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Questions and Answers
What condition directly stimulates the release of erythropoietin (EPO)?
What condition directly stimulates the release of erythropoietin (EPO)?
Which of the following conditions would directly stimulate the release of erythropoietin (EPO) by the kidneys?
Which of the following conditions would directly stimulate the release of erythropoietin (EPO) by the kidneys?
Which factor would NOT directly contribute to hypoxia and trigger erythropoietin release?
Which factor would NOT directly contribute to hypoxia and trigger erythropoietin release?
Besides the kidneys, which other organ plays a smaller role in releasing erythropoietin?
Besides the kidneys, which other organ plays a smaller role in releasing erythropoietin?
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The stimulus of hypoxia relating to decreased RBC count, decreased amount of hemoglobin and decreased availability of O2 is meant to maintain what?
The stimulus of hypoxia relating to decreased RBC count, decreased amount of hemoglobin and decreased availability of O2 is meant to maintain what?
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If a patient has a normal RBC count and normal hemoglobin levels, but still experiences hypoxia, what could be a potential cause?
If a patient has a normal RBC count and normal hemoglobin levels, but still experiences hypoxia, what could be a potential cause?
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Which scenario would result in decreased oxygen delivery to the tissues, leading to hypoxia?
Which scenario would result in decreased oxygen delivery to the tissues, leading to hypoxia?
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What is the relationship between homeostatis and stimulus related to erythropoietin?
What is the relationship between homeostatis and stimulus related to erythropoietin?
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Which of the following feedback loops is represented by the regulation of blood oxygen levels via erythropoietin?
Which of the following feedback loops is represented by the regulation of blood oxygen levels via erythropoietin?
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If a patient has a normal red blood cell count but still experiences hypoxia, which of the following could be a potential cause?
If a patient has a normal red blood cell count but still experiences hypoxia, which of the following could be a potential cause?
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What is the primary role of blood capillaries within the circulatory system?
What is the primary role of blood capillaries within the circulatory system?
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How would the hematocrit levels of a healthy adult male and female compare?
How would the hematocrit levels of a healthy adult male and female compare?
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If a patient has a low erythrocyte count, which of the following conditions is most likely?
If a patient has a low erythrocyte count, which of the following conditions is most likely?
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What is the correct order of blood flow?
What is the correct order of blood flow?
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Upon centrifuging a tube of blood, three distinct layers are observed. What components are primarily found in the Buffy coat layer?
Upon centrifuging a tube of blood, three distinct layers are observed. What components are primarily found in the Buffy coat layer?
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What is the primary role of erythropoietin in maintaining homeostasis?
What is the primary role of erythropoietin in maintaining homeostasis?
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Which of the following conditions would most likely trigger the release of erythropoietin?
Which of the following conditions would most likely trigger the release of erythropoietin?
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If a patient has kidney damage and reduced erythropoietin production, which of the following would likely occur?
If a patient has kidney damage and reduced erythropoietin production, which of the following would likely occur?
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Besides the kidney, which other organ plays a role (to a smaller extent) in the release of erythropoietin?
Besides the kidney, which other organ plays a role (to a smaller extent) in the release of erythropoietin?
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Which is NOT a stimulus for erythropoietin release?
Which is NOT a stimulus for erythropoietin release?
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What is the primary stimulus that triggers the release of erythropoietin (EPO) by the kidneys?
What is the primary stimulus that triggers the release of erythropoietin (EPO) by the kidneys?
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How does erythropoietin (EPO) primarily contribute to restoring normal blood oxygen levels?
How does erythropoietin (EPO) primarily contribute to restoring normal blood oxygen levels?
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Which of the following conditions would directly lead to the release of erythropoietin (EPO)?
Which of the following conditions would directly lead to the release of erythropoietin (EPO)?
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Besides the kidneys, which other organ plays a role in releasing erythropoietin (EPO), although to a smaller extent?
Besides the kidneys, which other organ plays a role in releasing erythropoietin (EPO), although to a smaller extent?
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What is the relationship between decreased RBC count, erythropoietin release, and homeostasis?
What is the relationship between decreased RBC count, erythropoietin release, and homeostasis?
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A patient presents with fatigue, pallor, and shortness of breath. Lab results indicate abnormally low blood O2 levels. What condition is MOST likely indicated by these findings?
A patient presents with fatigue, pallor, and shortness of breath. Lab results indicate abnormally low blood O2 levels. What condition is MOST likely indicated by these findings?
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Which of the following is NOT a primary cause of anemia?
Which of the following is NOT a primary cause of anemia?
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A patient has been experiencing persistent, slight blood loss due to a bleeding ulcer. What type of anemia is MOST likely to develop as a result?
A patient has been experiencing persistent, slight blood loss due to a bleeding ulcer. What type of anemia is MOST likely to develop as a result?
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Which of the following is a characteristic of iron-deficiency anemia?
Which of the following is a characteristic of iron-deficiency anemia?
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A patient's stomach mucosa is destroyed by an autoimmune disease, leading to a deficiency in intrinsic factor. This MOST likely results in which type of anemia?
A patient's stomach mucosa is destroyed by an autoimmune disease, leading to a deficiency in intrinsic factor. This MOST likely results in which type of anemia?
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Synthetic erythropoietin (EPO) is used to treat which type of anemia?
Synthetic erythropoietin (EPO) is used to treat which type of anemia?
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Aplastic anemia is characterized by which of the following?
Aplastic anemia is characterized by which of the following?
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Which of the following mechanisms is the MOST common cause of hemolytic anemia?
Which of the following mechanisms is the MOST common cause of hemolytic anemia?
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What is the underlying genetic defect in thalassemias?
What is the underlying genetic defect in thalassemias?
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In sickle-cell anemia, what causes RBCs to assume a crescent shape?
In sickle-cell anemia, what causes RBCs to assume a crescent shape?
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Flashcards
Blood Composition
Blood Composition
Fluid connective tissue made of plasma and formed elements.
Plasma
Plasma
The non-living fluid matrix of blood, comprising about 55% of blood volume.
Formed Elements
Formed Elements
Living blood cells suspended in plasma, including RBCs, WBCs, and platelets.
Hematocrit
Hematocrit
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Blood Circulation
Blood Circulation
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Homeostasis
Homeostasis
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Hypoxia
Hypoxia
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RBC Count
RBC Count
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Hemoglobin
Hemoglobin
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Erythropoiesis
Erythropoiesis
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Red Bone Marrow
Red Bone Marrow
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Causes of Hypoxia
Causes of Hypoxia
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Stimulus for Erythropoiesis
Stimulus for Erythropoiesis
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Anemia
Anemia
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Hemorrhagic Anemia
Hemorrhagic Anemia
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Chronic Hemorrhagic Anemia
Chronic Hemorrhagic Anemia
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Iron-Deficiency Anemia
Iron-Deficiency Anemia
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Pernicious Anemia
Pernicious Anemia
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Renal Anemia
Renal Anemia
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Aplastic Anemia
Aplastic Anemia
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Hemolytic Anemias
Hemolytic Anemias
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Sickle-Cell Anemia
Sickle-Cell Anemia
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Thalassemias
Thalassemias
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Study Notes
Chapter 17: Blood
- Blood is a fluid connective tissue with plasma (non-living fluid) and formed elements (living cells)
- Formed elements include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (cell fragments)
- Blood accounts for ~8% of body weight
- Average volume: males ~5-6 Liters, females ~4-5 Liters
- Blood's physical characteristics: sticky, opaque, metallic taste; color varies with oxygen content (high O2 = scarlet, low O2 = dark red); pH 7.35-7.45
Circulation
- Blood exits the heart via arteries
- Arteries branch into capillaries
- Oxygen and nutrients diffuse across capillary walls into organs
- Carbon dioxide and waste from organs enter bloodstream
- Oxygen-deficient blood flows into veins
- Veins return blood to the heart
Blood Composition
- Blood sample spun yields three layers: plasma on top (~55%), erythrocytes on the bottom (~45%), with WBCs and platelets in the Buffy coat (<1%)
- Hematocrit: percent of blood volume occupied by red blood cells; ~47% ± 5% for males, ~42% ± 5% for females
Blood Plasma
- 90% water; over 100 dissolved solutes (nutrients, gases, hormones, wastes, proteins, inorganic ions)
- Plasma proteins (most abundant solutes); remain in blood; produced mostly by the liver
- 60% Albumin; 36% Globulins; 4% Fibrinogen
Formed Elements: Erythrocytes
- Biconcave discs, anucleate, with no organelles
- Diameters larger than some capillaries
- Filled with hemoglobin (Hb) for gas transport
- Contain plasma membrane protein spectrin and other proteins
- Spectrin provides flexibility to change shape; major factor contributing to blood viscosity
- RBC Survival: ~100-120 days
- No protein synthesis, growth, or division after maturation
- Old RBCs become fragile; Hb begins to degenerate
- Get trapped in small circulatory channels, especially the spleen
- Macrophages engulf dying RBCs in spleen
Formed Elements: Erythrocytes
- Structural characteristics (biconcave shape, high surface area to volume ratio, large amount of hemoglobin) contribute to gas transport
- 97% hemoglobin (Hb)
- No mitochondria; ATP production anaerobic
- Superb example of complementarity of structure and function
- RBC function is dedicated to respiratory gas transport; Hb binds reversibly with oxygen
- Normal values: males ~13-18g/100ml, females ~12-16g/100ml
Formed Elements: Erythrocytes - Hemoglobin Structure
- Globin composed of 4 polypeptide chains (2 alpha, 2 beta)
- Heme pigment bonded to each globin chain gives blood its red color
- Heme's central iron atom binds 1 O₂
- Each Hb molecule transports 4 O₂
- Each RBC contains ~250 million Hb Molecules (~1 billion O₂ molecules)
Erythrocyte Formation and Regulation (Erythropoiesis)
- Formation in red bone marrow
- Composed of reticular connective tissue and blood sinusoids
- Primarily in axial skeleton, girdles, and proximal epiphyses of humerus and femur
- Hematopoietic stem cells (hemocytoblasts) give rise to all formed elements
- Hormones and growth factors direct development
- Erythropoiesis: 15-day proerythroblast to reticulocyte to mature RBC development
- Regulation primarily controlled by the hormone erythropoietin (EPO) from the kidneys. High RBC or O₂ levels will depress production
Dietary Requirements for Erythropoiesis
- Essential nutrients include amino acids, lipids, carbohydrates, and iron
- Iron is 65% in hemoglobin; rest found in liver, spleen, and bone marrow
- Stored in cells as ferritin or hemosiderin
- Transported in blood bound to transferrin
- Vitamin B12 and folic acid necessary for DNA synthesis
Fate and Destruction of Erythrocytes
- Life span: 100-120 days
- Old RBCs become fragile; hemoglobin begins to degenerate
- Get trapped in smaller circulatory channels, especially the spleen
- Hemoglobin is broken down
- Macrophages in spleen engulf and recycle them
- Heme and globin are separated, with iron salvaged for reuse and heme degraded to bilirubin
- Bilirubin is secreted into intestines as bile
- Pigment leaves as stercobilin in feces; globin metabolized into amino acids and released into circulation
Erythrocyte Disorders
- Anemia: blood has abnormally low oxygen-carrying capacity; signs of fatigue, pallor, shortness of breath, and chills
- Causes: blood loss (hemorrhagic anemia - rapid blood loss, treated with blood replacement or chronic hemorrhagic anemia- persistent but slight blood loss), low RBC production (iron-deficiency, pernicious anemia - autoimmune disease destroys stomach mucosa; lack of intrinsic needed to absorb B12; treated with B12 injections or nasal gel, or renal anemia - lack of EPO), and high RBC destruction (hemolytic anemias, thalassemia, sickle-cell anemia)
Leukocytes (White Blood Cells)
- Make up <1% of total blood volume (4,800-10,800 WBCs/µl blood)
- Function in defense against disease; leave capillaries via diapedesis and move through tissue spaces by ameboid motion and positive chemotaxis
- Types: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes)
Leukocytes: Granulocytes
- Larger and shorter-lived than RBCs.
- Lobed nuclei; cytoplasmic granules stain specifically with Wright's stain.
- All phagocytic (to some degree)
Granulocytes: Neutrophils
- Most numerous WBC.
- Also called polymorphonuclear leukocytes (PMNs or polys).
- Granules stain lilac; contain hydrolytic enzymes or defensins.
- 3-6 lobes in nucleus; twice the size of RBCs.
- Very phagocytic ("bacteria slayers")
Granulocytes: Eosinophils
- Red-staining granules
- Bilobed nucleus
- Granules lysosome-like
- Release enzymes to digest parasitic worms
- Role in allergies and asthma, modulating immune response
Granulocytes: Basophils
- Rarest WBC; nucleus deep purple with 1-2 constrictions
- Large, purplish-black (basophilic) granules containing histamine
- Histamine is an inflammatory chemical that acts as a vasodilator, attracting WBCs to inflamed sites
- Are functionally similar to mast cells
Agranulocytes
- Lack visible cytoplasmic granules.
- Have spherical or kidney-shaped nuclei.
- Types include lymphocytes and monocytes
Agranulocytes: Lymphocytes
- Second most numerous WBCs in normal blood.
- Large, dark-purple, circular nuclei with thin rim of blue cytoplasm
- Mostly in lymphoid tissue (e.g., lymph nodes, spleen); few circulate in blood
- Crucial to immunity
- Two types: T cells (act against virus-infected cells and tumor cells) and B cells (give rise to plasma cells that produce antibodies)
- Relatively long-lived
Agranulocytes: Monocytes
- Largest leukocytes.
- Abundant pale-blue cytoplasm.
- Dark purple-staining, U- or kidney-shaped nuclei.
- Leave circulation, enter tissues, and differentiate into macrophages.
- Phagocytic cells crucial against viruses, intracellular bacterial parasites, and chronic infections.
- Activate lymphocytes to mount an immune response
Leukocyte Formation (Leukopoiesis)
- Production of WBCs, stimulated by chemical messengers from red bone marrow and mature WBCs. (Interleukins (ILs) and Colony-Stimulating Factors (CSFs))
- All leukocytes originate from hemocytoblasts.
- Lymphocytes: from lymphoid stem cells
- Granulocytes and monocytes: from myeloid stem cells
Platelets
- Cytoplasmic fragments of megakaryocytes.
- Blue-staining outer region; purple granules.
- Granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)
- Act in clotting process; ~150,000 – 400,000 platelets /ml of blood
- Form temporary platelet plugs that help seal breaks in blood vessels.
- Circulating platelets kept inactive and mobile by nitric oxide (NO) and prostacyclin from endothelial cells lining blood vessels.
- Age quickly and degenerate in about 10 days.
- Thrombopoietin regulates platelet formation, deriving from megakaryoblasts via mitosis but no cytokinesis
- Large cells with multilobed nuclei.
Hemostasis
- Fast series of reactions for stopping bleeding
- Requires clotting factors and substances released by platelets and injured tissues
- Three steps: vascular spasm, platelet plug formation, and coagulation (blood clotting)
Hemostasis: Vascular Spasm
- Vasoconstriction of damaged blood vessel
- Triggeers: direct injury to vascular smooth muscle, chemicals released by endothelial cells and platelets, pain reflexes
- Most effective in smaller blood vessels
Hemostasis: Platelet Plug Formation
- Positive feedback cycle
- Exposed collagen fibers trigger platelets to stick to the damaged site via von Willebrand factor
- Platelets swell, become spiked and sticky, and release chemical messengers (ADP)
- ADP causes nearby platelets to stick and release their contents
- Serotonin and thromboxane A2 enhance vascular spasm and platelet aggregation
Hemostasis: Coagulation (Blood Clotting)
- Reinforces platelet plug with fibrin threads
- Blood transformed from liquid to gel by reactions of clotting factors (procoagulants)
- Most plasma proteins are involved; Vitamin K essential for synthesis.
- Three phases: (1.) prothrombin activator formed in intrinsic and extrinsic pathways triggered by tissue-damaging events, (2.) prothrombin to thrombin, (3.) fibrinogen to fibrin mesh
Coagulation Phase 3: Common Pathway to the Fibrin Mesh
- Thrombin converts soluble fibrinogen to fibrin
- Fibrin strands form structural basis of clot
- Fibrin causes plasma to become a gel-like trap for formed elements
- Thrombin activates factor XIII, which cross-links fibrin and strengthens clot formation
Clot Retraction
- Actin and myosin in platelets contract within 30-60 minutes.
- Pulls on fibrin strands, squeezing serum from clot.
- Draws ruptured blood vessel edges together
Vessel Repair
- Platelet-derived growth factor (PDGF) stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall.
- Vascular endothelial growth factor (VEGF) stimulates endothelial cells to multiply and restore endothelial lining
Fibrinolysis
- Removes unnecessary clots after healing.
- Begins within two days; continues for several days.
- Plasminogen in clot is converted to plasmin by tissue plasminogen activator (tPA), factor XII, and thrombin.
- Plasmin is a fibrin-digesting enzyme.
Factors Limiting Clot Growth
- Swift removal and dilution of clotting factors
- Inhibition of activated clotting factors
- Thrombin bound onto fibrin threads
- Antithrombin III inactivates unbound thrombin
- Heparin in basophils and mast cells inhibits thrombin by enhancing antithrombin III
Factors Preventing Undesirable Clotting
- Platelet adhesion is prevented by smooth endothelium, antithrombic substances (like nitric oxide and prostacyclin), and anticoagulants (like Vitamin E quinone).
Disorders of Hemostasis
- Thromboembolic disorders: undesirable clot formation (thrombus and embolism).
- Bleeding disorders: abnormalities preventing normal clot formation (thrombocytopenia, impaired liver function, hemophilia).
- Disseminated intravascular coagulation (DIC): clotting causes bleeding (widespread clotting blocks vessels).
Transfusions
- Whole-blood transfusions used when rapid, substantial blood loss.
- Packed red cells with plasma and WBCs removed used to restore oxygen-carrying capacity
- Transfusion of incompatible blood can be fatal.
Human Blood Groups
- RBC membranes bear 30 types of glycoprotein antigens.
- Anything perceived as foreign by the recipient generates an immune response.
- Promoters of agglutination are called agglutinogens
- Mismatched transfused blood is perceived as foreign, can clump and destroy RBCs; can be fatal
- Presence/absence of antigens used to classify blood cells into different groups (like ABO or Rh).
ABO Blood Groups
- Based on presence/absence of agglutinogens (A and B) on RBCs.
- Blood may contain preformed anti-A or anti-B antibodies (agglutinins). Antibodies against antigens not present on the recipient's RBCs will cause agglutination and destruction
- Anti-A or anti-B typically form in the blood by 2 months old, and reach adult levels by 8-10 months.
Rh Blood Groups
- 52 named Rh agglutinogens (Rh factors); C, D, and E are most common.
- Rh+ indicates presence of D antigen – ~85% of Americans are Rh+.
- Anti-Rh antibodies are not normally formed in Rh- individuals. However, they form if an Rh- individual receives Rh+ blood or an Rh- mother carries an Rh+ fetus
- Second exposure to Rh+ blood can lead to a typical transfusion reaction
Hemolytic Disease of the Newborn
- Also called Erythroblastosis Fetalis
- Only occurs in Rh- mother with Rh+ fetus; mom exposed to Rh+ blood during first delivery – mom then generates anti-Rh antibodies.
- Second pregnancy: Mom's antibodies cross the placenta and destroy RBCs of Rh+ baby.
- Treated with prebirth transfusions and postbirth exchange transfusions
- RhoGAM (anti-Rh) can prevent sensitization in Rh- mother
Transfusion Reactions
- Occur if mismatched blood infused, attacking the recipient's cells. Donor's cells are attacked by recipient's plasma agglutinins, agglutinate and clog small vessels; rupture and release hemoglobin into bloodstream; Diminished oxygen-carrying capacity, diminished blood flow, hemoglobin in kidney tubules, renal failure
- Symptoms: Fever, chills, low blood pressure, rapid heartbeat, nausea, vomiting
- Treatment: Prevent kidney damage (fluids and diuretics)
Restoring Blood Volume
- Death can occur from shock resulting from low blood volume.
- Volume must be replaced immediately with normal saline or multiple-electrolyte solutions that mimics plasma electrolyte composition and osmotic properties
- Plasma expanders (purified human serum albumin, hetastarch, dextran) mimic osmotic properties; and can cause complications
Diagnostic Blood Tests
- Hematocrit (test for anemia), Blood glucose tests (diabetes), Microscopic examination of RBCs (reveals variations in size and shape).
- Differential WBC count, Prothrombin time, platelet counts (assess hemostasis), and SMAC (blood chemistry profile) and complete blood count (CBC).
Developmental Aspects
- Fetal blood cells form in yolk sac, liver, and spleen.
- By the 7th month, red bone marrow becomes the primary hematopoietic area.
- Blood cells from mesenchymal cells called 'blood islands'.
- Fetus forms hemoglobin F (higher affinity for O2).
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Description
This quiz explores the physiological mechanisms surrounding erythropoietin (EPO) release in response to hypoxia. Participants will answer questions about the conditions and factors that influence EPO secretion and its role in maintaining homeostasis related to blood oxygen levels. Test your knowledge on how the body responds to low oxygen conditions and the feedback loops involved.
