The GI Tract Flashcards
What is our main source of energy?
calories
What are carbohydrates?
our primary fuel source
What are the two things we can do with carbohydrates?
- burn in mitochondria for ATP
- store as fat for later
What are fats used for?
energy storage
Are fats more efficient than carbs and proteins? By how much?
yes, they are! they are 2x as efficient
What are the three overarching essential ingredients we need to function?
- protiens
- vitamins
- minerals
What are proteins used for?
to break down into amino acids
How many amino acids can your body make?
11/20, so the rest you have to eat
What are vitamins?
organic substances that CAN’T be made by the body
What are minerals?
inorganic substances that CAN’T be made by the body
What is the GI tract?
digestive system (mouth to anus)
What do accessory organs do in the GI tract?
they help secrete enzymes that aide digestion
What are some accessory organs?
- liver
- gallbladder
- salivary gland
- pancreas
What is the lumen?
the hole running through the GI tract
What is the mucosa?
inner layer of the GI tract that secretes mucus, protects other layers, and absorbs nutrients
What type of tissue is the mucosa?
epithelial
What is the submucosa?
2nd innermost layer, that has lymphatic, nerve, and blood vessels
What type of tissue is the submucosa?
connective
What is the muscularis layer?
the 3rd innermost layer that has circular and longitudinal muscles for pushing food down
What type of tissue is the muscularis layer?
smooth muscle tissue
What is the serosa?
outermost layer, protects tract from the outside
What type of tissue is the serosa?
epithelial
What is the beginning of digestion?
when salivary glands secrete enzymes
What if you have no teeth for food breakdown?
no problem, some birds swallow pebbles and do the mechanical breakdown in their gizzard
What is the salivary gland controlled by?
your brain
How does swallowing start and end?
it starts voluntary and ends involuntary
What does the esophagus do?
connects pharynx to stomach
What happens to the esophagus when you swallow?
your brain tells the esophagus to send one way waves to move food downwards
What is a sphincter?
openings that let food in and then close itself, so that food doesn’t travel backwards
What is the entrance to the stomach from the esophagus?
the esophageal sphincter
What happens in the stomach to the food?
gastric juices mix with food
What does HCl do in the stomach and where does it come from?
it creates the low pH environment in the stomach and it is secreted from the parietal cells
What other gastric molecule is in the stomach?
pepsinogen
Is pepsinogen active or inactive?
inactive, the stomach keeps it that way until the food arrives because you don’t want to digest your own stomach
How is pepsinogen turned active?
when our stomach becomes acidic by the HCl and pepsinogen turns into pepsin
What cells does pepsinogen come from?
chief cells
Does the stomach absorb nutrients from the food?
no, that happens in the small intestine
What are the three parts of the small intestine?
- duodenum
- jejunum
- ileum
What does the duodenum do?
fats are broken down here with accessory organs pancreas and gallbladder
What does the jejunum do?
this is where absorption officially starts
What does the ileum do?
absorbs more nutrients
Is the small intestine small?
nope, it has a huge surface area and it’s about the size of a tennis court
What do the villi and microvilli do?
hair like structures in the small intestine that increases absorption and it is called the “brush border”
What are proteins and carbs broken down by?
the brush border enzymes
Where do the broken down proteins and carbs go?
they are transported into cells and then into the blood stream
What emulsifies fats in the small intestine?
bile salts
What enzymes break down the fats into fatty acids?
lipase enzymes
What happens to the fats after breakdown?
it diffuses across the membrane and is packed into transport proteins
What are chylomicrons?
transport proteins that fatty acids are packed into
Where does the fatty acid enter?
the lymph system first and then the circulatory system
What does the pancreas do for the small intestine?
secretes enzymes “pancreatic juice” into the duodenum via the pancreatic duct
What are some enzymes that the pancreas secretes?
bicarbonate, trypsin, amylase, and lipase
What does bicarbonate do?
neutralizes stomach acids (after the food enters the small intestine)
What does trypsin do?
aids with digestion
Is trypsin stored actively or inactively?
inactively
What kind of environment is amylase and lipase activated by?
basic (alkaline) environment
Before the nutrients get distributed throughout the body, what must they pass through first?
the liver
What is the main function of the liver?
detoxification
What does the liver regulate?
glucose levels
If there’s too much glucose, what does the liver do?
make glycogen
If there’s too little glucose, what does the liver do?
break down glycogen
What else does the liver do?
makes plasma proteins and filters dead bile pigments
What is the large intestine also called?
the colon
How large is the large intestine compared to the small one?
shorter but wider than the small intestine
What does the colon do?
absorbs the last of the water, electrolytes, and vitamin k & compacts feces
What is attached to the colon?
cecum and appendix
Do we have a cecum?
no
What does the cecum do?
helps digest cellulose
What 2 sphincter muscles control the rectum?
a voluntary and involuntary muscle
What is feces composed of?
water, mucus, bacteria. and bile pigments
What do herbivores have in order to digest cellulose?
longer digestive tracts and a longer cecum
What do ruminants have to help digest cellulose?
4 chambered stomachs
What doe carnivores have because they don’t really eat plants?
shorter intestinal tracts (also because they chan tear and chew food)
What is coprophagy?
when animals eat feces to absorb more nutrients
What does ghrelin do?
stimulates hunger and feeding and it is released from the stomach to the brain
What does leptin do?
tells CNS to limit food intake (high body fat=high levels of leptin)
What is BMR?
calories needed by your body to perform basic functions
What is the difference between Calorie and calorie?
Calorie = kcal
calorie = cal
When does transition between voluntary to involuntary digestion occur?
when the food goes from the oral cavity to the pharynx
How does swallowing affect breathing?
you momentarily hold your breath, when swallow, to close the airway so that food doesn’t go to your lungs
What is peristalsis?
the motion of moving food down your esophagus
Where are the bile salts made and stored?
made in the liver but stored in the gallbladder
What is gastrin?
hormone that stimulates the secretion of gastric juices into the stomach
What cells does gastrin target?
it targets chief and parietal cells because they’re the ones that secrete HCl and pepsin
What is CKK and what does it do?
it is a hormone that stimulates the release of pancreatic juices
What does GIP do?
it’s a hormone that responds to ingestion of glucose (it increases intake and absorption of nutrients)
What is secretin and what does it do?
regulates and secretes bicarbonate into the duodenum
