51) The ________ stores blood platelets.
A) lymph node
B) thymus
C) tonsil
D) spleen
52) The lymphatic capillaries are
A) more permeable than blood capillaries.
B) less permeable than blood capillaries.
C) as permeable as blood capillaries.
D) completely impermeable.
53) B lymphocytes are to ________ as T lymphocytes are to ________.
A) antibodies; antigens
B) antibodies; programmed cell death
C) antigens; antibodies
D) programmed cell death; antibodies
54) Which cell has the responsibility of presenting foreign antigens to lymphocytes?
A) cytotoxic CD8+ T lymphocyte
B) dendritic cell
C) helper CD4+ T lymphocyte
D) natural killer
55) Lymph capillaries differ from blood capillaries in all of the following ways
except
that
A) they are more permeable than most blood capillaries.
B) they carry lymph instead of blood.
C) they are blind-ended.
D) their walls consist of endothelial cells.
56) Which of the following might explain why most people are sick more often as children than as adults in their 20s through 50s?
A) The immune system does not appear until the preteen years.
B) The thymus is so active in children that it fights bacteria so hard that it produces strong symptoms of disease.
C) Because of their small size, children's bodies cannot contain as much lymphoid tissue as those of adults.
D) We build up many varieties of memory lymphocytes during childhood, providing immunity to more and more antigens during adulthood.
57) The bulges that give lymph vessels a string-of-beads appearance are really
A) lymph nodes.
B) pockets for valves.
C) weakenings in the wall of the vessels.
D) temporary constrictions caused by bulging skeletal muscles that squeeze the lymph vessel.
58) Lymphoid tissue contains all of the following elements
except
A) T cells.
B) B cells.
C) follicles.
D) thick collagen fibers.
59) Clusters of lymph nodes occur in all of the following sites
except
A) along the aorta.
B) in the mediastinum.
C) in bones and bone marrow.
D) in the inguinal region.
60) Because the appendix is a narrow tube, it traps microorganisms from the digestive tract, and these microorganisms enter its wall and activate memory lymphocytes for long-term immunity. Another immune organ that traps microorganisms is the
A) thymus.
B) bone marrow.
C) palatine tonsil.
D) the spleen.