Hemostasis and Platelets Quiz

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Questions and Answers

What is the minimum time interval required between two blood donations?

3 days

3 months (correct)

3 weeks

3 years

Which scenario represents an incompatible blood transfusion?

Donor is blood group O and recipient is blood group AB

Donor is blood group B and recipient is blood group B

Donor is blood group AB and recipient is blood group A (correct)

Donor is blood group A and recipient is blood group A

Which statement is true regarding thrombasthenic purpura?

It is caused by decreased platelet count (correct)

It is characterized by excessive platelet count

Bleeding time is usually shortened

It does not affect clotting mechanisms

In the context of hemophilia A, which statement is accurate?

It occurs due to deficiency in clotting factor VIII Signup and view all the answers

What is a true statement regarding blood group AB?

AB is a universal blood recipient Signup and view all the answers

What characterizes thrombocytopenic purpura?

Decreased platelet count Signup and view all the answers

What is the definition of bleeding time?

Time taken from pin pricking until bleeding stops Signup and view all the answers

Which mechanism is part of hemostasis?

Vasoconstriction Signup and view all the answers

Which of the following factors prevents blood clot formation?

Anticoagulants Signup and view all the answers

What does the intrinsic mechanism of blood coagulation depend on?

Blood components only Signup and view all the answers

How does vitamin C deficiency relate to purpura?

It causes a defect in blood vessel walls. Signup and view all the answers

Which blood type is considered a universal donor?

Group O Signup and view all the answers

What role do clotting factors play in the blood coagulation process?

They are involved in blood clot formation. Signup and view all the answers

What is the typical range for the duration of the extrinsic coagulation mechanism?

20-40 seconds Signup and view all the answers

What is a main complication of incompatible blood transfusion?

Infection Signup and view all the answers

Which blood type does not contain anti-A or anti-B antibodies?

Group AB Signup and view all the answers

What is the normal platelet count range?

300000/mm3 Signup and view all the answers

In which situation is a blood transfusion indicated?

With marked decrease in platelet count Signup and view all the answers

What percentage of the population represents Rh positive people?

85% Signup and view all the answers

Massive compatible blood transfusion can cause which of the following?

Hypocalcemia Signup and view all the answers

Which condition signifies purpura?

Presence of red or purple marks on the skin Signup and view all the answers

What is the consequence of transfusing incompatible blood groups?

Acute renal failure Signup and view all the answers

Which blood group has surface antigen 'B' and antibodies 'Anti-A'?

Blood group B Signup and view all the answers

Which blood group is known as the universal donor?

Blood group O Signup and view all the answers

Purpura is primarily caused by a deficiency in which type of blood component?

Platelets Signup and view all the answers

What is the normal range for bleeding time?

15 seconds Signup and view all the answers

What characteristic feature defines thrombocytes?

They are formed by megakaryocytes Signup and view all the answers

Which condition can lead to erythroblastosis fetalis?

Mother Rh -ve, father Rh +ve, baby Rh +ve Signup and view all the answers

Most clotting factors are synthesized from which plasma protein?

Beta globulin Signup and view all the answers

What is the primary purpose of administering anti-D antibodies to a Rh-negative mother after the delivery of an Rh-positive fetus?

To neutralize the D-antigen present in fetal red blood cells Signup and view all the answers

Why is the first fetus usually not affected by Rh incompatibility in an Rh-negative mother with a Rh-positive partner?

No Rh-positive fetal blood enters the mother's circulation during the first delivery Signup and view all the answers

What complication can arise in subsequent pregnancies after a Rh-negative mother has delivered a Rh-positive baby?

Possible brain damage due to high bilirubin levels in the infant Signup and view all the answers

Which fetal condition is primarily caused by the mother's anti-D antibodies in subsequent pregnancies?

Hemolytic disease leading to fetal anemia Signup and view all the answers

Which of the following statements is true regarding blood transfusions?

Even compatible transfusions can lead to complications such as massive transfusion syndromes Signup and view all the answers

How does sensitization occur in a Rh-negative mother during her first childbirth when delivering a Rh-positive fetus?

Resulting from Rh-positive fetal RBCs entering the mother's bloodstream during delivery Signup and view all the answers

What condition may arise if a Rh-positive fetus experiences extreme agglutination of red blood cells?

Kernicterus due to excessive mother-to-fetus bilirubin transfer Signup and view all the answers

What is the primary role of IgG antibodies in the context of Rh incompatibility during pregnancy?

To cross the placenta and target Rh-positive fetal red blood cells Signup and view all the answers

Study Notes

Platelets

Normal platelet count: 300,000/mm3
Platelet lifespan: 10 days
Platelet formation: megakaryocytes in bone marrow
Platelet function: important in hemostasis and clot formation
Platelets help heal injured vessel walls
Platelets are responsible for platelet plug formation

Purpura

Characterized by small (petechiae) or large (ecchymosis) hemorrhages under the skin
Purpura is caused by:
- Reduced platelet count (thrombocytopenic purpura): usually caused bone marrow lesions
- Vitamin C deficiency
- Defect in platelet function (thrombasthenic purpura): caused by prolonged bleeding time
The bleeding time test measures the duration it takes for bleeding to stop after a pin prick

Hemostasis

The process of stopping bleeding from small vascular injuries
Requires a series of steps:
- Vasoconstriction
- Platelet reaction (platelet plug formation)
- Coagulation mechanism

Blood Clotting

Also known as blood coagulation
Process involves formation of a fibrin network that traps blood cells
Intrinsic mechanism:
- Initiated from within blood itself
- Requires 4-8 minutes
Extrinsic mechanism:
- Initiated from outside blood
- Uses tissue factor
- Takes 20-40 seconds

Clotting Factors

Plasma proteins, primarily beta-globulins
Most are formed by the liver
Act as proteolytic enzymes
Present in blood in inactive forms

Anticoagulants

Factors that prevent blood clots
Examples include heparin, reducing calcium levels (clotting factor IV) with sodium citrate, and Rh-negative group O blood.

Rh-negative group O

Used in emergencies when blood type is unknown
Can be donated to any recipient
First Rh-positive baby: mother must receive anti-D antibodies within 48 hours of delivery to prevent developing Rh antibodies.

Erythroblastosis Fetalis

Occurs when Rh-positive female marries Rh-positive male and the baby is Rh-positive.
During the delivery of the first Rh-positive baby, maternal circulation is exposed to fetal Rh-positive red blood cells, sensitizing the mother.
During subsequent pregnancies, maternal antibodies (IgG) cross the placenta and attack fetal red blood cells causing hemolysis.
Can lead to anemia, jaundice, brain damage (kernicterus), stillbirth, and even death of the second or following Rh-positive babies.
Treatment: exchange blood transfusion with Rh-negative group O blood

Blood Transfusion

Indications: blood loss, anemia, marked decrease in platelet count, clotting factor deficiencies
Precautions:
- Blood should be free of infectious diseases
- Blood groups must be compatible
- Blood must be stored at the correct temperature before transfusion
Changes in stored blood:
- Decreased red blood cell count
- Increased potassium levels
Complications:
- Incompatible blood transfusion: acute renal failure
- Hyperkalemia
- Hypercalcemia
- Iron overload

Blood Group Compatibility

Recipient's plasma should not contain agglutinins against the donor's red blood cells.
Group O is a universal donor because its red blood cells lack antigens.
Group AB is a universal recipient because its plasma lacks anti-A or anti-B antibodies.
Blood group A has surface antigen “A” and antibodies “Anti-B” in plasma.
Blood group B has surface antigen “B” and antibodies “Anti-A” in plasma.
Blood group AB has surface antigens “A” and “B” and no antibodies in plasma.

Hemophilia

Hemophilia A: Factor VIII deficiency
Hemophilia B: Factor IX deficiency
Hemophilia C: Factor XI deficiency

Important Blood Facts

Normal hemoglobin content: 11 gm/dl
Normal red blood cell count: 5 million/mm3
Normal blood volume decrease: 5%
Blood donation minimum time interval: 3 months

Single Best Answer (SBAs):

Most numerous blood group in ABO system: O
Percentage of Rh-positive people in the population: 85%
Normal bleeding time: 3 minutes
Anticoagulant effect: cooling of blood
Primary site of clotting factor synthesis: liver
Universal recipient: blood group AB
Treatment for erythroblastosis fetalis: Rh-negative group O blood
Normal distribution of blood groups: Group O > group A > group B > group AB
Least time interval between blood donations: 3 months
Incompatible blood transfusion: The donor is blood group AB and the recipient is blood group A

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Description

Test your knowledge on platelets, purpura, and hemostasis. This quiz covers normal platelet counts, their function in clot formation, and the causes and implications of purpura. Understand the complex processes involved in blood clotting and how the body stops bleeding.