RESPIRATORY SYSTEM EXTERNAL RESPIRATION :- Exchange of

gases between the blood and the lungs is called External Respiration .

Internal respiration :- Exchange of gases between the blood and the cells is called Internal Respiration.

Plura and plural cavity The pleura consists of a closed sac of

serous membrane (one for each lung) which contains a small amount of serous fluid. The lung is pushed into this sac so that it forms two layers: one adheres to the lung and the other to the wall of the thoracic cavity

THE VISCERAL PLEURA• This is adherent to the lung, covering

each lobe and passing into the fissures that separate them.

THE PARIETAL PLEURA• This is adherent to the inside of the chest

wall and the thoracic surface of the diaphragm. It is not attached to other structures in the mediastinum and is continuous with the visceral pleura round the edges of the hilum.

THE PLEURAL CAVITY • This is only a potential space and contains no

air, so the pressure within is negative relative to atmospheric pressure. In health, the two layers of pleura are separated by a thin film of serous fluid (pleural cavity), which allows them during breathing.

The organs of the Respiratory system are

Nose Pharynx Larynx trachea Two bronchi Bronchioles and smaller air passages Two lungs and their covering Muscles of breathing- the intercostals

muscles and the diaphragm.

larynx The larynx or ‘voice box’ links the

laryngopharynx and the trachea . It lies in front of the laryngopharynx and the 3rd 4th 5th and 6th cervical vertebrae . Until puberty there is little difference in the size of the larynx between the sex .thereafter it grows larger in the male , which explains the prominence of the ‘Adam’s apple’ and the generally deeper voice .

Structures associated with the larynx

Superiorly- the hyoid bone and the root of the longue .

Inferiorly –it is continuous with the trachea .

Anteriorly – the muscles attached to the hyoid bone and the muscles of the neck.

Posteriorly- the laryngopharynx and 3rd -6th cervical vertebrae

Laterally – the lobes of the thyroid gland .

structure Cartilage The larynx is composed of several irregularly

shaped cartilages attached to each other by ligaments and membranes .the main cartilages are :-

1 thyroid cartilage 1 cricoids cartilage 2 arytenoids cartilages 1 epiglottis. First 3 are hyaline cartilage And last 4th elastic cartilage