-
epithelial tissue
cells that cover surfaces inside and outside the body
-
connective tissue
support and protect the body by holding structure together
-
muscle tissue
contract and relax to permit movement
-
nervous tissue
transmit nerve impulses
-
What are the parts of the GI tract?
- mouth
- esophagus
- stomach
- small intestine
- large intestine
-
digestion?
mechanical/chemical processes of breaking down food into smaller components
-
absorption?
uptake of nutrients from the GI tract into the blood or lymph
-
what is peristalsis?
waves of contraction that propels material along the GI tract
-
what is segmentation?
back and forth action that breaks food apart
-
what is mass movement?
peristaltic wave that contracts over a large area of the large intestine to help eliminate waves
-
what are the 4 parts to GI motility?
- peristalsis
- segmentation
- mass movement
- elimination
-
what is the alimentary canal?
- long hollow muscular canal from mouth to anus
- nearly 15 ft
-
What are the four layers of the alimentary canal?
- mucosa - epithelia cells and glands, innermost
- submucosa - CT and glands, contains blood vessels carrying nutrients to GI tract
- smooth muscle - moves food forward, longitudinal and circular
- serosa - outside layer that protects the tract, secretes lubricating fluid to keep it cushioned
-
what are sphincters
- ring link muscles that control the flow of contents in the GI tract
- open and close valves to control flow of contents
-
what are the 5 sphincters
- lower esophageal sphincter
- pyloric sphincter
- hepatopancreatic sphincter
- ileocecal valve
- anal sphincter
-
lower esophageal sphincter?
- prevents back glow of stomach contents into the esophagus (reflux)
- aka cardiac sphincter
-
pyloric sphincter
- control the flow of stomach contents into the small intestine
- only allows 1 tsp of chyme at a time into SI to neutralize the acid and digest nutrients
-
hepatopancreatic sphincter
- control the flow of bile and pancreatic juice from the common bile and pancreatic ducts into the small intestine
- aka sphincter of oddi
-
ileocecal valve
prevent the contents of the large intestine from reentering the small intestine
-
anal sphincter
prevent defecation until the person desires to do so
-
7 secretions that aid in digestion
- saliva
- mucus
- digestive enzymes
- hydrochloric acid
- bile
- bicarbonate ions
- hormones
-
saliva
- dissolves taste forming compounds
- aids in swallowing and digestion and protection of teeth
-
mucus
- protects GI tract cells
- lubricates digesting food
-
digestive enzymes
break down carbs, fats, and proteins small enough for absorption
-
hydrochloric acid
- promotes digestion of protein
- destroys microorganisms
- increases solubility of minerals
-
bile
aids in fat digestion (emulsifies fat)
-
bicarbonate ions
neutralizes stomach acid when it reaches the small intestine
-
hormones
regular food intake, digestion, and absorption
-
-
what are the 4 components of saliva
- lysozyme - breaks down bacteria
- mucus - lubricates and holds bolus together
- amylase - breaks down starch, only 5%
- lingual lipase - initiates fat digestion
-
the 5 tastes we can taste from our taste buds
- salty - from metal ions
- sour - from acids
- sweet - from organic compounds like sugar
- bitter - from many groups, caffeine, plants
- umami - savory tastes from amino acids and MSG
-
what does swallowing do
moves bolus from mouth to esophagus
-
purpose of epiglottis
prevents food from lodging in the trachea by covering larynx
-
muscles that make up esophagus
- circular muscles
- longitudinal muscles
- relax and contract to move food along
-
bolus + stomach secretions =
chyme
-
what do parietal cells secrete?
- Hcl
- intrinsic factor (IF)
-
what does hydrochloric acid do? (4 things)
- destroys bacteria and viruses
- inactivates proteins (such as plant and animal hormones to prevent them from affecting human functions)
- inhibits salivary amylase
- converts pepsinogen into active form of pepsin
-
what does IF (intrinsic factor) do?
binds to B12 and aids in its absorption
-
what do chief cells secrete?
- pepsinogen (the inactive enzyme)
- gastric lipase
-
pepsinogen
- turns into the enzyme pepsin by Hcl, which breaks down proteins into AA chains
- first location of protein digestion
-
gastric lipase
enzyme that breaks down lipids
-
what do mucous neck cells secrete?
mucus
-
What does mucus do?
protects stomach from being digested
-
production of mucus relies on?
presence of prostaglandins
-
why is heavy use of aspirin/NSAIDs bad?
inhibits prostaglandin production -> can damage the stomach
-
what do endocrine cells secrete?
gastrin
-
Gastrin
- stimulated by food, thoughts of food, and action potentials of autonomic nervous system
- stimulates secretion of pepsinogen and HCl
- stimulates contraction of lower esophageal sphincters
- slows gastric emptying
-
what does glucose-dependent insulinotropic peptide do?
slows down the release of chyme into the SI
-
what are the parts of the small intestine?
- duodenum (10 in)- primary site of digestion
- jejunum (4ft) - upper part of digestion, lower for absorption
- ileum (5ft)
-
brush border enzymes
enzymes produced in the small intestine
-
3 enzymes secreted by the small intestine?
- secretin
- cholecystokinin (CCK)
- gastric inhibitory peptide (GIP)
-
Secretin
- stimulated by presence of acidic chyme and presence of peptones in the duodenum
- stimulates secretion of pancreatic bicarbonate which neutralizes the HCl
-
Cholecystokinin (CCK)
- stimulate by food, presence of fat and protein in duodenum
- stimulates contraction of gallbladder and release of bile
- stimulates release of enzyme rich pancreatic fluids
-
Gastric Inhibitory Peptide (GIP)
- stimulated by fats and protein
- inhibits secretion of stomach acid and enzymes
- slows gastric emptying/motility
-
what is enterohepatic circulation
- recycling of bile
- bile is stored in the gallbladder until needed
- it is release into the duodenum and then reabsorbed in the ileum to be returned to liver
-
purpose of liver
- produces bile to aid in digestion and absorption of fat
- emulsifies fat
-
purpose of gallbladder
bile storage
-
purpose of pancreas
produces pancreatic juice to help break down large molecules
-
what enzymes does pancreatic juice contain
- sodium bicarbonate - neutralizes acidic chyme coming into SI to protect the SI from damage by the acid
- lipase - digest fat, break down large molecules
- proteases - digest protein, break large AA chains into smaller AA chains
- pancreatic amylase - digest starch and carbs
-
what do enzymes do
speed digestion by catalyzing chemical reactions
-
4 types of absorption
- passive diffusion
- facilitate diffusion - carrier proteins allows substances through membrane into cell
- active transport
- endocytosis - phagocytosis and pinocytosis
-
portal circulation - what gets absorbed and where
- water soluble nutrients (proteins, carbs, medium chain fatty acids, B vitamins, vitamin C)
- portal vein delivers nutrient rich blood to liver before going throughout the body
- it gives the liver a chance to process and store nutrients before being used (liver is main processing location in the body)
-
lymphatic circulation - what gets absorbed and where
- fat soluble nutrients (long chain fatty acids, fat soluble vitamins, large particles
- nutrients enter circulation at thoracic duct near the heart, far from the liver
-
3 main sections of the large intestine
-
5 parts of the colon
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
-
3 main functions of the large intestine
- houses gut microbiota to keep GI tract healthy
- absorbs water and electrolytes
- forms and expels feces
-
small intestine into large intestine through?
ileocecal valve
-
4 ways microbiota contribute to health
- protect against infection by pathogens (crowd them out, produce antimicrobial substances)
- synthesize vitamins to be absorbed in colon (especially vitamin K and biotin)
- digest and metabolize complex carbs/fibers/starches + form short fatty chain acids
- modulate information with metabolic products
-
dysbiosis
- imbalance between beneficial and pathogenic bacteria
- can cause GI infections
-
pro-biotic bacteria
- live bacteria that will colonize the LI
- found in fermented foods
-
pre-biotic bacteria
found in non digestible carbohydrates that promote growth of bacteria
-
what does the large intestine absorb
- water
- sodium
- potassium
- short chain FA
- vitamins produced by bacteria in LI
-
ulcer
- very small erosion of the top layer of cells in the stomach or duodenum
- aka peptic ulcer
-
causes of ulcers
- hub pylori bacteria (acid resistant) - weakness mucus coating that protects stomach + duodenum -> allows HCl + acids to erode the cells
- heavy use of aspirin, NSAIDs, alcohol, or smoking
-
treatments for ulcers
- antibiotics
- antacid
- medicines that reduce acid (pepsin)
-
treatments for heartburn
- smaller meals
- less fatty meals
- stop smoking
-
how can meds that reduce Hcl production in stomach be bad for you?
long term use decreases stomach acidity = Ca and Mg less well dissolved from food = decreased absorption of them = decreased bone mineralization process = increased risk of osteoporosis
-
nonalcoholic fatty liver disease
- liver cells store excess fat instead of metabolizing it -> swelling, inflammation, and scarring
- gradual weight loss and daily exercise can reverse the effects
-
Gallstones
develop in gallbladder when cholesterol in bile forms crystal-like particles
-
causes and treatment of constipation
- causes - low fiber diet (bc fiber helps stimulate peristalsis and forms soft feces). Antacids, calcium, iron supplements.
- treatment - plenty of dietary fiber and fluids, laxatives
-
enema
insertion of fluid into rectum -> stimulates the bowel -> liquid and feces are expelled
-
hemorrhoids
swollen veins of the rectum and anus
-
crohn’s disease
inflammation + ulceration extend through all layers of GI tract
|
|