Video Transcript
Several types of blood cells are
present in the blood and in the lymphatic system. Which cell is a lymphocyte? (A) Cell (E), (B) cell (C), (C)
cell (D), (D) cell (A), (E) cell (B).
There are many types of white blood
cells in the immune system as we can see here. Let’s go over how these cells
develop from their precursor cells and describe what they look like to determine our
correct answer.
All of our blood cells come from a
common blood stem cell called a hematopoietic stem cell. This cell can differentiate into
two major cells: a myeloid progenitor and a lymphoid progenitor. Let’s look at the cells produced
from the myeloid progenitor first. The myeloid progenitor can
differentiate into multiple cells, including red blood cells or erythrocytes as
shown here. So we can eliminate cell (B), since
this is a red blood cell.
The myeloid progenitor can also
differentiate into a myeloblast, which can give rise to the basophil, neutrophil,
eosinophil, and monocyte. These cells are collectively known
as granulocytes. Granulocytes contain a multilobed
nucleus and granules to help destroy pathogens. So we can eliminate cells (C) and
(E) because these are granulocytes.
Monocytes can differentiate into
macrophages as shown here. Macrophages have ruffles in their
membrane, or protrusions, that can act as a type of tentacle to pull in pathogens
for phagocytosis. So cell (A) is a macrophage and not
a lymphocyte.
Now let’s look at cells produced by
the lymphoid progenitor. The lymphoid progenitor can give
rise to lymphocytes, such as natural killer cells and T or B lymphocytes. T and B lymphocytes have a large
nucleus and a small amount of cytoplasm. Therefore, cell (D) is a
lymphocyte, and the correct answer choice is (C), cell (D).
