英文医学课件：3 血液生理

1、BLOOD【血液】,Objectives,After studying this part, you should be able to: describe the components of blood, their origins, and the role of hemoglobin in transporting oxygen in red blood cells. understand the molecular basis of blood groups and the reasons for transfusion reactions. delineate the process

2、 of hemostasis that restricts blood loss when vessels are damaged, and the adverse consequences of intravascular thrombosis. understand the basis of disease states where components of the blood are abnormal, dysregulated, or both.,Plasma（血浆） Blood Cells Red Blood Cells (RBC) or Erythrocytes（红细胞） Whi

3、te Blood Cells (WBC) or Leucocytes（白细胞） Platelets (PLT) or Thrombocytes（血小板）,Components of blood,Plasma,The fluid portion of the blood, the plasma, is a remarkable solution containing an immense number of ions, inorganic molecules, and organic molecules that are in transit to various parts of the bo

4、dy or aid in the transport of other substances Normal plasma volume is about 5% of body weight, or roughly 3500 mL in a 70-kg man Plasma clots on standing, remaining fluid only if an anticoagulant is added If whole blood is allowed to clot and the clot is removed, the remaining fluid is called serum

5、 Serum has essentially the same composition as plasma, except that its fibrinogen and clotting factors II, V, and VIII have been removed and it has a higher serotonin content because of the breakdown of platelets during clotting,System for Naming Blood-Clotting Factors,Some of the Proteins Synthesiz

6、ed by the Liver: Physiologic Functions and Properties,Plasma includes water, ions, proteins, nutrients, hormones, wastes, etc.,the volume of red blood cells as a percentage of centrifuged whole blood M: 4050% F: 3748%,Hematocrit（packed cell volume, 血细胞比容）,International Council for Standardization in

7、 Haematology (ICSH) Recommendations for Surrogate Reference Method for the Packed Cell Volume,Bone Marrow,In the adult, red blood cells, many white blood cells, and platelets are formed in the bone marrow In the fetus, blood cells are also formed in the liver and spleen, and in adults such extramedu

8、llary hematopoiesis may occur in diseases in which the bone marrow becomes destroyed or fibrosed,Changes in red bone marrow cellularity in various bones with age,Normal Values for the Cellular Elements in Human Blood,Development of various formed elements of the blood from bone marrow cells,White bl

9、ood cells (Leucocytes)（白细胞）,Platelets (Thrombocytes) 血小板,Platelets are small, granulated bodies that aggregate at sites of vascular injury They lack nuclei and are 24 m in diameter There are about 300,000/L of circulating blood, and they normally have a half-life of about 4 days The megakaryocytes,

10、giant cells in the bone marrow, form platelets by pinching off bits of cytoplasm and extruding them into the circulation Between 60 and 75% of the platelets that have been extruded from the bone marrow are in the circulating blood, and the remainder are mostly in the spleen Splenectomy causes an inc

11、rease in the platelet count (thrombocytosis),Physiological properties of platelets,Adhesion,Physiological properties of platelets,Aggregation,Physiological properties of platelets,Release or secretion,Physiological properties of platelets,Contraction,Red blood cells (Erythrocytes) （红细胞）,The red bloo

12、d cells (erythrocytes) carry hemoglobin in the circulation They are biconcave disks that are manufactured in the bone marrow In mammals, they lose their nuclei before entering the circulation In humans, they survive in the circulation for an average of 120 days The average normal red blood cell coun

13、t is 5.4 million/L in men and 4.8 million/L in women The number of red cells is also conveniently expressed as the hematocrit, or the percentage of the blood, by volume, that is occupied by erythrocytes. Each human red blood cell is about 7.5 m in diameter and 2 m thick, and each contains approximat

14、ely 29 pg of hemoglobin There are thus about 3 1013 red blood cells and about 900 g of hemoglobin in the circulating blood of an adult man,Human red blood cells and fibrin fibrils,Red cell formation and destruction,Role of the Spleen,The spleen is an important blood filter that removes aged or abnor

15、mal red cells It also contains many platelets and plays a significant role in the immune system Abnormal red cells are removed if they are not as flexible as normal red cells and consequently are unable to squeeze through the slits between the endothelial cells that line the splenic sinuses,Hemoglob

16、in,The red, oxygen-carrying pigment in the red blood cells of vertebrates is hemoglobin, a protein with a molecular weight of 64,450,Reactions of Hemoglobin,Hemoglobin in the Fetus,The blood of the human fetus normally contains fetal hemoglobin (hemoglobin F) Its structure is similar to that of hemo

17、globin A except that the chains are replaced by chains; that is, hemoglobin F is 22 Fetal hemoglobin is normally replaced by adult hemoglobin soon after birth,Blood Types,The membranes of human red cells contain a variety of blood group antigens, which are also called agglutinogens (凝集原) The most im

18、portant and best known of these are the A and B antigens, but there are many more,Antigens of the ABO system on the surface of red blood cells,Summary of ABO System,The Rh Group,Aside from the antigens of the ABO system, those of the Rh system are of the greatest clinical importance The Rh factor, n

19、amed for the rhesus monkey because it was first studied using the blood of this animal, is a system composed primarily of the C, D, and E antigens, although it actually contains many more Unlike the ABO antigens, the system has not been detected in tissues other than red cells D is by far the most a

20、ntigenic component, and the term Rh-positive as it is generally used means that the individual has agglutinogen D The D protein is not glycosylated, and its function is unknown The Rh-negative individual has no D antigen and forms the anti-D agglutinin when injected with D-positive cells The Rh typi

21、ng serum used in routine blood typing is anti-D serum Eighty-five per cent of Caucasians are D-positive and 15% are D-negative; over 99% of Asians are D-positive Unlike the antibodies of the ABO system, anti-D antibodies do not develop without exposure of a D-negative individual to D-positive red ce

22、lls by transfusion or entrance of fetal blood into the maternal circulation D-negative individuals who have received a transfusion of D-positive blood (even years previously) can have appreciable anti-D titers and thus may develop transfusion reactions when transfused again with D-positive blood,Hem

23、olytic Disease of the Newborn,Hemostasis,Hemostasis is the process of forming clots in the walls of damaged blood vessels and preventing blood loss while maintaining blood in a fluid state within the vascular system A collection of complex interrelated systemic mechanisms operates to maintain a bala

24、nce between coagulation and anticoagulation,Summary of reactions involved in hemostasis,The Clotting Mechanism,Anticlotting Mechanisms,The tendency of blood to clot is balanced in vivo by reactions that prevent clotting inside the blood vessels, break down any clots that do form, or both These react

25、ions include the interaction between the platelet-aggregating effect of thromboxane A2 and the antiaggregating effect of prostacyclin, which causes clots to form at the site when a blood vessel is injured but keeps the vessel lumen free of clot,Examples of Diseases Due to Deficiency of Clotting Fact

26、ors,Anticlotting Mechanisms,Antithrombin III is a circulating protease inhibitor that binds to serine proteases in the coagulation system, blocking their activity as clotting factors. This binding is facilitated by heparin, a naturally occurring anticoagulant that is a mixture of sulfated polysaccha

27、rides. The clotting factors that are inhibited are the active forms of factors IX, X, XI, and XII The endothelium of the blood vessels also plays an active role in preventing the extension of clots. All endothelial cells except those in the cerebral microcirculation produce thrombomodulin, a thrombi

28、n-binding protein, on their surfaces. In circulating blood, thrombin is a procoagulant that activates factors V and VIII, but when it binds to thrombomodulin, it becomes an anticoagulant in that the thrombomodulinthrombin complex activates protein C. Activated protein C (APC), along with its cofacto

29、r protein S, inactivates factors V and VIII and inactivates an inhibitor of tissue plasminogen activator, increasing the formation of plasmin Plasmin (fibrinolysin) is the active component of the plasminogen (fibrinolytic) system,The fibrinolytic system and its regulation by protein C,Anticoagulants

30、,Heparin is a naturally occurring anticoagulant that facilitates the action of antithrombin III. Low-molecular-weight fragments have been produced from unfractionated heparin, and these are seeing increased clinical use because they have a longer half-life and produce a more predictable anticoagulan

31、t response than unfractionated heparin. The highly basic protein protamine forms an irreversible complex with heparin and is used clinically to neutralize heparin In vivo, a plasma Ca2+ level low enough to interfere with blood clotting is incompatible with life, but clotting can be prevented in vitr

32、o if Ca2+ is removed from the blood by the addition of substances such as oxalates, which form insoluble salts with Ca2+, or chelating agents, which bind Ca2+ Coumarin derivatives (香豆素类) such as dicumarol and warfarin are also effective anticoagulants. They inhibit the action of vitamin K, which is

33、a necessary cofactor for the enzyme that catalyzes the conversion of glutamic acid residues to -carboxyglutamic acid residues. Six of the proteins involved in clotting require conversion of a number of glutamic acid residues to -carboxyglutamic acid residues before being released into the circulatio

34、n, and hence all six are vitamin K-dependent. These proteins are factors II (prothrombin), VII, IX, and X, protein C, and protein S,Summary,Blood cells; plasma Blood cells arise in the bone marrow and are subject to regular renewal; the majority of plasma proteins are synthesized by the liver Hemogl

35、obin; fetal hemoglobin; mutated forms of hemoglobin lead to red cell abnormalities and anemia Blood group systems Hemostasis Clotting mechasnism Anticlotting mechanisms Anticoagulants,Which of the following statements is correct? A Damaged tissue releases a substance called tissue fibrinogen, which

36、is mainly composed of phospholipids B Damage to the vessel wall initiates what is called the intrinsic pathway C The activation of protein coagulation factor plus the release of platelet thromboplastin eventually leads directly to the formation of thrombin D The actual blood clotting is caused by a conversion of the plasma protein prothrombin into another protein thrombin, which is the enzyme that causes the polymerization of the plasma fibrinogen molecules into fibrin threads that lead to blood clotting E Damage to platelets ca