What is the Difference Between Blood Plasma and Glomerular Filtrate

The main difference between blood plasma and glomerular filtrate is that the blood plasma contains suspended cells, proteins, and large molecules while the glomerular filtrate, generally, contains neither of these.

Blood plasma and glomerular filtrate are two types of fluids that occur in the body. Glomerular filtrate originates from the blood plasma at the glomerulus. Furthermore, blood plasma occurs inside blood vessels while glomerular filtrate occurs inside the Bowman’s capsule.  

Key Areas Covered 

1. What is Blood Plasma
     – Definition, Composition, Importance
2. What is Glomerular Filtrate
     – Definition, Composition, Importance
3. What are the Similarities Between Blood Plasma and Glomerular Filtrate
     – Outline of Common Features
4. What is the Difference Between Blood Plasma and Glomerular Filtrate
     – Comparison of Key Differences

Key Terms 

Blood Cells, Blood Plasma, Bowman’s Capsule, Electrolytes, Glomerular Filtrate, Proteins  

What is Blood Plasma 

Blood plasma is the pale yellow color fluid. In a general sense, it is a type of extracellular fluid (ECF). 93% of the blood plasma is composed of water. Also, it contains dissolved proteins like fibrinogens, globulins, and albumins. Apart from that, it also contains glucose, clotting factors, electrolytes including Na⁺, Ca²⁺, Mg²⁺, HCO^3–, Cl^–, etc., hormones, and carbon dioxide. Functionally, blood plasma serves as the main medium involved in the transportation of excretory products. Also, it maintains the osmotic balance and the concentration of electrolytes in the body.

Figure 1: Blood Plasma

Furthermore, blood plasma contains suspended blood cells including red blood cells, white blood cells, and platelets. Here, the primary function of the red blood cells is to transport oxygen to various parts of the body. White blood cells are the key components of the immune system. Moreover, platelets in the blood plasma are responsible for the blood clotting, which prevents blood loss during injuries.

What is Glomerular Filtrate 

Glomerular filtrate is the fluid that occurs inside the Bowman’s capsule. It generates from blood plasma during the first step of the formation of urine (filtration), which occurs in the glomerulus. The Bowman’s capsule receives blood through the afferent arteriole. Moreover, the hydrostatic pressure inside the glomerular capillaries serves as the main force for the filtration of most of the liquid portion of the blood plasma along with the small molecules suspended in the plasma into the Bowman’s capsule.  

Figure 2: Glomerular Filtrate

Notably, around 99% of the glomerular filtrate contains water. Also, it contains electrolytes. Other small molecules in the blood plasma like glucose and amino acids, hormones, nitrogenous wastes, etc. can also pass into the glomerular filtrate. Generally, glomerular filtrate does not contain large molecules and proteins like hemoglobin, albumin, globulin, etc., which are in the blood plasma. However, around 0.02% of albumin can pass into the glomerular filtrate.  

Similarities Between Blood Plasma and Glomerular Filtrate 

• Blood plasma and glomerular filtrate are two types of fluids found inside separated compartments. 
• Both occur inside the glomerulus, but they are separate. 
• Also, the main component of both types of fluids is water. Furthermore, both of them contain glucose, creatinine, urea, uric acid, and various electrolytes like sodium, potassium, chloride, and bicarbonate ions. 

Difference Between Blood Plasma and Glomerular Filtrate 

Definition 

Blood plasma refers to the pale yellow fluid portion of the blood that contains suspended red and white blood cells and platelets while glomerular filtrate refers to the filtrate that passes from the lumen of the glomerular capillary to the space of Bowman’s capsule. Hence, this is the fundamental difference between blood plasma and glomerular filtrate.

Occurrence 

Another difference between blood plasma and glomerular filtrate is that the blood plasma occurs inside the blood vessels while the glomerular filtrate occurs inside the glomerulus.  

Cells 

Various types of blood cells are suspended in the blood plasma while glomerular filtrate does not contain blood cells. 

Proteins and large Molecules 

Moreover, blood plasma contains suspended proteins and other large molecules while glomerular filtrate does not contain proteins and other large molecules. Thus, this is a main difference between blood plasma and glomerular filtrate.

Conclusion 

Blood plasma is the fluid that occurs inside blood vessels. It contains suspended blood cells, proteins like hemoglobin, albumin, and globulin. On the other hand, the glomerular filtrate is the fluid that occurs inside the glomerulus. Its composition is similar to blood plasma, but it does not contain blood cells, proteins, and other large molecules. Therefore, the main difference between blood plasma and glomerular filtrate is the presence of blood cells, proteins, and other large molecules. 

References:

1. Benjamin, Richard John, and Lisa Swinton Mclaughlin. “Plasma Components: Properties, Differences, and Uses.” Transfusion, vol. 52, 2012, doi:10.1111/j.1537-2995.2012.03622.x.
2. “Boundless Anatomy and Physiology.” Physiology of the Kidneys|Lumen Learning, Lumen, Available Here

Image Courtesy:

1. “Blood vial” By Wheeler Cowperthwaite from Reno, USA – Blood vial (CC BY-SA 2.0) via Commons Wikimedia  
2. “Glomerular Physiology” By Tieum – https://commons.wikimedia.org/wiki/File:PhysiologieGlom%C3%A9rulaire.png (CC BY-SA 4.0) via Commons Wikimedia