Histology Testbank: Blood 2a

Instructions: For each histology question, pick the one best answer. This histology test bank is also useful for the histology questions on the USMLE (USMLE step 1).

1.
Approximately what percentage of the volume of blood do the formed elements comprise?
a. 5
b. 25
c. 45
d. 75
e. 90

Answer: c

Blood is composed of the formed elements and plasma. Plasma is the liquid portion of blood. The formed elements consist of the cells and cell fragments. The erythrocytes (red blood cells), platelets, and leukocytes (white blood cells) are all considered formed elements.

When a sample of blood is centrifuged, the percentage occupied by the formed elements is the hematocrit. An average hematocrit is about 45%.

2.
Which of the following is the most abundant in a peripheral smear of blood?
a. Neutrophils
b. Basophils
c. Erythrocytes
d. Leukocytes
e. Platelets

Answer: c

Erythrocytes (red blood cells) are the most abundant formed element in a peripheral smear of blood.

3.
Which leukocyte is the least abundant in a peripheral smear of blood?
a. Lymphocytes
b. Basophils
c. Neutrophil
d. Monocytes
e. Eosinophils

Answer: b Basophils are the least abundant leukocyte. Leukocytes are the white blood cells. The order of frequency of the leukocytes is: neutrophil, lymphocyte, monocyte, eosinophil, basophil. Histology hint from Sarah Bellham: The order of frequency of the leukocytes can be remembered by the mnemonic: "Never Let Monkeys Eat Bananas".

4.
Which of the following is not a granulocyte?
a. PMN
b. Basophils
c. Neutrophil
d. Monocytes
e. Eosinophils

Answer: d

The granulocytes are named because of the presence of visible cytoplasmic granules. The granulocytes consist of neutrophils, eosinophils, and basophils. "PMN" is an abbreviation for polymorphonuclear neutrophil. Thus, it is a neutrophil, which is a granulocyte. The non-granulocytes are lymphocytes and monocytes.

Histology hint from Sarah Bellham: Poly is from the Greek "polys", which means many. "Poly" is also sometimes used as a nickname for polymorphonuclear leukocyte.

5.
Which of the following is a granulocyte?
a. Thrombocyte
b. Monocyte
c. Lymphocyte
d. Basophil
e. Erythrocyte

Answer: d

The granulocytes are named because of the presence of visible cytoplasmic granules. The granulocytes consist of neutrophils, eosinophils, and basophils. The non-granulocytes are lymphocytes and monocytes. Erythrocytes are red blood cells. A thrombocyte is a platelet.

Histology hint from Sarah Bellham: The suffix (or prefix) "phil" comes from the Greek word meaning love. It is used to specify an attraction or affinity towards something. It is seen in such words as philosophy, philanthropy and bibliophile.

This suffix is used in naming the three granulocytes: eosinophils, basophils, and neutrophils. Eosinophils "love" or are attracted to the eosin dye; thus the granules in an eosinophil are orange/pink. Basophils "love" or are attracted to the basophilic dye; thus the granules in a basophil are blue. Neutrophils "love" or are attracted to the neutral dye; thus the granules in a neutrophil are neutral colored.

6.
Which of the following is described as having a "central pallor"?
a. Leukocytes
b. Monocytes
c. Eosinophils
d. Platelets
e. Erythrocytes

Answer: e

Erythrocytes (red blood cells) are described as biconcave discs. When stained, this phenomenon results in the central portion of the cell staining lighter, thus the "central pallor".

Histology hint from Sarah Bellham: A biconcave disc can be visualized by holding two Frisbees together so that the middle portion is thinner than the top or bottom.

7.
Which is the smallest leukocyte?
a. Neutrophil
b. Lymphocytes
c. Monocytes
d. Eosinophil
e. Basophils

Answer: b

The leukocytes consist of neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Neutrophils are granulocytes. Neutrophils have a multi-lobed nucleus. The lobes are separated by a thin strand. Because of the shape of the nucleus, neutrophils are also called "polymorphonuclear neutrophils", "poly's", "PMN", or "polymorph.

Lymphocytes are agranulocytes. Lymphocytes can be categorized by three sizes: small, medium, and large. The small lymphocytes are the smallest leukocyte, being only slightly larger than an erythrocyte.

Monocytes are agranulocytes. They are the largest leukocyte.

Eosinophils are granulocytes. Eosinophils have prominent orange pink granules. The nucleus of eosinophils is usually bi-lobed.

Basophils are granulocytes. Basophils have large blue granules, which often obscure the nucleus. The granules are basophilic, therefore they are blue.

8.
Which leukocyte usually has a bi-lobed nucleus?
a. Neutrophil
b. Lymphocytes
c. Monocytes
d. Eosinophil
e. Basophils

Answer: d

The leukocytes consist of neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Neutrophils are granulocytes. Neutrophils have a multi-lobed nucleus. The lobes are separated by a thin strand. Because of the shape of the nucleus, neutrophils are also called "polymorphonuclear neutrophils", "poly's", "PMN", or "polymorph".

Lymphocytes are agranulocytes. Lymphocytes can be categorized by three sizes: small, medium, and large. The small lymphocytes are the smallest leukocyte, being only slightly larger than an erythrocyte.

Monocytes are agranulocytes. They are the largest leukocyte.

Eosinophils are granulocytes. Eosinophils have prominent orange pink granules. The nucleus of eosinophils is usually bi-lobed.

Basophils are granulocytes. Basophils have large blue granules, which often obscure the nucleus. The granules are basophilic, therefore they are blue.

9.
What is the buffy coat?
a. Leukocytes
b. Platelets
c. Erythrocytes
d. Plasma
e. Both a and b

Answer e:

The buffy coat is seen in a sample of centrifuged blood. It is the thin layer above the red blood cells, but below the plasma. It consists of the leukocytes and platelets.

10.
What is another term for a platelet?
a. Thrombocyte
b. Monocyte
c. Lymphocyte
d. Basophil
e. Erythrocyte

Answer: a

A thrombocyte is another name for a platelet.