Digestive System
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68 terms
Terms | Definitions |
|---|---|
 Digestive Function (6) | 1- Ingestion of food 2- Propulsion- movement (swallowing-degultination) (peristalisis- movement along tract) 3- Mechanical digestion (Mastication, churning, segmentation) 4- Chemical digestion (enzymes, macromolecules--> micromolecules, pass through tract wall) 5- Absorption (lumen of tract --> epithelium --> blood) 6- Defecation |
| Gastrointestinal tract | Mouth --> pharynx --> esophagus --> stomach --> small intestine --> large intestine --> rectum --> anal canal --> anus |
| Accessory organs | Teeth, tongue, salivary glands, liver, gall bladder, pancreas |
| Enteric nervous system | Submucosal and myenteric nerve plexuses Controls esophagus, stomach, intestine activities |
| Tract wall | 4 layers- Mucosa, submucosa, muscularis, serosa Moslty under parasympathetic control- vagus nerve |
| Mucosa | Inner mucous membrane with simple columnar epithelium and lamina propria Mucous membrane characterized by folds, glands and projections |
| Muscularis mucosa | Thin muscle band controlling local mucosa movements/responses |
| Submucosa | Binds mucosa to muscularis Blood and lymphatic vessels absrob nutrients from digestive tract |
| Submucosal nerve plexus | Stimulates submucosal glands and muscularis mucosa |
| Muscularis | Thickest layer 2 smooth muscle layers - (3 in stomach) Inner circular layer - decreases diameter (Form sphincter valves) Outer longitudinal layer- decreases length |
| Sphincter vavles | Propel and mix food Prevent backflow |
| Myenteric nerve plexus | Responds to stretch ANS Stimulates muscle layers |
| Serosa | Outer layer Visceral peritoneum Secretes serous fluid Mostly parasymphathetic control - vagus nerve |
| Oral Cavity | Analyzes food, moistens food, forms bolus, initiates enzyme digestion |
| Uvula | Blocks nasopharynx when swallowing |
| Tongue | extrinsic and intrinsic skeletal muscles |
| Salivary glands | Produce saliva containing water, amylase, lipase, antibacterial agents, mucus; 1 liter/day Parotid glands -- over masseter muscle Sublingual glands -- under tongue Submandibular glands -- under sublingual gland & mandible |
| Dentin | Bone like material compsing most of tooth |
| Crown | Above gum line Covered by enamel- hardest substance in body |
| Root | Below gum line Projections anchor tooth in jaw bone |
| Gums | (Gingivae) Covers surface between teeth |
| Periodontal ligament | Lines alveolar socket Anchors teeth and absorbs shock |
| Cementum | Secures tooth to peridontal ligament |
| Central (pulp) cavity | Contains blood vessels and nerves |
| Pharynx | Throat Nasopharynx, oropharynx, laryngopharynx |
| Esophogus | Propels food into stomach Extends through mediastinum of thoracic cavity Begin with swallowing (deglutination)- voluntary & involuntary muscles Lower esophageal (cardiac) sphincter at opening into stomach Gravity aids peristalsis- liquids 1 to 2 seconds, bolus 4 to 8 seconds Stratefied squamous epithelium in mucosa layer (not simple columnar) Adventitia on outer layer (not visceral peritoneum- serosa) |
| Stomach | Churns/mixes bolus with gastric juices and forms chyme Empties into duodenum through pyloric sphincter Acididc (pH = 2) Mucosa- thick; forms rugae when empty Epithelium replaced every 3 to 6 days- tight junctions secure cells |
| Gastric glands | Secrete gastric fluids into stomach through gastric pits |
| Chief cells | Produce enzyme pepsinogen; released in inactive form Pepsin= active form-- denatgures proteins and kills bacteria |
| Parietal cells | Secrete HCl and intrinsic factor |
| Intrinsic factor | Required for vitamin B12 absorption |
| HCl | Converts pepsinogen to pepsin-- denatures proteins and kills bacteria |
| Mucous cells | Secrete alkaline mucous |
| Enteroendocrine (G) cells | Hormone Secrete stomach gastrin into blood Stimulates HCl and pepsinogen production Contracts lower esophogeal sphincter Loosens pyloric sphincter |
| Muscularis | 3 muscle layers: Inner oblique, middle circular and out longitudinal |
| Mesentery | Derived from parietal peritoneum (greater omentum) |
| Greater omentum | Form of mesentery Extends from stomach into cavity Covers and protects abdominal organs Contains adipose, blood vessels, lymph nodes and nerve endings |
| Small intestine | Held in place by mesentery--> Duodenum, jejunum, ileum Projections into mucosa increase surface area |
| Duodenum | 1' , retroperitoneal (behind parietal peritoneum) Digestive enzymes and bile enter here through hepatopancreatic sphincter |
| Jejunum | 8', Bulf of digestion & absorption |
| Ileum | 12', opens into large intestine through ileocecal sphincter |
| Circular folds (plicae circularis) | Ridges in mucosa Spiral, mix and slow movement of chyme |
| Villi | Extensions of mucosa |
| Microvilli | Extensions of plasma membrane of absorbing cells |
| Intestinal glands (crypts) | Between villi Secrete intestinal fluid and hormones |
| duodenal (Brunner's) glands | In submucosa of duodnum Secrete bicarbonate *** neutralize stomach acid |
| Bicarbonate | Neutralizes stomach acid-- secreted by Brunner's gland and pancreatic acinar cells Inhibits pepsin |
| Lymphatic nodules | Peyer's patches (ilium) Prevent bacteria from entering blood |
| Duodenal enteroendocrine glands | Secrete CCK and secrtin (hormones) |
| CCK | Stimulates gallbladder contraction and opens hepatopancreatic sphincter Stimulates enzyme release from pancreas |
| Secretin | Stimulates bile production by liver and stimulates bicarbonate release from pancreas |
| Large intestine | thick mucosa little digestive function reabsorbs water, electrolytes, biles salts, vitamins forms & stores feces ascending, transverse, descending, sigmoid |
| Cecum | Entrance into large intestine |
| Vermiform appendix | Some lymphatic function No digestive function |
| Rectum | Stores feces Opens to outside through anal canal and anus |
| Anus | Internal (involuntary) and external (voluntary) anal sphincters control movement Stratified squamous epithelium in anal canal |
| Mass peristaltic movements | Waves of muscle contractions moving feces to rectum |
| Liver & functions | Largest gland 4 lobes- large left & right lobes Functions: -Control blood glucose levels (form glycogen to decrease glucose levels) (break down glycogen to increase glucose levels) -CHO, fat and protein metabolism -Storage of vitamins, iron & copper -Removal of drugs, hormones and toxins -Production of bile- contains water, ions, cholesterol, bile salts and bilirubin -*Synthesis of bile salts from cholesterol*-- bile salts emulsify fats for absorption -- keeps cholesterol dissolved in bile -Synthesis of blood proteins- transport, clotting & completment proteins -Phagocytosis |
| Blood enters liver through | Hepatic artery & hepatic portal vein (from digestive tract) |
| Hepatic lobules | 6 sided with rows of hepatic cells arranged around central vein |
| Portal triad | At each corner of hepatic lobule Composed of hepatic arteriole, hepatic portal venule & bile duct Blood passes through hepatic sinusoids and empties into central vein -- leads to hepatic vein |
| Kupffer's cells | -Phagocytic -Remove old RBC, WBC and bacteria |
| Hepatic cells | Carry out most functions of the liver Form and secrete bile into bile canaliculi-- bile flows into bile ducts |
| Bile pathway | Secreted by hepatic cells --> bile canaliculi --> left/right hepatic bile ducts --> form common hepatic duct --> leaves liver --> merges with cystic duct of gall bladder--> forms common bile duct --> merges with main pancreatic duct --> bile enters duodenum through hepatopancreatic sphincter |
| Hepatic stem cells | Capable of mitosis *** Regenerate parts of liver |
| Gallbladder | Simple columnar epithelium with 1 muscle layer Stores biles Releases bile when fats enter duodenum Duodenal enteroendocrine glands secretes CCK into blood when fats enter --> contracts smooth muscle in gallbladder and relaxes hepatopancreatic sphincter --> bile moves through common bile duct into duodenum --> hepatopancreatic sphincter closes when fats no longer present in duodenum |
| Pancreas | Mostly retroperitoneal -secretes bicarbonate & digestive enzymes Secretions enter main pancreatic duct --> merges with common bile duct --> duodenum through hepatopancreatic sphincter Secretions move through accessory pancreatic duct when hepatopancreatic sphincter closes (All enzymes except lipase) |
| Pancreatic acinar cells | Exocrine Secrete bicarbonate and digestive enzymes |
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