Blood Plasma Composition and Properties

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Questions and Answers

What percentage of body weight is the normal volume of plasma?

10%

5% (correct)

15%

What is the result of allowing whole blood to clot and then removing the clot?

Whole blood

Plasma

Platelets

Serum (correct)

What is the primary function of plasma proteins in terms of blood pressure?

Reducing blood pressure

Increasing blood pressure

Maintaining osmotic pressure (correct)

Regulating body temperature

What is the term for the process of stopping bleeding while maintaining blood in a fluid form?

Hemostasis Signup and view all the answers

What is the function of plasma proteins in terms of pH?

Existing in an anionic form Signup and view all the answers

What is the result of platelet breakdown during clotting?

Increased serotonin levels Signup and view all the answers

What is a unique characteristic of lymph after a meal?

It has a high fat content, making it milky in appearance. Signup and view all the answers

What is the primary mechanism of contraction in vascular smooth muscle?

Myosin light chain mechanism. Signup and view all the answers

What is the primary function of endothelial cells?

To respond to flow changes and circulating substances. Signup and view all the answers

What is the typical protein content of lymph?

Lower than plasma. Signup and view all the answers

What type of channels are present in the membranes of vascular smooth muscle cells?

Various types of K+, Ca2+, and Cl− channels. Signup and view all the answers

What is the role of endothelial cells in the circulation?

To constitute a large and important organ. Signup and view all the answers

What is the significance of the latch bridge mechanism in vascular smooth muscle?

It produces prolonged contractions. Signup and view all the answers

Where do lymphocytes primarily enter the circulation?

Through the lymphatics. Signup and view all the answers

What is the primary function of thrombomodulin in the blood clotting process?

Forming a complex with thrombin to become an anticoagulant Signup and view all the answers

Which of the following statements is true about fibrin?

Fibrin is an insoluble protein that is formed from fibrinogen Signup and view all the answers

What is the function of antithrombin III in the blood clotting process?

Inhibiting thrombin and preventing clot formation Signup and view all the answers

What is the role of Ca2+ in the blood clotting process?

Required for nearly all steps in clot formation Signup and view all the answers

What is the function of plasmin in the blood clotting process?

Lysing fibrin and fibrinogen Signup and view all the answers

What is the role of platelet receptors in the blood clotting process?

Binding to collagen and releasing serotonin and TXA2 Signup and view all the answers

What is the function of heparin in the blood clotting process?

Facilitating the binding of antithrombin III to thrombin Signup and view all the answers

What is the function of prostacyclin in the blood clotting process?

Inhibiting platelet aggregation Signup and view all the answers

Study Notes

Blood Plasma

Plasma is a fluid of the blood that is a solution containing ions, inorganic molecules, and organic molecules.
It aids in the supply or removal of substances to or from various parts of the body.
Normal volume of plasma is 5% of body weight (approximately 3500ml in a 70kg person).
Plasma clots when outside the body, but remains fluid if an anticoagulant is added.
Serum is plasma without fibrinogen, clotting factors II, V, and VIII, and has a higher serotonin content due to platelets broken down during clotting.

Plasma Proteins

Plasma proteins include albumins, globulins, and fibrinogen.
These proteins are large and do not pass through capillary pores.
They exert a capillary osmotic pressure of approximately 25mmHg, pulling water into the blood.
They are responsible for about 15% of blood buffering power.
In plasma, these proteins are in an anionic form (COO-) at pH 7.4.
They have specific functions such as antibodies and clotting factors, and nonspecific functions as carriers for hormones, solutes, and drugs.

Hemostasis

Hemostasis is the process of stopping bleeding while maintaining blood in a fluid form.
It involves a balance between coagulation and anticoagulation.
Vascular injury leads to bleeding, and the response involves vasoconstriction, platelet aggregation, and clot formation.
Endothelial damage exposes collagen, leading to platelet binding, serotonin release, and vascular constriction.
Platelets aggregate and form a hemostatic plug, covering small punctures.
Tissue releases thromboplastin, activating the clotting mechanism and forming fibrin.

Clotting Mechanism

Fibrinogen is converted to fibrin monomers by thrombin, and then polymerizes to form fibrin.
Fibrin is initially a loose mesh that is stabilized by factor XIII.
Most steps in clot formation require Ca2+.
Thrombin is a serine protease that converts fibrinogen to fibrin, and activates platelets, endothelial cells, and WBCs.

Clotting vs Anticlotting

Coagulants include TXA2, which aggregates platelets.
Anticoagulants include PGI2, which is anti-aggregating, and antithrombin III, which binds and inactivates thrombin.
Fibrinolytics, such as plasmin, break down fibrin and fibrinogen.

Thrombomodulin

Thrombomodulin binds thrombin, forming a thrombin-thrombomodulin complex.
The complex becomes an anticoagulant.

Plasmin (Fibrinolysin)

Plasmin is the active form of plasminogen, a plasma protein.
It breaks down fibrin and fibrinogen, forming FDP, which inhibits thrombin.

Lymph

Lymph is tissue fluid that enters the lymphatic vessels.
It drains into the venous blood via the thoracic and right lymphatic ducts.
Lymph contains clotting factors and clots on standing in vitro.
It has a lower protein content than plasma (approximately 7g/dL).
Lymph protein content varies with the region from which it drains.
Water-insoluble fats are absorbed from the intestine into the lymphatics, and the lymph in the thoracic duct after a meal is milky due to its high fat content.

Structural Features of the Circulation

Two major cell types make up the blood vessels: endothelium and vascular smooth muscle.
Endothelial cells respond to flow changes, stretch, and various circulating substances, and secrete growth regulators and vasoactive substances.
Vascular smooth muscle cells have K+, Ca2+, and Cl- channels, and contraction is produced primarily by the myosin light chain mechanism.
They undergo prolonged contractions that determine vascular tone.

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Description

This quiz covers the composition and properties of plasma, including the substances it contains and its role in the body. It also explains the differences between plasma and serum.