Questions and Answers
What is blood?
One of the largest organs distributed throughout the entire body
In a 70kg man, whole blood volume is approximately _____ liters.
5.6
What is the typical pH range of blood?
7.35-7.45
What percentage of blood is composed of plasma?
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What is the primary function of red blood cells (RBCs)?
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Which of the following factors are involved in haemopoiesis?
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The spleen plays no role in the maturation and activation of lymphoid cells.
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What is the lifespan of a red blood cell?
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What happens to senescent RBCs?
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Which of the following terms refers to the production of red blood cells?
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What is myoglobin primarily used for?
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What is the molecular weight of myoglobin?
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Haem is part of the polypeptide chain in haemoglobin.
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What allows red blood cells to transport oxygen efficiently?
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What is the primary site of haemopoiesis in adults?
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Study Notes
Blood Overview
- Blood is a vital organ, comprising approximately 7-8% of total body weight in a 70kg individual, equating to about 5.6 liters.
- Maintains a temperature of 38°C and has a slightly alkaline pH of 7.35-7.45.
Blood Composition
- Plasma constitutes 55% (~3.5L) of blood, containing gases, salts, proteins, carbohydrates, and lipids.
- Formed elements make up 45%, including:
- Erythrocytes (red blood cells) - 99%
- Leukocytes (white blood cells) - <1%
- Platelets - <1%
- Serum is the fluid remaining after blood clots, lacking coagulation factors.
Functions of Blood
- Transports oxygen and nutrients to tissues while carrying waste products, carbon dioxide, hormones, water, solutes, and heat away.
Haemopoiesis
- Refers to the production and development of blood cells, with specific types being:
- Erythropoiesis: red blood cell production
- Leucopoiesis: white blood cell production
- Thrombopoiesis: platelet production
- RBCs outnumber WBCs by over 500 times in circulation.
Sites of Haemopoiesis
- In children, blood cell production occurs in the marrow of long bones; in adults, it shifts to the pelvis, cranium, vertebrae, and sternum.
- The liver, thymus, and spleen can perform blood cell production if necessary (extramedullary haematopoiesis).
- Maturation of lymphoid cells occurs in the spleen and lymph nodes.
Key Features of Haemopoiesis
- A single stem cell can produce over 1 million mature blood cells.
- Stem cells in bone marrow grow, divide, and lose cell adhesion molecules to enter circulation.
- Growth factors essential for haemopoiesis include erythropoietin, colony stimulating factors, interleukins, and thrombopoietin.
Erythropoiesis
- A single proerythroblast can yield about 16 mature red blood cells.
Erythrocytes Characteristics
- Erythrocytes are anucleate with a discoid shape and have a lifespan of approximately 120 days.
- 1% of RBCs are destroyed daily.
- Anaemia is defined by decreased hemoglobin concentration, with reference ranges being 11.5-16.0 g/dL for females and 13.5-17.5 g/dL for males.
- Inherited conditions like G6PD deficiency and sickle cell anaemia lead to haemolytic anaemias.
Life Cycle of RBCs
- RBCs live ~120 days, with senescent cells removed by macrophages.
- Components of hemoglobin are recycled: globin is converted into amino acids, iron is reutilized, and heme is excreted in bile.
Metabolism in RBCs
- RBCs utilize aerobic metabolism for optimal efficiency, requiring oxygen transport to tissues.
- Myoglobin and hemoglobin are specialized proteins facilitating oxygen transport and storage.
Haem Group Importance
- Oxygen binding is facilitated by the haem group, tightly bound to proteins, essential for hemoglobin function.
- The iron component (Fe2+/ferrous) forms part of the haem structure, creating bonds necessary for oxygen binding.
Structure of Myoglobin
- Serves as an oxygen reservoir in heart and skeletal muscle cells.
- The protein comprises 153 amino acids with a molecular weight of 17 kDa, primarily in an α-helix conformation.
- Features 8 helices and is structured with a hydrophilic exterior and a hydrophobic interior, except for specific histidines.
Structure of Hemoglobin
- Similar to myoglobin but facilitates cooperative binding of oxygen, enhancing its efficiency.
Oxygen Binding Sites
- The haem integrates into myoglobin and hemoglobin, playing a crucial role in their oxygen-binding capabilities.
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Description
This quiz explores the fundamental concepts of haematology, including the composition of whole blood and the processes involved in haemopoiesis, focusing on erythropoiesis. It is designed to test your understanding of blood components and their functions, essential for medical and health science students.
