Chapter 7 - Absorption of Toxicants Flashcards
What are some methods that a toxicant can enter to body after exposure?
- respiratory inhilation
- GI ingestion
- skin dermal
What is the path of travel for toxicants once they enter the body?
- toxicant
- respiratory system
- GI system
- skin (integumetary)
Entry point for toxic gases, solvents aerosols, and particulates
respiratory system
Has a large surface area,
GI system
Not highly permeable to most water-soluble chemical, but lipid soluble compounds are well absored via passive diffusion.
skin (integumentary)
composed of phospholipid bilayer approximately 7-9nm thick
cell membranes
What function do most proteins have on a cell membrane?
structural, receptor, and enzymatic
What is the primary mechanism for movement of toxicants across a cell membrane?
simple diffusion
What factors can affect net diffusion?
- molecule size
- charge
Which proteins are particularly selective to size?
channel proteins
Which kind of membrane protein takes part in facilitated diffusion?
integral membrane protein
What does facilitaed diffusion typically transport across the membrane?
glucose
What is the driving force behind simple and facilitated diffusion?
concentration gradient
What kind of transport is very specific and uses ATP to bring molecules against the concentration gradient?
active transport
How is active transport driven?
phosphorylation and ATP binding
How can a cell bring in molecules into the cell via vesicles formed from the plasma membrane?
endocytosis
Why is endocytosis used as a mode of transport into the cell?
it can bring in large toxins
What is the outer layer of the skin called?
stratum corneum
What are the degrees of absorption for the GI tract?
- site
- pH
- time
- physiochemical properties
Why is absorption through the GI tract considered systemic?
it can cause toxicants to travel throughout the whole body
Where is absorption poor during absorption through the GI tract?
oral and esophagus
Where can toxicants accumulate in the GI tract?
liver
How does the liver remove toxicants?
- venous blood
- excreted into bile
- metabotically converted
- stored
What is the process of bile being reabsorbed in the small intestine via the hepatic portal vein?
enterhepatic circulation
What are the different levels of the respiratory tract where toxicants can be absorbed?
- nasopharyngeal
- tracheobronchial
- alveolar
- lymph
less and less absorbed as you go down
How is the respiratory tract efficient in transporting toxicants?
it is quick, lipophilic and low-molecular weight gases are quickly absorbed (lipophilicity)
hydrophilic chemicals rate of absorption increases with size
What are some examples of rapidly absorbed compounds absorbed through the respiratory tract?
- nitrous oxide
- hydrocyanic acid
- ether
- chloroform
lipophilic: higher the rate ____ the absorption
hydrophilic: higher the size ____ the absorption
greater; lower
What kinds of substances can stay in the lungs for a long period of time?
asbestos and coal dust
Material that remains in the respiratory tract can produce local toxicity in the forms of…
- lung cancer
- chronic bronchitis
- lung fibrosis
- emphysema
For females ____L of lung capacity volume is standard.
2.5
What do all the models of disposition integrate?
- distribution
- metabolism
- elimination
Which model is represented?
Toxicant is introduced to the body and transported to a single homogenous compartment
one-compartment model
What is the most common compartment model system?
two or greater compartment models
What model is represented?
Toxicant is distributed through the blood (central comp.) into a periphreal compartment where it can be eliminated or returned back to the blood.
two compartment model
What is half-life?
time required to reduce the blood or plasma concentration by 50%
