Pathophysiololgy 4.1 The Cardiovascular System: Physiology Review and Functions of Blood

What type of tissue is blood and what is its main function?

Blood is a type of connective tissue that circulates throughout the body, transporting necessary nutrients and waste products to and from body tissues.

What are the two main components of blood?

Blood is composed of plasma (liquid component) and formed elements (erythrocytes, leukocytes, and thrombocytes).

What are the formed elements of blood?

Erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).

What is the average total blood volume in an adult?

5 to 6 liters.

What is plasma and what does it contain?

Plasma is the liquid component of blood that contains mostly water (~90%), proteins (~6–8% including albumin, fibrinogen, and globulins), and other small molecular substances (~2%).

What are the main functions of plasma?

Transport of nutrients, waste products, and hormones; heat distribution; fluid regulation; and acid-base balance.

Where are blood cells synthesized?

In the bone marrow.

Why are not all blood cells considered true cells?

Because some lack a nucleus and organelles.

What is the function of erythrocytes (RBCs)?

They carry oxygen to body tissues and carbon dioxide away from tissues using hemoglobin.

How long do erythrocytes live?

Approximately 120 days.

What is the function of leukocytes (WBCs)?

They function in immunity and the inflammatory response.

What is the function of platelets?

They assist in blood clotting by releasing chemical messengers and adhesion proteins and forming clots at injury sites.

What is hemostasis?

Hemostasis is the stoppage of blood flow.

What are the three stages of hemostasis?

Vascular constriction, formation of the platelet plug, and blood coagulation.

What triggers hemostasis after a blood vessel injury?

Chemical signals are released from the damaged cells.

What happens during vascular constriction?

Damaged blood vessels constrict, decreasing blood flow.

What happens during the formation of the platelet plug?

Platelets arrive at the vessel wall, become activated by cytokines and contact with collagen, become sticky, and attract more platelets to form a plug.

What activates platelets during platelet plug formation?

Cytokines and contact with collagen.

What is required for platelet adhesion?

A protein called von Willebrand factor.

What is the role of von Willebrand factor?

It helps platelet adhesion and carries coagulation factor VIII.

What happens if someone is deficient in platelets or von Willebrand factor?

They cannot effectively form a platelet plug, leading to excessive bleeding.

What are aspirin and clopidogrel (Plavix) classified as?

They are platelet aggregation inhibitors.

What is the purpose of platelet aggregation inhibitors?

To prevent clot formation in people at risk for peripheral artery disease, myocardial infarction, and/or stroke.

What occurs during the third step of hemostasis (blood coagulation)?

Fibrinogen is converted into fibrin.

What is the role of fibrin in blood coagulation?

Fibrin strands form a clot by adhering platelets and other blood components together.

How does the body regulate blood coagulation?

Through pro-coagulation factors that promote clotting and anti-coagulation factors that inhibit clotting.

What are the two coagulation pathways?

Intrinsic and extrinsic pathways.

What is significant about the steps in the coagulation pathways?

Each step perpetuates the next.

What happens if there is an abnormality in any step of the coagulation pathways?

It can lead to problems with clotting.

Where are most coagulation factors produced?

In the liver.

What is vitamin K needed for in coagulation?

It is needed to synthesize factors II, VII, IX, X, prothrombin, and protein C.

What happens with vitamin K deficiency or liver failure?

Abnormal bleeding occurs because prothrombin will not be made.

What role does calcium play in coagulation?

Calcium is needed to carry out most of the coagulation conversions.

What do the intrinsic and extrinsic pathways both produce?

Prothrombin activator.

How does the intrinsic pathway begin and how fast is it?

It begins with factor XII and is slower, taking 1–6 minutes.

How does the extrinsic pathway begin and how fast is it?

It begins with thromboplastin from subendothelial cells and is faster, taking about 15 seconds.

Where do the intrinsic and extrinsic pathways converge?

At activation of factor X.

What happens after factor X is activated?

Prothrombin is converted to thrombin.

What does thrombin do?

It converts fibrinogen into fibrin.

Why is fibrin important?

It stabilizes the clot.

Why are both intrinsic and extrinsic pathways necessary?

Both are required for hemostasis to occur.

What are some natural anticoagulants in the body?

Antithrombin III, protein C, and protein S.

What happens if there is a deficiency of natural anticoagulants?

There is an increased risk of clotting.

What conditions are anticoagulant drugs used to prevent?

Thromboembolic disorders such as deep vein thrombosis (DVT) and pulmonary embolism (PE).

How does warfarin work?

It inhibits vitamin K–dependent clotting factors (II, VII, IX, X).

What monitoring is required for patients on warfarin?

Frequent INR testing.

How does heparin work?

It binds to antithrombin III to inhibit thrombin, factor Xa, and other clotting factors, stopping fibrin formation.

What is an advantage of low molecular weight heparin (Lovenox)?

It requires less frequent administration and monitoring.

What is unique about dabigatran (Pradaxa)?

It is a newer oral anticoagulant that requires less management and is more cost-effective than warfarin.

How do rivaroxaban (Xarelto) and apixaban (Eliquis) work?

They inhibit factor Xa and do not require monitoring