Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 20 - The Lymphatic System and Lymphoid Organs and Tissues - Review Questions - Page 762: 10

Answer

A high percentage of the human body is water. The amount varies with age, sex and adiposity, For a healthy young adult, about 55-60% of the weight of the body is water--this is much higher in infants. The total body water is usually considered to comprise the following compartments the intracellular fluid (ICF or cytosol) within cells ; the extracellular fluid (ISF, plasma , lymph), and the transcellular fluid --cerebrospinal fluid, synovial fluid, pleural fluid, bile, aqueous humor etc. The fluid of plasma comes from the digestive tract; interstitial fluid is an ultrafiltrate of plasma, and lymph is residual interstitial fluid ( plus fat and some proteins} that is returned to the blood circulation. Total body water is about 40 liters(L); interstitial fluid is about 10.5 liters, and plasma and lymph ( intervascular fluid) amounts to about 3.8 L.

Work Step by Step

The extracellular fluids-- plasma , ISF and lymph-- are similar in composition with a few exceptions: Proteins Plasma has much more proteins (22 mEq/L); for other components of the ECF the protein concentration is about 1.5-2 mEq/L. Lymph is similar in protein content, except in lymphatic vessels that drain the liver, where the protein content rises. ---the protein content of ICF varies between 40-50 mEq/L. Electrolytes: The chief cation of the ECF is sodium(Na+); the chief anion is CL-. This is true in all the ECF fluids --plasma, ISF, and lymph-- though plasma has lower concentration of CL- than ISF does. It is noteworthy that in ICF the major cation is potassium (K+) and the chief anion is HPO4--; also, the amount of protein in ICF is 3X the usual concentration in plasma. Nutrients: glucose, lactic acid, amino acids, iron, vitamins Lipids : cholesterol, fatty acids, phospholipids Dissolved gases: oxygen carbon dioxide, nitrogen Nitrogenous wastes--urea, uric acid, creatinine, creatine ammonia Lymph leaving the upper and lower limbs is a clear fluid , while plasma usually has a light straw color. However, lymph leaving the liver has higher than usual concentrations of proteins. As mentioned earlier, the chyle --of the lacteal lymphatics that drain the digestive tract villi-- is whitish or milky in appearance because of the lipid substances --fatty acids and emulsified fats in the lymph fluid. Lymph is not exactly equivalent to plasma. Like blood, lymph has cells --lymphocytes, macrophages, dendritic cells and reticular cells. Lymph in lymphatic vessels that drain lymph nodes directly has large numbers of lymphocytes. Lymphatic fluid is very similar in compostion to plasma except for the higher plasma concentratiion of proteins==albumins, globulins, fibrinogens, clotting factors. prothrombin
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