Body Fluid, Flow and Pressure Flashcards
What are the 3 main fluid compartments in the body?
Intracellular
Plasma
Interstitial space (Extracellular)
What % of the body is water?
60%
Of the body’s 60% what proportions are intracellular, interstial and plasma?
40% Intracellular
15% Interstitial
5% Plasma
How can we measure fluid compartments?
V=S/C
V= unknown volume
S= known amount of substance
C= concentration
What substance is used to measure the plasma volume?
Evan’s blue, inulin, albumin
- A substance that does not cross capillaries
What substance is used to measure extracellular space?
24Na or sucrose
- A substance that doesn’t enter cells easily.
What substance is used to measure the total body water?
3H2O
Something that distributes in all of the body’s water.
What are the 3 major ions in body fluids?
Na+, K+ and Cl-
Define osmolarity.
Concentration of a solution expressed as total no. solute particles per litre.
What is the osmolarity of blood plasma?
290 mosmol/litre
What is crystalloid oncotic pressure?
Due to ions Na+, K+, Cl-
Cell membranes are mainly impermeable to ions.
Capillary walls are permeable so theres no crystalloid oncotic pressure difference.
What is oncotic osmotic pressure?
Form of osmotic pressure induced by proteins in blood plasma.
What is the oncotic pressure exerted in capillaries?
25mmHg
What direction does water move in terms of osmotic pressure?
Water will move from low osmotic pressure to high osmotic pressure.
What is the plasma concentration of Na+?
140mmol/litre
What is the plasma concentration of K+?
4mmol/litre
What is the plasma concentration of Ca2+?
2mmol/litre
What is the intracellular concentration of K+?
120mmol/litre
What is the intracellular concentration of Na+?
10mmol/litre
What is the intracellular concentration of Ca2+?
100nmol/litre
What is the major ion controlling blood volume?
Na+
What is the major ion controlling cell volume?
K+
What is the average life span of a red blood cell?
120 days
What is the red blood cell count in an average human?
Males = 5.5x10^12/litre Females = 4.8x10^12/litre
What are the 3 main types of leucocyte (white blood cell)?
- Lymphocytes (20-40%)
- Monocytes (2-8%)
- Granulocytes
What is the total number of platelets in blood?
1.5-4x10^11/litre
What is pulmonary circulation and give two features of it.
Circulation from the heart to the lungs.
Low resistance
Low pressure
What is systemic circulation and give three features of it.
Circulation from heart around the body.
High resistance
High pressure
In parallel with each other
Define cardiac output
CO = SV x heart rate
CO is volume per minute ~5L/min
SV = stroke volume (volume per beat) ~70mls
What is the link between venous return and cardiac output?
They must be the same.
What is ‘Total peripheral resistance’?
The force required to maintain blood flow from the root of the aorta to venous end.
Pressure load on the left heart.
Also called AFTERLOAD.
What is ‘central venous pressure’?
Filling pressure of the heart.
Also called PRELOAD.
Define Fick’s Law.
Rate of diffusion is dependent on area, concentration difference and distance it has to travel.
Define the Law of Flow (Darcy’s Law)
Flow is proportional to pressure difference and inversely proportional to the resistance to flow.
What is the equation of Darcy’s Law?
Flow = (P1-P2)/R
Where:
R=resistance to flow (independent variable)
Describe Pousseuilles Law.
A small change in diameter causes a large change in resistance and flow.
R= 8VL/πr^4
L=length of tube
r=radius of tube
V=viscosity of fluid
Flow is proportional to r^4
What is the influence of viscosity of a liquid on flow?
Laminar flow - viscous drag at the sides of the tube slows flow at the sides. Faster movement in the centre of the tube - AXIAL streaming.
What is the effect of turbulence on flow?
Increases resistance and causes vibrations.
Can cause damage to the vessel wall or cause clotting.
What is the effect of tubes in series on the total resistance?
Total resistance = R1 + R2 + R3…
What is the effect of tubes in parallel on the total resistance?
1/Total resistance = 1/R1 + 1/R2 + 1/R3…
Hence lower cumulative restance than in series.
How is flow controlled independently in tissues?
By constriction or dilation of its blood vessels.