chapter 17 - blood #2

Question 1

What are the three phases of reaction to bleeding?

Answer 1

1. vascular spasm
2. platelet plug formation
3. coagulation (blood clotting)

Question 2

Explain what vascular spasm is.

Answer 2

It is the vasoconstriction of a damaged blood vessel

triggers: direct injury, chemicals released by endothelial cells and platelets, pain reflex in smooth muscle of endothelium

Question 3

Explain the process of platelet plug formation.

Answer 3

at site of injury, platelets:

1. come in contact with exposed collagen fibers
2. become sticky and bind to area
3. degranulate: release chemical messengers
4. chemical messengers begin positive feedback cycle bringing more platelets
5. plug forms in about 1 min

Question 4

What are the three phases of coagulation?

Answer 4

1. formation of prothombin activator
2. prothrombin is converted to thrombin
3. thrombin catalyzes the joining of fibrinogen to form a fibrin mesh

Question 5

explain the two pathways for the formation of prothrombin activator.

Answer 5

intrinsic: in intrinsic, all factors needed are found in the blood.
extrinsic: exposed to an additional factor in tissues underneath the damaged endothelium which bypasses several steps of the intrinsic pathway and is faster

most processes involve both aspects

Question 6

what is factor X and what does it complex with.

Answer 6

Both intrinsic and extrinsic pathways cascade towards factor X.

It then complexes with Ca2+, PF3 and factor V to form prothrombin activator

Question 7

What does the prothrombin activator do?

Answer 7

catalyzes the transformation of prothrombin to thrombin.

Question 8

Explain the process of forming the fibrin mesh.

Answer 8

Thrombin catalyzes the conversion of fibrinogen (soluble protein made by liver and present in blood) to fibrin.

Fibrin strands attach to the platelets forming the structural base of the clot.

Fibrin mesh causes plasma to become gel-like and trap formed elements that try to pass through.

Question 9

What is factor XIII and how is it activated?

Answer 9

activated when thrombin comes in contact with Ca2+

it is an enzyme that cross-links the fibrin strands tightly together strengthening and stabilizing the clot.

Question 10

How long does it take to get to clot formation with each pathway?

Answer 10

intrinsic: 3-6 minutes
extrinsic: can be within 15 secs

Question 11

Explain what happens in clot retraction and repair of tissue.

Answer 11

actin and myosin in platelets contract within 30-60 minutes.

This pulls the fibrin strands squeezing serum from the clot and pulling the wound together.

PGDF (Platelet-derived growth factor) released by platelet granules stimulates rebuilding of wall.

VEGF (Vascular endothelial growth factor) stimulates the regrowth of endothelium lining the vessel.

Question 12

What is serum?

Answer 12

it is what is released when the clot contracts. it is plasma minus the clotting proteins

Question 13

explain fibrinolysis.

Answer 13

Begins within two days and takes several days to complete

Plasminogen in clot is converted to plasmin by plasminogen activator (tPA), factor XII, and thrombin. These activators are secreted by endothelial tissues that detect the presence of the clot.

plasmin is a fibrin digesting enzyme that breaks fibrin into fragments and then amino acids

Question 14

What two homeostatic mechanisms prevent clots from becoming too large?

Answer 14

1. swift removal and dilution of clotting factors

2. inhibition of activated clotting factors: most thrombin is bound to fibrin threads and heparin inactivates thrombin

Question 15

What prevents undesirable clotting?

Answer 15

platelet adhesion is prevented by:

1. smooth endothelial lining of blood vessels
2. antithrombic substances nitric oxide and prostacyclin secreted by endothelial cells

Question 16

what is a thromboembolytic disorder?

Answer 16

it is undesirable clot formation, there are two types

THROMBUS: a clot that develops and persists in an unbroken vessel

EMBOLUS: a freely floating thrombus in the blood stream that can get stuck.

Treatment:
aspirin - prevents platelets from sticking together
heparin - inhibits thrombin formation
warfarin - inhibits clotting

Question 17

What is pulmonary embolism?

Answer 17

when an embolus gets lodged in the lungs

Question 18

What is cerebral embolism?

Answer 18

when an embolus gets lodged in the lungs

Question 19

What is disseminated intravascular coagulation?

Answer 19

a situation in which widespread clotting occurs in intact blood vessels and residual blood becomes unable to clot. blockage of blood flow accompanied by severe bleeding follows.

can occur as a complication of pregnancy, as a result of septicemia, or an incompatible blood transfusion

Question 20

What are the 3 bleeding disorders?

Answer 20

Thrombocytopenia

Impaired liver function

Hemophilias

Question 21

what is thrombocytopenia?

Answer 21

deficient number of circulating platelets

petechiae (small purple spot) appear on the body due to spontaneous widespread hemorrhage

due to suppression or destruction of bone marrow
<50,000 platelets per mm3

treated with transfusion of concentrated platelets

Question 22

Explain liver failure as it relates to bleeding disorders.

Answer 22

inability to synthesize procoagulants

causes include vit K deficiency, hepatitis, and cirrhosis

can also prevent liver from producing bile, impairing fat and vit K absorption

Question 23

Explain what hemophilias are and list the types

Answer 23

hereditary bleeding disorders where the person lacks one of the necessary clotting factors

hemophilia A: (77%) most common, due to deficiency of factor VIII x-linked

hemophilia B: deficiency of factor IX (x-linked)

hemophilia C: mild type, deficiency of factor XI (not x-linked)

SYMPTOMS: prolonged bleeding especially in joint cavities

TREATMENT: plasma transfusions and injections of missing factor

Question 24

What is used to determine blood type?

Answer 24

presence or absence of each antigen/agglutinogen

Question 25

Explain what hemolytic disease of the newborn is.

Answer 25

Rh- mother becomes sensitized when exposure to Rh+ blood causes her to synthesize anti-Rh antibodies

anti-Rh antibodies cross placenta and destroy the RBCs of an Rh+ baby

destruction of the RBCs causes inc bilirubin in the blood which damages the developing nervous system.

TREATMENT: baby pre birth transfusions and exchange transfusions after birth. serum containing anti-Rh can prevent the mother from becoming sensssitized

Question 26

What is bilirubin?

Answer 26

a by-product of RBCs being destroyed

Question 27

What happens in a transfusion reaction?

Answer 27

anti bodies in the recipients blood attacks the RBCs that were transfused into it.

causes agglutination and clogging of small vessels and rupturing of RBC and release of hemoglobin

EFFECTS: diminished oxygen carrying capacity, and hemoglobin in kidney tubules resulting in renal failure

Question 28

What is an agglutinogen and what is another name for it?

Answer 28

they are glycoproteins on the surface of the RBC

also known as antigens

Question 29

What is an agglutinin and what is another name for it

Answer 29

it is the globules in the plasma

also called antibodies

Question 30

What is a hematocrit?

Answer 30

a test that gives % RBC

Question 31

what is a blood chemistry test?

Answer 31

measures various components of the plasma

Question 32

What is a count of formed elements test?

Answer 32

measures the number/volume of rbcs, wbcs, and platelets

Question 33

What is an assessment of hemostasis?

Answer 33

tests clotting time

prothrombin time