what is capsular fluid?
Answers
Explanation:
Summary
1. The cations sodium, potassium, calcium and magnesium are always at a higher concentration in the capsular fluid (perivitelline fluid) of Lymnaea stagnalis and Biomphalaria sudanica than in the bathing medium. The concentration of each ion is a complex function of the concentrations of all ions in the medium and of pH.
2. Typical values for the ratio of capsular concentration to medium concentration for Lymnaea capsules isolated in slightly alkaline water of average hardness are 2·4-5 for monovalent and 18-40 for divalent cations.
3. Lowering the pH of the medium from 8·5 to 4·0 reduces the capsular concentrations of monovalent ions by about 45% and of divalent ions by about 85%.
4. Consideration of the potential difference between the capsular fluid and the medium, and comparison of the monovalent and divalent ion ratios, indicates that a Donnan equilibrium exists across the capsular membrane.
5. On dilution of the medium the above ratios may rise more than tenfold and the potential difference may rise from about 23 mV to above 60 mV (inside negative). It is concluded that the capsular fluid/membrane system buffers the internal cation activities against changes in external cation activities, particularly in the case of calcium.