Core concept

Structure and function

What a structure can do follows from its shape and parts, from molecules to whole organs.

What a structure does follows from how it is built, at every level. A capillary wall is a single thin layer of cells, so gases cross it in a fraction of a second. The left ventricle has a wall about three times thicker than the right because it pumps against much higher pressure. A heart valve's flaps are tethered by cords so they close under pressure instead of flipping inside out.

Use this in both directions. Given a structure, predict what it can do: a thick, muscular wall squeezes; a thin, leaky one exchanges. Given a job, predict the structure: a surface built for absorption will be folded to add area. It is the fastest way to remember anatomy, because each detail has a reason.

Where it shows up

Orientation to the body

Chemistry and physics for physiology

Cells

Tissues

Signals, repair and control

Integumentary system

Bone tissue

The skeleton

Joints

Muscle tissue

The muscular system

Nervous tissue and neural signaling

The brain and spinal cord

Nerves, reflexes and pathways

Special senses

The autonomic nervous system

Blood

The cardiovascular system

Lymphatic and immune systems

The respiratory system

The digestive system

The urinary system

The reproductive system

Development and inheritance

Practice it across systems

Mixed questions on structure and function