- published: 19 Feb 2016
- views: 76471
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.
Coulda been my grandpa, coulda been my preacher
Coulda been my third grade history teacher
Somebody said it and I'll never forget it
Mighta been my daddy, mighta been my mama
Mighta been Dolly Parton or the Dalai Lama
They were words to the wise
And they hit me right between the eyes
If you wanna write a song, better get a guitar
If you wanna win Daytona, better get you a car
If you wanna be Picasso, better get you some paint
Son, you are what you do
And if you don't, then you ain't
Coulda been a stranger, coulda been a friend
Coulda been a commentator on CNN
Talkin' through my TV directly to me
Mighta been my butcher, mighta been my baker
Mighta been an outta work undertaker down at the Superette
Who gave me this reality check
If you wanna go to heaven, you better go to church
If you wanna promotion, you better get to work
If you wanna catch the big one, better get you some bait
Yeah, you are what you do
And if you don't then you ain't
If you want an education, you better stay in school
Get some sunglasses if you wanna be cool
Talk to Mother Teresa if you wanna be a saint
Yeah, you are what you do
And if you don't, then you ain't
Yeah, you are what you do