Question

1) Toxicants

a) Which of the following is NOT a major storage site for toxicants?

Kidney

Blood brain barrier

Bone

Fat

Liver

b) Which of the following are true regarding toxicant excretion by the lungs? (check all that apply)

  Because the alveolar epithelium is so thin, toxicant transfer from blood into alveoli requires active transport

   Extensive capillary networks surrounding alveoli aids in rapid toxicant and gas exchange between blood and alveoli

   The structure of the capillary network and alveolar sacs creates an efficient route of elimination for volatile lipophilic toxicants

   The higher the solubility in blood, the more likely a toxicant is to be excreted by the lungs

Answer 1

1. Answer:- Blood brain barrier

The prime goal of the blood–brain barrier is to protect the brain against circulating toxins or pathogens that could cause brain infection.

Due to this reason, Blood brain barrier is not the major storage site for toxicants.

Fats

The fats are in a continual exchange with blood and thus the toxic particles may be mobilized into the blood for further distribution and elimination or maybe get redeposited in other adipose tissue cells. Due to this reason, fats are the major toxicant storage site.

Bone

Bone is another major site for storage. Bone is made up of proteins and the mineral salt hydroxyapatite. Bone contains very short blood supply. During the normal processes that form bone, calcium and hydroxyl ions are incorporated into the hydroxyapatite-calcium matrix. Several chemicals, primarily elements, follow the same kinetics as calcium and hydroxyl ions and therefore that element can be substituted for them in the bone matrix.

For example, elements like strontium or lead may be substituted for calcium (Ca), and fluoride (F-) may be substituted for hydroxyl (OH-) ions. As the bones are continually being remodeled under normal conditions. Calcium and other minerals are continually being resorbed and replaced. Thus, any toxicants stored in the matrix, has a chance to get into the circulatory system.

Liver

The liver is a storage site for some toxic substances. Having large blood flow and its hepatocytes (so called liver cells) contain proteins that bind to some chemicals, including toxicants.

Kidney

Just like liver, the kidneys have a high blood flow, which preferentially exposes these organs to toxicants in high concentrations. Storage of toxic in the kidneys is associated primarily with the cells of the nephron. (the structural and functional unit of kidney).

2. true regarding toxicant excretion by the lungs:-

Answer:-

1. Because the alveolar epithelium is so thin, toxicant transfer from blood into alveoli requires active transport.

2. Extensive capillary networks surrounding alveoli aids in rapid toxicant and gas exchange between blood and alveoli.

3. The structure of the capillary network and alveolar sacs creates an efficient route of elimination for volatile lipophilic toxicants.