D–G
disseminated intravascular coagulation (DIC) A
secondaryCOAGULATION disorder arising from an
imbalance among the CLOTTING FACTORS in the
BLOOD. DIC occurs as a result of a significant
underlying health condition such as HIV/AIDS,
overwhelming infections, or CANCER, and as a seri-
ous complication in PREGNANCY. DIC is a symptom
rather than a condition. Indications of its presence
include
- PETECHIAE(pinpoint hemorrhages), especially on
the roof of the MOUTH (soft palate) and the
lower legs - ECCHYMOSIS(easy bruising)
- hemorrhage (easy bleeding)
- thrombosis (clot formations in the blood ves-
sels, typically the veins)
The diagnostic path includes blood tests, espe-
cially fibrinogen and fibrin split products. Treat-
ment for DIC targets the underlying cause, though
may include measures such as BLOOD TRANSFUSION
to arrest hemorrhaging or ANTICOAGULATION THERAPY
when the condition manifests as thrombosis. The
outlook, like the treatment, depends on the
underlying cause.
See also PLATELET.
eosinophil See GRANULOCYTE.
erythrocyte A red BLOODcell (RBC). The primary
function of erythrocytes is to carry oxygen from
the LUNGSto the cells of tissues throughout the
body and return carbon dioxide, a metabolic
waste, to the lungs for removal from the body.
Erythrocytes contain iron and HEMOGLOBIN, a pig-
mented protein that gives them their red color.
Hemoglobin is the substance to which oxygen and
carbon dioxide molecules bind for transport
through the bloodstream. Erythrocytes account
for 99 percent of the blood cells the blood carries.
Erythrocytes lack nuclei, which means they
cannot proliferate (reproduce). They have a life-
span of about 120 days. The BONE MARROWthus
must continuously produce erythrocytes, which it
does at the rate of about 2 million per minute. The
SPLEENand the LIVERfilter aging, deteriorating, and
defective erythrocytes from the blood circulation.
Men have a somewhat higher percentage of ery-
throcytes in their blood, about 47 percent, than
women, who have about 42 percent, primarily
because women lose blood each month with MEN-
STRUATION. The number of erythrocytes in both
men and women begins to decline after age 70
because erythropoiesis slows as a natural aspect of
aging.
For further discussion of erythrocytes within
the context of blood and lymph structure and
function please see the overview section “The
Blood and Lymph.”
See also HEMATOPOIESIS; OXYGEN–CARBON DIOXIDE
EXCHANGE.erythropoiesis See HEMATOPOIESIS.erythropoietin (EPO) A HORMONE the KIDNEYS
produce that stimulates the BONE MARROW to
increase red BLOODcell production. EPO is a pro-
tein structure called a CYTOKINE. Specialized cells in
the renal cortex, called peritubular fibroblasts,
respond to the amount of oxygen in the blood as
it passes through the kidney. When the oxygen
saturation of the blood is low (HYPOXIA), the per-
itubular fibroblasts increase EPO production. Nor-
mally the bone marrow releases about two million137