March 13 Flashcards
Before the 17th century, what was the key to restoring health if someone was unhealthy?
- Lifestyle (diet & exercise)
- Medication (herbs)
What principle guided treatments in pre-17th century medicine?
“Opposites cure opposites” (e.g. a cold remedy cures a hot illness)
How was illness understood before the 17th century?
As an internal disorder of the body, not caused by a specific agent like bacteria
Until when did the humoral vision of the body dominate in Europe?
Late seventeenth century
How was humoral medicine viewed by the Middle Ages?
It was seen as “quackery”
What new scientific approach replaced Aristotelian, qualitative, natural philosophy?
A mechanical, chemical, and mathematical vision of the world & body, developed by Galileo, Descartes, Newton, & Boyle
What are the three main functions of the circulatory system?
- Transportation (respiratory, nutritive, excretory)
- Regulation (hormonal, temperature)
- Protection (clotting, immune defense)
What substances does the circulatory system transport for cellular metabolism?
Respiratory: Oxygen & CO₂ via RBCs
Nutritive: Nutrients from digestion
Excretory: Waste removal
How does the circulatory system regulate body functions?
- Hormonal regulation (transport of hormones)
Temperature regulation (heat distribution & dissipation)
How does the circulatory system protect the body?
- Injury protection: Blood clotting
Pathogen protection: Immune response (white blood cells & antibodies)
What is hematopoiesis?
The formation of blood cells
Where do hematopoietic stem cells originate and migrate to?
They originate in the embryo and migrate to different tissues
What is the major hematopoietic organ of the fetus?
The liver
What is the major hematopoietic organ after birth?
The bone marrow
What role do cytokines play in hematopoiesis?
Cytokines play important roles in regulating and stimulating hematopoiesis.
What is the most abundant type of blood cell?
Red blood cells (RBCs)
What is the shape of red blood cells (RBCs)?
Biconcave disc shape
Where are red blood cells (RBCs) located in a blood sample after centrifugation?
Packed at the bottom
What forms the “buffy coat” in a blood sample after centrifugation?
White blood cells (WBCs) and platelets (thin, light interface)
Where is plasma located in a blood sample after centrifugation?
At the very top (fluid portion)
What is the process of erythropoiesis?
The formation of red blood cells (RBCs) from uncommitted stem cells through a series of stages in the bone marrow
What happens when the nucleus is expressed during erythropoiesis?
The cell forms a reticulocyte, which is released into circulation
What happens to the reticulocyte after it enters circulation?
It expels its nucleus and matures into a red blood cell (RBC)
Where does erythropoiesis occur?
In the bone marrow
What structure gives red blood cells (erythrocytes) their unique concave shape?
The cytoskeleton
How do red blood cells (RBCs) respond to changes in the tonicity of their environment?
They swell in hypotonic medium and shrink in hypertonic medium
What illness can affect the shape of red blood cells?
Sickle Cell Anemia
What is the primary function of erythrocytes (RBCs) and hemoglobin (Hb)?
To aid in oxygen delivery to tissues
Where is most of the oxygen found in the blood?
Most oxygen is bound to hemoglobin (Hb) in red blood cells (RBCs)
What gives blood its red color?
Hemoglobin (Hb)
What is the structure of hemoglobin in red blood cells?
Hemoglobin is made up of 4 globin proteins (2 alpha, 2 beta), each with a heme group that binds an iron molecule
How does heme iron interact with oxygen?
Heme iron combines with oxygen in the lungs and releases oxygen into tissues
How much oxygen can each red blood cell (RBC) carry?
Each RBC can carry over a billion molecules of oxygen (280 million hemoglobin molecules per RBC x 4 heme groups)
How does the oxygen content change as blood moves from the arteries to the veins?
Blood entering tissues contains 200 mL O₂/L, and blood leaving tissues contains 155 mL O₂/L, meaning 45 mL O₂ is unloaded to tissues.
What is the oxygen-hemoglobin saturation in systemic arteries and veins?
In systemic arteries, ~97% of hemoglobin is saturated with oxygen (oxyhemoglobin). In systemic veins, the saturation drops to ~75%, with about 22% of the oxygen unloaded to tissues.
What physiologic factors can change hemoglobin (Hb) conformation and affect oxygen binding?
Factors like pH and temperature can change Hb conformation, influencing oxygen binding.
How does a decrease in pH affect hemoglobin’s affinity for oxygen?
A decrease in pH decreases Hb’s affinity for oxygen, leading to more oxygen being offloaded into tissues. This occurs during exercise when muscle activity produces lactic acid (Bohr effect).
How does an increase in temperature affect hemoglobin’s affinity for oxygen?
An increase in temperature decreases Hb’s affinity for oxygen, leading to more oxygen being offloaded into tissues.
What is the Bohr effect?
The Bohr effect describes how a decrease in pH (e.g., due to lactic acid from muscle activity) reduces hemoglobin’s affinity for oxygen, enhancing oxygen delivery to tissues.
How does temperature affect the bond between oxygen and hemoglobin?
Higher temperatures weaken the bond between oxygen and hemoglobin, promoting more oxygen offloading into tissues.
What is the oxygen-hemoglobin dissociation curve?
It describes the relationship between the partial pressure of oxygen (pO₂) and the percentage of hemoglobin saturated with oxygen, indicating how oxygen is loaded into the blood and unloaded into tissues.
How much does oxyhemoglobin decrease as blood passes from arteries to veins through the tissues?
Oxyhemoglobin decreases by ~22% as blood moves from arteries to veins.
What is the oxygen reserve in venous blood?
The oxygen reserve is the oxyhemoglobin remaining in venous blood, which is enough to sustain the brain and heart for ~4-5 minutes without breathing or CPR. It can also be used when tissue oxygen requirements increase (e.g., during exercise).
What happens to oxygen unloading in tissues during exercise?
Oxygen unloading increases (more oxygen is delivered to tissues) during exercise due to factors like increased temperature and decreased pH.
How does oxygen unloading change under normal conditions?
Oxygen unloading decreases (less oxygen is offloaded to tissues) when conditions are such that hemoglobin’s affinity for oxygen is higher (e.g., higher pH, lower temperature).
What structures do mature red blood cells (RBCs) lack?
Mature RBCs lack nuclei, mitochondria, and endoplasmic reticulum (ER).
How do mature RBCs obtain energy?
RBCs obtain energy through anaerobic metabolism of glucose, as they cannot respire aerobically.
What happens in the glycolytic pathway that leads to the production of 2,3-DPG?
A side reaction in the glycolytic pathway results in the production of 2,3-Diphosphoglyceric Acid (2,3-DPG).
What enzyme produces 2,3-DPG, and how is it regulated?
The enzyme producing 2,3-DPG is inhibited by oxyhemoglobin. When oxyhemoglobin levels decrease (e.g., in hypoxia or anemia), 2,3-DPG production increases.
How does increased 2,3-DPG concentration affect oxygen unloading?
Increased 2,3-DPG concentration enhances oxygen unloading by shifting the oxygen-hemoglobin dissociation curve to the right, facilitating more oxygen delivery to tissues.
What happens as RBCs age?
RBCs become fragile and eventually are destroyed.
What is the lifespan of a red blood cell (RBC)?
The lifespan of a RBC is 120 days.
What is bilirubin, and how is it produced?
Bilirubin is produced when old RBCs are destroyed in the spleen, as a breakdown product of heme from hemoglobin (Hb).
How is bilirubin processed in the body?
Liver enzymes bind bilirubin, and it is excreted into bile.
How is bilirubin eliminated from the body?
Bilirubin circulates in bile and is eventually lost in urine and feces.
What is jaundice and what causes it?
Jaundice is associated with high blood concentrations of bilirubin (hyperbilirubinemia) from the death of red blood cells (RBCs).
Why do healthy newborns experience jaundice?
Healthy newborns experience a rapid decrease in blood hemoglobin (Hb) at birth, leading to increased bilirubin levels.
Why are preemies more likely to experience jaundice?
Preemies often have inadequate amounts of liver enzymes needed to bind bilirubin, preventing its excretion in bile, making it toxic.
What is alpha thalassemia?
Alpha thalassemia is characterized by decreased synthesis of alpha hemoglobin chains.
What is beta thalassemia?
Beta thalassemia involves impaired synthesis of beta hemoglobin chains.
What is sickle cell anemia and how is it inherited?
Sickle cell anemia is an inherited, recessive disease where two copies of the gene produce hemoglobin S (Hb-S) instead of normal hemoglobin A (Hb-A).
What causes sickle cell anemia at the molecular level?
A single amino acid substitution in the beta globin chain of hemoglobin leads to polymerization of Hb-S into long fibers, causing red blood cells to take on a sickle shape and promoting hemolysis.
What is the function of albumins in blood plasma?
Albumins provide osmotic pressure needed to draw water from surrounding tissue fluid into capillaries, helping maintain blood volume and pressure.
Where are albumins produced and what percentage of plasma proteins do they account for?
Albumins are produced in the liver and account for most of the plasma proteins, making up 90% of plasma proteins when combined with 9 other proteins.
What are globulins and their function in plasma?
Globulins are proteins in plasma; alpha and beta globulins transport lipids and fat-soluble vitamins, while gamma globulins (antibodies) are produced by lymphocytes and function in immunity.
Where are fibrinogen proteins produced and what is their role in the body?
Fibrinogen is produced in the liver and is important for clot formation.
agglutination
- occurs when A-type RBCs are mixed with anti-A-type antibodies
- occurs when B-type RBCs are mixed with anti-B-type antibodies
What is the Rh factor and where is it found?
The Rh factor is a group of antigens found on red blood cells (RBCs).
Can A/B antibodies cross the placenta?
No, A/B antibodies cannot cross the placenta, but Rh antibodies can.
What can happen if an Rh-negative mother has an Rh-positive baby?
If an Rh-negative mother has an Rh-positive baby, it may cause issues during birth, as the mother could become sensitized and produce antibodies against the Rh antigen.
What is Hemolytic Disease of the newborn?
Hemolytic Disease occurs when Rh antibodies from the mother cross the placenta in a subsequent pregnancy, causing RBC hemolysis in the fetus.
what are the 3 steps of blood clotting
- vasocontraction
- formation of a platelet plug
- production of a web of fibrin proteins that penetrate & surround platelet plug
What is the role of fibrinogen in blood clotting?
Fibrinogen is converted by thrombin into fibrin, which forms the clot.
What pathway is involved in blood clotting in vivo (inside the body)?
The extrinsic pathway is involved in blood clotting in vivo.
What pathway is involved in blood clotting in vitro (outside the body)?
The intrinsic pathway is involved in blood clotting in vitro.
clot dissolution
plasminogen converted to
plasmin which digests
fibrin (promotes clot
dissolution)
What is the initial treatment for heart attack patients to stop platelet clumping?
Heart attack patients are usually treated with chewable aspirin to stop platelet clumping before being evaluated for angioplasty or clot-dissolving drugs.
What is a commonly used clot-dissolving medication in U.S. ER departments?
One of the most commonly used clot-dissolving medications in U.S. ER departments is tissue plasminogen activators (TPAs).
What other medical conditions can tissue plasminogen activators (TPAs) be used for?
TPAs can also be used for stroke, blood clots, and other related conditions.
What is STEMI?
ST Elevated Myocardial Infarction (STEMI) is the most severe type of heart attack, where the artery supplying blood to the heart becomes blocked.
What class of drugs is preferred for treating STEMI, and why?
Fibrinolytic drugs are the preferred pharmacological class for STEMI treatment because they can achieve reperfusion, unlike drugs from other classes.
How do fibrinolytic drugs work in STEMI treatment?
Fibrinolytics convert plasminogen to plasmin, which cleaves fibrin, leading to clot dissolution and restoration of blood flow to ischemic tissues.
