Blood Components Platelets

8/3/2019 Blood Components Platelets

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Interested in learning more? Platelets are sometimes called thrombocytes. Thrombocytopenia is a disorder that results in a reduced platelet count. (You could

investigate this disorder for your project if you desire).

Platelets

Platelets play an extremely important

in control of blood loss through theirinvolvement in the clotting

mechanism. Platelets are irregularly-

shaped bodies/fragments (not cells)

with ‘sticky’ surfaces, that allow them

to seed clot formation. When a person

bleeds externally, the end result of

clotting is a visible and palpable ‘scab’

made from a dried mesh of blood cellsand a mesh of fibrin proteins, along

with other extracellular proteins.

Internal bleeding results in a similar

blood clotting process, involving

clotting factors, platelets, and

extracellular proteins, but appears as

a bruise. Both scabs and bruises are

clots that control blood loss and lead to healing.

Below: Resting platelet = top left

Activating/Flattening towards bottomright.





Aspirin, along with chemicals called

blood thinners, impair platelet

function by reducing their ‘stickiness’,

and thus their ability to initiate and

maintain a strong clotting process.

Aspirin is used long-term, at low doses, to help prevent heart attacks, strokes,

and blood clot formation in people at

high risk of developing blood clots. It

has also been established that low

doses of aspirin given immediately

after a heart attack, reduce the risk

of another heart attack and of the

death of cardiac muscles.

For blood to coagulate, plateletsfirst aggregate to form a platelet plug,

then release chemical signals that are

responsible for activating the 13

clotting factors. Normally, this

process is essential to control

bleeding (homeostasis) and is a critical

first step in the healing process.

Clotting inhibitors are an importantnegative feedback that keeps

coagulation from getting out of hand.

Fibrinolysis refers to the breakdown

of fibrin, and occurs once an injury

has been healed.

Importantly, a stroke is the result of a

clot forming in (or breaking off and

depositing in) an artery supplying thebrain with oxygen. If the flow of

oxygen is broken, brain damage,

paralysis, or even death may result. A

Below: Both red & white blood cellsbecome trapped in fibrin webs during

clot formation, providing the clot with

its characteristic colour.





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clot that occludes a coronary artery

(responsible for supplying the heart

muscles with oxygen) will result in a

heart attack.

Platelets are produced by

megakaryocytes within the bone

marrow. In contrast to the

erythrocyte, which has adiameter of 7-8 microns,

megakaryocytes (shown left

amidst red blood cells) have an

average diameter of 20 to 25

microns. Each megakaryocyte

produces a total of 1000 to 3000

platelets.

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Blood Components Platelets