the ______ pathway.
non-ionic, paracellular
True or False: Vaginally births and C-sections lead to different microbiomes in the child.
True (C-sections are sterile); however, thought to be less important than previously thought as C-section babies will catch up
The drug Lubiprostone stimulates chloride secretion in the colon by activating ______ channels.
Cl-
The colon’s epithelial lining is continuously renewed through the process of cell ______ and ______.
migration, differentiation
The ______ zone in the colon crypts is where stem cells reside and proliferate.
proliferation
The ______ zone in the colon crypts is where cells undergo differentiation into specialized cell types.
transition
The enzyme ______, produced by colonic bacteria, converts bilirubin to urobilinogen, contributing to the characteristic color of feces.
β-glucuronidase
______ diarrhea occurs when the colon secretes excessive fluids into the lumen, often due to infections or inflammation.
Secretory
______ diarrhea results from impaired absorption of nutrients and water in the colon, commonly associated with conditions like celiac disease.
Malabsorptive
______ diarrhea occurs when poorly absorbed substances in the colon, such as lactose, draw water into the lumen, causing loose stools.
Osmotic
During defecation, the ______ maneuver involves closing the glottis and contracting abdominal muscles, increasing pressure to expel feces.
Valsalva
The colon also uses ____ and ____ transporters, coupled to H+ ions, to absorb SCFAs.
MCT1, MCT4
Sodium-coupled ____ and ____ transporters contribute to SCFA absorption in the colon.
SMCT1, SMCT2
The final stage in the life cycle of colon epithelial cells is ____, shedding them into the lumen.
Exfoliation
Psoriasis is associated with an increased ratio of ________ to actinobacteria.
firmicutes
Obesity is associated with a reduced ratio of _________ to firmicutes.
bacteroidetes
The rectum is approximately ____ cm long.
15
Best treatment (currently) for c. diff is ___________.
fetal microbial transplant
The _________ muscle loops around the rectum like a sling, pulling it forward to create a more acute angle between the rectum and the anal canal (the anorectal angle). During defecation, there is conscious relaxation of this muscle, which creates a more open anorectal angle and allows for a straighter passage through the anal canal.
puborectalis
The internal anal sphincter is innervated by _________ neurons.
enteric
The external anal sphincter is innervated by _________ neurons.
somatic efferent
Increased pressure in the rectum can either lead to ________ or defecation.
delay
What is ‘delay’ in the defecation pathway?
Continued contraction of the external anal sphincter and high pressure eventually trigger reverse peristalsis in the rectum, relieving the pressure and urge to defecate.
Rectal innervation originates in the _______ portion of the spinal cord.
saccral
The trace gases that make flatulence odorous are _________, __________, and _____________.
hydrogen sulfide, indole, skatole
True or False: IBS and IBD are the same.
False, IBS is non-specific and affects up to 15% of people; IBD is either ulcerative colitis or Crohn’s.
Microorganisms that can cause inflammatory diarrhea include _________ and _________.
salmonella, c. difficile
Microorganisms that can cause secretory diarrhea include _________, _________, and _________.
e. coli, cholera, influenza
In secretory diarrhea, influenza inhibits _________ receptors, while E. coli and cholera involve _______ receptors.
ENaC, CFTR
Bacterial enzymes that are involved in the digestive system include ______ which breaks down urea into ammonia, __________ which break down bilirubin into urobilinogen and stercobilins, and _________ which unconjugate bile acids.
urease, reductases, deconjugases
DRA, also known as SLC26A3, stands for ___________.
downregulated-in-adenoma
What is DRA?
DRA is a Cl-/HCO3-
Exchanger.
ENaC is to the distal colon as ________ is to the proximal colon; there are regional differences in ion transport in the colon.
NHE (sodium-hydrogen exchanger)
The inputs for MCT1 are SCFA and _____.
H+
The inputs for SMCT1 are SCFA and _______.
2 Na+
True or False: During Segmentation in the small intestine, there is no net movement.
True, basically just mixes chyme with intestinal secretions.
SGLT stands for ___________.
solute linked glucose transporter
Vitamin B12 is also known as _________.
cobalamin
In the pancreas, CCK acts on ______ cells while secretin acts on _______ cells.
acinar, ductal
What are the types of cells in the stomach, their locations, and what they secrete?
- Parietal cells, body, HCl & Intrinsic Factor
- Chief cells, body, Pepsinogen
- G cells, antrum, Gastrin
- Mucous cells, antrum, Mucus & Pepsinogen
True or False: Gastrin is released into the stomach.
False, gastrin is released into the circulation by G cells in the stomach (acts as hormone).
What are the sphincters in the stomach?
Lower Esophageal Sphincter (LES) [top of the stomach], Pyloric Sphincter [body of the stomach]
In the direct pathway of HCl production, ACh, gastrin, and histamine directly stimulate the _______ cells, triggering the secretion of protons into the lumen.
parietal
In the indirect pathway of HCl production, ACh and gastrin stimulate the ECL cell, resulting in the secretion of _________. This substance then acts on the parietal cell.
histamine
Histamine from the ECL cells acts at _____ receptors on the parietal cells.
H2
Chief cells in the stomach are stimulated by _______ and _______.
cAMP, Ca2+
True or False: During the vomiting reflex, respiration stops and abdominal pressure increases.
True, along with LES relaxation, contraction of diaphragm and ab muscles, and closure of the glottis.
