the digestive system Flashcards
what is ingestion?
-taking in food
-what is absorption?
-movement of nutrients into the bloodstream
what is digestion?
-breaking food into nutrient molecules
what is defecation?
-excretes to rid the body of indigestible waste
two main groups of organs
-alimentary canal
-accessory digestive organs
the mouth in the digestive system
-mastication (chewing) of food
-tongue mixes chewed with saliva
-tongue initiates swallowing
-taste buds on the tongue allow for taste
the teeth in the digestive system
-teeth masticate into smaller fragments
-incisors-cutting
-canines-tearing or piercing
-premolars-crushing and grinding
-molars-crushing and grinding
teeth
-crown
-enamel
-dentin
-pulp cavity
-root canal
-good dental health is important to ensure proper mastication of food to aid digestion
crown
exposed part of tooth above the gum
enamel
covers the crown
dentin
bulk of the tooth
pulp cavity
contains connective tissue, blood vessels, and nerve fibres
root canal
where outer surface and attaches the tooth to the peridontal membrane
salivary glands
-three pairs of salivary glands empty secretions into the mouth
-saliva is a mixture of mucus and serous fluids
-helps to moisten and bind food together into a mass called bolus
-salivary amylase- begins starch digestion
-lysozymes and antibodies- inhibits bacteria
what are the three compositions of the pharynx
-nasopharynx
-oropharynx
-larynogopharynx
the pharynx
-serves as a passageway for food, fluids and air
the pharynx in digestion
-food passes from the mouth posteriorly into the oropharynx then larynogopharynx
-food is propelled to the oesophagus by alternating contractions of two skeletal muscle layers
oesophagus
-runs from pharynx to stomach through diaphragm
-conducts food by peristalsis to the stomach
-passageway for food only
anatomy of the stomach
-gastric glands that secrete gastric juice, including intrinisc factor needed for vitamin B12 absorption
-parietal cells produce hydrochloric acid that activates enzymes
-pyloric region is the site of most digestive activity
the stomach
-food enters at a sphincter from the esophagus
-food empties into the small intestine at the pyloric sphincter
-greater omentrum- extension of peritoneum, insulates, cushions, and protects abdominal organs
peristaltic waves in the stomach 1
-propulsion:
peristaltic waves move from the fundus toward the pylorus
peristaltic waves in the stomach 2
-grinding
-the most vigorous peristalsis and mixing action occur close to the pylorus
-the pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum
peristaltic waves in the stomach 3
-grinding
-the peristaltic wave closes the pyloric valve
-forcing most of the contents of the pylorus backward into the stomach
small intestine
-site of nutrient absorption in the blood
-chemical digestion begins in the small intestine
-enzymes produced by intestinal cells and pancreas are carried to the duodenum by pancreatic ducts
-bile, formed by the liver, enters the duodenum via the bile duct
small intestine
-structural modifications increase surface area for food absorption
-villi- finger like projections formed by the mucosa
-microvilli tiny projections of the plasma membrane
regulation of pancreatic juice and bile secretion and release- 1
-chyme entering duodenum causes duodenal enteroendocrine cells to release CCK and secretin
-CCK and secretin enter the bloodstream
regulation of pancreatic juice and bile secretion and release- 2
-upon reaching the pancreas, CCK induces secretion of enzyme-rich pancreatic juice
-secretin causes secretion of biocarbonate-rich pancreatic juice
regulation of pancreatic juice and bile secretion and release- 3
-secretin causes the liver to secrete more bile
regulation of pancreatic juice and bile secretion and release- 4
-CCK stimulates the gallbladder to release stored bile
-stimuation by vagal nerve fibres causes weak contractions of the gallbladder
regulation of pancreatic juice and bile secretion and release- 5
-CCK causes the hepatopancreatic sphincter to relax, allowing bile and pancreatic juice to enter the duodenum
large intestine
-produces some B and K vitamins
-water, vitamins, ions and remaining water are absorbed
-remaining materials are eliminated via faeces (nutrients, bacteria, water, undigested food residues)
-goblet cells produce alkaline mucus to lubricate the passage of faeces
pancreas
-produces a wide spectrum of digestive enzymes that break down all categories of food
-alkaline fluid introduced with enzymes neutralizes acidic chyme coming from stomach
-produces insulin and glucagon hormones
liver
-digestive role is to produce bile
-bile leaves the liver through common hepatic duct and enters duodenum through the bile duct
what is bile? what does it do?
-conatains cholesterol, phospholipids and electrolytes
-bile emulsifies (breaks down) fats
gallbladder
-when no digestion is occurring, bile is stored in the gallbladder
-while in the gallbladder, bile is concentrated by the removal of water
-when fatty food enters the duodenum, the gallbladder spurts out stored bile
