The percentage of a centrifuged blood sample made up of red blood cells is called the hematocrit.
Missing Word
hematocrit
The hematocrit is the proportion of blood volume occupied by packed red cells after centrifugation. It is a quick measure of red cell levels and falls in anemia.
Category: Blood Composition
Question 2
The cytoskeletal protein spectrin gives the red blood cell membrane the flexibility to bend and squeeze through narrow capillaries.
Missing Word
spectrin
Spectrin is a protein network on the inner surface of the red blood cell membrane. It lets the cell deform as it passes through capillaries narrower than itself and then spring back to its biconcave shape.
Category: Erythrocytes
Question 3
The glycoprotein hormone thrombopoietin, produced mainly by the liver, stimulates megakaryocytes to produce platelets.
Missing Word
thrombopoietin
Thrombopoietin is the growth factor that drives megakaryocyte development and platelet production. Its name combines thrombo, for clot, with poietin, for making.
Category: Formed Element Production
Question 4
Each red blood cell is packed with hemoglobin, the iron-containing protein that binds and transports oxygen.
Missing Word
hemoglobin
Hemoglobin is the oxygen-carrying protein of red blood cells, built from four globin chains that each hold an iron-containing heme group.
Category: Erythrocytes
Question 5
Carbon dioxide bound to amino acids of the globin chains forms the compound carbaminohemoglobin.
Missing Word
carbaminohemoglobin
Carbaminohemoglobin forms when carbon dioxide attaches to the globin portion rather than the iron. It carries a minority of the carbon dioxide, with most traveling in plasma as bicarbonate.
Category: Erythrocytes
Question 6
Iron released from old red blood cells travels through the blood bound to the plasma protein transferrin.
Missing Word
transferrin
Transferrin is the plasma protein that carries iron to the bone marrow and other tissues, where it can be reused to make new heme.
Category: Erythrocytes
Question 7
Intestinal bacteria convert bilirubin to urobilinogen and then to stercobilin, the brown pigment that colors feces.
Missing Word
stercobilin
Stercobilin is the end product of bilirubin breakdown in the intestine, and it gives feces their brown color.
Category: Erythrocytes
Question 8
White blood cells move toward chemical signals released by damaged or infected tissue in a process called chemotaxis.
Missing Word
chemotaxis
Chemotaxis is movement guided by a chemical gradient. Positive chemotaxis draws leukocytes to sites of injury and infection.
Category: Leukocytes and Platelets
Question 9
Basophils release histamine and the anticoagulant heparin.
Missing Word
heparin
Heparin is an anticoagulant that opposes clotting. Basophils release it along with histamine, which promotes inflammation.
Category: Leukocytes and Platelets
Question 10
A cancer in which the bone marrow overproduces abnormal white blood cells that circulate in the blood is called leukemia.
Missing Word
leukemia
Leukemia is a cancer of the blood-forming tissue in which abnormal leukocytes are overproduced. Unlike lymphoma, which collects in lymph nodes and other tissues, it is defined by abnormal cells in the marrow and blood.
Category: Leukocytes and Platelets
Question 11
Platelet plug formation begins when platelets adhere to exposed collagen fibers in the damaged vessel wall.
Missing Word
collagen
Collagen in the vessel wall is normally hidden beneath the endothelium. When the vessel is damaged, exposed collagen gives platelets a surface to stick to, starting the platelet plug.
Category: Hemostasis
Question 12
In the common pathway of coagulation, the enzyme thrombin converts fibrinogen into fibrin.
Missing Word
thrombin
Thrombin is formed from prothrombin by activated factor X. It converts soluble fibrinogen into insoluble fibrin strands that form the clot.
Category: Hemostasis
Question 13
During fibrinolysis, the enzyme plasmin breaks down the fibrin mesh of a clot.
Missing Word
plasmin
Plasmin forms from the inactive plasma protein plasminogen and digests fibrin, dissolving a clot once the vessel has repaired.
Category: Hemostasis
Question 14
A blood clot fragment that breaks loose and travels through the bloodstream is called an embolus.
Missing Word
embolus
An embolus is a traveling clot fragment. If it lodges in a smaller vessel, it can block flow and cause a stroke, heart attack or pulmonary embolism.
Category: Hemostasis
Question 15
The clumping of red blood cells that occurs when antibodies bind to antigens on their surface is called agglutination.
Missing Word
agglutination
Agglutination is the clumping of red cells by antibodies, as happens in a mismatched transfusion. It is the reaction used to determine blood type in the lab.
Category: Blood Typing