Page 38 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

P. 38

3 Blood S. Silbernagl

Overview
Total blood volume correlates with the (fat- tion. Finally, numerous plasma proteins partic-
free) body mass (→ Table below) and averages ipate in blood clotting and fibrinolysis. When
3.6 L in women and 4.5 L in men. The blood’s blood clots, the fibrinogen in plasma is used
tasks include transporting various substances up and serum is formed.
(O 2 , CO 2 , nutrients, metabolic products, vita- Formation of blood cells (→ A). The hemato-
mins, electrolytes, etc.), the transport of heat poietic tissue, i.e., red bone marrow in adults,
(heating, cooling), signal transmission (hor- the spleen and liver in the fetus, contain pluri-
mones), and buffering as well as defense potent stem cells that, under the effect of he-
against foreign materials and microorganisms. matopoietic growth factors (see below), differ-
The blood cells (→ A and Table below) are in- entiate into myeloid, erythroid, and lymphoid
volved in this, the erythrocytes being responsi- precursor cells. These stem cells reproduce in
ble for O 2 and CO 2 transport and a part of pH such a way that their stock is maintained
buffering. Among the leukocytes, the neutro- throughout life (→ p. 2ff.). While the lympho-
phil granulocytes (neutrophils) are responsible cytes that originate from the lymphoid precur-
for nonspecific immune defenses, and the sors still require further maturation (partly in
monocytes and lymphocytes for specific im- the thymus, partly in the bone marrow) and
mune reactions. The thrombocytes (platelets) are later on formed in the spleen and the
are important for hemostasis. The ratio of lymph nodes (lymphopoiesis), all other precur-
blood cell volume to total blood volume is sor cells proliferate and mature up to their fi-
called hematocrit (Hct) (→ p. 31 A). More than nal stage in the bone marrow (myelopoiesis),
99% of the Hct is made up of erythrocytes. until they finally pass from there into the
In the fluid phase of blood, called plasma, blood (→ A). Among other factors, two renal
electrolytes, nutrients, metabolic products, vi- hormones are involved in this, namely erythro-
tamins, gases and proteins are held in solution poietin for the maturation and proliferation of
(→ Table). Among the tasks of the plasma pro- erythrocytes (→ A and p. 32), and thrombo-
teins are humoral immune defense, mainte- poietin for megakaryocytes and thrombocytes,
nance of colloidal osmotic (oncotic) pressure, respectively (→ A). There are additional para-
which is responsible for maintaining a con- crine factors that regulate blood cell formation
stant blood volume, as well as the transport of in the bone marrow. Because of their action in
water-insoluble materials and the protection cell culture, they are sometimes also called col-
of various substances against their breakdown ony-stimulating factors (CSFs). Other stem cell
in blood, and their excretion by the kidneys growth factors are stem cell factor (SCF = steel
(e.g., heme). This protein-binding of small factor = c-kit ligand) and fit3 ligand (FL). They
molecules lowers their osmotic power, while trigger the release of synergistically active fac-
they can acquire an antigenic effect (→ p. 52f.) tors, such as CSF and interleukins (IL-3, IL-6,
as haptens. The coupling of hormones, drugs, IL-11, IL-12) and are inhibited, among others,
and toxins to plasma proteins reduces their by transforming growth factor β (TGF-β) and
signaling, therapeutic, or toxic action, while at tumor necrosis factor α (TNF-α).
the same time preventing their rapid excre-

Total Blood Blood volume (L) < 0.041 · kgKG + 1.53; , 0.047 · kgKG + 0.86
Hematocrit (L cells /L blood ) < 0.40–0.54; , 0.37–0.47
Erythrocytes Number (10 12 /L blood = 10 6 / µl blood ) < 4.6–6.2; , 4.2–5.4
Hemoglobin (g/L blood ) < 140–180; , 120–160
Leukocytes Number (10 9 /L blood = 10 3 / µL blood ) 3–11 (of which 63% granuloc., 31% lymphoc., 6% monoc.)
Thrombocytes Number (10 9 /L blood = 10 3 / µL blood ) < 170–360; , 180–400
28 Plasmaproteins (g/l Serum) 66–85 (of which 55–64% albumin)

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