#04: Blood II Continued/Heart I

Question 1

Coagulation: Intrinsic and Extrinsic Pathways

Answer 1

• Two separate pathways exist for the third step of clotting, coagulation. They both eventually lead to activation of prothrombinase. The intrinsic and extrinsic pathways.
○ The extrinsic pathway rapidly responds to form a clot, but the clot is not as strong as that formed by the intrinsic pathway.
○ The intrinsic pathway is slower to develop but has positive feedback components that result in a much larger and stronger clot.
○ In both intrinsic and extrinsic pathways, factors are activated by the cleavage of peptide sequences by protease activity in many of the blood clotting factors. The activated factors in many cases also have protease activity.

Question 2

Intrinsic Pathway

Answer 2

• The Intrinsic Pathway has several characteristics.
○ The pathway behaves like dominoes, when the 1st step is activated, it triggers activation of 2nd step, which triggers 3rd step, and so on.
○ Has several positive feedback loops that increase the changes.
○ Many steps involve the conversion of an inactive factor to an active state by the removal of a peptide fragment.

Question 3

Extrinsic Pathway

Answer 3

• The Extrinsic Pathway begins with vascular damage with subendothelial cells exposed to blood. Damaged tissues release a mix of lipoproteins and phospholipids called thromboplastin (or tissue factor of factor III).

Question 4

Intrinsic & Extrinsic Pathway Respond To…

Answer 4

• Intrinsic pathway relies on circulating clotting factors, while extrinsic pathway responds immediately to damaged vessels.

Question 5

What Both Intrinsic and Extrinsic Pathway Ultimately Lead To

Answer 5

• Both pathways lead to activation of prothrombinase, which converts prothrombin to thrombin. Activated thrombin cleaves fibrinogen to generate fibrin molecules that lack the negatively charged amino acids, making fibrin much less water-soluble. Fibrin spontaneously aggregates in a regular array, forming a fibrin clot.

Question 6

Vitamin K Source

Answer 6

• We get vitamin K from bacteria which powers the clotting process. So if we take antibiotics, we may kill these bacteria, which weakens clotting process.

Question 7

Collagen

Answer 7

• Collagen is factor associated with intrinsic pathway, which is activated when exposed to plasma clotting factors that appear due to injury. Tissue factor is associated with extrinsic pathway, which is directly activated by damage to tissue.

Question 8

Plasmin

Answer 8

• Degradation of fibrin clots is the function of plasmin (protease that circulates as the inactive proenzyme plasminogen). Plasminogen binds to both fibrinogen and fibrin, becoming incorporated into the clot as it’s formed. Tissue plasminogen activator (tPA) converts plasminogen to plasmin. Its inactive form is released from vascular endothelial cells. After injury, it binds to fibrin and is activated. It then cleaves plasminogen to plasmin, which then digests the fibrin clot into soluble degradation products.

Question 9

Hemophilia

Answer 9

• Hemophilia caused by deficiency in any clotting factor. Many clotting disorders are X-linked, so men tend to be more susceptible to them. Women more likely to be carriers. Minor injuries may produce hemorrhage.
○ Treatment involves supplying missing clotting factor. Usually done by transfusing blood with the factor.

Question 10

Thrombus

Answer 10

• A thrombus is a blood clot formed inside blood vessels or the heart. A thrombus that breaks loose and floats through the circulation is known as an embolus. Both a thrombus and embolus can cause death if they block a blood vessel to an essential organ.

Question 11

Deep Vein Thrombosis

Answer 11

• Deep Vein Thrombosis (Economy Class Syndrome) is when you develop a thrombus in vascular structure of body. When you remain inactive for a long period of time, blood flow slows down and not being pumped, which is promoting clot formation, mainly in legs. When you suddenly put a ton of activity on your body, clot can break free and cause an embolus.
○ Major factors contributing to clot formation are blood flow rate, quality of vessel wall, and blood viscosity.
○ Treat with anticoagulants (heparin, coumadin) or compression stockings.

Question 12

Heart Fluid Flow

Answer 12

• General direction fluid flows is from area of high pressure to low pressure. To supply this pressure, we have a pump to pump blood throughout the body.
○ In body, it is key to have blood stay in one direction, which is why values are used to prevent that.

Question 13

Heart Is A Double Pump

Answer 13

• The Heart is a double pump. Contains arteries which carry blood away from the heart, and veins, which carry blood back to the heart. Arteries carry blood high in oxygen, except pulmonary arteries. Veins carry blood low in oxygen, except pulmonary veins.

Question 14

Heart Unidirecctional Flow

Answer 14

• Heart’s anatomy ensures unidirectional flow of blood though it. Backflow of blood is prevented by valves.

Question 15

Heart Side-by-Side Pumps

Answer 15

• Heart acts like 2 side-by-side pumps that work at same rate and pump same volume of blood; one directs blood to lungs for gas exchange, other directs blood to body tissues for nutrient and respiratory gas delivery.

Question 16

Heart Base

Answer 16

• The posterosuperior surface of the heart, formed primarily by the left atrium, is called the base. The pulmonary veins that enter the left atrium border this base.

Question 17

Heart Apex

Answer 17

• The inferior, conical end of the heart is called the apex, where electrical conduction occurs.

Question 18

Pericardium

Answer 18

• Heart is contained within the pericardium, a fibrous sac and serous lining. It restricts heart’s movement so it doesn’t bound and move about in the thoracic cavity, and prevents heart from overfilling with blood.
○ Outer portion is tough, dense connective tissue layer called fibrous pericardium.
○ Inner portion is a thin double-layered serous membrane called the serous pericardium. (Parietal touches fibrous, visceral lines heart).
§ Thin space between parietal and visceral layers is pericardial cavity, into which serous fluid is secreted to lubricate the serous membranes and facilitate almost frictionless movement of heart.

Question 19

Periardial Effusion

Answer 19

• Pericardial effusion is where there’s too much periccardial fluid trapped inside pericardium. Can form a disorder called cardiac tamponade, which is having enough fluid to damage the heart. Too much fluid begins to push on the heart which weakens contraction.
○ Pericardiocentesis is process of manually removing pericardial fluid.

Question 20

Epicardium

Answer 20

• Epicardium is the outermost heart layer and is also known as the visceral layer of the serous pericardium. It’s composed of a serous membrane and areolar connective tissue.

Question 21

Myocardium

Answer 21

• Myocardium is middle layer of heart and is composed of cardiac muscle tissue. It’s thickest of three heart wall layers. It’s where heart attacks occur. Its arrangement of cardiac muscle permits compression necessary to pump large volumes of blood out of the heart.

Question 22

Endocardium

Answer 22

• The internal surface of the heart and the external surfaces of the heart valves are covered by endocardium. It’s composed of a simple squamous epithelium (endothelium) and a layer of areolar connective tissue.