Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Blood Composition

The only fluid tissue in the
human body

Classified as a connective
tissue
• Living cells = formed
elements
• Non-living matrix =
plasma

Color range
• Oxygen-rich blood is
scarlet red
• Oxygen-poor blood is dull
red

pH must remain between
7.35–7.45

Blood temperature is slightly
higher than body temperature
Hematocrit: Percent of blood volume that is RBCs
•
47% ± 5% for males
•
42% ± 5% for females
Figure 10.1
Blood Cell Types
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Erythrocytes (Red Blood Cells)
 Main function is to carry oxygen
 Biconcave disks
 Essentially bags of hemoglobin;
few organelles
 Anucleate (no nucleus)
 Outnumber white blood cells
1000:1
 Contain the plasma membrane
protein spectrin and other
proteins
 Major factor contributing to
blood viscosity
Hemoglobin
 Molecular structure
• Protein globin: two alpha
and two beta chains
• Heme pigment bonded to
each globin chain
 Iron atom in each heme can
bind reversibly to one O2
molecule
 Each Hb molecule can
transport four O2
Sickle Cell Hemoglobin Causes Clotting

Normal hemoglobin = HbA

Sickle cell hemoglobin = HbS (mutation in single amino acid - missense)
Pleiotropic Effects Seen if HbS present
HbAHbA = normal
HbAHbS = sickle
cell trait
HbSHbS = sickle
cell
disease/anemia
Fetal Hemoglobin Binds O2 More Avidly
 Fetal circulation must
extract oxygen from
maternal circulation
 Fetal hemoglobin (HbF)
binds O2 more avidly than
normal hemoglobin (HbA)
does
 Replaced by “adult”
hemoglobin just after birth
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Leukocytes (White Blood Cells)
Differential
WBC count
(All total 4800 –
10,800/l)
Formed
elements
Platelets
Leukocytes
Granulocytes
Neutrophils (50 – 70%)
Eosinophils (2 – 4%)
Basophils (0.5 – 1%)
Erythrocytes
Agranulocytes
Lymphocytes (25 – 45%)
Monocytes (3 – 8%)
Figure 17.9
Leukocyte Levels in the Blood
 Normal levels are between 4,000 - 11,000 cells per millimeter
 Abnormal leukocyte levels
• Leukocytosis
o Above 11,000 leukocytes/ml
o Generally indicates an infection (bacterial, fungal, parasitic)
o Also caused by some cancers, (including lymphocyte leukemia),
hemhorrage, pneumonia
• Leukopenia
o Abnormally low leukocyte level (< 3,500/ml)
o Commonly caused by certain drugs, radiation
o Neutropenia (low neutrophil count) common in cancer patients
receiving chemotherapy
o HIV-AIDS, TB, malaria, influenza also cause leukopenia
o Requires careful sanitation and “gowning up” for medical staff
Types of Leukocytes
 Granulocytes
• Granules in their
cytoplasm can be
stained
• Include neutrophils,
eosinophils, and
basophils
 Agranulocytes
• Lack visible
cytoplasmic granules
• Include lymphocytes
and monocytes
Figure 10.4
Characteristics of Formed Elements of the Blood
N
E
B
Characteristics of Formed Elements of the Blood
L
M
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Hematopoiesis
 Subdivided into erythropoesis and leukopoesis
 Erythropoesis ccurs in red bone marrow
 Erythropoesis Steps
1. Ribosome synthesis
2. Hemoglobin accumulation
3. Ejection of the nucleus and formation of
reticulocytes
4. Reticulocytes then become mature
erythrocytes
Stem cell
Hemocytoblast
Committed
cell
Developmental pathway
Proerythroblast
Early
Late
erythroblast erythroblast
Phase 1
Ribosome
synthesis
Phase 2
Hemoglobin
accumulation
Phase 3
Ejection of
nucleus
Normoblast
Figure 17.5
Reticulo- Erythrocyte
cyte
Fate of Erythrocytes
 Unable to divide, grow, or
synthesize proteins
 Wear out in 100 to 120 days
 When worn out, are eliminated by
phagocytes in the spleen or liver
• Iron is salvaged for reuse
• Heme is degraded to yellow
the pigment bilirubin
• Liver secretes bilirubin (in
bile)) into the intestines
 Lost cells are replaced by division
of hemocytoblasts
Control of Erythrocyte Production
 Rate is controlled by a
hormone (erythropoietin)
 Kidneys produce most
erythropoietin as a
response to reduced
oxygen levels in the
blood (hypoxia)
 Hypoxia can develop
from hemorrhage, low O2
in air, insufficient
hemoglobin
 Homeostasis is
maintained by negative
feedback from blood
oxygen levels
Platelets Important in Clotting
 Small fragments of megakaryocytes
 Formation is regulated by thrombopoietin
 Blue-staining outer region, purple granules
 Form a temporary platelet plug that helps seal breaks in blood
vessels
Stem cell
Hemocytoblast
Developmental pathway
Megakaryocyte
Platelets
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Hemastasis: Blood Clotting
Step 1 Vascular spasm
• Smooth muscle contracts,
causing vasoconstriction.
Step 2 Platelet plug formation
Collagen
fibers
• Injury to lining of vessel
exposes collagen fibers;
platelets adhere.
• Platelets release chemicals
that make nearby platelets
sticky; platelet plug forms.
Platelets
Fibrin
Step 3 Coagulation
• Fibrin forms a mesh that traps
red blood cells and platelets,
forming the clot.
Figure 17.13
Hemastasis
Undesirable Clotting
 Thrombus
• A clot in an unbroken blood
vessel
• Can be deadly in areas like
the heart
 Embolus
• A thrombus that breaks
away and floats freely in
the bloodstream
• Can later clog vessels in
critical areas such as the
brain, causing a stroke
(CVA)
Bleeding Disorders
 Thrombocytopenia
• Platelet deficiency
• Even normal movements can
cause bleeding from small blood
vessels that require platelets for
clotting
 Hemophilia
• Hereditary bleeding disorder
• Normal clotting factors are
missing or deficiency in Vit. K.
mild hemophilia
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood
Blood Groups and Transfusions
 Large losses of blood have
serious consequences
• Loss of 15 to 30 percent
causes weakness
• Loss of over 30 percent
causes shock, which can be
fatal
 Transfusions are the only way to
replace blood quickly
 Transfused blood must be of the
same blood group
Human Blood Groups
 Blood contains genetically
determined proteins
 A foreign protein (antigen) on
a donated RBC may be
attacked by the immune system
 Blood is “typed” by using
antibodies that will cause blood
with certain proteins to clump
(agglutination)
Human Blood Groups
 There are over 30 common red blood cell antigens
 The most vigorous transfusion reactions are caused by ABO
and Rh blood group antigens
ABO Blood Groups and Alleles
Components of
Blood of this Type
anti-A
anti-B
anti-B
anti-A
Rh Blood Groups and Hemolytic Deaseas of Newborns
 Named because of the presence or
absence of one of eight Rh antigens
(agglutinogen D)
Dd
dd
 Most Americans are Rh+
 The danger is only when the mother
is Rh– and the father is Rh+, and the
child inherits the Rh+ factor
• Problems can occur in second and
subsequent pregnancies when the
baby’s Rh+ blood enters Rh– maternal
circulation: erythroblastosis fetalis
(hemolytic disease of the newborn)
• RhoGAM injections contain anti-Rh
antibodies that quickly clear the
maternal circulation of Rh protein
Dd
dd
This baby, if from
the second or
subsequent
pregnancy, could
have
complications in
an Rh- mother
Blood Composition and Function
 General Composition of Blood
• Plasma
• Formed Elements
 Erythrocytes
 Leukocytes
 Hematopoesis
 Hemostasis (Clotting)
 Transfusion and Blood Typing
 Developmental Aspects of Blood