QUESTIONS AND CORRECT ANSWERS GRADED A+/ NUR 100
LATEST EXAM
What is the first type of cell produced by the developing embryo?
A. Erythrocyte
B. Granulocyte
C. Lymphocyte
D. Thrombocyte
Ans: A. Erythrocyte
The need for oxygen delivery to developing tissues results in the production of erythrocytes
before other blood cells. Erythropoiesis commences in the yolk sac as early as the fourteenth
day of embryonic development. These primitive red cells produce embryonic hemoglobins that
temporarily serve oxygen needs of the fetus. Myelopoietic and lymphopoietic activities beginw
ehn the liver and spleen become sites of production at 6-9 weeks of gestation; however,
erythropoiesis still predominates. At this time, the red cells produce hemoglobin F, which is the
chief oxygen carrier during fetal life.
,Quiz What percentage of tissue located in the bone marrow cavities of adults is fat?
A. 10%
B. 25%
C. 50%
D. 75%
Ans: C. 50%
In the infant, there is an increased demand for blood formation because of the rate of growth.
At birth, all bone marrow cavities are filled with hematopoietic tissue (active red marrow). As
the growth rate slows, there is less need for active marrow. Fatty infiltration of the marrow
becomes noticeable at about 4 years of age as cell production diminishes within the shafts of
the long bones and is filled with yellow inactive tissue. Fat comprises 50% of the total marrow
space in the adult. Except for lymphopoiesis, hematopoiesis is confined to the flat bones and
pelvic area by the age of 25 years.
Quiz Which of the following is not characteristic of pluripotent hematopoietic stem cells?
A. Possess self-renewal ability
B. Produce progenitor cells committed to a single cell lineage
C. Express the stem cell marker CD13
D. Are morphologically unrecognizable
,Ans: C. Express the stem cell marker CD13
Hematopoietic stem cells can make copies of themselves to maintain the stem cell pool and
possess the ability to generate cells of all lineages (pluripotential). These stem cells give rise to
multipotential myeloid and lymphoid progenitor cells, which ultimately produce progenitor
cells that are restricted to a specific cell lineage. With appropriate cytokine stimulus, the
committed progenitor cells undergo proliferation to recognizable precursors that produce an
amplified number of mature end-stage cells. Stem cells and progenitor cells cannot be
morphologically distinguished (look similar to small lymphocytes) but can be identified
phenotypically by markers such as the stem cell marker CD34. CD34 expression is lost as
antigens for a specific cell lineage are expressed. CD13 is a marker expressed by myeloid
precursors.
Quiz As an adult, what are the two best areas for obtaining active bone marrow by aspiration?
A. Vertebra, tibia
B. Sternum, vertebra
C. Anteroir iliac crest, tibia
D. Posterior iliac crest, sternum
Ans: D. Posterior iliac crest, sternum
Unlike the infant, in which all BM is capable of forming blood cells, the active marrow in an
adult is confined to the flat bones of the skeleton such as the sternum and posterior iliac crest.
Although the spinous processes of the vertebrae contain active marrow, these sites are rarely
, used for aspiration in adults because of the danger of damage to the spinal cord. Sternal
puncture also presents a possibility of serious damage to underlying structures but may be used
because of easy accessibility or if the aspirate is a dry tap in the iliac crest. To obtain both a BM
aspirate and core biopsy, most marrow specimens are taken from the posterior iliac crest. The
anterior iliac crest may occasionally be used in adults and sometimes the tibia in children less
than 2 years of age.
Quiz What is the normal ratio of myeloid to erythroid precursors in bone marrow (M:E ratio)?
A. 1:1
B. 1:3
C. 4:1
D. 8:1
Ans: C. 4:1
The ratio between all granulocytes and their precursors and all nucleated red cell precursors
represent the myeloid-to-erythroid ratio. Myeloid precursors outnumber erythroid precursors
by about 3 or 4 to 1 in the normal BM. Although there are many more RBCs in the peripheral
blood than granulocytes, RBCs have a much longer life span in circulation (120 days) as
compared to granulocytes (about 8 hours). Granulocytes, therefore, require a more continual
production than erythrocytes and are the most numerous marrow precursors. Alteration in the
M:E ratio such as 1:1 or 8:1 may indicate erythroid hyperplasia or granulocytic hyperplasia,
respectively.
Quiz Which of the following does not accurately describe hematopoietic growth factors?