Journey Of The Blood (Page 4 of 6) in pdf

Reading Passage: Journey of Blood

Imagine hiking 60,000 miles. You sure would have a lot of blisters! Sixty thousand miles is a long way. It’s almost two

and half times around the world, or about a quarter of the way to the moon. And yet, that is also about the total

length of all the blood vessels in your body. Every time your heart pumps, it is pumping blood around 60,000 miles of

arteries, veins and capillaries.

The heart is an astonishing organ. Minute after minute, hour after hour, day after day, it pumps away. And there it

sits, thump, thump, thump – pumping for a whole lifetime while you are for the most part completely unaware of it.

Imagine you could shrink to the size of a cell and take the same journey as a red blood cell around the body. What

would that journey be like? What kinds of adventures and strange objects and terrains might you encounter? Unlike

a typical journey, your journey does not start and end at the same place. Your journey starts in the bone marrow,

which produces red blood cells, alongside white blood cells and platelets.

From the bone marrow, you travel to the heart, carried along in deoxygenated blood. You enter a chamber of the

heart, then another, before being pumped to the lungs. While in the lungs, you absorb some oxygen molecules. Then

you return to the heart, through two more chambers. The powerful heart muscle pumps you through the body’s

biggest blood vessel, the aorta.

The aorta can send you any number of places in the body since it splits into three more arteries. If you enter one of

the carotid arteries, you travel up the neck to the brain. You can feel these arteries on the side of your throat. On the

other hand, you might be diverted into one of the less glamorous subclavian arteries. These tubes supply the

muscles of the arms, down to the wrists, where you can feel your pulse. Alternatively, you might enter the

descending thoracic aorta, which feeds various internal organs and the leg muscles.

Wherever you go, you give up your precious oxygen molecules. Chances are you give up oxygen to the brain or

digestive organs. Together, these use about three-quarters of the body’s energy while resting

. As you come closer

to oxygen-hungry tissues, you pass through capillaries. Your oxygen molecules diffuse into tissues, and you absorb

some carbon dioxide, the main by-product of metabolism. You enter a vein then travel back to the heart. You end up

in one of the main veins entering the heart, the superior or inferior vena cava. From here you start your journey all

over again!

After about four months, your journey comes to an end. A red blood cell typically lasts about 120 days

. Traveling at

almost two miles per hour

, you might travel one-tenth of the total length of the 60,000-mile circulatory system. Most

likely, your destiny is to be engulfed by white blood cells in lymph nodes, the liver, or the spleen. Alternatively you

might just disintegrate while in the blood stream. Again, ever-vigilant white blood cells would mop up the fragments.

Whatever your fate, it was certainly an amazing journey!

C leveland C linic H ow D oes B lood T ravel T hrough Y our B ody

blood-‐travel-‐through-‐body

M cClave S A, S nider H L ( 2001) D issecting t he e nergy n eeds o f t he b ody. C urr O pin C lin N utr M etab C are 4 (2):143-‐7.

L ife C ycle o f t he E rythrocyte. R etrieved f rom

h ttp://faculty.ucc.edu/biology-‐potter/life_cycle_of_the_erythrocyte.htm

C alculated f rom a f igure o f 9 2 c m p er s econd, g iven b y G ardin J M, e t a l. ( 1984) E valuation o f b lood f low v elocity i n t he a scending a orta a nd

main p ulmonary a rtery o f n ormal s ubjects b y D oppler e chocardiography. A m H eart J . 1 07(2):310-‐9.

Journey Of The Blood Page 4

Related Articles

Related forms

Related Categories