Human Heart and blood

Heart and blood THE HEART IS ONE OF THE BODY’S MARVELS , pumping blood around the body ceaselessly . Every second of the day , even as you sleep , the heart’s powerful muscles are contracting to send a jet of blood shooting through the body’s intricate network of blood vessels . Blood flows right round the body and back to the heart , creating a complete circulation to every part of the body . Without it , you would quickly die . Blood carries the oxygen , nutrients and chemicals that every body cell needs to survive , and washes away all the waste products , including carbon dioxide .Human Heart and blood

FACTS: About blood

What is blood?http://What is blood?
It is a complex mix of cells and platelets in a clear yellowish fluid called plasma.  Washed along in the plasma too are salts, hormones, fats and sugars.
Red blood cells
The most numerous blood cells are button-shaped ‘red’ blood cells which are like rafts that ferry oxygen around the body, held on board by a protein called haemoglobin.
  White blood cells
Big ‘white’ blood cells play a vital role in the body’s defense against disease.  White blood cells called neutrophils swallow invaders.  Lymphocytes help identify them.
  • Platelets
Tiny cell fragments called platelets help plug leaks such as cuts.
Blood is a mix of red cells (erythrocy(erythrocytes)tes), white cells (leucocytes) and tiny platelets in plasma.

FACTS: About circulation

DATA: Blood & heart

Blood flows out of the heart through large blood vessels called arteries, which branch into smaller arterioles and then into tiny capillaries.

Blood flows through the arteries at Im a second
There are 60,000km of capillaries in the body. 
The heart beats on average 80 times a minute.

Blood flows back to the heart through small venules that join to form larger veins.  The load of oxygen makes blood redder in the arteries than the veins.
Double circulation
There are two systems of circulation in the body, each pumped by a different half of the heart. 
Sides of the heart
The left of the heart drives the ‘systemic’ circulation which carries oxygen-rich blood from the lungs around the body.  The right half of the heart drives the ‘pulmonary’ circulation, which drives blood through the lungs to the left side of the heart. 
The pumping of the heart sends regular shock waves through the circulation, detectable as a pulse.  To feel your pulse, lay two fingers gently on the inside of your wrist.  Counting the number of pulses tells you how fast your heart is beating.

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