CHAPTER 19 BLOOD & BLOOD VESSELS
Red Blood Cells (RBCs)
● Erythrocytes are responsible for gas exchange, primarily oxygen (O2) and carbon dioxide
(CO2).
● Produced in the red bone marrow, RBCs lose their nucleus before entering circulation,
making them anucleated.
● They appear as biconcave disks under a microscope, which increases surface area for gas
exchange.
● Contain hemoglobin, a quaternary protein with four heme groups, each containing an iron
atom (Fe) that binds O2.
● Fully saturated blood has all heme groups filled with O2, while deoxygenated blood may
have one or more heme groups missing O2.
White Blood Cells (WBCs)
● WBCs are divided into two categories: agranular and granular leukocytes.
● Granular leukocytes include neutrophils (most abundant, bilobed nucleus, increase during
infections), eosinophils (rise during parasitic infections), and basophils (least abundant,
release histamines during allergic reactions).
● Agranular leukocytes include monocytes (which differentiate into macrophages) and
lymphocytes (T cells and B cells).
● Each type of WBC plays a unique role in the immune response and defense against
pathogens.
Platelets (Thrombocytes)
● Platelets are not complete cells but fragments of megakaryocytes involved in clotting.
● They store chemicals and vesicles containing clotting factors and enzymes, including
thromboxane A2, which promotes vasoconstriction and platelet aggregation.
● Platelet plug formation involves adhesion to damaged vessels, activation and release of
signaling molecules, and aggregation to form a plug.
Blood Groups and Rh Factor
● Blood group proteins on RBCs include A, B, AB, and O, with AB being an example of
codominance.
● The Rh factor determines whether blood is Rh+ (presence of the factor) or Rh- (absence
of the factor).
● Blood type AB+ is the universal recipient, while O- is the universal donor, able to be
given to any blood type.
, Inflammatory Response and Clotting Mechanisms
Platelet Plug Formation
● Involves a series of steps: adhesion to damaged vessels, activation and release of
signaling molecules, and aggregation to form a plug.
● Platelet adhesion occurs when they stick to collagen fibers in damaged vessels.
● Activated platelets release ADP and thromboxane A2, which activate other platelets and
act as vasoconstrictors.
Blood Clotting Process
● A blood clot consists of insoluble fibrin proteins that trap blood elements, preventing
blood loss.
● Clotting is a cascade of chemical reactions leading to fibrin thread formation.
● Thrombosis occurs when blood clots too easily, while clot retraction pulls damaged
vessel surfaces closer together.
Role of Vitamin K and Aspirin
● Vitamin K is essential for synthesizing clotting factors in the liver but does not directly
form clots.
Red Blood Cells (RBCs)
● Erythrocytes are responsible for gas exchange, primarily oxygen (O2) and carbon dioxide
(CO2).
● Produced in the red bone marrow, RBCs lose their nucleus before entering circulation,
making them anucleated.
● They appear as biconcave disks under a microscope, which increases surface area for gas
exchange.
● Contain hemoglobin, a quaternary protein with four heme groups, each containing an iron
atom (Fe) that binds O2.
● Fully saturated blood has all heme groups filled with O2, while deoxygenated blood may
have one or more heme groups missing O2.
White Blood Cells (WBCs)
● WBCs are divided into two categories: agranular and granular leukocytes.
● Granular leukocytes include neutrophils (most abundant, bilobed nucleus, increase during
infections), eosinophils (rise during parasitic infections), and basophils (least abundant,
release histamines during allergic reactions).
● Agranular leukocytes include monocytes (which differentiate into macrophages) and
lymphocytes (T cells and B cells).
● Each type of WBC plays a unique role in the immune response and defense against
pathogens.
Platelets (Thrombocytes)
● Platelets are not complete cells but fragments of megakaryocytes involved in clotting.
● They store chemicals and vesicles containing clotting factors and enzymes, including
thromboxane A2, which promotes vasoconstriction and platelet aggregation.
● Platelet plug formation involves adhesion to damaged vessels, activation and release of
signaling molecules, and aggregation to form a plug.
Blood Groups and Rh Factor
● Blood group proteins on RBCs include A, B, AB, and O, with AB being an example of
codominance.
● The Rh factor determines whether blood is Rh+ (presence of the factor) or Rh- (absence
of the factor).
● Blood type AB+ is the universal recipient, while O- is the universal donor, able to be
given to any blood type.
, Inflammatory Response and Clotting Mechanisms
Platelet Plug Formation
● Involves a series of steps: adhesion to damaged vessels, activation and release of
signaling molecules, and aggregation to form a plug.
● Platelet adhesion occurs when they stick to collagen fibers in damaged vessels.
● Activated platelets release ADP and thromboxane A2, which activate other platelets and
act as vasoconstrictors.
Blood Clotting Process
● A blood clot consists of insoluble fibrin proteins that trap blood elements, preventing
blood loss.
● Clotting is a cascade of chemical reactions leading to fibrin thread formation.
● Thrombosis occurs when blood clots too easily, while clot retraction pulls damaged
vessel surfaces closer together.
Role of Vitamin K and Aspirin
● Vitamin K is essential for synthesizing clotting factors in the liver but does not directly
form clots.
