- Platelet plugs—rupture of a capillary creates a
rough surface to which platelets stick and form a
barrier over the break. - Chemical clotting involves platelet factors, chemi-
cals from damaged tissue, prothrombin, fibrinogen
and other clotting factors synthesized by the liver,
and calcium ions. See Table 11–3 and Fig. 11–7 for
the three stages of chemical clotting. The clot is
formed of fibrin threads that form a mesh over the
break in the vessel.
6. Clot retraction is the folding of the fibrin threads
to pull the cut edges of the vessel closer together to
facilitate repair. Fibrinolysis is the dissolving of the
clot once it has served its purpose.
7. Abnormal clotting (thrombosis) is prevented by the
very smooth endothelium (simple squamous
epithelium) that lines blood vessels; heparin, which
inhibits the clotting process; and antithrombin
(synthesized by the liver), which inactivates excess
thrombin.
270 Blood
REVIEW QUESTIONS
- Name four different kinds of substances trans-
ported in blood plasma. (p. 252) - Name the precursor cell of all blood cells. Name
the primary hemopoietic tissue and state its loca-
tions. (pp. 254) - State the normal values (CBC) for RBCs,
WBCs, platelets, hemoglobin, and hematocrit.
(p. 262) - State the function of RBCs; include the protein and
mineral needed. (p. 254) - Explain why iron, protein, folic acid, vitamin B 12 ,
and the intrinsic factor are needed for RBC pro-
duction. (pp. 256) - Explain how bilirubin is formed and excreted.
(pp. 258–259) - Explain what will happen if a person with type O
positive blood receives a transfusion of type A neg-
ative blood. (p. 261) - Name the WBC with each of the following func-
tions: (p. 262)
a. Become macrophages and phagocytize dead
tissue
b. Produce antibodies
c. Detoxify foreign proteins
d. Phagocytize pathogens
e. Contain the anticoagulant heparin
f. Recognize antigens as foreign
g. Secrete histamine during inflammation- Explain how and why platelet plugs form in rup-
tured capillaries. (p. 264) - Explain how vascular spasm prevents excessive
blood loss when a large vessel is severed.
(p. 264) - With respect to chemical blood clotting:
(pp. 265–266)
a. Name the mineral necessary
b. Name the organ that produces many of the
clotting factors
c. Name the vitamin necessary for prothrombin
synthesis
d. State what the clot itself is made of - Explain what is meant by clot retraction and fibri-
nolysis. (p. 266) - State two ways abnormal clotting is prevented in
the vascular system. (p. 268) - Explain what is meant by blood viscosity, the fac-
tors that contribute, and why viscosity is impor-
tant. (p. 252) - State the normal pH range of blood. What gas has
an effect on blood pH? (p. 252) - Define anemia, leukocytosis, and thrombocytope-
nia. (pp. 257, 263)