Cardiovascular System,
Blood, and Bone
Marrow
Answers
151.The answer is c.(Junqueira, pp 206–207, 211. Kumar, p 512.)Vasa
vasorum (VV) are vessels within a vessel and are found primarily in the
adventitia of large arteries and veins. They provide nutrition and oxy-
genated blood to the thick media and adventitia of these vessels, which are
unable to obtain nutrition by diffusion from the lumen. Coronary arteries
fulfill a similar function for the myocardium.
152.The answer is a.(Junqueira, pp 245–247. Ross, pp 268, 270–271.)The
first stage in granulopoiesis is the myeloblast (A), a large cell with prominent
light-staining nucleoli with only a little cytoplasm, generally without granules.
The lineage shown in the figure illustrates eosinophilic development in the
bone marrow. Basophils may be bilobed or segmented, but with larger and
more irregular granules that obscure the nucleus in Wright-stained blood
smears. The promyelocyte (B)is the next cell in the lineage. It is larger than
the myeloblast, nucleoli are less visible, and primary granules are present in
the cytoplasm. Granule specificity is attained in the myelocyte with flattening
of the nucleus. The eosinophilic myelocyte (C) differentiates into the
eosinophilic metamyelocyte (D)when invagination of the nucleus begins.
Further invagination leads to the formation of an eosinophilic band (E)and
ultimately a mature eosinophil (F).An eosinophil has a bilobed nucleus and
plays an important role in allergic and parasitic infections. The granules stain
with eosinophilic dyes and contain major basic protein, histaminase, peroxi-
dase, and some hydrolytic enzymes. Eosinophils have an affinity for antigen-
antibody complexes and, although phagocytic, are not as active against
bacteria as neutrophils. The histaminase secreted by eosinophils counteracts
the release of histamine from basophils and mast cells, essential in hypersen-
sitivity reactions. B lymphocytes differentiate into antibody-producing plasma
cells; T lymphocytes are responsible for cell-mediated responses including
graft rejection; and neutrophils are responsible for phagocytosis of bacteria.
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