Unit 2: Food Intake, Digestion, and Absorbtion Flashcards
The chemical structures of macronutrients is fairly large and we must break them down into more ___________ units in order for them to be absorbed by the body.
Soluble: disposed to being dissolved
General Circulation
the flow of blood throughout the entire body
Monosaturated Fat
A fatty acid containing one double or triple bond between carbons
Most ______ become fatty acids
triglycerides: a compound with three molecules of fatty acid bound with one molecule of glycerol.
What is the major storage fat in humans?
triglycerides
Gastrointestinal (GI) Tract
tract pertaining to the stomach and intestines
Calories
Any of several units of heat defined as the amount of heat required to raise the temperature of 1 kilogram of water by 1 degree Celsius (equal to 4.184 Joules)
How are macronutrients able to provide energy?
macronutrients contain a host of special chemical bonds that link carbon with hydrogen molecules. In the presence of specific enzymes, these carbon-hydrogen bonds are broken in a controlled manner. When these bonds are broken, energy is released.
What is the energy released from the break down of macronutrients used for?
To join to key energy mediators together – free adenosine diphosphate (ADP) and phosphate (P)
What do we get when join adenosine diphosphate (ADP) and phosphate (P) together?
adenosine triphosphate (ATP)
What is ATP used for?
things like muscle contraction and nutrient uptake into the cells
Adenosine Diphosphate (ADP)
a nucleotide made up of adenosine and 2 phosphate groups, produced in living cells, reversibly renewed to ATP for the storing of energy
Adenosine Triphosphate (ATP)
a nucleotide made up of adenosine and 3 phosphate groups. The breakage of one phosphate group (forming ADP) provides energy for physiological processes such as muscular contraction
Where does the digestive process begin?
the mouth with the process of mastication (chewing)
Bolus
a formed mass of soft, partially chewed food mixed with fluid secretions
What does the process of chewing trigger?
appearance of specific acids, mucus, enzymes, and bile, all secreted by the stomach and a number of supporting organs
Bile
fluid produced by the liver and stored in the gallbladder, ultimately secreted into the smaller intestine to alkalinize and emulsify foodstuffs
Where does the nutrients released during the breakdown process travel?
small intestine
In the small intestine, how is the nutrients absorbed?
specific intestinal cells called enterocytes
Why does digested food travel slowly through the intestines?
to give the GI system ample time for the nutrients to come in contact with the enterocytes so that the nutrients can be grabbed up and transported into the hepatic portal system
What is the hepatic portal system?
blood circulation from the GI tract to the liver
What can cause nutrients to pass through the intestinal tract unabsorbed and get excreted as waste later?
if digested food travels to quickly through the GI tract or the nutrients are bound to something like fiber
Where does the nutrients travel from the hepatic portal system?
liver
What is the liver’s role in this process?
it decides what to do with the nutrients before allowing them into general circulation
What is the main function of the mouth in the digestive system?
where food enters
What happens when we swallow?
food is passed onto the next digestive system
What is present in saliva?
digestive enzymes like amylase and lipase
Amylase
of pancreatic and salivary origin, this enzyme catalyzes the hydrolysis of starch into smaller compounds
Lipase
catalyzes the splitting of fats into glycerol and fatty acids
What happens once food is turned into a bolus?
the bolus is passed to the pharynx under voluntary control (although the process of swallowing is actually involuntary)
What happens during swallowing?
the epiglottis is involuntarily closed to prevent food from entering our trachea
What transports food and water from the mouth to the stomach?
esophagus
What does the lower esophageal sphincter (or cardiac sphincter) do?
regulate food entry into the stomach. Specifically, this muscle prevents food and stomach juices from re-entering the esophagus
Other than gravity, what helps move your food through the esophagus?
peristalsis - waves of involuntary muscle contractions moving the contents forward
What is the stomach responsible for?
first major wave of digestion
What does the stomach do to the bolus?
breaks it down into smaller pieces called chyme
Chyme
partly digested food formed as a semi-fluid mass
Where is the stomach?
between your esophagus and your small intestine. sits in the upper part of your abdomen, slightly to the left
What are the 3 divisions of the stomach?
fundus, body and antrum. fundus = first part just beyond esophagus. body = central part. antrum = lower part
pyloric sphincter
lies at end of antrum, regulates the passage of chyme into the smaller intestine
how many layers of the stomach wall?
4
Name the layers of the stomach.
first main layer = gastric mucosa. 2nd layer = submucosa. 3rd layer = muscularis externa. final layer = serosa
Gastric Mucosa
First main layer of the stomach that has cells that secrete most of the gastric juices (main acid = HCl). Contains chief cells and parietal cells
chief cells
secrete the enzymes of gastric juice
parietal cells
secrete HCl acid and intrinsic factor (IF)
What is IF essential for?
vitamin B12 absorption
submucosa
2nd layer of the stomach that consists of fibrous connective tissue designed to join the gastric mucosa and the muscularis externa
muscularis externa
third layer of the stomach that contains a host of smooth muscle fibers that run circularly in order to squeeze food through the stomach toward the small intestine
serosa
fourth and final layer of the stomach. connective tissue layer that connects the muscularis externa with the abdominal peritoneum, a membrane that covers most of the intra-abdominal organs
What is the point of the HCl and high acidity of the stomach?
helps breakdown of food, it also helps destroy a majority of the pathogenic bacteria swallowed with food and mucus
How long does it take for the chyme to empty from the stomach?
1 - 4 hours. Chyme moves slowly from the stomach
What order do the macronutrients leave the stomach?
carbohydrates empty first, then proteins and then fiber and fat last
what is the small intestine responsible for?
receiving chyme from the stomach and beginning the absorptive process
