Chapter 7 - Absorption of Toxicants

Question 1

What are some methods that a toxicant can enter to body after exposure?

Answer 1

• respiratory inhilation
• GI ingestion
• skin dermal

Question 2

What is the path of travel for toxicants once they enter the body?

Answer 2

1. toxicant
2. respiratory system
3. GI system
4. skin (integumetary)

Question 3

Entry point for toxic gases, solvents aerosols, and particulates

Answer 3

respiratory system

Question 4

Has a large surface area,

Answer 4

GI system

Question 5

Not highly permeable to most water-soluble chemical, but lipid soluble compounds are well absored via passive diffusion.

Answer 5

skin (integumentary)

Question 6

composed of phospholipid bilayer approximately 7-9nm thick

Answer 6

cell membranes

Question 7

What function do most proteins have on a cell membrane?

Answer 7

structural, receptor, and enzymatic

Question 8

What is the primary mechanism for movement of toxicants across a cell membrane?

Answer 8

simple diffusion

Question 9

What factors can affect net diffusion?

Answer 9

• molecule size
• charge

Question 10

Which proteins are particularly selective to size?

Answer 10

channel proteins

Question 11

Which kind of membrane protein takes part in facilitated diffusion?

Answer 11

integral membrane protein

Question 12

What does facilitaed diffusion typically transport across the membrane?

Answer 12

glucose

Question 13

What is the driving force behind simple and facilitated diffusion?

Answer 13

concentration gradient

Question 14

What kind of transport is very specific and uses ATP to bring molecules against the concentration gradient?

Answer 14

active transport

Question 15

How is active transport driven?

Answer 15

phosphorylation and ATP binding

Question 16

How can a cell bring in molecules into the cell via vesicles formed from the plasma membrane?

Answer 16

endocytosis

Question 17

Why is endocytosis used as a mode of transport into the cell?

Answer 17

it can bring in large toxins

Question 18

What is the outer layer of the skin called?

Answer 18

stratum corneum

Question 19

What are the degrees of absorption for the GI tract?

Answer 19

• site
• pH
• time
• physiochemical properties

Question 20

Why is absorption through the GI tract considered systemic?

Answer 20

it can cause toxicants to travel throughout the whole body

Question 21

Where is absorption poor during absorption through the GI tract?

Answer 21

oral and esophagus

Question 22

Where can toxicants accumulate in the GI tract?

Answer 22

liver

Question 23

How does the liver remove toxicants?

Answer 23

• venous blood
• excreted into bile
• metabotically converted
• stored

Question 24

What is the process of bile being reabsorbed in the small intestine via the hepatic portal vein?

Answer 24

enterhepatic circulation

Question 25

What are the different levels of the respiratory tract where toxicants can be absorbed?

Answer 25

1. nasopharyngeal 2. tracheobronchial 3. alveolar 4. lymph | less and less absorbed as you go down

Question 26

How is the respiratory tract efficient in transporting toxicants?

Answer 26

it is quick, lipophilic and low-molecular weight gases are quickly absorbed (lipophilicity) | hydrophilic chemicals rate of absorption increases with size

Question 27

What are some examples of rapidly absorbed compounds absorbed through the respiratory tract?

Answer 27

- nitrous oxide - hydrocyanic acid - ether - chloroform

Question 28

lipophilic: higher the rate ____ the absorption hydrophilic: higher the size ____ the absorption

Answer 28

greater; lower

Question 29

What kinds of substances can stay in the lungs for a long period of time?

Answer 29

asbestos and coal dust

Question 30

Material that remains in the respiratory tract can produce local toxicity in the forms of...

Answer 30

- lung cancer - chronic bronchitis - lung fibrosis - emphysema

Question 31

For females ____L of lung capacity volume is standard.

Answer 31

2.5

Question 32

What do all the models of disposition integrate?

Answer 32

- distribution - metabolism - elimination

Question 33

Which model is represented? Toxicant is introduced to the body and transported to a single homogenous compartment

Answer 33

one-compartment model

Question 34

What is the most common compartment model system?

Answer 34

two or greater compartment models

Question 35

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.

Answer 35

two compartment model

Question 36

What is half-life?

Answer 36

time required to reduce the blood or plasma concentration by 50%