Final answer:
The walls of the ventricles in the heart are lined with trabeculae carneae, ridges of cardiac muscle covered by endocardium. The ventricular walls are also attached to the papillary muscles and chordae tendineae. These structures help to provide structural support and prevent the backflow of blood into the atrium during ventricular contraction.
Step-by-step explanation:
The walls of the ventricles in the heart are lined with trabeculae carneae, which are ridges of cardiac muscle covered by endocardium. These muscular ridges provide structural support and help to increase the contractile force of the ventricles. Additionally, the walls of the right ventricle are reinforced by a band of cardiac muscle known as the moderator band, which connects to the inferior papillary muscle.
Another important structure involved in the attachment of the ventricular walls is the chordae tendineae. These strong strands of connective tissue are attached to the flaps of the tricuspid valve and connect to the papillary muscles. The tension generated by the contraction of the papillary muscles helps to hold the valve flaps in place and prevent the backflow of blood into the atrium during ventricular contraction.