Did you know?

[Doctor Ali]

I'm opening this thread in terms for educational purposes; particular for USMLE Step 1. Everyone is welcome to write, share, comment, and/or give a thought in terms of Medical Education. Again this thread is meant for MEDICAL EDUCATION - NOT meant for thrashing or bashing each. This is for Medical Education Thread and I'm asking to keep it as clean as it suppose to be. When someone wants to start a new topic, it would be a good idea to start with "Did you know?" and from there, start discussing. This is meant to HELP people around for Step 1. All the best!!!!!!

[soniaa]

Did you know?



Total body water (TBW) is approximately 60% of body weight. The percentage of TBW is highest in newborns and adult males; lowest in adult females and in adults with a large amount of adipose tissue. The TBW is broken down into Intracellular Fluid and Extracellular Fluid.


Intracellular Fluid (ICF) is two - thirds of Total Body Water (TBW). That would be 40%. The major cations of ICF are K+ and Mg2+. The major anions of ICF are protein and organic phosphates such as Adenosine triphosphate (ATP), Adenosine diphosphate (ADP) and Adenosine monophosphate (AMP).


Extracellular Fluid (ECF) is one - third of Total Body Water (TBW). That would be 20%. The major cation of ECF is Na+. The major anions of ECF are Cl- and HCO3-. Now, ECF is further broken down into plasma and interstitial fluid.


Plasma is one - fourth of the ECF, which is also one - twelfth of TBW. That would be 5%. The major plasma proteins are albumin and globulins.


Interstitial fluid is three - fourth of the ECF, which is also one - fourth of TBW. That would be 15%. The composition of interstitial fluid is the same as that of plasma except that it has little protein. Thus, interstitial fluid is an ultrafiltrate of plasma.




To summarize:


TBW - 60% - Broken down into ICF and ECF

ICF - 40%

ECF - 20% - Broken down into Interstitial fluid and plasma

Interstitial fluid is 15%

plasma is 5%

Blood is Plasma right ?

[houmd]

Blood plasma is the yellow liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells).

per wiki


Essentially its the liquid medium that suspends the RBCs, WBCs, & other

[Doctor Ali]

Blood is Plasma right ?

Blood plasma is the yellow liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells).

per wiki


Essentially its the liquid medium that suspends the RBCs, WBCs, & other

I will clarify this one. Houmd is correct based on what he/she had said. Now to clarify it; Blood is not plasma. Blood is broken down into components and one of the component is plasma. Approximately 55 percent of blood is plasma, a straw-colored clear liquid. The liquid plasma carries the solid cells and the platelets which help blood clot. Without blood platelets, you would bleed to death. When the human body loses a little bit of blood through a minor wound, the platelets cause the blood to clot so that the bleeding stops.

Plasma is a clear yellowish liquid that forms the fluid portion of blood and lymph. Plasma transports red and white blood cells and platelets throughout the body. It also delivers nutrients to the body's millions of cells and picks up cell waste products. Plasma is composed chiefly of water. This watery solution contains small amounts of minerals, salt, sugar (glucose), fats, amino acids, hormones, enzymes, dissolved gases, wastes like urea, and several proteins.




The other components of Blood is RBCs - 45%, WBCs - 0.1%, and Platelets - 0.17%. These make up approximately 45% of the blood.




So yeah, Blood is NOT plasma. Plasma is a component of the Blood. Hope this clears up.

[Doctor Ali]

Did you know?

Here's how Blood is broken down.

[Doctor Ali]

Did you know?


I just figured out how to post images in terms of educational. That been said, I will now post images of Maltose and Trehalose. Remember, that these two compounds breaks down into two molecules of glucose. The only difference is how they are arranged.

[Doctor Ali]

Did you know?


This is Maltose.

[Doctor Ali]

Did you know?


This is Trehalose.

[windsorstudent]

Remember that when studying Physiology there are two questions you must ask yourself on every single topic in order to really understand the material.

1. What is the concept behind this? Understanding the concept, NOT MEMORIZATION, will help you to do well in all aspects of physiology. When it comes to physio, you usually wont ever see the same question twice, but the concepts will repeat themselves, if you understand the underlying concepts then you will learn physio properly

2. Why is this important? If you can correlate any physiological event to clinical importance then it is going to stick in your brain much MUCH easier than if you were to just read it and try to remember it for an exam. For example, I could talk all day about the action potential being transmitted through the Neuromuscular junction, but if I don't correlate it to something like Myasthenia Gravis then I'm not going to truly understand how it could have a clinical importance. There is a reason they teach you the things they do, always try to find that reason.

In terms of the Left Ventricle

Concept

When you think of preload think of End Diastolic Volume (EDV). Thus the preload is related to the amount of volume placed into the left ventricle just prior to contraction. This becomes much more important later when discussing heart failure.

When you think of afterload, think more in terms of pressure. This is the force of pressure which the ventricle must pump to expel its contents passed the aortic valve. Thus, afterload is directly related to the aortic pressure.

Importance

The normal patient should have an ejection fraction (% of volume expelled from the Left Ventricle) of approximately 0.6 = 60%.

If for any reason the afterload (pressure) were to increase (eg. untreated hypertension due to a billion possible reasons) then it increases the force needed by the ventricle to pump out that same 60% of volume, making the heart work harder for the same amount.

When the ventricle must work harder it will undergo several possible adaptive mechanisms in order to try and restore its homeostatic level of 60%. One of those mechanisms is by hypertrophy (remember the heart is just a giant muscle & can hypertrophy similar to skeletal muscle). By undergoing hypertrophy the heart will increase its contraction strength but at the same time shrink the available space within the left ventricle for volume to occupy. Thus the cardiac output (CO) will decrease and the tissues will receive less blood (which correlates to the oxygen they receive).

Another problem that correlates with the above is based on the concept of the Frank-Starling Law. In a dummy-downed version it simply states that the heart will attempt to pump out any volume it receives, hence if the heart receives more volume, it will attempt to pump out more volume. If for some reason the preload increases within the left ventricle, the heart will stretch out its walls and increase contraction force due to Frank-Starling Forces. If this volume becomes too much, and the ventricle stretches too much, then again the heart will undergo adaptive changes to try and compensate by undergoing hypertrophy. This (again) will increase the contraction force at the expense of the volume available for ejection, and thus create a vicious circle of growth and hypoxia to the tissues. Hence why the main compaint in patients with heart failure is shortness of breath (SOB)

There is actually quite a bit more but I think I'll let you look up the rest.

Thank you. I appreciate your response and feedback.

How does decreasing afterload increase the stroke volume? If the pressure the ventricle must pump to push the blood into the aorta decreases how does that increase the amount of volume of the blood being pumped into the aorta? Shouldn't it decrease the amount of volume of the blood because there is less pressure to push blood through the aorta?

[McNasty]

afterload is the pressure/resistance the left ventricle must push AGAINST to get blood into the aorta(stroke volume), so if afterload is decreased it becomes easier for the LV which increases stroke volume

[houmd]

afterload is the pressure/resistance the left ventricle must push AGAINST to get blood into the aorta(stroke volume), so if afterload is decreased it becomes easier for the LV which increases stroke volume

McNasty's clarification is exactly correct