Blood Loss

Question 1

What is Hemostasis?

Answer 1

• A sequence of responses that stop bleeding when blood vessels are injured
• Response must be quick, localized, and carefully controlled

Question 2

What are the three mechanisms that can reduce loss of blood from cells?

Answer 2

• Vascular spasm
• Platelet plug formation
• Blood clotting (coagulation)

Question 3

Where can/cannot hemostasis prevent hemorrhage?

Answer 3

• Can: smaller blood vessels

- Cannot: larger vessels

Question 4

What is vascular spasm?

Answer 4

• When vessel is damaged, the smooth muscle in its wall contracts immediately

Question 5

How long does vascular spasm last?

Answer 5

• Several minutes to several hours

Question 6

What is platelet plug formation?

Answer 6

When platelets come into contact with damaged vessels, they change characteristics and form a plug to fill the gap in the injured vessel.

Question 7

What are the steps to platelet plug formation?

Answer 7

• Platelets contact and stick to injured blood vessel
• Platelets interact with each other and begin to release chemicals
• Chemicals activate near platelets and sustains vascular spasm
• Chemical release causes stickiness which brings multiple platelets together
• Large number of platelets forms plug

Question 8

What is blood clotting (coagulation)?

Answer 8

Blood thickens and forms a gel that eventually separates from liquid.

• Gel is the clot
• Consists of network of fibrin

Question 9

What is fibrin?

Answer 9

Insoluble protein fibers

Question 10

What is the process of coagulation?

Answer 10

• Series of chemical reactions that culminates in formation of fibrin threads
• Too easy to form clot, thrombosis forms
• To long to form, hemorrhage results

Question 11

What are the clotting factors?

Answer 11

• Calcium ions (CA2+)
• Several enzymes made by liver cells and released into blood
• Various molecules associated with platelets and released by damaged tissue

Question 12

How are clotting factors identified?

Answer 12

Roman numerals

Question 13

What are the 3 steps to clotting?

Answer 13

Step 1: Prothrombinase is formed
Step 2: Prothrombinase converts prothrombin into the enzyme thrombin
Step 3: Thrombin converts soluble fibrin into insoluble fibrin

Question 14

What is Prothrombin and where is it created?

Answer 14

Plasma protein formed in the liver with the help of Vitamin K

Question 15

What forms the threads of the clot?

Answer 15

Fibrin

Question 16

What contains substances that interfere with fibrin and clot formation?

Answer 16

Cigarette smoke

Question 17

What is clot retraction?

Answer 17

Consolidation or tightening of the fibrin clot

Question 18

What is the purpose of clot retraction?

Answer 18

Pulls the edges of injured vessels walls closer together, decreasing risk of further injury

Question 19

What do fibroblasts form?

Answer 19

Connective tissue in the ruptured area

- new endothelial cells repair the vessel lining

Question 20

What occurs simultaneously with coagulation?

Answer 20

Fibrinolysis

Question 21

What is fibrinolysis?

Answer 21

Enzymatic breakdown of fibrin within clots

Question 22

How can endothelial surfaces of blood vessels be roughened?

Answer 22

• Atherosclerosis
• Trauma
• Infection

Question 23

What is clotting in an unbroken blood vessel? The clot itself?

Answer 23

Thrombosis; Thrombi

Question 24

What are the two ways clots can form in unbroken blood vessels?

Answer 24

• Blood vessel surfaces may be roughened

- When blood flows too slowly

Question 25

Can a thrombosis dissolve spontaneously?

Answer 25

Yes

Question 26

What is an emobolus?

Answer 26

A blood clot, bubble of air, fat from broken bones, or pieces of debris transported by the bloodstream

Question 27

Where do emboli usually form?

Answer 27

Veins (blood moves slower)

- Most common site for it to lodge is lungs (Pulmonary embolism)

Question 28

Massive emboli in the lungs results in what?

Answer 28

Right ventricular failure; death can occur in a few minutes to hours

Question 29

What can an embolism cause if it blocks blood flow to brain, kidney, or heart?

Answer 29

• Stroke
• Kidney failure
• Heart attack