Chapter 3 Blood

1. What is hematocrit?

The percentage of blood volume that is occupied by RBC.

2. What are Crystal Osmotic Pressure and Colloid Osmotic Pressure of plasma? What are the major roles of them in blood volume and osmotic homeostasis?

The osmotic pressure of plasma is about 300mOsm (milliosmol), mainly come from the crystalline substance especially sodium and chloride ions, called Crystal Osmotic Pressure, a few come from plasma protein, called Colloid Osmotic Pressure.

The main role of plasma colloid osmotic pressure is determining the distribution of fluid between the plasma and the ISF compartments by controlling transcapillary dynamics to keep normal plasma volume. The main role of plasma Crystal smotic pressure is determining the distribution of fluid inside and outside cells to keep cells in normal volume and shape.

3. Please briefly describe the physiological properties of red blood cells.

1Plastic deformation

2Suspension stability

3Osmotic fragility

4. What is erythrocyte sedimentation rate?

The distance that red blood cells settle in a tube in one hour.

5. Please briefly describe the regulatory effects of erythropoietin on red blood cell production?

Erythropoietin is the principal stimulus for RBC production in low oxygen states. Normally, about 90 percent of all erythropoietin is formed in the kidneys, and the remainder is formed mainly in the liver. Renal secrete the erythropoietin in response to hypoxia. The important effect of erythropoietin is to stimulate the production of proerythroblasts from hematopoietic stem cells in the bone marrow. In addition, once the proerythroblasts are formed, the erythropoietin causes these cells to pass more rapidly through the different erythroblastic stages than they normally do, further speeding up the production of new RBCs. The rapid production of cells continues as long as the person remains in a low oxygen state or until enough RBCs have been produced to carry adequate amounts of oxygen to the tissues despite the low level of oxygen; at this time, the rate of erythropoietin production decreases to a level that will maintain the required number of RBCs but not an excess.

6. Please briefly describe the nutritional requirements for maturation of red blood cells?

(1) vitamin B12

(2) folic acid

7. Why do patients with atrophic gastric mucosa often complicate with megaloblastic anemia?

The parietal cells of the gastric glands secrete a glycoprotein called intrinsic factor, which combines with vitamin B12 in food and makes the B12 available for absorption by the gut. Patients with atrophic gastric mucosa fails to produce normal gastric secretions. Lack of intrinsic factor, therefore, decreases availability of vitamin B12. Vitamin B12 is especially important for the synthesis of DNA and final maturation of the RBCs. Therefore, atrophic gastric mucosa can cause megaloblastic anemia for deficiency of B12.

8. Please briefly describe the pathogenesis of hemolytic disease of the newborn?

In most instances of Hemolytic Disease of the Newborn, the mother is Rh negative and the father is Rh positive. The baby has inherited the Rh-positive antigen from the father, and the mother develops anti-Rh agglutinins from exposure to the fetus’s Rh antigen. In turn, the mother’s agglutinins diffuse through the placenta胎盘 into the fetus and cause RBC agglutination.

 

9. What is hemostasis? Please briefly describe the essential mechanisms underlying hemostasis?

The term hemostasis means prevention of blood loss.Whenever a vessel is cut or ruptured, hemostasis is achieved by several mechanisms: (1) vascular constriction, (2) formation of a platelet plug, (3) formation of a blood clot as a result of blood coagulation, and (4) eventual growth of fibrous tissue into the blood clot to close the hole in the vessel permanently

10. Please briefly describe the essential steps of blood clotting?

Clotting takes place in three essential steps

(1) Formation of prothrombin activator

(2) Conversion of prothrombin to thrombin.

(3) Conversion of fibrinogen into fibrin fibers

11. Please briefly describe the difference between the extrinsic and intrinsic pathways in clotting initiation?

It is clear that after blood vessels rupture, clotting occurs by both pathways simultaneously. Tissue factor initiates the extrinsic pathway, whereas contact of Factor XII and platelets with collagen in the vascular wall initiates the intrinsic pathway. An especially important difference between the extrinsic and intrinsic pathways is that the extrinsic pathway can be explosive; once initiated, its speed of completion to the final clot is limited only by the amount of tissue factor released from the traumatized tissues and by the quantities of Factors X, VII, and V in the blood. With severe tissue trauma, clotting can occur in as little as 15 seconds. The intrinsic pathway is much slower to proceed, usually requiring 1 to 6 minutes to cause clotting.


2018年09月20日

Chapter 2 Cell-Review Questions with Reference Answers by Dr. Shuwei Jia
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