Tissue fluids_etiology_volume regulation_pressure.pptx

Tissue fluids_etiology_volume regulation_pressure.pptx

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  Tissue Fluid
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  • DEFINITION • Tissuefluid is the medium in which cells are bathed. • It is otherwise termed as interstitial fluid. It leads t5o the formation of approximately 20% of extracellular fluid (ECF).
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  • FUNCTIONS OFTISSUE FLUID • Because of the capillary membrane, there is no direct contact particularly between blood and cells. • And, tissue fluid behaves s as a medium for exchange of various substances especially between the cells and blood in the capillary loop. • Oxygen and nutritive substances diffuse from the arterial end of capillary through the tissue fluid and arrive the cells. • Carbon dioxide and waste materials diffuse from the cells into the venous end of capillary via this fluid.
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  • FORMATION OFTISSUE FLUID • Formation of tissue fluid involves two processes: • 1. Filtration. • 2. Reabsorption. • FILTRATION • The formation of tssue fluid takes place with the the process of filtration. • Generally, the blood pressure (also called hydrostatic pressure) in arterial end of the capillary is approximately 30 mm Hg. • This hydrostatic pressure is the driving force or filtration of water and other substances from blood into tissue spaces. • Along the course of the capillary, the pressure falls in a gradsual manner and it is approximately 15 mm Hg at the venous end. • Capillary membrane is not permeable to the large molecules, especially the plasma proteins.
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  • So, theseproteins remain in the blood and exert a pressure termed as oncotic pressure or colloidal osmotic pressure. • It is Approximately 25 mm Hg. Osmotic pressure is constant throughout the circulatory system and it is an opposing force for the filtration of water and other materials particularly from capillary blood into the tissue space. • Whatever it may be, the hydrostatic pressure in the arterial end of the capillary (30 mm Hg) is greater than the osmotic pressure. • And, the net filtration pressure of 5 mm Hg is results in continuous filtration
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  • Starling Hypothesis •Determination of net filtration pressure is dependent on Starling hypothesis. • Starling hypothesis states that the net filtration through capillary membrane is proportional • to the hydrostatic pressure difference across membrane minus the oncotic pressure difference. • These pressures are known as Starling forces • REABSORPTION • Fluid filtered at the arterial end of capillaries is reabsorbed back into the blood at the venous end of capillaries. • Here also, the pressure gradient plays a crucial role. • At the venous end of capillaries, the hydrostatic pressure is less (15 mm Hg) and the oncotic pressure is more (25 mm Hg). • Because of the pressure gradient of 10 mm Hg, the fluid is reabsorbed along with waste materials from the tissue fluid into the capillaries. • About 10% of filtered fluid gains entry into the lymphatic vessels. • Thus, the process of filtration at the arterial end of the capillaries assists in the formation of tissue fluids and the process of reabsorption at the venous end assists in regulating the volume of tissue fluid.
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  • 6. • HarrellBR, Miller S. Abdominal Compartment Syndrome as a Complication of Fluid Resuscitation. Nurs Clin North Am. 2017 Jun;52(2):331-338. [PubMed] • 7. • Cheuvront SN, Kenefick RW, Sollanek KJ, Ely BR, Sawka MN. Water-deficit equation: systematic analysis and improvement. Am J Clin Nutr. 2013 Jan;97(1):79-85. [PubMed] • 8. • Haberal M, Sakallioglu Abali AE, Karakayali H. Fluid management in major burn injuries. Indian J Plast Surg. 2010 Sep;43(Suppl):S29-36. [PMC free article] [PubMed] • 9. • Perikal PJ, Jagannatha AT, Khanapure KS, Furtado SV, Joshi KC, Hegde AS. Extrapontine Myelinolysis and Reversible Parkinsonism After Hyponatremia Correction in a Case of Pituitary Adenoma: Hypopituitarism as a Predisposition for Osmotic Demyelination. World Neurosurg. 2018 Oct;118:304-310. [PubMed] • 10. • Hellerstein S. Fluid and electrolytes: clinical aspects. Pediatr Rev. 1993 Mar;14(3):103-15. [PubMed] • 11. • Meyers RS. Pediatric fluid and electrolyte therapy. J Pediatr Pharmacol Ther. 2009 Oct;14(4):204-11. [PMC free article] [PubMed] • 12. • Taylor SP, Karvetski CH, Templin MA, Heffner AC, Taylor BT. Initial fluid resuscitation following adjusted body weight dosing is associated with improved mortality in obese patients with suspected septic shock. J Crit Care. 2018 Feb;43:7-12. [PubMed]