Question

question 1
1 pts
the bulk of the heart wall is the thick, contractile middle layer called the
pericardium.
epicardium.
endocardium.
myocardium.
question 2
1 pts
the structure referred to as the pacemaker of the heart is(are) the:
sa node.
av node.
purkinje fibers.
av bundle.
question 3
1 pts
the term blood type refers to the type of blood cell
antibody.
antigen.
transfusion reaction.

Explanation:

• Question 1: The heart wall has three layers. The pericardium is the outer - covering sac. The epicardium is the outer layer of the heart wall. The endocardium is the inner lining. The myocardium is the thick, contractile middle layer responsible for the heart's pumping action.
• Question 2: The SA (sino - atrial) node initiates the electrical impulse that causes the heart to contract rhythmically, so it is called the pacemaker of the heart. The AV (atrioventricular) node delays the impulse slightly. The Purkinje fibers and AV bundle are part of the conduction system but do not initiate the impulse like the SA node.
• Question 3: Blood type is determined by the type of antigen (such as A, B, or Rh antigens) on the surface of red blood cells. Antibodies are in the plasma and react with foreign antigens. A transfusion reaction is an immune response (like agglutination) that occurs when incompatible blood is transfused.

Answer:

• Question 1: myocardium
• Question 2: SA node
• Question 3: antigen