A cross-section of the heart revealing the internal structures.

Close-up of anterior view of cross-section of heart.

Transverse section of the male pelvis showing the inguinal canal (left side with intercrural fibers).

Simple drawing of cross section of skin with three needles administering injections at different angles. Intramuscular at 90 degrees (left), subcutaneous at 45 degrees (center), and intradermal at 15 degrees (right).

Cross-section of forearm at level midway between elbow and wrist showing arrangement of muscles. Orientation drawing in upper left corner.

Two cross sections of the heart, side by side, showing the changes in heart structure during its pumping action.

Cross-section of arm at level just above elbow showing arrangement of muscles around central bone. Orientation drawing in upper left corner.

Illustration of a coronal section of the heart with the sinuatrial node and its conduction system indicated in red and the atrioventricular node and its conduction system indicated in blue.

Two cross-sections of the right hand at the level of the wrist to show the anatomy involved in carpal tunnel syndrome. Orientation drawing upper left.

Four examples of placental placement within uterus, shown as cross-sections (top) and schematically from below (bottom). Normal placenta (far left), low implantation (left), partial placenta previa (right), total placenta previa (far right).

Cross-section of the left side of heart.