Body fluid compartments Flashcards
What is the water percentage in baby, male and female?
baby-80%
male-60%
female-50%
What percentage of water is gained from metabolism?
10%
What percentage of water is lost in urine and faeces?
Urine-60%
Faeces- 40%
What are the 4 different sources of water to the body? How much water does each source supply?
- Ingested water (2 liters)
- Liver and pancreatic secretions ( 2 liters)
- salivary gland secretions (1.5 liters)
- Stomach and small intestines secretions (3.5 liters).
What are the 3 different sources of water loss in the body? How much water does each source loose?
Small intestines absorbs ~ 8.5 liters
Colon (400ml)
feces (100 ml)
Where is most of the water in the body located?
Intracellular fluid (40%)= other, plasma, interstitial Extra (20%)
Which ions are high in the extracellular fluid and plasma? Which is the major cation and anion?
In order
Na+ Cation
Cl- Anion
HC0- 3 Anion
Which ions are high in the intracellular fluid?
Which is the major cation and anion?
K+ Cation
PO4 3- Anion
Protein anions (also a little in plasma)
What is the normal plasma osmolality?
What is the normal urine osmolality?
280-300 mOsm/Kg
500and 800 mOsm/Kg (24h urine test)
Randon- 50-1400
What is the effect of hydro-static pressure?
Moves water moves from the blood plasma into the interstitial fluid
What is the effect of osmotic pressure?
Moves water from interstitial fluid into the blood plasma
Which two compartments make up extracellular fluid?
Interstitial fluid
Blood plasma
What does the blood plasma have which may effect osmotic pressure?
plasma proteins (protein ions)
Why does active transport require energy?
Because it is going against the concentration gradient
What is an aquaporine?
Membrane protein water channels
How is water and osmolality of the ECF controlled by the CNS/ brain?
The hypothalamic thirst center involves
Subfornical Organ (SFO)
and
Organum Vasculosum of the lamina terminalis (OVLT)
both have extensive vasculature and lack of a normal blood brain barrier (BBB)
This allows them to link the CNS and peripheral blood flow
What happens when the hypothalamic thirst center is damaged?
Partial or total loss of a desire to drink
What stimulates the sensation of thirst?
increase in plasma osmolality (1-2%)
or decrease in plasma volume (10-15%)
Where is the thirst centre located, what is used to monitor it, and where are impulses relayed to in the brain?
anterior hypothalamus
osmoreceptors
cerebral cortex (conscious)
Describe how information in the blood is relayed to the hypothalamus
Baroreceptors in blood vesseles are innervated by the vagus and glossopharangeal nerve..
Information passes using these nerves to the vasomotor centre in the medulla oblongata
It travels up to the paraventricular and supraoptic nucleus in the hypothalamus.
The osmoreceptros then stimulate the posterior pituitary which when required will stimulate ADH production
What is ADH? Where is it released from, what does its release depend on and what effect does it have?
(hormonal regulation of low plasma level)
Antidiurectic hormone
Posterior pituitary
Released when plasma osmolality increased (sensed by osmoreceptors and hypothalamus)
Released when plasma volume decreases (sensed by baroreceptors in the great veins and right atrium)
It causes the cells of the collecting duct and distal tubules to be more permeable to water. And increases the insertion of aquaporins
What is aldosterone? What releases it? Why is it released? And what effect does it have?
(hormonal regulation of plasma osmolality)
Hormone
Released from Adrenal cortex
when NA+ is low or k+ is high.
It targets Na+/K+ ATPase and epithelial Na+ channel. Causes absorption of Na+
Hormonal regulation of high blood plasma-
What is ANP? What releases it? When is it released? What effect does this have?
Atrial natriuretic peptide
Released from cardiac atria
when blood volume inceases (stretches atria)
brings blood volume back to normal- increased Na+ excretion so increased urination
What is the function of Antidiuretic hormone (ADH) or vasopressin
makes cells of collecting duct & distal tubule permeable to water.
What is the function of Angiotensin II and Aldosterone
promote the urinary reabsorption of Na+ and Cl- (as well as water, by osmosis) when dehrydrated.
What is the function of Atrial natriuretic peptide (ANP)
promote excretion of Na+ and Cl- followed by water excretion to decrease blood volume.
When does dehydration occur and what are its symptoms?
When water intake is not enough to cover water loss over a long period of time so water is lost from the plasma and interstitial fluid.
Symptoms- weight loss, confusion, fever
Which condition can cause excess urine loss/ dehydaration?
Type 1 and Type 2 diabetes
excess sugar increases osmolality and prevents water reabsorbtion
What type of kidney abnormalities can cause dehydration
Under developed kidneys (young)
Declined kidney function (old)
What is water intoxication?
Too much water drunk too fast or complete blockage of urine production. This dilutes the bodies fluids. Na+ in ECF is reduced So osmotic shift of water into cells causing cellular swelling (convulsions, coma,death)
What is the word to describe a low sodium concentration in the blood? Which party drug can cause this?
Hyponatraemia
Ecstasy- drink too much water
What is oedema?
The swelling of the tissues due to accumulation of fluid in the ECF
What are the 4 main causes of oedema? State any associated conditions
- increased capillary hydro-static pressure- so fluid leaves capillaries
(cirrhosis portal hypertension) - loss of plasma proteins (sever malnutrition)
- Obstruction of lymphatic circulation)
- Increased capillary permeability (inflammation)
What is the consequence of lactose malabsorbtion?
Osmotic diarrhea
Which are the major solutes which contribute to osmolality?
Na+, Cl-, Glucose & urea
What are solutes? What are the different classes of solutes? What fits into each category?
Solutes: molecules in solution (eg salts)
• Classification:
– Electrolytes – inorganic salts (ie: Na+, K+, Cl-) , all acids and bases and some proteins
– Non electrolytes – examples include glucose, lipids, creatinine, and urea
Which type of solute has the greatest osmotic power?
Electrolytes
Describe what is osmotic pressure?
the process that controls the movement of solvents (water) across a membrane. Movement will occur when there are differences in osmotic pressure across a membrane.
What are the two definitions of osmotic pressure? Which is most often used?
Osmolarity- solute concentration as the number of osmoles of solute per litre of solution
Osmolality: is the measure of the osmoles (Osm) of solute per kilogram (Kg) of solvent
Osmolality is most often used
Can osmolarity and osmolality be changed? I so by what?
Osmolarity can by pressure or tempertaure
Osmolality can not- per unit mass
What happens to urine when ADH is high and when it is low?
Which medical condition can cause ADH release?
Low ADH levels produce dilute urine and reduced volume of body fluids
• High ADH levels produce concentrated urine
prolonged fever, excessive sweating, vomiting, or diarrhea, severe blood loss
Where is most water reabsorbed? How much is absorbed here?
Proximal tubule
80%
What is the most common cause of portal hypertension?
Cirrhosis
Where will you find barereceptors?
Where will you find osmoreceptors?
Great veins
Right atria
Hypothalamus
