Questions and Answers
What is the main function of blood in the body?
Red blood cells can replicate themselves.
False
What is the main component of plasma in blood?
water
Red bone marrow produces all types of blood cells, while lymphatic tissue supplements blood cell production mainly by producing __________.
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Match the blood cell with its description:
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What is the primary nutritional requirement for red blood cell formation?
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Which nutrients are essential for red blood cell formation? Select all that apply.
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Sickle cell disease is an inherited blood disorder.
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Red blood cells circulate in the body for about $120$ days before being consumed by ____________.
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What is the term for a state in which the body has an excess of red blood cells?
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Which type of polycythemia results from conditions lowering oxygen levels in the blood?
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Anemia is a deficiency of white blood cells.
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Anemia results from an insufficient supply of ____ in the diet.
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What is the term for an abnormally high white blood cell count?
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Match the granulocyte with its characteristics:
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What type of leukemia involves uncontrolled granulocyte production?
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An increased number of neutrophils indicate a viral infection.
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Platelets play a key role in stopping bleeding through ___.
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Match the following blood clotting terms with their definitions:
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What enzyme is formed in the intrinsic and extrinsic pathways to activate prothrombin?
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What is the end result of both the extrinsic and intrinsic pathways in blood clot formation?
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Smooth endothelium in blood vessels discourages blood clot formation. True or False?
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Vitamin K is absorbed only if _____ is present.
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What does a hematocrit reveal?
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Which of the following white blood cells have the longest lifespan?
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What percentage of the population in the United States has blood type O?
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What antibodies does Type A blood contain?
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Type AB blood has no ______ antibodies.
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Type O blood is considered universal donor blood.
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Which of the following is not part of hemostasis?
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Which substance allows RBCs to transport oxygen?
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When an infecting organism pierces the skin, which of the following WBCs would quickly migrate out of the blood vessels and into the tissues to ingest the foreign invader?
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What substance, carried by each red blood cell, determines blood type?
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What will occur if someone with type A blood receives a transfusion with type B blood?
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Study Notes
Blood Composition
- Blood is a connective tissue made up of several types of cells in combination with a fluid matrix.
- It accounts for 7% of body weight and has a volume of approximately 5 liters in an average adult.
- Blood is composed of two main components: plasma (55% of blood volume) and formed elements (45% of blood volume).
Plasma
- The main component of plasma is water.
- Plasma also contains proteins, nutrients, electrolytes, hormones, and gases.
- Plasma proteins play roles in blood clotting, the immune system, and the regulation of fluid volume.
Formed Elements
- Formed elements include cells and cell fragments.
- The three main types of formed elements are erythrocytes (red blood cells, RBCs), leukocytes (white blood cells, WBCs), and platelets.
- RBCs are the heaviest of the formed elements and account for most of the formed elements.
Blood Cell Formation
- The body continually replaces blood cells that are old or damaged.
- Blood cell formation, or hemopoiesis, occurs in hemopoietic tissues, such as red bone marrow and lymphatic tissue.
- Red bone marrow produces all types of blood cells, while lymphatic tissue produces lymphocytes.
Red Blood Cells
- RBCs are critical for delivering oxygen to cells and removing carbon dioxide.
- A normal RBC is shaped like a disc with a sunken center, allowing for a large surface area for oxygen and carbon dioxide diffusion.
- RBCs lose almost all of their organelles during development and cannot replicate themselves.
- Hemoglobin, a red pigment, fills over a third of the interior of a RBC and gives blood its color.
- Hemoglobin consists of four ribbon-like protein chains called globins, each bound to an iron-containing molecule called heme.
Hematocrit, Hemoglobin, and RBC Count
- Hematocrit is the percentage of cells in a sample of blood.
- Hemoglobin concentration is the amount of hemoglobin in the blood.
- RBC count is the number of RBCs in a sample of blood.
- Normal values for these measurements vary between men and women.
Sickle Cell Disease
- Sickle cell disease is an inherited blood disorder involving hemoglobin.
- Affected RBCs are stiff and distorted, causing them to clump together and block small blood vessels.
- This deprives tissues of necessary oxygen, resulting in intense pain.
Life Cycle of Red Blood Cells
- RBCs circulate for about 120 days before they die and are consumed by phagocytic cells in the spleen and liver.
- The body must constantly produce new RBCs to maintain homeostasis.
- The process of producing new erythrocytes, or erythropoiesis, is maintained through a negative feedback loop involving the kidneys and the hormone erythropoietin (EPO).### Maintenance of the Body
- Macrophages in the liver and spleen ingest and destroy old RBCs, breaking down hemoglobin into globin and heme.
- Globin is further broken down into amino acids, which are used for energy or to create new proteins.
- Heme is broken down into iron and bilirubin, with iron being transported to the bone marrow to create new hemoglobin and bilirubin being excreted into the intestines as part of bile.
- Bilirubin gives feces its brown color and urochrome, another pigment, gives urine its yellow color.
Jaundice
- Jaundice occurs when the destruction of RBCs becomes excessive, causing bilirubin to accumulate in the tissues and giving the skin and sclera a yellowish hue.
- Jaundice can also result from liver disease or bile duct obstruction that interferes with the flow of bile into the intestines.
- Newborns may develop jaundice shortly after birth due to their immature livers taking time to clear bilirubin from the blood.
Polycythemia
- Polycythemia is a state where the body has an excess of RBCs, resulting in an imbalance.
- Causes of polycythemia include an abnormality in the red bone marrow, such as cancer, and the body's attempt to compensate for conditions that have caused a decrease in oxygen levels in the blood.
- Symptoms of polycythemia include headache, ruddiness, and itchiness, and if left unchecked, can lead to complications such as high blood pressure, blood clots, and heart failure.
Anemia
- Anemia is a deficiency of RBCs or hemoglobin, resulting in a decrease in the oxygen-carrying capacity of the blood.
- Causes of anemia include a loss of RBCs, excessive destruction of RBCs, an insufficient supply of iron in the diet, and a lack of vitamin B12 or the hormone erythropoietin (EPO).
- Symptoms of anemia include fatigue, pallor, and shortness of breath, and may also lead to a faster heart rate and lower blood pressure.
White Blood Cells
- White blood cells (WBCs) or leukocytes are the body's line of defense against infection, with five types: neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
- WBCs contain a nucleus and internal structures, and can be classified into two types: granulocytes (with granules) and agranulocytes (without granules).
- Granulocytes include neutrophils, eosinophils, and basophils, which have different functions and characteristics.
- Agranulocytes include lymphocytes and monocytes, which also have different functions and characteristics.
Lymphocytes
- Lymphocytes are responsible for long-term immunity and come in two types: T lymphocytes and B lymphocytes.
- T lymphocytes directly attack infected or cancerous cells, while B lymphocytes produce antibodies against specific antigens.
Monocytes
- Monocytes are highly phagocytic and can engulf large bacteria and viral-infected cells.
- Monocytes migrate into tissues and transform into macrophages, which ingest bacteria, cellular debris, and cancerous cells.
Changes with Aging
- The volume and composition of blood remains relatively constant with age, but abnormal blood values may occur due to disorders in other systems.
- Elderly individuals are more likely to form unwanted blood clots, develop chronic types of leukemia, and develop pernicious anemia due to the atrophy of the stomach mucosa.
Leukemia
- Leukemia is a cancer of the blood or bone marrow, characterized by an extremely high WBC count.
- Types of leukemia include acute and chronic forms, and can be classified based on the type of blood cell affected, such as lymphocytic or myeloid leukemia.### Blood Composition and Function
- Blood is composed of formed elements (WBCs, RBCs, and platelets) and plasma
- Deficiencies in WBCs, RBCs, and platelets can lead to weakened immune system, anemia, and increased risk of bleeding and bruising, respectively
Platelets and Hemostasis
- Platelets are fragments of megakaryocytes and play a key role in stopping bleeding (hemostasis)
- Platelets live for about 7 days
- Hemostasis involves a sequence of events: vascular spasm, formation of a platelet plug, and formation of a blood clot
- Vascular spasm: smooth muscle fibers in the blood vessel wall constrict to slow blood flow
- Formation of a platelet plug: platelets transform into sticky platelets, which stick to the vessel wall and each other, forming a platelet plug
- Platelet plug forms a temporary seal in the vessel wall
Formation of a Blood Clot
- Blood clotting involves a complex series of chemical reactions using clotting factors
- Extrinsic pathway: damaged blood vessel and surrounding tissues release clotting factors, leading to a cascade of events
- Intrinsic pathway: clotting factors are activated within the blood, leading to a different cascade of events
- Both pathways result in the formation of factor X, which leads to the formation of a blood clot
- Normal clotting requires adequate blood levels of calcium
Blood Clotting Process
- Prothrombin activator acts on prothrombin (factor II) to form thrombin
- Thrombin transforms fibrinogen into fine threads of fibrin, which form a web at the site of injury
- Red blood cells and platelets flowing through the web become ensnared, creating a clot
Fibrinolysis
- The blood clotting process doesn't stop with the formation of the clot
- Platelets trapped within the fibrin web contract, pulling the edges of the damaged vessel closer together
- Later, an inactive plasma protein (plasminogen) is converted into plasmin, which dissolves the fibrin meshwork, and the clot breaks up
Prevention of Blood Clots
- Smooth endothelium: the inner lining of undamaged blood vessels helps prevent platelets from sticking
- Blood flow: the blood normally produces small amounts of thrombin, which is diluted by normal blood flow
- Anticoagulants: basophils and mast cells normally secrete the anticoagulant heparin, which prevents blood clots
Blood Clotting Disorders
- Formation of unwanted blood clots is the most common and serious of clotting disorders
- Unwanted blood clots can lead to sudden death
- Treatment options include heparin and warfarin (Coumadin)
- Hemophilia: a rare disorder resulting from a deficiency of one of the clotting factors, typically factor VIII
Blood Types
- There are four main blood types: A, B, AB, and O
- Blood type is determined by the presence or absence of A and B antigens on the surface of red blood cells
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Test your knowledge of blood cells, their production, and functions. Learn about the components of blood and their roles in the human body.
