The stru c tu re and function o f th e sp leen • Figure 12.5
The spleen filters blood and
stores blood cells.
White pulp is lymphatic
tissue consisting mainly
of lymphocytes and
macrophages, which filter
blood to remove debris
Red pulp consists of blood-filled
sinuses with red blood cells,
plasma cells, and granular
leukocytes. Here, worn-out blood
cells are destroyed and RBCs
and platelets are stored.
If a mosquito bit you and injected a microorganism into
your bloodstream, where would your lymphatic system
remove this organism to help reduce the incidence of
a. in the lymph nodes
b. in the white pulp of the spleen
c. in the thymus
d. in the red pulp of the spleen
e. in the tonsils
The spleen is the largest single mass of lymphatic tis-
sue in the body (Figure 12.5). It lies between the stomach
and the diaphragm and is covered by a capsule of dense
connective tissue. The spleen contains two types of tissue.
The red pulp stores platelets, perhaps up to one-third
of the body’s supply.
The red pulp produces blood cells during the growth of
White pulp is lymphatic tissue, consisting mostly of
lymphocytes and macrophages.
Red pulp consists of blood-filled venous sinuses and
cords of splenic tissue consisting of red blood cells,
macrophages, lymphocytes, plasma cells, and granular
Blood enters the spleen through the splenic artery and
then enters the white pulp. B cells and T cells within the
white pulp carry out immune responses, while macro-
phages destroy pathogens by phagocytosis. The red pulp
then performs three functions related to blood cells:
The macrophages remove worn out or defective blood
cells and platelets.
Finally, lymphatic nodules are egg-shaped masses of
lymphatic tissue that are not surrounded by a capsule.
Many are small and solitary, but some are grouped togeth-
er. For example, the tonsils in your throat are a group of
lymphatic nodules, strategically positioned to fight against
inhaled or ingested foreign substances.
processes drive the flow of lymph
through the lymphatic system?
glands are involved in the immune re-
sponses of the lymphatic system?
is the major difference between primary
and secondary lymphatic tissues?
Components of the Lymphatic System Are Found Throughout the Body