digestive system Flashcards
Digestion
The chemical and mechanical breaking down of food molecules
digestive system
organs that collectively perform the breaking down of food
six essential activities of the digestive system
ingestion propulsion mechanical digestion chemical digestion absorption defecation
ingestion
bring in food
propulsion
mixing and moving food
mechanical digestion
break down into smaller pieces to aid chemical digestion
chemical digestion
acids and enzymes break food into monomers
absorption
absorb monomers into blood/lymph
defecation
eliminate unused material (feces)
Mechanoreceptors and chemoreceptors
Respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of digestion
Complex of nerves in the walls of GI tract
Mechanoreceptors and chemoreceptors Initiate reflexes that
Activate or inhibit digestive glands
Stimulate smooth muscle to mix and move lumen contents
Two Groups of organs of digestion
Gastrointestinal Tract (GI Tract)/Alimentary Canal Accessory Structures
Gastrointestinal Tract (GI Tract)/Alimentary Canal
Begins with mouth – ends at anus
Mouth, pharynx,esophagus,stomach,small intestine, large intestine
Accessory Structures
Teeth, tongue, salivary glands, liver, gall bladder, pancreas
Hepatic portal circulation
Drains nutrient-rich blood from digestive organs
Delivers it to the liver for processing
wall of GI tract 4 layers
mucosa
submucosa
mucularis
serosa and peritoneum
mucosa
inner lining,mucous membrane
Epithelium, lamina propria, smooth muscle (muscularis mucosae); functions to protect, secrete hormones, enzymes and lubricating mucus, and absorb nutrients.
lamina propia
propria contains capillaries to absorb and MALT (mucosa associated lymphatic tissue) for defense against infection
Submucosa
consists of areolar connective tissue that binds the mucosa to the muscle layer; gives elastic property to tract; contains chemoreceptors and mechanoreceptors
Muscularis
thick layer of muscle
Smooth muscle (3 layers) ,inner sheet of circular fibers and outer sheet of longitudinal fibers & nerves
Responsible for segmentation and peristalsis
Sphincters (timing, prevent backflow)
Serosa and Peritoneum
outermost layer
serosa
composed of simple squamous epitheleum and connective tissue Secretes serous (wet) fluid to allow the organs to glide
peritoneum
largest serous membrane.
Parietal – lines wall of abdominal cavity
Visceral – outer layer of some organs (all but retroperitoneal organs)
mesentary
double layer of peritoneum
Routes for blood vessels, lymphatics, and nerves
Holds organs in place and stores fat
binds small intestine to posterior abdominal wall
Retroperitoneal organs
lie posterior to the peritoneum
Intraperitoneal (peritoneal) organs
are surrounded by the peritoneum
Falciform ligament
attaches liver to anterior abdominal wall
Greater omentum
(fat skin) drapes over transverse colon and small intestine
Contains lymph nodes
Lingual Frenulum
mucous memb connects underside of tongue to floor over buccal cavity
papillae
line tongue on top and sides
Some contain taste buds
Parotid glands location
under and in front of ears
submandibular gland location
lies beneath base of tongue
sublingual gland location
lie in front of submandibular glands
Saliva
only .5% solutes
Water helps dissolve/mucous sticks it together
amylase, lysozyme
amylase function and location
digestive enzyme (carbs / starches) saliva
lysozyme function and lcoation
destroys bacteria to protect mucous membrane from infection and the teeth from decay
saliva
swallowing stages
voluntary stage
pharyngeal stage
esophageal stage
voluntary stage
bolus is forced by tongue to oropharynx
pharyngeal stage
(involuntary) breathing interrupted, soft palate closes nasopharynx, epiglottis closes off larynx, vocal cords close
esophageal stage
food pushed by peristalysis , circular muscles contract while longitudinal muscles relax
HCL can back up into lower esophagus, heartburn
cardia
surrounds superior opening of stomach
fundus
above and left of cardia on stomach
body
large central portion of stomach
pylorus
narrow inferior region of the stomach
pyloric sphincter
valve between pyloris and duodenum
stomach wall four layer modification
Rugae
Mucous surface cells line stomach (non-ciliated)
gastric pits are formed from epithelial cells
Gastric glands are located inside these pits
3 types of Exocrine gland cells compose this
chyme function and location
food mixed with the secretions of the gastric glands turned into a thin liquid
stomach
pepsin function and location
digestive enzymes that break down proteins in chmye (most effective in PH2)
stomach
what stimulates digestion
Distention (stretch), increase in pH, and presence of partially digested materials stimulate digestion to begin.
parasympathetic impulses promote peristalsis and stimulate glands to secrete
3 Phases of Gastric Secretion
Cephalic
gastric
intestinal
cephalic
salivating
gastric
stomach acids
intestinal
excitatory and inhibitory hormones control release of gastric juices
Enterogastric reflex
when chyme enters duodenum, a series of reflex reactions occur to inhibit acid secretion (hormones called enterogastrones)
Inhibition of digestion
presence of food in the small intestine inhibits parasympathetic stimulation and stimulates sympathetic activity. negative emotions (anger) may also slow down digestion
gastric inhibitory peptide
inhibits gastric secretion
secretin
decreases gastric secretion
cholecystokinin
(CCK) inhibits gastric emptying
Gastric emptying
release of chyme from the stomach into the duodenum
empties all contents of stomach w/in 2-6 hours of ingestion
regulated by nervous/hormonal controls
chyme does what for gastric emptying
chyme in duodenum generates reflex to slow gastric emptying
ranking of carbs proteins and fats in time in stomach
carbs spend the least time in the stomach
proteins spend longer time
Triglycerides (fats) spend the most time
pancreatic amylase
digests carbohydrates
in pancreas
trypsin/chymotrypsin function and location
digests proteins
pancreas
pancreatic lipase function and location
digests triglycerides
pancreas
ribonuclease/deoxyribonuclease function and location
digests nucleic acids
pancreas
Liver
produces bile, weighs about 3 pounds, located under the diaphragm-rt side of the body
divided into right and left lobes by the falciform ligament
lobes divided into lobules
sinusoids
sinusoids-capillary beds through which blood passes
lined with stellate reticuloendothelial cells that destroy worn out white and red blood cells, bacteria and toxic substances
Hepatocytes
produce bile
common bile duct
common hepatic duct joins the cystic duct
gall bladder
Located under liver
Functions in storage until needed in small intestine
Bile
Excretory product and digestive secrection
Salts aid in emulsification
Conversion of triglyceride globules into droplets and absorption of triglycerides following their digestion
Bilirubin
principal bile pigment
broken down into intestines and color of feces
functions of liver
Carbohydrate Metabolism Lipid Metabolism (store and break down) Protein Metabolism (synthesize and convert) Synthesis of Bile Storage – vitamins and minerals Phagocytosis Activation of Vitamin D
Carbohydrate Metabolism
convert glucose to glycogen when sugar level is high and breakdown glycogen to glucose when sugar is low
Duodenum length
10 inches
jejunum
Jejunum (1meter) means empty – more muscular and vascular than ileum; more villi and plicae circulares than duodenum
ileum
(2 meters) joins colon at Ileocecal junction
What is digested in the Sm. Int.?
Carbs, fats (bile needed)
Proteins continue to break down here (started in stomach)
Small intestine relies largely on the liver and pancreas to produce enzymes, bile, ions, etc., for digestion to occur
acessory organs
salivary glands
liver
gallbladder
pancreas
alimentary canal structures
mouth pharynx esophogus stomach small intestine large intestine rectum anus
