1. Essentials of Clinical Medicine Introduction to physiology

2. Introduction to Physiology
Anatomy – how things are constructed
Physiology – how things work

3. Physiology
The movement of water, ions and molecules throughout the body, and particularly across membranes.
The movement of fluids and gases through the body, usually through tubes
The movement of parts of the body relative to other parts
The movement of the body relative to the surroundings 3

4. Introduction to physiology

6. ICF 28 10 4 Total body water 42 Extra-cellular fluid 14
Plasma and Tran
Interstitia
Cell membrane
ICF
Capillary membrane 28 10 4
Total body water 42

7. Water compartments in health
TBW = 60% BODY WEIGHT = 42 litres
Divided into
ICF – 2/3 [66%] = 28
ECF – 1/3 [33%] = 14
Interstitial = 10
Intravascular/plasma = 3
Transcellular [Cell wall, CSF etc] = 1

8. Introduction to physiology
liquid

9. Does this
matter? Yes!

10. Diffusion

12. Flow of fluids through a tube
Dependent on
Force – pressure difference
Tube – diameter [fourth power] and length
Fluid – viscosity and density
Flow – laminar or turbulent

13. Quiet
Noisy

14. Length Pressure difference Diameter [ 4th power!] Viscosity
Normal in blood vessel

15. Abnormal in blood vessel, usual in respiratory
Length
Pressure difference
Diameter
Density
Abnormal in blood vessel, usual in respiratory

16. Laminar flow is silent - so if you hear a noise [murmur or bruit]
Does this matter? Yes!
Laminar flow is silent - so if you hear a noise [murmur or bruit]
in the cardiovascular system it must mean there is turbulent flow and something is wrong!
E.g. arteries in the neck or kidneys.
In the heart, you will hear the NORMAL heart sounds, which are caused by the valves closing; if you hear any other noise, something is wrong!

17. Does this matter? Yes!
Turbulent flow is noisy and in the respiratory system, flow is usually at least partially turbulent.
So you can normally hear breath sounds.
You can also hear abnormal sounds, such as a wheeze caused by asthma.

18. Atherosclerosis 18

19. Does this matter? Yes!
Atheroma can occur in any artery and is a major cause of death and disability
Brain – stroke
Heart - heart attack
Kidneys – renal failure
Peripheral – lose limb

20. Length
Pressure difference
Diameter [d 4th]
Viscosity

21. Length
Pressure difference
Diameter [d 4th]
Viscosity

22. Equilibrium between plasma and interstitial fluid is established
Governed by ‘Starling forces’
where loss of fluid from the plasma, owing to
hydrostatic pressure
is opposed by reabsorption of fluid into plasma, owing to
colloid osmotic pressure or oncotic pressure
EH Starling

23. Hydrostatic pressure forces fluid out of the plasma across capillary walls
Arteriolar
Venular
Hydrostatic pressure
hydrostatic pressure 35mm Hg
hydrostatic pressure 15mm Hg
filtration of plasma

24. Colloid osmotic pressure 25mm Hg
Impermeance of plasma proteins generates a colloid osmotic pressure
Colloid osmotic pressure draws fluid back into capillaries from interstitial space
Arteriolar
Venular
Colloid osmotic pressure 25mm Hg

25. equilibrium between plasma and interstitial fluid
Filtration pressure = hydrostatic pressure – colloid osmotic pressure
Arteriolar
Venular
hydrostatic pressure 35mm Hg
hydrostatic pressure 15mm Hg
Colloid osmotic pressure 25mm Hg
reabsorption at venular end

26. Does this matter? Yes! Things can go wrong! Fall in plasma protein
Defect in capillary membrane
Rise in venous pressure

27. Does this matter? Yes! Oedema Starvation [low input of nutrients]
Liver failure [not enough made]
Anaphylaxis
Heart failure