Lungs

Lungs are composed of bronchi, and smaller air passage, alveoli, connective tissue, blood vessels, lymph vessels and nerves.

Two lungs one lying on each side of the midline in the thoracic cavity.

Left and right lung are separated by "mediastinum" .

Lungs are paired spongy, air filled organ located on each either side of the chest (throax).

Right lung weight - 700 gm, and right lung is heavier 50-100 gm than left lung.

Right lung thicker and broader than left lung.

Lungs are spongy in texture.

In young, lungs are brown or grey colour.

Adult right lung weight;  375- 550gm

Left lung weight; 325- 450gm

Right lung are more prone to infection.

Parts of Lungs

Lung has -

1. An apex

2. A base

3. Two surface

a. Medial surface

b. Costal surface

1. Apex

Apex is at upper end.

It is rounded rise into root of neck.

Structure associated with it are first rib and blood vessels and nerves in root of neck. Boundary between neck and thorax.

2. Base

Base is broad inferior surface of lung.

Base rest of Diaphragm.

It is concave and semilunar in shape.

3. Surface of lungs

1. Medial surface

Medial surface of lungs face towards center of chest.

Medial surface has roughly triangular shaped area called Hilus (hilum; wedge shaped area located on central portion of each lung) at level of 5th, 6th, 7th  thoracic vertebrae.

Hilus region is where the bronchi, arteries, vein and nerves enter and exit the lungs.

Concavity is greater on the left lung than on the right lung because of position of Heart.

Structures that enter and exit at the hilum are bronchi, 1pulmonary artery, 2 pulmonary veins, 1 bronchial artery, bronchial veins, lymph vessels, parasympathetic and sympathetic nerves.

These structures are held together by pleura and convective tissue and constitute root of the lung.

2. Costal surface

Costal surface of lungs is smooth and convex.

Costal surface of lungs is covered by costal pleura which separates lung from; ribs, costal cartilage and intercostal muscles (muscle between ribs).

Lobes and Fissures of Lungs

Lungs are divided into lobes. Fissures separates these lobes from each other.

Lobes of Lungs

Right lung divided into 3 lobes-

1. Superior lobe

2. Middle lobe

3. Inferior lobe

Divided by 2 fissure 

1. Oblique fissure

2. Horizontal fissure

Left lung divided into 2 lobes-

1. Superior lobe

2. Inferior lobe

Left lung has no middle lobe.

Divided by oblique fissure

Left lung has concavity, cardiac notch into which heart fits.

Bronchopulmonary Segments

Bronchopulmonary segment is a portion of lung supplied by a specific segmental bronchus and arteries.

Bronchopulmonary Segment in Right Lung

10 Bronchopulmonary segment in right lung-

3 in superior lobe

2 in middle lobe

5 in inferior lobe

Bronchopulmonary Segment in Left Lung 

9 Bronchopulmonary segment in left lung -

4 in upper lobe

5 in lower lobe

These bronchopulmonary segments function somewhat independently. These segments make it possible to remove one diseased segment without damaging the rest of lung.

Lobules

Bronchopulmonary segment contains small division called lobules; which are surrounded by elastic connective tissue.

A lobule has hundreds of alveoli.

It is served by lymphatic vessel, an artery, a small vein and branch from terminal bronchiole.

Fissures

Each lungs is divided into lobes by fissures. 

1. Oblique fissure

2. Horizontal fissure

1. Oblique fissure

Oblique fissure is in both lung.

In right lung- it separates the inferior lobe from middle lobe in right lung.

In left lung- Oblique fissure separated the inferior lobe from superior lobe.

2. Horizontal fissure

Horizontal fissure is in right lung only.

It separated the superior lobe from middle lobe in right lobe.

Root of Lung

Root of Lung located at the hilum of each lung.

Root of Lung is short, broad pedicle which connects medial surface of lung to mediastinum.

It is composed of structure entering and leaving at lung at hilum.

These structure are held together by pleura and convective tissue and constitute root of lung.