1 31 2020 2 3 2020 2 5 2020 Chapter 14 Digestive System and Stomach Physiology 1 The six essential activities of the digestive system a Digestion b Absorption c Elimination i ii Ingestion Propulsion 1 Swallowing oropharynx 2 Peristalsis esophagus stomach small intestine large intestine iii Mechanical digestion 1 Chewing mouth 2 Churning mouth 3 Segmentation small intestine Chemical digestion Absorption Defecation 2 Digestive system organs iv v vi a Two groups i Alimentary canal GI tract 1 Mucosa the exterior b Epithelium c Lamina propria 2 Submucosa 3 Muscularis a Submucosal gland Inner circular layer a b Outer longitudinal layer 4 Serosa a Mucosal membrane line body cavities that are open to a Serosal membrane ii Accessory digestive organs b Sphincter circular layer of muscle that controls entry of fluids and solids c Body membrane thin layer of tissues that lines or covers the organs Composed of at least 2 tissue types 3 Smooth muscle in the digestive system i i a 2 layers along GI tract Circular layer 1 Around circumference 2 Contraction a Makes lumen smaller 3 Shows longitudinal views of smooth muscle fibers ii Longitudinal layer 1 Parallel to long axis of organ 2 Contraction shortens organ 3 Shows smooth muscle fiber in cross sections iii iv The cross section of the intestine shows the smooth muscle layers running at right angles to each other Contraction Contraction of circular muscles behind food mass 1 2 Contraction of longitudinal muscles ahead of food mass 3 Contraction of circular muscle layers forces food mass forward 4 pH logarithmic scale used to express how acidic or basic a substance is a H ion concentration b Scale from 0 to 14 0 6 is acidic i 1 Battery acid lemon juice saliva ii 8 14 is basic or alkaline 1 Seawater soapy water drain cleaner pH changes in different compartments of the digestive tract c d pH in a fed state pH in a fasted state e Neutralization due to saliva 7 and food 5 Negative feedback steps Initiation event or stimulus a b Variable c Receptor senses the change in variable d Control center compares against reference value i Set point e Negative feedback f Effectors make adjustments in the opposite direction as initiation event 6 Enzymes proteins that speed up reactions a Catalyst speeds up the rate of a favorable reaction b Always ends in ase c Lowers the activation energy for a reaction d Energy needed to start a chemical reaction Brings reactants closer together Reactants in right orientation Energy supplied to break and form bonds e Enzymes can be general but most are very specific Act on a specific substrate or chemical The reaction gives rise to the products reactants i ii iii i ii 7 Exocrine glands that secrete substances through ducts onto an epithelium 8 Endocrine glands that secrete substances into the blood 9 Types of metabolisms a Metabolism the sum of all biochemical reactions that occur inside a cell b Catabolism reactions that break complex molecules into simpler ones Cellular respiration breakdown can be harnessed to make ATP c Anabolism reactions that build complex molecules from simpler ones i i ii Requires energy Glucose created glycogen 10 Anabolic and catabolic reactions a Anabolic dehydration reaction Removal of water i ii Makes larger polymers from smaller ones iii iv Requires energy Synthesizing a polymer 1 Dehydration removes a water molecule forming a new bond b Catabolic hydrolytic reaction i ii iii Using water to breakdown polymers Releases energy Hydrolysis breaking down a polymer 1 Adds a water molecule breaking a bond 11 Biomolecules nutrients essential for survival growth maintenance and repair a Carbohydrates lipids proteins and nucleic acids b Also known as macromolecules c They are polymers chains of similar units called monomers i Polymers are made from monomers by dehydration reactions 1 Dehydration reaction a Covalent linkage of two monomers b Hydrogen removed from one molecule c Hydroxyl group removed from the other d Hydrogen and OH react to form water 2 Dehydration synthesis monomers are joined by removal of OH from one monomer and removal of H from the other at the site of bond formation ii Polymers broken into monomers by hydrolysis reaction 1 Hydrolysis monomers are released by the addition of a water molecule adding OH to one monomer and H to the other 2 Hydrolysis reaction Water splitting a b Cleavage of molecules with the addition of water c Using water to break covalent bonds d Carbohydrates i ii Sugars and starches Contain C H O 1 H O ratio is 2 1 iii 3 classes 1 Monosaccharides a Simple sugars 1 sugar b Monomer c Soluble 2 Disaccharides a 2 sugars 3 Polysaccharides long chains of linked monomers a Many sugars b Polymer of many monosaccharides e Lipids Contain C H O 1 Much less oxygen than carbs Insoluble in water 1 Nonpolar iii Main types 1 Triglycerides 2 Phospholipids 3 Steroids 4 Eicosanoids f Proteins Contains C H O N i ii Monomers amino acids i ii iii iv Linked together by peptide bonds Polymer of amino acids Polypeptide Function is dictated by structure 1 1 1 a Sequence of a chain of amino acids Primary 2 Secondary helices 3 Tertiary 4 Quaternary a Local folding of the polypeptide chain into sheets or a Three dimensional folding pattern of a protein due to side chain interactions a Protein consisting of more than one amino acid chain g Nucleic acids Composed of C O H N P i ii Made up of monomers called nucleotides 1 Adenine 2 Thymine 3 Cytosine 4 Guanine 1 DNA 2 RNA iii iv Double helix Watson and Crick Two major classes 12 Enzymes of chemical digestion a Breakdown proteins i ii proteases peptidases amino acids Proteins b Breakdown carbs Amylases Polysaccharide and disaccharide i ii c Breakdown RNA DNA i ii Nucleases Nucleic acid nucleotides d Breakdown fats Lipases Fat glycerol and fatty acids i ii 13 Oral cavity monosaccharide a Site of ingestion b Start of chemical saliva and mechanical chewing digestive c Saliva is made by salivary glands i ii iii Exocrine glands Cleanses mouth Lubricates food 1 98 water 2 2 other things PH of 6 5 7 iv v Multiple functions 1 Antibacterial defense 2 Clearance 3 Digestion 4 Lubrication 5 Mastication 6 Rinsing 7 Solubilization 8 Swallowing a 2 phases i ii Buccal phase 1 Voluntary Pharyngeal esophageal phase 1 Involuntary a Smooth muscle 2 Uvula rises 3 Larynx rises a Epiglottis block gottis 4 Upper esophageal sphincter relaxes a Bolus moves into esophagus 5 Begins as the uvula and larynx rise to prevent food from entering respiratory passageways The tongue