CHAPTER 21
Answers to “What Did You Learn?”
1.
Erythrocytes make up about 44% of whole blood.
2.
The blood provides defense against pathogens and antigens that could harm us. In
addition, blood can form clots on damaged blood vessels to prevent excessive
fluid loss.
3.
Plasma is composed of water, proteins, and other solutes (electrolytes, nutrients,
respiratory gases, and waste products).
4.
The four classes of plasma proteins are albumins, globulins, fibrinogen, and
regulatory proteins.
5.
Erythrocytes lack organelles to allow more room for hemoglobin, which increases
their efficiency in transporting oxygen and carbon dioxide. However, the absence
of both a nucleus and cellular organelles means that the erythrocyte cannot
synthesize proteins for repair or replacement. Thus, the erythrocyte has a finite
life span of about 120 days.
6.
Transferrin and ferritin participate in recycling the iron ion of hemoglobin.
Transferrin removes and transports the ion to the liver, where it is passed to
ferritin, which stores it until it is needed and transported to the red bone marrow.
7.
The transfusion of blood from a person with blood type AB to a person with a
blood type A would not be successful. The person with blood type A has anti-B
antibodies and would react to the B surface antigens in the donor’s blood, causing
the blood to agglutinate.
21-1
8.
Leukopenia refers to a condition in which the number of leukocytes is below the
normal range of between 4500 – 11,000 per microliter of blood.
9.
Basophils are involved in inflammation. Basophil granules release histamine
causing vasodilation that leads to decreased blood pressure. Fluid leaking from
dilated blood vessels causes swelling in a local area. Histamine release also
occurs during allergy attacks, causing swelling around the nose and eyes. In
addition, basophils release heparin, which inhibits blood clotting.
10.
Megakaryocytes are large cells that form platelets. The megakaryocytes have
long cytoplamsic extensions through blood vessel walls and small particles of
these extentions are spliced off by the force of the blood flow. 11.
Hemocytoblasts are hemopoietic stem cells. They are pluripotent,
meaning that they can develop into many different kinds of blood cells. They
divide continuously to produce committed progenitor cells.
Answers to “Content Review”
1.
Blood plasma absorbs and distributes heat throughout the body. Blood vessels in
the dermis can dilate and dissipate additional heat. Likewise, these same blood
vessels will constrict (and blood is shunted to deeper blood vessels) if heat needs
to be conserved.
2.
Globulins are the second largest group of plasma proteins [forming about 37% of
all plasma proteins] and include alpha-, beta-, and gamma-globulins. The smaller
alpha-globulins and larger beta-globulins primarily bind, support, and protect
certain water-insoluble or hydrophobic molecules, hormones, and ions. Gamma-
21-2
globulins, also called immunoglobulins, are the molecules called antibodies.
Antibodies are soluble proteins produced by some of our defense cells to help
protect the body against pathogens that may cause disease.
3.
The buffy coat contains leukocytes and platelets.
4.
Erythrocytes have a unique biconcave disk structure that allows respiratory gases
to be loaded and unloaded rapidly and efficiently. Additionally, their structure
facilitates both a single-line stacking of these cells, termed a rouleau, as they pass
through small blood vessels, and some flexibility of the cells to permit their
passage through the smallest vessels.
5.
Each hemoglobin molecule consists of four protein building blocks, called globin.
Each globin contains a nonprotein (or heme) group that is in the shape of a ring
with an (Fe2+) ion (called a ferrous ion) in the center of the ring. Oxygen binds to
these iron ions for transport in the blood. The oxygen binding is fairly weak to
assure that there is a rapid attachment and detachment of oxygen with
hemoglobin.
6.
Neutrophils have a multilobed nucleus (as many as 5 lobes) and cytoplasm with
pale-colored granules. Eosinophils have a bilobed nucleus and cytoplasm with
pink-orange to reddish granules. Basophils have a bilobed or S-shaped nucleus
and cytoplasm with deep-purple granules. Lymphocytes have a round or slightly
indented nucleus that fills the cell. The nucleus is darkly stained and surrounded
by a thin rim of cytoplasm. These 4 leukocytes are about 1.5 times the diameter
of an erythrocyte. Monocytes have a kidney or U-shaped pale-staining nucleus
with abundant cytoplasm. They are almost 3 times the diameter of an erythrocyte.
21-3
7.
Basophils are involved in the release of histamine and heparin during antiinflammatory or allergic reactions. Lymphocytes attack pathogens, destroy
cancer cells, coordinate immune cell activity, and produce antibodies.
8.
Platelets are continually produced in the red bone marrow by cells called
megakaryocytes. Megakaryocytes extend long processes (called proplatelets)
through the blood vessel wall. These proplatelets are spliced by the force of the
blood flow into platelets. They help produce a clot to prevent blood loss.
9.
Hemopoiesis is the process to produce newly formed elements in the blood.
Hemocytoblasts are the hemopoietic stem cells from which formed elements are
derived. The two lines of blood cell development are: the myeloid line that gives
rise to erythrocytes, megakaryocytes, and all leukocytes except lymphocytes, and
the lymphoid line that forms the lymphocytes.
10.
A number of hormones and growth factors found in the bone marrow are
called colony-stimulating factors (CSFs). These stimulating molecules clearly
influence the maturation and division of the blood stem cells.
21-4