No. 10No. 10

1. Trachea1. Trachea 2. Bronchi2. Bronchi 3. Lungs3. Lungs 4. Pleura4. Pleura 5. mediastinum5. mediastinum

Section 4 The TracheaSection 4 The Trachea

The The tracheatrachea is a tube approximately 2.0 cm in diamete is a tube approximately 2.0 cm in diameter and 11 cm long.r and 11 cm long.

LocationLocation:: It is located in the midline of neck and upper thorax, anIt is located in the midline of neck and upper thorax, an

d in front of the esophagus.d in front of the esophagus. It extends from the larynx at the lower border of the criIt extends from the larynx at the lower border of the cri

coid cartilage at the level of sixth cervical vertebra to tcoid cartilage at the level of sixth cervical vertebra to the level of the sternal angle (corresponding) to the lohe level of the sternal angle (corresponding) to the lower border of the fourth thoracic vertebra, where it diwer border of the fourth thoracic vertebra, where it divides into the right and left principal bronchi.vides into the right and left principal bronchi.

CompositionComposition:: The wall of trachea is mainly composed of aboThe wall of trachea is mainly composed of abo

ut 15ut 15 ～～ 30 C-shaped rings of hyaline cartilage 30 C-shaped rings of hyaline cartilage keep the lumen of the trachea open.keep the lumen of the trachea open.

But the posterior wall of the trachea is closed But the posterior wall of the trachea is closed by the tracheal muscle and lies against the antby the tracheal muscle and lies against the anterior surface of the esophagus permitting the erior surface of the esophagus permitting the esophagus to expand during swallowing.esophagus to expand during swallowing.

Carina of tracheaCarina of trachea:: It is a sagittal semilunar ridge inside the It is a sagittal semilunar ridge inside the

bifurcation of trachea, which can be seebifurcation of trachea, which can be seen through bronchoscope and used as a gn through bronchoscope and used as a guide to the bronchi.uide to the bronchi.

Section 5 The BronchiSection 5 The Bronchi

The trachea terminates at the level of fourth thThe trachea terminates at the level of fourth thoracic vertebra and divides into the right and loracic vertebra and divides into the right and left principal bronchi.eft principal bronchi.

The The right principal bronchusright principal bronchus is about 2 is about 2 ～～ 3 c3 cm long and is shorter, wider and more vertical m long and is shorter, wider and more vertical in position than the left.in position than the left.

The The left principal bronchusleft principal bronchus is longer, about is longer, about 44 ～～ 5 cm long, finer and less vertical.5 cm long, finer and less vertical.

So the foreign objects from the trachea usually So the foreign objects from the trachea usually pass to the right bronchus.pass to the right bronchus.

Bronchial treeBronchial tree:: As entering the lungs, the principal As entering the lungs, the principal

bronchus branches to form bronchus branches to form lobar bronchilobar bronchi which enter the lobes of lung.which enter the lobes of lung.

The lobar bronchi continue to branch, The lobar bronchi continue to branch, forming still smaller bronchi called the forming still smaller bronchi called the segmental bronchisegmental bronchi, which are , which are subdivided into the subdivided into the bronchiolesbronchioles..

ramify into even smaller tubes called the ramify into even smaller tubes called the terminal bronchiolesterminal bronchioles..

These branches resemble a tree and so These branches resemble a tree and so are called the bronchial tree.are called the bronchial tree.

Section 6 The LungsSection 6 The Lungs

The lungs are the essential organs of The lungs are the essential organs of respiration.respiration.

Healthy lungs always contain some air so Healthy lungs always contain some air so they may float in water. In the newborn they may float in water. In the newborn which has not breath, the lungs will not which has not breath, the lungs will not float in water. At birth the lungs are float in water. At birth the lungs are pinkish-white but they turn dark trey with pinkish-white but they turn dark trey with age and become almost black due to age and become almost black due to carbonaceous deposits.carbonaceous deposits.

LocationLocation:: The lungs are situated one on each side The lungs are situated one on each side

within the thorax, and separated from ewithin the thorax, and separated from each other by the heart and other contenach other by the heart and other contents of the mediastinum.ts of the mediastinum.

ⅠⅠ. The External Features of Lungs. The External Features of Lungs

Each lung is shaped somewhat like a Each lung is shaped somewhat like a cone, with an apex, a base, two cone, with an apex, a base, two surfaces and three borders.surfaces and three borders.

The right lung is shorter than the left The right lung is shorter than the left one because the right dome of the one because the right dome of the diaphragm is higher, and it is wider diaphragm is higher, and it is wider because the heart and pericardium because the heart and pericardium bulge more to the left.bulge more to the left.

1. One apex and one base1. One apex and one base

1) The 1) The apex of lungapex of lung is rounded and extends to is rounded and extends to about 2about 2 ～～ 3 above the level of the medial one-3 above the level of the medial one-third of the clavicle.third of the clavicle.

2) The 2) The base of lungbase of lung is concave and related to t is concave and related to the diaphragm which separates the right lung frhe diaphragm which separates the right lung from the liver and the left lung from the stomacom the liver and the left lung from the stomach, spleen and liver, so the base of lung is also ch, spleen and liver, so the base of lung is also called the alled the diaphragmatic surfacediaphragmatic surface..

2. Two surfaces2. Two surfaces

The lung possesses a costal surface and The lung possesses a costal surface and a medial surface.a medial surface.

1) The 1) The costal surfacecostal surface is smooth, convex is smooth, convex and related to the inner surface of the riand related to the inner surface of the ribs, costal cartilages and intercostal spacbs, costal cartilages and intercostal spaces.es.

2) The 2) The medial surfacemedial surface is related to the m is related to the mediastinum, so it is also called the mediaediastinum, so it is also called the mediastinal surface.stinal surface.

The hilum of lung and root of lungThe hilum of lung and root of lung:: Near the center of the medial surface, there is a depreNear the center of the medial surface, there is a depre

ssion called the ssion called the hilum of lung (hilus)hilum of lung (hilus). The hilus is the . The hilus is the region where the structures that form the root of the lregion where the structures that form the root of the lung-that is, the bronchus, blood vessels, lymphatics aung-that is, the bronchus, blood vessels, lymphatics and nerves-enter or leave the lung.nd nerves-enter or leave the lung.

The structures entering and emerging the hilum is callThe structures entering and emerging the hilum is called the ed the root of lungroot of lung, which is short broad pedicle and c, which is short broad pedicle and consists of the bronchi, pulmonary artery and veins, neonsists of the bronchi, pulmonary artery and veins, nerves, bronchial vessels, lymphatics and lymph nodes.rves, bronchial vessels, lymphatics and lymph nodes.

3. Three borders3. Three borders The borders of lung includes anterior, posterioThe borders of lung includes anterior, posterio

r and inferiors.r and inferiors. The The anterior borderanterior border is thin and sharp, having is thin and sharp, having

a deep notch at the forth and fifth intercostals a deep notch at the forth and fifth intercostals spaces in the left lung, called the spaces in the left lung, called the cardiac notccardiac notchh of left lungof left lung, beneath which is the , beneath which is the lingula of lingula of left lungleft lung..

The The posterior borderposterior border is round. is round. The The inferior borderinferior border is also sharp and separate is also sharp and separate

s the base of lung from the costal and medial ss the base of lung from the costal and medial surfaces.urfaces.

ⅡⅡ. The Lobes and Segments of . The Lobes and Segments of LungsLungs

Fissures and lobesFissures and lobes:: Each lung is divided into Each lung is divided into superiorsuperior

and and inferior lobesinferior lobes by an by an oblique oblique fissurefissure. The right lung is further . The right lung is further divided by a horizontal fissure, which divided by a horizontal fissure, which bounds a bounds a middle lobemiddle lobe..

The right lung therefore has three The right lung therefore has three lobes, whereas the left has only two. lobes, whereas the left has only two.

Bronchopulmonary segmentsBronchopulmonary segments:: Each lung is subdivided by connective tissue pEach lung is subdivided by connective tissue p

artitions into smaller units called artitions into smaller units called bronchopulbronchopulmonary segmentsmonary segments. .

Each bronchopulmonary segment represents tEach bronchopulmonary segment represents the portion of the lung that is supplied by a spehe portion of the lung that is supplied by a specific tertiary bronchus. Each lung has ten segmcific tertiary bronchus. Each lung has ten segments.ents.

The bronchopulmonary segments are importaThe bronchopulmonary segments are important surgically because a diseased segment can nt surgically because a diseased segment can be removed without having to remove an entirbe removed without having to remove an entire lobe or the entire lung. Also, disease does noe lobe or the entire lung. Also, disease does not spread so easily across the partitions that set spread so easily across the partitions that separate the segments, so pathology tends to be parate the segments, so pathology tends to be confined to one or several segments rather thaconfined to one or several segments rather than spreading freely throughout the lungs.n spreading freely throughout the lungs.

Section 7 The PleuraSection 7 The Pleura

Each lung is enclosed in a double-walled Each lung is enclosed in a double-walled the the pleurapleura. Both layers of the pleura are . Both layers of the pleura are formed of serous membrane that lines the formed of serous membrane that lines the inner surface of the thorax and the surface inner surface of the thorax and the surface of the thorax and the surfaces of lungs.of the thorax and the surfaces of lungs.

The portion of the pleura that adheres The portion of the pleura that adheres firmly to the lungs is the firmly to the lungs is the visceral pleuravisceral pleura..

The portion that lines the walls of the The portion that lines the walls of the thoracic cavity is the thoracic cavity is the parietal pleuraparietal pleura..

ⅠⅠ. The Parietal Pleura. The Parietal Pleura

The serous membrane lining the inner sThe serous membrane lining the inner surface of chest wall is called the parietal urface of chest wall is called the parietal pleura.pleura.

According to the regions the parietal pleAccording to the regions the parietal pleura is divided into four portions:ura is divided into four portions:

① ① thethe costal pleuracostal pleura,, ② ② he he diaphragmatic pleuradiaphragmatic pleura,, ③ ③ the the mediastinal pleuramediastinal pleura ,, ④ ④ the the cupola of pleuracupola of pleura..

ⅡⅡ. The Visceral Pleura. The Visceral Pleura

The pleura is reflected from the mediastinum tThe pleura is reflected from the mediastinum to the surface of lung, where it is called visceral o the surface of lung, where it is called visceral pleura covering the lungs and extending into tpleura covering the lungs and extending into the fissures of lung.he fissures of lung.

Below the root of lung the mediastinal pleura Below the root of lung the mediastinal pleura extends as a double layer to the mediastinal sextends as a double layer to the mediastinal surface of lung. This double layer is called the urface of lung. This double layer is called the ppulmonary ligamentulmonary ligament..

ⅢⅢ. The Pleural Cavity and . The Pleural Cavity and RecessesRecesses

Ⅰ Ⅰ) The Pleural Cavity) The Pleural Cavity The visceral and parietal layers are continuous The visceral and parietal layers are continuous

at the hilus of the lung. between the two layers at the hilus of the lung. between the two layers of the pleura is an extremely narrow of the pleura is an extremely narrow pleural cpleural cavityavity, which is filled with , which is filled with pleural fluidpleural fluid. The pl. The pleural fluid is secreted by the pleura, and it acts eural fluid is secreted by the pleura, and it acts as a lubricant to reduce the friction between tas a lubricant to reduce the friction between the two layers during respiratory movements.he two layers during respiratory movements.

The two pleural cavities are separated from eaThe two pleural cavities are separated from each other by the mediastinum.ch other by the mediastinum.

Ⅱ Ⅱ) The Pleural Recesses) The Pleural Recesses Costodiaphragmatic recessCostodiaphragmatic recess:: In quiet breathing the inferior border of the luIn quiet breathing the inferior border of the lu

ng does not completely extend the inferior mang does not completely extend the inferior margin of the pleural reflexion, so that the costal rgin of the pleural reflexion, so that the costal and diaphragmatic pleurae are in contact with and diaphragmatic pleurae are in contact with each other here, the intervening narrow slit tereach other here, the intervening narrow slit termed the med the costodiaphragmatic recesscostodiaphragmatic recess. In quiet . In quiet respiration the lower limit of lung is about 5 crespiration the lower limit of lung is about 5 cm above the lower limit of the pleura.m above the lower limit of the pleura.

Costomediastinal recessCostomediastinal recess:: A similar condition present behind the stA similar condition present behind the st

ernum, between the costal and mediastiernum, between the costal and mediastinal pleurae it is termed the nal pleurae it is termed the costomediacostomediastinal recessstinal recess..

ⅣⅣ. The Projection of the Inferior . The Projection of the Inferior Margins of Lungs and PleuraeMargins of Lungs and Pleurae

On the surface of the body, the projectioOn the surface of the body, the projection of the inferior margins of the lungs and n of the inferior margins of the lungs and pleurae are shown in table 1:pleurae are shown in table 1:

The inferior margins of pleurae is the cosThe inferior margins of pleurae is the costodiaphragmatic lines of reflexion of the todiaphragmatic lines of reflexion of the pleuraepleurae

Table 1 The inferior margins of Table 1 The inferior margins of lungs and pleuraelungs and pleurae

Midclavicular linMidclavicular line e

Midaxillary linMidaxillary line e

Posterior median Posterior median line line

Inferior Inferior margin of margin of lungs lungs

66thth fib fib 88thth rib rib On the level of TOn the level of T10 10

spinal process spinal process

Inferior Inferior margin of margin of pleurae pleurae

88thth rib rib 1010thth rib rib On the level of TOn the level of T12 12

spinal process spinal process

Section 8 The MediastinumSection 8 The Mediastinum

The The mediastinummediastinum is generally defined as the iis generally defined as the interval between the right and left pleural sacs.nterval between the right and left pleural sacs.

LocationLocation:: It extends from the sternum in front to vertebrIt extends from the sternum in front to vertebr

al column behind, and from the thoracic inlet al column behind, and from the thoracic inlet above to the diaphragm below.above to the diaphragm below.

Its lateral wall is the mediastinal pleura of botIts lateral wall is the mediastinal pleura of both sides.h sides.

DivisionDivision:: The mediastium is divided into The mediastium is divided into superiorsuperior and and inferior inferior

mediastinamediastina by the line drawn horizontally from the st by the line drawn horizontally from the sternal angle to the lower border of 4th thoracic vertebrernal angle to the lower border of 4th thoracic vertebra.a.

The inferior mediastinum is subdivided into an The inferior mediastinum is subdivided into an anterianterior mediastinumor mediastinum in front of pericardium, a in front of pericardium, a middle memiddle mediastinumdiastinum containing the pericardium with heart and containing the pericardium with heart and great vessels, and the great vessels, and the posterior mediastinumposterior mediastinum betwe between pericardium and vertebral column.en pericardium and vertebral column.

The posterior mediastinum extends to the lower bordThe posterior mediastinum extends to the lower border of the 8th thoracic vertebra, its main contents are ter of the 8th thoracic vertebra, its main contents are the bronchi, esophagus, vagus and phrenic nerves, thohe bronchi, esophagus, vagus and phrenic nerves, thoracic duct etc.racic duct etc.