1. Blood #2

2. 14.4: Hemostasis Hemostasis refers to the stoppage of bleeding
Actions that limit or prevent blood loss include:
Blood vessel spasm
Platelet plug formation
Blood coagulation

3. Blood Vessel Spasm Blood vessel spasm
Triggered by pain receptors, platelet release, or serotonin
Smooth muscle in blood vessel contracts

4. Platelet Plug Formation
Triggered by exposure of platelets to collagen
Platelets adhere to rough surface to form a plug
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Endothelial lining
Collagen fiber 1
Break in
vessel wall
Platelet
Red blood cell 2
Blood escaping
through break 3
Platelets adhere to each other , to end of broken vessel, and to exposed collagen 4
Platelet plug helps control blood loss

5. Blood Coagulation Blood coagulation
Triggered by cellular damage and blood contact with foreign surfaces
A blood clot forms
This is a:
Hemostatic mechanism
Causes the formation of a blot clot via a series of reactions which activates the next in a cascade
Occurs extrinsically or intrinsically

7. Extrinsic Clotting Mechanism
Chemical outside of blood vessel triggers blood coagulation
Triggered by tissue thromboplastin (factor III) (not found in blood)
A number of events occur that includes factor VII, factor X, factor V, factor IV, and factor II (prothrombin)
Triggered when blood contacts damaged blood vessel walls or tissues
This is an example of a positive feedback mechanism

8. © SPL/Photo Researchers, Inc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© SPL/Photo Researchers, Inc.

9. Intrinsic Clotting Mechanism
Chemical inside blood triggers blood coagulation
Triggered by Hageman factor XII (found inside blood)
Factor XII activates factor XI which activates IX which joins with factor VIII to activate factor X
Triggered when blood contacts a foreign surface

11. Tissue thromboplastin (Factor lll) Hageman Factor Xll
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Extrinsic Clotting
Mechanism
Intrinsic Clotting
Mechanism
Tissue damage
Blood contacts
foreign surface
Releases
Activates
Tissue thromboplastin
(Factor lll)
Hageman Factor Xll
Activates
(Ca+2)
Activates
Factor Vll
Factor Xl
Activates
(Ca+2)
Activates
Factor X
Factor lX
Activates
Factor Vlll
platelet phospholipids
Factor V
(Ca+2)
Factor X
Activates
(Ca+2)
Activates
Factor V
(Ca+2)
Prothrombin
activator
Converts
Prothrombin
(Factor ll)
Thrombin
(Factor lla)
Converts
Fibrinogen
(Factor l)
Fibrin
Factor Xlll
Stabilizes
Fibrin
clot

12. Fate of Blood Clots
After a blood clot forms it retracts and pulls the edges of a broken blood vessel together while squeezing the fluid serum from the clot
Platelet-derived growth factor stimulates smooth muscle cells and fibroblasts to repair damaged blood vessel walls
Plasmin digests the blood clots
A thrombus is an abnormal blood clot
An embolus is a blood clot moving through the blood vessels

13. © The McGraw-Hill Companies, Inc./Al Telser, photographer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen
Artery wall
Lumen
Plaque
Artery wall
(a)
(b)
© The McGraw-Hill Companies, Inc./Al Telser, photographer

14. Prevention of Coagulation
The smooth lining of blood vessels discourages the accumulation of platelets and clotting factors
As a clot forms fibrin absorbs thrombin and prevents the clotting reaction from spreading
Anti-thrombin inactivates additional thrombin by binding to it and blocking its action on fibrinogen
Some cells such as basophils and mast cells secrete heparin (an anticoagulant)

16. 14.5: Blood Groups and Transfusions
In 1910, identification of the ABO blood antigen gene explained the observed blood type incompatibilities
Today there are 31 different genes known to contribute to the surface features of RBCs determining compatibility between blood types

17. Antigens and Antibodies
Terms to become familiar with:
Agglutination – clumping of red blood cells in response to a reaction between an antibody and an antigen
Antigens – a chemical that stimulates cells to produce antibodies
Antibodies – a protein that reacts against a specific antigen

18. Red blood cell Anti-B antibody Red blood cell Anti-A antibody
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Red blood cell
Anti-B antibody
Red blood cell
Anti-A antibody
Antigen A
Antigen B
Type A blood
Type B blood
Red blood cell
Anti-A antibody
Anti-B antibody
Antigen A
Antigen B
Red blood cell
Type AB blood
Type O blood

19. Agglutinated red blood cells Red blood cell Antigen A Anti-B antibody
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Agglutinated red
blood cells
Red blood cell
Antigen A
Anti-B antibody
Anti-A antibody
(a)
(b)
(c)
(d)
c: © G.W. Willis/Visuals Unlimited; figure d: © George W. Wilder/Visuals Unlimited

20. ABO Blood Group
Based on the presence or absence of two major antigens on red blood cell membranes
Antigen A
Antigen B

22. Rh Blood Group The Rh blood group was named for the rhesus monkey
The group includes several Rh antigens or factors
Rh positive – presence of antigen D or other Rh antigens on the red blood cell membranes
Rh negative – lack of these antigens
The seriousness of the Rh blood group is evident in a fetus that develops the condition erythroblastosis fetalis or hemolytic disease of the newborn

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Rh-negative
woman with
Rh-positive
fetus
Cells from
Rh-positive
fetus enter
woman’s
bloodstream
Woman
becomes
sensitized—
antibodies ( + )
form to fight
Rh-positive
blood cells
In the next
Rh-positive
pregnancy,
maternal
antibodies
attack fetal red
blood cells