What material is found in the hollow spaces of long bones?

A. Dendritic cells: Dendritic cells are antigen-presenting cells that originate from precursor cells in the bone marrow, but they do not differentiate from monocytes.

B. Bacterial cells: Bacterial cells are pathogens and do not differentiate into any immune cells.

C. Natural killer cells: Natural killer cells are a type of lymphocyte involved in the innate immune response but do not differentiate from monocytes.

D. Monocyte cells: Monocytes are a type of white blood cell that, upon migrating into tissues, differentiate into macrophages, which play a key role in phagocytosis and immune response.

A. Increased afterload: Increased afterload, the resistance the heart must overcome to eject blood, typically reduces stroke volume because the heart has to work harder to push blood against higher pressure.

B. Decreased heart contractility: This would reduce stroke volume, as the heart would be less effective at pumping blood.

C. Increased preload: Preload refers to the volume of blood in the ventricles at the end of diastole. An increased preload stretches the heart muscle, which typically leads to a stronger contraction and higher stroke volume.

D. Decreased blood pressure: While low blood pressure may reduce afterload, it doesn't directly increase stroke volume unless other factors are at play.