Lymphatic and Immune.

Lymph moves through the body in lymphatic vessels and empties into large veins. Blood travels through arteries, veins, and capillaries and returns to the heart. Lymph specifically drains into the venous system, not arteries or capillaries.

Formed elements in blood are the cellular components: erythrocytes (red blood cells), leucocytes (white blood cells), and thrombocytes (platelets). Plasma is the fluid portion of blood, not a formed element. Proteins and hormones are transported by blood but are not formed elements. Oxygen and carbon dioxide are respiratory gases carried by plasma and erythrocytes.

Antigens sit on the surface of red blood cells and determine blood group. A person with group A carries A antigens on the RBC surface and anti-B antibodies in plasma. You develop antibodies to the antigens you do not have. Antibodies are in plasma, not on red blood cells. Antigens are on the RBC surface, not in plasma. A person with blood group A would not have anti-A antibodies, as that would trigger an immune reaction against their own cells.

Successful blood transfusion requires both blood group and rhesus factor compatibility. Rhesus (Rh) factors are antigens on the surface of some individuals' red blood cells. Those with the factor are Rh-positive; those without are Rh-negative. Matching blood group alone is not sufficient. Rhesus factor alone is not sufficient. Incompatible transfusions cause clotting, hemolysis, and other transfusion reactions.

Primary lymphoid organs are bone marrow and thymus. Lymphoid organs are where lymphocytes mature. Lymph nodes, spleen, and tonsils are all secondary lymphoid organs. Secondary lymphoid organs also include lymphoid tissues in mucous membranes.

T lymphocytes are produced in the bone marrow but mature in the thymus. B lymphocytes are produced in the bone marrow and mature primarily in the bone marrow. The spleen and lymph nodes are secondary lymphoid organs where mature lymphocytes encounter antigens.

Barrier defenses are physical barriers that prevent pathogens from entering body tissues. They include skin and mucous membranes. Neutrophils, macrophages, and mast cells are part of the innate immune response, not barrier defenses. They act after pathogens have breached the physical barriers.

Phagocytes are part of the body's first line of immunological defense. They protect against pathogens by engulfing them. Phagocytes include dendritic cells, neutrophils, eosinophils, macrophages, and monocytes. Natural killer cells, T lymphocytes, and plasma cells are not phagocytes. They participate in immunity through other mechanisms.

Natural killer cells resemble lymphocytes. Their granules contain chemicals that can destroy virally infected cells. Neutrophils are phagocytes that engulf pathogens like bacteria. B lymphocytes and plasma cells do not directly destroy cells. Instead, they produce antibodies.

Plasma cells are formed from B lymphocytes and they secrete antibodies. T lymphocytes release chemical messengers called cytokines. Macrophages and dendritic cells are phagocytes and do not secrete antibodies.