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THE DIGESTIVE SYSTEM I
D. C. Mikulecky
Professor of Physiology
Virginia Commonwealth
University
FUNCTIONS OF THE
DIGESTIVE SYSTEM
MOTILITY
SECRETION
DIGESTION
ABSORPTION
THE DIGESTIVE TRACT
MOUTH AND PHARYNX
ESOPHAGUS
STOMACH
SMALL INTESTINE
LARGE INTESTINE
ANUS
THE DIGESTIVE TRACT
MUCOSA
LOGITUDINA
MUSCLE
SUBMUCOSAL
PLEXUS
CIRCULAR
MUSCLE
MYENTERIC
PLEXUS
LUMEN
EXTRINSIC
NERVES
INNERVATION OF THE G.I.
TRACT
PARASYMPATHETIC
SYMPATHETIC
INTRINSIC
PARASYMPATHETIC
VAGUS: DOWN TO TRANSVERSE
COLON. PREGANGLIONIC
CHOLINERGIC NEURONS
ORIGNINATE IN MEDULLA
PELVIC: BELOW THAT.
PREGANGLIONIC CHOLINERGIC
NEURONS ORIGNINATE IN SACRAL
S.C.
SYMPATHETIC
GANGLIA OUTSDE G. I. TRACT:
CELIAC, SUPERIOR AND INFERIOR
MESENTERIC
POSTGANGLIONIC ADRENERGIC
FIBERS INNERVATE MYENTERIC
AND SUBMUCOSAL PLEXUS
INTRINSIC INNERVATION
SUBMUCOSAL PLEXUS
MYENTERIC PLEXUS
DIFFERENT MEDIATORS: ACh, Nitric
Oxide, VIP, Enkephalins, Serotonin,
Substance P
G. I. PEPTIDES
HORMONES
NEUROCRINES
PARACRINES
G. I. HORMONES
GASTRIN
CHOLECYSTOKININ (CCK)
SECRETIN
GIP
MOTILIN
GASTRIN
ENDOCRINE CELLS IN PYLORIC STOMACH
STIMULATED BY PROTEIN IN STOMACH
STIMULATES SECRETION BY PARIETAL
AND CHIEF CELLS
STIMULATES ILEAL MOTILITY
RELAXES ILEOCECAL SPHINCTER
INDUCES COLONIC MASS MOVEMENTS
SECRETIN
ENDOCRINE CELLS IN DUODENAL MUCOSA
ACID IN DUODENAL LUMEN
INHIBITS GASTRIC EMPTYING
INHIBITS GASTRIC SECRETION
STIMULATES AQUEOUS BICARBONATE
SECRETION BY PANCREAS
STIMULATES BICARBONATE RICH BILE
SECRETION BYLIVER
CHOLECYSTOKININ
ENDOCRINE CELLS IN DUODENAL MUCOSA
FAT AND PROTEIN IN DUODENAL LUMEN
INHIBITS GASTRIC EMPTYING
INHIBITS GASTRIC SECRETION
CAUSES GALL BLADDER CONTRACTION
CAUSES RELAXATION OF THE SPHINCTER OF
ODDI
CONTRIBUTES TO SATIETY
GASRTIC INHIBITORY
PEPTIDE (GIP)
STRUCTURALLY RELATED TO
SECRETIN AND GLUCAGON
INHIBITS GASTRIC ACIS SECRETION
(PHARMACOLOGICAL DOSES)
STIMULATES INSULIN RELEASE
MOTILITY
THE DIGESTIVE TRACT IS
SURROUNDED BY LAYERS OF
SMOOTH MUSCLE
THESE MUSCLES ENABLE MIXING
AND PROPULSIVE MOVEMENT TO BE
CARRIED OUT BY THE DIGESTIVE
TRACT
SECRETION
DIGESTION REQUIRES THAT
ENZYMES BE SECRETED BY THE
PANCREAS AND OTHER ORGANS
MUCOUS SECRETIONS PROTECT THE
DIGESTIVE TRACT
ACID IS SECRETED IN THE STOMACH
THERE ARE OTHER SECRETIONS OF
IMPORTANCE
DIGESTION
BREAKING DOWN COMPLEX
FOODSTUFFS INTO ABSORBABLE
UNITS BY ENZYMES PRODUCED IN
THE DIGESTIVE SYSTEM
INVOLVES THE BREAKDOWN OF
CARBOHYDRATES, PROTEINS FATS,
AND OTHER FOODS
ABSORPTION
ALL OTHER FUNCTIONS SUPPORT
THIS ONE
THIS IS HOW WE OBTAIN THE
NECESSARY FUEL FOR OUR CELLS
ACCESSORY DIGESTIVE
ORGANS
SALIVARY GLANDS
EXOCRINE PANCREAS
BILLIARY SYSTEM: (LIVER AND
GALLBLADDER)
CONTROL OF DIGESTIVE
SYSTEM
External
Influences
Local
Influences
Receptors in Digestive Tract
Intrinsic
Nerve
Plexuses
Extrinsic Autonomic
Nerves
Smooth muscle
Exocrine Gland Cells
Endocrine Gland Cells
GI
Hormones
THE MOUTH
INGESTION OF FOOD
CHEWING AND SWALLOWING
SALIVARY SECRETION
CHEWING
CHEWING IS THE FIRST STEP IN THE
DIGESTIVE PROCESS
FOOD IS MIXED WITH SALIVA AND
BROKEN UP INTO SMALLER PIECES
TASTE BUDS ARE STIMULATED
SALIVARY SECRETION
SALIVARY AMYLASE: DIGESTS CARBOHYDRATE
MOISTENING AND LUBRICATING AGENT
ANTIBACTERIAL ACTION: LYSOZYME AND
RINSING
SOLVENT FOR TASTE STIMULI
SPEECH FACILITATION
ORAL HYGENE
BICARBONATE BUFFERS NEUTRALIZE ACIDS
Swallowing
A PROGRAMMED ALL-OR-NONE REFLEX
CHEWING AND MOVING THE BOLUS OF FOOD BACK IS
MANLY VOLUNTARY (STRIATED MUSCLE)
PRESSURE OF BOLUS ON PHARYNX TRIGGERS
INVOLUNTARY REFLEX (SMOOTH MUSCLE)
TONGUE PREVENTS FOOD FROM MOVING BACK
UVULA ELEVATED, SEALING NASAL PASSAGE
LARYNX ELEVATES AND CLOSURE OF GLOTTIS
RESPIRATION BRIEFLY INHIBITED
PHARYNGEAL MUSCLES FORCE BOLUS BACK
PERISTALTIC WAVES MOVE BOLUS THROUGH ESOPHAGUS
PERISTALSIS
RINGLIKE
CONTRACTION
SWEEPS DOWN
THE ESOPHAGUS
THE STOMACH
GASTROESOPHAGEAL
SPHINCTER
ESOPHAGUS
FUNDUS
BODY
OXYNTIC
MUCOSA
PYLORIC
ANTRUM
SPHINCTER
PYLORIC
GLAND
AREA
THE STOMACH
MIXING AND STORAGE ORGAN
HAS ITS OWN PACEMAKER: SETS
FREQUENCY OF RHYTHMIC PERISTALTIC
CONTRACTIONS
PERISTALSIS BECOMES STRONGER IN
ANTRUM
MOTILITY IS HIGHLY CONTROLLED
NO ABSORPTION OF FOOD, ONLY
ASPIRIN AND ALCOHOL
FACTORS INFLUENCING
GASTRIC MOTILITY
DISTENSION OF STOMACH:
INCREASES
FEEDBACK FROM THE SMALL
INTESTINE: DECREASES
CONTROL FROM CNS
GASTRIN: INCREASES
MIXING MOTIONS IN THE
STOMACH
PYLORIC SPHINCTER
CLOSED
PERISTALSIS
BEGINS
MIXING MOTIONS IN THE
STOMACH
PYLORIC SPHINCTER
CLOSED
PERISTALTIC WAVE
TRAVELS DOWNWARD
STOMACH EMPTYING
PYLORIC SPHINCTER
OPENS
CHYME
SQUIRTED
INTO
DUODENUM
PERISTALTIC WAV
TRAVELS DOWNWA
FACTORS CONTROLLING
STOMAC EMPTYING
GASTRIC MOTILITY
ENTEROGASTRIC REFLEX: VIA
INTRINSIC AND AUTONOMIC
NERVES
ENTEROGASTRONES: SECRETIN,
CHOLECYSTOKININ (CCK), GASTRIC
INHIBITORY PEPTIDE
FACTORS IN SMALL INTESTINE
CONTROLLING STOMAC EMPTYING
FAT
ACID
HYPERTONICITY
DISTENSION
GASTRIC SECRETIONS
MUCOUS: SURFACE CELLS
MUCOUS: MUCOUS NECK
CELLS
HYDROCHLORIC ACID:
PARIETAL CELLS
INTRINSIC FACTOR:
PARIETAL CELLS
PEPSINOGEN: CHIEF
CELLS
GASTRIN: ONLY IN THE
PYLORIC GLAND AREA
ACTIVATION OF PEPSIN
CHIEF
CELL
PEPSIN-OGEN
PEPSIN
HCL
PARIETAL
CELL
DIGESTS
PROTEIN
STIMULATION OF GASTRIC
SECRETION: CEPHALIC PHASE
SEEING, VAGUS
SMELLING,
TASTING
FOOD
INTRINSIC NERVES
PYLORIC AREA
GASTRIN
PARIETAL
& CHIEF
CELLS
INCREASED
GASTRIC
SECRETION
STIMULATION OF GASTRIC
SECRETION: GASTRIC PHASE
STIMULI
VAGUS
IN STOMACH:
PROTEIN,
DISTENSION,
CAFFEINE,
ALCOHOL
INTRINSIC NERVES
PYLORIC AREA
GASTRIN
PARIETAL
& CHIEF
CELLS
INCREASED
GASTRIC
SECRETION
THE GASTRIC MUCOSAL
BARRIER
PROTECTS THE CELLS FROM CONTENTS
OF STOMACH
LUMINAL MEMBRANES OF CELLS ARE
IMPERMEABLE TO PROTONS
CELLS ARE TIGHTLY ADJOINED
RAPID TURNOVER
IF BROKEN, PEPTIC ULCER MAY RESULT:
POSITIVE FEEDBACK INVOLVING
HISTAMINE
GASTRIN SECRETION
INHIBITION
ACID IN ANTRUM
REMOVAL OF PROTEIN AS STOMACH
EMPTIES