Blood

Blood and Hemostasis Study Notes

Platelets

  • Definition: Platelets, also known as thrombocytes, are small cell fragments in the blood that help initiate the formation of blood clots.

  • Function:

    • They close breaks in damaged blood vessels, preventing excessive bleeding.

Blood Plasma

  • Composition: The liquid portion of blood consists of 92% water.

  • Functions:

    • Transport nutrients, gases, and vitamins.

    • Maintain fluid and electrolyte balance.

    • Help regulate pH levels in the body.

Plasma Proteins

  • Types of Plasma Proteins:

    • Albumins: Important for regulating blood pressure.

    • Globulins: Function primarily in the transport of antibodies.

    • Fibrinogen: A crucial component for blood clotting.

  • Medical Condition:

    • Multiple myeloma: A type of cancer that affects plasma cells, leading them to crowd out healthy cells and produce antibodies that may attack the body's own tissues.

Hemostasis

  • Definition: Hemostasis is the process of stopping bleeding. It involves the coagulation and clotting of blood to seal the site of a blood vessel damage.

  • Emergency First Aid:

    • Pressure can be applied to slow down bleeding.

    • A tourniquet may also be applied in severe cases.

    • Demonstrations on how to properly apply a tourniquet should be consulted for correct technique.

Key Events in Hemostasis

  1. Blood Vessel Spasm:

    • Mechanism: Serotonin acts as a vasoconstrictor, causing the blood vessel to shrink.

  2. Platelet Plug Formation:

    • Process: Platelets aggregate and close the opening in the damaged vessel.

  3. Coagulation:

    • Description: Fibrin forms over the platelet plug to further reinforce it, eventually forming a scab.

Coagulation Relevant Terms

  • Thrombin:

    • An enzyme found in blood plasma that causes the clotting of blood by converting fibrinogen to fibrin.

  • Coagulation:

    • Refers to the thickening of blood to form a clot, known medically as hematoma.

Clots and Emboli

  • Thrombus:

    • A blood clot that forms abnormally within a blood vessel.

  • Embolus:

    • A thrombus that has broken loose and is traveling through the bloodstream.

  • Pulmonary Embolism:

    • Occurs when a blood clot lodges in the lungs.

  • Cerebral Embolism:

    • Occurs when a blood clot travels to the brain.

Vitamin K Injections for Newborns

  • Purpose:

    • Newborns are given Vitamin K injections to prevent a bleeding disorder known as 'vitamin K deficiency bleeding' (VKDB).

  • Administration:

    • Babies typically receive the injection in the hospital shortly after birth.

Hemophilia

  • Common Name: Often referred to as "bleeder's disease."

  • Genetics:

    • Carried on the X chromosome and transmitted from mothers to sons.

  • Clinical Manifestation:

    • Patients with hemophilia experience difficulty in clotting blood, which can lead to severe hemorrhagic crises even with minor injuries.

Blood Donations

  • Process of Donation:

    • Blood is typically removed from the brachial vein.

  • Average Blood Volume:

    • An average adult has approximately 10 pints (around 5 liters) of blood in their body.

  • Typical Donation Volume:

    • Most blood donations involve the removal of about 1 pint (½ liter) of blood.

Plasma Donation

  • Procedure:

    • A machine collects plasma from the blood while returning red blood cells (RBCs) back to the donor.

Uses of Donated Blood

  • Patients with Hemophilia:

    • Blood donations help replenish blood and clotting factors that hemophiliacs lack.

  • Patients with Sickle Cell Disease:

    • Donations aid in reducing sickle-shaped cells in circulation.

  • Situations Requiring Replacement:

    • Blood donations are critical for replacing blood losses after injuries or surgical procedures.