+ What is the name of the mechanism/structure that allows the hypothalamus to communicate with the anterior pituitary? With the posterior pituitary?
Within the stalk, a specialized capillary system, the hypophyseal portal sytem, allows the hypothalamus to communicate with the anterior pituitary. The posterior and hypothalamus communicate through a collection of neurons in the stalk called the hypothalamic-hypophyseal.
+ What causes a goiter resulting in hyperthyroidism? In hypothyroidism?
The most common type of goiter is caused by an iodine deficiency, this is hypothyroidism.
When the thyroid gland produces too much thyroid hormone, it leads to hyperthyroidism.
+ portal systems: where are they located in the body?
A portal system, or portal venous system (which is more accurate) is a system that connects two capillary beds to one another using "portal veins". This system allows blood flow between the two capillary beds without flowing through the heart. This is an advantage where certain organs/organ systems require highly localized concentrations of substances (e.g. hormones).
Two major portal systems are the hypophyseal portal system for the hypothalamic-pituitary axis, and the hepatic portal system for the liver and GI tract.
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