GI Lectures 1&2
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What is one of the major functions of the GI tract?

  • Oxygen exchange
  • Temperature regulation
  • Hormone synthesis
  • Nutrient absorption (correct)

    • The GI tract is responsible for

  • Removing carbon dioxide from the blood
  • Regulation of water and electrolyte balance (correct)
  • Producing bile acids only
  • Regulating body temperature

    • List the 6 major functions of the GI tract (Hint: IDARTT)

    Immunologic barrier, digestion of food into absorbable particles, absorption of food components and transport into the blood, regulation of water and electrolyte balance, transportation of food and thermoregulation

    Which of the following is NOT a function of the GI tract?

    <p>Synthesis of RBC</p> Signup and view all the answers

    Which species is known for its ability to digest cellulose due to microbial fermentation in the GI tract?

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

    Monogastric animals differ from ruminants in their

    <p>Stomach structure and digestive process</p> Signup and view all the answers

    The GI tract are concentric muscle ________ lined with an _________

    <p>The GI tract are concentric muscle cylinders lined with an epithelium</p> Signup and view all the answers

    What are the accessory organs of the GI tract?

    <p>Teeth, tongue, salivary glands, liver and pancreas</p> Signup and view all the answers

    What is prehension?

    <p>The process of getting food into the mouth</p> Signup and view all the answers

    Match the species differences in feeding behavior

    <p>Horses = Lips (when eating from manger) or incisors (when grazing) Cattle = tongue (wrap around forage) and incisors Goat and sheep = Tongue and lips Carnivores = Canines, incisors and forelimbs</p> Signup and view all the answers

    What is the first act of digestion?

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

    What are the actions of mastication?

    <p>It involves the action of the teeth, jaws, tongue and cheek</p> Signup and view all the answers

    Herbivores mastication movements are vertical and carnivores are horizontal, where they move against each other like scissors

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

    Match the functions of GI motility to correct description

    <p>Propel = Propel ingested feed from one location to the next Retain = Retain ingested feed at a given site for digestion, absorption or storage Break up = Break up food material physically and mix it with digestive secretions Circulate = Circulate ingested feed so that all portions come into contact with absorptive surfaces</p> Signup and view all the answers

    The term for swallowing is …

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

    The first MOTILITY pattern in the GI tract is

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

    Deglutition involves voluntary and involuntary stages and occurs after food has been ma

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

    The voluntary phase in Deglutition is considered the ____ phase

    <p>The voluntary phase in Deglutition is considered the oral phase</p> Signup and view all the answers

    When the food enters the pharynx what nerve endings are activated?

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

    What initiates the involuntary part of Deglutition?

    <p>When food enters the pharynx and activates sensory nerve endings</p> Signup and view all the answers

    The involuntary phase of Deglutition is known as the _________

    <p>The involuntary phase of Deglutition is known as the swallow reflex.</p> Signup and view all the answers

    Where does the involuntary phase occur within?

    <p>It occurs within the pharynx and esophagus</p> Signup and view all the answers

    During the pharyngeal phase of swallowing, which action prevents food from entering the nasal cavity?

    <p>The tongue pushes food into the pharynx</p> Signup and view all the answers

    What has to happen in order to prevent food from exiting via the nostrils?

    <p>The soft palate elvates, closing the pharyngeal opening of the nasopharynx</p> Signup and view all the answers

    When the tongue is pressed against the hard palate, closing off the oral opening, what is it preventing from happening?

    <p>Prevents food from exiting via the mouth</p> Signup and view all the answers

    When the epiglottis is moved backwards covering the entrance to the trachea preventing the movement of food into the respiratory system, what does this prevent?

    <p>Prevents aspiration</p> Signup and view all the answers

    Difficulty swallowing due to an obstruction or narrowing of the esophagus is known as

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

    A patient who experiences frequent choking or coughing during eating might be suffering from

    <p>Oropharyngeal dysphagia</p> Signup and view all the answers

    Which of the following nuclei of the hypothalamus is considered the satiety center?

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

    Which of the following nuclei of the hypothalamus is considered the hunger center?

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

    Which of the following are stimulatory neuropeptides? Select all that apply

    <p>Neuropeptide Y</p> Signup and view all the answers

    Which of the following is the neuropeptide that inhibits hunger and increases energy consumption?

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

    Which of the following hormones is primarily involved in regulating hunger?

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

    Ghrelin is a neuropeptide stimulatory hormone

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

    List all the inhibitory non-hypothalamus hormones

    <p>CCK, Peptide YY, Leptin and Insulin</p> Signup and view all the answers

    What are the two actions of leptin?

    <p>It’s secreted from fat cells and it acts to inhibit NPY release and activates MSH release</p> Signup and view all the answers

    Ghrelin is produced in the _________

    <p>Ghrelin is produced in the stomach</p> Signup and view all the answers

    Plasma Ghrelin ________ during fasting and ______ postprandially (postprandially = after eating)

    <p>Increases, decreases</p> Signup and view all the answers

    Which of following is not considered a major salivary gland amongst all species? (Basically according to hooper)

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

    Salivary glands can be classified into which of the following types?

    <p>Serous, mucous and seromucous</p> Signup and view all the answers

    Which of the following is NOT a characteristic of salivary glands?

    Signup and view all the answers

    List the small salivary glands (HINT 4)

    <p>Ventral jaw glands, palate/pharyngeal glands, lip glands, zygomatic glands</p> Signup and view all the answers

    What are the four PRIMARY functions of saliva?

    <p>Protection of oral mucosa and teeth, facilitation of Deglutition, Initiation of enzymatic carbohydrate digestion, pH regulation through bicarbonate secretion</p> Signup and view all the answers

    Humans and pigs are the only species that can produce amylase for initiation of enzymatic carbohydrate digestion

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

    What are the secondary functions of saliva?

    <p>Immunologic function, thermoregulation, and defense mechanisms</p> Signup and view all the answers

    Saliva consists of _____ and __________

    <p>Saliva consists of water and electrolytes</p> Signup and view all the answers

    The basic secretory unit of salivary glands is …..

    <p>The basic secretory units of salivary glands is acini</p> Signup and view all the answers

    Primary saliva is produced in the acini and the secondary saliva is produced in the ducts

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

    Which part of the nervous system plays a key role in regulation of saliva secretion?

    <p>Parasympathetic nervous system</p> Signup and view all the answers

    Stimulation of saliva secretion occurs via ________ and _______

    <p>Stimulation of saliva secretion occurs via innate reflex and conditioned through sight, smell or imagination of food</p> Signup and view all the answers

    Regulation of saliva secretion through the PNS acts through/on ___ receptors

    <p>M3</p> Signup and view all the answers

    The action of the PNS acting on the M3 receptors results in what?

    <p>It results in contraction of myoepithelial cells</p> Signup and view all the answers

    In regards to the stimulation of saliva secretion via the SNS, what receptors does it act on ?

    <p>Alpha 1</p> Signup and view all the answers

    What needs to occur to stimulate saliva secretion via the innate reflex?

    <p>It’s stimulated/triggered through contact with oral mucosa</p> Signup and view all the answers

    What are the “Big 5 hormones”?

    <p>Secretion, gastric , cck, GIP and Motilin</p> Signup and view all the answers

    Where is each one of the “big 5” hormones produced?

    <p>Secretion = Duodenum (primarily) and Jejunum (very minor) Gastrin = Produced in stomach (antrum) and duodenum CCK = Produced in duodenum, jejunum and ileum GIP/Motilin = Duodenum and jejunum</p> Signup and view all the answers

    Gastrin primarily functions to

    <p>Stimulate gastric acid secretion</p> Signup and view all the answers

    Secretin is released in response to:

    <p>Acidic chyme in the duodenum</p> Signup and view all the answers

    Cholecystokinin stimulates the:

    <p>Release of enzymes from the pancreas</p> Signup and view all the answers

    What is the action of each Big 5 GI hormone?

    <p>Secretin = Stimulates bicarbonate secretion and inhibits acid secretion Gastrin = Stimulates acid secretion GIP = Inhibits gastric secretion and stimulates insulin secretion Motilin = Induction of intestinal motility during fasting (MMC)</p> Signup and view all the answers

    What stimulates each hormone to be released?

    <p>Motilin = Acetylcholine GIP = Fats, glucose CCK = Fats and proteins Gastrin = Protein, high pH</p> Signup and view all the answers

    Match each glandular zone to what it produces

    <p>Cardia = Mucus production Fund us = HCL and enzymes production Pylorus = Mucus production Free bee = Free bee</p> Signup and view all the answers

    What is the primary function of the surface mucosal cells in the gastric mucosa?

    <p>To produce mucus that protects the stomach lining from acidic damage</p> Signup and view all the answers

    Gastric pits are invaginations in the stomach lining that …

    <p>Lead to deeper gastric glands responsible for secreting gastric juice</p> Signup and view all the answers

    Which of the following is the incorrect statement regarding gastric glands

    <p>Mucous neck cells serve as progenitor cells for parietal cells</p> Signup and view all the answers

    Parietal cells secrete (…) that is essential for Vit B12 absorption in the ileum

    <p>Parietal cells secrete intrinsic factor that is essential for Vit b12 absorption in the ileum</p> Signup and view all the answers

    All functional cell types of the gastric pit originate from stem cells located in the neck of the gland.

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

    What are the four enteroendocrine cell types?

    <p>G cells, D cells, I cells and ECL cells</p> Signup and view all the answers

    Enteroendocrine cells are named according to the hormone/sectrion they produce:

    <p>G cells = Gastrin I cells = CCK D cells = Somatostatin ECL cells = Histamine</p> Signup and view all the answers

    When parietal cells are stimulated to produce HCL, vesicles containing _____ are targeted to the (basalateral/apical) membrane

    <p>When parietal cells are stimulate to produce HCL, vesicles containing H+/K+ ATPase pumps are targeted to the apical membrane</p> Signup and view all the answers

    All the enteroendocrine cells are cells located within the stomach

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

    Autoproteolysis essentially means =

    <p>Self activation under the right conditions</p> Signup and view all the answers

    Pepsinogen hydrolyzes proteins

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

    In calves and labs, chief cells produce ____ instead of pepsinogen

    <p>In calves and labs, chief cells produce prochymosine instead of pepsinogen.</p> Signup and view all the answers

    What is the active form of prochymosine, and what is its function?

    <p>The active form is chymosine, and it hydrolyzes the milk protein</p> Signup and view all the answers

    Mucins are secreted by (exocytosis/endocytosis)

    <p>Mucins are secreted by exocytosis</p> Signup and view all the answers

    Surface mucosa cells do not live long, they regenerate every 3-5 days.

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

    HCL secretion is regulated at three levels. What are these 3 levels?

    <p>Neural, hormonal and paracrine</p> Signup and view all the answers

    The regulation of HCL at the three levels is mediated by

    <p>Neural = Acetylcholine Hormonal = Gastrin Paracrine = Histamine Free bee = Free bee</p> Signup and view all the answers

    What are the stimulatory substances for HCL secretion?

    <p>Gastrin, histamine and acetylcholine</p> Signup and view all the answers

    What inhibits HCL secretion?

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

    Gastric secretion is regulated at which of the following levels?

    <p>Cephalic, gastric and intestinal phase</p> Signup and view all the answers

    During the cephalic phase of gastric secretion, the stimulus is primarily

    <p>Sight, smell or thought of food</p> Signup and view all the answers

    The intestinal phase of gastric secretion is triggered by

    <p>Entry of chyme into duodenum</p> Signup and view all the answers

    Gastric enzyme secretion will be stimulated at what two levels?

    <p>Neural and hormonal levels</p> Signup and view all the answers

    neural stimulation of enzymatic secretion in the stomach is mediated by

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

    Hormonal stimulation of enzymatic secretion is mediated by : (select all that apply)

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

    NSAIDS can cause damage to the gastric mucosa by:

    <p>Reducing prostaglandin production</p> Signup and view all the answers

    Study Notes

    GI Tract: Function & Structure

    • One of the major functions of the GI tract is digestion.
    • The 6 major functions of the GI tract are: Ingestion, Digestion, Absorption, Transport, Secretion, Excretion (IDARTT)
    • Microbial fermentation in the GI tract allows for the digestion of cellulose, a trait prominent in ruminants.
    • Monogastric animals differ from ruminants in their single-chambered stomach structure compared to ruminants' multi-chambered stomach.
    • The GI tract consists of concentric muscle layers lined with an epithelium.
    • Accessory organs associated with the GI tract include the liver, gallbladder, pancreas, and salivary glands.
    • Prehension is the act of grasping food.
    • Mastication involves the chewing of food, crushing and grinding it, mixing it with saliva, and increasing surface area for enzyme action.

    GI Motility

    • The first act of digestion is prehension, followed by mastication.
    • Deglutition is the swallowing of food.
    • The first motility pattern in the GI tract is deglutition.
    • Deglutition involves voluntary and involuntary stages and occurs after food has been masticated.
    • The voluntary phase in Deglutition is considered the oral phase.
    • When food enters the pharynx, nerve endings are activated.
    • The involuntary part of Deglutition is initiated by the activation of receptors in the pharynx.
    • The involuntary phase of Deglutition is known as the pharyngeal phase.
    • The involuntary phase occurs within the pharynx and esophagus.
    • During the pharyngeal phase, the soft palate elevates to prevent food from entering the nasal cavity.
    • The tongue presses against the hard palate, closing off the oral cavity.
    • Epiglottis moves backwards, covering the entrance to the trachea and preventing food from entering the respiratory system.
    • Dysphagia is difficulty swallowing due to an obstruction or narrowing of the esophagus.
    • Choking or coughing during eating might be a symptom of dysphagia.

    Regulation of Hunger & Satiety

    • The hypothalamus is the brain region responsible for regulating hunger and satiety.
    • The arcuate nucleus of the hypothalamus is considered the satiety center.
    • The lateral hypothalamus is considered the hunger center.
    • Stimulatory neuropeptides include ghrelin, neuropeptide Y, and agouti-related protein (AgRP).
    • Leptin is the neuropeptide that inhibits hunger and increases energy consumption.
    • Ghrelin is a neuropeptide stimulatory hormone.
    • Inhibitory non-hypothalamus hormones include insulin, CCK, and PYY.
    • Leptin acts to decrease appetite and increase energy expenditure.
    • Ghrelin is produced in the stomach.
    • Plasma Ghrelin levels increase during fasting and decrease postprandially.

    Salivary Glands & Saliva

    • Parotid, submandibular, and sublingual glands are the major salivary glands.
    • Salivary glands can be classified into serous, mucous, and mixed types.
    • Salivary glands secrete saliva.
    • Small salivary glands include buccal, labial, lingual, and palatine glands.
    • The four primary functions of saliva are lubrication, moistening, dissolving, and enzyme digestion.
    • Secondary functions of saliva include buffering, antibacterial action, and taste perception.
    • Saliva mainly consists of water and electrolytes.
    • The basic secretory unit of salivary glands is the acini.
    • The PNS plays a key role in regulating saliva secretion.
    • Stimulation of saliva secretion occurs via the PNS and SNS.
    • PNS acts on M3 receptors.
    • The PNS action on M3 receptors results in increased secretion.
    • The SNS acts on alpha receptors.
    • To stimulate saliva secretion via the innate reflex, food needs to be placed in the mouth.

    Gastrointestinal Hormones

    • Gastrin, Cholecystokinin, Secretin, Motilin, and Ghrelin are the "Big 5 hormones".
    • Gastrin is produced in the gastric mucosa.
    • Cholecystokinin is produced in the duodenum and jejunum.
    • Secretin is produced in the duodenum and jejunum.
    • Motilin is produced in the duodenum and jejunum.
    • Ghrelin is produced in the stomach.
    • Gastrin primarily functions to stimulate the stomach.
    • Secretin is released in response to acid entering the duodenum.
    • Cholecystokinin stimulates the gallbladder to contract.
    • Motilin is involved in intestinal motility.
    • Gastrin stimulates gastric acid and enzyme secretion, gastric motility, and growth of the gastric mucosa and gastric emptying.
    • Secretin neutralizes intestinal pH, inhibits gastric emptying, and stimulates pancreatic bicarbonate secretion.
    • CCK stimulates pancreatic enzyme secretion, bile secretion, gastric emptying, and satiety.
    • Motilin stimulates gastric emptying and intestinal motility.
    • Ghrelin stimulates appetite and growth hormone release.

    Gastric Mucosa

    • The gastric mucosa is responsible for acid and enzyme secretion.
    • Surface mucosal cells in the gastric mucosa secrete mucus.
    • Gastric pits are invaginations in the stomach lining.
    • Parietal cells secrete HCl and intrinsic factor, essential for Vitamin B12 absorption.
    • Chief cells secrete pepsinogen, a zymogen (inactive form) of pepsin.
    • Enteroendocrine cells are named according to the hormone/secretion they produce.
    • Enteroendocrine cells include G cells, D cells, ECL cells, and X/A-like cells.
    • Parietal cells release vesicles containing H+ and K+ ATPase to the apical membrane upon stimulation.
    • Autoproteolysis is when a protein cleaves itself.
    • Pepsinogen is activated by HCL, converting it to pepsin.
    • Prochymosine is a zymogen produced by chief cells in calves and labs, and it functions as a milk protein digesting enzyme.
    • Mucins are secreted by exocytosis.
    • HCL secretion is regulated at three levels: cephalic, gastric, and intestinal.
    • Gastrin is the primary mediator of HCL secretion.
    • Stimulatory substances for HCL secretion include gastrin, histamine, and acetylcholine.
    • Inhibitory substances for HCL secretion include secretin, somatostatin, and prostaglandins.
    • Gastric secretion is regulated at the cephalic, gastric, and intestinal levels.
    • The cephalic phase of gastric secretion is triggered by sight, smell, taste, and thought of food.
    • The intestinal phase is triggered by food entering the duodenum.
    • Gastric enzyme secretion is stimulated at the neural and hormonal levels.
    • Neural stimulation of enzymatic secretion is mediated by vagus nerve.
    • Hormonal stimulation of enzymatic secretion is mediated by gastrin and CCK.
    • NSAIDS can damage the gastric mucosa by inhibiting prostaglandin synthesis.

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