Lecture #10 Cardiovascular System: The Blood: Platelets and Clotting

Question 1

What are thrombocytes?

Answer 1

Cell fragments that circulate for 5-9 days, then die.

2/3 of mature platelets circulate, 1/3 reside in the spleen

Question 2

This type of cell refers to clot formation and the clot is called a thrombus also known as?

Answer 2

Throbosis

Question 3

What is it called when there is a circulating clot?

Answer 3

An embolus

Question 4

What is caled when a condition so severe that leads to uncontrollable bleeding?

Answer 4

Hemorrhage

Question 5

What is Thrombocytopoiesis?

Answer 5

Myelooid stem cells produce megakaryocytes with a diameter of ~160um

Question 6

What is Thrombopoietin (TPO)?

Answer 6

Causes fragments to slough off the megakaryocyte

Question 7

How many fragments, or platelets enter the circulation?

Answer 7

2,000-3,000 & the platelet diameter ~2-4um and ~1 um thick.

Question 8

What is hemostasis?

Answer 8

It’s a series of reactions designed to stop bleeding

Question 9

What are the three phases of hemostasis that occur in rapid succession?

Answer 9

First–Vascular spasm i.e., immediate vasoconstriction in response to injury

Second–platelet plug formation

Third–coagulation (blood clotting)

Question 10

What is phase 1 of vascular spasm?

Answer 10

Only occurs in blood vessels that have a smooth muscle—spasm reduces vessel diameter which results in pressing of endothelial surfaces together.

Question 11

Does phase 1 of the vascular stop blood flow or continue blood flow?

Answer 11

Stops blood flow almost instantly.

Question 12

Where does phase 1 take place?

Answer 12

Effective only in very small vessels (meta) arterioles, precapillary sphnicters

Question 13

What is the function of phase 2 platelet plug formation?

Answer 13

Platelets normally do not stick to each other or to the endothelial lining of blood vessels

Question 14

What happens to platelets when their is damage to the blood vessels?

Answer 14

In order for the platelets to stick, they become exposed to collagen fibers and they become activated, which is allowing them to stick to one another.

Question 15

After the platelets are exposed to collagen fiber what transformation happens to the activated platelets?

Answer 15

Platelets liberate thromboxane A2, serotonin, and ADP which attract & activate still more platelets

Question 16

What are the functions of ADP, Thromboxane A2, and serotonin?

Answer 16

ADP makes platelets stick, while thromoboxane A2 and serotonin cause vasoconstriction. Which results in a formation of platelet plug.

Question 17

What happens in Phase 3 Coagulation?

Answer 17

It is a complex process, where it involves 13 clotting factors which is a set of reactions in which blood is transformed from a liquid to a gel.

Question 18

Does phase 3 coagulation involve intrinsic, extrinsic pathways, or both?

Answer 18

Both pathways are activated–the activation of the intrinsic pathway takes more time than for the extrinsic pathway

Question 19

What are the final steps that constitute the common pathway which must be completed for effective clotting?

Answer 19

Once Prothrombinase is formed it is converted to thrombin.

Question 20

What are the two main functions of thrombin?

Answer 20

Converts fibrogen (soluble) into a fibrin (insoluble stable threads) mesh

Activates factor XIII which stabilizes the fibrin network

Question 21

During the formation of clotting factors, Prothrombin, fibrinogen, and factors ________are synthesized in the liver.

Answer 21

Factors V, VII, IX, and X

Question 22

What is the purpose of Vitamin K?

Answer 22

Vitamin K is needed for the synthesis of factors II,VII,IX, and X—deficiency of K can lead to failure of blood clotting.

Question 23

If an individual is lacking factor VIII they are?

Answer 23

Hemophiliacs

Question 24

Why must clots be dissolved?

Answer 24

So that they do enter the circulation as an embolus (a blood clot transported by the bloodstream)

Question 25

A dissolution of a clot is known as?

Answer 25

Fibrinolysis

Question 26

When a clot is formed, an inactive plasma enzyme called _______ is incorporated onto the clot.

Answer 26

Plasminogen

Question 27

Both body tissues and blood contain substances that can activate plasminogen to ______ or fibrinolysin, an active plasma enzyme.

Answer 27

Plasmin

Question 28

Among these substances are ____activated factor XII, and _______ activator, which is synthesized in endothelial cells of most tissues and liberated into the blood.

Answer 28

Thrombin, Tissue Plasminogen

Question 29

Once _____ is formed, it can dissolve the clot by digesting fibrin threads and inactivating substances such as fibrinogen, prothrombin, and factors V and XII.

Answer 29

Plasmin