Cardiovascular System

Blood group A is named for having the A antigen on the RBC.

During delivery of the first child, foetal blood may enter the maternal system from the placenta. The mother will then produce agglutinins against rhesus antigen D. These can cross the placenta in a subsequent pregnancy and, if the second baby is Rh+, attack the foetal erythrocytes causing newborn haemolytic disease. The disorder can be easily prevented by administration of anti-D antibodies to the mother after the first delivery.

Skeletal muscle is voluntary, while cardiac muscle is not under our conscious control. A skeletal muscle cell is a syncytium (composed from the amalgamation of many small cells (myoblasts)), while the myocardium behaves as a functional syncytium – the cells contract in unison.

The SA node contains cells that will depolarise at a faster rate than others in the heart. If it fails, these other places will depolarise, but their rate will be slower than that of the SA node.

The mitral valve is between the left atrium and left ventricle.

Valves prevent blood in veins from flowing away from the heart, while contracting skeletal muscle compresses the veins, and this pushes blood through them towards the heart (as the valves prevent blood form being pushed in the other direction).

Atrial natriuretic enzyme (ANP) exerts effects that result in a decrease in BP.

Ventricular systole refers to contraction of the ventricles. The other statements are wrong.

Sinusoidal capillaries have gaps between their endothelial cells large enough for cells to pass through. In addition, their basement membrane, being incomplete, presents a lower barrier to extravasation.

Osmolality is the number of osmoles (osmol) of solute per kilogramme of solvent. (Osmolarity (with an “r”) is defined as the number of osmoles of solute per litre of solution.)