CHAPTER 14: BLOOD
OBJECTIVES:
1.
Describe blood according to its tissue type and major functions.
2.
Define the term hematology.
3.
Name the average volume of blood in a human.
4.
Name the two major components of blood and the percentage of each by weight.
5.
Give the common and scientific name for the three types of blood cells, and describe each
in terms of their circulating concentration in a normal individual, overall function, and
key characteristics.
6.
Explain why a mature erythrocyte lacks a nucleus.
7.
Explain why red blood cells have a relatively short life span.
8.
Discuss where erythropoiesis occurs in adults and fetuses, and what other factors are
needed for red cell production.
9.
Outline the negative feedback loop involving the hormone erythropoietin.
10.
Explain why the solid portion of blood, formed elements, packed cell volume, or
hematocrit are all composed of approximately 99% erythrocytes.
11.
Distinguish between granulocytes and agranulocytes, name the leukocytes in each
category, and list the specific function for each cell type.
12.
Name the process by which a leukocyte leaves the blood stream and enters a tissue (Is
this normal?).
13.
Name the primitive bone marrow cell from which all blood cells arise.
14.
List the components transported in blood plasma.
15.
Outline and explain the three steps involved in hemostasis.
16.
Name the hormone that platelets within a platelet plug release that causes further
vasoconstriction of a vessel.
17.
Describe the final step in blood coagulation.
18.
Name the natural anticoagulant released by basophils and mast cells.
19.
Define the term agglutination.
20.
Discuss blood typing (A, B, AB, O) and transfusions in terms of the following:
a.
b.
c.
d.
the antigen present on a person's (recipient's) erythrocytes;
the antibodies within the person's (recipient's) plasma;
compatible donor types;
incompatible donor types.
21.
Identify the blood type considered the universal donor and the blood type considered the
universal recipient.
22.
Discuss what is meant by Rh incompatibility and its consequences.
CHAPTER 14: CARDIOVASCULAR SYSTEM: BLOOD
I.
BLOOD AND BLOOD CELLS
Blood is a connective tissue whose cells are suspended in liquid called plasma.
Functions of blood include transporting substances between body cells and the outside,
maintaining homeostasis and protection.
Hematology is the study of blood, blood-forming tissues and the disorders that affect
them.
II.
BLOOD VOLUME AND COMPOSITION:
A.
Blood volume varies from individual to individual, but the average volume (70
kg male) is 5 liters.
B.
Blood can be separated into two major components:
See Fig 14.1, page 511.
1.
Blood cells or "formed elements" (45%), which is composed mainly of
red blood cells.
a. Quantitative analysis of this portion of blood represents the
hematocrit (HCT) reading or packed cell volume (PCV).
b. See Fig 14.2, page 511.
2.
III.
Plasma (55%), liquid that contains water, electrolytes, hormones, wastes,
proteins and much more (discussed in greater detail later).
BLOOD CELLS or "Formed Elements":
Blood is composed of three types of cells, including red blood cells, white blood cells,
and platelets. See Fig 14.1, page 511.
A.
The Origin of Blood Cells
1.
Hematopoietic Stem Cells in bone marrow of adults
2.
Specific types of Colony Stimulating Factors produce
differentiation resulting in specific types of cells.
3.
ALL BLOOD CELLS ARE FORMED FROM THE SAME LARGE
PRIMITIVE CELL CALLED A HEMOCYTOBLAST .
See Fig 14.3, page 512.
III.
BLOOD CELLS or "Formed Elements":
B.
Characteristics of Red Blood Cells (RBC) = Erythrocytes
See Fig 14.4, page 513.
1.
C.
2.
compose 99% of blood cells.
3.
contain hemoglobin, which is loosely bound to oxygen.
See Fig 14.8, page 518.
a.
Hemoglobin = protein (globin) + heme (iron);
b.
oxyhemoglobin = bright red;
c.
deoxyhemoglobin = darker red, purple
4.
Mature cells lack nuclei (i.e. are anucleate), leaving more room for
hemoglobin/oxygen;
Red Blood Cell Counts
1.
D.
E.
III.
s (increased surface area);
RBC Count (RCC) = the number of rbc's/mm3 blood.
a.
Average RCC = 4 million-6 million rbc's/mm3;
Red Blood Cell Production and Its Control
1.
Production (Erythropoiesis)
a.
In fetuses = yolk sac, liver, spleen;
b.
In adults = red bone marrow;
2.
Control of Production
Number normally remains stable.
a.
Negative feedback mechanism involving the hormone
erythropoietin, which is produced and secreted by the special
cells in the kidney and liver.
b. See Fig 14.5, page 514, and Table 14.1, page 515.
o
Chemoreceptors in kidney and liver detect low blood
oxygen,
o
Erythropoietin is released from kidney and liver into
circulation,
o
Erythropoietin targets red bone marrow, stimulating
erythropoiesis.
Dietary Factors Affecting RBC Production
1.
B12, folic acid, and iron are all needed.
2.
Intrinsic Factor is secreted by stomach allowing B12 absorption
3.
Lack of proper nutrients leads to anemia
BLOOD CELLS or "Formed Elements":
F.
Destruction of RBCs
Average life-span = 120 days
1.
Liver and spleen macrophages destroy worn RBC,
2.
Hemoglobin is broken into globin and heme,
3.
Iron in Hb is recycled,
4.
Heme is broken into biliverdin > bilirubin > bile.
5.
See Table 14.4, page 517 and Fig 14.6, page 515.
G.
Types and Function of WBC’s
White Blood Cells (WBC) = Leukocytes
See Figures 14.9-14.13, pages 519-520.
Leukocytes function to control disease:
Most only live a few days (except lymphocytes). Leukocytes are divided into
granulocytes and agranulocytes:
1.
Granulocytes
o
o
o
o
a.
Neutrophils
most abundant WBC = 54%-62%;
polymorphonucleocytes (PMN);
phagocytosis of foreign particles (disease organisms &
debris);
increased in acute bacterial infections.
c. Eosinophils
o
1-3% of total WBC's;
o
kill parasites and are responsible for allergic reactions;
o
increased during parasitic infections (tapeworm,
hookworm);
o
Release histamine during allergic reactions.
d. Basophils
o
<1% of total WBC's;
o
release heparin which inhibits blood clotting;
o
release histamine, a vasodilator helpful inflammatory
responses (increases blood flow to damaged tissue).
o
may leave bloodstream and develop into mast cells
(antibodies attach and cause mast cell to burst, releasing
allergy mediators).
III.
BLOOD CELLS or "Formed Elements":
G.
H.
I.
Types and Function of WBC’s
2.
Agranulocytes
a.
Monocytes
o
3-9% of total WBC's;
o
phagocytosis;
o
largest WBC, 12-20 microns,
o
In blood = phagocyte; In tissues = macrophage;
o
increased
during typhoid
fever,
malaria,
and
mononucleosis.
b.
Lymphocytes
o
25-33% of total WBC's;
o
live for several months to years;
o
range in size from large (10-14) to small (6-9);
o
attack cells directly
 T-cells
o
produce antibodies that act against specific foreign
substances (immunity);
 B-cells
o
increased during TB, whooping cough, viral infections,
tissue rejection reactions, and tumors.
3.
Diapedesis = process by which leukocytes move through blood vessel
walls to enter tissues;
See Fig 14.14, page 520.
WBC Counts
1.
Average WBC count (WCC) = 5000-10,000 WBC’s / mm3 blood;
a.
Number of WBC’s increases during infections;
o
leukocytosis = WCC > 10000;
o
leukopenia = WCC < 5000;
2.
Differential WCC indicates % of each particular leukocyte;
3.
Leukemia = abnormal (uncontrolled) production of specific types of
immature leukocytes (see below).
Blood Platelets = thrombocytes
1.
Fragments of giant cells called megakaryocytes;
2.
Normal count = 130,000-360000 platelets/ mm3 blood;
3.
Function = blood clotting (will be discussed in more detail later).
See Summary of Formed Elements in Table 14.6, page 523.
Major Blood Cell Summary Table (Keyed on last page of this outline)
Major Blood Cell
Type
Scientific Name
Circulating
Concentration/
mm3 blood
General Function
Key Characteristics
White Blood Cell Summary Table (Keyed on last page of this outline)
Specific WBC
Function/
Event of Increase?
Differential %
Typical Sketch
IV.
BLOOD PLASMA (See Fig 14.1 page 511, Fig 14.2, page 511, Fig 14.16, page 524).
Blood plasma is clear, yellow liquid, composed of proteins,
nutrients, gases, electrolytes, and many more substances.
A.
1.
2.
1.
2.
3.
C.
WATER:
92 %.
Functions as solvent, in transport, temperature regulation, and serves as
site of metabolic reactions.
B.
Plasma Proteins:
See Table 14.7, page 524.
7% of plasma volume
all produced in the liver.
Three types:
a.
albumin;
o
maintains osmotic pressure of cells (0.9%) and
o
transports fatty acids;
b.
globulins ( α, β , γ );
o
antibodies;
c.
fibrinogen;
o
blood clotting.
Plasma Gases:
1.
oxygen (needed for cellular respiration),
2.
carbon dioxide (produced by cell respiration),
3.
nitrogen (use unknown).
D.
2.
3.
E.
2.
3.
4.
5.
F.
2.
G.
2.
Plasma Nutrients:
1.
amino acids,
monosaccharides (i.e. glucose),
lipoproteins: See Table 14.8, page 526.
Nonprotein Nitrogenous Substances (Plasma Wastes):
1.
urea (amino acid metabolism),
uric acid (nucleotide metabolism),
creatinine (creatine metabolism),
creatine (CP to recycle ADP to ATP in muscle & brain),
bilirubin (hemoglobin metabolism).
Plasma Electrolytes:
1.
includes sodium, potassium, calcium, magnesium, chloride,
bicarbonate, phosphate, and sulfate;
Maintain osmotic pressure, Resting Membrane Potential, and pH.
Regulatory Substances:
1.
enzymes,
hormones.
V.
HEMOSTASIS = stoppage of bleeding from a blood vessel.
A.
V.
3 steps involved:
See Table 14.9, page 527.
1.
Blood vessel spasm (vessel walls constrict);
a.
vasospasm
b.
reduces blood flow
2.
Platelet plug formation
See Fig 14.17, page 527.
a.
platelets become sticky and adhere to one another
b.
platelets also release the hormone serotonin, which causes further
vasoconstriction of the vessel;
3.
blood coagulation = formation of a blood clot;
a.
complex cascade of events (positive feedback mechanism);
b.
requires calcium ions;
c.
2 possible starting pathways
o
Extrinsic Clotting Mechanism

Starts when platelet contacts damaged tissue or
tissue outside of blood vessel (hence, extrinsic)

Cascade leads to prothrombin activator (PA)
release by platelets

PA and Ca2+ cause prothrombin to convert to
thrombin

Thrombin catalyzes the polymerization of
fibrinogen to fibrin

Fibrin threads make up meshwork of clot
o
Intrinsic Clotting Mechanism (all factors normally found in
blood)

Starts when blood contacts a foreign substance

Cascade again leads to same final steps as above

Cascade leads to prothrombin activator (PA)
release by platelets

PA and Ca2+ cause prothrombin to convert to
thrombin

Thrombin catalyzes the polymerization of
fibrinogen to fibrin

Fibrin threads make up meshwork of clot
d.
Final step = fibrinogen
fibrin.
e.
See scanning electron micrograph, Fig 14.18, page 528.
f.
See Fig 14.19, page 529
HEMOSTASIS
B.
Fate of Blood Clots and Prevention of Coagulation (Fibrinolytic System)
1.
2.
3.
Fibrinolytic system provides checks and balances so that blood clotting
does not go awry
Thrombus = abnormal clot
Embolus = floating clot (abnormal)
Embolism = when embolus gets lodged in a small vessel obstructing
blood flow
Fibrinolytic substances include:
a.
b.
c.
tissue plasminogen activator (TPA):
o
naturally produced
o
Also injected quickly after MI to dissolve coronary
thrombus(i).
o
See blue box on page 530.
Heparin is an anticoagulant:
o
naturally produced by basophils and mast cells;
o
Also used a pharmacologic agent extracted from lung
tissues of animals;

used during open-heart surgery and hemodialysis.
Warfarin (Coumadin) is another anticoagulant:
o
given to patients prone to thrombosis;
o
slower acting than heparin.
See Clinical Application 14.3, page 532, concerning Medicinal Uses of the
Leech.
VI.
BLOOD GROUPS/TRANSFUSIONS
A.
Significance
2.
3.
*
B.
1.
There are antigens present on the cell membrane surface of
our erythrocytes (red blood cells).
Our plasma contains substances called antibodies that are produced
against non-self antigens.
If the RBCs antigen (donor) and plasma antibody (recipient) are the same,
the serious condition of hemolysis (bursting) of rbc's will occur.
In the laboratory, this situation can be simulated, however the result is
termed agglutination = clumping of red blood cells.
ABO Blood types:
2.
3.
1.
inherited trait;
determined by the antigens on a person's RBC;
4 types: A, B, AB, O
b.
c.
d.
4.
See Fig 14.21, page 534 and Table 14.13, page 534.
a.
Type A blood = antigen A on rbc's;
Type B blood = antigen B on rbc's;
Type AB blood = both antigen A & B on rbc's;
Type O = neither A or B antigen on rbc's.
Antibodies in plasma: (See above figure)
a.
Shortly after birth, we spontaneously
develop antibodies against RBCs antigens, that are not our own.
b.
Antibodies formed include:
o
Persons with Type A blood, develop Anti-B antibodies;
o
Persons with Type B blood, develop Anti-A antibodies;
o
Persons with Type AB blood, do not develop either Anti-A
or Anti-B antibodies;
o
Persons with Type O blood, develop both Anti-A and AntiB antibodies.
VI.
BLOOD GROUPS/TRANSFUSIONS (continued):
C.
Summary of ABO Interactions: (This Table is keyed at the end of this outline)
When considering blood transfusion reactions, the most important factor to
consider is the antibodies present in the recipient's plasma!
BLOOD TYPE
ANTIGEN ON
RBC'S
ANTIBODIES
IN PLASMA
COMPATIBLE
DONORS
INCOMPATIBLE DONORS
GENOTYPE
PHENOTYPE
*
A person with type O blood is considered the universal donor.
*
A person with type AB blood is considered the universal recipient.
VI.
BLOOD GROUPS/TRANSFUSIONS (continued):
D.
Rh Factor:
1.
inherited trait;
2.
studied in rhesus monkeys (thus, Rh);
3.
group of antigens present on rbc's = Rh positive;
lack of antigens on rbc's = Rh negative;
4.
Rh antibodies do not form spontaneously, but will form in Rh-negative
persons in response to stimulation:
5.
a.
Initial exposure (transfusion, etc.) does not produce harmful
effects, however the Rh-negative person has now been sensitized
(i.e. they can produce anti-Rh antibodies);
b.
Additional exposure (transfusion, etc.) causes serious hemolysis to
occur.
Erythroblastosis fetalis = hemolytic disease of the newborn (HDN)
See Figure 14.23, page 536.
a.
Scheme:
o
o
o
o
o
b.
Rh-negative mother becomes pregnant with Rh-positive
fetus;
Pregnancy uneventful, but during birth, baby's blood enters
the mother's circulation and causes her to produce anti-Rh
antibodies;
Mother conceives a second Rh-positive fetus;
Mother's anti-Rh antibodies can now pass through the
placenta and enter the fetus’ circulation;
The fetus’ rbc's hemolyze resulting in this fatal condition.
Usually, no longer a significant problem because of the
administration of a drug called RhoGAM, which destroys the
mother's anti-Rh antibodies before they can cross the placenta and
destroy the fetus’ red blood cells.
VII.
VIII.
Blood Disorders
A.
Sickle Cell Disease. See blue box on page 513.
B.
Hemochromatosis. See blue box on page 517.
C.
Chronic Granulomatous Disease. See blue box on page 518.
D.
King George III and Porphyria. See Clinical Application 14.1, page 517.
E.
Types of Anemias. See Table 14.3, page 516, blue box on page 516, and Fig
14.7, page 516.
F.
Leukemia. See Clinical Application 14.2, page 522.
G.
Edema. See blue box on page 524.
H.
DIC, Disseminated intravascular clotting. See blue box on page 528.
I.
Atherosclerosis. See Fig 14.20, page 531.
J.
Thrombocytopenia. See blue box on page 531.
K.
Hemophilia. See Clinical Application 14.4, page 533.
Other Interesting Topics
A.
IX.
The Medicinal Leech. See Clinical Application 14.3, page 532.
Clinical Terms Related to the Blood
See Page 537.
Major Blood Cell Summary Table
Major Blood Cell
Type
red blood cell
white blood cell
platelet
Scientific Name
erythrocyte
leukocyte
thrombocytes
Circulating
Concentration/
mm3 blood
4-6 million/
mm3 blood
5-10,000/
mm3 blood
130,000-360,000/
mm3 blood
General Function
transportation of
oxygen
fight infection
blood clotting
Key Characteristic
see page 4
see page 5-6
are fragments of
giant megakaryocyte
White Blood Cell Summary Table)
Specific WBC
Function/
Event of Increase?
Differential %
Typical Sketch (refer to
text)
neutrophil
general phagocytosis;
acute bacterial infections
54%-62%
see page 519
eosinophil
kills parasites; involved in
inflammation and allergic
reactions
1%-3%
see page 519
basophil
Inflammatory reactions: releases
heparin (natural anticoagulant)
and histamine (inflammation)
less than 1%
see page 519
monocyte
phagocytosis of large particles;
typhoid, malaria, mononucleosis
3%-9%
see page 519
lymphocyte
produce antibodies/immunity;
viral infections, tissue rejection,
tumors, TB, whooping cough
25%-33%
see page 520
Summary of ABO Interactions
BLOOD TYPE
A
B
AB
O
Antigen on rbc’s
A
B
A and B
neither A or B
Antibodies in plasma
B
A
neither A or B
both A and B
Compatible donors
A, O
B, O
AB, A, B, O
O
Incompatible donors
B, AB
A, AB
NONE
A, B, AB
Genotype
IAIA OR IAi
IBIB, IBi
IAIB
ii
Phenotype
type A
type B
type AB
type O
Chapter 14 Blood
1. List the major components of blood.
The blood consists of red blood cells, white blood cells, platelets, and plasma (the liquid
portion).
2. Define hematocrit, and explain how it is determined.
Hematocrit (HCT) is the percentage of the cells in a blood sample. This is obtained by
allowing the sample to stand (clotting is prevented), allowing the cells to separate and
sink to the bottom. This is further centrifuged and the percentage of the cells and
liquid is determined.
3. Describe a red blood cell.
A red blood cell is a biconcave disk that has no nucleus.
4. Distinguish between oxyhemoglobin and deoxyhemoglobin.
Oxyhemoglobin is hemoglobin combined with oxygen. Deoxyhemoglobin is hemoglobin
that has released its oxygen.
5. Explain what is meant by a red blood cell count.
A red blood cell count is the number of red blood cells in a cubic millimeter (mm3) of
blood.
6. Describe the life cycle of a red blood cell.
a. Nutrients from food are absorbed from the small intestine into the bloodstream.
b. The blood transports the absorbed nutrients to the red bone marrow tissue.
c. The red bone marrow produces red blood cells.
d. The red blood cells circulate for about 120 days.
e. Damaged and old red blood cells are destroyed in the liver.
f. The resulting biliverdin is converted to bilirubin that is excreted in the bile from the liver.
7. Define erythropoietin, and explain its function.
Erythropoietin is a hormone that is released from the kidneys, and to a lesser extent
the liver, which stimulates red blood cell production.
8. Explain how vitamin B12 and folic acid deficiencies affect red blood cell production.
Both substances are required for DNA synthesis that is needed by all cells for growth
and reproduction. Hematopoietic tissue reproduces at a particularly high rate, so this
tissue is especially affected by the lack of either vitamin.
9. List two sources of iron that can be used for the synthesis of hemoglobin.
Obtaining vitamin C in the diet will increase iron absorption from the small intestine.
It is also conserved from the red blood cell destruction and reused.
10. Distinguish between biliverdin and bilirubin.
Biliverdin is the greenish pigment that results when the heme portion of the
hemoglobin breaks apart. Bilirubin is what biliverdin eventually converts to over time.
11. Distinguish between granulocytes and agranulocytes.
A granulocyte is a white blood cell that has granular cytoplasm. Agranulocytes are
white blood cells that lack cytoplasmic granules.
12. Name five types of leukocytes, and list the major functions of each type.
a. Neutrophils are granulocytes that function to phagocytize foreign particles.
b. Eosinophils are granulocytes that function to kill certain parasites and help control allergic reactions.
c. Basophils are granulocytes that function to release heparin that inhibits blood clotting. They also release
histamine to cause inflammation.
d. Monocytes are agranulocytes that leave the bloodstream to function as macrophages that phagocytize
foreign particles.
e. Lymphocytes are agranulocytes that function to produce antibodies that act against specific foreign
substances.
13. Explain the significance of white blood cell counts as aids to diagnosing diseases.
If there is a rise in white blood cells, there could be an infection of some type going on
within the body. If the white blood cell count drops, there could be an entirely different
set of diseases that could be going on within the body. A differential white blood cell
count measures the numbers of each specific type of white blood cell. This can signal a
specific disease process, as an increase in neutrophils usually means a bacterial
infection.
14. Describe a blood platelet, and explain its functions.
A blood platelet (thrombocyte) is a fragment of a cell. They function to initiate the
formation of blood clots.
15. Name three types of plasma proteins, and list the major functions of each type.
a. Albumins - help to maintain osmotic pressure of the blood.
b. Globulins - help to transmit lipids and fat-soluble vitamins and are the antibodies of immunity.
c. Fibrinogen - precursor to fibrin that has a major role in blood clotting.
16. Define lipoprotein.
A lipoprotein is a lipid and a protein joined together.
17. Define apoprotein.
An apoprotein is found within the protein surface layer of a lipoprotein. Apoproteins
function to combine with receptors on the membranes of specific target cells.
18. Distinguish between low-density lipoprotein and high-density lipoprotein.
Low-density lipoproteins have a relatively high concentration of cholesterol and are the
major cholesterol-carrying lipoproteins. High-density lipoproteins have a relatively
high concentration of proteins and a lower concentration of lipids.
19. Name the sources of VLDL, LDL, HDL, and chylomicrons.
VLDL is produced in the liver. LDL is the product of the enzyme lipoprotein lipase as
it breaks down the VLDL. HDL is produced in the liver and small intestine from the
remnants of LDL. Chylomicrons are produced by the liver and are the building blocks
from which the others are formed.
20. Describe how lipoproteins are removed from plasma.
The lipoproteins are pulled into the cells by receptor-mediated endocytosis and are
then used as needed elsewhere.
21. Explain how cholesterol is eliminated from plasma and from the body.
Much of the cholesterol is reabsorbed by the small intestine and transported back to
the liver. Some cholesterol, however, escapes reabsorption and reaches the large
intestine, where they are eliminated with the feces.
22. Define nonprotein nitrogenous substances, and name those commonly present in plasma.
A nonprotein nitrogenous substance is a molecule that contains nitrogen atoms but are
not proteins. Amino acids, urea, and uric acid are commonly present in the blood
plasma.
23. Name several plasma electrolytes.
These include sodium, potassium, calcium, magnesium, chloride, bicarbonate,
phosphate, and sulfate ions.
24. Define hemostasis.
Hemostasis refers to the stoppage of bleeding.
25. Explain how blood vessel spasms are stimulated following an injury.
Cutting or breaking a blood vessel stimulates the smooth muscles in its wall to
contract. This response may only last a few minutes but as the platelet plug forms,
serotonin is released, which causes the smooth muscles in the wall to contract further.
26. Explain how a platelet plug forms.
Platelets tend to stick to collagen fibers in connective tissue and any rough surface.
They also begin to stick to each other, forming the platelet plug.
27. List the major steps leading to the formation of a blood clot.
a. The production of a substance called prothrombin activator. This is dependent upon the presence of
calcium ions.
b. Tissue damage occurs and the clotting mechanism starts reactions, which also depend on the presence of
calcium. This leads to production of prothrombin activator, which converts prothrombin into thrombin.
c. Thrombin acts as an enzyme and causes a reaction in fibrinogen allowing it to become fibrin.
d. The fibrin threads stick to the exposed surfaces of the damaged blood vessels and create a meshwork in
which various blood cells and platelets become entangled. The resulting mass is the blood clot.
28. Indicate the trigger and outline the steps for extrinsic clotting and intrinsic clotting.
The trigger for extrinsic clotting is the blood vessel wall or tissue outside the blood
vessels contracting. The steps that follow are what were outlined in question 27. The
intrinsic clotting factors are all within the blood proper. The trigger is exposure of the
blood to a foreign surface such as collagen. Factor XII (the Hageman factor) then
activates factor XI, which in turn activates factor IX. Factor IX then joins with factor
VIII and platelet phospholipids to activate factor X. These reactions, for which calcium
is required, lead to the production of prothrombin activator. The extrinsic flow would
follow as previously described.
29. Distinguish between fibrinogen and fibrin.
Fibrinogen is the soluble precursor to the insoluble fibrin.
30. Describe a positive feedback system that operates during blood clotting.
Once a blood clot starts to form, it promotes still more clotting. This is due to the fact
that thrombin also acts directly on blood-clotting factors other than fibrinogen. It can
cause prothrombin to form still more thrombin. This is positive feedback.
31. Define serum.
Serum is essentially plasma minus all of its fibrinogen and most of the other clotting
factors.
32. Distinguish between a thrombus and an embolus.
A thrombus is a blood clot that forms in a vessel abnormally. An embolus is a blood
clot that becomes dislodged and is carried away by blood flow.
33. Explain how a blood clot may be removed naturally from a blood vessel.
Fibrin threads absorb a plasma protein called plasminogen. Then a substance called
plasminogen activator is released from the lysosomes of the damaged tissue cells that
converts plasminogen to plasmin. Plasmin is a protein-splitting enzyme that can digest
fibrin threads and other proteins associated with blood clots.
34. Describe how blood coagulation may be prevented.
The endothelium of blood vessels discourages the accumulation of platelets and clotting
factors. Endothelial cells also produce prostacyclin (PGI2), a prostaglandin, that
inhibits adherence of platelets to the inner surface of blood vessel walls. Antithrombin
that is present in the plasma globulins inactivates thrombin. Heparin is also released
from mast cells and basophils, which interferes with the formation of prothrombin
activator.
35. State a vitamin required for blood clotting.
Vitamin K is necessary for some clotting factors to function.
36. Distinguish between antigen and antibody.
An antigen that is present on the surface of red cell membranes. Antibodies are
proteins that are dissolved in the plasma.
37. Explain the basis of ABO blood types.
The ABO blood types are based on the presence or absence of two major antigens
(formerly called agglutinogens) on the red blood cells membranes. Their presence or
absence is determined by heredity. The two antigens are antigen A and antigen B. The
types of blood with the corresponding antigens are:
a.
b.
c.
d.
Type A - antigen A
Type B - antigen B
Type AB - antigen A and B
Type O - neither antigen A nor B
38. Explain why a person with the blood type AB is sometimes called a universal recipient.
Because blood type AB lacks both anti-A and anti-B antibodies, an AB person can receive blood of any type.
39. Explain why a person with blood type O is sometimes called a universal donor.
People with type O blood lack antigens A and B, which allows transfusion into persons
with blood of any other type. Type O blood does contain both anti-A and anti-B
antibodies so if transfused to another blood type it should be given slowly to minimize
the chance of an adverse reaction.
40. Distinguish between Rh-positive and Rh-negative blood.
Rh-positive blood is when the red blood cell membrane has Rh antigens (most
importantly antigen D) present. Rh-negative blood lacks the Rh antigens.
41. Describe how a person may become sensitized to Rh-positive blood.
A person may become sensitized to Rh-positive blood by receiving a transfusion.
42. Define erythroblastosis fetalis, and explain how this condition may develop.
Erythroblastosis fetalis is a condition where an Rh-positive fetus has come into contact
with anti-Rh antibodies through breaks in the placental membrane. This only happens
if the mother has previously had a child that was Rh-positive. The baby's blood may
agglutinate after birth.