To what extend human body is similar to a machine ? Human body must have an energy source in both phases, electrical and mechanical Human body consists of billions of engines (Cells) Cardiovascular system acts as a transport ways between these engines to supply them with fuel and exclude wastes Fuel cycle within the machine : 1- Food is digested in the digestive system 2 - Digested food is combined with oxygen (O 2 ) 3- Oxygenated digested food is immersed to the cells and combustion takes place to produce fuel Why 80 % of air is nitrogen not oxygen ?

Air is inhaled through the nose or mouth and then through the pharynx, larynx, and the trachea. The trachea divides into the right and left bronchus, each of which continues to bifurcate into smaller and smaller bronchi and terminal bronchioles until they form alveoli Alveoli are the actual operating units of the lungs

Atmosphere Air Human Body Blood Ventilation Perfusion

Gas transfer velocity α

Alveoli are lined with a liquid called surfactant, therefore they have tendency to get smaller due to surface tension of the surfactant. Surfactant is a unique liquid because it is unlike all liquids, it has not a constant surface tension. Surface tension of the surfactant is mainly depends on the alveoli surface area. Bubbles from liquids of low surface tension last longer than those of higher surface tension, Why ? Because liquids with higher surface tension form bubbles with high pressure inside so rupture of these bubbles are easier. Bubbles from liquids of low surface tension last longer than those of higher surface tension, Why ? Because liquids with higher surface tension form bubbles with high pressure inside so rupture of these bubbles are easier.

Receiving various signals from the nervous system, the diaphragmatic muscles contract and the diaphragm moves downward. As the diaphragm depresses, it creates vacuum in the lungs and air rushes into the lungs to fill it. As the diaphragm relaxes, it pushes the molecules closer together, increasing the internal pressure in the lungs. The air flows from the lungs into the lower pressure outside the body.nervous systemdiaphragmlungs

Exercising Resting Time Oxygen Partial Pressure (PO 2 ) mmHg

The volume of the lungs during different stages of normal and deep breathing is a good diagnostic of lung functionality. A relatively simple instrument, called the spirometer is used to measure airflow into and out of the lungs and record it on a graph of lung volume (L) versus time (sec). During normal breathing at rest, this is referred to as the tidal volume (TV) at rest. In other words TV is “The amount of gas inspired or expired with each breath”. During heavy exercise, the tidal volume (TV) is considerably larger. At the end of a normal inspiration it is possible with some effort to further fill the lungs with air. The maximum amount of additional air taken in is called inspiratory reserve volume (IRV). Similarly, at the end of a normal expiration we can force more air out of the lungs and the maximum volume of additional expired air is called expiratory reserve volume (ERV).

A traditional and modern spirometer used to measure a lot of parameters which deal with the lungs performance. The airflow in and out of the lungs is recorded on a rotating chart. Water is used as an air-tight seal to keep air within the counterbalance drum. Note: The information collected by the spirometer printed out on a chart called a spirog ram. A modern spirometer An incentive spirometer

Tidal VolumeTV Volume of air inspired and then expired during breathing in rest Inspiratory Reserve VolumeIRV Volume of air a person can inspire above tidal volume Expiratory Reserve VolumeERV Volume of air a person can exhale below resting expiratory volume Inspiratory CapacityIC Volume of a person can inspire above the resting expiratory volume Residual VolumeRV Volume of air left in lung after maximum expiratory effort Functional Residual CapacityFRC Air remains in lung after normal expiration Vital CapacityVC Maximum volume of air that can be inspired and then expired Forced Vital CapacityFVC The same VC but under maximum expiratory force Respiratory Volumes - Tidal Volume(TV) - Inspiratory Reserve Volume (IRV) - Expiratory Reserve Volume (ERV) - Residual Volume (RV) Respiratory Capacities - Vital Capacity (VC) - Inspiratory Capacity(IC) - Functional Residual Capacity (FRC) - Total Lung Capacity (TLC)

Anatomical dead space can be measured using the Bohr equation. It is more commonly used to calculate the latter.Bohr equation Bohr equation states that the dead space (V d ) is calculated as follows : V d /V t = P a CO 2 – P e CO 2 P a CO 2 Where, V d is dead space volume, V t is tidal volume, P a CO 2 is the partial pressure of carbon dioxide in the arterial blood, and P e CO 2 is the partial pressure of carbon dioxide in the expired air.

Is a measure of the tendency of a hollow organ to resist recoil toward its original dimension upon removal of a distending or compressing force. It is a very important physical characteristic of the lungs Compliance Compliance= In adults compliance= liter/cm Fibrosis in lung results in Stiff lungssmall volume change in large pressure Change Flabby lunglarge volume change in small pressure Change Liter/cm Why infants with respiratory distress syndrome (RDS) have lungs with low compliance ? RDS is a respiratory disorder that affects premature infants born about 6 weeks or more before their due dates. In this situation, infant’s lungs cannot produce sufficient surfactant which the liquid coats the inside of lung to keep lungs open to breathe air once they are born. Oxygen insufficiency may be results in some physiological organs damage. Why infants with respiratory distress syndrome (RDS) have lungs with low compliance ? RDS is a respiratory disorder that affects premature infants born about 6 weeks or more before their due dates. In this situation, infant’s lungs cannot produce sufficient surfactant which the liquid coats the inside of lung to keep lungs open to breathe air once they are born. Oxygen insufficiency may be results in some physiological organs damage.