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Week of notes March 22-24

by: Madeline Notetaker

Week of notes March 22-24 Biol 2230-001

Madeline Notetaker
GPA 4.0

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About this Document

These are the notes from lecture this week on the digestive system
Human Anatomy & Physiology II
Dr. John Cummings
Class Notes
Digestive System, anatomy, Cummings
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This 63 page Class Notes was uploaded by Madeline Notetaker on Thursday March 24, 2016. The Class Notes belongs to Biol 2230-001 at Clemson University taught by Dr. John Cummings in Spring 2016. Since its upload, it has received 20 views. For similar materials see Human Anatomy & Physiology II in Biological Sciences at Clemson University.


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Date Created: 03/24/16
DigestiveSystem eliminates waste.Aone direction continuous tube nutrients, Organs •  Alimentary canal •  Along the line of the tube, pathway from mouth to anus •  Accessory organs •  Contribute to digestive process •  Teeth, tongue, gallbladder, liver… Actions •  Ingestion: •  Taking food into the system •  Can only get food in through mouth! Actions •  Propulsion: moving of food •  Deglutition= swallowing •  Starts propulsion •  Voluntary •  Peristalsis= smooth muscle contractions •  Involuntary *Propulsion is something that occurs everywhere is digestive system Actions •  Mechanical digestion: PHYSICAL breakdown (takes big chunks and turns them into little) •  Mastication= chewing •  Mixing= mixing food with other secretions •  Segmentation= alternation of contraction and relaxation of tube Actions •  Chemical digestion: enzymatic breakdown •  Enzymes are specific to different macromolecules •  Starts in mouth, stops, starts again in stomach, finishes in small intestine Actions •  Absorption •  Movement of digested product into lumen of alimentary canal, through vessels or lymphatic vessels •  Occurs in small intestine (and water in large intestine) Actions •  Defecation •  Elimination of waste/feces Controlmechanisms •  Sensors •  Sensory receptors: mechanical & chemical •  Stimuli: •  Stretch •  Osmolality (change in fluid composition) •  pH changes •  Presence of specific molecules (ex: proteins activate stomach) •  Nerve plexuses •  Involved in reflex responses •  Short reflexesIntrinsic) long reflexes (Extrinsic) either activate or inhibit the secretion of something or change the activity of muscle contractions •  Hormones •  Hormonal secretions from gland Mesentary Membranous tissue with a lot of fat, also on underside of organs holding it. High fat area that increases with age Tunics(Layers) •  Mucosa •  Superficial •  Purple in pic •  Epithelial tissue; predominantly simple columnar with goblet cells •  Secretory •  Submucosa •  Deep to mucosa •  Secrete enzymes, hormones •  Blood vessels, nerve fibers, lymphatic vessels •  Dense connective tissue with elastic fibers •  Muscularis externa •  Deep to submucosa •  Smooth muscle tissue •  2 parts: circular layer and longitudinal layer •  Can contract in 2 directions •  Serosa •  Thin layer •  Visceral peritoneum EntericNeurons •  Submucosal nerve plexus •  In submucosa of tube •  Activates glandular muscle contractionth •  Myenteric nerve plexus •  More important •  Between two muscle layers •  Changes smooth muscle contraction Oral(Buccal)Cavity ØBoundaries include cheeks, lips •  Palate: top of mouth; have hard and soft palate •  Helps to separate oral and nasal cavities •  Gives tongue something to push against Oral(Buccal)Cavity •  Tongue •  An accessory organ •  Involved in moving food in mouth and mixing it •  Form food into structure called bolus •  Functions in swallowing •  Covered in papillae •  Fungiform: provide •  Circumvallateceptors Oral(Buccal)Cavity •  Salivary glands •  Secretory glands that produce saliva •  Sublingual, submandibular, parotid glands •  Composed of mucus cells, serous cells, or both •  Saliva… •  Cleans mouth even when not eating to prevent bacteria buildup •  Helps dissolve food- put in solution •  Helps form bolus •  Can contain enzyme that allows breakdown of starch Saliva •  Water (97%) •  Electrolytes- charged ions •  Amylase- enzyme that can only breakdown s•  Substrate is long chain carbohydrates •  Mucin- protein associated with mucus •  Lubricant •  Lysosome- immune function •  IgA- immune function •  Metabolic wastes- urea and uric acid Ø pH is slightly acidic Ø Produce 1-1.5 L liter a day Ø Under autonomic NS control Ø Increases due to parasympathetic activity Ø Can by prompted by chemoreceptors or pressure receptors or memory Oral(Buccal)Cavity •  Teeth •  An accessory organ •  Involved in mastication •  32 in adults •  Different kinds: •  Incisors •  Cupids •  Premolars •  Molars •  Teeth come in stages; don’t erupt at once •  Get 20 primary teeth, lose them, replaced with permanent ones, then wisdom tooth ToothStructure Gumline Crown: exposed part Enamel: hard structure, Dentine: deep to enamel Pulp: deep to dentine, nerves Cementum: part that holds tooth in socket No enamel in root, dentine and pulp run down root Pulp exits through root canal Pharynx When we swallow, the epiglottis, covers the trachea and forces food down esophagus Only things that occurs in pharynx is propulsion Esophagus •  Only thing that happens in esophagus is propulsion •  2 sphincters: •  Upper esophageal sphincter •  Gastroesophageal sphincter Deglutition •  Food compacted into bolus •  Buccal phase: VOLUNTARY PHASE •  Tip of tongue is placed against hard palate •  Tongue contracts to force bolus into oropharynx •  Bolus stimulates tactile receptors •  Pharyngeal-esophageal phase: INVOLUNTARY •  Tactile receptors stimulate medulla and pons •  Motor impulses sent to muscles •  Peristalsis moves bolus toward stomach Stomach A storage tank; empty volume is 50 mL, but can stretch to hold up to 4 L; chemical breakdown; and greater; True sphincter at pyloric to control emptying, lets out small amounts; Folds calledsser rugae to increase surface area and can collapse to change shape StomachCells •  Goblet cells •  Produce mucus StomachCells •  Goblet cells •  Mucous neck cells •  Series of cells •  Also mucus producing, but more acidic mucus StomachCells •  Goblet cells •  Mucous neck cells •  Parietal cells •  Secrete hydrochloric acid pH of 2 •  Secrete intrinsic factor which is required for us to absorb vitamin B12 StomachCells •  Goblet cells •  Mucous neck cells •  Parietal cells •  Chief cells •  Produce protein pepsinogen which is an inactive protein activated by HCl •  Also produce lipase StomachCells •  Goblet cells •  Mucous neck cells •  Parietal cells •  Chief cells •  Enteroendocrine cells •  Very bottom of gastric glands •  Produce hormone gastrin •  Often called G-cells GastricSecretion ØUnder neural and hormonal control •  Cephalic (reflex) phase •  Happens before food arrives in stomach •  Aconditioned reflex GastricSecretion •  Cephalic (reflex) phase •  Gastric phase •  When food actually arrives in stomach •  As food arrives, stretches signal back to stomachbrain, causes secretion •  Food with proteins arrives in stomach, stimulates G- cells to release gastrin, gastric glandsity of GastricSecretion •  Cephalic (reflex) phase •  Gastric phase •  Intestinal phase •  Related to food leaving stomach •  2 components: 1.  first start leaving and arrive in duodenum 2.  Inhibitory:As we continue to have things leave MucosalBarrier •  Bicarbonate-rich mucus •  So we do not digest our own stomach! •  Tight junctions in mucosal epithelium •  Doesn’t allow acids to leak through •  HCl-impermeable plasma membranes in gastric gland cells •  HCl can only go out not through •  Undifferentiated stem cells at junction of gastric pits and gastric glands •  To continue to replace cells •  Lining is replaced every 3-6 days GastricFilling Changes size! •  Receptive relaxation •  Before food arrives in stomach •  Prevents stretch from happening •  Adaptive relaxation •  Once food arrives, pressure doesn't’t increase until about 1 L in stomach GastricContraction •  Basic electrical rhythm •  Interstitial cells of Cajal •  Depolarize to cause smooth muscle contraction •  3 contractions per minute GastricContraction •  Basic electrical rhythm •  Interstitial cells of Cajal •  Depolarize to cause smooth muscle contraction •  3 contractions per minute •  Rate can change •  Waves pushing everything toward pyloric sphincter • is liquid thing that can get though sphincter •  As chyme arrives, initially activates stomach, continues to activate à increase in pressure slows down stomach •  STOMACH EMPTIES SLOWLY GastricEmptying Ø About 4 hours after meal- starts to empty 1.  Chyme enters duodenum (very slowly!) 2.  Stretch and chemoreceptors in the duodenum activated (by pH, proteins, fats) 3.  Enterogastric or enterogastone reflexes initiated •  Enterogastric: reduces stomach activity by inhibiting vagal nerve stimulation or causing sympathetic stimulation of pyloric sphincter •  Enterogastone: reflex that uses a hormone that shuts off activity of stomach 4.  Gastric activity reduced 5.  Pyloric contractions reduced 6.  Duodenal filling stoppedà aka stop emptying stomach LONG organ length Runs from pyloric valve to large intestine segmentsinto SmallIntestine (themajor organofchemicaldigestion) Subdivisions •  Duodenum •  First 10 inches •  Little opening in wall called hepatopancreatic ampulla •  Adds secretions from pancreases and liver Subdivisions •  Jejunum •  Roughly 8 ft- most of intestine small •  Continues digestion and begins absorption Subdivisions •  Ileum •  Roughly last foot •  All digestion is finished, most absorption is finished •  StructuralModifications ofsmallintestine •  Length •  Long coiled tube •  High surface area •  So extremely efficient •  Can further increase surface area with folds StructuralModifications •  Length •  Plicae circulares •  Folds into the lumen •  Slow the movement of chyme and increases absorptive ability StructuralModifications •  Length •  Plicae circulares •  Villi •  Finger like projections of just mucosa on top of plicae circulares to further increase SA StructuralModifications •  Length •  Plicae circulares •  Villi •  Microvilli •  Cells that make up villi •  Resembles a brush •  Brush border produces enzymes to break down carbs and proteins Liver •  An accessory organ •  Primary function is to recycle RBC •  Largest gland of the body •  Produces bile •  Bile functions as an emulsifier •  Emulsification is form of mechanical digestion- takes big globs of fat and turns them into little globs • chemical digestion to occur!for •  Bile salts •  Substances that actually emulsify •  Bile pigments •  Bilirubin- further brokUrobilinogen •  Urobilinogen- brown pigment •  Cholesterol •  Neutral fats •  Phospholipids •  Electrolytes Bilecomposition 4Lobesofliver 1.  Right 2.  Left 3.  Caudate 4.  Quadrate •  Falciform ligament •  Dicides liver into right and left sides •  Descends from diaphragm Ducts •  Common hepatic duct •  Carries secretions from liver to duodenum •  Bile duct •  When common hepatic duct joins with gallbladder •  Cystic duct Gallbladder •  Astorage container •  Stores bile • produces bile but we don’t need it all the time unless we are digestion •  Concentrates bile •  Becomes more concentrated •  Sometimes super concentrates it- need to get removed BileStorage •  Hepatopancreatic sphincter closed when not digesting •  Liver continually produces bile •  Bile backs up cystic duct BileRelease Ø Fatty chyme entering duodenum stimulates production of cholecystokinin (CCK) by intestine Ø CCK is a hormone that causes parasympathetic impulses to promote gallbladder contraction Ø CCK also relaxes hepatopancreatic sphincter Pancreas •  Produces pancreatic juice •  Acinar part of pancreas •  Juices travel through pancreatic duct, which joins bile duct and enter through ampulla PancreaticJuice •  Water •  Enzymes •  macromoleculess of •  Bicarbonate •  pancreatic ductls of •  Has a high pH (>8) •  If we didn’t have it, enzymes would be denatured and couldn’t function 1.  Trypsin- active enzyme •  Dumped into duodenum •  Trypsinogen- inactive form of trypsin •  Enterokinase- activates Trypsinogen (enterokinase is a brush border secretion) 2.  Carboxypeptidase- active enzyme •  Procarboxypeptidase- activated by trypsin •  Trypsin 3.  Chymotrypsin- active enzyme •  Produced by pancreas •  Chymotrypsinogen- also activated by trypsin •  Trypsin ProteaseEnzymes (breakdownofproteins) •  Amylase •  Breaks down smaller carbs (*salivary amylase breaks down starch) •  Lipase •  Class of enzymes that break down fats •  Nucleases •  Break down nucleic acids OtherpancreaticEnzymes •  Secretin •  Intestinal hormone •  Release is stimulated by high levels of HCl •  Acts of pancreatic duct cells, causing them to release bicarbonate •  CCK •  Stimulates acinar cells to secrete enzymes •  Parasympathetic impulses •  Nervous control •  Activates acinar cell activity of pancreas ControlofPancreatic Secretion Emptyingofsmallintestine • intestinel valve at entrance of large •  Normally closed •  Gastroileal reflex • of segmentation in the small intestineorce •  Gastrin • Ileocecal valve- opens it up that relaxes •  Pressure •  Don’t want to empty too much at once so pressure builds in cecum which closes valve First part called cecum, vermiform appendix not used but can become inflamed by seeds and rupture, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus, 2 sphincters Anatomyoflargeintestine •  Haustra •  Segments; saclike puckerings (constrictions) •  Feces is composed of undigested food residue, sloughed off epithelial cells, bacteria, and water •  Large intestine absorbs water Anatomy •  Haustra •  Taenia coli •  Bands of smooth muscle that cause puckerings Anatomy •  Haustra •  Taenia coli •  Epiploic appendages •  On external surface •  Unsure of function •  Possibly did something in the past IntestinalBacteria •  Symbiotic relationship with bacteria •  We both benefit •  Bacteria ferment indigestible carbohydrates (like cellulose) •  of fermentatione is product •  Synthesize B vitamins •  Synthesize vitamin K •  Used to make clotting factors Motilityinlargeintestine •  Haustral contractions •  Haustrum contracts and squeezes contents to next one •  Slowly move things through •  Occur roughly every 30 minutes, all day long •  Prompted by stretch •  Mass movements •  Large peristaltic movements that push directionally •  3-4 times daily •  Signaled by gastric filling DefecationReflex •  Mass movements cause stretch •  Stretch triggers parasympathetic stimulation of sigmoid colon and rectum and inhibits anal sphincters •  Relax anal sphincters •  External anal sphincter under voluntary control •  Valsalva’s maneuver assists emptying


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