BLOOD

• The cells and cell parts are called

  formed elements
• A hematocrit blood test measures the ratio of the volume

  of red blood cells to the total volume of blood. In this test, a tube of whole blood is

  spun in a centrifuge and the formed elements separate from the plasma.
• Albumins. Albumins are transport proteins dissolved in plasma. An example of an

  albumin is the plasma protein that binds to thyroid hormone to extend its half-life

  while traveling in the blood
• Globulins. are another class of plasma proteins. Examples of

  globulins are the antibodies produced by white blood cells to fight foreign

  pathogens.
• Fibrinogen is a clotting protein dissolved in

  plasma.
• clotting factors, are needed for the clot to

  form.
• Serum is plasma with the fibrinogen and clotting factors removed.
• Ions in solution are electrolytes.

  An example of an ion transported in plasma is Ca2+. Osteoblasts deposit excess

  calcium ions from the blood into bone (the skeletal system chapter). Other ions in

  plasma include Na+, K+, and Cl−.
• Nutrients are necessary chemicals for normal body function. Glucose is a good

  example.
• Waste products are by-products of chemical reactions that occur in the cells.

  They are secreted into the blood for removal.
• bilirubin

  a waste produced from the breakdown of worn-out red blood cells.
• Gases, which enter or leave the body through the lungs, may be required by cells

  for chemical reactions to occur.
• Regulatory substances are chemicals used for communication.
• Erythrocytes is a biconcave disk, thick

  around its rim and thin at its center. This shape gives the cell a greater surface area for

  an exchange of gases in the lungs and at the tissues. the most plentiful

  of the formed elements—function to transport oxygen and carbon dioxide.
• Leukocytes These cells are commonly called white blood cells. Each of the five types
• contain small granules that differ in

  color when stained. These leukocytes are classified as granulocytes.
• agranulocytes because they do not contain visible

  granules.
• Neutrophils are the most common type of leukocyte. Neutrophils typically

  make up 40% to 70% of all the white blood cells in circulation. Each has a

  lobed nucleus and faint granules in the cytoplasm that contain lysozymes used to destroy

  bacteria. The number of neutrophils in circulation rises in response to bacterial infections.
• Basophils are the least common type of leukocyte. Basophils average from

  0% to less than 2% of all the white blood cells in circulation. The large, dark blue-purple

  granules are so prominent that it is difficult to see the S- or U-shaped nucleus.

  The number in circulation tends to increase with allergies.

  primary function is to release two chemicals histamine and heparin for defense
• Histamine released from basophils causes vessels to dilate (expand). This brings

  more blood to an area and causes blood vessel walls to become more permeable.

  The increased blood flow and permeability allow more leukocytes to move out of

  the blood vessels into injured tissues more quickly.
• Heparin released from basophils is an anticoagulant, which means it prevents

  clotting. This chemical allows other leukocytes to move more freely.
• Eosinophils Eosinophils make up 0% to 6% of the total circulating white blood

  cells. Their granules stain orange to bright red, making them easy to distinguish from

  other WBCs. Their numbers increase with parasitic infections and allergies.
• Monocytes make up 4% to 8% of the total circulating white blood cells.

  Although monocytes and lymphocytes stain similarly, there are significant differences

  between the two types.
• Monocytes migrate to tissues where

  they become macrophages
• phagocytize (eat) dead

  and dying tissue, microorganisms, and any other foreign matter or debris.
• Lymphocyte cells are fairly common in circulating blood, making

  up 20% to 50% of the total WBCs. Although and monocytes stain

  similarly, they are smaller and have less cytoplasm. Two of the subclasses

  of are B cells and T cells. Although they look alike, they have different

  immune system functions.
• Thrombocytes These formed elements are commonly called platelets, a term that

  may be used interchangeably with thrombocytes. Platelets are not actually cells but

  cell fragments. Together, platelets and leukocytes make up approximately 1% of whole

  blood, but platelets outnumber leukocytes.
• Platelets secrete vasoconstrictors (chemicals that reduce the size of broken blood

  vessels) to slow the flow of blood.
• Hematopoiesis is blood production. It is a continual process

  designed to meet the demand of replacing circulating cells that have worn out or been

  lost through bleeding.
• hemocytoblast (stem cell) is the starting cell for the production

  of all the formed elements. This cell is said to be pluripotent, which means it can

  become any one of seven different types of formed elements.
• Myeloid hemopoiesis is the production of all the formed elements in the red

  bone marrow.
• Only lymphocytes can also be produced in lymphoid tissues such as

  the lymph nodes, thymus, and spleen.
• additional production in sites outside

  the red bone marrow is lymphoid hemopoiesis.
• Thrombopoiesis is the production of platelets. It begins with

  a hemocytoblast in the red bone marrow. When there is a need for more platelets,

  the liver and kidneys produce a chemical called thrombopoietin. The target tissue

  for thrombopoietin is the hemocytoblast. Thrombopoietin causes the hemocytoblast

  to grow and divide to become a megakaryocyte. The megakaryocyte eventually breaks apart to become many platelets.
• Leukopoiesis is the production of leukocytes, which also begins

  with a hemocytoblast in the red bone marrow. Lymphocytes and

  macrophages out in the tissues produce chemicals called colony-stimulating factors

  (CSFs) when there is a challenge to the immune system.
• Erythropoiesis is erythrocyte production. Erythropoiesis, too, begins

  with a hemocytoblast in red bone marrow. The kidneys produce erythropoietin (EPO)

  to stimulate red blood cell production when the oxygen blood level is low, a condition

  called hypoxemia.
• The cytoplasm of erythrocytes contains hemoglobin, a red, complex protein
• hemoglobin, a red, complex protein made

  of four chains of amino acids called globins.
• Each chain contains a

  heme group with an iron ion at its center that can bind to one oxygen molecule, so

  each hemoglobin molecule can carry four oxygen molecules.
• The liver secretes bilirubin in bile, an important digestive

  juice it is then

  removed from the body with feces.