THE THORAX AND THE ABDOMEN

Sheet No. 1

ANATOMICAL STUDIES OF THE TRUNK

The following observations pertain to the structure of the ribs and the movement of the diaphragm. Leonardo was one of the first to accurately describe the mechanical action of the diaphragm during respiration.

The heart is a tool of the soul, moved by the heat of the blood.

When the lung expands, the ribs must necessarily rise to create space for the air. This occurs through the action of the external intercostal muscles. Observe how the spine serves as the foundation for all these bones, like the mast of a ship. Leonardo frequently used architectural and mechanical metaphors to explain the human body.

The vessels of the liver are distributed like the roots of a tree. The portal vein carries the nourishment from the stomach to be refined. original: "vena porta"

PART OF THE BODY	MECHANICAL FUNCTION
Ribs	Protection and expansion
Diaphragm	The primary driver of breath
Spine	The central support

Note the curvature of the lower back.