Compressive forces are perpendicular to the vertebral disc, even when the person is lyingsupine.a. Trueb. False

The correct answer is b. False.

When discussing compressive forces acting on the vertebral discs, it's important to consider the body's position. While a person is lying supine (on their back), the gravity acting on their body does create compressive forces, but these forces are not solely perpendicular to the vertebral discs. The orientation of the body and the alignment of the spine also influence how these forces are distributed across the discs.

In a supine position, the load on the intervertebral discs is more evenly distributed compared to when standing or sitting. However, the discs experience a combination of axial (vertical) compression and some shear forces, depending on the alignment of the spine and the position of the limbs. Therefore, it is not accurate to say that compressive forces are strictly perpendicular when a person is lying supine, making the statement false.