body fluid compartments.pdf

BODY FLUID COMPARTMENT Dr. Farah Abdulhussein (F.I.C.M.S path., MSc. Micro., M.B.Ch.B) ALkafeel University/ College of Medicine 15/4/2024 1 By the end of this lecture, the students should be able to: 1-...

BODY FLUID COMPARTMENT Dr. Farah Abdulhussein (F.I.C.M.S path., MSc. Micro., M.B.Ch.B) ALkafeel University/ College of Medicine 15/4/2024 1 By the end of this lecture, the students should be able to: 1- Recognize the types of body fluid compartments with their percentages. 2- Know the percentage of electrolytes ,their distribution, and their functions. 3- Describe the fluid intake and output during steady state conditions. 4- Identify the problems that occur due to disturbances of fluids volume and its constituents. Email :[email protected] Website :http://Alkafeel.edu.iq  INTRODUCTION - The maintenance of a relatively constant volume and a stable composition of the body fluids is essential for homeostasis. Some of the most common and important problems in clinical medicine arise because of abnormalities in the control systems that maintain this relative constancy of the body fluids. - The relative constancy of the body fluids is remarkable because there is continuous exchange of fluid and solutes with the external environment, as well as within the different body compartments. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 3  BODY FLUID COMPARTMENTS The total body fluid is distributed mainly between two compartments: - Extracellular fluid. - Intracellular fluid. 1- The extracellular fluid : All the fluids outside the cells are collectively called the extracellular fluid which is divided into the interstitial fluid , the blood plasma and small compartment of fluid that is referred to as transcellular fluid (this compartment includes fluid in the synovial, peritoneal, pericardial, and intraocular spaces, as well as the cerebrospinal fluid). The total body water (TBW): is about 60 percent of the body weight, or about 42 liters. In a 70-kilogram adult man, the extracellular fluids account for about 20 percent of the body weight, or about 14 liters. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 4  EXTRACELLULAR FLUID COMPARTMENT - The two largest compartments of the extracellular fluid are the interstitial fluid, which makes up more than three fourths (11 liters) of the extracellular fluid, and the plasma, which makes up almost one fourth of the extracellular fluid, or about 3 liters. - The plasma is the non cellular part of the blood; it exchanges substances continuously with the interstitial fluid through the pores of the capillary membranes. - These pores are highly permeable to almost all solutes in the extracellular fluid except the proteins. Therefore, the extracellular fluids are constantly mixing, so the plasma and interstitial fluids have about the same composition except for proteins, which have a higher concentration in the plasma. - transcellular fluids together constitute about 1 to 2 liters 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 5  INTRACELLULAR FLUID COMPARTMENT 2- The intracellular fluid : fluid in the body are inside the 100 trillion cells and are collectively called the intracellular fluid. Thus, the intracellular fluid constitutes about 40 percent of the total body weight in an “average” person. - About 28 of the 42 liters - The fluid of each cell contains its individual mixture of different constituents. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 6  BODY FLUID COMPARTMENT - The percentage of TBW depends on age, gender, and degree of obesity. - As a person grows older, the percentage of TBW is gradually decreases, this decrease is due in part to the fact that aging is usually associated with an increased percentage of the body weight being fat, which decreases the percentage of water in the body. - In premature and newborn babies, the total body water ranges from 70 to 75 percent of body weight. - Because women normally have a greater percentage of body fat compared with men, their total body water averages about 50 percent of the body weight. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 7  BODY ELECTROLYTES - The electrolytes constitute about 7% of the total body weight. - The distribution of electrolytes in various compartments differs markedly. - In the ICF, the main cations are K+ and Mg2+, and the main anions are PO3 and proteins. - While in the ECF, the predominant cation is Na+ and the principal anions are Cl− and HCO3−. Besides these, a small proportion of non-diffusible proteins, nutrients and metabolites such as glucose and urea are also present in ECF. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 8  FUNCTIONS OF ELECTROLYTES 1. Electrolytes are the main solutes in the body fluids for maintenance of acid–base balance. 2. Electrolytes maintain the proper osmolality and volume of body fluids. 3. The concentration of certain electrolytes determines their specific physiologic functions, e.g. the effect of calcium ions on neuromuscular excitability. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 9  FLUID INTAKE AND OUTPUT ARE BALANCED DURING STEADY-STATE CONDITIONS - The fluid intake is highly variable and must be carefully matched by equal output of water from the body to prevent body fluid volumes from increasing or decreasing. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 10  WATER INPUT Water input Water is added to the body fluids by: 1. Ingestion of water in the form of fluid and as constituent of foodstuffs. The water intake is highly variable, which may range from 0.5 to 2.0 L/day depending upon the social and personal habits and environmental conditions. In general, people living in hot climate drink more water. Ingestion of water is mainly controlled by the thirst center. Increase in the plasma osmolality stimulates thirst center and promotes water ingestion. 2. Endogenous production of water during oxidation of foodstuffs adds about 300 mL of water to the body fluids per day. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 11  WATER OUTPUT Water output A variable amount of water is lost from the body in urine, faeces, sweat and as insensible loss. 1. Insensible loss of water (about which the individual is unaware) occurs by evaporation from the cells of skin and respiratory passages. 2. 2. Water loss in sweat. Water loss by the production of sweat from skin can vary from 100 mL/day in routine at room temperature of 23οC to 1400 mL in hot weather to 5000 mL following prolonged exercise. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 12  WATER OUTPUT 3. Water loss in faeces. Most of the water entering the gastrointestinal tract (GIT) is reabsorbed by the intestine. About 200 mL/day is lost through faeces in a healthy individual. Faecal loss of water is tremendously increased in diarrhoea. -GIT water losses can also occur with vomiting. 4. Water loss in urine. About 1500 mL of water is eliminated from the body in urine. Water losses through kidney are highly variable 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 13  DEHYDRATION DEHYDRATION - Is defined as excessive loss of water from the body. Body requires certain amount of fluid intake daily for normal functions. - Minimum daily requirement of water intake is about 1 L. This varies with the age and activity of the individual. - The most active individuals need 2 to 3 L of water intake daily. - Dehydration occurs when fluid loss is more than what is consumed. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 14  EDEMA EDEMA: EXCESS FLUID IN THE TISSUES Edema refers to the presence of excess fluid in the body tissues. In most instances, edema occurs mainly in the extracellular fluid compartment, but it can involve intracellular. 1-INTRACELLULAR EDEMA Three conditions are especially prone to cause intracellular swelling: (1) hyponatremia. (2) depression of the metabolic systems of the tissues. (3) lack of adequate nutrition to the cells. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 15  EDEMA - When blood flow to a tissue is decreased, the delivery of oxygen and nutrients is reduced. If the blood flow becomes too low to maintain normal tissue metabolism, the cell membrane ionic pumps become depressed. - When the pumps become depressed, sodium ions that normally leak into the interior of the cell can no longer be pumped out of the cells and the excess intracellular sodium ions cause osmosis of water into the cells. - Intracellular edema can also occur in inflamed tissues. - Inflammation usually increases cell membrane permeability, allowing sodium and other ions to diffuse into the interior of the cell, with subsequent osmosis of water into the cells 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 16  EXTRACELLULAR EDEMA 2- EXTRACELLULAR EDEMA Extracellular fluid edema occurs when excess fluid accumulates in the extracellular spaces. There are two general causes of extracellular edema: (1) abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries, example; Acute or chronic kidney failure, Mineralocorticoid excess, Heart failure, and burns. (2) failure of the lymphatics to return fluid from the interstitium back into the blood, often called lymphedema. The most common clinical cause of interstitial fluid accumulation is excessive capillary fluid filtration, example; Cancer, infections (e.g., filaria nematodes), surgery , congenital absence or abnormality of lymphatic vessels. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 17  REFERENCES 1- Guyton and Hall Textbook of Medical Physiology, 13TH edition, 2016. 2- Medical Physiology for Undergraduate Students, Indu Khurana, 2012. 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 18 15/4/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 19