All of the following are main
organs of the endocrine system except the blank. (A) Thyroid gland, (B) liver, (C)
pancreas, or (D) adrenal gland.
To answer this question correctly,
we need to learn some more information about the human endocrine system.
The endocrine system is made up of
many different glands that consist of cells that function to release hormones
directly into the bloodstream. The blood transports hormones
throughout the entire body, and these hormones eventually reach their specific
target cells upon which they can trigger a specific effect to maintain normal
functioning of the body. Let’s take a look at some of the
glands in the human endocrine system, which have been shown in pink in this diagram
on the right.
The thyroid gland is a
butterfly-shaped endocrine gland located at the base of the neck that releases a
hormone called thyroxine among others. Thyroxine has various target
tissues and various effects, such as modulating our energy level, metabolism, and
even our growth. As the question is asking for
organs that are not part of the human endocrine system, we can eliminate option (A),
as we know the thyroid gland is an endocrine gland.
The pancreas contains endocrine
cells that release hormones, so we can eliminate option (C), as the pancreas does
function as an endocrine gland. For example, when blood glucose
levels are low, glucagon is released from the pancreas and instructs liver cells to
break down their stores of glycogen into glucose, which is then released into the
blood to increase the levels of blood glucose back to a healthy range.
While the liver is useful in this
hormonal response in addition to its many other functions, it is not a gland within
the endocrine system as it does not release any hormones, which suggests that the
organ listed that is not a main organ of the endocrine system is the liver.
Let’s double check that this is the
correct answer by taking a look at the final option, the adrenal gland. Humans typically have two adrenal
glands, one of which sits above each of our kidneys. The adrenal glands release many
different hormones, so we can confirm that they are organs belonging to the
endocrine system. For example, they release
adrenaline, which helps our body to respond effectively to stressful situations.
We’ve worked out that the thyroid
gland, pancreas, and adrenal glands are all main organs of the endocrine system so
cannot be our correct answer. The answer choice which is not a
main organ of the endocrine system is (B) the liver.