5 main parts


Typically 7% to 9% of the body's total weight, varies with size and weight but is usually 4 to 6 iters

  1. bright red (oxygenated)
  2. dark red/purplish (unoxygenated)
  3. much more dense than pure water
  4. typical volume in adult male 5-6 liters
  5. typical volume in adult female 4-5 liters


  1. Distribution & Transport

oxygen from lungs to body cells

  • carbon dioxide from body cells to lungs
  • nutrients from GI tract to body cells
  • nitrogenous wastes from body cells to kidneys
  • hormones from glands to body cells

2. Regulation (maintenance of homeostasis)
  • maintenance of normal body pH -- blood proteins (albumin) & bicarbonate
  • maintenance of circulatory/interstitial fluid-- electrolytes and blood proteins (albumin)
  • maintenance of temperature (blushed skin)

3. Protection
  • platelets and proteins "seal" vessel damage
  • protection from foreign material & infections--leukocytes, antibodies, complement proteins


  • Caved in the middle, no nucleus, thin center thick outer cell
  • Function: help transport carbon dioxide away from cells to lungs so it can be disposed into the external environment
  • Function: red pigment (hemoglobin) bonds with oxygen to create oxyhemoglobin used to transport large amounts of oxygen to body cells
  • Hemoglobin can also carry small amounts of CO2 carried by the blood to form carbaminohemoglobin


  • Granulocyrics Includes: neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
  • Function: they defend the body from cancer cells that can form inside our tissue cells and from microorganisms that have invaded our bodies
  • Eosinophils kill parasites and have a role in allergic reactions
  • Neutrophils are the one of the body's main defenses against bacteria
  • Basophils are not well understood, but they function in allergic reactions
  • Monocytes enter the tissue, where they become larger and turn into macrophages. There they can phagocytize bacteria (up to 100 in their lifetime) throughout the body. These cells also destroy old, damaged and dead cells in the body



Consists of 90% water and 10% nutrients

Makes up around half of the bloods mass in the body

Can be easily separated because the heavier blood cells will sink to the bottom and the plasma will remain on the top

Usually a straw, gray, or brownish color

Without plasma the blood cells would have no medium to travel on through out the body

As plasma circulates through the body, it acts like a milkman making deliveries. The plasma drops off various substances to the cells of the body, and collects waste products for processing

Blood plasma flows constantly, and the components of plasma are constantly being renewed

In addition to providing nutrition and waste cleanup, blood plasma also harbors immune system cells which attack infections in the body, and it is used to deliver hormones and clotting factors to areas where they are needed


Platelets are the smallest type of blood cell--smaller than either red or white cells

Along with plasma, these three types of cells comprise the blood in your veins. Platelets are fractured pieces of very large bone marrow cells called megakaryocytes, which means they're not technically full cells but broken, irregularly shaped fragments of cells

When blood vessels are damaged and blood loss begins, the very small and light platelets are the first cells to reach the ruptured surface of the vessel

The platelets, in combination with nutrients like vitamin K and a protein called fibrinogen, form a thick, tough web of material called fibrin. A cluster of fibrin threads covers the hole in the blood vessel and prevents blood from escaping while repairs are done

A body with an abnormally high platelet count can sometimes develop blood clots--buildups of fibrin within the blood vessels that obstruct proper flow

a body with too few platelets may be unable to clot its blood properly, giving cuts that would otherwise be minor a risk of serious blood loss