Difference between revisions of "Veterinary Education Online"

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<h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Article of the Week - [[Stomach and Abomasum - Anatomy & Physiology|The Stomach of the Ruminant]]</h2>
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<h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Article of the Week - [[Diffusion - Physiology]]</h2>
 
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[[Image:Abdomen development young cow.jpg|thumb|right|150px|Abdominal development of a young cow - Copyright Prof.Pat Mccarthy]]
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Gases or liquids can be unevenly distributed between two areas. If one area has a higher concentration than the other then the differance between these two areas is termed the concentration gradient. The equality is then corrected by the movement of the molecules down this so called gradient from the region of high concentration to that of low. This process is passive as the molecules do not have to be forced to do this and it is reffered to as diffusion.  
  
The ruminant stomach is composed of 4 separate compartments. Food passes first into the [[The Rumen - Anatomy & Physiology|rumen]], then [[The Reticulum - Anatomy & Physiology|reticulum]], [[The Omasum - Anatomy & Physiology|omasum]] and finally into the [[The Abomasum - Anatomy & Physiology|abomasum]] before entering the [[Duodenum - Anatomy & Physiology|duodenum]]. The first three compartments are adapted to digest complex carbohydrates with the aid of microorganisms which produce [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]] - the major energy source of ruminants. The last compartments, the [[The Abomasum - Anatomy & Physiology|abomasum]] resembles the simple [[Forestomach - Anatomy & Physiology|monogastric stomach]] in structure and function.
 
  
The microorganisms in the ruminant stomach also synthesise all of the B vitamins, vitamin C and vitamin K. Vitamin synthesis in the rumen is sufficient for growth and maintenance. Only vitamins E, D and A should be provided in the ruminant diet. Under normal conditions, ruminants will not require B vitamins added in the diet. Cobalt is needed for vitamin B12 synthesis and so cobalt should be provided in the diet or vitamin B12 injected directly into the bloodstream. In stress conditions, vitamin B3 (Niacin) and vitamin B1 (Thiamine) may also need to be provided in the diet....
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This works by the random thermal movement of molecules. If there is a gas present in an air tight room and then a door is opened into the next room where a lower concentration of the same gas is present the laws of probability state that more of the randomly moving molecules will escape through the door from the area of high concentration than will escape back through the door from the area of low and that eventually the concentrations in both rooms with be approximately the same. The net movement therefore will be from the room with a high concentration to that of a low concentration.  
  
[[Stomach and Abomasum - Anatomy & Physiology|Click here to read more]]
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'''Ficks Law'''
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A Simple Schematic Diagram of Diffusion Across a Cell Membrane(Courtesy of Mariana Ruiz Villarreal) Q = DA((C1 - C2) ÷ L)
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Q = the transport rate of a substance by diffusion
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D = The diffusion coefficient
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A = The cross sectional area which the substance is to diffuse across
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C1 C2 = The concentrations in the two areas 
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L = distance separating the two areas
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Ficks law demonstrates that the rate of diffusion can be maximised by increasing the area over which diffusion can occur, minimising the distance it has to occur over and increasing the gradient it occurs along. In the body it tends to be the former two which are taken into account when adapting surfaces for diffusion to occur over.
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[[Diffusion - Physiology|Click here to read more]]
 
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Revision as of 08:36, 21 October 2008

Welcome to WikiVet,
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Article of the Week - Diffusion - Physiology

Gases or liquids can be unevenly distributed between two areas. If one area has a higher concentration than the other then the differance between these two areas is termed the concentration gradient. The equality is then corrected by the movement of the molecules down this so called gradient from the region of high concentration to that of low. This process is passive as the molecules do not have to be forced to do this and it is reffered to as diffusion.


This works by the random thermal movement of molecules. If there is a gas present in an air tight room and then a door is opened into the next room where a lower concentration of the same gas is present the laws of probability state that more of the randomly moving molecules will escape through the door from the area of high concentration than will escape back through the door from the area of low and that eventually the concentrations in both rooms with be approximately the same. The net movement therefore will be from the room with a high concentration to that of a low concentration.


Ficks Law

A Simple Schematic Diagram of Diffusion Across a Cell Membrane(Courtesy of Mariana Ruiz Villarreal) Q = DA((C1 - C2) ÷ L)

Q = the transport rate of a substance by diffusion 
D = The diffusion coefficient 
A = The cross sectional area which the substance is to diffuse across 
C1 C2 = The concentrations in the two areas  
L = distance separating the two areas

Ficks law demonstrates that the rate of diffusion can be maximised by increasing the area over which diffusion can occur, minimising the distance it has to occur over and increasing the gradient it occurs along. In the body it tends to be the former two which are taken into account when adapting surfaces for diffusion to occur over.

Click here to read more


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