Sistema Rh, MN e Eritroblastose Fetal - Aula 08 - Módulo 2: Genética

Understanding Blood Types and the Rh System

Introduction to the Course

• The course "Dominando A Genética" is currently open for enrollment with a limited-time discount coupon available. It includes six different study guides and over 120 exercises designed to provide hands-on learning experiences.

Overview of Blood Systems

• The lesson begins by explaining the ABO blood system, which categorizes blood types as A, B, AB, or O. Following this, the focus shifts to the Rh system that determines if blood is positive or negative. This distinction is crucial for understanding blood transfusions.

The Rh Factor Explained

• The term "Rh" originates from studies conducted on rhesus monkeys, which have a similar blood system to humans. Understanding this factor helps in identifying whether an individual has the Rh protein on their red blood cells (hemácias).

• An individual classified as Rh-negative lacks the Rh factor on their red blood cells, while those who are Rh-positive possess it. This difference is vital for safe blood transfusions and compatibility between donors and recipients.

Blood Donation Compatibility

• Individuals with O-negative blood can donate to anyone but can only receive from other O-negative donors. Conversely, those with O-positive can only donate to themselves or other positive types due to potential immune reactions against foreign antigens present in incompatible blood types.

• It’s emphasized that individuals with Rh-negative are homozygous recessive (rr), while those who are Rh-positive can be either homozygous dominant (RR) or heterozygous (Rr). Understanding these genetic backgrounds aids in predicting compatibility during transfusions.

Exploring Other Blood Systems: MN System

Characteristics of MN Blood Group

• The MN system consists of two alleles: M and N, both of which are dominant traits leading to three possible phenotypes: MM (only M factor), NN (only N factor), and MN (both factors present). This system does not typically cause incompatibility during standard blood transfusions but may pose challenges in specific medical situations like bone marrow transplants.

Erythroblastosis Fetalis: A Critical Condition

Definition and Importance

• Erythroblastosis fetalis refers to a condition where fetal red blood cells are destroyed by maternal antibodies due to incompatibility between maternal and fetal blood types—often involving the Rh factor.

Understanding Fetal Erythroblastosis

Overview of Erythroblastosis Fetalis

• Erythroblastosis fetalis is a condition where the mother's immune system attacks the baby's red blood cells, leading to their destruction.

• The baby experiences a critical need for red blood cells, resulting in the release of immature red blood cells (erythroblasts) into circulation.

• This condition is also known as hemolytic disease of the newborn, characterized by the breakdown of fetal red blood cells.

Conditions Leading to Erythroblastosis

• For erythroblastosis fetalis to occur, specific conditions must be met: the father must be Rh-positive and the mother Rh-negative.

• During a normal pregnancy, there is no mixing of maternal and fetal blood unless complications arise (e.g., placental abruption).

Mechanism of Sensitization

• After birth, when the placenta detaches from the uterine wall, small amounts of fetal blood can enter the mother's bloodstream.

• If this occurs and if the baby is Rh-positive while the mother is Rh-negative, she becomes sensitized and produces antibodies against Rh-positive blood.

Implications for Subsequent Pregnancies

• The antibodies produced during sensitization can cross the placenta in future pregnancies, attacking any subsequent Rh-positive fetus.

• This attack may lead to severe anemia in the newborn or even miscarriage due to ongoing immune response from the mother.

Prevention Strategies

• To prevent sensitization in future pregnancies, medical intervention involves administering an injection (often referred to as a vaccine but technically not one).

• This injection contains antibodies that neutralize any fetal Rh-positive blood that enters maternal circulation during delivery or shortly before.

Importance of Medical Monitoring

• Continuous monitoring during pregnancy allows healthcare providers to administer this preventive treatment effectively whenever necessary.

• It’s crucial for all pregnancies involving an Rh-negative mother and an Rh-positive father to follow this protocol to avoid complications.

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