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What substances are carried in blood plasma?
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Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).
Blood plasma is the straw-colored, liquid portion of blood that serves as a vital transport medium. Composed of 90β92 percent water, it carries a wide array of essential solutes and substances throughout the body.12
Key substances transported in plasma include:
- Proteins: These make up 6β8 percent of plasma and include serum albumin (which maintains osmotic pressure), globulins (involved in transport and immunity), and coagulation proteins like fibrinogen.12
- Electrolytes: Essential ions such as sodium, potassium, chloride, bicarbonate, calcium, and magnesium are critical for maintaining homeostasis.12
- Nutrients and Organic Compounds: Plasma carries glucose, amino acids, vitamins, and lipids (such as cholesterol and triglycerides), often bound to carrier proteins.12
- Hormones: Various hormones, including insulin, thyroxine, and steroid hormones, are secreted into the plasma to reach target organs.12
- Waste Products: Nitrogenous wastes like urea, creatinine, and uric acid are transported to the kidneys for excretion.12
- Other Constituents: Plasma also contains enzymes, antibodies, cytokines, and trace metals like iron and copper.12