chapter 14 digestive system anatomy and physiology ii ms. harborth
TRANSCRIPT
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Chapter 14Digestive SystemAnatomy and Physiology IIMs. Harborth
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PART I:Digestive SystemTakes in food (ingests)Breaks it down physically
(digests)Absorbs nutrientsRids body of indigestible
remains (defecates)
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Anatomy of the Digestive System
Alimentary canal (GI tract)◦ Ingests,
digests, absorbs, defecates
Accessory digestive organs◦Teeth, tongue,
large digestive glands
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Alimentary CanalContinuous, hollow muscular tubeSubmucosal and myenteric nerve
plexuses30 feet long in cadaver
◦Mouth◦Pharynx◦Esophagus◦Stomach◦Small intestine◦Large intestine◦Anus
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MouthLabiaCheeksHard and soft
palateUvulaVestibuleOral cavity
properTongueLingual
frenulum
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PharynxOropharynxLaryngopharyn
x2 skeletal
muscle layers◦Inner layer
longitudinal◦Outer layer
circularPeristalsis
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Esophagus10 inches long4 tissue layers
◦Mucosa – innermost◦Submucosa◦Muscularis externa◦Serosa
Visceral peritoneum Parietal peritoneum
Mesentery
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Stomach10 inches long,
can hold 1 gallonDiameter changesCardiac region
◦Cardioesphageal sphincter
FundusBodyPylorus
◦Pyloric sphincter
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StomachRugaeGreater
curvatureLesser
curvatureLesser
omentumGreater
omentum
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StomachGastric pits
◦Gastric glands◦Gastric juice
Ex: Intrinsic factorChief cells
◦pepsinogensParietal cellsMucous neck cellsChyme
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Small Intestine 6-13 ft longIleocecal valveDuodenumJejunumIleumPancreatic ductsBile ductPeyer’s patches
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Food AbsorptionMicrovilliVilli
◦Lacteal lymphatic capillary
Circular folds
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Large Intestine5 ftCecumAppendixColon
◦Ascending colon◦Transverse colon◦Descending colon◦Sigmoid colon
RectumAnal canal
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Accessory Digestive OrgansSalivary glands
◦Parotid glands◦Submandibular glands◦Sublingual glands
Saliva◦Bolus◦Salivary amylase◦Lysozyme and IgA antibodies
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Accessory Digestive Organs
Teeth◦Masticate◦Deciduous teeth◦Permanent teeth◦Incisors◦Canines◦Premolars (bicuspids)◦Molars
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Teeth ContinuedCrown and RootGingivaEnamelNeckCementumPeriodontal membrane (ligament)DentinPulp cavityPulpRoot canal
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Accessory Digestive Organs
Pancreas◦Retroperitone
al◦Digestive
enzymes in alkaline fluid
◦Endocrine organ
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Accessory Digestive Organs
Liver and Gallbladder◦Liver
4 lobes Bile Common hepatic duct
◦Gallbladder Cystic duct Stores and concentrates bile
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Functions of Digestive System1. Ingestion2. Propulsion3. Food breakdown: mechanical
digestion4. Food breakdown: chemical
digestion5. Absorption6. Defecation
digestion animation
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Digestion ReflexesMechano/Chemoreceptors
triggered by:◦Stretch of organ by food◦pH of contents◦Presence of certain breakdown
productsActivate or Inhibit:
◦Glands that secrete digestive juices or hormones
◦Smooth muscles that mix and propel food
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Activities of Mouth, Pharynx, and Esophagus
Mouth – mechanical and chemical digestion
Deglutition (tongue, soft palate, pharynx, and esophagus)◦Buccal phase◦Pharyngeal-esophageal phase
FYI: Swallowing can occur while standing on your head!
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Activities of StomachSight, smell, and taste of
food stimulates parasympathetic reflexes◦Gastric juices secreted◦Hormone gastrin released
Makes stomach glands produce pepsinogens, mucus, and HCl
FYI: You make 2-3 Liters of gastric juice a day!
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Chemistry in the StomachHCl makes pepsinogen pepsinRennin: works on milk protein
(only in infants)Hardly any chemical digestion
occurs ◦Aspirin and alcohol are absorbed
through stomach wall
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Food Propulsion from Stomach
Chyme is end productPylorus only allows liquid
and small particles to pass through sphincter
Each contraction squirts 3 ml of chyme
Rest is squeezed back into stomach◦ Causing enterogastric reflex
FYI: It usually takes 4 hours for your stomach to empty, or 6 hours if meal was high in fat
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Activities of Small IntestineCarb and protein digestion had begun in
stomach, but no fat digestionMicrovilli make few enzymes
◦ Brush border enzymes◦ Hormones:
Secretin Cholecystokinin (CCK)
Pancreatic juices are enzyme and bicarbonate rich◦ Complete digestion of starch◦ Carry out ½ of protein digestion◦ Responsible for fat digestoin◦ Digest nucleic acids
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Absorption in Small IntestineWater and end products absorbed
through intestinal cell plasma membranes via active transport◦Except lipids – absorbed through diffusion
Then to the hepatic portal veinBy the end of ileum, only water and
indigestible food materials and LOTS of bacteria
FYI: Takes about 3-6 hours for food to go through small intestine
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Activities of Large Intestine
Bacteria metabolize and release gases (methane and hydrogen sulfide) and some vitamins
These gases make feces smell
Peristalsis and mass movements
Defecation reflex
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PART II:Nutrition and MetabolismMajor nutrients
◦Carbohydrates◦Lipids◦Proteins
Vitamins and mineralsWater
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MetabolismCatabolism and
anabolismCarbohydrate
metabolismFat metabolismProtein
metabolism
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Carbohydrate MetabolismGlucose
ATPCellular
respiration◦Glycolysis,
Krebs cycle, electron transport chain
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Fat MetabolismLiverFat is broken
down to acetic acid
Acetic acid is broken down in mitochondria to make ATP, CO2, and water
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Protein MetabolismProteins are broken down
into amino acidsCellular uptake20 amino acids are
needed, 8 can’t be made by our cells (“essential amino acids”)
IF no other energy source is available, amine groups are removed as ammonia, and rest is used by mitochondria for ATP
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Liver’s Role in MetabolismUsed in digestion, detoxifying
drugs & alcohol, degrades hormones, makes cholesterol, albumin, clotting proteins and lipoproteins, and METABOLISM
Blood circulates through, liver grabs nutrients and macrophages kill pathogens
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LiverGlycogenesisGlycogenolysisGluconeogenesis
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CholesterolHDL and LDL
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Body Energy BalanceEnergy intake = heat + work +
energy sourceRising or falling blood levels of
nutrients, hormones, or body temperature affect eating behavior
Psychological factors influence as well
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Metabolic RateBasal metabolic rate
◦Amount of heat produced when at rest◦ Influenced by:
Surface area Sex Age Emotions Amount of thyroxine
Total metabolic rate◦Amount of kilocalories body needs to fuel
all activities◦Stays elevated well after exercise
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Body Temperature RegulationHypothalamus
◦Heat-promoting mechanisms Vasoconstriction Shivering
◦Heat loss mechanisms Radiation through skin