Lecture 1 Intro to RBCs Flashcards
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What is the function of blood?
- Transport gases, nutrients, hormones and metabolic wastes
- Regulates pH, ions, water
- Restricts fluid loss via blood clotting
- Defends against toxins and pathogens
- Regulates body temp
What is hematocrit?
% of total blood volume occupied by red blood cells (normal 37-54%)
What does plasma consist of?
- Water (92%)
- ions
- organic molecules
- Trace elements and vitamins
- Gases
What proteins are found in plasma?
- Albumins (60%) –> osmotic pressure
- Globulins (35%) –> antibodies
- Fibrinogen (4%) –> fibrin -> blood clotting
What are the cellular elements in blood?
- Erythrocytes: Red Blood Cells
- Leukocytes: White Blood Cells
- Thrombocytes: Platelets
What do RBCs contain?
Hemoglobin and enzymes
How many RBCs are there per microliter of blood?
about 5 million
Describe the structure of a Hemoglobin Molecule
- 2 alpha chains
- 2 beta chains
- 4 heme structures (one in each chain)
- 4 iron atoms (found in the center of each heme)
How many oxygen atoms can each hemoglobin molecule carry?
4 oxygen atoms
Describe RBC production and removal
- Produces and removal same rate
- Rate is 2-3 million per second
What is Erythropoiesis?
- Production of Erythrocytes from hematopoietic precursor cells in the bone marrow
- Requires iron, Vitamin B12 and folate from diet
What is erythropoietin?
- Hormone made in the kidneys which promotes erythropoiesis
- Secreted in response to low oxygen levels
- Secretion leads to an increase in RBC production
What happens when Hypoxia Inducible Factor (HIF1alpha) becomes stable?
- Signals low oxygen
- Activates transcription of erythropoietin gene
- Increases RBC production
- Increases Oxygen Circulation
In bone marrow, what percent of cells develop into erythrocytes and what percent develop into leukocytes?
- 25% erythrocytes
- 75% leukocytes
(more erythrocytes in body than leukocytes, however, leukocytes have a higher production rate)
How are platelets formed?
- Formed by the breakdown of megakaryocytes in the bone marrow to the blood circulation
What is hematopoiesis?
- Process of blood cell formation from occurring in bone marrow
Development of - erythrocytes (RBCs)
- Leukocytes (WBCs)
- Thrombocytes (Platelets)
What regulates hematopoiesis?
Cytokines
What are sites of hematopoiesis?
In Embryo: Yolk sac, Liver, Spleen, Bone marrow
After Birth: Bone marrow
Adults: Pelvis, spine, ribs, cranium, proximal end long bones
How are RBCs removed?
- Degraded by Macrophages
- Iron is recycled for new RBCs and transported to bone marrow by Transferrin
- Heme produces Bilirubin and transported to the liver and excreted in bile
What are causes of Jaundice (hyperbilirubinemia)
- Large release of hemoglobin from degraded RBCs
- High turnover of RBC
- Liver disease
- Bile duct obstruction (pushing bile back into the liver)
What are causes of low RBC production?
- Destruction of stem cells via drugs or radiation
- Inadequate nutrients: iron, folic acid, vitamin B12
- Low erythropoietin (renal)
What causes high removal of RBCs?
- Genetic: defect in RBC proteins (hemoglobin)
- Parasitic infections
- drugs
- Autoimmune reactions
- Hemorrhagic (excessive blood loss)
What is Polycythemia?
- Hematocrit is too high (too many RBCs)
- Caused by abnormal erythrocyte precursors
- Low oxygen delivery to tissues
