B3.2.12 Exchange of substances between tissue fluid and cells in tissues (HL) Notes

Tissue Fluid Enables Cellular Exchange

1. The exchange of substances between tissue fluid and cells is a critical process that ensures cells receive nutrients and oxygen.
2. Simultaneously, waste products are removed for excretion.

Plasma: The Blood’s Transport Medium

1. Plasma makes up 55% of blood and carries nutrients, gases, hormones, and waste.
2. It’s mainly water (90-92%) but also contains:
   1. Water (90%): The major component, acting as a solvent and transport medium.
   2. Plasma Proteins (7%): Includes albumin, globulins, and fibrinogen. These proteins help maintain osmotic pressure, immune defense, and blood clotting.
   3. Nutrients (1%): Glucose, amino acids, and lipids.
   4. Electrolytes: Sodium, potassium, chloride, and calcium, which help regulate fluid balance and nerve function.
   5. Waste Products: Urea, creatinine, and carbon dioxide are carried to excretory organs like the kidneys and lungs.
   6. Hormones: Chemical messengers that regulate body functions.

Tissue Fluid Is The Link Between Blood and Cells

1. Tissue fluid (interstitial fluid) forms when plasma leaks out of capillaries, bathing cells in nutrients and oxygen.
2. It’s similar to plasma but lacks large plasma proteins.
3. The composition of tissue fluid includes:
   1. Water: Makes up most of the tissue fluid and provides a medium for the transport of nutrients and waste.
   2. Nutrients: Such as oxygen, glucose, and fatty acids, which are provided to the cells.
   3. Waste Products: Such as carbon dioxide and urea, which are transported away from the cells.
   4. Electrolytes: Including ions like sodium, potassium, and chloride, which are also present in plasma and maintain osmotic balance.
   5. Proteins (lower concentration): Tissue fluid contains fewer proteins than plasma, as proteins are too large to pass freely through capillary walls. T

Key Differences Between Plasma and Tissue Fluid