lecture 3 lungs & pleura

Lungs & pleura

By

Dr. Noura El Tahawy

MD., Ph.D.,

Faculty of Medicine,

El Minia University

www.slideshare.net/drnosman

Cross-section of the thorax showing the position of the mediastinum, lungs & pleural

cavities .

Subdivisions of the mediastinum.

Pleura

Pleural cavity

• The two pleural cavities are situated on either side of the mediastinum

• Each pleural cavity is completely lined by a mesothelial membrane called the pleura.

• The outer surface of each lung is covered by pleura

• Each lung remains attached to the mediastinum by a root formed by the airway,

pulmonary blood vessels, lymphatic tissues, and nerves.

• The pleura lining the walls of the cavity is the parietal pleura, whereas that reflected

from the mediastinum at the roots and onto the surfaces of the lungs is the visceral

pleura.

• Only a potential space normally exists between the visceral pleura covering lung and

the parietal pleura lining the wall of the thoracic cavity

• The lung does not completely fill the potential space of the pleural cavity, resulting in

recesses, which do not contain lung and are important for accommodating changes in

lung volume during breathing.

• The costodiaphragmatic recess, which is the largest and clinically most important

recess, lies inferiorly between the thoracic wall and diaphragm .

Formation of pleural

cavity during lung

development

Cross-section of the thorax showing the position of the mediastinum, lungs & pleural

cavities .

Parietal pleural reflections and recesses.

Pleural

cavities.

Lateral view of the upper

opening of the thoracic cage

showing how the apex of the

lung projects superiorly into the

root of the neck. The apex of the

lung is covered with visceral and

parietal layers of pleura and is

protected by the suprapleural

membrane, which is a

thickening of the endothoracic

fascia .

Section through an

intercostal space

. B .Structures penetrated by

a needle when it passes

from skin surface to pleural

cavity. Depending on the

site of penetration, the

pectoral muscles will be

pierced in addition to the

serratus anterior muscle .

Lungs

Dr. Noura El Tahawy

Surfaces & borders of the lungs

• Each lung has a half-cone shape, with a base, apex, two surfaces and three borders

• The base sits on the diaphragm .

• The apex projects above rib I and into the root of the neck .

• The two surfaces-the costal surface lies immediately adjacent to the ribs and intercostal

spaces of the thoracic wall. The mediastinal surface lies against the mediastinum anteriorly

and the vertebral column posteriorly and contains the comma-shaped hilum of the lung

through which structures enter and leave .

• The three borders-the inferior border of the lung is sharp and separates the base from the

costal surface. The anterior and posterior borders separate the costal surface from the

medial surface. Unlike the anterior and inferior borders, which are sharp, the posterior border

is smooth and rounded .

Lungs.

Root& hilum of the lung

• In the mediastinum, the vagus nerves pass immediately posterior to the roots of the

lungs, while the phrenic nerves pass immediately anterior to them. There is a thin

blade-like fold of pleura projects inferiorly from the root of the lung and extends from

the hilum to the mediastinum. This structure is the pulmonary ligament

• Within each root and located in the hilum are :

• a pulmonary artery ;

• two pulmonary veins ;

• a main bronchus ;

• bronchial vessels ;

• nerves; and lymphatics

• Generally, the pulmonary artery is superior at the hilum, the pulmonary veins are

inferior, and the bronchi are somewhat posterior in position .

• On the right side, the lobar bronchus to the superior lobe branches from the main

bronchus in the root, unlike on the left where it branches within the lung itself, and is

superior to the pulmonary artery .

Roots and hila of the lungs.

A. Right lung.

B. Major

structures

related to the

right lung

(mediastinal

surface).

•These include :

•the heart (Rt atrium)

• inferior vena cava,

•superior vena cava

• esophagus .

• right subclavian

artery and vein arch

over and are related

to the superior lobe of

the right lung as they

pass over the dome of

cervical pleura and

into the axilla .

A. Left lung.

B. Major structures

related to the left

lung (mediastinal

surface).

•These include:

•the heart (Lt. ventricle),

•aortic arch

•Descending thoracic

aorta

•esophagus.

•left subclavian artery

and vein arch over and

are related to the

superior lobe of the left

lung as they pass over

the dome of cervical

pleura and into the

axilla.

Bronchial tree&

Broncho-pulmonary Segments

Bronchial tree

• Bronchial tree: Trachea is a flexible tube that extends from vertebral level CVI in the lower neck to

vertebral level T4 in the mediastinum where it bifurcates into a right and a left main bronchus .

• The trachea is held open by 'C-shaped' transverse cartilage rings embedded in its wall-the open part of

the 'C' facing posteriorly. The posterior wall of the trachea is composed mainly of smooth muscle .Each

main bronchus enters the root of a lung and passes through the hilum into the lung itself. The right main

bronchus is wider and takes a more vertical course through the root and hilum than the left main

bronchus . Therefore, inhaled foreign bodies tend to lodge more frequently on the right side than on the

left.

• The main bronchus divides within the lung into lobar bronchi (secondary bronchi), each of which

supplies a lobe. On the right side, the lobar bronchus to the superior lobe originates within the root of the

lung. The lobar bronchi further divide into segmental bronchi (tertiary bronchi), which supply

bronchopulmonary segments.

• Within each bronchopulmonary segment, the segmental bronchi give rise to multiple generations of

divisions and, ultimately, to bronchioles, which further subdivide and supply the respiratory surfaces.

The walls of the bronchi are held open by discontinuous elongated plates of cartilage, but these are not

present in bronchioles.

A. Bronchial tree. B. Bronchopulmonary segments.

Bronchopulmonary segments

• bronchopulmonary segment is the area of lung supplied by a segmental bronchus

and its accompanying pulmonary artery branch .Tributaries of the pulmonary vein

tend to pass intersegmentally between and around the margins of segments.

• Each bronchopulmonary segment is shaped like an irregular cone with the apex at

the origin of the segmental bronchus and the base projected peripherally onto the

surface of the lung .

• Clinical note: A bronchopulmonary segment is the smallest, functionally

independent region of a lung and the smallest area of lung that can be isolated and

removed without affecting adjacent regions.

• There are ten bronchopulmonary segments in each lung (some of them fuse in the

left lung)

A. Bronchial tree. B. Bronchopulmonary segments.

Bronchopulmonary segments. A. Right lung. B. Left lung.

(Bronchopulmonary segments are numbered and named)

Bronchopulmonary segments. A. Right lung. B. Left lung.

(Bronchopulmonary segments are numbered and named)

Blood supply of the lungs

Bronchial arteries and veins

The bronchial arteries and veins constitute the 'nutritive' vascular system of the pulmonary

tissues (bronchial walls and glands, walls of large vessels, and visceral pleura).

The bronchial arteries originate from the thoracic aorta or one of its branches :

1. a single right bronchial artery normally arises from the third posterior intercostal

artery (but occasionally, it originates from the upper left bronchial artery

2. two left bronchial arteries arise directly from the anterior surface of the thoracic

aorta: -the superior left bronchial artery arises at vertebral level TV, and the inferior

one inferior to the left bronchus .

The bronchial arteries run on the posterior surfaces of the bronchi and ramify in the lungs

to supply pulmonary tissues

.

The bronchial veins drain into :

either the pulmonary veins or the left atrium; and

into the azygos vein on the right or into the superior intercostal vein or hemiazygos vein on

the left .

Pulmonary vessels.

A. Diagram of an

anterior view. B.

Axial computed

tomography image

showing the left

pulmonary artery

branching from the

pulmonary trunk.

C. Axial computed

tomography image

(just inferior to the

image in B)

showing the right

pulmonary artery

branching from the

pulmonary trunk.

Pulmonary innervation

Lymphatic drainage of

lungs.

Surface anatomy of the lungs &

pleura

Surface anatomy of the lungs

• The apex of the lung projects into the neck. It can be mapped out on the anterior surface of the body by drawing a curved

line, convex upward, from the sternoclavicular joint to a point 1 in. (2.5 cm) above the junction of the medial and

intermediate thirds of the clavicle

• The anterior border of the right lung begins behind the sternoclavicular joint and runs downward, almost reaching the

midline behind the sternal angle. It then continues downward until it reaches the xiphisternal joint

• The anterior border of the left lung has a similar course, but at the level of the fourth costal cartilage it deviates laterally

and extends for a variable distance beyond the lateral margin of the sternum to form the cardiac notch . This notch is

produced by the heart displacing the lung to the left. The anterior border then turns sharply downward to the level of the

xiphisternal joint.

• The lower border of the lung in midinspiration follows a curving line, which crosses the 6th rib in the midclavicular line

and the 8th rib in the midaxillary line, and reaches the 10th rib adjacent to the vertebral column posteriorly. It is important

to understand that the level of the inferior border of the lung changes during inspiration and expiration.

• The posterior border of the lung extends downward from the spinous process of the 7th cervical vertebra to the level of the

10th thoracic vertebra and lies about 1.5 in. (4 cm) from the midline

• The oblique fissure of the lung can be indicated on the surface by a line drawn from the root of the spine of the scapula

obliquely downward, laterally and anteriorly, following the course of the sixth rib to the sixth costochondral junction. In the

left lung the upper lobe lies above and anterior to this line; the lower lobe lies below and posterior to it.

• In the right lung is an additional fissure, the horizontal fissure ,which may be represented by a line drawn horizontally along

the fourth costal cartilage to meet the oblique fissure in the midaxillary line. Above the horizontal fissure lies the upper lobe

and below it lies the middle lobe; below and posterior to the oblique fissure lies the lower lobe.

Surface anatomy of the pleura

• The boundaries of the pleural sac can be marked out as lines on the surface of the body. The lines, which indicate the limits of the parietal pleura where it lies close to the body surface, are referred to as thelines of pleural reflection.

• The cervical pleura bulges upward into the neck and has a surface marking identical to that of the apex of the lung. A curved line may be drawn, convex upward, from the sternoclavicular joint to a point 1 in. (2.5 cm) above the junction of the medial and intermediate thirds of the clavicle

• The anterior border of the right pleura runs down behind the sternoclavicular joint, almost reaching the midline behind the sternal angle. It then continues downward until it reaches the xiphisternal joint. Theanterior border of the left pleura has a similar course, but at the level of the fourth costal cartilage it deviates laterally and extends to the lateral margin of the sternum to form the cardiac notch. (Note that the pleural cardiac notch is not as large as the cardiac notch of the lung.) It then turns sharply downward to the xiphisternal joint

• The lower border of the pleura on both sides follows a curved line, which crosses the 8th rib in the midclavicular line and the 10th rib in the midaxillary line, and reaches the 12th rib adjacent to the vertebral column—that is, at the lateral border of the erector spinae muscle Note that the lower margins of the lungs cross the 6th, 8th, and 10th ribs at the midclavicularlines, the midaxillary lines, and the sides of the vertebral column, respectively; the lower margins of the pleura cross, at the same points, the 8th, 10th, and 12th ribs, respectively. The distance between the two borders corresponds to the costodiaphragmatic recess .

Surface markings of lungs and parietal pleura on the anterior thoracic wall

Surface markings of the lungs and parietal pleura on the posterior thoracic wall .

Surface markings of the lungs and parietal pleura on the lateral thoracic walls .

Bronchoscopy

• Patients who have an endobronchial lesion (i.e. a

lesion within a bronchus) may undergo

bronchoscopic evaluation of the trachea and its main

branches. The bronchoscope is passed through the

nose into the oropharynx and is then directed by a

steerable control system past the vocal cords into the

trachea. The bronchi are inspected and, if necessary,

small biopsies are obtained.

Bronchoscopic

evaluation.

A. Of the lower end of

the trachea and its

main branches.

B. B. Of tracheal

bifurcation showing

a tumor at the

carina.

Bronchoscopic

evaluation. A. Of the

lower end of the trachea

and its main branches.

B. Of tracheal

bifurcation showing a

tumor at the carina.

Reviews

Cross-section of the thorax showing the position of the mediastinum.

Lateral view of the mediastinum.

Subdivisions of the mediastinum.

Questions

• Mention the surface anatomy of the lungs & pleura

• Give an account on the anatomy of broncho-pulmonary segments& their clinical importance

• Give an account on the relations of the medial surface of the Right lung

• Give an account on the relations of the medial surface of the Left lung

• Complete the following statements;

--- Nerve supply of the parietal pleura is ………….…, while that of pulmonary (visceral) pleura

is ……….

------ The root of the lung lies opposite …, ….., ….... Vertebrae.

---- The structures passing through the hilum of the lung are:

1 ………….. 2 ……………..3 ………….4 …………… 5 ………………6………..

-----The arterial supply of the lung is derived from ……………………artery, which is a branch

from ………... …. In the right lung & from …………………..…… in the left lung

____ The pulmonary veins drain into …………….. while the bronchial veins drain into ……….

Thank you