Lungs | The lungs are the principal of organs of respiration. The two lungs are situated in the thoracic cavity, one on either side of the mediastinum enclosed in the plural sac. The main function of lungs is to oxygenated the blood.right lung is large and heavier than left lung.
The right lung weight is about 700g and left lung weight is about 650g. Right lung has three lobes and the left lung has two lobes. The lobes are separated by deep prominent fissure on the surface of the lung and are supplied by two lobar bronchi.
lungs are attached to trachea and heart by principal bronchi and pulmonary vessels, respectively.
In new born baby and people living in clean environment, the lungs are rosy pink in colour, but in people living in polluted areas or those who are smokers, have the lungs are brown or black in colour, and mottled in appearance due to inhaled carbon particles.
In adult, the lungs are spongy in texture and crepitate on touch due to the presence of air in their alveoli.
EXTERNAL FEATURES OF LUNGS
Each lung presents the following features -
1- Apex
2- Base
3- Three borders(Anterior, posterior and inferior)
4- Two surface (costal and medial)
APEX
The apex is rounded superior end of the lung. It extend into root of the neck about 3cm superior to the anterior end of the 1st rib and 2.5cm above the medial one-third of the clavicle. It is covered by cervical pleura and supra pleural membrane
BASE
The base is lower semilunar concave surface, which rests on the dome of the diaphragm, hence it is also sometimes called Diaphragmatic surface
BORDER
The border of the lungs are follow;
1- Anterior border - it is thin and shorter than the posterior border. The anterior border of right lung is vertical. The anterior border of left lung presents a wide Cardiac notch, which occupied by the heart and pericardium
2- Posterior border - It is thick and rounded. It extends from spine of C7 vertebra to the spine of T10 vertebra.
3- Inferior border - it is semilunar in shape and separates the costal and medial surface.
SURFACE
The surfaces of the lungs are costal and medial-
COSTAL SURFACE
It is a large , smooth and convext is covered by the costal pleura and end-thoracic fascia.
MEDIAL SURFACE
It is divided into two parts
A) small posterior vertebral part
B) large anterior mediastinal part
LOBES AND FISSURE
The right lung is divided into three lobes: superior, Medial and inferior
BY TWO FISSURE
A) An oblique fissure
B) An horizontal fissure
Left lung is divided into two lobes: a) Superior and b) inferior by an Oblique fissure.
OBLIQUE FISSURE - A long oblique fissure runs obliquely downwards and forward crossing the posterior border about 6cm below the apex and inferior border about 7.5cm lateral to the midline. It separates the superior and middle lobe from the inferior lobe.
ROOTS OF THE LUNGS
The root of lung is a short broad pedicle connecting the medial surface of the lung with the mediastinum. It consists of structure entering and leaving the lung at hilum.
The root of lung consist of the following structure
1- - principal bronchus in the left lungs
2- pulmonary artery
3- pulmonary vein
4- bronchial artery
5- bronchial vein
6- Lymphatic of the lungs
INTERNAL FEATURES OF THE LUNGS
The lung is mainly made up of Intrapulmonary bronchial tree, which is concerned with the conduction of air to and fro from the lung, and pulmonary units, which are concerned with gaseous exchange .
BRONCHIAL TREE
The bronchial tree consist of principal bronchus, lobar bronchi, terminal bronchioles and respiratory bronchioles .
PRINCIPAL BRONCHI
The trachea divides outside the lungs, at the level of the lower border of T4 vertebra into two primary bronchi left and right lung
LOBAR BRONCHI
On entering the lung, the right principal bronchus divides three lobar bronchi, one for each lobe of the right lung. The left principal bronchus on entering the lung divides into two lobar one for each lobe of the left lung
PULMONARY UNITS
Each Pulmonary units consists of
1- alveolar ducts
2- atria
3- alveoli
ARTERIAL SUPPLY OF THE LUNGS
The lungs are supplied by two sets of arteries
1- Bronchial arteries
2- Pulmonary arteries
Bronchial vein
The bronchial vein drain the deoxygenated blood from the bronchial tree and bronchial tissue.
Pulmonary vein
The pulmonary vein drain the oxygenated blood from the lungs, there two pulmonary vein on each side.
LYMPHATIC DRAINAGE
The lymphatic drainage of the lung is clinically important because lung cancer spreads by lymphatic path.
The lymph from the lung is drained by two sets of lymph vessels.
1- Superficial vessels
2- Deep vessels
NERVE SUPPLY
The lung is supplied by both parasympathetic and sympathetic nerve filers.
The PARASYMPATHETIC FIBRES are derived from the VAGUS NERVE and SYMPATHETIC FIBRES derived from T2 and T5 spinal segments.
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