Unit 3 - Blood PART E

Question 1

Hemostasis

Answer 1

Process of preventing blood loss (opposite of hemostasis is hemorrhage).

Question 2

What are the 4 main steps of Hemostasis?

Answer 2

1. Vasconstriction (vascular spasm)
2. Platelet plug formation
3. Coagulation (clot formation)
4. Fibrinolysis (Clot dissolution)

Question 3

1. Vasconstriction (vascular spasm)

Answer 3

a. Damage to blood vessel wall activates local pain receptors. Which triggers an increase in SYMPATHETIC ACTIVITY causing vasoconstriction that reduces blood flow to the site of damage.

b. Platelets stick to exposed collagen fibers and release platelet factors (factors = ions/molecules/cytokines), some of which reinforce vasoconstriction including:
i. Serotonin
ii. Thromboxane A2

Question 4

Platelets stick to exposed collagen fibers and release platelet factors (factors = ions/molecules/cytokines), some of which reinforce vasoconstriction including:

Answer 4

i. Serotonin (from secretory vesicles of platelets)
ii. Thromboxane A2 (from platelet membrane)

• also contribute to platelet aggregation (along with ADP & PAF)
• net result is a growing platelet plug that seals the damaged vessel wall

Question 5

2. Platelet Plug Formation

Answer 5

a. Platelet adhesion

b. Factors involved in platelet aggregation include:
i. Platelet Activating Factor (PAF).
ii. Serotonin
iii. Adenosine diphosphate(ADP)
iv. Thromboxane A2

c. Platelet plug formation cannot spread beyond the site of injury due to secretion of PROSTACYCLIN and NITRIC OXIDE (NO) from surrounding endothelial cells which blocks adhesion and aggregation.

Question 6

Platelet adhesion

Answer 6

platelets stick to exposed collagen and release factors that attract other platelets to the site (POSITIVE FEEDBACK) that fill in damaged area forming a platelet plug.

Question 7

Factors involved in platelet aggregation include:

Answer 7

i. PLATELET ACTIVATING FACTOR (PAF).
ii. SEROTONIN (from secretory vesicles of platelets)
iii. ADENOSINE DIPHOSPHATE (ADP) (from platelet mitochondria)
iv. THROMBOXANE A2 (from platelet phospholipids)

ii & iv are VASOCONSTRICTORS

Question 8

Serotonin & Thromboxane A2 are…

Answer 8

VASOCONSTRICTORS

Question 9

Platelet plug formation CANNOT spread beyond the site of injury due to what?

Answer 9

secretion of PROSTACYCLIN and NITRIC OXIDE (NO) from surrounding endothelial cells which blocks adhesion and aggregation.

Question 10

Coagulation

Answer 10

complex process in which fluid blood forms a gelatinous clot

Question 11

3. Coagulation (Clot Formation)

Answer 11

a. Cascade/Network of factor interactions activated through two pathways almost simultaneously:
i. intrinsic Pathway (Contact Activation Pathway)
ii. Extrinsic Pathway (Cell Injury/Tissue Factor Pathway)

b. Each pathway results in activation of Factor X, whose
formation is the start of the common pathway.

c. Factor X combines with Ca2+, Factor V, and phospholipids to form PROTHROMBIN ACTIVATOR.
- Active factor X exerts positive feedback on the extrinsic pathway (activating more Factor VII and Tissue Factor III).

d. Prothrombin activator converts Prothrombin (a plasma protein) into Thrombin.

d. Thrombin acts on Fibrinogen (soluble clotting protein in plasma) to produce insoluble Fibrin polymers. These form a web of thread-like protein that covers the platelet plug and traps formed elements (RBCs).
- Thrombin exerts positive feedback on intrinsic pathway (activates more Factor XI = plasma thromboplastin)

e. ActiveFactorXIII(FibrinStabilizingFactor) converts fibrin into a cross-linked polymer, and stabilizes the clot.

Question 12

Cascade/Network of factor interactions activated through two pathways almost simultaneously: (eventually merge into 1)

Answer 12

i. Intrinsic Pathway (Contact Activation Pathway)
- Initiated by factors in blood exposed to collagen (tissue factor XII)

ii. Extrinsic Pathway (Cell Injury/Tissue Factor Pathway)
- Initiated by factors in surrounding damaged tissues (Tissue Factor III = Tissue thromboplastin)

Question 13

Intrinsic Pathway (Contact Activation Pathway)

Answer 13

Initiated by factors in blood exposed to collagen (tissue factor XII)

Question 14

Extrinsic Pathway (Cell Injury/Tissue Factor Pathway)

Answer 14

Initiated by factors in surrounding damaged tissues (Tissue Factor III = Tissue thromboplastin)

Question 15

Prothrombin activator converts Prothrombin (a plasma protein) into _____.

Answer 15

Thrombin

• the enzyme that converts FIBRINOGEN into insoluble FIBRIN polymers
• these fibrin fibers become part of the clot

Question 16

Thrombin acts on ______ (soluble clotting protein in plasma) to produce insoluble Fibrin polymers. These form a web of thread-like protein that covers the platelet plug and traps formed elements (RBCs).

Answer 16

FIBRINOGEN

Question 17

What is something to note about Coagulation (Clot Formation)?

Answer 17

~ 2 dozen factors involved. These are obtained from the diet, liver (plasma proteins) damaged tissue and platelets.

Vitamin K is required for synthesis of 4 of the factors (II, VII, IX, X) ,

Question 18

4. Fibrinolysis (Clot Dissolution)

Answer 18

After blood vessel wall is repaired, clot is broken up by fibrin digesting enzyme called PLASMIN.
- First, thrombin and TISSUE PLASMINOGEN ACTIVATOR (tPA) convert PLASMINOGEN in the clot into plasmin.

• Plasmin breaks up clot (fibrin) (= FIBRINOLYSIS).
• Phagocytes then remove the clot in clumps.

Question 19

Plasminogen

Answer 19

an inactive form of plasmin

- part of the clot

Question 20

Anticoagulants

Answer 20

Produced by the body prevent spread of clot.

Block parts of coagulation cascade. (AKA prevent coagulation from taking place)

Question 21

What are the 2 mechanisms that limit the extent of blood clotting within a vessel:

Answer 21

(1) inhibition of platelet adhersion &

(2) inhibitation of the coagulation cascade & fibrin production

Question 22

Most anticoagulants act by…

Answer 22

blocking 1 or more of the rxns in the coagulation cascade

Question 23

Which anticoagulants does the body produce:

Answer 23

1. Heparin
2. Antithrombin III
3. Protein C

Question 24

The body produces these 2 anticoagulants:

1. Heparin
2. Antithrombin III

Answer 24

INHIBIT ACTIVE FACTORS IX, X, XI & XII

- work together

Question 25

The body produces this anticoagulant:

3. Protein C

Answer 25

INHIBITS ACTIVE FACTORS V & VIII

Question 26

Application of hemostasis and blood clotting (3 ex’s):

Answer 26

E.g.1. Thrombus = stationary clot in an undamaged vessel
(increases resistance to blood flow)

E.g2. Embolus = free floating clot

• can cause blockage of small vessels of the lungs (pulmonary embolism) or brain (cerebral embolism =
  stroke) or heart (coronary embolism – leads to myocardial infarction)..

E.g.3: Hemophilia

• Clotting is abnormal or absent
• Majority of people with hemophilia are lacking clotting factor VIII (also known as Antihemophilic Factor)

Question 27

Application of hemostasis and blood clotting: Thrombus

Answer 27

THROMBUS = stationary clot in an undamaged vessel

(increases resistance to blood flow) & stop BF

Question 28

Application of hemostasis and blood clotting: Embolus

Answer 28

EMBOLUS = free floating clot

• can cause blockage of small vessels of the lungs (pulmonary embolism) or brain (cerebral embolism =
  stroke) or heart (coronary embolism – leads to myocardial infarction).. (AKA heart attacks, occur when a coronary blood vessel is blocked by a blood clot)

Question 29

Application of hemostasis and blood clotting: Hemophilia

Answer 29

• Clotting is abnormal or absent
• Majority of people with hemophilia are lacking clotting factor VIII (also known as Antihemophilic Factor)

(best-known coagulation disorder)

Question 30

Hemophilia

Answer 30

a name given to several diseases in which 1 of the factors in the coagulation cascade is either DEFECTIVE or LACKING