Lungs

Learning Objective

After reading this post you will know the following about lungs anatomy:

  • Gross features of lungs.
  • Differences between right and left lung.
  • Differences between fetal and adult lungs.
  • Structures passing through the hilum of right and left lungs.
  • Structures related to the mediastinal surface of right and left lung.
  • Bronchopulmonary segments of lungs and their cilinical significance.
  • Nerve supply of lungs
  • Lymphatic drainage of lungs.

 Gross Features of Lungs

Q. Describe lungs under the following headings:

  1. Gross features
  2. Fissures and lobes
  3. Lung root
  1. Gross features: Each lung has:      surfaces and borsders of lungs
  •  An Apex that
    • is blunt
    • extends into the neck, an inch above the medial 1/3rd of the clavicle.
    • is covered by cervical pleura and suprapleural membrane (Sibson’s fascia).
    • is related anteriorly to the subclavian artery and scalenus anterior muscle.
    • is related posteriorly to the neck of the 1st rib.
    • Is related 
    • Anteriorly to subclavian artery and vein, and scalenus anterior muscle.
    • Posteriorly to sympathetic chain, highest intercostal vein, superior intercostal artery and ventral ramus of T1 spinal nerve.
    • Laterally to scalenus medius muscle.
    • Medially 
      • On right side to right brachiocephalic vein, right phrenic nerve, brachiocephalic artery, right vagus nerve and trachea.
      • On left side to left brachiocephalic vein, left subclavian artery, left recurrent laryngeal nerve, oesophagus and thoracic duct.
  •  A Base  (Diaphragmatic surface) that:
    • is semilunar and concave
    • is related to the dome of the diaphragm.
    • is separated from the liver by the right dome of the diaphragm on the right side.
    • is separated from the fundus of the stomach and spleen by left dome of diaphragm on the left side.
  •  Three Borders:
    • Anterior border is sharp and shorter than the posterior border.
    • Posterior border is thick and rounded.
    • Inferior border is semilunar in shape .

*Anterior border of left side presents a concave CARDIAC NOTCH and the tongue shaped projection below the cardiac notch LINGULA.

  • Three Surfaces:
    • Costal surface is convex and is related to ribs and intercostal muscles.
    • Medial surface is divided into two parts:
      • Mediastina surface: Anterior 2/3rd of medial surface. It is related to the mediastinal structure..
      • Vertebral surface: Posterior 1/3rd of medial surface. Is related to vertebral bodies and intervertebral discs

2. Fissures and lobes:

  • Right lung has usually:
    • Two fissures – Oblique and transverse/horizontal
    • Three lobes – Superior, middle and inferior
  • Left lung has usually:
    • One fissure – Oblique
    • Two lobes – Superior and inferior

lungs -fissures and blog

3. Root of Lung

  • Lung root consists of the structures passing to and from the hilum of the lung to the mediastinum.
  • Lung roots lie opposite to T5 – T7 vertebrae.
  • The structures of the lung root are embedded in the connective tissue and surrounded by extension of mediastinal pleura.
  • Following structures are present in the lung root lungs:
    • Principal bronchus in the left lung and eparterial and hypearterial bronchi in the right lung
    • Pulmonary artery
    • Superior and inferior pulmonary veins
    • Bronchial arteries (one on the right side and two on the left side)
    • Bronchial veins
    • Nerves ( anterior and posterior pulmonary plexus)
    • Lymhatics from the lung.

root of lung/hilum of lung

Lung roots move downward and forward in full inspiration to allow expansion of the posterior part of the lung.

Q. Enumerate the differences between:

  1. Fetal and adult lung
  2. Right and left lung

                                                             Differences Between Fetal and Adult Lung

S.No.FETAL LUNG ADULT LUNG
1SolidPorus
2Sinks  in waterFloat in water
3Does not crepitate on touch Crepitates on touch
4Colour – pinkColour – Grey to mottled black (due to deposition of carbon)
5No air in alveoliAir in alveoli 

                                                              Differences Between Right And Left Lung

S.No.RIGHT LUNG LEFT LUNG
1ShorterLonger
2WiderLonger
3HeavierLighter
4Usually has two fissures- oblique and transverseUsually has one fissure – oblique
5Has usually three lobes- Superior, middle and inferior Has usually two lobes - Superior and  inferior
6Anterior border is straightAnterior border has a concave cardiac notch
7Base is more concave( due to liver below  the diaphragm)Base is less concave

 Q. Enumerate the important structures passing through the hilum of right and left lungs:

  1. From above downwards
  2. From before backwards
  1. From above downwards:

   

     Right Lung  Left Lung  
Eparterial bronchus,  Left Principal bronchus
Right Pulmonary artery Left Pulmonary artery 
Hyparterial bronchus Inferior pulmonary vein
Right Inferior pulmonary vein

  1. From before backwards: In both right and left lungs
  • Superior pulmonary vein
  • Pulmonary artery
  • Bronchus

 Relations of Mediastinal Surface of Lungs

Q. Draw labeled diagram  to show relations of mediastinal surface of right and left lung.

mediastinal surface of right lungmediastinal surface of left lung

   Bronchopulmonary Segments of Lungs

Q. Describe bronchopulmonary segment under the following headings:

  1. Definition
  2. Characteristic features
  3. Nomenclature
  4. Clinical significance

A  1. Definition: Bronchopulmonary segment is a  wedge shaped self  contained functionally independent respiratory unit of lung which is  aerated by tertiary or segmental bronchus.

2. Characteristic features:

  • Each bronchopulmonary segment is pyramidal in shape with apex directed towards the hilum and base towards the surface of the lung.
  • Each segment is separated from the adjacent segments by connective tissue.
  • Segmental/tertiary bronchus with bronchial vessels and a branch of pulmonary artery accompanying it are central in position.
  • There is little anastomosis between the arteries of adjacent segments.
  • Tributaries of pulmonary vein are intersegmental running in the connective tissue septa.
  • Intersegmental veins act as guide for separating the segments during surgical resection
  • It is the smallest part of the lung that can be removed without affecting the adjacent regions of the lung.

bornchopulmonary segment

3.Nomenclature: There are 10 bronchopulmonary segments in each lung. Their names and location are as follows:

Bronchopulmonary segments of right lungbronchopulmonary segments of left lung

4. Clinical significance:

  • The connective tissue septa between the adjacent bronchopulmonary segments acts as a natural barrier and prevents spread of infection between the segments.*Carcinoma and tuberculosis break through the barrier.
  • The knowledge of bronchopulmonary segments helps in:
    • Performing bronchoscopy
    • Correct interpretation of bronchogram
    • Understanding why abcess formation is more common in some segments
      • Posterior segment of upper lobe
      • Apical segment of the lower lobe
    • Natural drainage from the infected segment by adopting different postures e.g.  for drainage of apical segment of the lower lobe the patient should be asked to lie prone with head turned to one side.

Nerve Supply and Lymphatic Drainage of Lungs

Q. Describe briefly:

  1. nerve supply of lungs
  2. lymphatic drainage of lungs

A. 1. Nerve supply of lungs:Lungs are supplied by autonomic nervous  system. Sympathetic and parasympathetic fibers form anterior and posterior pulmonary plexuses in the roots of the lungs before supplying it.

Sympathetic fibers are:

  • Derived from T2 – T5 spinal segments
  • Bronchodilator
  • Vasomotor
  • Inhibitor of secretions from the glands of bronchial tree.

*Sympathomimetic drugs such as epineherine cause bronchodilation and relieve bronchial asthma ( bronchospasm).

Parasympathetic fibers are

  • Derived from the vagus nerves.
  • Bronchoconstrictor
  • Secretomotor

* Also carry afferent (sensory) fibers which are sensitive to stretch and play important role in reflex control of respiration.

2. Lymphatic drainage of lungs

Lymph from the lungs is drained by two sets of lymph vessels.

  • Superficial lymph vessels:
    • Drain the peripheral lung tissue.
    • Form the superficial (subpleural) plexus beneath the pleura.
    • Pass around the borders and fissures of lungs to drain into the bronchopulmonary lymph nodes at the hilum.
  • Deep lymph vessels:
    • Drain the bronchial tree.
    • Begin from the submucosa of bronhi.
    • Form Deep plexus around the bronchi  drain into pulmonary lymph nodes located within lungs around lobar bronchi.
    • From pulmonary lymph nodes the lymph is drained into bronchoplulmonary lymph nodes located at the hilum.

lymphatic drainage of lungs

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