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Urinary Sytem > Body Fluid Compartments > Flashcards

Body Fluid Compartments Flashcards

1
Q

Total fluid compartments

A

Total Body: 42L: ICF: 28L

ECF: 14L

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2
Q

The various fluid quantities in the ECF

A

Plasma(IVF): 3L
Tissue fluid( ISF): 11L
Transcellular fluid: 1-2L

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3
Q

What is meant by the term Steady State

A

The body fluid constancy, in terms of composition and volume, is maintained by way of a dynamic equilibrium
or so-called “steady state”, which implies a continuous turnover (exchange) of solutes and fluid. This is the
opposite of a static equilibrium where there is no turnover once equilibrium has been reached.

Fluid intake(high variable) and output are balanced

Ensures homeostasis by preventing Increase/Decrease body fluid volumes

Kidney plays an important role.

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4
Q

Discuss Fluid Intake

A

By:

  1. Ingestion of liquids or water in food (2100 ml/day)
  2. Synthesized by oxidation of carbohydrates (200 ml/day)

Total water intake = 2300 ml/day

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5
Q

Fluid Output/Loss

A

Insensible (consciously unaware) Water Loss:

• Evaporation from the respiratory tract and diffusion through the skin (700 ml/day)

Fluid Loss in Sweat

  • Varies - dependent on climate and physical activity
  • Normal conditions (100 ml/day)
  • Hot weather/heavy exercise (increases to 1 to 2 L/hour)

Water Loss in Feces
• Small amount of water lost in feces (100 ml/day) normally
• Severe diarrhea – Life-threatening if not corrected (Several L lost)

Water Loss by the Kidneys
▪ Urine excreted by the kidneys

The most important means by which the body maintains a balance between water and
electrolyte intake and output, is by controlling the rates at which the kidneys excrete
these substances

Urine volume can be as low as 0.5 L/day in a dehydrated person or as high as 20 L/day
in a person who has been drinking lots of water

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6
Q

Obligatory Urine Volume

A

Minimal volume of urine that must be excreted by the kidneys

A normal 70 kg human must excrete about 600 milliOsmoles of solute each day.
If maximal urine concentrating ability is 1200 mOsm/L, the minimal volume of urine that must be excreted

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7
Q

Obligatory Urine Volume Calculation

A

600 mOsmol/day / 1200 mOsmol/L

= 0.5 L/day

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8
Q

Human Waste Products a day

A

600 mOsmol/day

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9
Q

Clinical abnormalities of fluid volume regulation

A

HYPONATREMIA:

-Excess water in the ECF or loss of sodium from the
ECF

HYPERNATREMIA (↑plasma sodium concentration):

-Loss of water from the ECF (concentrates sodium ions) orexcess sodium in the ECF

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10
Q

Hyponatremia

A

Excess water in the ECF or loss of sodium from the
ECF
➢ The loss of sodium results in hyponatremia dehydrationassociated with decreased ECF volume:

▪ Overuse of diuretics - inhibits the ability of the kidneys
to conserve sodium
▪ Addison’s disease - ↓ secretion of aldosterone, impairs the ability of the kidneys to reabsorb sodium

➢ Excess water retention results in hyponatremia
overhydration:

▪ Excessive secretion of ADH, causes the kidney tubules to reabsorb more water
▪ Brain swelling (skull is rigid – herniation)

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11
Q

Hypernatremia

A

(↑plasma sodium concentration)

Loss of water from the ECF (concentrates sodium ions) or excess sodium in the ECF

➢Loss of water from the ECF:

▪ Occurs from an inability to secrete ADH - large amounts of dilute urine excreted (“central” diabetes insipidus)

▪ More common cause is simple dehydration, promotes intense thirst and stimulates secretion of ADH
➢Excess sodium in the ECF:

▪ Hypernatremia—overhydration – associated with extra water retention by the kidneys

Rapid fluid replacement could lead to cerebral edema (ICF and ECF loads increase causing increased pressure within the brain space)

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12
Q

What is the Gibbs-Donnan Effect phenomenon

A 
The phenomenon of predictable and
unequal distribution of permeant
charged ions on either side of a
semipermeable membrane, in the
presence of impermeant charged
ions
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13
Q

Osmotic pressure

A

π(pi)
π = MRT

M is the molar concentration of dissolved
species (units of mol/L).

R is the ideal gas constant (0.08206 L atm
mol-1 K-1)

T is the temperature on the Kelvin scale.

Osmotic pressure caused by proteins are critical for keeping fluid inside capillaries

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14
Q

Transcapillary Fluid Movement

A

Arterial blood pressure (ABP) exerts an outward
hydrostatic force on the fluid inside blood vessels, while the plasma proteins are responsible for an inward osmotic force (COP).

The two forces, causing filtration and reabsorption, balance each other almost exactly, except that the outward force is a bit larger than the inward force.

Thus slightly more fluid moves out of the
capillaries than comes back.

This small volume of fluid is returned to the blood by the lymphatic system.

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15
Q

Lymphatic Capillaries

A

1/10 of the fluid that leaks out is transported by the
lymphatic system back into the blood

Total estimated lymph flow of about 120 ml/hr or 2-
3L/day

Crucial for transport of proteins

Allows for passage of large molecule (proteins)

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16
Q

Edema

A

Accumulation of excess fluid in the interstitial spaces

Develops as a result of tissue losing its negative
pressure

It is an abnormal and a harmful condition

Disruption of one of the four Starling Forces

17
Q

What is Edema

A

Refers to excess fluid in the interstitial spaces. It is an
abnormal, harmful condition that, inter alia, is unfavourable to exchange between the intravascular andintracellular compartments.

18
Q

Causes of Intracellular Edema

A
  1. Hyponatremia
  2. Depression of the metabolic systems of the tissues; and
  3. Lack of adequate nutrition to the cells
  4. Inflamed tissues - Inflammation increases cell membrane permeability, allowing sodium and other ions to diffuse into the interior of the cell resulting in osmosis of water into the cells
19
Q

Causes of Extracellular Edema

A
  1. Lymphedema - failure of the lymphatics to return fluid from the interstitium back into the blood
  2. Excessive capillary fluid filtration
  3. Increased capillary pressure
  4. Decreased plasma proteins
  5. Increassed capillary permeability
  6. Blockage of lymph return
20
Q

Four major factors that cause increased capillary filtration of fluid and protein into the interstitium

A
  1. Increased capillary hydrostatic pressure
  2. Decreased plasma colloid osmotic pressure
  3. Increased capillary permeability
  4. Increased interstitial fluid colloid osmotic pressure
21
Q

What is Lymphedema

A
  1. FAILURE OF THE LYMPH VESSELS TO RETURN FLUID AND
    PROTEIN TO THE BLOOD

Plasma proteins that accumulate in the interstitium have no other way to be removed

↑ Colloid osmotic pressure of the interstitial fluid, which removes more fluid out of the capillaries

• Caused by infection, cancer or after surgery in which lymph vessels are removed or obstructed

22
Q

Edema caused by Heart Failure

A

Systemic/Peripheral Edema:

• Heart is too weak to pump blood around the body
effectively

• Raises venous pressure and capillary pressure,
causing increased capillary filtration

Pulmonary Edema:

• Left-sided heart failure but without significant failure
of the right side of the heart

• Blood is pumped into the lungs normally by the right
side of the heart but cannot enter from the pulmonary
veins to the left side of the heart
• Pulmonary vascular and capillary pressures ↑

23
Q

Kidney Disease

A

Decreased urinary excretion of salt and water

• Large amounts of sodium chloride and water are added to the ECF

• Most of the salt and water leaks from the blood into the interstitial
spaces

The main effects of this are:
1. Widespread increases in interstitial fluid volume (extracellular edema) and

  1. Hypertension due to the increase in blood volume
24
Q

Safety factors that prevent Edema

A

Low tissue compliance in the negative pressure
range (- 3 mm Hg):

▪ The interstitial fluid hydrostatic pressure is in the
negative pressure range, small increases in
interstitial fluid volume cause relatively large
increases in interstitial fluid hydrostatic pressure,
opposing further filtration of fluid into the tissues

Increased lymph flow (7 mm Hg):

▪ Lymph flow can increase 10- to 50-fold when
fluid begins to accumulate in the tissues

Wash-down of proteins (7 mm Hg):

▪ Proteins are removed by lymph flow, decreasing
the interstitial fluid proteins, lowers the net
filtration force across the capillaries and prevents
further accumulation of fluid

25
Q

Potential spaces and effusions

A

▪Potential spaces: Pleural cavity, pericardial cavity, peritoneal
cavity, and synovial cavities

▪Fluid in the capillaries adjacent to the potential space diffuses
not only into the interstitial fluid but also into the potential
space

▪Proteins collect in the potential spaces because of leakage

▪Effusion: Edema fluid in potential spaces

▪Ascites: collection of effusion fluid in the abdominal cavity

Urinary Sytem (12 decks)

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