Measurement of Body Fluid Compartments

1. بسم الله الرحمن الرحيم ﴿و ما أوتيتم من العلم إلا قليلا﴾ صدق الله العظيم الاسراء اية 58

2. BIOPHYSICS By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology

3. Biophysics , Abdelaziz Hussein

4. Measurement of volumes of Body Fluid Compartments Principle of measurement: • A known amount of a dye or indicator is injected into the body. • Then the dye concentration in that compartment is measured. • The compartment volume is calculated as follow:

5. 5 gm Concentration 10 mg/ml Volume = 5000/10 = 500 ml

6. Measurement of volumes of Body Fluid Compartments Characters of dye : • Not toxic. • Rapidly and evenly distributed throughout the nominated compartment • Not metabolized. • Not rapidly excreted. • Easily measured.

7. Measurement of Total Body Water Measurement of total body water: • Can be measured by Deutrium oxide (D2O, heavy water), Tritium oxide and Aminopyrine • They are distributed ICF and ECF Problem: • Amount of D2O injected = 4 mg • Plasma concentration = 0.01 mg/dl. 4 mg Volume = = 40 Liters 0.01 x 10

8. Measurement of ECF and ICF Volumes Measurement of ECF volume: • Can be measured by Inulin (more accurate), Mannitol and Sucrose • They are distributed ECF only Measurement of ICF volume : • Not directly measured • But measured by the following formula; ICF = Total body water – ECF

9. Measurement of Plasma Volume Measurement of plasma volume: • Can be measured by Evans blue dye (more common) or radioactive iodine bound to plasma proteins • They are distributed only in vascular part of ECF Measurement of ISF : • Cannot be measured directly but measured by • ISF= ECF – plasma volume

10. Measurement of Blood Volume Measurement of blood volume: Plasma volume Blood volume = 1- Haematocrit Measurement of RBCs volume : • RBCs volume = Blood volume – Plasma volume • Can be measured directly as chromium (51Cr), iron (59Fe ) and phosphorus (32P)

11. Total Body Water

12. Total Body Water • In adult men is about 60% of body weight • In adult women is about 50% of body weight (much fat in their bodies) . • ↑ % of fat in the body →↓ % of water. • In infants is more than 70%,so water loss leads to rapid dehydration. • 97% in embryo at 6 weeks • In old age the water content is decreased (45%)

15. Functions of Body Water

17. Functions of Body Water • Required for all chemical reactions inside the body. • Powerful solvent that dissolve various substances to make them accessible to body. • So, it acts as a vehicle that carries nutrients and gases to the body cells and removes wastes from them. 3. Moistens tissues such as mouth, eyes and nose, and lubricates joints.

18. Functions of Body Water 4. Regulation of body temperature as water has a high latent heat of evaporation (each gram H2O needs 0.58 ◦C to evaporate from the body). 5. Helps in osmotic equilibrium between various body compartments.

19. Functions of Body Water 6. Formation of digestive secretions and action of enzymes 7. Absorption at the venous end of capillaries, GIT and kidney 8. Filtration at arterial end of capillaries and glomeruli.

20. Functions of Body Water 9. Excretion at GIT, kidney and skin. 10. Exchange at capillary membrane, alveolar membrane and cell membrane. 11. Refractive medium in the eye

21. Water Balance

22. Water Balance Definition: • Body water is kept constant by adjusting water input and water output

23. Control of Water Input ↓ blood volume (Hypovolaemia) Thirst Center Angiotensin II Thirst sensation ↑ plasma osmolarity (Hypertonicity) Increased water intake ↑ plasma osmolarity ↓ blood volume

24. Control of Water Output ↓ blood volume (Hypovolaemia) Posterior pituitary ADH secretion Angiotensin II ↑ plasma osmolarity (Hypertonicity) ↑ plasma osmolarity ↓ blood volume ↓ Urine volume

25. Homeostasis Definition: • Are the mechanisms that keep the internal environment constant Significance: • This is very important as the cells lie in the internal environment →keeps normal functions of cells as: • Body water • Body temperature • Arterial blood Pressure • Composition of ECF as regard, Ions, pH and glucose

26. Homeostasis Range: • There is a narrow range of change in homeostasis; more than this range the cell function is greatly affected Body systems: • All body systems performs their functions to maintain homeostasis • Body functions regulated by; • A) Nervous mechanism by nervous system (rapid) • B) Endocrine system: by hormones (slow)

27. AS Biology, Cell membranes and Transport

28. Homeostasis • Homeostasis is characterized by feedback mechanism • Feedback mechanisms are the mechanisms that keep the system constant • They are 2 types : • A) Negative feedback: the response is opposite to the stimulus. • B) Positive feedback: the response in the same direction of the stimulus .

29. Homeostasis • A) Negative feedback: the response is opposite to the stimulus • These mechanisms keep the system constant and the response inhibits the stimulus. a) ↑ CO2→ hyperventilation → washout of excess CO2→ ↓ CO2 to normal. b) ↑ blood glucose→↑ insulin secretion → ↑ glucose utilization → ↓ glucose level to normal. c)↑ arterial blood pressure (ABP)→ reflex vasodilatation and ↓ heart rate → ↓ arterial blood pressure back to normal.

32. Homeostasis • A) Positive feedback: the response is in the same direction of the stimulus • the response increases the stimulus • a) Death cycles→ fatal cycles leads to death

34. Homeostasis • A) Positive feedback: b) Some positive feedback cycles are usefule.g. A) During labour: • Cervical dilatation→↑ es the uterine contractions→ descent of baby → more cervical dilatation → more uterine contractions → more descent of baby, till complete labor. B) Blood clotting

36. Biophysics , Abdelaziz Hussein