Absorption Flashcards
What is BIOACCESSIBILITY? What are the two sources for it?
The availability of a molecule to enter an organism from the environment.
- The organism has access to the molecule
- Environmental pollution + biodegradation
While BIOAVAILABILITY is how much of a xenobiotic that gets into the body to the SOA, BIOACCESSIBILITY is the different _____ of the xenobiotic the body encounters. Give examples.
Forms
Prescription drugs, food alternative meds, cosmetic + household cleaners
What is the difference between BIOACCUMULATION and BIOMAGNIFICATION?
In both cases, toxic chemicals bond are stored in fatty tissues/organs instead of being secreted out in animals.
BIOACCUMULATION: takes place in a single organism over the span of its life. Older animals have a higher level of chemical.
BIOMAGNIFICATION; the toxic chemicals transfer from lower trophic levels to higher trophic levels within a food web, resulting in a higher concentration in predators.
What are the two routes of exposure/administration? How are they different? Give examples of both.
Enteral (alimentary) and Parenteral (extra-alimentary)
Enteral involves the gastrointestinal tract and is done through ORAL, SUBLINGUAL/BUCCAL, and RECTAL.
The parenteral involves substances unstable in the GI tract and is done through INJECTIONS, INHALATIONS, and TRANSDERMAL exposures.
(T/F) One of the advantages of parenteral exposure is that it has quick effects while a disadvantage is that it decreases the likelihood of getting the drug into the right tissue.
False, it has quick effects and it increases the likelihood of getting the drug into the right tissue because it is more precise.
What are the three physical factors that influence absorption of a xenobiotic? What do they all dictate?
- Substance properties
- Matrix properties
- Route of exposure/administration
Blood flow, surface area and contact time.
The greater the blood flow, the _____ the absorption of a drug. The greater the surface area and time for absorption, the _______ the absorption.
Greater; greater
Pick one from each pair in where a greater absorption of a xenobiotic would occur and briefly explain why:
- Intestine vs subcutaneous tissue
- Intestine vs stomach
- Greater absorption in intestine than subcutaneous tissue because HIGHER BLOOD FLOW. Organs that need more oxygen have a higher blood flow.
- Intestine has a LARGER surface area which also means LARGER CONTACT TIME, so greater absorption in intestine than stomach.
*residence time in intestine is 4-8 times longer than stomach
What are the five elements of the digestive system? Briefly explain them.
- Digest - break molecules into small molecules
- Secrete - active release of a substance
- Absorb - movement of nutrients into stomach from GI tract or intestinal cells after digestion
- Excrete - elimination of non-absorbed or metabolic wastes
- Protect
The gastrointestinal tract is a flexible muscular tube extending from the _______ to the ______ that is surrounded by the body. Many things pass through the GI tract without being absorbed and if they are not absorbed, they are not _____ our body.
Mouth; Anus; Inside
(T/F) The organisms that live in our digestive tract only have positive impacts on absorption and health.
False, can also have negative impacts.
What is the difference between Mechanical digestion
and Chemical digestion for ORAL (enteral) drugs?
Mechanical digestion begins in the mouth where molecule is broken into smaller pieces to increase SA with water added to it. Then, peristalsis lubricates food and moves it into stomach. NO change in chemical nature of drug.
Chemical digestion also begins in the mouth through the saliva’s enzymes. Digestive “juices” break down complex drug molecules into their chemical building blocks. Process is completed in the small intestine.
Match the following terms regarding digestive “juices.”
- Saliva
- Gastric juice
- Bile
- Pancreatic juice
- Epithelial cell secretions
A. in STOMACH made up of water, mostly PROTEASES and HCL to break down food. Protected by gastric mucosa.
B. in the INTESTINE produced by liver and released by gall bladder. Acts as a EMULSIFIER (e.g. micelles of lipophilic molecules created in an aqueous env are broken down to be absorbed by epithelial cells).
C. made of enzymes
D. in the MOUTH with a slightly basic pH that neutralizes acid. Has AMYLASE and LIPASE.
E. in the INTESTINE with enzymes and bicarbonate
Saliva - in the MOUTH with a slightly basic pH that neutralizes acid. Has AMYLASE and LIPASE.
Gastric juice - in STOMACH made up of water, mostly PROTEASES and HCL to break down food. Protected by gastric mucosa.
Bile - in the INTESTINE produced by liver and released by gall bladder. Acts as a EMULSIFIER (e.g. micelles of lipophilic molecules created in an aqueous env are broken down to be absorbed by epithelial cells).
Pancreatic juice - in the INTESTINE with enzymes and bicarbonate
Epithelial cell secretions - made of enzymes
Small intestine is the _______ site of chemical absorption, while large intestine is the ________ site of chemical absorption.
Primary
Secondary
Nutrients and xenobiotics reach the blood and lymph via the intestinal _______ cells.
Epithelial
What are the four ways xenobiotics reach the blood and lymph via epithelial cells?
1) Transcellular
2) Paracellular
3) Transcytosis
4) Absorption into lymph
Match the following terms to their definitions regarding chemical absorption:
1) Transcellular
2) Paracellular
3) Transcytosis
4) Absorption into lymph
A. receptor mediated endocytosis where the molecule is released on the other side of the cell. Limited by size, lipophilicity and SA.
B. molecules (usually lipophilic) pass through epithelial cells using active/passive transport
C. done via M-cells pd Peyer’s.
D. molecules transfer across an epithelium by passing through the intercellular space (cracks) between the cells. Limited by size and lipophilicity (small + polar)
Transcellular - molecules (usually lipophilic) pass through epithelial cells using active/passive transport
Paracellular - molecules transfer across an epithelium by passing through the intercellular space (cracks) between the cells. Limited by size and lipophilicity (small + polar)
Transcytosis - receptor mediated endocytosis where the molecule is released on the other side of the cell. Limited by size, lipophilicity and SA.
Absorption into lymph - done via M-cells pd Peyer’s.
Unabsorbed materials in the small intestine is partially or completely absorbed by _______ in the large intestine. The remaining unabsorbed is ______.
Microflora
Feces
Match the transit time of a xenobiotic according to the organs:
- less than a minute
- 1-2 hours
- 7-8 hours
- 12-14 hours
A. small intestine
B. large intesine
C. mouth
D. stomach
Less than a minute - mouth
1-2 hours - stomach
7-8 hours - small intestine
12-14 hours - large intestine
First pass metabolism includes the HEPATIC PORTAL SYSTEM, what are the four steps of it?
- Small intestine absorbs products of digestion
- Nutrient molecules travel in hepatic portal vein to liver
- Liver monitors blood content
- Blood enters general circulation
Briefly describe first pass metabolism and how it reduces BIOAVAILABILITY.
First pass metabolism is a process where a drug administered by the MOUTH (oral) is absorbed from the GI tract (small intestine) and is transported to the LIVER via the HEPATIC PORTAL VIEN where it is metabolized. The drug is metabolized into its inactive forms, reducing the bioavailability by causing only some of the active drug to reach the SOA.
