Lecture 8 Notes

What are megakaryocytes?

blue/purple -staining outer region; purple granules (large vesicles)

• containing numerous signaling molecules for

  • 1.) activating other platelets

  • 2.) increasing the vascular spasm

  • 3.) promoting formation of the platelet plug

  • 4.) promoting regrowth of blood vessels

  • 5.) attract immune cells to the site of injury

What is Thrombopoietin?

hormone involved with stimulating platelets formation (produced by the liver and kidneys)

• stimulates production and maturation of megakaryocyte

What is the life span of a thrombocyte?

takes a week to make and a week to break

What is the life line of a thrombocyte?

Hemocytoblast → Megakaryoblast → Megaharyocyte → platelets

What is Thrombocyte main function?

form temporary plug that helps seal breaks in blood vessels

What two things keep thrombocytes inactive and mobile?

• nitric oxide

• prostacyclin

  • both of these are released from endothelial cells lining blood vessels

What are the three steps of Hemostasis?

1.) Vascular spasm

2.) platelet plug formation

3.) coagulation from plasma clotting factors

What triggers vascular spasm?

1.) mechanical injury to smooth muscle surrounding blood vessels

2.) chemicals released by endothelial

Capillaries don’t have __ so they can’t do vasoconstriction.

smooth muscle

What sticks platelets together during platelet plug formation?

von Willebrand factor

What four factors cause platelets to activate?

• ADP

• Thromboxana A2

• Serotionin

• Platelet activating factor (PAF)

What does Aspirin do?

inhibits thromboxana A2

What’s the first step in coagulation?

prothrombin activator (FactorX) formed via intrinsic and extrinsic pathways

What is the second step in coagulation?

prothrombin (factor II) converted to enzyme thrombin

What is the third step in coagulation?

thrombin catalyzes fibrinogen (factor I) → fibrin

What is the fourth step for coagulation?

fibrin with Ca²⁺ and factor XIII cause crosslinking of fibrin (the sticky web to the right)

What happens in clot retraction?

actin and myosin contract to draw rupture blood vessel edges together

What two growth factors help in Vessel Repair?

• Platelet-derived growth factor

• Vascular endothelial growth factor

What is Platelet-derived growth factor?

stimulates cell divison of smooth muscle cells and fibroblasts to rebuild blood vessels wall

What is Vascular endothelial growth factor?

stimulates endothelial cells to multiply and restore endothelial lining

What happens in fibrinolysis?

removes unneeded clots after healing

• Plasminogen

• Plasmin

What is Plasminogen?

in clots is converted to plasmin by

• tissue plasminogen activator

What is plasmin?

is a fibrin-digesting enzye

What are the three factors that limit clot growth or formation?

• Dilution

• Inhabitation of thrombin

• Missing Clotting Factors

What inhibition thrombin?

• Anti-thrombin III

• Heparin

• Dabigatran

What is Anti-thrombin III?

inactivates unbound thrombin

What is Heparin?

released by basophils and mast cells inhibits thrombin by enhancing anti-thrombin III

What is Dabigatran?

(drug) directly inhibits thrombin

What is missing clotting factors?

• Hemophiliia A, B, and C

• Vitamin K

What is Hemophilia A, B and C factors?

missing VIII, IX, and XI

What is Vitamin K?

needed to synthesis 4 clotting factors (II, VII, IX, X)

What is Warfarin?

(drug) blocks formation of vitamin K dependent clotting factors

What is Thromboembolic disorder?

undesirable clot formation

What is thrombus?

clot that develops and persists in unbroken blood vessels

What is embolus?

thrombus freely floating in bloodstream

What is Embolism?

embolus obstructing a vessel

What is bleeding disorders?

abnormalities that prevent normal clot formation

What is THrombocytopenia?

dificient number of circulating platelets

What is Petechiae?

appear due to spontaneous widespread hemorrhage

What does liver cause?

Vitamin K deficiency, hepatitis, and cirrhosis