Unit 16

Pre-text assignments

1 Learn the key words and phrases:

transmit, clump together, obstruct, agglutinogens, agglutinins, dilute, adverse reaction, inherited trait

2 Translate and memorize the explanation to the terms:

transfusion the act of transfusing fluid into a vein or

artery

precaution a measure taken beforehand to prevent harm

or secure good

inheritance the reception of genetic qualities by

transmission from parent to offspring

3 Find substitutes for the given phrases:

1) pertaining to injury a) transfusion

2) introduction of blood into the veins b) hypertension

3) inflammation of the bladder c) traumatic

4) high blood pressure in the arteries d) transplant

5) to remove and plant in another place e) cystitis

Blood Groups and Transfusions

Early attempts to transfer blood from one person to another produced varied results. Sometimes the person receiving the transfusion was aided by the procedure. At other times, the recipient suffered a blood reaction in which the red blood cells clumped together, obstructing vessels and producing other serious consequences.

Eventually, it was discovered that each individual has a particular combination of substances in his or her blood. Some of these substances react with those in another person's blood. These discoveries led to the development of procedures for typing blood. It is now known that safe transfusions of whole blood depend upon properly matching the blood types of the donors and recipients.

Agglutinogens and Agglutinins

The clumping of red cells following a transfusion reaction is called agglutination. This phenomenon is due to the presence of substances called agglutinogens (antigens) in the red cell membranes and substances called agglutinins (antibodies) dissolved in the plasma.

Blood typing involves identifying the agglutinogens that are present in a person's red cells. Although many different agglutinogens are associated with human erythrocytes, only a few of them are likely to produce serious transfusion reactions. These include the agglutinogens of the ABO group and those of the Rh group.

Avoiding the mixture of certain kinds of agglutinogens and agglutinins prevents adverse transfusion reactions.

ABO Blood Group

The ABO blood group is based on the presence (or absence) of two major agglutinogens in red cell membranes – agglutinogen A and agglutinogen B – which are present at birth as a result of inheritance. The erythrocytes of each person contain one of the four following combinations of agglutinogens: only A, only B, both A and B, or neither A nor B.

A person with only agglutinogen A is said to have type A blood; a person with only agglutinogen B has type B blood; one with both agglutinogen A and B has type AB blood; and one with neither agglutinogen A nor B has type 0 blood (also called type H). Thus, all humans have one of four possible blood types – A, B, AB, or 0.

Because an agglutinin of one kind will react with an agglutinogen of the same kind and cause red blood cells to clump together, such combinations must be avoided. The major concern in blood transfusion procedures is that the cells in the transfused blood not be agglutinated by the agglutinins in the recipient's plasma. For this reason, a person with type A (anti-B) blood must not be given blood

of type B or AB, because the red cells of both types would be agglutinated by the anti-B in the recipient's type A blood. Likewise, a person with type B (anti-A) blood must not be given type A or AB blood, and a person with type 0 (anti-A and anti-B) blood must not be given type A, B, or AB blood.

Because type AB blood lacks both anti-A and anti-B agglutinins, it would appear that an AB person could receive a transfusion of blood of any other type. For this reason, type AB persons are sometimes called universal recipients. It should be noted, however, that type A (anti-B) blood, type B (anti-A) blood, and type0 (anti-A and anti-B) blood still contain agglutinins (either anti-A or anti-B) that could cause agglutination of type AB cells. Consequently, even for AB individuals, it is always best to use donor blood of the same type as the recipient blood. If the matching type is not available and type A, B, or 0 is used, it should be transfused slowly so that the donor blood is well diluted by the recipient's larger blood volume. This precaution usually avoids serious reactions between the donor's agglutinins and the recipients agglutinogens.

Similarly, because type 0 blood lacks agglutinogens A and B, it would seem that this type could be transfused into persons with blood of any other type. Therefore, persons with type 0 blood are sometimes called universal donors. Type 0 blood, however, does contain both anti-A and anti-B agglutinins, and if it is given to a person with blood type A, B, or AB, it too should be transfused

slowly to minimize the chance of an adverse reaction.

Rh Blood Group

The Rh blood group was named after the rhesus monkey in which it was first studied. In humans, this group includes several Rh agglutinogens (factors). The most important of these is agglutinogen D; however, if any of the Rh factors are present in the red cell mernbranes, the blood is said to be Rh positive. Conversely, if the red cells lack Rh agglutinogens, the blood is called Rh negative.

As in the case of agglutinogens A and B, the presence (or absence) of an Rh agglutinogen is an inherited trait. Unlike anti-A and anti-B, agglutinins for Rh (anti-Rh) do not appear spontaneously. Instead, they form only in Rh-negative persons in response to special stimulation.

If an Rh-negative person receives a transfusion of Rh-positive blood, the recipients antibody – producing cells are stimulated by the presence of the Rh agglutinogen and will begin producing anti-Rh agglutinin. Generally no serious consequences result from this initial transfusion, but if the Rh-negative person – who is now sensitized to Rh-positive blood – receives another transfusion of Rh-positive blood some months later, the donor's red cells are likely to agglutinate.

Post-text assignments

1 Respond to the given assigments:

1 Distinguish between agglutinogens and agglutinins.

2 What is meant by blood type?

3 What is the main concern when blood is transfused

from one individual to another?

4 Why is a type AB person called a universal recipient?

2 Form sentences of your own using the following words and phrases:

immunity to infection, on exertion, mistaken for plasma, life-span, combatting infection, reversible function, responsible for, ulcerative lesions, engulf, deficient in vitamin K, due to hemorrhage, to test for the presence of, capillary fragility

3 Translate into English:

1 Кров - це рідка тканина, яка виконує багато різноманітних функцій.

2 Рідка частина крові називається плазмою.

3 Кров насичується киснем у легенях.

4 У дорослих кров становить від 1/12 до 1/14 маси тіла.

5 Білірубін - продукт гемоглобіну.

6 Запальні стани характеризуються підвищенням ШОЕ, тобто швидкості осідання еритроцитів.

7 Білі кров'яні тільця, або лейкоцити, відіграють важливу роль у боротьбі з інфекціями.

8 Грунтовні знання про сумісність груп крові є необхідними для переливання крові.