Phases of Toxic Phenomenon Exposure and Absorption
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Questions and Answers

Which factor is considered one of the most important for the likelihood of a xenobiotic being absorbed?

  • Body temperature
  • Time of day
  • Eye color
  • Route of exposure (correct)

    • What is necessary for a substance to exert an effect on internal organs?

  • Being in gaseous form
  • Absorption into the body (correct)
  • Ingestion of large quantities
  • Absence of local toxicity

    • Which of the following is NOT a primary route of exposure for xenobiotics according to the text?

  • Dermal (skin)
  • Respiratory
  • Gastrointestinal (GI) tract
  • Intramuscular (correct)

    • What is the absorbed dose in relation to the exposure dose for substances injected or implanted directly into the body?

    <p>The same</p> Signup and view all the answers

    Local toxicity, such as irritation, may occur even if a substance has not been:

    <p>Absorbed</p> Signup and view all the answers

    Why are xenobiotics often ranked for hazard according to the route of exposure?

    <p>Due to route-specific differences in absorption</p> Signup and view all the answers

    Which mechanism of transport requires cellular energy from ATP?

    <p>Active Transport</p> Signup and view all the answers

    What is a key difference between facilitated diffusion and simple diffusion?

    <p>Facilitated diffusion is carrier-mediated</p> Signup and view all the answers

    In endocytosis, what happens to the substance and section of the cell membrane after engulfment?

    <p>They move into the interior of the cell</p> Signup and view all the answers

    Which system is involved in draining excess fluid from tissues and is part of the circulatory system?

    <p>Lymphatic System</p> Signup and view all the answers

    Why can some large molecules and particles not enter cells via passive or active mechanisms?

    <p>They are too large to dissolve in the lipid layer</p> Signup and view all the answers

    Which type of cells benefit greatly from phagocytosis as a process of engulfing particles?

    <p><strong>Liver</strong> cells</p> Signup and view all the answers

    What substances are actively transported into the liver, kidney, and central nervous system?

    <p><strong>Xenobiotics</strong></p> Signup and view all the answers

    What is an essential function of active transport within the body?

    <p>Maintenance of electrolyte and nutrient balance</p> Signup and view all the answers

    Which factor determines the rate of passive transfer of xenobiotics across cell membranes?

    <p>The difference in concentrations of the substance on opposite sides of the membrane</p> Signup and view all the answers

    What is the main characteristic of the phosphate head of a phospholipid molecule in cell membranes?

    <p>Hydrophilic</p> Signup and view all the answers

    What is the term used to describe the movement of toxicants across a membrane barrier without requiring cellular energy?

    <p>Passive transfer</p> Signup and view all the answers

    What type of molecules can readily diffuse through the phospholipid membrane due to their properties?

    <p>Substances with high lipid solubility</p> Signup and view all the answers

    Which specialized transport mechanism requires the substance to be engulfed by the cell?

    <p>Endocytosis</p> Signup and view all the answers

    What property of chemical substances affects their ability for passive transfer across cell membranes?

    <p>Degree of ionization</p> Signup and view all the answers

    Which type of molecules can pass across a membrane through aqueous pores?

    <p>$H_2O$ molecules</p> Signup and view all the answers

    What is the primary way that xenobiotics cross cell membranes?

    <p>$O_2$ passive transfer</p> Signup and view all the answers

    Which type of molecules usually cannot make it through small pores in cell membranes?

    <p>$C_{1000}$ molecules</p> Signup and view all the answers

    What determines a toxicant's initial absorptive behavior and likelihood of distribution to tissues?

    <p>The affinity of a xenobiotic to various tissues</p> Signup and view all the answers

    Why is the disposition of a toxicant dependent on its volume of distribution (Vd)?

    <p>Because Vd is the volume in which the toxicant needs to be uniformly dissolved to produce observed blood concentration</p> Signup and view all the answers

    What can cause a chemical to have a high plasma concentration and low Vd?

    <p>Restricted distribution due to inability to cross cell membranes</p> Signup and view all the answers

    Why is binding of a toxicant to plasma proteins important in toxicology?

    <p>It influences toxicity by affecting the amount of unbound toxicant</p> Signup and view all the answers

    Which factor does NOT influence the distribution of a toxicant to tissues?

    <p>The speed of diffusion from tissues into the capillary bed</p> Signup and view all the answers

    Why may a compound with high plasma protein binding show less toxicity?

    <p>Because toxicity is typically related to the unbound fraction of the compound</p> Signup and view all the answers

    Which body compartment has a low plasma concentration if a chemical distributes throughout both compartments?

    <p>Extracellular water (interstitial water)</p> Signup and view all the answers

    What primarily determines the rate of distribution of a toxicant to organs or tissues?

    <p>Blood flow and diffusion from capillary beds into cells</p> Signup and view all the answers

    Why do some toxicants selectively accumulate in certain body parts?

    <p>As a result of binding to plasma proteins</p> Signup and view all the answers

    Why might accumulation at a site other than the target organ be viewed as protective?

    <p>As it decreases plasma levels and reduces concentration at the target site</p> Signup and view all the answers

    What determines if a chemical readily crosses cell membranes for distribution?

    <p>Physical and chemical characteristics</p> Signup and view all the answers

    What is the main reason why some toxicants do not readily enter the central nervous system?

    <p>Tightly joined capillary endothelial cells</p> Signup and view all the answers

    Which organ is mentioned to have a high capacity for binding a multitude of chemicals?

    <p>Liver</p> Signup and view all the answers

    What is a characteristic of the skeletal uptake of xenobiotics?

    <p>Deposition of toxicants in bone is dynamic</p> Signup and view all the answers

    How does storage in fat impact the toxicity of highly lipophilic toxicants?

    <p>Lowers toxicity in lean individuals</p> Signup and view all the answers

    Which barrier protects the developing fetus from toxicants absorbed in maternal circulation?

    <p>Placental barrier</p> Signup and view all the answers

    Which organs are likely to concentrate more toxicants than all other organs combined?

    <p>Liver and Kidney</p> Signup and view all the answers

    What physiological feature limits the movement of water-insoluble compounds through paracellular transport in the central nervous system?

    <p>High protein concentration in interstitial fluid</p> Signup and view all the answers

    Why is bone noted as a storage depot for xenobiotics?

    <p>Exchange occurs between bone surface and extracellular fluid</p> Signup and view all the answers

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