Textbooks Textbook of Medical Physiology Guyton and Hall
Textbooks • Textbook of Medical Physiology – Guyton and Hall 11 th Edition • Pathway to Pregnancy and Parturition – P. L Senger Second Edition
Evaluation • Midterm Examination – February 21 th 50% – 9: 30 am to 11: 20 Lect. Theatre “A” – Final Exam – April 29 th 50% – 13: 00 h Lect. Theatres “A”
FYI • A copy of each Power Point presentation is available in your CD and at: – http: //people. upei. ca/bate/html/physiologyii. html • A copy of the notes is also found there
SUGESTION • Use your time in class to pay attention instead of trying to copy what is in the screen. • YOU ALREADY HAVE ALL THAT INFORMATION WITH YOU !!!!! • Fill your notes upon reviewing the material in the web / CD.
GASTROINTESTINAL PHYSIOLOGY V BS 122 2013 LUIS A BATE
TOPICS • Overall digestive tract function and regulation – Regulation (motility) – Secretions – Digestion – Absorption – Fermentation
REGULATION OF GASTROINTESTINAL FUNCTION
Objectives • To understand the overall regulation of gastrointestinal function – Ingestion, mastication, deglutition, passage • To identify the main components (anatomy), substances (neurotransmitters, hormones) and processes (reflexes) involved
Food ingestion • Prehension • Mastication/Chewing • Deglutition/Swallowing F 1 -1
Prehension • Mechanisms vary greatly with species – Horses and sheep use the lips to manipulate and the teeth to rip – Cattle use the tongue to manipulate, the hard palate and lower teeth to rip – Carnivores use the incisors to cut and the canines to rip – Poultry uses the beak or bill F 1 -2
PREHENSION BY CATTLE • Use the tongue to manipulate food into mouth • Us mobile lower teeth and hard palate to press and tear F 1 -5
MASTICATION • Very important in herbivores • Not important in carnivores • Non existing in avian species F 1 -8
Mastication in hervivores • Reduce particle size – Increases surface area – Breaks cellulose membrane • Lubricate for swallowing • Mix with saliva • Exposed to digestive enzymes • Reduce excoriation of GIT F 1 -9
Deglutition • One voluntary initial stage – Movement of bolus to back of oral cavity • A pharyngeal stage (involuntary) – Passage from oral cavity to esophagus • Oesophageal stage (involuntary) – Passage of food into stomach F 1 -10
SOFT PALATE NASOPHARYNX GLOTTIS ESOPHAGUS EPIGLOTTIS TRACHEA F 1 -11
Respiration F 1 -12
Deglutition F 1 -13
http: //celiacdisease. upmc. com/Ima ges/Sub/Photo. Digestive. Tract. jpg
www. admani. com/Alliance. Equine/Mother. Natures. Design. htm
http: //personal. cobleskill. edu/tischda/feeds/sheepdig. htm
http: //www. ansi. okstate. edu/resourceroom/nutrition/poultrydigestivetract. htm
www. extension. umn. edu/distribution/livestocksystems/co mponents/DI 0469 -02. html
MESENTERY LONGITUDINAL MUSCLE MUSCULARIS MUCOSA MYENTERIC PLEXUS SEROSA MUCOSA MEISSNER’S PLEXUS CIRCULAR MUSCLE EPITHELIUM LUMEN SUBMUCOSAL GLANDS SUBMUCOSA F 1 -14
Smooth muscle • Arranged in bundles containing ~ 1000 fibres • Fibres connected electrically by gap junctions • Each bundle is separated by connective tissue but they contact each other at discrete points • Function as syncytium – Electric impulses travels in all directions • Some connections between F 1 -15
Electrical stimulation • Continuous slow intrinsic activity – Slow waves – Spikes • Slow waves (3 - 12/min) result by changes in resting membrane potential (range 5 to 15 m. V) (from 50 to -35 m. V) • Controls spike potential that initiates contraction F 1 -16
• • Spike potentials Last 10 -20 msec True action potential Triggered when more positive than -40 m. V The higher the slow waves rise, the more frequent spike potentials occur (1 -10 /sec) • Triggered by Ca++ influx through calciumsodium channels – Slower than sodium channels of nerve fibres F 1 -17
Membrane potential F 1 -18
Factors depolarizing membranes (membrane potential less negative) • Stretching • Acetylcholine • Parasympathetic stimulation –Mediated through acetylcholine • Specific gastrointestinal hormones F 1 -19
Factors hyperpolarizing membranes (membrane potential more negative) • Norepinephrine or epinephrine on fibre membrane • Sympathetic stimulation – Secreting norepinephrine F 1 -20
Enteric nervous system • Lies in gut wall • Extends from the esophagus to anus • Has as many neurones as the spinal cord • Made of two plexuses – Myenteric or Auerbach’s plexus • Situated between long. and circ. muscle layer – Submucosal or Meissner’s plexus • Situated in the submucosal layer F 1 -21
Enteric nervous system • Myenteric plexus controls gastrointestinal movement • Submucosal plexus controls secretions and blood flow • Innervated by sensory neurons from the epithelium • Connected to parasympathetic and sympathetic divisions F 1 -22
VILLUS LONGITUDINAL CIRCULAR SUBMUCOSA F 1 -23
Myenteric plexus • Controls motor activity along the gut – Increases tonic contraction or “tone” of gut wall – Increases intensity of rhythmical contractions – Increases rhythm – Increases velocity, thus more peristalsis • Has some inhibitory neurons – Secrete VIP • Controls sphincter activity F 1 -24
Submucosal plexus • Controls the function of small sections of the intestine • Signals from epithelium to SMP control – Local secretion – Local absorption – Local contraction • Regulates folding of gastrointestinal mucosa F 1 -25
Neurotransmitters • Acetylcholine – Mainly excites GI activity • Norepinephrine – Usually inhibits GI activity • Adenosine triphosphate (ATP) • Serotonin • Vasoactive intestinal polypeptide (VIP) • Somatostatin (SS) • Leu-enkephalin • Met-enkephalin • Bombesin F 1 -26
Gastrointestinal reflexes • Integrated completely within the enteric system and controls – Secretion, peristalsis, local mixing • Gut-sympathetic ganglia-gut – Gastrocolic reflex • Promotes colon evacuation – Enterogastric reflex • Prevents stomach motility and emptying – Colonoileal reflex • Inhibits ileal emptying F 1 -27
Cont… • Gut-spinal cord / brain-gut – Uses vagus nerve – From stomach and duodenum • Controls gastric motor and secretory activity – Pain reflexes • Inhibits gastrointestinal activity – Defecation reflex • Promotes colonic rectal and abdominal contraction F 1 -27
Endocrine control of motility • Cholecystokinin – Is secreted by I cells of the mucosa of the duodenum and jejunum – Responds to FA, monoglycerides in intestinal content – Increases contractility of the gallbladder • Secretes bile into the small intestine • Emulsifies fat – Inhibits stomach motility – Slows down transit F 1 -28
Cont… • Gastric inhibitory polypeptide – Is secreted by mucosal of upper intestine – Responds to fat and protein – Slows down stomach emptying – Allows for proper digestion of intestinal content F 1 -28
F 1 -29
F 1 -30
Functional movements of the GIT • Propulsive movements – Moves contents along the tract – Rate permitting digestion • Mixing movements – Mixes content • Facilitates enzymatic digestion – Increases exposure to epithelial wall • Facilitates digestion and absorption F 1 -31
Propulsive movements F 1 -32
Mixing movements (Segmentation) F 1 -33
Summary • Reviewed the overall regulation of gastrointestinal function – – Ingestion Mastication Deglutition Passage • Identify the main anatomical features of the GIT – Different layers – Enteric nervous system
Summary • Regulatory substances – Neurotransmitters – Hormones • Regulatory processes – Reflexes
© Luis A Bate 2013 Luis A Bate by Prepared for V BS 122 MOTILITY GASTROINTESTINAL PHYSIOLOGY ☺☻☺☻ Have a good day That’s all
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