Video Transcript
The figure shows a drawing of a
cross section of the seminiferous tubules in the testes. Identify the cell that secretes
testosterone.
The seminiferous tubules, one of
which is represented as the large circular structure in the center of this diagram,
make up the bulk of the testes in human biological males and are the location of
sperm production. 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 diploid primary germ cells into haploid mature sperm cells. It 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 and is often represented as
2n. Haploid cells that are produced
through meiosis, on the other hand, have half this number of chromosomes, only a
single set, often represented as n.
The mature sperm cells that are the
final product of spermatogenesis are haploid gametes. If they fuse together with another
haploid gamete, the egg cell in fertilization, this will form a diploid zygote with
a full set of chromosomes ready to develop into a fully formed human.
Let’s have a go at labelling some
of the cells that we can see within and surrounding 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, as we can
see sperm cells at most different stages of development that follow the initial
primary germ cell stage.
The cells that are eventually
produced from these primary germ cells in the first stage of spermatogenesis just
after the birth of the biological male are found furthest from the lumen and are
called spermatogonia, or a singular spermatogonium. These cells are still diploid, as
they are produced through mitosis and have not yet entered meiosis. The spermatogonia do eventually go
through meiosis, the final product of which are haploid spermatids, located closer
to the lumen of the seminiferous tubule. The spermatids then differentiate
into haploid mature sperm cells that can be released into the lumen. This completes the process of
spermatogenesis.
The seminiferous tubules also
contain 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. For example, some interstitial
cells are interspersed between the seminiferous tubules and the testes. A specific example of interstitial
cells that are found in the testes are called Leydig cells. Leydig cells are responsible for
producing and secreting the hormone testosterone. Testosterone plays an important
role in the completion of meiosis in spermatogenesis and various other processes
that aid it, such as the fluid secretion from the Sertoli cells.
Therefore, the cell that secretes
testosterone is an interstitial cell, which is labeled (E).
