Qiang XIA ( 夏强 ), PhD

Department of Physiology

Room C518, Block C, Research Building, School of Medicine

Tel: 88208252

Email: xiaqiang@zju.edu.cn

BLOOD 【血液】

Body Fluid = 60% of Body Weight (BW)

Intracellular Fluid2/3, 40% of BW

Extracellular Fluid1/3, 20% of BW

Plasma 5% of BW

Interstitial Fluid15% of BW

70 kg Male, 42 L

Internal environment （内环境）

Extracellular Fluid1/3, 20% of BW

Plasma 5% of BW

Interstitial Fluid15% of BW

Internal Environment

Homeostasis （稳态）Homeostasis (from

the Greek words for

“same” and “steady”):

maintenance of

static or constant

conditions in the

internal

environmentWalter B. Cannon

http://www.harvardsquarelibrary.o

rg/unitarians/cannon_walter.html

Components of Homeostasis:

Concentration of O2 and CO2

pH of the internal environment

Concentration of nutrients and waste products

Concentration of salt and other electrolytes

Volume and pressure of extracellular fluid

----Regulation

Body's systems operate together to

maintain homeostasis:

Skin system Skeletal and muscular system

Circulatory system Respiratory system

Digestive system Urinary system

Nervous system Endocrine system

Lymphatic system Reproductive system

How is homeostasis achieved?

Components of blood

Plasma （血浆）Blood Cells

Red Blood Cells (RBC) or Erythrocytes （红细胞）White Blood Cells (WBC) or Leucocytes （白细胞）Platelets (PLT) or Thrombocytes （血小板）

Plasma includes water, ions, proteins, nutrients, hormones, wastes, etc.

The hematocrit （血细胞比容） is a rapid assessment of blood composition.It is the percent of the blood volume that is composed of RBCs (red blood cells).

the volume of red blood cells as a percentage of

centrifuged whole blood

M: 40~50%

F: 37~48%

Hematocrit （ packed cell volume, 血细胞比容）

International Council for Standardization in Haematology (ICSH) Recommendations for "Surrogate Reference" Method for the Packed Cell Volume

Physical & chemical properties of blood

1. Specific Gravity （比重）Depending on hematocrit & protein composition

Whole blood ： 1.050~1.060

Plasma ： 1.025~1.035

Red blood cells ： 1.090

2. Viscosity （粘度）

relative viscosity of whole blood 4~5

depending on hematocrit

relative viscosity of plasma 1.6~2.4

related to the protein composition of  the plasma

3. Osmotic Pressure （渗透压）

The osmotic pressure of a solution depends on the number of solute particles in the solution, NOT on their chemical composition and size

Plasma osmotic pressure (~300 mOsm/L ）Crystalloid Osmotic Pressure （晶体渗透压）

Pressure generated by all crystal substances, particularly

electrolytes

Important in maintaining fluid balance across cell

membranes

Colloid Osmotic Pressure （胶体渗透压）Osmotic pressure generated by plasma proteins, particularly

albumin.

Approximately 25 mmHg, but important in fluid transfer

across capillaries

4. Plasma pH

Normal range: 7.35~7.45

Buffer systems （缓冲系统） :

NaHCO3/H2CO3, Pro-Na/Pro, Na2HPO4/NaH2PO4

Hb-K/Hb, HbO2-K/HbO2, K2HPO4/KH2PO4, KHCO3/H2CO3

Functions of bloodTransportation

O2 and CO2 Nutrients (glucose, lipids, amino acids) Waste products (e.g., metabolites) Hormones

RegulationpHBody temperature

ProtectionBlood coagulationImmunity

Body Fluid = 60% of Body Weight (BW)

Intracellular Fluid2/3, 40% of BW

Extracellular Fluid1/3, 20% of BW

Plasma 5% of BW

Interstitial Fluid15% of BW

70 kg Male, 42 L

Plasma

Water (92% of plasma)serves as transport medium; carries heat

Proteins (6~8% of plasma)Inorganic constituents (1% of plasma)

e.g., Na+, Cl-, K+, Ca2+…

Nutrients glucose, amino acids, lipids & vitamins

Waste products e.g., nitrogenous wastes like urea

Dissolved gases O2 & CO2

Hormones

Composition

Plasma proteins

•Albumins （白蛋白） (60-80% of plasma proteins) •most important in maintenance of osmotic balance •produced by liver

•Globulins （球蛋白） (1-, 2-, -, -)•important for transport of materials through the blood (e.g.,

thyroid hormone & iron) •clotting factors •produced by liver except -globulins which are

immunoglobulins (antibodies) produced by lymphocytes

•Fibrinogen （纤维蛋白原） •important in clotting •produced by liver

Red blood cells (Erythrocytes) （红细胞）

StructureBiconcaveNo nucleusFew organellesSmallHemoglobin molecules

Count

RBC count

M:

4.0~5.5×1012/L

F:

3.5~5.0×1012/L

Hemoglobin （血红蛋白）M: 120~160

g/L

F: 110~150

g/L

Physiological properties

Plastic deformability

（可塑变形性）

Erythrocyte Sedimentation Rate (ESR) （红细胞沉降率）The distance that red blood cells settle in a tube of blood in one

hour

Normal value [Westergren method （魏氏法，国际血液学标准化委员会推荐魏氏法为标准法） ]:

M: 0~15 mm/h ， F: 0~20 mm/h

An indication of inflammation which increases in many diseases,

such as tuberculosis & rheumatoid arthritis…

d

Suspension stability （悬浮稳定性）

International Council for Standardization in Haematology (ICSH)

红细胞叠连（ Rouleaux formation ）

Osmotic fragility （渗透脆性）

the susceptibility of a red blood cell to break apart when

exposed to saline solutions of a lower osmotic pressure

than that of the human cellular fluid

Notice that hemolysis begins in the 0.45% tube and is complete in the 0.35% tube.

Only substances which act as impermeant molecules can

be used to make isotonic solutions （等张溶液） . E.g.

cells placed in an isosmotic solution （等渗溶液） of

urea (1.9%), a permeant molecule, will swell and bust.

Solutions which have the same calculated osmotic

pressure are said to be ISOSMOTIC but are not

necessarily ISOTONIC

Function of RBCs

1. Transport of O2 and CO2

2. Buffering

Production of RBC (Erythropoiesis)

Hemocytoblast stem cellStem cell becomes committedEarly erythroblasts have ribosomes Erythroblasts accumulate iron and hemoglobinNormoblasts eject organellesReleased as erythrocyte

Nutritional Requirements for Erythropoiesis

1. Many vitamins, minerals, and proteins are necessary for normal RBC

production

2. Clinically, folic acid （叶酸） , VitB12, and iron （铁） are the most

important.

Deficiencies of these factors lead to characteristic anemias （贫血）

Diagram of iron kinetics from iron stores to developing red blood cell (RBC). Iron stores include the bone marrow, reticuloendothelial system (liver and spleen) and RBCs. Transferrin (total iron-binding capacity [TIBC]) transports iron (Fe) to developing erythrocytes. Iron is deposited in the RBC, and transferrin returns to storage sites to bind more Fe for transport. Lactoferrin is a competitor of transferrin; it takes Fe that is free and returns it to storage sites. Lactoferrin levels are elevated in anemia of chronic disease. Increases in interleukin-1 increase the sequestration of Fe in storage sites. (Hb=hemoglobin)

Regulation of Erythropoiesis

1. Erythropoietin （促红细胞生成素）

2. Hormones:

Androgen （雄激素）

Others

Hypoxia-inducible factor-1, HIF-1

Erythropoiesis is hormonally regulated:

decreased oxygen delivery to the kidney causes the secretion of erythropoietin, which activates receptors in bone marrow, leading to an increase in the rate of erythropoiesis.

average lifespan = about 120 days

Destruction of RBC

Macrophages engulf old RBCs Iron is salvaged Heme degrades into bilirubin

Anemia（贫血）

Anemia is defined as a qualitative or quantitative deficiency of hemoglobin, a protein found inside red blood cells (RBCs)

The three main classes of anemia ：excessive blood loss (acutely such as a

hemorrhage or chronically through low-volume loss)excessive blood cell destruction (hemolysis)deficient red blood cell production (ineffective

hematopoiesis)

Iron deficiency anemia

（缺铁性贫血）

巨幼红细胞性贫血（ megaloblastic anemia ）

Hemolysis（溶血）Red blood cells without (left and middle) and with (right)

hemolysis. Note that the hemolyzed sample is transparent, because there are no cells to scatter light.

White blood cells (Leucocytes)（白细胞） Types of WBC

WBC Count (109/L) %Granulocytes

Neutrophils 2.0~7.0 50~70Eosinophils 0.02~0.5 0.5~5Basophils 0~0.1 0~1

Monocytes 0.12~0.8 3~8Lymphocytes 0.8~4.0 20~40

Total 4~10

WBC count

Leukopoiesis

Myeloblasts become all of the granular leukocytes Monoblasts become monocytes Lymphoblasts become lymphocytes

Platelets (Thrombocytes)

Formed in the bone marrow from cells called megakaryocytes

Without nucleus, but can secrete a variety of substances

normal value:

(100~300) x 109/L Average lifespan=7~14 days Play an important role in

hemostasis

1. Adhesion

Platelets adhere to the vessel wall at the site of injury

Physiological properties of platelets

von Willebrand factor, vWF

Unifying model of platelet adhesion to collagen at arterial shear. Two different pathways by which human and mouse platelets firmly adhere to collagen at arterial shear are illustrated. In both, the majority of platelets are initially tethered to collagen via GP Ib/IX/V interacting with collagen-bound VWF (left), although a minority of platelets interact directly with collagen independently of VWF/GP Ib/IX/V. In the first pathway (upper), signaling from GP VI first leads to activation of integrins α2β1 (GP Ia/IIa) and αIIbβ3 (GP IIb/IIIa). Activated integrins then firmly attach the platelet to collagen, either directly (α2β1) or via collagen-bound VWF (αIIbβ3) (right). In the second pathway (lower), platelets first adhere to collagen via integrin α2β1, before GP VI engages collagen and induces activation. These two pathways are likely to reinforce each other and the events of thrombus formation. Release of secondary mediators (ADP and TxA2) would further potentiate these events (right). (Redrawn from Auger JM, Kuijpers MJ, Senis YA: Adhesion of human and mouse platelets to collagen under shear: a unifying model. FASEB J 2005;19:825-827.)

2. Aggregation

Platelets adhere to one another

Platelet Aggregation Pathway Platelet activation and coagulation normally do not occur within an intact blood vessel. After vessel wall injury, platelet-plug formation is initiated by the adherence of platelets to subendothelial collagen. In high shear arterial blood, platelets are first slowed down from their blood flow velocity by interacting with the collagen-bound von Willebrand factor (VWF) and subsequently stopped by binding directly to collagen via their glycoprotein receptor complex. The activation of these collagen receptors on platelets following their binding to collagen activates phospholipase C (PLC)-mediated cascades. This results in a mobilization of calcium from the dense tubula system. An increase in intracellular calcium is associated with activation of several kinases necessary for morphological change, the presentation of the procoagulant surface, the secretion of platelet granular content, the activation of glycoproteins, and the activation of Phospholipase A2 (PLA2). Activation of PLA2 releases arachidonic acid (AA), which is a precursor for TBXA2 synthesis. PTGS1 catalyzes the first step in the formation of TBXA2 from AA. This reaction is irreversibly blocked by aspirin, which also leads to the blockage of platelet aggregation

These processes result in the local accumulation of molecules like thrombin, TBXA2, and ADP, which are important for the further recruitment of platelets as well as the amplification of activation signals as described above. The secreted agonists activate their respective G protein coupled receptors: thrombin receptor (F2R), thomboxane A2 receptor (TBXA2R), and ADP receptors (P2RY1 and P2RY12). The P2RY12 receptor couples to Gi, and when activated by ADP, inhibits adenylate cyclase. This interaction counteracts the stimulation of cAMP formation by endothelial-derived prostaglandins, which alleviates the inhibitory effect of cAMP on IP3-mediated calcium release. Thienopyridines, a class of oral antiplatelet agents, permanently inhibit P2RY12 signaling, which is sufficient to block platelet activation.

F2R, TBXA2R and P2RY1 couple to the Gq-PLC-IP3-Ca2+ pathway, inducing shape change and platelet aggregation. In addition, receptor signaling through G12/13 (F2R; TBXA2R) contributes to morphological changes through activation of kinases.

Platelet adhesion, cyotoskeletal reorganization, secretion, and amplification loops are all different steps towards the formation of a platelet-plug. These cascades result in the activation of the Fibrinogen Receptor expressed on platelet cells. This activation develops binding sites for fibrinogen, which are not available in inactive platelets. The binding of fibrinogen results in the linkage of activated platelets through fibrinogen bridges, thereby mediating aggregation. Inhibition of this receptor through Glycoprotein IIb/IIIa inhibitors blocks platelet aggregation induced by any agonist.

Inducers of platelet aggregation

ADP

Low dose1st reversible phase

High dose 2nd irreversible phase

Thromboxane A2 (TXA2)

Collagen

Thrombin

Phospholipid

Arachidonic Acid

Phospholipase A2

TXA2

Cyclo-oxygenase

PGG2 & PGH2

PGI2

Prostacyclin synthase(Vascular endothelium)

Thromboxane synthase(Platelets)

Aggregation Anti-aggregationContraction Relaxation

Platelet interactions with agonists and antagonists of platelet aggregation, the vessel wall, other platelets, and adhesive macromolecules. Agents in parentheses prevent the formation or inhibit the function of the adjacent agonists of platelet aggregation. ADP = adenosine diphosphate, VWF = von Willebrand factor, cAMP = cyclic adenosine monophosphate, GP = glycoprotein.

3. Release or secretion:

Platelets contain alpha and dense granulesDense granules: containing ADP or ATP, calcium,

and serotonin α-granules: containing platelet factor 4, PDGF,

fibronectin, B-thromboglobulin, vWF, fibrinogen, and coagulation factors V and XIII

Schematic drawing of the platelet (top figure), showing its alpha and dense granules and canalicular system. The bottom figure illustrates the platelet's major functions, including secretion of stored products, as well as its attachment, via specific surface glycoproteins (GP), to denuded epithelium (bottom) and other platelets (left).VWF: von Willebrand factor; TSP: thrombospondin; PF4: platelet factor 4; PDGF: platelet derived growth factor; -TG: beta thromboglobulin; ADP: adenosine diphosphate; ATP: adenosine triphosphate.

A schematic representation of selected platelet responses to activation and the congenital disorders of platelet function. AC = adenylyl cyclase; BSS = Bernard–Soulier syndrome; CO = cyclooxygenase; DG = diacylglycerol; G = GTP-binding protein; IP3 = inositol trisphosphate; MLC = myosin light chain; MLCK = myosin light chain kinase; P2Y1, P2Y12 = G-protein-coupled ADP receptors; PAF = platelet activating factor; PGG2/PGH2 = prostaglandin arachidonic pathway intermediates; PIP2 = phosphatidylinositol bisphosphate; PKC = protein kinase C; PLA2 = phospholipase A2; TK = tyrosine kinase; PLC = phospholipase C; TS = thromboxane synthase; TxA2 = thromboxane A2; vWD = von Willebrand disease; vWF = von Willebrand factor. The Roman numerals in the circles represent coagulation factors and yellow Ps indicate phosphorylation. (Modified with permission from Rao AK: Congenital disorders of platelet function: disorders of signal transduction and secretion. Am J Med Sci 1998; 316:69-76.)

4. Contraction

Clot retraction ( 血块回缩 )

5. Adsorption

Clotting factors: I, V, XI, XIII

Production of Platelets (Thrombocytes)

FormationLarge multinucleated cells that pushes against the wall

of the capillaryCytoplasmic extensions stick through and separate

ThrombopoietinThrombopoietin (leukemia virus oncogene

ligand, megakaryocyte growth and development factor), is a glycoprotein hormone produced mainly by the liver and the kidney that regulates the production of platelets by the bone marrow

It stimulates the production and differentiation of megakaryocytes, the bone marrow cells that fragment into large numbers of platelets

Hemostasis（止血） The arrest of bleeding following injury and the

result of 3 interacting, overlapping mechanisms:

Vascular spasm （血管收缩）Formation of a platelet plug （血小板血栓形成）Blood coagulation (clotting) （血液凝固）

Bleeding time ( 出血时间 ) ： <9 min

Role of vascular endothelium in hemostasiso Vasoconstriction: reduced blood flow facilitates

contact activation of platelets and coagulation factors

o Exposure of sub-endothelial basement membrane

and collagen

o Release of tissue thromboplastins ( 组织因子 )

o Synthesis of basement membrane components,

tissue factor ( 组织因子 ), vWF, plasminogen activator

( 纤溶酶原激活物 ), antithrombin III ( 抗凝血酶 III), 

thrombomodulin ( 血栓调节蛋白 )

Signaling mediates responses to damage in a blood vessel:

adjacent endothelial cells are a source of signals that influence platelet aggregation and alter blood flow and clot formation at the affected site.

Role of platelets in hemostasisRelease of vasoconstricting substances

Formation of the "platelet plug"

Promotion of blood clotting

Clot retraction

Clotting factors

Clotting factor SynonymsI fibrinogen 纤维蛋白原II prothrombin 凝血酶原III tissue thromboplastin 组织因子IV Ca2+

V proaccelerin 前加速素易变因子VII proconvertin 前转变素稳定因子VIII antihemophilic factor 抗血友病因子IX plasma thromboplastin component 血浆凝血活酶X Stuart-Prower factorXI plasma thromboplastin antecedent 血浆凝血活酶前质XII contact factor 接触因子XIII fibrin-stabilizing factor 纤维蛋白稳定因子

Blood coagulation

The liver plays a critical role in producing andmodifying blood-borne proteins, including those used in the clottingpathway.

Moreover, bile salts from the liver facilitate the absorption of lipids in the diet, including vitamin K,which is required for the synthesis of prothrombin.

Exploration of the details of the clotting pathway has yielded detailed information about the sequence, only a portion of which is represented here. Note thrombin’s influence in three different directions.

Knowledge that thrombin plays acentral role in clottinghas generated detailedstudies of the possiblepathways resulting inits formation:

the extrinsic pathway is the more important of the two under most circumstances.

Coagulation cascade

3 processes

2 pathways

Tissue factor pathway (extrinsic) Following damage to the blood vessel, endothelium Tissue Factor (TF)

is released, forming a complex with FVII and in so doing, activating it (TF-FVIIa).

TF-FVIIa activates FIX and FX. FVII is itself activated by thrombin, FXIa, plasmin, FXII and FXa. The activation of FXa by TF-FVIIa is almost immediately inhibited by

tissue factor pathway inhibitor (TFPI). FXa and its co-factor FVa form the prothrombinase complex, which

activates prothrombin to thrombin. Thrombin then activates other components of the coagulation cascade,

including FV and FVIII (which activates FXI, which, in turn, activates FIX), and activates and releases FVIII from being bound to vWF.

FVIIIa is the co-factor of FIXa, and together they form the "tenase" complex, which activates FX; and so the cycle continues. ("Tenase" is a contraction of "ten" and the suffix "-ase" used for enzymes.)

Contact activation pathway (intrinsic) The contact activation pathway begins with formation of the

primary complex on collagen by high-molecular-weight kininogen (HMWK), prekallikrein, and FXII (Hageman factor). Prekallikrein is converted to kallikrein and FXII becomes FXIIa.

FXIIa converts FXI into FXIa. Factor XIa activates FIX, which with its co-factor FVIIIa form the

tenase complex, which activates FX to FXa. The minor role that the contact activation pathway has in

initiating clot formation can be illustrated by the fact that patients with severe deficiencies of FXII, HMWK, and prekallikrein do not have a bleeding disorder.

Final common pathway

Thrombin has a large array of functions Its primary role is the conversion of fibrinogen to fibrin, the building block of a

hemostatic plug. In addition, it activates Factors VIII and V and their inhibitor protein C (in the

presence of thrombomodulin), and it activates Factor XIII, which forms covalent bonds that crosslink the fibrin polymers that form from activated monomers.

Following activation by the contact factor or tissue factor pathways, the coagulation cascade is maintained in a prothrombotic state by the continued activation of FVIII and FIX to form the tenase complex, until it is down-regulated by the anticoagulant pathways.

Fibrin Polymerization

Structure of Fibrinogen

A deficiency of a clotting factor can lead to

uncontrolled bleeding.

Vitamin K is a cofactor needed for the synthesis of

factors II, VII, IX, & X in the liver. So a deficiency of

Vitamin K predisposes to bleeding.

Hemophilia & Bolshevik Revolution

http://en.wikipedia.org/wiki/Grigori_Rasputin

http://www.sciencecases.org/hemo/hemo.asp

Rasputin

Serum （血清）

serum = plasma – fibrinogen and

some of the other clotting factors

+ substances released by vascular

endothelial cells and

platelets

Clotting time ( 凝血时间 ) ： 4-12 min

Which of the following statements is correct? A Damaged tissue releases a substance called tissue

fibrinogen, which 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 causes the release of platelet thromboplastin, which has an effect similar to tissue prothrombin

Anticoagulants（抗凝物质）Serine Protease Inhibitor

Antithrombin III （抗凝血酶 III ） : inhibiting all serine proteases of the blood coagulation system, including: thrombin factor IXa, Xa, XIa, XIIa

Protein C system （蛋白 C 系统）Protein C, thrombomodulin, Protein S…

In an uninjured vessel,thrombin bound to thrombomodulin activatesprotein C, which blocks theclotting response.

Tissue factor pathway inhibitor (TFPI) （组织因子途径抑制物）

Heparin （肝素）A polysaccharide produced by the tissue

mast cells and the basophils of circulating blood

Interfering primarily with the action of thrombin after combining with antithrombin III

Fibrinolysis（纤维蛋白溶解）

o 2 processeso Activation of plasminogen

o Degradation of fibrin

o 4 components of plasma fibrinolysis systemo Plasminogen （纤维蛋白溶解酶原）o Plasmin （纤维蛋白溶解酶）o Plasminogen activator

o Plasminogen inhibitor

Following tissue repair, fibrin clots are dissolved in a process mediated by plasmin; synthetic plasminogenactivators can be used immediately after a stroke orheart attack to help dissolve clots and restore blood flow.

o 2 pathways of plasminogen activation

Fibrin Degradation Products (FDP)

o Extrinsic Plasminogen activator

Tissue-type plasminogen activator (tPA)

Urokinase

o Plasminogen inhibitor

Plasminogen activator inhibitor type-1 (PAI-1)

2-antiplasmin

Antithrombin III

Which of the following substances enzymatically causes the polymerization of plasma fibrinogen? A Thromboplastin B Prothrombin C Prothrombin Activator D Thrombin E Phospholipids

Which of the following cases would result in a fatal transfusion reaction? A Donor group A, Host group A B Donor group AB negative, Host group AB

and Rh positive C Donor Rh negative, host Rh positive,

medical history is negative for prior transfusions

D Donor group AB, Host group 0 E Donor group 0, Host group AB

CASEA woman brings her 13-year-old son to the pediatrician's office. The boy's problems go back to the neonatal period, when he bled unduly after circumcision. When his deciduous (baby) teeth first erupted, he bit his lower lip, and the wound oozed for 2 days. As he began to crawl and walk, bruises appeared on his arms and legs. Occasionally he would sustain a nosebleed without having had an obvious injury. By the time he was 3 years of age, his parents became aware that occasionally he would have painful swelling of a joint—a knee, shoulder, wrist, or ankle—but his fingers and toes seemed spared. The joint swelling would be accompanied by exquisite tenderness; the swelling would subside in 2 to 3 days. The patient's mother states that when her son was a baby, she had noted what appeared to be blood in his stool, and the boy tells the pediatrician that twice his urine appeared red for 1 or 2 days.

Anxiously the patient's mother relates that her brother and her maternal uncle both had similar problems and were thought to be "bleeders." There is no further family history of bleeding, and there is no parental consanguinity (i.e., the patient's parents are not blood relatives). Examination of this boy reveals the presence of ecchymoses (bruises) and the inability to fully flex or extend his elbows.

A panel of four tests is ordered, with instructions to extend testing as appropriate. The four tests are a (1) platelet count, (2) prothrombin time, (3) partial thromboplastin time, and (4) bleeding time.

The patient's platelet count was found to be 260,000/ L (normal, 150,000 to 300,000/ L). This finding appears to rule out a paucity or excess of platelets as the cause of bleeding.

1. What is the role of platelets in hemostasis (the control of bleeding)?

2. What purpose is served by drawing blood into a solution of sodium citrate? What is the purpose of adding a solution of calcium chloride? Does the prothrombin time measure the intrinsic or extrinsic pathway of coagulation?

3. What mechanisms might cause the prothrombin time to be abnormally long?

4. With the given data, can you guess in general the site of the clotting abnormality in this patient?

5. Which clotting factors participate in the early steps of the intrinsic pathway of thrombin formation?

6. In reference to the patient's history, is there a discernible pattern in the way the patient's disorder might be inherited?

7. As in the case of the prothrombin time, what mechanisms might be responsible for a long partial thromboplastin time?

8. Diagnosis is made easier because deficiency of certain clotting factors either causes no symptoms or is associated only with much milder bleeding problems than the patient manifests. Which disorders can be set aside on this basis?

9. It is possible that the patient is functionally deficient in one of two clotting factors? Which are these? Can you propose a way to determine which deficiency is present?

10. Had the bleeding time been long, what diagnoses must be considered?

11. How does the bleeding time help to further delineate the diagnosis?

12. The patient's mother then added that her son's former physician had made a diagnosis of classic hemophilia. She asks, "What are the odds that his sister, now 17, is a carrier?"

Thank you for your attention!