University:
Kentucky State University
Course:
BIO 303 | Human Physiology
Academic year:

2021
Views:

252

Pages:

4
Author:

kundgetanufv

Body fluids Lecture 13: Body fluids are distributed in compartments: A. Intracellular compartment: inside the cells of the body (two thirds) B. Extracellular compartment: (one third) it is divided into sub compartments: 1. Inside blood vessels (intravascular compartment )plasma 2. Inside lymphatic vessels 3. Transcellular fluid: fluid found around organs in cavities, examples are: a. Synovial fluid b. Peritoneum fluid c. Pericardium fluid d. Cerebrospinal fluid: found in the CNS e. Pleural fluid 4. Interstitial fluid: fluid found outside the cells and the vessels Rules followed in exchanging fluids: 1. Osmotic pressure causing osmosis 2. Hydrostatic pressure causing filtration 3. Oncotic (colloid osmotic) pressure: Note: the intravascular fluid contains more proteins than the interstitial fluid, but the intracellular fluid contains the highest amount of proteins. So what is the importance of that? Answer: because of the hydrostatic pressure at the level of capillaries (arterial side), filtration of fluids occurs but at the Venous side there is another force attracting back these fluids which is created by proteins (this pressure is called oncotic pressure). What happens if the concentration of proteins in the plasma is decreased? There will be normal filtration but the reabsorption won’t be efficient so some fluid will remain at the level of interstitial fluid causing Edema. Conditions with no protein content in plasma: 1. In nephrotic syndrome: at the level of kidney in this syndrome these is a loss of proteins which is called hyperproteinemia 2. In liver diseases: because the liver is the site for synthesizing proteins * We have high balance of water in the body and this process is related to the sodium homeostasis. How do we lose water? 1. Urine (60%) 2. Feces, sweating  sensible loss of water 3. Evaporation  insensible 4. Breathing Note: breathing and evaporation loss of water equals almost 28% How do we uptake(input) water? 1. Drinking 2. Food 3. Metabolic processes such as burning glucose chemically What organs are involved in the regulatory process? Urinary system, cardiovascular system, endocrine, skin, Aspects of regulation: 1. Osmolality: we have osmoreceptors that sense changes in osmolality and sending signals to the CNS 2. Regulation of extracellular fluid: by sensing the changes in the volume Ex: loss of hypotonic solution  increase in osmolality in the interstitial fluid  attract water leading to cell shrinking .(called dehydration ) Ex2: if someone ingests high amount of pure water  osmolality decreases cells swell . (water intoxication) How to measure the volume of body fluids? By the dilation principle: C1 V1 =C2 V2 **Characteristics of substances that can be used are mentioned in the slides. Measuring the total body fluid volume: We use radioactive water (tritium ) or heavy water (deuterium). Measuring the ECF volume: We use substances that are distributed only in the ECF examples are: 1. Radioactive sodium ( although sodium will be distributed inside the cells but within the first 30 mins only small amount will be distributed so we can ignore its effect )  here we measure the sodium space 2. Inulin  we measure the inulin space Note: the inulin space may or may not equal the sodium space. 3. 125I-iodothalamate 4. Thiosulfate Measuring the ICF volume: The ICF volume= total volume- ECF volume