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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>

<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 - [[Spleen - Anatomy & Physiology|Spleen]]</h2>

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[[Image:simpdifdiag.jpg|right|thumb|250px|<small><center>A Simple Schematic Diagram of Diffusion Across a Cell Membrane(Courtesy of Mariana Ruiz Villarreal)</center></small>]]

[[Image:LH_Canine_labelled_ventrodorsal_abdominal_organs_radiograph.jpg|150px]]

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 spleen is a major lymphoid and blood filtration organ and is located in the left cranial abdomen. It is responsible for storing and removing [[Erythrocytes - WikiBlood|erythrocytes]] from the blood as well as antigen surveillance of the blood and antibody production.

<p>The spleen develops in association with the digestive system in the dorsal mesogastrium, and as the [[Forestomach - Anatomy & Physiology|stomach]] rotates during development the spleen comes to occupy the left cranial abdomen. Haematopoietic cells in the spleen are derived from the AGM (aorta-gonad-mesonephros) and yolk sac and as the [[Primary Lymphoid Tissue - Anatomy & Physiology|primary lymphoid organs]] become established it becomes populated with [[Lymphocytes - WikiBlood#Types|T and B lymphocytes]].</p>

<p>The spleen lies vertically on the left side of the cranial abdomen. It is attached to the greater curvature of the [[Alimentary - Anatomy & Physiology#Stomach|stomach]] by the gastrosplenic ligament. The spleen is covered in a enclosed in a capsule of fibrous and elastic tissue that extends into the parenchyma as trabeculae.  </p>

<p> The parenchyma is supported by a fine mesh of reticular fibres and is divided into two types of tissue, the red and the white pulp. The red and white pulp are separated by the marginal sinus.</p>

 

[[Spleen - Anatomy & Physiology|Click here to read more]]

[[Diffusion - Physiology|Click here to read more]]

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