BODY FLUIDS

Fluids.ppt
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Body Fluids
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Fluid compartments

The fluid compartments in healthy, normal men and women differ, because weight for weight the female body contains more fat.

When we consider body fluids, it is essential to distinguish between intracellular (inside cells) and extracellular (outside cells) fluids.
The extracellular fluid in turn comprises both interstitial (between cells) and plasma compartments.
Normally it is the interstitial concentration of substances which concern us.

Ionic Composition

It is important to realise that proteins are large organic anions, that can not, under normal circumstances, leave the cell body, or for that matter the blood vesels..
The intracellular protein ions are responsible, in part, for the distribution of ions across the cell wall.
The crucial concentrations are the interstitial and intracellular concentrations.

Concentration in mM/ L

Plasma
[/color]Na+ 140 - K+ 4 - Ca++ 2 - CL- 100 - Hco3 28 - Protein 16

Interstitial

Na+ 145 - K+ 4 - Ca++ 2 - Cl- 115 - Hco3 30 - Protein 10

Intracellular

Na+ 10 - K+ 160 - Ca++ 10-4 - Cl- 3 - Hco3 10 - Protein 55

Forces acting upon the ions

: Since there are different concentrations of ions on either side of the cell membrane, there are two forces acting

the force of the chemical gradient 1

the force of the electrical gradient 2
If the membrane is only permeable to potassium, the inside of the cell will be negative with respect to the outside. This is the situation which obtains in excitable tissues when the membrane is "at rest".

Transport across membranes

The different concentrations of ions either side of the membrane mean that there are several concentration gradients to consider, and these allow for a number of different transport processes.
The most important pump in the whole system, and one of the greatest users of energy in the body at rest, is the sodium/potassium ATPase, also known as the sodium pump. The sodium gradient set up by this pump provides the chemical energy to allow many substances to enter or leave the cell against their concentration gradient.

Osmotic pressure

Just as ions tend to move across semi-permeable membranes - from areas of high concentration to areas of low concentration
so does water - to dilute stronger solutions
this is osmosis - the pressure which withstands the movement is osmotic pressure

Hydrostatic pressure

If you use a hose pipe, the water pressure at the tap end, is greater than the water pressure at the nozzle.
These are hydrostatic pressures - which "try" to force the water out of the pipe
In a blood vessel, the hydrostatic pressure at the arterial end is usually higher than at the venous end.

Starling's Hypothesis

In a capillary, there are two pressures to consider, the hydrostatic pressure, which is a composite of the force provided by the heart, and the forces due to gravity. Hydrostatic pressure is the force which "tries" to force the fluid out of the capillary.
The plasma proteins can not normally leave the capillary, so they exert an osmotic pressure, which tends to draw fluid into the capillary.
The consequence is that fluid tends to leave the capillary at the arterial end, and be drawn back in at the venous end. Any surplus fluid will either produce oedema, or be taken up by the lymph ducts, and returned to the circulation.
Altering either the hydrostatic or osmotic pressure will disturb the fluid balance across the capillary wall.

Body fluids

Body fluid, bodily fluids, or biofluids are liquids originating from inside the bodies of living people.
They include fluids that are excreted or secreted from the body as well as body water that normally is not.
The dominating content of body fluids is body water.
Approximately 60-65% of body water is contained within the cells (in intracellular fluid) with the other 35-40% of body water contained outside the cells (in extracellular fluid).
This fluid component outside of the cells include the fluid between the cells (interstitial fluid), lymph and blood.
There are approximately 6 to 10 liters of lymph in the body, compared to 3.5 to 5 liters of blood.

List of body fluids
Amniotic fluid
Aqueous humour and vitreous humour
Bile
Blood serum
Breast milk
Cerebrospinal fluid
Cerumen (earwax)
chyle
Endolymph and perilymph
Feces - see diarrhea
Female ejaculate
Gastric acid
Gastric juice
Lymph
Mucus (including nasal drainage and phlegm)
Peritoneal fluid
Pleural fluid
Pus
Saliva
Sebum (skin oil)
Semen
Sweat
Synovial fluid
Tears
Vaginal secretion
Vomit
Urine

Body fluids and health

Body fluid is the term most often used in medical and health contexts. Modern medical, public health, and personal hygiene practices treat body fluids as potentially unclean. This is because they can be vectors for infectious diseases, such as sexually transmitted diseases or blood-borne diseases. Universal precautions and safer sex practices try to avoid exchanges of body fluids. Body fluids can be analysed in medical laboratory in order to find microbes, inflammation, cancers, etc.
[edit]Sampling
Methods of sampling of body fluids include:
Blood sampling for any blood test, in turn including:
Arterial blood sampling, such as radial artery puncture
Venous blood sampling, also called venipuncture
Lumbar puncture to sample cerebrospinal fluid
Thoracocentesis to sample pleural fluid
Amniocentesis to sample amniotic fluid

Body fluids in forensic science
The term body fluid is used in a forensic science context to refer to items of biological evidence. The term is a historical one whose meaning has been expanded due to the discovery of the evidential significance of various biological materials. Body fluid therefore refers to not only to typical body liquids such as blood or semen, but to any item of trace evidence with a biological origin, including hair, bone, teeth, faeces and skin or muscle tissue.

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Body Fluid Analysis
http://labtestsonline.org/understanding/analytes/body-fluid/tab/glance

Fluid balance

Fluid balance is the concept of human homeostasis that the amount of fluid lost from the body is equal to the amount of fluid taken in. Euvolemia is the state of normal body fluid volume. Water is necessary for all life on Earth. Humans can survive for 4–6 weeks without food, but for only a few days without water.
The amount of water varies with the individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity.[1] In the US, the reference daily intake (RDI) for water is 3.7 litres per day (l/day) for human males older than 18, and 2.7 l/day for human females older than 18[2] including water contained in food, beverages, and drinking water. The common misconception that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of water per day is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day. For example, people in hotter climates will require greater water intake than those in cooler climates. An individual's thirst provides a better guide for how much water they require rather than a specific, fixed number. A more flexible guideline is that a normal person should urinate 4 times per day, and the urine should be a light yellow color.
A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, perspiration and urination. Food contributes 0.5 to 1 l/day, and the metabolism of protein, fat, and carbohydrates produces another 0.25 to 0.4 l/day, ] which means that 2 to 3 l/day of water for men and 1 to 2 l/day of water for women should be taken in as fluid, i.e. drunk, in order to meet the Recommended Daily Intake (RDI). In terms of mineral nutrients intake, it is unclear what the drinking water contribution is. However, inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some minerals. Examples include calcium, zinc, manganese, phosphate, fluoride and sodium compounds. Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role (not necessarily major) in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels. Water is essential for the growth and maintenance of our bodies, as it is involved in a number of biological processes.
Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal.
The human kidneys will normally adjust to varying levels of water intake. The kidneys will require time to adjust to the new water intake level. This can cause someone who drinks a lot of water to become dehydrated more easily than someone who routinely drinks less.
[ ]Routes of fluid loss and gain

Fluid can leave the body in many ways. Fluid can enter the body as preformed water, ingested food and drink and to a lesser extent as metabolic water which is produced as a by-product of aerobic respiration (cellular respiration) and dehydration synthesis.
[ Input
A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, sweating and urination. Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake.
In the normal resting state, input of water through ingested fluids is approximately 1200 ml/day, from ingested foods 1000 ml/day and from aerobic respiration 300 ml/day, totaling 2500 ml/day.
[ ]Regulation of input
Main article: Thirst
Input of water is regulated mainly through ingested fluids, which, in turn, depends on thirst. An insufficiency of water results in an increased osmolarity in the extracellular fluid. This is sensed by osmoreceptors in the organum vasculosum of the lamina terminalis, which trigger thirst. Thirst can to some degree be voluntarily resisted, as during fluid restriction.
[ ]Output
The majority of fluid output occurs via the urine, approximately 1500 ml/day (approx 1.59 qt/day) in the normal adult resting state. ]
Some fluid is lost through perspiration (part of the body's temperature control mechanism) and as water vapor in expired air. These are termed "insensible fluid losses" as they cannot be easily measured. Some sources say insensible losses account for 500 to 650 ml/day (0.5 to 0.6 qt.) of water in adults, while other sources put the minimum value at 800 ml (0.8 qt.). In children, one calculation used for insensible fluid loss is 400ml/m2 body surface area.
In addition, an adult loses approximately 100ml/day of fluid through feces. ]
For females, an additional 50 ml/day is lost through vaginal secretions.
These outputs are in balance with the input of ~2500 ml/day. ]
[ ]Regulation of output
The body's homeostatic control mechanisms, which maintain a constant internal environment, ensure that a balance between fluid gain and fluid loss is maintained. The hormones ADH (Anti-diuretic Hormone, also known as vasopressin) and Aldosterone play a major role in this.
If the body is becoming fluid-deficient, there will be an increase in the secretion of these hormones, causing fluid to be retained by the kidneys and urine output to be reduced.
Conversely, if fluid levels are excessive, secretion of these hormones is suppressed, resulting in less retention of fluid by the kidneys and a subsequent increase in the volume of urine produced.
[ ]Antidiuretic hormone
If the body is becoming fluid-deficient, this will be sensed by osmoreceptors in the organum vasculosum of lamina terminalis and subfornical organ. These areas project to the supraoptic nucleus and paraventricular nucleus, which contain neurons that secrete the antidiuretic hormone, vasopressin, from their nerve endings in the posterior pituitary. Thus, there will be an increase in the secretion of antidiuretic hormone, causing fluid to be retained by the kidneys and urine output to be reduced.
[ ]Aldosterone
Main article: Renin-angiotensin system
A fluid-insufficiency causes a decreased perfusion of the juxtaglomerular apparatus in the kidneys. This activates the renin-angiotensin system. Among other actions, it causes renal tubules (i.e. the distal convoluted tubules and the cortical collecting ducts) to reabsorb more sodium and water from the urine. Potassium is secreted into the tubule in exchange for the sodium, which is reabsorbed. The activated renin-angiotensin system stimulates zona glomerulosa of the adrenal cortex which in turn secretes hormone aldosterone. This hormone stimulates the reabsorption of sodium ions from distal tubules and collecting ducts. Water in the tubular lumen follows the sodium reabsorption osmotically.
[ ]Effects of illness

When a person is ill, fluid may also be lost through vomiting, diarrhea, and hemorrhage. An individual is at an increased risk of dehydration in these instances, as the kidneys will find it more difficult to match fluid loss by reducing urine output (the kidneys must produce at least some urine in order to excrete metabolic waste.)
[ ]Fluid balance in an acute hospital setting

In an acute hospital setting, fluid balance is monitored carefully. This provides information on the patient's state of hydration, renal function and cardiovascular function.
If fluid loss is greater than fluid gain (for example if the patient vomits and has diarrhoea), the patient is said to be in negative fluid balance. In this case, fluid is often given intravenously to compensate for the loss.
On the other hand, a positive fluid balance (where fluid gain is greater than fluid loss) might suggest a problem with either the renal or cardiovascular system.
If blood pressure is low (hypotension), the filtration rate in the kidneys will lessen, causing less fluid reabsorption and thus less urine output.
An accurate measure of fluid balance is therefore an important diagnostic tool, and allows for prompt intervention to correct the imbalance.
[ ]Trace elements

There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism; for example sodium, potassium and chloride are common chemicals found in very small amounts in most waters, and these elements play a major role in body metabolism. Water is essential for the growth and maintenance of our bodies, as it is involved in a number of biological processes.

Homeostasis

Introduction

Homeostasis is the maintenance of a stable internal environment that enables the optimal functioning of body cells. Activities at the cellular level are controlled by feedback mechanisms for the maintenance of homeostasis of body temperature, body fluid composition, blood sugar, gas concentrations and blood pressure. In this topic these mechanisms will be explored and you will have the opportunity to plan and conduct a long-term investigation based on one of your own homeostatic mechanisms.

You will learn about
: Homeostasis

the role of the cell membrane structure in active transport and as a receptor
DNA and how it controls the production of cellular materials
components of a stimulus-response feedback model for homeostasis
homeostatic mechanisms that control body temperature, body fluid composition, blood sugar, gas concentrations, blood pressure
physiological and behavioural mechanisms that influence the maintenance of homeostasis in the homeostatic mechanisms mentioned above.

Regulation of body fluids

The body relies upon a constant fluid level to ensure metabolic reactions within cells can proceed. Gases, nutrients, ions, hormones and wastes are carried in body fluids.

Osmotic pressure

Water is continually being lost from the body in a variety of ways, for example through sweat and urine. When water is lost from any of the body fluids, dissolved solutes become more concentrated and water is less concentrated - this creates high osmotic pressure. When water content increases and solutes are less concentrated this creates low osmotic pressure.

Changes in osmotic pressure will stimulate responses in the body to ensure water levels are maintained in optimum amounts.

The following diagram is the feedback model for increased osmotic pressure, for example after exercising.



he stimulus is an increase in osmotic pressure (water concentration in plasma decreases) due to exercising. This is detected by osmoreceptors in the hypothalamus . The modulator, the hypothalamus, sends a message to release ADH from the posterior lobe of the pituitary gland and nerve impulses from the drinking centre. These effectors are the kidney tubules becoming more permeable to water and the stimulation of drinking behaviour. The responses that occur are an increased reabsorption of water into plasma and an increase in water intake causing a decrease in osmotic pressure which reverses the original stimulus.

Homeostasis via feedback systems
A steady internal state makes it possible for our cells to operate at their optimum level. Changes that occur in the external environment affect the internal environment, which is being continually adjusted in response.

A stimulus-response feedback model is a good way of showing how mechanisms are operating in the body in order to maintain homeostasis .

Things to remember about this model:

the loop represents a continuous process so there is no starting or finishing point
the response alters the original stimulus.
The following diagram reveals a stimulus-response feedback model. Use this diagram to answer the questions below



A negative feedback model can be represented with five boxes, all linked in a circular arrangement with arrows. The box at the top of the page represents the starting point of the feedback loop. It contains the stimulus or change in the environment. The second box which is linked by an arrow contains the receptor or the cells that detect the change. The third box is contains the modulator which is where the change is processed and information relayed on. The fourth box contains the effector which is organs, glands or tissues that are instructed to adjust output or secretions to cause an effect. This is linked by an arrow to the response in the last box. This is the change or outcome of the adjustments. The arrow that links the response box back to the stimulus box is a "dashed" or "broken line" arrow representing negative feedback that is where the response removes the initial stimulus.

Acid Base Balance
This animated tutorial describes the basic physiology of acid base balance.
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