Hemostasis & Fetal Circulation Flashcards
Endothelial factors:
Smoothness of endothelial lining prevents platelet adhesion
(-) charged particles present over endothelial lining repel the clotting factors
Hemostasis
Prevention of blood loss
4 main steps:
Vascular constriction/spasm
Formation of platelet plug
Blood coagulation
Fibrinolysis
Vascular constriction/spasm
Reduces flow of blood from injured vessel
After blood vessel has been damaged, the vessel wall causes the smooth muscle in the wall to contract
Functional characteristics of platelets
Cell membrane contains:
Glycoprotein (receptors) cause adherence to injured endothelial cells and exposed collagen
Phospholipids, that play an important role in blood clotting
Their cytoplasm contains:
Contractile proteins
Dense granules
Alpha-granules
Can store large quantities of Ca++
Mechanism of the platelet plug
Platelets immediately change their own characteristics drastically
They begin to swell
They assume irregular forms with numerous irradiating pseudopods from the surface
Contractile proteins contract forcefully and release the granules (contain multiple active factors)
Become sticky to collagen in the tissue and to a protein von Willebrand factor
Blood coagulation
Formation of blood clot
Stages of blood clotting:
Intrinsic pathway
Activated when there is a blood trauma
Activated through exposed endothelial collagen
Is slow and takes about 1-6 minutes to form a clot
Extrinsic pathway
Activated when the traumatized vascular wall comes into contact with the blood
Activated through tissue factor released by endothelial cells after external change
Is quick and takes 15 seconds after the tissue factor is released
Umbilical cord:
2 umbilical arteries: return deoxygenated blood, fecal waste, CO2 to placenta
1 umbilical vein: brings oxygenated blood and nutrients to the fetus
Ductus Venosus
carry oxygenated blood from umbilical vein to inferior vena cave, bypassing fetal liver
Ductus arteriosus
carry oxygenated blood from pulmonary artery to aorta, bypassing fetal lungs
The final common pathway of coagulation involves:
The degradation of a transglutaminase (factor XIII)
Formation of the prothrombinase complex
Formation of prothrombin
Formation of fibrinogen
Formation of the prothrombinase complex
What is the order of clotting?
Fibrin, fibrinogen, thrombin, prothrombin, thromboplastin
Prothrombin, thromboplastin, thrombin, fibrin, fibrinogen
Thromboplastin, thrombin, prothrombin, fibrin, fibrinogen
Thromboplastin, prothrombin, thrombin, fibrinogen, fibrin
Thromboplastin, prothrombin, thrombin, fibrinogen, fibrin
Which of the following statements about the platelet phase of hemostasis is TRUE?
Platelets secret factors that promote primary hemostasis
Most clotting factors circulate as inactive precursor
Platelets can adhere to collagen via the vonWillebrand factor
ADP, thrombin, and thromboxane A2 can cause platelets to aggregate
All the above
all the above
Which vessels transport blood rich oxygen and nutrients to the fetus?
Ductus venosus
Umbilical vein
Umbilical artery
Ductus arteriosus
umbilical vein
