Cardiovascular System: Lymphatic and Immune System
Explain why lymph from the right upper limb is drained into vessels
on the right side of the
neck, whereas lymph from the right lower limb is drained into vessels on the left side of the
Lymph from the right upper limb drains into the right subclavian
trunk, which may
then empty into the right lymphatic duct. These lymphatic vessels often return lymph fluid to the
venous blood proximal to the union of the right internal jugular vein and right subclavian vein. In
contrast, lymph from both lower limbs drains into the lumbar trunks, which empty into the
thoracic duct at the cisterna chyli. In this manner, lymph from the right lower limb will drain,
along with three-quarters of the body, into the vessels of the left side of the neck.
Identify and describe the functions of the lymphatic system.
The lymphatic system recovers tissue fluid and leaked plasma proteins
them to the bloodstream. By doing so, the system eliminates local variations in the chemical
composition and volume of tissue fluid. The lymphatic system also distributes hormones,
antibodies and cells of the immune system. Lastly, it picks up dietary fats from the intestines and
transports them into the bloodstream.
How does the structure and the function of lymph-collecting vessels
compare to those of
veins? What tunics do they have in common?
Lymph-collecting vessels transport fluids toward the heart in the
same manner as veins.
Both structures have three tunics, but the walls of the lymphatic vessels are thinner. Both
structures transport low-pressure fluids and consequently have one-way pocket valves to prevent
retrograde flow, although valves are more numerous in lymphatic vessels.
Patients often complain to their physician of "swollen
glands" in their neck. What is the
proper name of these "glands," and what is the significance of their swelling?
These structures are properly known as lymph nodes, specifically
cervical lymph nodes
if they are located in the neck. The nodes contain large numbers of macrophages and
lymphocytes. Large numbers of pathogens trapped in the lymph nodes can cause the node to
enlarge and become tender.
Describe the process of T cell activation and the significance of the blood-thymus barrier.
Immature lymphocytes that originate in the bone marrow, travel to the
they mature into T lymphocytes. In the thymus they develop immunocompetence, the ability to
recognize a specific antigen. These naive cells however, only become fully activated when they
experience an antigen challenge. In this process the T cell is presented with its specific antigen
by a macrophage or dendritic cell.