What are the 3 main building blocks that food is broken down to?
- 1. simple sugars
- 2. amino acids
- 3. lipids
What are the 3 different types of enzymes used in the chemical breakdown of food? What do each type break down?
- Amylase: from our saliva, breaks down starch
- Protease: breaks down protein
- Lipase: breaks down fats
Why are fats hard to break down and what does the liver secrete to aid in the breakdown of fats?
- Once fats are broken apart, they clump up together again easiliy.
- Bile is secreted from the liver, which contains bile salts to help prevent fats from clumping up together again.
T or F: The pancreas and liver are considered accessory organs. What does this mean?
True: They aid in the digestion of food but are not part of the digestive tract
What is the inner layer of the GI tract and what is it compposed of?
Mucosa called the Lamina Propria: Epithelium + Loose CT
This layer of the GI tract is a thick layer of CT that provides it with its elasticity. What does it contain?
Submucosa: larger blood and lymph vessels, and the submucosal plexus (a nerve network)
What is the layer external to the submucosa? What does it consist of?
- Muscularis Externa:
- Circular layer
- Longitudinal layer
What are the 2 neuron networks within the walls of the GI tract?
- 1. Submucosal Plexus of Meissner
- 2. Myenteric Plexus of Auerbach
What do chemoreceptor and mechanoreceptors do for our digestive tract?
- Chemoreceptor: (3 parts)
- i. tells what subtrates are needed for digestion
- ii. what the products of digestion are
- iii. detects pH
- Mechanoreceptors: detecting stretch to tell if something is there
These are the cells in the digestive tract that release hormones.
T or F: Long reflexes are actions in the body that do not involve the brain
How much can our stomach store? What is food named as it enters and exists our stomach?
- 1 Gallon:
- i. Food first entering the stomach is called fundus.
- ii. Food then gets turned into a paste, called Chyme.
- iii. Once it exists the stomach
- it is called Pyloris
How is protein broken down?
- Digestion occurs in the stomach by using HCl and pepsin.
- HCl can bring pH down to 2, and activates pepsinogen into pepsin.
What do Chief cells, parietel cells and enteroendocrine cells secrete?
- Chief cells: pepsinogen
- Parietel cells: HCl and intrinsic factors
- Enteroendocrine cells: Gastrin
What are intrinsic factors and which cell secretes them?
Parietel cells: They are needed to absorb vitamin B12, necessary to make RBCs
What does Gastrin do what secretes it?
Enteroendocrine cells: stimulates gastric secretion
What are the 3 cells that compose of the Gastric Glands?
- Chief cells
- Parietel Cells
- Enteroendocrine cells
What are the 3 ways we do not digest ourselves from gastric juices?
- 1. A thick layer of mucus above the gastric pits, pepsin is inhibited by when in contact with mucus
- 2. Produce enzymes in inactive precursor forms
- 3. High rate of epithelial regeneration along digestive tract
How do contractile cells help with GI tract regeneration?
They fill up the holes of cells that die so there are no holes in the wall
What are the 3 phases of gastric secretion?
- 1. Cephalic Phase: An example of "feed forward mechanism"
- Thinking about eating something, especially when excited or chewing a lemon and saliva is produced.
- 2. Gastric Phase: When Food is swallowed
- Triggered by stretch of stomach and pressence of actual molecules
- Moves the ood up and down the stomach, releasing a bit of pyloris at a time
- 3. Intestinal Phase: released into the small intestine
This Gastric secetion phase can both inhibit or increase gastric emptying. What is an example of when it inhibits gastric emptying?
Intestinal phase: eating fatty foods are harder to break down so it requires longer in the stomach to do this.
What is the sphincter between the stomach and small intestine?
What is the first part of the small intestine and what is its significance?
Duodenum: it is where bile from the gall bladder and pancreatic juices get secreted into
What does the pancreas secrete to aid in digestion? Where does it get released into?
- Makes HCO3- to neutralize acid from stomach
- Enzyme Juice: proteases, lipases, nucleases, amylases
What are the hormones that tells the gallbladder and pancreas to secrete their juices?
- Secretin: tells pancrease to secrete HCO3- Juice
- CCK: (cholecystokinin) tells pancreas to secrete enzymes and gallbladder to deliver bile.
What is the 2nd part of the small intestine, after the duodenum, and what occurs here?
Jejunum: main site of breakdown and absorption
What is the last part of the small intestine and what occurs here?
Ileum: reclaims bile salts