Still Digesting Pharynx, esophagus, stomach, pancreas, and liver

Pharynx Connects nasal and oral cavities to larynx and esophagus 3 Parts – you do not need to know def. of each Nasopharynx – w/ nasal cavity provides passage for breathing Oropharynx – posterior to soft palate, inferior to nasal cavity; passage for food from mouth, and air to/from nasal cavity Laryngopharynx – inferior to oropharynx, passage to esophagus

Friday Writing Reflection On a sheet of paper to be turned in in Bin C at the end of the period, please write words on the following prompt: Who are 2 people that you admire? Choose 1 adult (20+ years old) and 1 high school student. Why? What qualities do they embody? How do they stand out from the rest of their peers?

Epiglottis Directs food down into esophagus while preventing food/liquids from entering larynx/trachea Will get confused if you try to do too many things at once…thus you choke Epiglottis Animation Swallowing Animation

Esophagus Straight collapsible tube, 25cm long Passageway for food from pharynx to stomach Connects to stomach at cardiac sphincter (thickened wall of circular smooth muscle)

Stomach Capacity 1 liter 4 regions Cardiac – near esophagus Fundic – temporary storage area Body – main portion Pyloric – end of stomach  pyloric canal Ends in pyloric sphincter which controls gastric emptying

Gastric Secretion Gastric juice – products of mucous cells, chief cells, and parietal cells Those 3 cells make up the gastric glands

Gastric Secretion cont. ComponentSourceFunction PepsinogenChief cells from gastric gland Inactive form of pepsin PepsinFormed when pepsinogen reacts with acid Protein splitting enzyme that digests nearly all types of dietary protein Hydrochloric Acid (HCl)Parietal cells from gastric gland Acid environment for conversion of pepsinogen to pepsin MucusGoblet cells and mucous glands Provides viscous, alkaline protective layer on the inside stomach wall Intrinsic factorParietal cells of the gastric glands Aids in Vitamin B 12 absorption

Regulation of Gastric Secretions Juice produced continuously; rate varies  controlled neurally and hormonally Parasympathetic impulses on vagus nerve stimulate stomach cells to release gastrin Gastrin – peptide hormone that increases secretory activity of gastric glands Sympathetic impulses in small intestine trigger release of cholecystokinin Cholecystokinin – hormone that decreases gastric motility as small intestine fills with food Note: the stomach does not absorb nutrients…only alcohol and some lipid soluble drugs

Moving out of the Stomach Chyme – semifluid paste of food particles and gastric juice Moves into the duodenum (first portion of small intestine) Pancreas, liver, and gallbladder then add their secretions Secretin and cholecystokinin – hormones secreted by duodenum to initialize pancreatic secretions

Pancreas Secretes digestive juice  pancreatic juice Pancreatic duct extends the length of the pancreas and connects to the duodenum Pancreatic juice Pancreatic amylase – enzyme that breaks down carbs Pancreatic lipase – enzyme that breaks down lipids into fatty acids and glycerol Nucleases – enzymes that break down nucleic acids into nucleotides Sodium bicarbonate – chemical released to neutralize acid

Pancreas cont. Protein splitting enzymes: Trypsin, chymotrypsin, and carboxypeptidase Split bonds between amino acids in proteins Released in inactive forms Activated in small intestine by other enzymes Ex. Trypsinogen is turned into trypsin by enterokinase (produced by SI)

Liver Located in upper quadrant of abdominal cavity just inferior to diaphragm Reddish, brown well supplied w/ blood vessels Hepatic cells produce bile Bile contains several ingredients the most important being bile salts Bile salts break fat globules into smaller droplets  emulsification Lipases are then able to break them down Bile moves through hepatic ducts

Gallbladder Stores bile produced by the liver Cystic duct connects to the common hepatic duct to form the common bile duct Be able to label these ducts on a diagram of the liver/gallbladder