Video Transcript
The figure shows a drawing of a
cross section of the seminiferous tubules in the testes. Identify the cells that are
haploid. (A) A and C. (B) B and C. (C) B, C, and D. (D) C only. Or (E) C and E.
One seminiferous tubule has been
represented here as the large, circular structure in the center of this diagram. The seminiferous tubules make up
the bulk of the testes in human biological males and are the location of sperm
production. And we can also see the edges of
two other seminiferous tubules on the left of the diagram here.
Sperm production is often called
spermatogenesis. Spermatogenesis functions to
convert primary germ cells into mature sperm cells. Primary germ cells are diploid
cells. The mature sperm cells they are
converted into are haploid. This conversion involves a special
type of cell division called meiosis that halves the number of chromosomes in a
cell.
You may recall that a diploid cell
has two sets of chromosomes like most other body cells. This is often represented as two
n. The haploid cells that are produced
through meiosis, on the other hand, have half this number of chromosomes. Haploid cells are often represented
as n. The mature sperm cells that are the
final product of spermatogenesis are haploid gametes. The main function of a sperm cell
is to fuse with another haploid gamete, the egg cell, in fertilization. Fertilization produces a diploid
zygote with two sets of chromosomes, ready to develop into a fully formed human.
Let’s have a go at labeling some of
the cells that we can see in the seminiferous tubule in the center of the
diagram. In the middle of each seminiferous
tubule is a space called the lumen. The seminiferous tubules of a
biological male who has begun puberty tell us a story of sperm production. We can see sperm cells at most of
the different stages of development that follow the initial primary germ cell
stage.
The cells that are eventually
produced from these primary germ cells following the birth of the male are found
furthest from the lumen and are called spermatogonia, or a singular
spermatogonium. These cells are diploid as they
were produced through mitosis and have not yet begun meiosis. These spermatogonia enter meiosis
to eventually produce haploid spermatids. The spermatids are located closer
to the lumen of the seminiferous tubule than the spermatogonia. The spermatids then differentiate
into haploid mature sperm cells. The mature sperm cells can be
released into the lumen.
We can be fairly confident that the
correct answer is therefore (B), as the two cells labeled B and C are both
haploid. To make sure, let’s check that the
other cells that have been labeled on this diagram are not haploid too. The seminiferous tubules also
contain diploid cells called Sertoli cells. One of the functions of Sertoli
cells is to secrete fluids to nourish and support the developing sperm cells.
Interstitial cells can be located
in various regions of the body between the functional cells of any particular
tissue. A specific example of interstitial
cells in the testes is Leydig cells, which are also diploid cells. Leydig cells are responsible for
producing and secreting the hormone testosterone. This confirms that the haploid
cells in the testes are spermatids and mature sperm cells. So, the correct answer to this
question is (B), B and C.
