L.8 - continuity principle Flashcards
What does blood consist of?
- plasma and different types of blood cells
Describe plasma and what it contains. How much of the blood bilge does it make up?
- almost clear liquid which makes up approx. 55% of the blood volume.
- It contains many dissolved materials such as proteins, carbs, lipids, ions (electrolytes), etc.
What are the 3 types of blood cells?
- erythrocytes (main cellular component of blood)
- leukocytes
- platelets (thrombocytes)
For erythrocytes - What is the function, diameter, lifetime, and how much of the blood does it make up?
- function: transport of O2 and CO2
- diameter: ~7 um
- lifetime: ~120 days
- volume of erythrocytes in blood:
5 x 10^6 cells/mm^3 of blood
For leukocytes - what is the diameter, volume of it in blood, function, and lifetime?
Diameter: ~9-15 um
Volume in blood: 8000 cells per mm^3
Function: to protect against infection.
Lifetime: 20 day cycle
For platelets (thrombocytes) - what is the diameter, volume of it in blood, function, and lifespan?
Diameter: ~3 um
Volume of it in blood: ~200,009 per mm^3 of blood
Function: to allow clotting
Lifespan: 7-10 day lifespan
How can blood components be separated?
- by centrifugation
Define haematocrit ratio.
- the ratio of RBC volume to the total blood volume (ie- %RBC volume)
What does haematocrit determine?
- the effective viscosity of the blood
haematocrit varies from what?
- from tissue to tissue and also with body condition
In %, how much does blood represent in the total body mass? Give example.
- 7%
Example - how much litres of blood is in a 70 kg male?
0.07 x 70 = 4.9
Approx. 5 litres of blood
How much blood does the heart pump per contraction & how long does it take for an average blood cell to make one full cycle of the body?
- 1 minute since the heart pumps about 80 ml of blood per contraction
Closed pumping system consists of 2 synchronous force pumps which are…?
- left ventricle (veins) and right ventricle (artery)
What does the muscles around the heart walls do?
- contracts and relaxes to form the pumping action (boyle’s law)
- heart contracts in systolic phase
- heart relaxes in diastolic phase
What is the contraction of both atria (atrial systole) is followed by…?
- by a contraction of ventricles (ventricular systole)
- which is then followed by a relaxation phase (diastole)
What stimulates the mechanical contractions of the heart?
- stimulated by electrical pulses (action potentials) generated in the sinoatrial node
What does left ventricle and right ventricle supply respectively?
L.V - provides systemic blood
R.V - supplies the lung
The 2 synchronous pumps work on the basis of what law?
- boyle’s law which states that for a gas at constant temperature, pressure x volume = constant
PV= constant
What is boyle’s law?
P•V = constant
What happens to the volume and pressure in the heart when the heart chambers relax and expand?
- volume increases
- pressure inside the chambers decreases (drawing blood into the chamber)
What happens to the volume and pressure in the heart when the heart chambers contracts?
- volume decreases
- pressure increases (forces blood out of chamber)
What happens as the blood circulates through the systemic system?
- pressure is lost
- pressure drops from 120 mmHg in the aorta to ~4-5 mmHg when entering the right atria.
What happens to the pressure when the right atria and ventricle contracts?
- pressure is increased to around 25-40 mmHg before entering the lungs where it decreases again to around 7-8 mmHg
What is the continuity principle (aka equation of continuity EOC state)?
- consider a channel through which a fluid can flow (e.g. artery)
- the EOC states that for an incompressible fluid, the rate of flow of fluid into one end of the channel must be equal to the rate of flow of fluid leaving the other end.