An echocardiogram--or echo--is a diagnostic test used to take pictures of the heart and surrounding blood vessels.It is more detailed than an X-ray and uses sound waves versus radiation.n echocardiogram--or echo--is a diagnostic test used to take pictures of the heart and surrounding blood vessels.
The term simple diffusion refers to a process whereby a substance passes through a membrane without the aid of an intermediary such as a integral membrane protein. The force that drives the substance from one side of the membrane to the other is the force of diffusion. In order for substances to pass through a cell membrane by simple diffusion it must penetrate the hydrophobic core of the phospholipid bilayer. The types of molecules that can do this are themselves substantially hydrophobic in nature such as carbon dioxide, oxygen or ethanol. In the figure below the green triangle indicates a concentration gradient of carbon dioxide. The blue arrow indicates the direction of net flow of carbon dioxide.
Diffusion. Dissolved substances have to pass through the cell membrane to get into or out of a cell. Diffusion is one of the processes that allows this to happen. Diffusion diffusion: The movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration occurs when particles spread. They move from a region where they are in high concentration to a region where they are in low concentration. Diffusion happens when the particles are free to move. This is true in gases and for particles dissolved in solutions. Particles diffuse down a concentration gradient, from an area of high concentration to an area of low concentration.