L1 - The Heart

objectives

• Describe the structure of the heart including the muscular wall and septum, atria, ventricles, valves and associated blood vessels

Unicellular vs. Multicellular Organisms

Unlike unicellular organisms, larger organisms have a small surface area to volume ratio, and therefore diffusion does not occur quickly enough to sustain them.

Larger organisms therefore require organ systems with specialised adaptations to supply all of their cells with nutrients and oxygen (through diffusion) and collect waste (through diffusion) to be excreted from the body.

The organ systems we use to do this is called the circulatory system.

The Circulatory System

The Human Heart

Heart Structure

• The heart has 4 chambers.
• Atria at the top and ventricles at the bottom.

• The walls of the atria are thinner than the ventricles as they receive blood at a relatively low pressure from the veins and they are not required to pump the blood very far.
• Ventricles are stronger and have more muscular walls. They need to be able to pump the blood out of the heart.
• The left ventricle is larger than the right ventricle as its job is to push the blood around the entire body whereas the right side only pushes the blood to the lungs.

You must learn the structure of the Heart!