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Relationship of Form and Function

(Sample Lesson)


There is a direct relationship between the form (shape) of a human body part (molecule, cell, tissue, organ, or organ system) and the way it functions. 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 the study of anatomy and physiology, it helps make the material easier to understand.


(A) The unique form (shape) of the thumb carpometacarpal joint increases the flexibility of the thumb and makes it possible for the hand to grasp and manipulate objects (function).

To do so, the thumb moves forward (anteriorly) from the palm and sideways (medially) toward the tips of the other fingers. This motion is called opposition.

Form: the thumb carpometacarpal joint shape allows thumb opposition.
Form: the shape of the thumb carpometacarpal joint
Function: objects are grasped and manipulated using thumb opposition.
Function: thumb opposition.

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(B) The hemoglobin molecule is a complex protein consisting of four, globular subunits. Each subunit is composed of a long and unique sequence of linked amino acid molecules. The sequence of amino acids controls the 3-D conformation or folding of each subunit and the way in which the subunits are bonded together. In turn, the form (shape) of the hemoglobin molecule determines its ability to bind oxygen (function).

Form: a hemoglobin molecule
consists of four globular subunits.
Form: four globular subunits of a hemoglobin molecule.

Function: each hemoglobin subunit
can bind a molecule of O2.
Function: hemoglobin binds up to 4 molecules of oxygen (O2).

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