Cardiovascular System: Blood

General Properties of Blood

Volume in adult body•Female = 4 -5 liters•Male = 5 – 6 liters

pH = 7.35 to 7.45

Temp = 38 oC

100.4 oF

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Hematocrit

Hematocrit

= percent volume

of whole blood

occupied by RBC

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Erythrocytes or Red Blood Cells•No nucleus•Life span = about 120 days•Average Count

•Male = 5.4 million / mm3 (μL)•Female = 4.8 million / mm3 (μL)

•Production called erythropoiesis•Takes about 4 days •Rate = 2 to 3 million per second !

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Erythrocytes on the tip of a hypodermic needle

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HemoglobinGlobin = one of four protein chains

Heme = one of four nonprotein parts with an Fe++ at their center that binds with O2 for transport

About 280 million hemoglobin molecules per RBC

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What kind of feedback system?

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Recycling Iron•On average about 26 mg of Fe+2 is used to make new hemoglobin per day•Body only requires about 1-2 mg per day from diet to replace Fe+2 lost in kidney & GI tract

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Hemoglobin Recycling•Iron•Amino Acids from globin proteins

Leukocytes or White Blood Cells•5,000 to 10,000 / mm3 (μL)

Compared to about 5 million for RBC

Granulocytes•Eosinophils•Basophils•Neutrophils

Agranulocytes•Monocytes•Lymphocytes

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Protection against foreign invaders in body

•Neutrophils – phagocytosis

•Eosinophils – phagocytosis

•Basophils – release histamine & heparin

•Lymphocytes – produce immune response to remove foreign antigens

•Monocytes – differentiate into macrophages

(large phagocytes)

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Platelets (Thrombocytes)

•Not really cells, but fragments of a larger cell called a megakaryocyte

•Average 250,000 / mm3 (μL)

•Play a major role in hemostasis or stopping bleeding

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Hemostasis

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Vascular Spasm

Vascular spasm is vasoconstriction of a damaged vessel to stop or slow flow of blood for 20 to 30 minutes to

“buy time” for other mechanisms to start working

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Platelet Plug FormationPlatelet Adhesion = platelets stick to exposed collagen

Platelet Aggregation = platelets stick to each other & build up a mass called a platelet plug

Platelet Activation = platelets develop cytoplasmic processes (pseudopods) & degranulate (exocytosis of granule contents)

Platelet Activation: Degranulation

Granules contain:• ADP = primary stimulus for platelet aggregation &

activation

• Thromboxane A2 = stimulates aggregation, degranulation, & vasoconstriction

• Serotonin = stimulates vasoconstriction• Platelet derived growth factors (PDGF) = promote

division of endothelia, smooth muscle & fibroblasts• Ca++ = increases local supply

= POSITIVE FEEDBACK LOOP

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CoagulationThree Basic Stages:

1) Form Prothrombin Activator

• Extrinsic pathway

• Intrinsic pathway

2) Form Thrombin

3) Form Fibrin

Clot Retraction

• Platelets contract and pull on fibrin strands

• Clot becomes denser & stronger

• Pulls edges of damaged vessel together

• Squeezes out serum

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Fibrinolysis

Plasmin activated by;•Factor XII•Plasmin•Thrombin•Tissue Plasminogen Activator (t-PA)

To Clot or Not to Clot• Thrombin diluted by blood

• Fibrin inactivates most of thrombin at wound

• Liver removes active clotting factors from

blood (leaves inactive factors)

• Anticoagulants;

Antithrombin from liver inactivates thrombin

Heparin from mast cells & basophils helps

prevent coagulation