The Digestive System A. Digestive processes B. Organization 1. General histology of the GI tract 1....
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The Digestive SystemThe Digestive SystemA. Digestive processesA. Digestive processesB. OrganizationB. Organization 1. General histology of the GI tract1. General histology of the GI tract a. Mucosaa. Mucosa b. Submucosab. Submucosa c. Muscularisc. Muscularis d. Serosad. Serosa 2. Peritoneum2. PeritoneumC. Mouth (oral cavity)C. Mouth (oral cavity) 1. Tongue1. Tongue 2. Salivary glands2. Salivary glands a. Composition of salivaa. Composition of saliva b. Secretion of salivab. Secretion of saliva 3. Physiology of digestion in the mouth3. Physiology of digestion in the mouth a. Mechanical digestiona. Mechanical digestion b. Chemical digestionb. Chemical digestion 4. Physiology of deglutition4. Physiology of deglutitionD. EsophagusD. Esophagus 1. Histology1. Histology 2. Physiology2. PhysiologyE. StomachE. Stomach 1. Anatomy and Histology1. Anatomy and Histology 2. Physiology of digestion in the stomach2. Physiology of digestion in the stomach a. Mechanical digestiona. Mechanical digestion b. Chemical digestionb. Chemical digestion 3. Regulation of gastric secretion and motility3. Regulation of gastric secretion and motility a. Cephalic phasea. Cephalic phase b. Gastric phaseb. Gastric phase c. Intestinal phasec. Intestinal phase 4. Regulation of gastric emptying4. Regulation of gastric emptying 5. Absorption5. Absorption
F. PancreasF. Pancreas 1. Anatomy and Histology1. Anatomy and Histology 2. Pancreatic juice2. Pancreatic juice 3. Regulation of pancreatic secretions3. Regulation of pancreatic secretionsG. LiverG. Liver 1. Anatomy and Histology1. Anatomy and Histology 2. Blood supply2. Blood supply 3. Bile3. Bile 4. Regulation of bile secretion4. Regulation of bile secretion 5. Physiology of the liver5. Physiology of the liverH. GallbladderH. Gallbladder 1. Histology1. Histology 2. Physiology2. PhysiologyI. Small intestineI. Small intestine 1. Anatomy and Histology1. Anatomy and Histology 2. Intestinal juice and brush border enzymes2. Intestinal juice and brush border enzymes 3. Physiology of digestion in the small intestine 3. Physiology of digestion in the small intestine a. Mechanical digestiona. Mechanical digestion b. Chemical digestionb. Chemical digestion 4. Regulation of intestinal secretion and motility4. Regulation of intestinal secretion and motility 5. Physiology of absorption5. Physiology of absorptionJ. Large intestineJ. Large intestine 1. Anatomy and Histology1. Anatomy and Histology 2. Physiology of digestion in the large intestine 2. Physiology of digestion in the large intestine a. Mechanical digestiona. Mechanical digestion b. Chemical digestionb. Chemical digestion 3. Absorption and feces formation3. Absorption and feces formation 4. Physiology of defecation4. Physiology of defecation
Food is vital to life becauseFood is vital to life because
1. provides energy1. provides energy
2. provides building blocks2. provides building blocks
Why do we have a digestive system?Why do we have a digestive system?
Five Basic Digestive ProcessesFive Basic Digestive Processes
1. ingestion1. ingestion
2. movement of food (peristalsis)2. movement of food (peristalsis)
3. digestion3. digestion
4. absorption4. absorption
5. defecation5. defecation
Two Types of DigestionTwo Types of Digestion
1. mechanical1. mechanical
2. chemical2. chemical
Digestive System OverviewDigestive System Overview
OrganizationOrganization
1. gastrointestinal tract1. gastrointestinal tractmouthpharynxesophagusstomachsmall intestinelarge intestine
2. accessory organs2. accessory organsTeethTongueSalivary glandsLivergallbladderpancreas
General HistologyGeneral Histology
1. mucosa1. mucosa a. epitheliuma. epithelium b. lamina propriab. lamina propria c. muscularis mucosaec. muscularis mucosae2. submucosa2. submucosa (submucosal plexus)(submucosal plexus)3. muscularis3. muscularis a. inner circulara. inner circular b. outer longitudinalb. outer longitudinal c. myenteric plexusc. myenteric plexus4. serosa 4. serosa
(visceral peritoneum)(visceral peritoneum)
PeritoneumPeritoneum1. parietal 1. parietal vsvs visceral visceral
2. peritoneal cavity2. peritoneal cavity
3. mesentery3. mesentery
4. mesocolon4. mesocolon
Mouth (oral cavity)Mouth (oral cavity)
1. boundaries1. boundaries
2. hard palate 2. hard palate vsvs soft palate soft palate
3. palatoglossal arches3. palatoglossal arches
4. palatopharyngeal arches4. palatopharyngeal arches
5. epithelium5. epithelium
6. vestibule6. vestibule
7. fauces7. fauces
fauces
TongueTongue1. intrinsic muscles1. intrinsic muscles
2. extrinsic muscles2. extrinsic muscles
3. frenulum3. frenulum
4. bolus4. bolus
5. hypoglossal nerve5. hypoglossal nerve
Salivary GlandsSalivary Glands1. buccal, lingual, labial1. buccal, lingual, labial
2. paired glands2. paired glands
a. parotida. parotid
b. submandibularb. submandibular
c. sublingualc. sublingual
Saliva is composed of 99.5% water, used to Saliva is composed of 99.5% water, used to dissolve foods, and 0.5% solutes, including:dissolve foods, and 0.5% solutes, including:
1. salivary amylase1. salivary amylase
2. ions (Na, K, Cl, HCO3, HPO4)2. ions (Na, K, Cl, HCO3, HPO4)
3. mucous3. mucous
4. lysozyme 4. lysozyme
SalivationSalivation is controlled by the is controlled by the parasympathetic nervous system parasympathetic nervous system
(cranial nerves VII and IX).(cranial nerves VII and IX).
Three types of stimuli may initiate Three types of stimuli may initiate salivation:salivation:
1. psychic1. psychic
2. chemical2. chemical
3. tactile3. tactile
Physiology of Digestion in MouthPhysiology of Digestion in Mouth
1. mechanical = mastication1. mechanical = mastication
2. chemical2. chemical
salivary amylasesalivary amylase
starch -----------------------> maltosestarch -----------------------> maltose
(glu+glu)(glu+glu)
Swallowing (Deglutition)Swallowing (Deglutition)
1. voluntary (buccal) stage1. voluntary (buccal) stage
(cranial nerves V, VII, XII)(cranial nerves V, VII, XII)
2. pharyngeal-stage2. pharyngeal-stage
(deglutition reflex)(deglutition reflex)
(cranial nerves IX, X, XI)(cranial nerves IX, X, XI)
3. esophageal stage3. esophageal stage
EsophagusEsophagus1. gross anatomy1. gross anatomy
2. esophageal hiatus2. esophageal hiatus
3. mucosa3. mucosa
4. muscularis4. muscularis
5. sphincters5. sphincters
a. uppera. upper
b. lower (gastroesophageal)b. lower (gastroesophageal)
lumen
mucosasubmucosa
muscularis externa
adventitia
stratified squamous epithelium
IC
OL
Stomach AnatomyStomach Anatomy
1. location1. location
2. divisions2. divisions
3. pyloric sphincter3. pyloric sphincter
4. curvatures4. curvatures
5. rugae5. rugae
Stomach HistologyStomach Histology1. simple columnar epithelium1. simple columnar epithelium2. gastric glands2. gastric glands a. chief cellsa. chief cells (pepsinogen, gastric lipase)(pepsinogen, gastric lipase) b. parietal cellsb. parietal cells (HCl, intrinsic factor)(HCl, intrinsic factor) c. mucous neck cells (mucous)c. mucous neck cells (mucous) d. G cells (gastrin)d. G cells (gastrin)3. muscularis3. muscularis
serosa has been removed
inner oblique fibers
middle circular fibers
outer longitudinal fibers
Mechanical Digestion in the Mechanical Digestion in the StomachStomach
1. regular gentle peristaltic waves1. regular gentle peristaltic waves
2. mixing waves producing chyme2. mixing waves producing chyme
Chemical Digestion in the StomachChemical Digestion in the Stomach
1.1. pepsinogen pepsin (pH 1 - 3)pepsinogen pepsin (pH 1 - 3)
proteins peptidesproteins peptides
2. gastric lipase2. gastric lipase
3. rennin (infant only)3. rennin (infant only)
HCl
Mode of Hydrochloric Acid Mode of Hydrochloric Acid SecretionSecretion
Pepsid ACPepsid AC
ZantacZantac
Three Phases of Stomach ControlThree Phases of Stomach Control
Cephalic PhaseCephalic Phase
Gastric PhaseGastric Phase
Intestinal PhaseIntestinal Phase
Stomach Regulation-First PhaseStomach Regulation-First Phase1. cephalic phase1. cephalic phase
a. psychic stimulia. psychic stimuli
b. vagus nerveb. vagus nerve
c. increased motility and secretionc. increased motility and secretion
Stomach Regulation-Cephalic Phase
Cephalic phase
thought and anticipation of food
parasympathetic output via the vagus nerve (X)
stimulation of stomach’s enteric nervous system
PSYCHIC STIMULI
sight, taste, smell of food sound of food preparation
increased gastric secretion + increased gastric motility
Stomach Regulation-Second PhaseStomach Regulation-Second Phase2. gastric phase2. gastric phase
a. stretch receptors and a. stretch receptors and
chemoreceptorschemoreceptors
b. local parasympathetic responseb. local parasympathetic response
c. gastrinc. gastrin
Stomach Regulation-Gastric Phase
increased stretch of stomach wall
direct stimulation of stomach’s enteric nervous system
increased gastric secretion + increased gastric motility
food enters the stomach
input to brainstem
parasympathetic output via the vagus nerve (X)
increased gastrin secretion
increased pH stimulates chemoreceptors
Positive Feedback Control of Positive Feedback Control of Gastric SecretionGastric Secretion
Negative Feedback of the Gastric Phase
CONTROLLED CONDITION
RECEPTORChemoreceptors and stretch receptors
increased pH and stretch of stomach wall, and generate nerve impulses that pass to
the control centers
CONTROL CENTER
Enteric nervous system and medullary neurons generate parasympathetic impulses that pass to the effectors
EFFECTORSParietal cells of the gastric mucosa
secrete HCl and the muscularis contracts more vigorously (increased frequency and
strength of mixing waves)
RETURN TO HOMEOSTASISIn response, there is increased acidity in stomach chyme and the mixing waves
begin emptying the stomach. An empty stomach is a return to homeostasis.
Food entering stomach disrupts homeostasis by causing an increase in
gastric juice pH AND stretch (distention) of stomach wall
Stomach Regulation-Third PhaseStomach Regulation-Third Phase3. intestinal phase3. intestinal phase a. stretch receptors and a. stretch receptors and chemoreceptorschemoreceptors b. enterogastric reflexb. enterogastric reflex c. hormonesc. hormones (1) gastrin (+)(1) gastrin (+) (2) cholecystokinin (CCK) (-)(2) cholecystokinin (CCK) (-) (3) secretin (-)(3) secretin (-) (4) gastric inhibitory peptide (4) gastric inhibitory peptide (GIP) (-)(GIP) (-)
Stomach Regulation-Intestinal Phase
increased stretch of duodenal wall
direct stimulation of duodenum’s enteric
nervous system
chyme enters the duodenum
decreased stomach activity
cholecystokininsecretin
increased enteric endocrine cell activity
secretion ofenterogastric
reflex
input to brainstem
increased sympathetic output to stomach
increased stomach activity
enteric gastrindecreased parasympathetic
output from the vagus nerve (X) to stomach
NET EFFECTgastric inhibition
inhibits
inhibits inhibits
Gastric Emptying
distention of stomach
STIMULATION OF GASTRIC EMPTYING
increased gastrin secretion increased vagal activity
contraction of gastroesophageal sphincterrelaxation of pyloric sphincter
increased rate of mixing wavesincreased gastric secretion
increased rate of emptying
partially digested proteinsalcoholcaffeine
distention of duodenum
INHIBITION OF GASTRIC EMPTYING
enterogastric reflex
decreased rate of emptying
partially digested proteins, fatty acids,
glucose in duodenum
secretion of cholecystokinin and
secretin
contraction of pyloric sphincterdecreased rate of mixing waves
decreased gastric secretion
Stomach AbsorptionStomach Absorption
Accomplishments of digestion to this point in the GI tractAccomplishments of digestion to this point in the GI tractstarch maltose by salivary amylase (action stops in stomach)proteins partially digested proteins (action of pepsin)lipids partially digested fats (action of lingual and gastric lipase)creation of chyme from food, drink, saliva, and gastric juice
Stomach Absorption
1. water1. water2. electrolytes2. electrolytes3. certain drugs (aspirin)3. certain drugs (aspirin)4. alcohol4. alcohol
Accessory Organs of DigestionAccessory Organs of Digestion
PancreasPancreas
Liver Liver
GallbladderGallbladder
PancreasPancreas1. gross anatomy1. gross anatomy
2. main pancreatic duct2. main pancreatic duct
3. hepatopancreatic ampulla3. hepatopancreatic ampulla
4. accessory pancreatic duct4. accessory pancreatic duct
5. 99% exocrine5. 99% exocrine
6. 1% endocrine6. 1% endocrine
Pancreatic JuicePancreatic Juice1. sodium bicarbonate (NaHCO3)1. sodium bicarbonate (NaHCO3)
2. pancreatic amylase2. pancreatic amylase
3. pancreatic lipase and cholesterol esterase3. pancreatic lipase and cholesterol esterase
4. nucleases -- DNAse and RNAse4. nucleases -- DNAse and RNAse
5. protein-digesting enzymes5. protein-digesting enzymes
a. trypsinogen (inactive)a. trypsinogen (inactive)
b. chymotrypsinogen (inactive)b. chymotrypsinogen (inactive)
c. procarboxypeptidase (inactive)c. procarboxypeptidase (inactive)
Pancreatic Regulation-Neural Pancreatic Regulation-Neural Control and Endocrine ControlControl and Endocrine Control
1. vagus nerve1. vagus nerve
2. CCK = enzymes2. CCK = enzymes
3. secretin = NaHCO33. secretin = NaHCO3
Pancreatic Regulation
acid chyme in duodenum
ENDOCRINE CONTROL
enteroendocrine cells stimulated
increased secretion of bicarbonate ions
increased secretin increased cholecystokinin
increased secretion of enzymes
NEURAL CONTROL
psychic stimuli stretch of stomach
increased parasympathetic impulses via vagus nerve
increased pancreatic secretion
Liver AnatomyLiver Anatomy1. location1. location
2. lobes2. lobes
3. falciform ligament3. falciform ligament
4. bile4. bile
5. bile canaliculi5. bile canaliculi
6. ducts6. ducts
Liver HistologyLiver Histology1. lobule1. lobule
2. hepatocytes2. hepatocytes
3. central vein3. central vein
4. sinusoids4. sinusoids
5. flow of bile5. flow of bile
6. blood flow6. blood flow
7. portal triad7. portal triad
BileBile
1. is a detergent1. is a detergent
2. emulsification of fats2. emulsification of fats
Produced continuously at slow rate
Secretion increased in response to:
vagus nerve – psychic and gastric phases
secretin – from the duodenum during intestinal phase
Physiology of the LiverPhysiology of the Liver
1. carbohydrate metabolism 4. detoxification1. carbohydrate metabolism 4. detoxification a. glycogenesis 5. synthesis and a. glycogenesis 5. synthesis and
excretion of bile excretion of bile b. glycogenolysis 6. storageb. glycogenolysis 6. storage c. gluconeogenesis 7. phagocytosis of c. gluconeogenesis 7. phagocytosis of
RBCs RBCs2. lipid metabolism 8. activation of vitamin 2. lipid metabolism 8. activation of vitamin D D 3. protein metabolism3. protein metabolism a. deamination (-NH2)a. deamination (-NH2) b. urea formationb. urea formation c. plasma protein productionc. plasma protein production
GallbladderGallbladder
1. anatomy1. anatomy2. rugae2. rugae3. cystic duct3. cystic duct4. stores/concentrates bile4. stores/concentrates bile5. sphincter of Oddi5. sphincter of Oddi6. CCK6. CCK
Biliary TractBiliary Tractcommon hepatic duct +cystic duct = common bile duct +main pancreatic duct = ampulla of Vatersphincter of Oddi
Regulation of Bile SecretionRegulation of Bile Secretion
acid chyme in duodenum
REGULATION OF BILE SECRETION
enteroendocrine cells stimulated
cholecystokinin secretion
gallbladder contraction
relaxation of sphincter of Oddi
release of bile into duodenum
Small Intestine AnatomySmall Intestine Anatomy
1. 21 ft. x 1 in.1. 21 ft. x 1 in.2. duodenum (10 in.) 2. duodenum (10 in.) -- retroperitoneal-- retroperitoneal3. jejunum (8 ft.)3. jejunum (8 ft.) -- mesentery-- mesentery4. ileum (12 ft.)4. ileum (12 ft.) -- mesentery-- mesentery5. ileocecal sphincter5. ileocecal sphincter
Small Intestine HistologySmall Intestine Histology
1. intestinal glands1. intestinal glands
2. plicae circulares2. plicae circulares
3. villi3. villi
4. microvilli4. microvilli
5. Peyer's patches5. Peyer's patches
Intestinal Juice and Brush Intestinal Juice and Brush Border EnzymesBorder Enzymes
MaltaseMaltase
LactaseLactase
PeptidasesPeptidases
DextrinasesDextrinases
NucleosidasesNucleosidases
PhosphatasesPhosphatases
Small Intestine-Mechanical Small Intestine-Mechanical DigestionDigestion
1. segmentation1. segmentation
2. peristalsis2. peristalsis
Review of Chemical Digestion of Carbohydrates
STARCH SUCROSE LACTOSE
mouth
stomach
small intestine
salivary amylase
(absorbed into blood of villus)
MALTOSE
pancreaticamylase
brush border maltase
glucose + glucose
SUCROSE
glucose + fructose(absorbed into blood of villus)
brush border sucrase
LACTOSE
glucose + galactose(absorbed into blood of villus)
brush border lactase
Review the Chemical Digestion of ProteinsReview the Chemical Digestion of Proteins
Review the Chemical Digestion of LipidsReview the Chemical Digestion of Lipids
Regulation of small intestinal Regulation of small intestinal secretion and motilitysecretion and motility
1. local reflexes1. local reflexes
2. parasympathetic reflexes 2. parasympathetic reflexes
(vagus nerve)(vagus nerve)
3. gastrin3. gastrin
Regulation of the Small Intestine
psychic stimuli stretch of stomach
increased parasympathetic impulses via vagus nerve
increased small intestinal motility secretion
+ relaxation of ileocecal sphincter
gastroileal reflex
chemoreceptors in stomach
increased gastrin secretion
stretch of small intestine
increased enteric nervous system activity
GASTRIC PHASE
Small Intestine AbsorptionSmall Intestine Absorption
1. monosaccharides1. monosaccharides2. 2. amino acidsamino acids
hepatic portal bloodhepatic portal blood liver inferior vena cava general circulation
3. fats 3. fats triglyceridestriglycerides chylomicronschylomicrons lymph lacteals intestinal trunk thoracic duct general circulation
4. water4. water
blood capillary
lactealwith
chylomicrons
monosaccharidesamino acids
superior mesenteric vein
hepatic portal vein
thoracic duct
inferiorvena cava
lymphatic vessel
Water absorptionWater absorption
GI tract fluids/24 hoursGI tract fluids/24 hours
saliva = 1 L small intestine =saliva = 1 L small intestine =ingested liquids = 2L 8 Lingested liquids = 2L 8 Lgastric juice = 2 L large intestine =gastric juice = 2 L large intestine =bile = 1L 0.9 Lbile = 1L 0.9 Lpancreatic juice = 2 Lpancreatic juice = 2 Lintestinal juice = 1Lintestinal juice = 1Ltotal = 9 Ltotal = 9 L
0.1 L0.1 L
Ingested or secreted into GI tract Absorbed into blood
Excretedin feces
Large Intestine AnatomyLarge Intestine Anatomy
1. 5 ft. x 2.5 in.1. 5 ft. x 2.5 in.2. cecum with appendix2. cecum with appendix3. colon3. colon a. ascendinga. ascending b. transverseb. transverse c. descendingc. descending d. sigmoidd. sigmoid4. rectum4. rectum
Large Intestine Anatomy Con’tLarge Intestine Anatomy Con’t5. haustra5. haustra
6. taenia coli6. taenia coli
7. epiploic appendages7. epiploic appendages
8. anal canal8. anal canal
9. anus9. anus
10. internal anal sphincter10. internal anal sphincter
11. external anal sphincter11. external anal sphincter
Large Intestine HistologyLarge Intestine Histology
1. no plicae circulares1. no plicae circulares
2. no villi2. no villi
3. goblet cells3. goblet cells
no villi
intestinal gland
lumen
goblet cells
muscularis mucosae
submucosa
Mechanical Digestion in the Mechanical Digestion in the Large IntestineLarge Intestine
1. haustral churning1. haustral churning
2. mass peristalsis 2. mass peristalsis
(gastrocolic reflex)(gastrocolic reflex)
3. peristalsis3. peristalsis
Chemical digestion in the Chemical digestion in the large intestinelarge intestine
1. bacteria fermentation1. bacteria fermentation
2. bacteria secrete vitamin K and some 2. bacteria secrete vitamin K and some
B complex vitaminsB complex vitamins
Large Intestine AbsorptionLarge Intestine Absorption
1. simple molecules and vitamins1. simple molecules and vitamins2. most remaining water (~900 ml/day) 2. most remaining water (~900 ml/day)
Feces consists of:Feces consists of:1. water (about 100 ml/day)1. water (about 100 ml/day)2. undigested foodstuffs (plant fibers = cellulose)2. undigested foodstuffs (plant fibers = cellulose)3. bacteria3. bacteria4. products of bacterial decomposition4. products of bacterial decomposition5. sloughed epithelial cells5. sloughed epithelial cells
Defecation Reflex in the AdultDefecation Reflex in the Adult1. distention of the rectum 1. distention of the rectum
stimulates stretch receptorsstimulates stretch receptors2. sacral parasympathetic area output, 2. sacral parasympathetic area output,
causing:causing: a. contraction of the descending colon, a. contraction of the descending colon,
sigmoid colon, and rectum; andsigmoid colon, and rectum; and b. reflex relaxation of the b. reflex relaxation of the
internal anal sphincterinternal anal sphincter3. voluntary relaxation of the 3. voluntary relaxation of the
external anal sphincterexternal anal sphincter (in the infant, this is also reflexive)(in the infant, this is also reflexive)4. expulsion of feces4. expulsion of feces