- published: 02 Nov 2015
- views: 6471054
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.
Sing it from the mountain
Tell it to the people
Sing it from the mountain
Tell it to the people
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
You got this feeling you? ve been wanting to share
It makes you feel as though you? re walking on air
You say this feeling needs a thing called love
Then you should tell the one you? re thinking of
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
It is time to show it
In every person, there? s a yearning to love
This is the message that is sent from above
In every heart, there? s a love so true
That? s why I? m sayin? that I love you
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
It is time to show it
You know that I love you
You say you love me too
So why don? t you let me know
Let? s open our hearts and let the feelings show
Sing it from the mountain
Tell it to the people
Sing it from the mountain
Tell it to the people
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
It is time to show it
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
It is time to show it
When you say you love somebody
You got to let them know about it
You should let them know it
When you say you love somebody
You got to let them know about it
It is time to show it
When you say you love somebody
You got to let them know about it
You should let them know it