The heart is a myogenic muscular organ found in all animals with a circulatory system (including all vertebrates), which pumps blood throughout the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart".

The vertebrate heart is principally composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue found only in this organ and responsible for the ability of the heart to pump blood. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males.

In invertebrates that possess a circulatory system, the heart is typically a tube or small sac and pumps fluid that contains water and nutrients such as proteins, fats, and sugars. In insects, the "heart" is often called the dorsal tube and insect "blood" is almost always not oxygenated since they usually respirate (breathe) directly from their body surfaces (internal and external) to air. However, the hearts of some other arthropods (including spiders and crustaceans such as crabs and shrimp) and some other animals pump hemolymph, which contains the copper-based protein hemocyanin as an oxygen transporter similar to the iron-based hemoglobin in red blood cells found in vertebrates.

Courage (also bravery, boldness, fearlessness, mettle, fortitude, or intrepidity) is the ability to confront fear, pain, danger, uncertainty, or intimidation. Courage is acting in spite of fear. "Physical courage" is courage in the face of physical pain, hardship, death, or threat of death, while "moral courage" is the ability to act rightly in the face of popular opposition, shame, scandal, or discouragement.

As a [desirable] quality, courage is discussed broadly in Aristotle's Nicomachean Ethics, where its vice of shortage is cowardice and its vice of excess is recklessness. 'live life not without fear, but with gallantry against it' : Christian L J Silver

In Roman Catholicism, courage is referred to as "Fortitude" as one of the four cardinal virtues, along with prudence, justice, and temperance. ("Cardinal" in this sense means "pivotal"; it is one of the four cardinal virtues because to possess any virtue, a person must be able to sustain it in the face of difficulty.) This is well expressed by Maya Angelou: