Medical physicsDr. Taqey AlMosawey

A bone joint composed from synovial membrane in cased two bone ends and synovial fluids (fig.5) .the surfaces of the joint are articular cartilage . the surface of the cartilage is rough which plays an useful role in joint lubrication by trapping some of the synovial fluid . this fluid squeezed in the joint according to the stress applied on the joint .the amount and the viscosity of synovial fluid change according to the applied stress . when a continues stress applied on the knee joint , synovial fluid in continually squeezed in the joint which cause a swollen in the joint .

Lubriction of bone joints:

i: rheumatoid arthritis which result in over production of synovial fluid in the joint and causes swollen joints and

ii: ostpoarthrosis a disease of the joint it self . threads squeeze synovial fluid from the porosi , of bone low viscosity means good lubrication the coefficient of friction reduced between the bones in the knee by synovial fluid to less than 0.01 where that of steel blade on ice s about 0.03 .

There are two major disease affect the joints which are :-

energy of the body: all activities of the body include energy

changes . the energy converted to work e.g. climbing a hill , lifting a weight ….

The potential energy can be change to a kinetic energy .

At based rest condition ,the energy conserved by the body in nearly follows:

  2770 used by liver and spleen 25% used by skeletal muscle and the heart .

CH5energy , work and power of the body

19% used by brain . 10% used by kidney . 19% digestive system , heat loosen … etc. The body uses food ………….. The food n changed to molecules by the

digestive system to combine with oxygen to produce the energy .

There are continuous changes in the energy of the body when it is doing work or not .

The conservation of energy in the body can be given by the first law of thermodynamics:

ΔU=ΔQ-ΔW…..(1) where ΔU=change in stored energy (-ve or +ve) ΔQ=heat loose or gained ΔW=work done by the body When the change of ΔU,ΔQ and ΔW in a

short interval of time Δt,thus the Rate of change of ΔU,ΔQ and ΔW is given by:

is the mechanical power .

The unit of these are :_ Food energy : kcal or cal Energy: joul/sec or watt or erg Energy (English unit) : foot – pound . Energy change in the body : Food is oxidized by the cells of the body after

the food digested to molecules of glucose the oxidation of one mole .

C6H12O6+6O2→6H20+6CO2+686 kcal This means that: One mole of glucose (180gm) + 6 moles of O2

(192gm) → 6 moles of H2O (108gm) + 6 moles of CO2 (264gm) + 686 kcal of heat .

Note thate one mole of a gas at normal conditions (normal temperature and normal pressure) has a volume of 22.4 liters .

Q1/ calculate the energy released per 1 gm of fuel and 1 lit of O2 used ?

Q2/ calculate the volume in liters of each O2 and CO2 used per/gm of fuel ?

The basal metabolic rate BMR is the lowest rate of energy can consumption needed to perform minimal body function under resting condition when the body

The typical person consumes energy when completely at rest at a rate of about 92 kcal/hr or 107 w which is called 1 met .

BMR is affected by the thyroid activity, it is higher for the persons having over active thyroid .

The chemical activity of the body is increasing or decreasing rapidly with the increase or decrease of the body temperature e.g. increase of body temperature will result in the increase of the chemical activity by 10% , and 2C˚ increase cause increasing of chemical activity by 20% . 3C˚ increase in the temperature causes 30% increase of 30% of the chemical activity . the decrease in the body temperature with result in decreasing the chemical activity of the body in the same rates an above . internal body temperature change in body

C˚ Temperature %

38 10% more

39 20% more

40 30% more

36 10% less

35 20% less

34 30% less

Note that the increase in food more than the consumption of energy will result in increasing of the weight and vice visa . hence to keep your weight steady you have to get food

The conserved energy is converted to external work and life preserving functions. The external work is given by :

ΔW=FΔX …..(3) Where : F= the force moved a distance ΔX and in its direction the power is the rate

of doing work : Where v= velocity =

Work and power of the body :

The external work is done when person is climbing a hill or walking up stairs which is equal weight of the body x vertical distance h I.e. ΔW=mgh…. (5)

Energy of 4.8 to 5 kcal is produced by consuming each liter of O2 .

The efficiency of the body is given by :

The body is consider a good efficient machine its efficiency can be up to about 20% is cycling and heavy exercises ..with external power production of 370w (0.5) and metabolic rate of 1850w

If you are riding a bicycle on level ground with constant speed there is no change in kinetic or potential energy and the power supplied is used to overcome friction and wind resistance long term power is proportional to the maximum rate of O2 consumption in the working muscles for a healthy man this consumption = 50 ml/(kg.min).

Pressure is defined as the force per unit area

For solid the force per unit area = stress the

pressure for liquid column: p=ρgh……..(2) where ρ= density of liquid , g= gravity

acceleration and h= high of liquid .

CH6Pressure

measurement of pressure in the body : part of the body normal pressure (mmHg)

pressure instrument

Blood systole: 100-140 sphygmomanometer

Skull diastole : 60-90 (mercury colomn ) aneroidsealed container with needle or digital.