The Blood 319
- Plasma is the fluid component of blood; 91% is
water.^
- Seven percent of plasma are the proteins: albumin,
globulin, and fibrinogen.^
- Two percent of plasma are solutes: ions, nutrients,
waste products, gases, enzymes, and hormones.
The Formation of Blood Cells:
Hematopoiesis
- Hematopoiesis occurs in red bone marrow or
myeloid- tissue where all blood cells are
produced.^
- Lymphocytes and monocytes are also produced by
lymph nodes, the spleen, and the tonsils.^
- Blood cells develop from undifferentiated
mesenchymal cells called stem cells or
hematocytoblasts.
The Blood Cell Anatomy
and Functions
- Erythrocytes appear as biconcave disks without a
nucleus. They consist of a protein network or stroma
and the red pigment hemoglobin.^
- Hemoglobin is made of the pigment heme, which has
four iron atoms that combine with oxygen gas in the
lungs, and the protein globin, which combines with
carbon dioxide in tissues.^
- Leukocytes have nuclei and do not have
hemoglobin. The two categories of leukocytes are
the granular leukocytes and the agranular or
nongranular leukocytes. They leave the blood and^
move into body tissues where they combat infection
and inflammation.^
- Neutrophils are the most common granular
leukocytes. They respond to tissue destruction from
bacteria by phagocytizing foreign substances and
destroying bacteria via their enzyme lysozyme.^
- Monocytes are nongranular leukocytes that
phagocytize bacteria and cellular debris. In tissues,
they are called macrophages because they are fairly
large, about 18 μm wide.^
- Eosinophils are granular leukocytes that combat
irritants that cause allergies and parasitic worms.
They produce antihistamines.^
- Basophils are granular leukocytes that are also
involved in allergic reactions. They produce
heparin, histamine, and serotonin.
8. Lymphocytes are nongranular leukocytes that produce
antibodies and are involved in the immune response.
Two common lymphocytes are the T lymphocytes and
the B lymphocytes.^ - Thrombocytes or platelets are very small disk-
shaped, cellular fragments with a nucleus. They
cause the clotting mechanism.
The Clotting Mechanism- A ruptured blood vessel attracts thrombocytes to
the site of injury.^
2.^ The damaged tissues release thromboplastin.^ - Thromboplastin, with the assistance of calcium
ions, proteins, and phospholipids, causes the
production of prothrombin activator.^ - Prothrombin activator with the assistance of calcium
ions causes prothrombin, a plasma protein, to be
converted into thrombin.^ - Thrombin causes soluble fibrinogen, another
plasma protein, to be converted into insoluble
fibrin.^ - Fibrin forms the threads of the clot, which enmesh
the blood cells and platelets seeping from the wound. - Tightening of the clot (clot retraction) or syneresis
occurs and hemorrhaging ceases.^ - After tissues are repaired, dissolution of the clot or
fibrinolysis occurs.^ - Unwanted clotting, caused by masses of cholesterol
known as plaque, in an unbroken blood vessel^
is known as a thrombosis. The clot is called a
thrombus.^ - A piece of a blood clot, transported by the
bloodstream, can get lodged in a vessel and block
off circulation. It is called an embolus and the
condition is called an embolism.
The Blood Groups- The different types of human blood groups must
be matched in a blood transfusion to prevent
agglutination of RBCs.^ - Agglutination is caused by a reaction between protein
antibodies in the blood plasma and surface antigens
on the red blood cell membrane.^ - Agglutination of RBCs will cause headache,
breathing difficulties, pain, and jaundice. Kidneys
may fail.