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Blood: Plasma

Blood: Plasma

Author: Aaron Mullally

- know what plasma is

- know what the classes of plasma proteins are and their functions

- know where the plasma proteins are manufactured

- know what the other materials in plasma are

This packet will cover one of the two major components of blood: plasma.

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Plasma Overview

There are two major components that make up blood, plasma and the formed elements. Plasma is essentially the liquid/water portion of blood with all of the non-living components mixed within it. The formed elements are cells; erythrocytes (red blood cells, RBC's), leukocytes (white blood cells, WBC's), and thrombocytes (platelets). This particular packet will focus on plasma and the next ones will cover the formed elements.

Blood is about 55% plasma and 45% formed elements. Plasma levels can vary and change dramatically throughout the day based on how hydrated you are, how active you are and hormonal changes in our physiology. Remember that plasma is where we get sweat from, we circulate blood to sweat glands and the filter it out and excrete it onto the surface of our skin. This is dangerous if we don't correct this because if our plasma levels drop our overall blood volume drops. This will effect blood flow and blood pressure and the heart's ability to circulate blood properly.

One of the most important and abundant components of plasma are the plasma proteins. There are three major classes of plasma proteins: albumin, globulins and fibrinogen. *By weight people have about 7.35 g/dL or 73.5 g/L. Remember that the average person has about 5L of blood within them, so this would total out to 367.5 g or .8 lbs (13 oz). We have almost a pound of protein in our blood! The three proteins all have thier own unique rolls and are all equally important in keeping us healthy.

*Albumin is the most abundant plasma protein, making up about 60% of the total plasma protein concentration (4.41 g/dL or 44.1 g/L or 220.5 g/person). Albumin's main role is the maintenane of normal water levels or plasma colloid osmotic pressure (PCOP). Remember that water and proteins are strongly attracted to one another. A good way to think of this concept is that albumin exerts a strong pulling force on water. Albumin is too large to escape the blood stream to the tissues so what it does is pull excessive water out of the tissues and back into the blood stream. Remember that albumin is manufactured in the liver and to make proteins you need to consume adequate amounts.

If children are severely malnourished they may develop a condition known as kwashiorkor. Children with kwashiorkor have a very distinct look to them; very thin limbs and large distended abdomens (on average). This, like most other conditions, are multifactoral or have many causes. It's not just protein deficiency with these children, studies have shown that a lack of antioxidants and other essential nutrients (carbs and fats) contribute to this.

In order for the liver to manufacture albumin it not only needs the necessary amino acids but needs energy (carbs and fats). If the liver cannot properly manufacture albumin then there will be a drop in PCOP. This will cause water to build up in the tissue spaces of the child, especially in the abdomen. The limbs look skiny because if the body is starved, especially of proteins, it will catabolize (break down) itself. The best source of protein is meat i.e. skeletal muscle.  This is a conditoin that can be corrected if treated early enough. You just get calories and proteins into the starving child.

Globulins are basically antibodies, and remember that antibodies are important for recognizing foreign antigens (specific immunity). These are not manufactured in the liver, these are manufactured by specialized B cells called plasma cells. I will talk about these more when we cover the immune system.

The other main plasma protein is fibronogen which is a precursor to fibrin. Fibrinogen is very important in the process of forming a clot and will also be discussed later on.

*Pagana, and Timothy J. Pagana. Diagnostic and Labratory Test Reference. St Louis: Elsevier. 2009 Print

Source: Mind of Aaron

Plasma Overview

This video will discuss the composition of plasma and the functions of plasma.

Source: Self made

Kwashiorkor Overview

This video gives a very visual presentation of what kwashiorkor is and how it looks. Just a warning the images in this video are graphic and real, so keep this in your mind before you watch it.


Source: Self made