PHIS 206 1st EditionLecture 26Outline of Last Lecture I. GI Tract and HomeostasisII. AnatomyIII. Function of the Digestive SystemIV. Wall of the GI TubeV. Differences in the Gut WallVI. Hepatic Portal SystemVII. MotilityVIII. SecretionIX. DigestionX. AbsorptionXI. Regulation StimuliXII. Stimuli + ReceptorsOutline of Current Lecture I. Oral CavityII. Chewing + Chewing ReflexIII. Saliva + Salivary GlandsIV. Stimulation of salivary SecretionV. Control of Salivary SecretionVI. Pharynx and EsophagusVII. SwallowingVIII. Esophageal PhaseIX. Stomach + Stomach AnatomyX. Motility: FillingXI. Motility: Stomach PeristalsisThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XII. Gastric EmptyingXIII. VomitingXIV. Gastric Exocrine Secretions XV. Phases of Gastric SecretionCurrent LectureI. Oral Cavity-Anatomy palate: roof of mouth pharynx: swallowing; back of mouth-4 Processes Motility: chewing; beginning swallowing reflex Secretion: saliva Digestion: small amount occurs in mouth Absorption: NO absorption of nutrientso can absorb some drugs nitroglycerin tablets (tablets for heart pain)II. Chewing + Chewing Reflex-Reduce food size to swallow-Increase surface area of food-Mix food with saliva saliva helps wet food to create taste-Stimulate salivary secretion-Stimulate taste buds older people secrete less saliva, so they may eat less b/c they cannot taste the food-Break down cellulose from plant foods have to chew a lot so that you can maximize the amount of nutrients your body can take from the food otherwise, it will pass right through you! -Chewing Reflex pressure when food pushed to top of mouth jaw dropping: contracts when stretch receptors are activated III. Saliva + Salivary Glands: secretion of mouth-keep mouth moist for speech-swallowing easier through moisture-salivary amylase: begins digestions of carbohydrates-antibacterial effects (wash away debris)-saliva is a solvent; food is the solute, stimulate of taste buds will occur-saliva will aid in neutralizing acids-Salivary Glands sublingual gland: saliva more watery than submandibular gland glands secrete different versions of salivaIV. Stimulation of Salivary Secretion-Mechanical: actually chewing the food particle-Chemical: acidic chemicals (remember, saliva neutralizes the acids)-Neural: autonomic nervous system remember Pavlov’s dogs involuntary secretion of saliva when seeing the pice of meat Sympathetic and Parasympathetic Nervous Systems BOTH stimulate salivary secretionV. Control of Salivary Secretion-completely neuralVI. Pharynx and Esophagus-Motility: swallowing-Secretion: Mucus-Digestion: NONE-Absorption: NONEVII. Swallowing-Anatomical: oropharyngeal (mouth/pharynx) v. esopharyngeal (esophagus)-Functional: voluntary v. involuntaryVIII. Esophageal Phase-Skeletal muscle: above bolus (ONLY)-Food enters esophagus, the upper esophageal sphincter closes to prevent reflux-Peristaltic waves pushes food down esophagus-Wave opens gastroesophageal sphincter to allow entrance to the stomach-gastroesophageal sphincter closes again IX. Stomach + Stomach Anatomy-Stomach Anatomy fundus and above: most food storage antrum: thicker muscle; force greater-4 Processes Motility: filling/ receptive relaxation; peristalsis Secretion: HCl, enzymes, mucus Digestion: protein, carbohydrates Absorption: alcohol, aspirin, NO foodX. Motility: Filling-can change 20-fold in volume with little change in pressure-receptive relaxation: stomach relaxes when it receives food-discomfort when over 1 L of foodXI. Motility: Stomach Peristalsis- stomach activity: 3/min-antrum (thicker muscle): force is greaterXII. Gastric Emptying-Gastric Factors Volume of chyme Chyme fluidity-Duodenal Factors Presence of fat Presence of acid Hypertonicity DistentionXIII. Vomiting-Upper GI will be completely relaxed-Force from diaphragm and abdominal muscles-Touch back of throat, irritate, dizziness, emotionXIV. Gastric Exocrine Secretions - Goblet cells: Mucus (protective)- Chief cells: Pepsinogen - Parietal cells: Hydrochloric acid (HCl) Activates pepsinogen Antimicrobial action Breaks down connective tissue and muscle fibers From carbon dioxide in bloodXV. Phases of Gastric Secretion-Cephalic (seeing, smelling, tasting, chewing, and swallowing food) - Gastric (food reaches the stomach)-Intestinal (food reaches the
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