What is Fick's law?

Answer 1

Ficks laws (note that there are two of them) are:

Most people are concerned with Fick's first law which relates the diffusive flux to the concentration under the assumption of steady state:

R=D X A Dp / d

R=the rate of diffusion

D=diffusion coefficient, which is a characteristic of the medium and varies exponentially with temperature

A=the surface area

and dC/dx Is the concentration gradient over the diffusion distance

Fick's first law suggests that the rate of diffusion in a given direction across and exchange surface:

1. is directly proportional to the concentration gradient- the steeper the concentration gradient, the faster the rate of diffusion

2. is directly proportional to the surface area- the greater the surface area of a membrane through which diffusion is taking place, the faster the rate of diffusion this is one of the factors which limits cellsize.

3. is inversely proportional to the distance- the rate of diffusion decreases rapidly with distance. diffusion is thus effective only over short distances. this limits cell size.

Fick's second law predicts how diffusion causes the concentration to change with time. It is a partial differential equation which, within the character limitations of Wikianswers, the second law is:

δφ/δt = ▼·(D▼φ)

where

• δ is being used as the symbol for partial differential
• φ is the concentration in dimensions of [(amount of substance) length−3]
• t is time
• · is the "dot product"
• ▼ is the del or gradient operator
• D is is the diffusion coefficient in dimensions of [length2 time−1]

Note that when φ is at steady state, this equation reduces to Fick's first law.

Answer 2

> Amount of marker substance taken up by the organ per unit time.

> Concentration of marker substance in arterial blood supplying the organ.

> Concentration of marker substance in venous blood leaving the organ.