Platelets (Thrombocytes)

Question 1

• Count: 150,000 - 400,000 per microliter of blood.
• Structure: Anucleated, membrane-bound cell fragments.
• Shed from the surface of megakaryocytes in the red bone marrow.
• Characteristics:
  ➢ Typically biconvex and discoidal in shape, measuring approximately 2 to 4 µm in diameter.
  ➢ Smallest of the formed elements and often appear in clumps.
• Function: Plays a crucial role in blood clotting by aggregating at sites of vascular injury to prevent bleeding.

Answer 1

Platelets (Thrombocytes)

Question 2

• They prevent loss of blood by clotting.
• Platelets also have an incompletely understood role in maintaining the integrity of the endothelial lining.
• Platelets react to abnormal surfaces such as might be encountered in a bleeding wound. Such platelets are activated. Mass of platelets increases called thrombus.
• They release factors that participate in the clotting cascade and in fibrin formation.

Answer 2

Roles of Platelets in Hemostasis

Question 3

• Platelet adhesion occurs when von Willebrand factor connects collagen and platelets.
• The platelet release reaction is the release of ADP, thromboxanes, and other chemicals that activate other platelets.
• Platelet aggregation occurs when fibrinogen receptors on activated platelets bind to fibrinogen, connecting the platelets to one another. A platelets plug is formed by the accumulating mass o platelets.

Answer 3

Example for an injured blood vessel:

Question 4

• Stage 1: inactive clothing factors are activated by exposure to connective tissue or by chemicals released from tissues.
• Stage 1: through a series of reactions, the activated clothing factors form prothrombinase.
• Stage 2: prothrombin is converted to thrombin by prothrombinase.
• Stage 3: Fibrinogen is converted to fibrin (the clot) by thrombin.

❖ Thrombin and tissue plasminogen activator convert inactive
plasminogen into plasmin.
❖ Plasmin breaks down the fibrin in a blood clot, resulting in clot
fibrinolysis.

Answer 4

Steps in the formation of fibrin:

Question 5

Blood Types

Answer 5

• Type A
• Type B
• Type AB
• Type O

Question 6

➢ Red blood cells with type A surface antigens and plasma with anti-B antibodies

Answer 6

Type A

Question 7

➢ Red blood cells with type B surface antigens and plasma with anti-A antibodies

Answer 7

Type B

Question 8

➢ Red blood cells with both type A and type B surface antigens, and neither anti- A nor anti- B plasma antibodies.
➢ Universal recipient

Answer 8

Type AB

Question 9

➢ Red blood cells with neither type A nor type B surface antigens, but both anti-A and anti- B plasma antibodies.
➢ Universal donor

Answer 9

Type O

Question 10

➢ does not cause an agglutination reaction because the anti-B antibodies in the recipient do not combine with the type A antigens on the red blood cells in the donated blood.

Answer 10

Blood type A donated to type A

Question 11

➢ causes an agglutination reaction because the anti-A antibodies in the recipient combine with the type A antigens on the red blood cells in the donated blood.

Answer 11

Blood type A donated to a type B

Question 12

➢ Discovered in rhesus monkey

Answer 12

Antigen D (Rh positive)

Question 13

If the Father is Rh positive and Mother Rh negative, and they will produce baby which is Rh positive:
* Before or during delivery, Rh-positive red blood cells from the fetus enter the blood of a Rh-negative woman through a tear in the placenta.
* The mother is sensitized to the Rh antigen and produces anti-Rh antibodies because this usually happens after delivery. There is no
effect on the fetus in the first pregnancy.
* During a subsequent pregnancy with a Rh- positive fetus, Rh-positive red blood cells cross the placenta, enter the maternal circulation, and stimulate the mother to produce antibodies against the Rh antigen. Antibody production is rapid because the mother has been sensitized to the Rh antigen.
* The anti- Rh antibodies from the mother cross the placenta, causing agglutination and hemolysis of fetal red blood cells, and hemolytic disease of the newborn (HDN) develops.

Answer 13

If the Father is Rh positive and Mother Rh negative, and they will produce baby which is Rh positive:
* Before or during delivery, Rh-positive red blood cells from the fetus enter the blood of a Rh-negative woman through a tear in the placenta.
* The mother is sensitized to the Rh antigen and produces anti-Rh antibodies because this usually happens after delivery. There is no
effect on the fetus in the first pregnancy.
* During a subsequent pregnancy with a Rh- positive fetus, Rh-positive red blood cells cross the placenta, enter the maternal circulation, and stimulate the mother to produce antibodies against the Rh antigen. Antibody production is rapid because the mother has been sensitized to the Rh antigen.
* The anti- Rh antibodies from the mother cross the placenta, causing agglutination and hemolysis of fetal red blood cells, and hemolytic disease of the newborn (HDN) develops.

Question 14

NEVER BACK DOWN NEVER WHAT/!!!!!!!!!!!!!!!!??????????????

Answer 14

NEVER GIVE UPPPPP!!!!!!!!!!!!!!!!!!!!!!!!!!!!