The relationship between the two features is often expressed as…

• Form follows function: a body part can perform its function only if it is a certain shape or
• Form determines function: the shape of a body part directly affects what it can do.

When this relationship principle is continuously applied to studying anatomy and physiology, it helps make the material easier to understand.

Examples

Thumb Carpometacarpal Joint

Its Form

The thumb carpometacarpal joint is formed by the first metacarpal of the thumb and the trapezium carpal (wrist) bone. The articulating surface of each bone is saddle-shaped, meaning it is concave in one direction and convex in the perpendicular direction. The saddle-shaped articulating surfaces fit together at right angles and are complementary. One surface’s concavity matches the other’s convexity, and vice versa.

Its Function

This reciprocal concavo-convex relationship increases the thumb’s flexibility, including a motion called opposition. During this motion, the thumb moves forward (anteriorly) from the palm and sideways (medially) toward the tips of the other fingers, allowing the hand to grasp and manipulate objects.

Hemoglobin Molecule

Its Form

Hemoglobin is a complex protein composed of four globular subunits. Each subunit contains a unique sequence of amino acids that determines its three-dimensional structure through folding. The specific amino acid sequence also influences how the subunits bond to form the complete hemoglobin molecule.

Its Function

The three-dimensional conformation of the hemoglobin molecule is essential for its primary function, which is to transport oxygen. This particular structure enables hemoglobin to bind with oxygen in the lungs and release it to the body’s tissues. In tissue cells, oxygen plays a crucial role in cellular respiration and the creation of ATP (adenosine triphosphate), which stores energy.