Body Fluids Lecture 1 Flashcards
What is homeostasis?
relative stability of the “milieu intérieur”
What is the milieu interieur?
Internal environment that surrounds the tissues and cells
External Environment
Environment ouside of the organism. It is the physical, chemical, social conditions that surround an organism
Internal environment
The environment that surrounds cells and tissues (relatively constant under conditions of health) also called the “millieu interior”
What is homeostasis in regards to the internal and external environments?
Human body regulates it’s internal environment in response to the external environment (ex. when temp or blood pressure increase internal environment will adjust)
What is the point of all functional activities in the body?
To maintain homeostasis
Is the internal environments different from the external enviornment?
Yes, it is vastly different
What is the most abundant body fluid?
Water
What occurs in body water?
- Solutes are dissolved
- Metabolic reactions take place
Why do metabolic reactions take place in water?
Lots of metabolic reactions produce heat, since water has a high specific heat capacity(requires a lot of energy to increase it by one degree) it acts as a good temperature buffer
Give four other roles of water in the body?
- Regulates body temp.
- Moistens tissues such as those in mouth, eyes and nose
- Protects body organs and tissues
- Lubricates joints
- Helps prevent constipation
- Lessens the burden on the lidneys and liver by flushing out waste products
- Helps dissolve minerals and other nutrients to make them accesible to the body
- Carries oxygen and nutrients to cells
Percent of water in skin
70%
Percent of water in muscle
75%
Percent of water in Heart, Liver, Brain and Kidney
70-80%
Percent of water in bone
25%
Percent of water in Fat (adipose tissue)
10%
What is the dryest type of tissue?
Fat
What happens if someone has a lot of adipose tissue?
They will have a lower total water content
What happens if someone has very little fat(adipose tissue)?
They will have a higher total water content
What is lean body mass?
Overall weight of a person minus the weight from their body fat
When comparing water to lean body mass what is the difference between a fat and skinny person?
The difference between a skinny and fat person becomes insignificant when comparing total body water as a proportion to lean body mass
What is the physiological reference individual?
21-year-old, white male, 70-kg
Why are all standards made for a 21 year old white male?
Standard reference values were computed in the 1920s by medical students who fit this criteria
Newborns body water content
Have 75% water, as adipose tissue is added babies water content decreases
How does puberty affect body water content between males and females?
Females - At puberty female sex hormone estrogen leads to subcutaneous fat in the breast/buttocks. This results in females being drier than males
Do males/females have the same water content prior to puberty?
Yes
How does aging affect water content?
Both sexes become drier as they age due to more adipose tissue and loss of muscle mass (muscles are replaced with connective tissue which is significantly drier)
How to calculate the absolute amount of water?
(Weight of person times % of water) divided by 100 equals absolute amount of water
Why is knowing body water necessary?
Need to know it in order to administer water-soluble medication
Is body water a Dynamic Steady state?
Yes
What is a dynamic steady state?
Water is constantly flowing in(drinking water)/out(peeing) there will always be a constant amount of water but it won’t be the same water
What is water balance?
When intake of water is equal to output
How do we intake water?
-Orally through fluid
-Orally through solids(food)
- Oxidative water from metabolism
What is an insensible output?
Losses that we cannot feel
Examples of insensible output?
- Lungs
-Skin (passive evaporation (entire body surface loses water))
What are sensible outputs?
Losses that we can feel
Examples of sensible output?
-Kidneys(urine)
-Stool (feces)
Obligatory losses vs Facultative
Obligatory: We lose this water no matter what
Facultative: Losses that are necessary to maintain water balance
Example of facultative loss?
- Kidney (urine)
What participates in both facultative and obligatory loss?
The kidney
Key homeostatic organ for water balance?
Kidney
What kind of loss is sweat ?
-Not obligatory
- Sensible
-Facultative loss
What is insensible perspiration?
-Loss of pure water
-Passive evaporation (affected by humidity and ambient temperature)
-Obligatory loss
-Occurs over the entire skin surface
How is sweating different that insensible perspiration?
-Loss of electrolytes
-Active evaporation (require energy)
-Occurs only at sweat glands
-Activated by heavy work/temperature
If someone doesnt have sweat glands will they still have insensible perspiration?
Yes
What is the water turnover in adults?
Over 24 hours 3-4% of the body weight is turned over
What is turnover rate in babies?
Over 24 hours 10% of total body weight it turned over
Why are babies more susceptible to over heating and dehydration?
Because there water turnover rate is very fast and because there surface to volume ration (water does not need to travel far to be passively evaporated from the surface)
Why can’t babies have water?
They are more likely to excrete ions that should not be from their less developed kidneys
What is a negative water balance?
When water loss is greater than water intake
Causes of negative water balance?
- Reduced intake
- Excessive loss from gut (diarrhea, vomiting)
- Excessive sweating
- Excessive loss in expired air (higher altitude causes you to breathe faster and is drier air causing for loss of water)
- Excessive loss in urine (diabetes)
What is water intoxication?
When water intake is grater than water loss
What intoxication causes?
- Excessive intake over a short amount of time
- Marathon
-Hyponatremia (if water is more dilute than cells, it will flow into cells causing them to burst) - Renal system failure (kidneys do not function properly)
What are the two major body water compartments?
- Intracellular fluid(ICF)
- Ectracellular fluid (ECF)
What is total body water percentage and how is it split between the ECF and ICF?
Total body water - 60%
ECF - 20%
ICF - 40%
What is the intracellular fluid and what ions are found in it?
-Fluid found inside all of the cells of the body
-2/3 of all body water
-High in potassium and Mg but low in Na+ and Cl-
What is the extracellular fluid and what ions are in it?
The ECF is made up of two major compartments : the plasma and the ISF and two minor compartments : lymph and transcellular fluid
-It is high in Na+ and Cl- but low is K+
What is the distribution of fluid between the ISF and plasma?
ISF: 15%
Plasma: 5%
What is the plasma?
-It is the fluid medium in which blood is suspended
-Surround all the blood cells
What is another name for hematocrit?
Packed Cell Volume (PCV)
What is the ISF?
-The true “milieu intérieur”
- The fluid that is bathing all the cells of the body
-Found outside the capillaries
What are capillaries and what do they do?
- Oxygenated blood and nutrient rich blood is transported through the capillaries to all cells of the body to provide them with the raw material they need
-Once the cell get what it needs the blood reneters the capillaries and is borught to the heart for reoxygenation
What are lymphatic vessels?
-Finger-like projections that can reach out into all the spaces of the body
-Blind ended tubules: only one end of the vessels are open
What is the lymphatic system?
-A network of blind ended tubules come together to form lymphatic vessels which converge to for lymphatic ducts that drain into the large veins of the chest
What is lymph and homw much of the ECF does it make up?
-colourless watery fluid flowing through the lymphatic system
-Only makes up 1-2% of the total ECF
What is transcellular fluid?
-Fluid produced by epithelial cells that line a certain cavity of your body
-What the fluid is made up of and its function depends on where you are in the body and what the epitheleal cells are secreting
What are 3 examples of transcellular fluid?
Eye:
-Epithelial cells produce ocular fluid
Spine:
- Cerebrospinal fluid
Joints:
- Sinovial fluid
True or false: The distribution of fluid between compartments remains constant?
True
Name all of the percentages of water in each compartment?
Total H20: 60%
ECF: 20%
ICF:40%
ISF: 15%
Plasma: 5%
How to determine compartment volumes directly?
Weigh the organism, desicate the organism(dehydrate it) then weigh the organism again
- The difference tells us how much water was in the organism
How to determine compartment volumes indirectly?
Indicator Dilution Method
1. Add a known quantity of substance to a container with the indicator
2. The colour of the substance will change as the substance and indicator mix
3. Take out a known quantity of the substance and calculate the concentration of the substance with the indicator (V= Q/c)
What must be known for indicator dilution method?
- Total quantity of test substance introduced
- The concentration of the substance/unit volume of fluid after the mixing
How is the indicator dilution method done to a human?
- Known quantity of indicator into vein (Q)
- Allow time to equilibrate
- Remove a known volume of blood and centrifuge it to obtain plasma
- Measure concentration (c) in unit volume of plasma
- Calculate volume of compartment (V- Q/c)
Why shouldn’t the indicator be given orally?
Some will be lost via urine which will mess up the ending concentration
Properties of a good indicator
- Non-toxic
- Diffuses readily
Induced no change in the distribution of water between compartments - Easy to measure concentration once dispersed
Properties of general indicators
- Radioactively labeled
- Coloured
What kind of indicator must be used to measure total body water volume?
An indicator that must be able to cross both the capillary wall and the cell membrane. can move freely through all compartments
What separates the ECF from the ICF?
Cell membrane
What separates the ISF from the plasma?
Capillary membrane
Indicatores from total body volume?
D2O, T2O, antipyrine
What kind of indicator would we use to measure the extracellular fluid?
An indicator that crosses the capillary wall but not the cell membrane
Examples of indicators the can’t cross the cell membrane but can cross the capillary wall
- Radioactively labeled sugars: inulin , sucrose
What kind of indicator must be used to measure plasma volume and give examples?
An indicator that can’t cross the capillary wall
Ex. Evan’s blue, Radioactive albumin
How can we measure the ISF volume?
-Use an indicator that can’t cross the capillary wall to measure the volum of the plasma first
-Use an indicator that can cross the capillary wall to measure the entire ECF
Then use the equation ISF = ECF - Plasma
Equation to measure ICF?
Total body water - ECF = ICF
How can indicator be lost in the body?
- By metabolism
- By excretion
What is 0.9% NaCl?
Can account for/replace the ECF in an individual
