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Blood
Chapter 17
Blood Composition and Characteristics
Major Components:
Plasma
Leukocytes
Platelets
Erythrocytes
Hematocrit = % RBC volume of total blood volume.
Females have about 42%, males have about 47% (+/- 5%)
Fig 17.1
Figure 17.1
Blood Composition and Characteristics
Characteristics of Blood:
Denser, more viscous than water
Volume of blood: 4-5L (F), 5-6L (M).
Normal pH: 7.35 – 7.45
Functions of Blood
1. Distribution
Delivery of O2 and other nutrients to all cells of the body
Transport of metabolic wastes to sites of elimination
Transport of hormones to target organs
2.
Regulation
Maintaining body temperature
Maintaining pH of tissues via protein buffers and bicarbonate
Maintaining proper fluid volume in circulatory system and tissues
3. Protection
Preventing blood loss through hemostasis
Preventing infection via antibodies, complement, and WBCs
Plasma Composition
Water
90% of plasma volume
Solutes
10% of plasma volume
~8% Proteins
Globulins- transport proteins (eg. albumin)
and antibodies (immunoglobulins)
Clotting proteins (eg. fibrinogen)
Others: enzymes, hormones
Metabolic wastes
~2% Nutrients
Electrolytes
Respiratory Gases
urea, lactic acid, creatinine
glucose, amino acids, vitamins, lipids
Na+,K+,Ca2+, Cl-, P04-, bicarbonate
O2, CO2
Blood Cells/Formed Elements
Erythrocytes-Red Blood Corpuscles
Characteristics: biconcave shape, ~7.5 mm diameter
5 million/microliter
Function: respiratory gas tranpsort, via
binding/unbinding to hemoglobin. (O2 and CO2)
Hemoglobin: protein globin + heme pigment
Contained within erythrocytes @ 12-20 g/100 ml blood
4 globin subunits/Hb; each one has 1 heme that binds 1 O2 molecule.
Fig. 17.2
Erythrocytes-Red Blood Corpuscles
Characteristics: biconcave shape, ~7.5 mm diameter
Function: respiratory gas transport via binding/unbinding to hemoglobin
(O2 and CO2)
Hemoglobin: protein globin + heme pigment
contained within erythrocytes
4 globin subunits/Hb; each one has 1 heme that binds
1 O2 molecule
Oxygen-Hemoglobin dissociation curve
Erythrocytes
Erythropoesis: genesis of red blood cells
begins with hemocytoblast stem cell
stimulated by erythropoetin released from the
kidneys
erythropoetin (EPO)-glycoprotein hormone
released predominantly from the kidneys but
also from the liver
Recombinant products: Epogen or procrit.
Fig 17.6
Erythrocytes
Fate and Destruction:
life time- 100-120 days
degraded in the spleen,liver by macrophages
iron released from heme and recycled
remainder of heme-degraded to

converted to bile by the liver
Leukocytes- White blood cells
Granulocytes- contain cytoplasmic granules that stain with Wright’s
stain; often lobed nuclei
neutrophils- most numerous WBCs; also called (polymorphonucleocytes)
function in inflammation and destroy bacteria via
defensins (proteins) and phagocytosis
eosinophils- attack parasitic worms by releasing enzymes from granules,
also destroys Ag/Ab complexes.
basophils- release the inflammatory chemical histamine from granules
Leukocytes-White blood cells
Agranulocytes- lack visible cytoplasmic granules
spherical or kidney-shaped nuclei
lymphocytes- most live in lymphoid tissue, but some
circulate in the blood
T & B lymphocytes
monocytes-differentiate into macrophages within tissues
(phagocytic cells)
Production of Leukocytes
Hemocytoblast
Myeloid stem cell
Lymphoid stem cell
Platelets
Platelets: cytoplasmic fragments of megakaryocytes that play a
role in blood clot formation
also called thrombrocytes
Production of platelets: stimulated by thrombopoietin (Tpo)
Hemocytoblast
Megakaryocyte fragmentation
platelets
Hemostasis- Complex series of reactions that stop bleeding after a blood
vessel is injured; involves numerous clotting factors (including fibrinogen,
prothrombin, Ca2+)
optional
Blood Types
optional reading
pp 654-658