HS 370
ABSORPTION OF TOXICANTS
Lecture Outline
Cellular Interaction Occurs:
1. On cell surface
2. Within the cell
3. In underlying tissue
Cellular Membrane Structure:
Phospholipid Molecules- Two Components
A. Phosphates:
Hydrophilic region-
B. Lipids:
Hydrophobic region-
Appearance: Phospholipid Bilayer-
Characteristics: Semipermeable Membrane
Process of Cellular Absorption:
Three main types of transport mechanisms to gain entrance into the cell: (Passive or Active)
1.Simple Diffusion:
Passive
Most Common
Concentration Gradient
2.Faciliated Diffusion:
Passive
Minor Role in Transportation
Major Role for Elimination
3.Active Transport:
Use of ATP (Active)
Minor Role in Transportation
Major Role in Elimination
4. Macromolecules:
Phagocytosis
a. Exocytosis
b. Endocytosis
Three Routes of Absorption of Toxicants Within the body:
1. Percutaneous (skin)
2. Inhalation
3. Ingestion
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I. Percutaneous Route
Includes:
1.
2.
3.
4.
5.
Skin Plays An Important Role:
1. Barrier against entry of toxicants and microorganisms
2. Protects against harmful effects of UV radiation
3. Assists in biotransformation of toxicants
4. Eliminates toxicants via sweat or cellular secretion
5. Regulates body temperature
6. Houses sensory receptors for temperature, pain and pressure
Skin composed of:
1. Epidermis-
2. Dermis-
3. Hypodermis-
Most common route of toxicant absorption through the skin:
Absorption by skin outler layer followed by passive diffusion through the epidermis and into the
dermis.
How quickly a toxicant diffuses through the epidermis is affected by a number of factors,
including:
1.
2.
3.
4.
*Toxicants that are small, nonpolar, and lipid-soluble will diffuse most rapidly.
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II. Respiratory System Route:
Respiratory System: 3 anatomical regions
1. Nasopharyngeal
2. Tracheobronchial
3. Alveolar
1. Nasopharyngeal region:
This region is composed of:
1. nares (nostrils)
2. nasopharynx
3. oropharynx
4. laryngopharynx
5. larynx
Toxicant Infiltration:
2. Tracheobronchial region:
a. trachea (windpipe)
b. bronchi (singular bronchus), and
c. bronchioles
Mucociliary Escalator:
Importance of cilia:
3. Alveolar region:
1. respiratory bronchioles
2. singular alveolus
Factors that affect respiratory absorption of inhaled substances:
1. Gases and vapors
Solubility
2. Particles
Solubility
Size
Toxicant Infiltration:
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III. Digestive System Route
1. mouth
2. oral cavity
3. esophagus
4. stomach
5. small intestine
6. large intestine
7. rectum
8. anus
9. accessory organs, such as pancreas & liver
Four distinct zones of the digestive system:
Mucosa-
Submucosa-
Muscularis-
Serosa-
Toxicant Infiltration
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