Digestion Flashcards
what is the pathway food takes through the gastrointestinal tract?
mouth -> pharynx -> esophagus -> cardiac sphincter -> stomach -> pyloric sphincter -> small intestine -> large intestine -> rectum -> anus
how long is the digestive system?
between 6.5m and 9m
what are the accessory organs?
- pancreas
- gall bladder
- liver
- organs that are along the digestive tract but that food does not pass through
how long does it take to go from one end of the tube to the other?
24-72 hours
what are the 4 steps of digestion?
- Ingestion
- Digestion
- Absorbtion
- Egestion
what is ingestion?
the taking of nutrients (eating)
what is digestion?
the breakdown of organic molecules into smaller complexes
what is absorption?
the transport of digested nutrients to the tissues of the body
what is egestion?
the removal of materials from the food that the body cannot digest (pooping)
what is mechanical digestion?
- breaking food into tiny pieces without changing the chemical structure of the food
- increases the surface area to expose the nutrients to the digestive chemicals
- AKA. chewing
what is chemical digestion?
food molecules are broken into smaller and smaller particles using enzymes (bonds are broken)
what does starch get broken down to?
monosaccharides
what does protein get broken down to?
amino acids
what do lipids get broken down to?
fatty acids and glycerol
what is the function of the mouth?
- the first step of mechanical digestion
what is mastication?
chewing your food
what is chewed food called?
bolus
how does taste work?
- our tongue is covered with tastebuds
- these identify the tastes of specific chemicals in our food with the help of our nose
what is the pharynx?
- intersection for nose, mouth, esophagus, epiglottis and trachea
- AKA. throat
what is the esophagus?
a long tube lined with muscle
what is the function of the esophagus?
the muscle pinches to push the food down to the stomach
what is peristalsis?
muscular contractions and relaxations that push food down to the stomach
what does the cardiac/esophageal sphincter do?
regulates how many bolus enter the stomach at a time
why does the lower esophageal sphincter relax at the bottom of the esophagus?
so that no food can travel from the stomach back up the esophagus
what is an esophageal ulcer?
when stomach acid burns a hole in the esophagus
what is heartburn?
when the bolus/stomach acid moves backward toward the heart causing a burning sensation in the esophagus
what does the pyloric sphincter do?
controls how much food enters the small intestine
what is the structure of the stomach?
- it is a J-shaped sack like organ
- 50mL –> 2L –> 4L
what is the function of the stomach?
- storage
- digestion (mechanical + chemical)
- pushes food to the small intestine
- produces pepsin, HCl and mucus
- digests proteins
what macromolecule gets digested in the mouth?
starches into monosaccharides
what macromolecule gets digested in the stomach?
proteins into amino acids
what do peptic cells do?
secretes pepsinogen (inactive enzyme), which mixes with HCl to create pepsin (active enzyme), the pepsin then breaks down the proteins
what is the pH of the stomach?
1-3
what do parietal cells do?
- secretes HCl
- maintains stomach pH
- kills bacteria
- activates pepsinogen into pepsin
which cell secretes pepsinogen?
peptic
which cell secretes HCl?
parietal
what do mucus cells do?
secrete mucus to make stomach lining
how often are the stomach cells destroyed and remade?
every 3-4 days
what does gastric juice consist of?
water, mucus, salts, HCl and enzymes
what is chyme?
- liquified food + gastric juices
- what the stomach releases to the small intestine
what does the pancreas do?
- produces digestive enzymes
- continues the digestion of starches, lipids and proteins
what does the liver do?
- produces bile and send it to the gall bladder for storage
- stores glycogen
- detoxifies many substances in the body
what does the gall bladder do?
stores + releases bile
what is bile?
grinds lipids to small pieces (fatty acids + glycerol)
what is the structure of the small intestine?
- small tube made of smooth muscle
- smaller in diameter than the large intestine
what are villi?
finger-like projections in the membrane of the small intestine
what is the function of the small intestine?
the absorption of monosaccharides, fatty acids +glycerol and amino acids
what does the large intestine do?
- pushes undigested food/waste/feces to the rectum
- absorbs water back into the body
what are the three segments of the small intestine?
- duodenum
- jejunum
- ileum
what is the function of the duodenum?
- receives chyme from the stomach
- most mechanical and chemical digestion occurs here
what is the function of the jejunum?
- continues the breakdown, most absorption occurs here
what is the function of the ileum?
absorbs nutrients and pushes undigested material to large intestine
what chemical digestion occurs in the duodenum?
enzymes break down carbohydrates
what hormones are released in the duodenum?
- secretin
- CCK
what are the two networks and where are they?
- in the small intestine
- capillary and lymph
what does the capillary network do?
absorbs amino acids and monosaccharides
what does the lymph network do?
absorbs fatty acids and glycerol
where are amino acids absorbed?
in the villi of the small intestine
where is glucose absorbed?
in the villi of the small intestine
what is the structure of the pancreas?
feather-like organ under the stomach on top of the small intestine
what is the structure of the liver?
has 4 lobes
what is the structure of the large intestine?
wider than the small intestine, but only about 1.5m long
what are the measurements of the small intestine?
7m x 2.5cm
what do hormones do?
control how we process, digest and absorb food
what does the colon do?
absorbs water and salts
what happens when we absorb too much water?
constipation
what happens when we don’t absorb enough water?
diarrhea
what does the rectum do?
receives and stores digested material before elimination
what does emulsify mean?
grinding into smaller pieces to increase surface area (bile)
