Plasma—the liquid portion of blood
- 91% water.
- Plasma transports nutrients, wastes, hormones,
antibodies, and CO 2 as HCO 3 –. - Plasma proteins: clotting factors are synthesized by
the liver; albumin is synthesized by the liver and
provides colloid osmotic pressure that pulls tissue
fluid into capillaries to maintain normal blood vol-
ume and blood pressure; alpha and beta globulins
are synthesized by the liver and are carriers for fats
and other substances in the blood; gamma globu-
lins are antibodies produced by lymphocytes.
Blood Cells
- Formed elements are RBCs, WBCs, and platelets
(Figs. 11–2 and 11–3). - After birth the primary hemopoietic tissue is the
red bone marrow, which contains stem cells.
Lymphocytes mature and divide in the lymphatic
tissue of the spleen, lymph nodes, and thymus,
which also have stem cells for lymphocytes.
Red Blood Cells—erythrocytes (see Table
11–2 for normal values)
- Biconcave discs; no nuclei when mature.
- RBCs carry O 2 bonded to the iron in hemoglobin.
- RBCs are formed in the RBM from hemocytoblasts
(stem cells, the precursor cells). - Hypoxia stimulates the kidneys to produce the hor-
mone erythropoietin, which increases the rate of
RBC production in the RBM. - Immature RBCs: normoblasts (have nuclei) and
reticulocytes; large numbers in peripheral cir-
culation indicate a need for more RBCs to carry
oxygen. - Vitamin B 12 is the extrinsic factor, needed for DNA
synthesis (mitosis) in stem cells in the RBM.
Intrinsic factor is produced by the parietal cells of
the stomach lining; it combines with B 12 to prevent
its digestion and promote its absorption. - RBCs live for 120 days and are then phagocytized
by macrophages in the liver, spleen, and RBM. The
iron is returned to the RBM or stored in the liver.
The heme of the hemoglobin is converted to biliru-
bin, which the liver excretes into bile to be elimi-
nated in feces. Colon bacteria change bilirubin to
urobilinogen. Any urobilinogen absorbed is con-
verted to urobilin and excreted by the kidneys in
urine (Fig. 11–4). Jaundice is the accumulation of
bilirubin in the blood, perhaps due to liver disease.
8. ABO blood types are hereditary. The type indicates
the antigen(s) on the RBCs (see Table 11–1 and
Fig. 11–5); antibodies in plasma are for those anti-
gens not present on the RBCs and are important
for transfusions.
9. The Rh type is also hereditary. Rh positive means
that the D antigen is present on the RBCs; Rh neg-
ative means that the D antigen is not present on the
RBCs. Rh-negative people do not have natural
antibodies but will produce them if given Rh-
positive blood.
White Blood Cells—leukocytes (see Table
11–2 for normal values)- Larger than RBCs; have nuclei when mature; pro-
duced in the red bone marrow, except some lym-
phocytes produced in the thymus (Figs. 11–2 and
11–3). - Granular WBCs are the neutrophils, eosinophils,
and basophils. - Agranular WBCs are the lymphocytes and mono-
cytes. - Neutrophils and monocytes phagocytize patho-
gens; monocytes become macrophages, which also
phagocytize dead tissue. - Eosinophils detoxify foreign proteins during aller-
gic reactions and parasitic infections; they phago-
cytize anything labeled with antibodies. - Basophils contain the anticoagulant heparin and
histamine, which contributes to inflammation. - Lymphocytes: T cells, B cells, and natural killer
cells. T cells recognize foreign antigens and des-
troy them. B cells become plasma cells, which pro-
duce antibodies to foreign antigens. NK cells
destroy foreign cell membranes. - WBCs carry out their functions in tissue fluid and
lymphatic tissue, as well as in the blood.
Platelets—thrombocytes (see Table 11–2 for
normal values)- Platelets are formed in the RBM and are fragments
of megakaryocytes; the hormone thrombopoietin
from the liver increases platelet production. - Platelets are involved in all mechanisms of hemo-
stasis (prevention of blood loss) (Fig. 11–6). - Vascular spasm—large vessels constrict when
damaged, the myogenic response. Platelets release
serotonin, which also causes vasoconstriction. The
break in the vessel is made smaller and may be
closed with a blood clot.
Blood 269