Video Transcript
The figure shows three different
types of glands. Which image (A), (B), or (C) is an
endocrine gland? What feature shown in the image is
common to all endocrine glands? (A) They do not have ducts. (B) They have cells of different
sizes. (C) They have a long, tube-like
structure. Or (D) They have a space where the
hormone is secreted.
An endocrine gland is a group of
specialized cells that secrete hormones directly into the bloodstream. These hormones can then control and
regulate different processes in the human body. In order to identify which image is
showing an endocrine gland, let’s look at the key features in each of the
images.
In image (A), we can see some blood
vessels. In both Image (B) and image (C), we
can see a long, tube-like structure called a duct. We can also see in both of these
images that some kind of secretion is being made onto a body surface. However, in images (B) and (C), we
cannot see any blood vessels. As we know that endocrine glands
secrete hormones directly into the bloodstream, we can work out that the image
showing an endocrine gland, which is closely associated with blood vessels, is Image
(A).
Let’s try the second part of the
question. We’ve already identified that image
(A) is showing us an endocrine gland. But what about images (B) and
(C)? These are both showing examples of
exocrine glands, which are groups of specialized cells that secrete substances via
ducts onto body surfaces. For example, image (B) is a
salivary gland secreting saliva via the salivary duct into the mouth, which is an
internal body surface. Image (C) displays a sweat gland
secreting sweat via sweat ducts onto the external body surface that is the skin.
A common feature of all endocrine
glands is that, unlike exocrine glands, they do not possess ducts. So they’re sometimes called
ductless glands. They don’t necessarily have cells
of different sizes, and they do not have long, tube-like structures, as this is
describing a duct. As you can also see in image (A),
they do not have a space into which the hormone is secreted. Instead, they secrete the hormones
directly into the blood. So we’ve worked out that the common
feature to all endocrine glands that’s shown in this image is that they do not have
ducts.
