BIOL 112 1st Edition Lecture 15 Outline of Last Lecture I The Crown Group II Kingdom Plantae III Plant Evolution IV Cryptogams V Phylum Bryophyta VI Advances of Bryophytes from Algae VII Tracheophytes VIII Phylum Pterophyta IX Advances of Ferns over Mosses X Seed Plants XI Gymnosperms XII Phylum Coniferophyta XIII Male Cone and Pollen XIV Female Cone and Eggs XV Seed XVI Advances of Conifers over Ferns XVII Angiosperms XVIII Phylum Anthophyta XIX Flower Anatomy XX The Ovule These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Outline of Current Lecture XXI Background of Form Function XXII The Digestive System XXIII The Human Digestive System A Pharynx B Esophagus C Stomach D Small Intestine XXIV Absorption Current Lecture I Background of Form Function Cells make up tissues tissue a group of cells with common structure function made up of the same differentiated type Tissues make up organs organs specific collection or grouping of different tissues the whole having some specific function ex skin organ system collection of different organs with specific overall function to body Different types of tissue Epithelial Tissue make up digestive system various types stratified squamous cuboidal simple columnar simple squamous pseudo stratified columnar apical surface is on the outside basal faces another type of tissue on the inside Connective Tissue Loose connective tissue fibrous connective tissue adipose tissue cartilage these tissues hold parts of the body together Muscle Tissue Skeletal muscle voluntary muscles smooth muscle organs cardiac muscle heart how the animal moves around II The Digestive System Four Major Functions Processing food Absorbs organic nutrients that are produced from processing the food Absorption of electrolytes Absorption of water Processing Digestion Breaking of each of the macromolecule types into monomers we cannot absorb polymers they are too big Hydrolysis Catabolic Reaction Polysaccharides simple sugars Proteins amino acids Lipids fatty acids and glycerol Nucleic acids nucleotides Primitive Animals vs Advanced Animals Digestion used to be mostly intracellular Paramecium engulfs food and digests in lysosomes digestion completed in cells Now digestion is exclusively extracellular hydrolytic reactions must occur in lumens of digestive organs then cells lining the lumen absorb the new monomers III The Human Digestive System Starts at mouth ends at anus If you were to take out your digestive system it would be approximately 5 times your height Start with Food Mouth Chewing reflex teeth Saliva has 2 main functions it mixes the food with ptyalin salivary amylase mucus binds the food together to make bolus of food also lubricates A Pharynx Throat combined organ for digestive and respiratory system swallow reflex Epiglottis acts as a hatch over the opening of the glottis prevents food from being swallowed into lungs or inhaled B Esophagus tube leading to stomach waves of peristaltic contractions push materials along to stomach regardless of gravity s pull on it doesn t matter if you re standing or laying down the action of the contractions is called Peristalsis C The Stomach a big bag that can hold about a liter of material sealed at both ends by sphincters valves sphincters tend to remain closed unless a signal is sent to relax Gastroesophageal sphincter upper end of stomach opened by peristaltic wave from esophagus Pyloric Sphincter lower end of stomach permits food to enter intestines after stomach is done processing food extreme conditions in the stomach found no where else in the body very acidic pH 1 2 hydrochloric acid enzyme pepsin hydrolysis of peptide bonds food broken up from bolus into liquid mush chyme 2 to 4 hours after a meal the stomach has completed its procession of the food from boluses into chyme and is now ready to send the contents along to small intestine With each peristaltic wave the pyloric sphincter opens and a small volume of chyme is squirted into the small intestine D Small Intestine About 3x your height folded up in your abdomen 3 distinct sections Duodenum 25 cm the smart part of the intestine closest to stomach cells sense the opening of the pyloric sphincter and appearance of acid chyme then secretes alkaline mucus into the lumen pH shifts from 2 to about 7 8 Jejenum 1 8 m Ileum 2 7 m Liver Gall Bladder Bile flows down bile duct to duodenum Basically liver secretes bile bile stored in bag called gall bladder Bile contains no enzymes It is a detergent emulsifies fats into tiny globule This increases the surface area for attach by lipase enzymes Bile emulsification also helps absorption of digested fatty acids by carrying fatty acids to absorptive cells Bile is also alkaline to neutralize stomach acid IV Absorption In advanced animals there is no phagocytosis in digestion all absorption then must be with monomers across the plasma membrane passive diffusion facilitated diffusion active transport Absorptive cells of small intestine can concentrate materials from chyme then release these materials into the bloodstream both steps occur by active transport Total absorptive area of small intestine is about 300 m2 about the size of a tennis court How does it get so much area Folding at several levels of structure Circular Folds in inner face of intestine Villi on folds villus is smaller finger like projection of tissue Microvilli of epithelial cells also called brush border All these features increase surface area for absorption