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What role do eosinophils play during allergic reactions?
What role do eosinophils play during allergic reactions?
Where are B lymphocytes processed?
Where are B lymphocytes processed?
What is the definition of hemostasis?
What is the definition of hemostasis?
What condition is characterized by an excessive increase in white blood cells for no apparent reason?
What condition is characterized by an excessive increase in white blood cells for no apparent reason?
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What is the primary function of T lymphocytes?
What is the primary function of T lymphocytes?
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What is the first mechanism of hemostasis after a blood vessel is severed?
What is the first mechanism of hemostasis after a blood vessel is severed?
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What contributes to local myogenic spasm in response to vessel wall trauma?
What contributes to local myogenic spasm in response to vessel wall trauma?
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What role do platelets play in vascular constriction following vessel injury?
What role do platelets play in vascular constriction following vessel injury?
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Which of these is NOT a factor in achieving hemostasis?
Which of these is NOT a factor in achieving hemostasis?
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How long can the vascular spasm last after a vessel injury?
How long can the vascular spasm last after a vessel injury?
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What is the average blood volume in a normal adult?
What is the average blood volume in a normal adult?
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What color is arterial blood due to the presence of oxyhemoglobin?
What color is arterial blood due to the presence of oxyhemoglobin?
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Which component of blood is responsible for transporting oxygen?
Which component of blood is responsible for transporting oxygen?
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Which of the following is NOT a function of blood?
Which of the following is NOT a function of blood?
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Which of the following contributes to the ionic composition of plasma?
Which of the following contributes to the ionic composition of plasma?
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What is the primary role of white blood cells in the blood?
What is the primary role of white blood cells in the blood?
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What is the primary component of plasma?
What is the primary component of plasma?
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Erythropoiesis refers to the production of which blood component?
Erythropoiesis refers to the production of which blood component?
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What is the first step in the process of blood hemostasis?
What is the first step in the process of blood hemostasis?
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Which factor is not required for the formation of a platelet plug?
Which factor is not required for the formation of a platelet plug?
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During coagulation, what does prothrombin convert into?
During coagulation, what does prothrombin convert into?
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What process strengthens the temporary platelet plug during hemostasis?
What process strengthens the temporary platelet plug during hemostasis?
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Which factor is NOT involved in the vascular spasms during blood hemostasis?
Which factor is NOT involved in the vascular spasms during blood hemostasis?
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What is the origin of platelets?
What is the origin of platelets?
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Which of the following is a required factor for the formation of prothrombinase?
Which of the following is a required factor for the formation of prothrombinase?
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What is the eventual outcome of the clot formed during hemostasis?
What is the eventual outcome of the clot formed during hemostasis?
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What is the diameter range of megakaryocytes?
What is the diameter range of megakaryocytes?
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What is the action of Warfarin in the body?
What is the action of Warfarin in the body?
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Where are platelets primarily destroyed in the body?
Where are platelets primarily destroyed in the body?
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How does EDTA help prevent clotting?
How does EDTA help prevent clotting?
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What is the typical survival time for platelets?
What is the typical survival time for platelets?
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Which component serves as an adhesion bridge between collagen and the glycoprotein platelet receptor?
Which component serves as an adhesion bridge between collagen and the glycoprotein platelet receptor?
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What role does antithrombin III play in the blood?
What role does antithrombin III play in the blood?
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What happens to prostacyclin production when endothelial cells are damaged?
What happens to prostacyclin production when endothelial cells are damaged?
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What is one of the contractile proteins found in platelets?
What is one of the contractile proteins found in platelets?
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What happens during the formation of a platelet plug?
What happens during the formation of a platelet plug?
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What effect does nitric oxide (NO) have on platelet aggregation?
What effect does nitric oxide (NO) have on platelet aggregation?
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Which factor is activated by the complex of thrombomodulin and thrombin?
Which factor is activated by the complex of thrombomodulin and thrombin?
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The normal blood count of platelets ranges between which values?
The normal blood count of platelets ranges between which values?
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What initiates the intrinsic pathway of clotting when endothelial walls are damaged?
What initiates the intrinsic pathway of clotting when endothelial walls are damaged?
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What is primarily stored within the dense tubular system of platelets?
What is primarily stored within the dense tubular system of platelets?
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What is the function of fibrin fibers during clotting?
What is the function of fibrin fibers during clotting?
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Study Notes
Blood Physiology
- Blood is a connective tissue in fluid form, considered the fluid of life, carrying oxygen from lungs to body parts and carbon dioxide from body parts to lungs.
- Blood is red in color; arterial blood is scarlet red due to hemoglobin and oxygen, while venous blood is purplish red due to increased carbon dioxide.
- Average blood volume in a healthy adult is 5 liters; in a newborn, it is 450 ml.
- Blood volume increases during growth, reaching 5 liters at puberty.
- In females, blood volume is slightly lower, approximately 4.5 liters.
- In a healthy adult weighing 70 kg, blood constitutes about 8% of body weight.
Blood Composition
- Blood consists of cellular components and plasma.
- Cellular components include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
- Plasma is primarily 98% water, containing ions and plasma proteins like albumin, globulin, and fibrinogen.
- Plasma has the same ionic composition as interstitial fluid.
Functions of Blood
- Transport: Blood carries oxygen, carbon dioxide, nutrients, hormones, and waste products.
- Homeostasis: Blood regulates body temperature and extracellular fluid (ECF) pH.
- Protection: White blood cells and antibodies protect against infections.
- Blood clotting: Prevents blood loss.
Blood Cells Formation
- Erythropoiesis: Formation of red blood cells (RBCs).
- Leucopoiesis: Formation of white blood cells (WBCs).
- Thrombopoiesis: Formation of platelets.
Hematopoiesis
- Hematopoiesis is the production of blood cells.
- In utero, RBCs are initially produced in the yolk sac, then in the liver and spleen during the middle trimester, and lastly in the bone marrow of all bones during the last few months of pregnancy.
- After birth, red bone marrow in flat bones continues to produce RBCs throughout life.
- In adults, bone marrow in the axial skeleton, pelvic and pectoral girdles, and proximal epiphyses of the humerus and femur are the primary sites of RBC production.
Production of RBCs
- In utero, bone marrow appears in the 30th to 36th weeks.
- Bone marrow is the primary site of RBC formation after birth.
Hematopoiesis
- Hematopoiesis commences during early embryonic life and continues throughout life.
- Yolk sac, liver, spleen, and bone marrow are the sites of hematopoiesis at different stages of development.
Hematopoiesis Chart
- This chart displays the relative contribution of different organs (liver, spleen, bone marrow) to RBC production at various fetal and postnatal stages.
- Bone marrow becomes the primary location throughout postnatal development and adulthood.
Active Bone Marrow Locations
- In adults, red bone marrow is mainly found in axial skeleton, pelvic and pectoral girdles, and proximal epiphyses of the humerus and femur.
Normal Bone Marrow Conversion
- During childhood, red marrow gradually converts to yellow marrow.
- In adults, yellow marrow occupies the shaft of long bones, whereas red marrow occupies the flat bones.
Bone Marrow
- Red bone marrow: Active bone marrow.
- Yellow bone marrow: Inactive bone marrow.
- Proportion of red and yellow marrow varies based on age and location within the skeletal system.
Blood Composition Ratios
- Plasma constitutes approximately 55% of whole blood volume.
- Cellular elements (RBCs, WBCs, platelets) make up the remaining 45%.
Composition of Whole Blood
-
Plasma: 46-63%
-
Formed elements (cells): 37-54%
-
Platelets: 0.1%
-
White blood cells: 0.001%
-
Red blood cells: >99.9%
Characteristics of RBCs
- Biconcave discs: 7.5 µm in diameter
- Flexible cell membranes
- Lack mitochondria, ribosomes, and RNA
- Use anaerobic glycolysis
- 120-day lifespan
- Normal range: 4.7-5.2 million/mm³
- Normal hemoglobin (Hb): 14-16 g/dL
Red Blood Cells (RBC) Function
- Transport oxygen.
- Transport carbon dioxide.
- Buffer
Genesis (Production) of RBC
- All blood cells develop from pluripotent hematopoietic stem cells that differentiate into committed cells.
- Committed stem cells are specific for RBCs, WBCs, and other blood cells.
- Growth of different stem cells is regulated by specific growth factors.
Stages of Differentiation of RBC
- Stages of RBC development involve committed stem cells, proerythroblast, basophilic erythroblast, polychromatophilic erythroblast, orthochromatic erythroblast, reticulocytes, and mature erythrocytes.
Erythropoiesis
- RBC development is characterized by a decrease in cell size, nucleus disappearance, and hemoglobin (Hb) appearance.
Regulation of RBC Production
- Erythropoiesis is stimulated by the hormone erythropoietin, produced by the kidney in response to low blood oxygen levels (hypoxia).
- Hypoxia is caused by low RBC count, hemorrhage, high altitude, prolonged heart failure, and lung disease.
- Kidneys produce erythropoietin when tissue oxygenation decreases.
Erythropoietin Formation
- Erythropoietin is primarily synthesized by fibroblasts in the renal cortex and outer medulla.
- Hypoxia in renal tissue leads to increased levels of hypoxia-inducible factor-1 (HIF-1).
- Norepinephrine, epinephrine, and various prostaglandins stimulate erythropoietin production.
Hemoglobin
- Adult hemoglobin (HbA) has two alpha and two beta globin chains, each associated with a heme group.
- Hemoglobin structure accounts for its oxygen-carrying capacity.
- Hemoglobin consists of four protein globin chains, each centered around a heme groups.
- Each heme group consists of a porphyrin ring with an iron atom in the center.
- Adult hemoglobin usually has two alpha and two beta chains.
Iron Metabolism
- Iron is a crucial component of hemoglobin, myoglobin, and other structures.
- Sixty-five percent of total iron is in hemoglobin.
- Four percent is in myoglobin.
- One percent is in various heme compounds.
- 0.1% is in the plasma combined with transferrin.
- Between 15 and 30 % is stored in the liver as ferritin.
Extravascular Pathway for RBC Destruction
- Old, damaged RBCs are phagocytosed in the liver, spleen, and red bone marrow.
- Hemoglobin is broken down into globin and heme.
- Globin is broken down into amino acids, which are recycled.
- Heme is converted to bilirubin, which is transported to the liver for processing and excretion in the bile.
- Iron is released and reused in erythropoiesis.
Bilirubin Metabolism
- Bilirubin metabolism involves the breakdown of heme, the conversion to bilirubin, conjugation with glucuronic acid in the liver, and excretion in the bile.
- Bilirubin is transported in the blood bound to albumin.
- Unconjugated bilirubin is converted to conjugated bilirubin in the liver.
- Conjugated bilirubin is then excreted in the bile into the gut and then in faeces as stercobilin.
Jaundice
- Elevated bilirubin levels (hyperbilirubinemia) cause jaundice.
- Prehepatic jaundice arises from excessive RBC breakdown.
- Intrahepatic jaundice arises from liver dysfunction with bilirubin conjugation problems.
- Posthepatic jaundice arises from biliary obstruction.
Types of Jaundice
-
Prehepatic: Excessive erythrocyte destruction exceeds liver's conjugation capacity, leading to unconjugated hyperbilirubinemia.
-
Intrahepatic: Liver dysfunction impairing bilirubin conjugation, resulting in conjugated hyperbilirubinemia.
-
Posthepatic: Obstruction of bile ducts preventing excretion of conjugated bilirubin, ultimately leading to conjugated hyperbilirubinemia.
Normal Bilirubin Metabolism
- Unconjugated bilirubin is transported in the blood bound to albumin.
- In the liver, unconjugated bilirubin is conjugated to glucuronic acid, making it water-soluble.
- Conjugated bilirubin is secreted into bile.
- In the intestines, urobilinogen is formed from conjugated bilirubin.
- Some urobilinogen is reabsorbed into the bloodstream and excreted through urine; most is converted to stercobilin and excreted in feces.
Prehepatic (Hemolytic) Jaundice
- Results from excess erythrocyte destruction beyond the liver's capacity to conjugate bilirubin, leading to unconjugated hyperbilirubinemia.
- This jaundice often results from autoimmune diseases, hemolytic disorders (like Rh incompatibility), abnormal RBCs, and extravascular hemolysis.
- Characterized by an elevated concentration of unconjugated bilirubin in the blood.
Intrahepatic Jaundice
- Results from dysfunction of liver cells interfering with uptake, conjugation, and/or secretion of bilirubin, leading to conjugated or unconjugated hyperbilirubinemia.
- Associated with generalized liver problems.
- In this case, hyperbilirubinemia often accompanies other abnormalities in biochemical markers of liver function.
Posthepatic Jaundice
- Arises from obstruction of the biliary tree, preventing conjugated bilirubin from entering the intestines.
- Characterized by pale stools (lack of stercobilin) and dark urine (excess conjugated bilirubin).
Neonatal Jaundice
- Common, especially in premature infants.
- Usually transient, resolving within the first 10 days.
- High bilirubin levels can be treated.
Blood Film
- Blood film is a microscopic examination of blood, used to visualize blood components.
- Staining techniques highlight different cell types, facilitating identification.
White Blood Cells (WBCs)
- Mobile units of the body's protective system.
- Normal count: 4,000-11,000 /µL.
- Types:
- Granulocytes: neutrophils (60%), eosinophils (2%), basophils (0.4%).
- Agranulocytes: lymphocytes (30%), monocytes (5%).
Neutrophils and Macrophages
- Defend against infections.
- Neutrophils are mature cells; they can attack and destroy bacteria while circulating in blood and within tissues.
Neutrophil Development
- Neutrophils go through these stages of development in the bone marrow: myeloblast, promyelocyte, myelocyte, metamyelocyte, band neutrophil, and mature neutrophil.
- Mature neutrophils are characterized by a segmented nucleus.
Phagocytosis
- Definition: Cellular ingestion of offending agents.
- Most important function of neutrophils and macrophages.
- Process of phagocytosis involves adherence, engulfment, and killing of foreign particles.
Monocytes
- Bean-shaped nucleus.
- Immature in blood (1-2 days).
- In tissues, mature to macrophages (tissue macrophages),
- Increased phagocytosis than neutrophils.
- Survive for months after phagocytosis.
WBC Mechanisms
- Diapedesis: WBCs squeezing through capillary pores to enter tissues.
- Chemotaxis: WBCs moving towards the site of infection by chemical signals.
Basophils
- Similar to mast cells outside capillaries in connective tissue.
- Release heparin into the blood, preventing blood coagulation.
- Involved in allergic reactions; release histamine, causing vascular and tissue reactions.
Eosinophils
- They attach themselves to the surface of parasites and release substances that kill them.
- Important in allergic reactions.
- Help prevent spread of inflammatory process.
Lymphocytes
- Responsible for acquired immunity.
- Present in lymph nodes and other lymphatic tissues.
- Types:
- B lymphocytes: Processed in bone marrow, produce antibodies upon antigen exposure.
- T lymphocytes: Processed in the thymus; destroy cells (e.g., virus-infected cells and cancer cells) by releasing specific chemicals.
Leukemia
- An excessive increase in white blood cells (WBCs) for no apparent reason.
Hemostasis and Blood Coagulation
- Hemostasis: Prevention of blood loss.
- Three main mechanisms:
- Vascular constriction
- Platelet plug formation
- Blood clot formation
Vascular Constriction
- Immediate after blood vessel damage, smooth muscle in the vessel wall contracts.
- This reduces blood flow from the ruptured vessel.
Platelet Plug Formation
- Platelets adhere to exposed collagen, releasing platelet factors.
- This makes nearby platelets sticky, leading to platelet aggregation.
Blood Clot Formation
- Prothrombin activator is formed as a result of blood vessel disruption.
- Prothrombin activator, in the presence of sufficient calcium ions, converts prothrombin to thrombin.
- Thrombin converts fibrinogen to fibrin fibers forming a mesh; this mesh traps red blood cells and platelets to form a clot.
- The clot begins to retract 20-60 mins after forming, tightening the clot.
Coagulation Pathways
- Two main pathways to clot formation:
- Extrinsic pathway: Initiated by trauma to the vascular wall or tissues exposed to blood.
- Intrinsic pathway: Initiated by trauma to the blood or exposure to collagen.
- Both pathways lead to common pathway in forming the clot structure.
Inactivating Blood Clotting
- Blood proteins, like fibrin fibers and antithrombin-heparin cofactor, remove thrombin from blood.
- Heparin-antithrombin III complex inactivates other activated factors XII, XI, X, and IX.
- Clot retraction shortens fibrin fibers; this retraction is caused by contraction of attached platelets.
- Plasmin: A protein that dissolves fibrin fibers and some other coagulants, like fibrinogen, Factor V, Factor VIII, prothrombin, and Factor XII.
Factors Affecting Clot Formation
- Normal coagulation depends on: Normal platelets All clotting factors. Vitamin K Calcium ions Tissue factor (TF).
Conditions Affecting Blood Clotting
- Deficiency in vitamin K Hemophilia Thrombocytopenia
Effects of Drugs on Clotting
- Some drugs affect blood clotting mechanisms. Examples are given.
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Description
Test your knowledge on the functions and components of blood, hemostasis, and the immune response. This quiz covers essential concepts related to white blood cells, lymphocytes, and the processes of allergic reactions and blood clotting. Perfect for students studying human biology and anatomy.
