►It is about 16 cycles per

minute.

►It is composed of:

a)Inspiration.

b) Expiration.

c) Expiratory pause.

►It is about 16 cycles per

minute.

►It is composed of:

a)Inspiration.

b) Expiration.

c) Expiratory pause.

1)Supply of O2 to tissues and

removal of CO2 from them.

2)Regulation of PH of the blood.

3)Excretion of water vapour.

4)Regulation of body

temperature.

5)Help voice production.

1)Supply of O2 to tissues and

removal of CO2 from them.

2)Regulation of PH of the blood.

3)Excretion of water vapour.

4)Regulation of body

temperature.

5)Help voice production.

I)Peripheral

mechanism.

II)Central mechanism.

I)Peripheral

mechanism.

II)Central mechanism.

A) Mechanics of inspiration:

1. The thoracic cavity increases in all

directions:

a) Vertically: by contraction of the

diaphragm and its descent 1.5 cm.

b) Transversely: by elevation of the ribs by

contraction of external intercostal musclesc) Antero-posteriorly: by elevation of the ribs, movement of the sternum.

•

A) Mechanics of inspiration:

1. The thoracic cavity increases in all

directions:

a) Vertically: by contraction of the

diaphragm and its descent 1.5 cm.

b) Transversely: by elevation of the ribs by

contraction of external intercostal musclesc) Antero-posteriorly: by elevation of the ribs, movement of the sternum.

•

2. Expansion of the thoracic cavity

leads to increases the negativity

of the intrapleural pressure

leading to distension of the lungs

cause rush of 500 c.c. of

atmospheric air into the lungs.

2. Expansion of the thoracic cavity

leads to increases the negativity

of the intrapleural pressure

leading to distension of the lungs

cause rush of 500 c.c. of

atmospheric air into the lungs.

B) Mechanics of expiration:

Quiet expiration is a passive process, it is done by:

1) Relaxation of inspiratory muscles (diaphragm and external intercostal muscles).

2) Drop of the thoracic cage by its weight.

3) Elastic recoil of the lung.

This pushes 500 c.c. of air out of the lung.

B) Mechanics of expiration:

Quiet expiration is a passive process, it is done by:

1) Relaxation of inspiratory muscles (diaphragm and external intercostal muscles).

2) Drop of the thoracic cage by its weight.

3) Elastic recoil of the lung.

This pushes 500 c.c. of air out of the lung.

Definition:

It is the pressure inside the

pleural sac.

►It is always negative

(subatmospheric) during normal

resting respiratory cycle.

Definition:

It is the pressure inside the

pleural sac.

►It is always negative

(subatmospheric) during normal

resting respiratory cycle.

a) Over growth of the

thoracic cage than the

lung.

b) Elastic recoil of the

lung against chest wall.

a) Over growth of the

thoracic cage than the

lung.

b) Elastic recoil of the

lung against chest wall.

a) During normal expiration I.P.P. is -3 mmHg.b) During normal inspiration I.P.P. is -6 mmHg.c) During forced inspiration I.P.P. is -30 mmHg.d) During forced expiration the I.P.P. is + 40 mmHg.

a) During normal expiration I.P.P. is -3 mmHg.b) During normal inspiration I.P.P. is -6 mmHg.c) During forced inspiration I.P.P. is -30 mmHg.d) During forced expiration the I.P.P. is + 40 mmHg.

1) It helps the expansion of the lungs during inspiration.2) It helps the venous return from the extrathoracic veins. 3) It helps flow of lymph from extrathoracic lymph vessels.4) It helps flow of blood through the pulmonary vessels. 5) It is a measurement of elastic recoil of the lung.

1) It helps the expansion of the lungs during inspiration.2) It helps the venous return from the extrathoracic veins. 3) It helps flow of lymph from extrathoracic lymph vessels.4) It helps flow of blood through the pulmonary vessels. 5) It is a measurement of elastic recoil of the lung.