Chapter 6 Respiratory System

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HISTORY

The anatomic and surgical history of the respiratory system is summarized in Table 6-1.

Table 6-1. Anatomic and Surgical History of the Respiratory System

Assyro-

Babylonia

3000 to

1000

B.C.

Described the sibilanta rhonci of lung tuberculosis: "His breathing sounds like a flute"

China 1100

B.C.

The Nei Ching classified the lungs as one of the five solid formative organs. The lungs also were said to contain the emotion of sorrow.

Egyptians 663 to

520 B.C.

The Sema Amulet represented the trachea and lungs. When depicted in color, the lung was clear, bright red, or "lung color."

Galen (ca. 130-

200 A.D.)

Described the lungs, heart, and thorax as necessary for breathing. Recorded a blood supply to the lungs coming from the aorta, but

failed to name it. Called the trachea "aspera arteria" and identified the divisions of the lung. He also noted the presence of the pleura.

Rolandus 1499 Resected part of a lung visible from a hernia of the chest wall

Leonardo da

Vinci (1452-

1519)

Dissected the bronchial vessels. One drawing shows increase in bronchial circulation in response to inflammation.

Andreas

Vesalius

16th

century

Used endotracheal intubation for anesthesia in animal surgery

De Pozze 1673 First description of pulmonary agenesis

Ruysch 1696 Claimed discovery of bronchial circulation: "I unhesitatingly avow that this vessel has not been seen before"

von Smmering

and

Reisseissen

1808 Described the bronchial circulation as the "vasa nutritia" of the lung

Antony 1823 Removed a portion of a lung attached to a large mass of pus in his patient's chest

Virchow 1847 Stated that bronchial circulation preserves pulmonary function in areas of arterial obstruction

Macewen 1878 Initiated the use of tracheal intubation for oral surgery and edema of the glottis

Block 1881 Partially removed the lungs of rabbits. He tested his methods on a cousin suffering from tuberculosis, taking out the apex of each lung.

When the operation failed, Block committed suicide.

Weinlechner 1882 Unsuccessfully removed a myxochondroma of the chest wall and middle lobe. He also resected part of the upper lobe, eliminating several

metastatic deposits.

Kroenlein 1883 Performed a two-staged lower left lung resection after the recurrence and extension of previously removed osteogenic sarcoma. The

patient recovered from the operation but died of pneumonia later.

Tuffier 1891 Performed the first successful lung resection to treat pulmonary tuberculosis by removing the apex of the right lung

1896 Developed an intratracheal tube with an inflatable cuff

Matas 1899 Developed artificial respiration via intralaryngeal insufflation

Garr and

Quincke

1901 Advocated adding intrapleural or extrapleural pneumolysis to thoracoplasty

Sauerbruch 1904 Attempted the use of positive pressure respiration, using a tight-fitting face mask, while employing his negative pressure chamber or

"pneumatic chamber"

Meltzer and

Auer

1909 Proposed the use of peroral intubation to facilitate positive pressure anesthesia

Elsberg and

Lilienthal

1910 Performed the first thoracotomy under intratracheal anesthesia

Kummel 1910 Performed an unsuccessful pneumonectomy by clamping the pedicle and leaving the clamps in situ. The patient died six days later.

Stuerz 1911 Cut the phrenic nerve to obtain relaxation of the lower lobe with tubercular adhesions

Davies 1913 Performed a dissection lobectomy using individual dissection ligature and suture of the hilar structures

Lilienthal 1914 Performed a one-stage lobectomy

Bull 1920 Reported to have performed apicolysis down to the fourth rib in 116 patients

Brun 1929 Published "Surgical Principles Underlying One-Stage Lobectomy," which gave a detailed description of one-stage lobectomy. His first case

in the study dated back to 1918.

Shenstone and

Janes

1929 Used a hilus tourniquet for lobectomy. Reported its usage in 1932.

Sauerbach and

Brunner

1930s Developed selective apical thoracoplasty

Churchill 1931 Performed dissection lobectomy, reestablishing its efficacy after Davies' 1913 procedure

Nissen 1931 Succeeded in performing a two-stage total pneumonectomy to treat diffuse bronchiectasis of the left lung. This procedure involved tying



Nissen 1931 Succeeded in performing a two-stage total pneumonectomy to treat diffuse bronchiectasis of the left lung. This procedure involved tying

off the hilum with rubber tubing and several silk ligatures, then waiting for the necrotic lung to slough off two weeks later.

Kramer and

Glass

1932 Originated the term "bronchopulmonary segments" to describe lung anatomy

Haight 1932 Performed a successful total pneumonectomy using a procedure similar to Nissen's

Bigger 1932 Performed a bronchotomy in order to remove a tumor of the left bronchus

Graham and

Singer

1933 Performed a one-stage total pneumonectomy when unexpectedly forced to resect the entire lung while treating a bronchogenic

carcinoma too close to the lobar bifurcation point

Rienhoff 1933 Introduced the modern technique of bronchial suture by cutting the cartilage at various points and using interrupted silk sutures to

suture the bronchus

Freedlander 1935 Reported an unsuccessful case of pulmonary lobectomy

Belsey and

Churchill

1939 Performed a lingulectomy, which is often thought of as the first segmental resection. They wrote, "It is suggested that the

bronchopulmonary segment may replace the lobe as the surgical unit of the lung."

Eloesser 1939 Removed an adenoma originating in the lower left lobe bronchus

Kent and

Blades

1942 Published a paper long considered the basis of the techniques of individual hilar ligation

Belsey 1944 Repaired a bronchus using fascia after removing a bronchial adenoma

Allison 1946 Reported on a procedure involving intrapericardial pneumonectomy with dissection of mediastinal tissue and lymph nodes (radical

pneumonectomy)

Thomas 1947 Performed a bronchial sleeve lobectomy

Sellors 1947 Performed a pulmonic valvotomy

Juvenelle 1947 Published report of investigation of pulmonary denervation which concluded that animals could survive lung autotransplantation

Gebauer 1948 Performed the first bronchial excision-reconstruction procedure, using a wire-supported dermal graft

Overholt and

Langer

1949 Systematized operative methods for segmental resection

Metras 1951 Described canine lung transplantation, with dogs surviving up to 29 days

Overholt 1952 Performed a simultaneous bilateral resection for bronchiectasis

Neptune 1953 Published report of attempts of en-bloc heart-lung transplantation in dogs

Bjrk and

Bagger

1954 Performed a pulmonary resection with pulmonary valvulotomy on a patient with pulmonary stenosis and pulmonary tuberculosis

Price-Thomas 1955 Performed a sleeve resection of the bronchus, removing a right main bronchus adenoma

Gaensler 1956 Advocated parietal pleurectomy to treat recurrent pneumothoraces

Brantigan 1959 First postulated that force needed to keep airways open is missing in emphysema; partial lung resection would improve patient's

condition by restoring this force

Hardy and

Webb

1963 Transplanted a human lung. The patient survived 17 days.

Jensik 1966 Advocated irradiation before bronchopulmonary sleeve resection for lung cancer

Lower and

Shumway

1980 Explained en-bloc heart-lung transplantation in primates

Reitz 1981 Reported successful human heart-lung transplant

Perelman 1983 Developed and performed limited (less than segmental) pulmonary resection

Swanson et al. 1997 First report of minimally invasive technique for lung volume reduction surgery (LVRS) without cutting visceral pleura, thereby reducing

morbidity/mortality due to air leaks, improving mechanics of breathing, and reducing trauma to patient

Cooper 1997 Described improvement on partial lung resection for severe emphysema first developed by Brantigan in 1959. Both lungs partially

resected at the same time with median sternotomy.

History table compiled by David A. McClusky III and John E. Skandalakis.

References

Brantigan O, Mueller E, Kress MB. A surgical approach to pulmonary emphysema. Ann Rev Respir Dis 1959;80:194-202.

Cooper JD. The history of surgical procedures for emphysema. Ann Thorac Surg 1997;63:312-319.

Deffebach ME, Charan NB, Lakshminarayan S, Butler J. The bronchial circulation: small, but a vital attribute of the lung. Am Rev Respir Dis 1987;135:463-481.

Fell SC, Kirby TJ. Segmental resection. In: Pearson FG, Deslauriers J, Hiebert CA, McKneally MF, Ginsberg RJ, Urschel HC (eds). Thoracic Surgery. New York: Churchill

Livingstone, 1995, pp. 854-855.

Grover FL, Fullerton DA, Zamora MR, Mills C, Ackerman B, Badesch D, Brown JM, Campbell DN, Chetham P, Dhaliwal A, Diercks M, Kinnard T, Niejadlik K, Ochs M. The

past, present, and future of lung transplantation. Am J Surg 1997;173:523-533.

Martini N, Ginsberg RJ. Lobectomy. In: Pearson FG, Deslauriers J, Hiebert CA, McKneally MF, Ginsberg RJ, Urschel HC (eds). Thoracic Surgery. New York: Churchill

Livingstone, 1995, pp. 848-849.

Naruke T. Mediastinal lymph node dissection. In: Pearson FG, Deslauriers J, Hiebert CA, McKneally MF, Ginsberg RJ, Urschel HC (eds). Thoracic Surgery. New York:

Churchill Livingstone, 1995, p. 909.

Naef AP. The Story of Thoracic Surgery: Milestones and Pioneers. Toronto: Hogrete and Huber Publishers, 1990.

Naef AP. Early history of thoracic surgery. In: Shields TW (ed). General Thoracic Surgery. Baltimore: Williams and Wilkins, 1972, pp. 1-9.

Naef AP. Pioneers on the road to thoracic surgery. J Thorac Cardiovasc Surg 1991;101:377-384.

Swanson SJ, Mentzer SJ, DeCamp MM Jr, Bueno R, Richards WG, Ingenito EP, Reilly JJ, Sugarbaker DJ. No-cut thorascopic lung plication: a new technique for lung

volume reduction surgery. JACS 1997;185:25-32.



Tsuchiya R. Bronchoplastic bronchovascular techniques. In: Pearson FG, Deslauriers J, Hiebert CA, McKneally MF, Ginsberg RJ, Urschel HC (eds). Thoracic Surgery. New

York: Churchill Livingstone, 1995, p. 870.

Warren R. Surgery. Philadelphia: W.B. Saunders Company, 1963, pp. 598-599.

Waters PF. Pneumonectomy. In: Pearson FG, Deslauriers J, Hiebert CA, McKneally MF, Ginsberg RJ, Urschel HC (eds). Thoracic Surgery. New York: Churchill

Livingstone, 1995, p. 844.

EMBRYOGENESIS

Normal Development

During the fourth week of development, the primordium of the lower respiratory system appears to start with an opening at the ventral pharyngeal wall of

the foregut. This opening is the laryngotracheal groove. The laryngotracheal groove will later produce an outgrowth, the respiratory diverticulum, which will

in turn produce the respiratory epithelium.

The respiratory diverticulum grows, carrying with it the mesenchyme. It finally separates from the pharynx (which represents the cranial part of the

foregut) by the two esophagotracheal ridges. These ridges unite and form the esophagotracheal septum. The esophagotracheal septum divides the foregut

into an anterior (ventral) part (the laryngotracheal tube) and a posterior (dorsal) part (the esophagus) (Fig. 6-1). The mesenchyme produces connective

tissue, muscle, and cartilage for the larynx, trachea, and lungs.

Fig. 6-1.

Division of the foregut into trachea and esophagus. Stippled area shows the future tracheal portion. Arrows indicate the local morphogenetic movements. (Modified

from Skandalakis JE, Gray SW. Embryology for Surgeons, 2nd ed. Baltimore: Williams & Wilkins, 1994; with permission.)

Remember



The respiratory primordium continues to communicate with the pharynx through its opening, which will become the laryngeal orifice or the inlet of the larynx.

Therefore, the proximal end of the diverticulum will produce the larynx.

The epithelium and glands of the trachea and lungs are of endodermal origin. Cartilages and muscles of the trachea are of splanchnic mesenchymal origin.

Prenatal Lung

During the fourth and fifth weeks, two asymmetrical phenomena occur. First, 26 days after fertilization,2 the tracheal end of the diverticulum, which is still

the respiratory diverticulum, produces the two lung buds (Fig. 6-2). The bronchial buds enlarge to form the primordia of the right and left bronchi. The

former has a caudal pathway and the latter an oblique one.

Fig. 6-2.

Development of trachea and bronchi. A, Four anterior views and lateral view of lung buds at the end of the fifth week (horizon XIII). B, Lateral view at the middle

of the sixth week (horizon XV). C, Lateral view near the end of the sixth week (horizon XVI). (Modified from Streeter GL. Developmental horizons in human

embryos: description of age group XIII, embryos about 4 or 5 mm long, and age group XIV, period of indentation of the lens vesicle. Contrib Embryol Carnegie Inst

Wash 1945;31:27-63; Streeter GL. Developmental horizons in human embryos: description of age groups XV, XVI, XVII, and XVIII. Contrib Embryol Carnegie Inst

Wash 1948;32:133-204; with permission.)

The second asymmetrical phenomenon is the production during the 5th week of two lateral buds on the right bronchus and only one on the left. The

bronchial tree subdivides within the lung bud to form several blind ends (the so-called infundibula).

GENESIS OF THE LOBES

The genesis of the lobes takes place as follows:

On the right



On the right

the upper lateral bud produces the lateral bronchus and upper lobe

the lower lateral bronchus produces the middle lobe

the stem (lowest) bronchus produces the lower bronchus and lower lobe

On the left

the (single) lateral bronchus produces the upper left bronchus and lobe

the original left stem bronchus produces the left lower bronchus and lobe

Lobe segmentation (bronchopulmonary segments) continues until there are 10 segments on the right and 8 on the left (Fig. 6-3). The pulmonary formation

ceases around the end of the 5th week.3

Fig. 6-3.

Development of trachea and bronchi. Anterior and lateral views at the beginning of the seventh week (horizon XVII). The trachea and esophagus have elongated,

and five orders of bronchial branching are visible. (Modified from Streeter GL. Developmental horizons in human embryos: description of age groups XV, XVI, XVII,

and XVIII. Contrib Embryol Carnegie Inst Wash 1948;32:133-204; with permission.)

At this time, three antenatal periods or phases of ramification of the pulmonary systems commence sequentially. These are: glandular or pseudoglandular,

canalicular, and alveolar or terminal sac.

GLANDULAR OR PSEUDOGLANDULAR PHASE

This phase starts at the end of the 5th week and perhaps ends around the 16th week. This phase was named glandular or pseudoglandular because



clusters of solid epithelial cuboidal cells surrounding each infundibulum of the bronchial tree give the pulmonary parenchyma the histologic appearance of an

exocrine gland. Gas exchange is not possible; therefore, the fetus born at this phase cannot survive.

CANALICULAR PHASE

This period starts around the 16th week and ends around the 25th week. The respiratory apparatus of the lungs is formed during this period by ramification

of blood vessels around the infundibula as well as around the primordia of pulmonary alveoli. The pulmonary tissues become very vascular, and the multiple

bronchioles have enlarged laminae. Respiration at the 24th to 25th week is possible and the born fetus may be able to survive.

ALVEOLAR OR TERMINAL SAC PHASE

This period extends from the 24th to 26th week until birth. At its commencement, terminal sac (alveolar) formation overlaps the end of the previous period.

The development of terminal sacs multiplies during the terminal sac phase. The epithelium of the sacs becomes thin and flat.

This phase is associated with a rich vascular proliferation of blood capillaries and lymph capillaries. These are the alveolar epithelial cells (type I

pneumocytes). They will later become secretory epithelial cells (type II pneumocytes) and produce surfactant. Surfactant lines the terminal sacs in a

coatlike formation, lowering surface tension and preventing collapse during expiration of the alveoli.

The premature infant will survive only if adequate pulmonary vasculature and surfactant are present. A premature seven-month fetus may survive because

the respiratory system at this time has good function, the lungs have some secretory function, and the surfactant promotes maturity of the antenatal

lungs.

Postnatal Lung

During the first week, air inflates all the alveoli. Blood and lymphatic capillaries absorb the fluid occupying 50% of the lung. From the sixth through the

eighth week, there is rapid development of alveoli. Cormack4 stated that 95% of alveoli develop after birth.

NOTE: More alveoli are formed during the first postnatal years. The pulmonary alveoli of the newborn are said to be 20 million; the number in adults is

approximately 300 million.

Three Embryoanatomic Pulmonary Asymmetric Curiosities

It has been said that:

The right primary bronchus has a caudal pathway and the left bronchus an oblique one. Thus, a foreign body within the trachea will most often travel downward

into the right bronchus.

The embryonic right primary bronchus develops two primary buds, the upper for the upper lobe and the lower for the middle lobe. The blind end of the primary

bronchus then forms the right lower lobe. The left primary bronchus produces only one primary bud which forms the left upper lobe. The left lower lobe is produced

by the blind end of the primary left bronchus.

Typically 10 segmental bronchi form on the right lung and 8 form on the left.

Congenital Anomalies

Congenital anomalies of the trachea and lungs are shown in Table 6-2 and Fig. 6-4.

Table 6-2. Congenital Anomalies of the Trachea and Lungs

Anomaly Prenatal Age

at Onset

First Appearance (or Other

Diagnostic Clues)

Sex Chiefly

Affected

Relative

Frequency

Remarks

Tracheal atresia Week 3-4 At birth ? Very rare Fatal at birth

Congenital tracheal stenosis Week 3-4 At birth ? Rare Usually fatal soon after birth

Tracheobronchomegaly Mo 5 Late childhood or later ? Rare

Bilateral agenesis of the lungs Week 4 At birth ? Very rare Fatal at birth

Unilateral agenesis and

hypoplasia of the lungs

Late week 4 Infancy and childhood Female Uncommon 50% die in first 5 yrs

Anomalies of lobulation Week 10 None Male ? Common Asymptomatic

Pulmonary isomerism Unknown None ? Uncommon Associated with heterotaxy, asplenia and

anomalous pulmonary veins

Congenital cysts of the

respiratory tract:

Bronchgenic cysts Week 6-7 Infancy, if at all ? Uncommon Compression of trachea may be fatal

Pulmonary cysts Week 24 Infancy and childhood Male Uncommon Eventually fatal if untreated

Source: Skandalakis JE, Gray SW. Embryology for Surgeons, 2nd Ed. Baltimore: Williams & Wilkins, 1994.

Fig. 6-4.



Congenital anomalies of the trachea and lungs. (Modified from Skandalakis JE, Gray SW. Embryology for Surgeons, 2nd ed. Baltimore: Williams & Wilkins, 1994; with

permission.)

Accessory Lobes

According to Shields,5 the common accessory lobes are the posterior accessory, inferior accessory, middle lobe of the left lung, and "azygos lobe" of the

upper right lobe (Figs. 6-5, 6-6).

Fig. 6-5.



Accessory lobes of the lungs.

Fig. 6-6.

Azygos lobe. a, Posterior thoracic structures, seen in anterolateral view; showing the azygos vein, the associated great vessels, and (at *) the transverse

connection between the azygos and hemiazygos veins. b, Contents of the right pleural cavity; upper pulmonary lobe is retracted to expose the accessory lobe and

the anomalous azygos vein. Inset: The anomalous azygos vein with part of its reflection of the parietal pleura. c, Transverse section through the right lung and

related structures at the level of the loop of the anomalous azygos vein. d to f, Upper portion of the right lung, showing the pulmonary relations of the anomalous

azygos vein and its connections; three aspects. Incidence of anomalous lobe, in the author's65 laboratory, 0.4 percent (8 cases in 2,000 specimens). R.i.v., right

innominate vein (NA, brachiocephalic); L.i.v., left innominate vein; I.j.v., internal jugular vein; A.j.v., anterior jugular vein; S.v., subclavian vein; S.v.c., superior vena



innominate vein (NA, brachiocephalic); L.i.v., left innominate vein; I.j.v., internal jugular vein; A.j.v., anterior jugular vein; S.v., subclavian vein; S.v.c., superior vena

cava; M.s., mediastinal surface; V.c.s., vertebrocostal surface. (Modified from Anson BJ. An Atlas of Human Anatomy, 2nd Ed. Philadelphia: WB Saunders, 1963; with

permission.)

There is confusion in the literature about the terminology for these "accessory lobes." The posterior, inferior and middle lobe of the left lung are true

accessory lobes. In reality, the azygos lobe is not an accessory lobe; it is a partial separation of a portion of the apical segment of the right upper lobe by

the azygos venous arch.

The azygos lobe varies in size and extent. It is formed by a deep indentation from an aberrant tributary of the azygos vein and its mesoazygos component

in the region of the apical and posterior segments of the right upper lobe.

Matawari et al.6 studied the segmental and vascular anatomy of the posterior pulmonary lobe. We quote from their excellent work:

The posterior pulmonary lobe (PPL) is defined by an aberrant fissure running horizontally on the costal surface of the lower lobe...Nineteen PPL cases

(15 right and 4 left) were found in 273 (116 right and 157 left) human lung specimens. The incidence of PPL was 13% on the right side and 3% on

the left side. The PPL frequently (right 87%, left 50%) corresponded to S(6) (superior segment). Analysis of the ramification of bronchi revealed that

B(7) (medial basal bronchus) tended to form a common trunk with B* (subsuperior bronchus) or B(8) (anterior basal bronchus). Analysis of the

ramification of veins revealed that V(6) (superior vein) tributaries were often double, and V(6) tended to disperse widely. Anomalies in which the

segmental artery and vein communicated with other segments were found in seven cases (37%) (4 arteries and 3 veins, 6 right and 1 left) in PPL.

These results show that the PPL does not always correspond to S(6) and frequently has an anomalous vessel from other segments.

Unilateral Agenesis, Aplasia, and Hypoplasia of the Lung

Raffensperger7 provided pragmatic definitions of pulmonary unilateral agenesis (complete absence of bronchus, parenchyma, and vessels) and pulmonary

hypoplasia (various degrees of underdevelopment).

Schechter8 classified congenital deficiency of lung tissue as follows:

Class I bronchopneumonic aplasia (Fig. 6-7B)

Unilateral or bilateral absence of the entire lung and bronchial tree, called "agenesis of the lung" in earlier classifications

Class II bronchopneumonic dysplasia (Fig. 6-7C, D)

Interrupted formation of the bronchial tree with absence of alveoli, called "aplasia of the lung" in earlier classifications

Class III bronchopneumonic hypoplasia (Fig. 6-8A, B, C)

Entire lung is reduced in size or one lobe of lung is absent

Class IV bronchopneumonic ectoplasia (Fig. 6-8D, E, F)

Displacement of part or all of a lung has occurred, with bronchoesophageal fistula present

Fig. 6-7.

A. Normal lungs. B. Pulmonary aplasia, with complete absence of both bronchial and alveolar tissue. C and D, Pulmonary dysplasia. Some bronchial elements are

present, but there are no alveoli. Enlargement of the sound lung and the resulting displacement of the heart and mediastinum are not shown. (Modified from

Schechter DC. Congenital absence or deficiency of lung tissue: the congenital subtractive bronchopneumonic malformations. Ann Thorac Surg 1968;6:286-313; with

permission.)

Fig. 6-8.



A to C. Pulmonary hypoplasia. Three conditions of different embryogenesis that all result in a smaller than normal lung. A, Alveolar tissue not functional. B, Reduced

size of one lung. C, Hypoplasia resulting from lobar dysplasia. The accompanying mediastinal shift is not shown. D to F. Pulmonary ectoplasia. Part or all of one

lung is attached to the esophagus and usually is supplied by a systemic artery. D, Bronchoesophageal fistula. E, Sequestration of right lower lobe. F,

Sequestration of lower lobe and dysplasia of upper lobe. (Modified from Schecter DC. Congenital absence or deficiency of lung tissue: the congenital subtractive

bronchopneumonic malformations. Ann Thorac Surg 1968;6: 286-313; with permission.)

Peragallo and Swenson9 studied congenital tracheal bronchus:

Tracheal bronchus is a congenital anomaly in which the right upper lobe bronchus originates from the lateral tracheal wall. This anatomic variant is

reported in approximately 1 of 250 patients at bronchoscopy. Although it is usually of little clinical significance, this atypical origin of the right upper

lobe bronchus may complicate one-lung ventilation during thoracic surgery.

Roque et al.10 presented a case of unilateral right pulmonary agenesis without mediastinal displacement. There was cervical ascent of the liver and right

hemidiaphragm.

We quote from Evrard et al.11 about congenital parenchymatous malformations:

[A]ny thoracic cystic lesion expanding on chest radiography should be an indication for surgical resection, even if asymptomatic, because of the risk

of pulmonary compression, infection, or malignant degeneration. In the few cases of a fetal intrathoracic mass, prenatal diagnosis and intrauterine

intervention may be indicated. . .

Congenital pulmonary venous obstruction causes pulmonary hypertension which, according to Endo et al.,12 seems to be reversible and amenable to

operation.

For details of congenital anomalies of the respiratory system, the interested student is encouraged to read Embryology for Surgeons.13

SURGICAL ANATOMY

Trachea

From a surgicoanatomic viewpoint, the trachea can be divided into two parts: upper (or cervical) and lower (or thoracic), including the tracheal bifurcation.

The length of the trachea in the supine position is 10 to 13 cm from the laryngotracheal junction at C6 (cricoid cartilage) to T4 where the bifurcation is

located. In upright posture, the trachea is located between C6 and T6 (Fig. 6-9). According to Kubik and Healey,14 the tracheal length may increase by

approximately 1.5-2.5 cm during the processes of swallowing or respiration.

Fig. 6-9.



Origin of the trachea at the level of the sixth cervical vertebra. (Modified from Brantigan OC. Clinical Anatomy. New York: McGraw-Hill, 1963; with permission.)

Mulliken and Grillo15 stated that the trachea can be located totally within the mediastinum when the neck is flexed, because the cricoid cartilage drops to

the level of the thoracic inlet.

The position of the trachea is not fixed; it can deviate to the right or left because it is ensheathed within a stroma of loose connective tissue that also is

related to the esophagus. The trachea has 15 to 20 U-shaped rings of hyaline cartilage that are responsible for the lateral rigidity of the organ. The rings

are united by a thin elastic membrane. Posteriorly, the cartilages are united by the thin tracheal smooth muscle (the trachealis).

Topography and Relations

CERVICAL TRACHEA

According to Kubik and Healey,14 the cervical trachea at its origin is located 1.5-2 cm below the skin. The sternal notch is 4.5-5.0 cm beneath the skin,

and at the bifurcation the depth is at approximately 7 cm.

The following is a summary of the topographic relations of the cervical trachea (Fig. 6-10).

Fig. 6-10.



Cross section of the neck showing fascial layers. D, the "danger space" within the prevertebral fascia. RV, retrovisceral or retropharyngeal space between the

prevertebral fascia and the pretracheal (visceral) facial layers. (Modified from Colborn GL, Skandalakis JE. Clinical Gross Anatomy. New York: Parthenon, 1993; with

permission.)

Anterior

Skin

Subcutaneous fascia with platysma

Investing layer of deep cervical fascia

Sternohyoid and sternothyroid muscles

Pretracheal fascia

Inferior thyroid and thyroid ima veins. Occasionally the thyroid ima artery is located just below the isthmus; these vessels and the isthmus are covered with a thin

connective tissue stroma.

The thyroid isthmus is in front of the 2nd, 3rd, and 4th tracheal cartilages.

Lateral

Skin, superficial fascia, and platysma

Sternocleidomastoid muscle and cervical investing fascia

Carotid sheath with common carotid artery, internal jugular vein, and vagus nerve

Omohyoid, sternohyoid, sternothyroid muscles

Middle thyroid vein

Thyroid lobe

Inferior thyroid artery and recurrent laryngeal nerve

Paratracheal lymph nodes

Posterior

Thin areolar tissue

Esophagus

Prevertebral ("danger") space of the neck

Vertebral column and musculature

THORACIC TRACHEA

The thoracic trachea is the deepest anatomic entity of the superior mediastinum. The topographic relations of the thoracic part of the trachea follow.

Anterior

Skin, superficial fascia, manubrium of sternum

Thymus and thymic fat, thymic vessels (Fig. 6-11)

Left brachiocephalic vein

Brachiocephalic artery and left common carotid artery, aortic arch

Cardiac plexus (Fig. 6-12)

Fig. 6-11.



The thymic vessels.

Fig. 6-12.

The lower end of the trachea, showing the deep cardiac plexus.

Lateral

On the right: right vagus nerve, paratracheal lymph nodes, mediastinal pleura, azygos venous arch (Figs. 6-12, 6-13)

On the left: paratracheal nodes, left recurrent laryngeal nerve, left common carotid artery

Fig. 6-13.



Right vagus nerve.

Posterior

Esophagus

TRACHEAL BIFURCATION

At the level of the sternal angle anteriorly and the fifth thoracic vertebra posteriorly, just above the left atrium, the trachea bifurcates into the right and

left primary bronchi. The topography and relations of tracheal bifurcation are:

Anterior

Superior and inferior tracheobronchial lymph nodes, right pulmonary artery

Posterior

Pulmonary plexus, bronchial arteries

The carina is an inside ridge at the bifurcation of the trachea at the level of the last tracheal cartilage. Schuster et al.16 proposed the carina as a landmark

for central venous catheter placement:

Location of the tip of a central venous catheter within the pericardium has been associated with potentially lethal cardiac tamponade. Because the

pericardium cannot be seen on chest x-ray, an alternative radiographic marker is needed for correct placement of central venous catheters...The

carina was a mean distance of 0.4 (0.1) cm above the pericardial sac as it transverses the superior vena cava. In no case was the carina located

below the pericardial sac. The carina is a reliable, simple anatomical landmark for the correct placement of central venous catheters. In almost all

cases, the carina is radiologically visible even in poor quality, portable chest x-rays. Central venous catheter tips should be located in the superior

vena cava above the level of the carina in order to avoid cardiac tamponade.

Vascular Supply



Vascular Supply

ARTERIES

The arterial supply of the trachea is from the inferior thyroid arteries and from branches originating from the superior thyroid arteries, bronchial arteries, and

internal thoracic arteries.

VEINS

The inferior thyroid veins drain the trachea, emptying into one or both brachiocephalic veins.

LYMPHATICS

The tracheal lymphatic vessels drain into the cervical, tracheal, and tracheobronchial lymph nodes.

Innervation

Sympathetic fibers from the cardiac branches of the cervical sympathetic trunk and thoracic visceral nerves convey postganglionic fibers to the tracheal

muscle for bronchodilatation. Parasympathetic fibers arise from the vagus nerves and the recurrent laryngeal nerves and pass to the mucosa and tracheal

muscle. These fibers are bronchoconstrictive. Many small clusters of ganglionic cells are present in the autonomic plexuses of the walls of the trachea and

bronchi.

Bronchi

(Fig. 6-14) Each primary bronchus extends from the tracheal bifurcation to the hilum of the related lung. The shorter and larger (2.5 cm) right bronchus

turns only slightly from the vertical orientation of the trachea through the mediastinum. The length of the left primary bronchus, almost double that of the

right primary bronchus, passes more obliquely laterally to the left. The left bronchus crosses anterior to the esophagus to reach the left hilum behind the

left third costal cartilage. Both bronchi have mobility and elasticity comparable to that of the trachea, although the irregularity of the cartilaginous plates

increases distally. The plates of cartilage decrease in prominence within the lungs, disappearing at the level of the bronchioles.

Fig. 6-14.

The primary bronchi (A) and some of their anterior vascular relations (B and C). The reflection of the pericardial sac upon the great vessels is shown in C.



We agree with the anatomic observations of Ashour et al.17:

[The] left lung is more vulnerable to bronchiectasis than the right, a clinical observation that could be explained on the basis of the anatomic

peculiarities of the left main bronchus. The latter, when compared to the right bronchus, has a longer mediastinal course, a narrower diameter, and

limited peribronchial space as it passes through the subaortic tunnel (Fig. 6-15) . . .the left lung, when compared to the right, is more vulnerable to

the bronchiectatic process both in frequency and severity. Anatomic features of the left main bronchus make it more prone to obstruction than the

right.

Fig. 6-15.

Anatomy of the left main bronchus as it passes through the subaortic tunnel. (Modified from Ashour M, Al-Kattan K, Rafay MA, Saja KF, Hajjar W,

Al-Fraye AR. Current surgical therapy for bronchiectasis. World J Surg 1999;23: 1096-1104; with permission.)

According to Trotter et al.,18 torsion of the lung in toto or torsion of a lobe may be spontaneous or occur after trauma. Felson19 stated that the following

anatomic conditions may be responsible for this rare and peculiar pathological occurrence:

Abnormal length of the primary or lobar bronchus with free pedicle

A complete fissure

Absence of the inferior pulmonary ligament

Topographic Relations

The topographic relations of the bronchi follow.

RIGHT PRIMARY BRONCHUS

Anterior

Right pulmonary artery, ascending aorta, superior vena cava (SVC)

Posterior

The azygos arch curves over the bronchus and drains into the SVC

The right vagus nerve passes between the azygos arch and the proximal part of the bronchus, giving origin to its pulmonary branch to the right lung

LEFT PRIMARY BRONCHUS

Anterior

The aortic arch, main pulmonary artery, left pulmonary artery and vein

NOTE: The pulmonary artery is located between the left upper lobe bronchus and the left primary bronchus.

Posterior

Descending aorta, esophagus, and pulmonary plexus



The left vagus nerve crosses behind the left bronchus, providing a pulmonary branch that passes to the left lung

Vascular Supply

The bronchial circulation is like Mother or the Red Cross: normally accepted and unsung, but capable of giving vital help when needed.Deffebach

et al.20

The bronchial blood supply has been studied in detail by Cauldwell et al.,21 Olson and Athanasoulis,22 Deffebach et al.,20 Miller and Nelems,23 and several

other investigators. The origins of the bronchial arteries and the pattern of bronchial venous drainage are both highly variable.

ARTERIES

(Fig. 6-16, Table 6-3) The origin of the right and left bronchial arteries is very variable. They may arise from the internal thoracic artery, subclavian artery,

or inferior thyroid arteries. In most cases the single right bronchial artery arises from the aorta or the third right posterior intercostal artery. The left lung is

nourished by two bronchial arteries that arise directly from the beginning of the descending thoracic aorta. Variations in origin of bronchial arteries are

shown in Figs. 6-17A & B.

Table 6-3. Origins and Number of Bronchial Arteries in 150 Dissected Autopsy Specimens

Anatomic Variation Number of Right Bronchial Arteries Number of Left Bronchial Arteries Percent Incidence

I 1 2 40.8

II 1 1 21.3

III 2 2 20.8

IV 2 1 9.7

V 1 3 4.0

VI 2 3 2.0

VII 3 2 0.6

VIII 1 4 0.6

IX 4* 1 0.6

*A branch from the left bronchial artery anterior to the esophagus passing to the right bronchus plus two right bronchial arteries from the aorta and one right

bronchial artery from the subclavian artery.

Source: Caudwell EW, Siekert RG, Lininger RE, Anson BJ. The bronchial arteries: an anatomic study of 150 human cadavers. Surg Gynecol Obstet 1948;86:395-412;

with permission.

Fig. 6-16.



The four most common sites of origin and numbers of bronchial arteries to the right and left lungs. See Table 6-3 for percentage of occurrence of each. (Modified

from Cauldwell EW, Siekert RG, Lininger RE, Anson BJ. The bronchial arteries: an anatomic study of 150 human cadavers. Surg Gynecol Obstet 1948;86:395-412;

with permission.)

Fig. 6-17.



Variations in origin of bronchial and esophageal arteries. A, left view. B, right view.

According to Deffebach et al.,20 the systemic bronchial arterial blood network "appears to be quite unimportant" at first, since its abolition is possible during

lung transplantation (Fig. 6-18). Their excellent article explores the "small, but vital" role of bronchial circulation in health and disease.

Fig. 6-18.

Schematic of the systemic blood supply to the lung. Note that the flow from the extrapulmonary airways and supporting structures returns to the right heart,

whereas intrapulmonary flow becomes anastomotic with the pulmonary circulation and returns to the left heart. (Modified from Deffebach ME, Charan NB,

Lakshminarayan S, Butler J. The bronchial circulation: small, but a vital attribute of the lung. Am Rev Respir Dis 1987;135:463-481; with permission.)

After Carles et al.24 dissected 40 fresh cadavers, they reported that the bronchial blood supply is dominated by the intercostobronchial trunk and

anastomotic networks of different territories of the bronchial tree. Their findings on the feasibility of bronchial artery revascularization may be applicable to

pulmonary transplantation.

VEINS

The right bronchial veins (usually two) drain to the terminal part of the azygos vein, and the left bronchial veins end in the left superior intercostal vein or

the accessory hemiazygos vein (Figs. 6-19, 6-20).

Fig. 6-19.



Right bronchial veins.

Fig. 6-20.



The main veins of the thorax. A dashed line indicates the course of a left superior vena cava (a rare anomaly) on its way to the coronary sinus. (Modified from

O'Rahilly RO. Gardner-Gray-O'Rahilly Anatomy: A Regional Study of Human Structure, 5th Ed. Philadelphia: WB Saunders, 1986; with permission.)

LYMPHATICS

Lymphatic vessels from the bronchi pass to the bronchopulmonary and tracheobronchial lymph nodes (Fig. 6-21).

Fig. 6-21.

Pulmonary lymphatics: overall view of regional drainage. (Modified from Rouvire H. Anatomie des Lymphatiques de l'Homme. Paris: Masson, 1932; with

permission.)

Innervation

Sympathetic and parasympathetic innervation occurs through the pulmonary and cardiac plexuses. The bronchi are relatively insensitive to pain, and

stimulation of their mucosal lining produces coughing.

Lungs

Topography and Relations

The lungs are movable organs within the thoracic cavity; however, both are anchored to the heart and trachea. The right lung is composed of three lobes

and the left lung of two lobes.

Both the liver and heart modify the external contour of each lung. The right lung is shorter because of the right hepatic lobe; the left lung is narrower

because of the leftward location of the heart and pericardium. Each lung accepts the bronchi as well as the pulmonary vessels.

Both lungs exhibit the following characteristics: apex, base, three surfaces, three borders, and fissures (Figs. 6-22A & B).

Fig. 6-22.



Projections of thoracic viscera. A, anterior view of male. B, posterior view of male. (Modified from Frick H, Kummer B, Putz R. Wolf-Heidegger's Atlas of Human

Anatomy (4th ed). Basel: Karger, 1990; with permission.)

APEX

The apex is covered by pleura. It projects above the clavicle into the base (root) of the neck. The extent of the lung above the clavicle varies with

respiration, posture, body build, and the angle of view. The apex of the left lung is a little longer than that of the right.

The relations of the apex are as follows:

Anterior: subclavian artery, anterior scalene muscle, subclavian vein, phrenic nerve, vagus nerve

Posterior: sympathetic trunk, 1st thoracic nerve, superior intercostal artery

Medial: brachiocephalic trunk, right brachiocephalic vein, trachea on the right, left subclavian artery and left brachiocephalic vein on the left

Lateral: scalenus medius muscle, first rib

BASE

The base is related to the superior surface of the diaphragm and several subdiaphragmatic organs. The right lower lobe is related to the pleura, diaphragm,

peritoneum, and right lobe of the liver. The left lower lobe is related to the pleura, diaphragm, peritoneum, left lobe of the liver, gastric fundus, and spleen.

THREE PULMONARY SURFACES

The costal surface of each lung is related to the thoracic wall. It ends at the anterior, posterior, and inferior pulmonary borders.

The medial or mediastinal surface of the lung is in contact with the organs of the mediastinum (Fig. 6-23). The posterior part of the medial surface is

related to the spine. Its medial mediastinal part is related to the superior, middle, and posterior mediastinum. The hilum (pulmonary porta) is the most

important anatomic area for the entrance and exit of bronchi, vessels, and nerves.

Fig. 6-23.



Relationships between the lungs and organs of the mediastinum. Sup.v., superior pulmonary vein; Inf. v., inferior pulmonary vein. (From Healey JE Jr, Hodge J.

Surgical Anatomy (2nd ed). Philadelphia: BC Decker, 1990; with permission.)

The right diaphragmatic surface is related to the right hemidiaphragm and right lobe of the liver. The left diaphragmatic surface is related to the gastric

fundus, the spleen, and occasionally to the splenic flexure of the colon and the left lobe of the liver.

Frija et al.25 reported the radiologic anatomy of the inferior lung margin using computed radiography:

The right posterior inferior lung margin (ILM) was always visible and usually concave upward (94%). Its height was 8.7 1.6 cm. Its most inferior

part faced L1 or L2 in 92% of cases. It was continuous medially inside with the azygo-esophageal recess in 96% of cases. The left posterior ILM was

not visible laterally in 34% of cases and medially in 60% of cases. It was most often concave upward (82% of cases). Its height was 6.9 1.5 cm.

Its most inferior part was at the level of L1 or L2. It was continuous medially with either the left paraspinal line or the paraaortic line. The right

anterior ILM was visible in 76% of cases. It was most often oblique upward and medially (46%) or concave upward (33%) and often notched (38%).

The left anterior ILM was visible in 64% of cases and more often oblique inward and upward (58%). It was continuous medially with the left inferior

precardiac recess. The anterior ILMs were more variable than the posterior. The posterior ILMs were very similar in shape and inferior level and

differed in depth only by the difference of height of the diaphragmatic cupolas.

THREE PULMONARY BORDERS

The three pulmonary borders (anterior, inferior, posterior) correspond to the lines of pleural reflection (Figs. 6-24, 6-25).

Fig. 6-24.



Borders of the pleurae and lungs in anterior and posterior views. (Modified from McVay CB. Anson & McVay Surgical Anatomy (6th ed). Philadelphia: WB Saunders,

1984; with permission.)

Fig. 6-25.

Borders of the pleurae and lungs in lateral views. (Modified from McVay CB. Anson & McVay Surgical Anatomy (6th ed). Philadelphia: WB Saunders, 1984; with

permission.)

Both right and left borders are atypical and not always constant. Deep or shallow respiration changes the topography. The surgeon should always remember

the upward cervical projection of the lung and its downward projection and relations (costodiaphragmatic recess) to organs within the peritoneal cavity,

such as the liver on the right and the spleen on the left.

FISSURES

(Fig. 6-26) The left oblique fissure begins posteriorly at the 4th rib or occasionally at the 3rd or 5th. It ends at the area of the 6th or 7th rib with a

downward and forward pathway, almost reaching the hilum.

Fig. 6-26.



External fissures of the lungs, and the frequency of their occurrences. Absence of a fissure does not imply alteration in the underlying bronchial pattern. The less

common fissures create dorsal and cardiac lobes. (Modified from Skandalakis JE, Gray SW. Embryology for Surgeons (2nd ed). Baltimore: Williams & Wilkins, 1994;

with permission.)

The right oblique fissure begins posteriorly approximately at the level of the 5th rib. With a downward and forward pathway, it ends at the 6th

costochondral junction. The left and right oblique fissures cross the midaxillary line on their respective sides at the level of the 5th or 6th rib.

The horizontal fissure begins at the level of the 6th rib near the midaxillary line where the pathway of the oblique fissure is located. The medial end of the

horizontal fissure is located at the 4th costal cartilage or 4th intercostal space, adjacent to the sternum.

Segmentation of the Lungs

The three lobes of the right lung and the two lobes of the left lung are composed of bronchopulmonary segments. The right lung has 10 segments and the

left lung has 8 segments (Table 6-4, Fig. 6-27). However, some writers count the two terminal branches of the apicoposterior segment separately, and

consider the anteromedial basal segment of the lower lobe as medial basal and anterior basal; thereby giving the left lung also 10 bronchopulmonary

segments. By definition, however, a bronchopulmonary segment is that portion of pulmonary tissue served by a tertiary bronchus.

Table 6-4. Bronchopulmonary Segmental Nomenclature and Numerical Designations

Right Lung Left Lung

Upper lobe

Apical 1 [1] Superior division

Anterior 2 [3] Apicoposterior 1 + 3 [1 + 2]

Posterior 3 [2] Anterior 2 [3]

Inferior divisionlingula

Superior lingular 4 [4]

Inferior lingular 5 [5]

Middle lobe

Lateral 4 [4]

Medial 5 [5]

Lower lobe

Superior 6 [6] Superior 6 [6]

Medial basal [cardiac] 7 [7] Anteromedial [Medial basal-cardiac] [7 + 8]

Anterior basal 8 [8] [Anterior basal] [8]

Lateral basal 9 [9] Lateral basal 9 [9]

Posterior basal 10 [10] Posterior basal 10 [10]

Note: Terms and numerals in brackets are those of the Nomina Anatomica, 1989.



Note: Terms and numerals in brackets are those of the Nomina Anatomica, 1989.

Source: Shields TW. Surgical anatomy of the lungs. In: Shields TW, LoCicero J III, Ponn RB (eds). General Thoracic Surgery, 5th ed. Philadelphia: Lippincott Williams &

Wilkins, 2000, pp. 63-75; with permission.

Fig. 6-27.

The bronchopulmonary segments. AB, anterior basal; AMB, anteromedial basal; An, anterior segment (of the upper lobe); Ap, apical; ApP, apical-posterior; IL,

inferior lingular; LB, lateral basal; LM, lateral segment of the middle lobe; MB, medial basal; MM, medial segment of the middle lobe; P, posterior segment (of the

upper lobe); PB, posterior basal; S, superior segment of the lower lobe; SL, superior lingular. (Modified from Hollinshead WH. Anatomy for Surgeons. New York:

Hoeber-Harper, 1961; with permission.)

The segments are characterized by the central location of a bronchus and a branch of the pulmonary artery. The pulmonary venous tributaries run between



The segments are characterized by the central location of a bronchus and a branch of the pulmonary artery. The pulmonary venous tributaries run between

segments.

The bronchopulmonary segments of both lungs have specific topographic locations. Their names indicate their positions relative to the thoracic wall and

mediastinum.

RIGHT LUNG

The 3 lobes of the right lung (upper, middle, and lower) are defined by an oblique major fissure separating the lower lobe from the middle lobe, and by a

horizontal minor fissure separating the upper lobe from the middle lobe. The upper lobe of the right lung has three bronchopulmonary segments: apical,

posterior, and anterior. The middle lobe is characterized by two segments, medial and lateral. The lower lobe has a superior segment and 4 basal segments:

anterior basal, medial basal, posterior basal, and lateral basal.

LEFT LUNG

The 2 lobes of the left lung (upper and lower) are separated by the oblique fissure. The distribution of bronchopulmonary segments differs from that of the

right lung. Characteristically, the apical and posterior segments of the upper left lobe form the "apicoposterior segment" of the upper lobe. The medial basal

and anterior basal segments have a common origin from the anteromedial segment of the lower lobe.

The inferior part of the left upper lobe is called the lingula, because of its thin prolongation in front of the left side of the heart. The lingula contains

superior and inferior bronchopulmonary segments which correspond to the anteroinferior position of the lingula. Topographically, the lingula is related to the

left 6th rib and left ventricle. It is the homologue of the right middle lobe.

According to Woniak,26 despite the fact that supernumerary segments are common, the supernumerary bronchi almost never arise from the trachea.

Lung Roots and Hila

The hilum is the area of the mediastinal surface that transmits the bronchi and pulmonary vessels. The lung root consists of a group of structures that

enter and exit the hilum.

The two lungs differ not only in number of lobes and arrangements of segments, but also in topographic relations with surrounding structures. Knowledge of

these differences is essential for the surgeon when approaching the right and left lung hila.

RIGHT LUNG HILUM

Anterior Approach

(Fig. 6-28.1). The most anterior anatomic entity in the hilum is the superior pulmonary vein. It partially covers the right pulmonary artery. Posterior to the

pulmonary artery is the bronchus. The azygos vein and the vagus and phrenic nerves are nearby.

Fig. 6-28.



Approaches to the right lung hilum. 1, Anterior approach. 2, Interlobar approach. 3, Posterior approach. RUL, right upper lobe; RML, right middle lobe; RLL, right

lower lobe. (From Healey JE Jr, Hodge J. Surgical Anatomy (2nd ed). Philadelphia: BC Decker, 1990; with permission.)

Interlobar Approach

(Fig. 6-28.2). The interlobar approach to the right lung hilum is through the oblique fissure. The pulmonary artery and its branches are the most superficial

structures.

Posterior Approach

(Fig. 6-28.3). The inferior pulmonary vein and/or its branches are side by side with the intermediate bronchus. The esophagus, vagus nerve, and azygos

vein are visible.

LEFT LUNG HILUM

Anterior Approach

(Figs. 6-29.1, 6-29.2). The superior pulmonary vein with its three tributaries corresponds to the bronchopulmonary segment of the left upper lobe and the

left pulmonary artery side by side. Close to the vein and a little posterior, the lower lobe bronchus can be seen. One can also observe the aortic arch, the

ligamentum arteriosum, and the left recurrent nerve. With lateral and posterior lung retraction, the vagus and phrenic nerves are visible.

Fig. 6-29.



Approaches to the left lung hilum. 1, Anterior approach. 2, Interlobar approach. 3, Posterior approach. LLL, left lower lobe; LUL, left upper lobe. (From Healey JE Jr,

Hodge J. Surgical Anatomy (2nd ed). Philadelphia: BC Decker, 1990; with permission.)

Interlobar Approach

(Fig. 6-29.2). The left pulmonary artery is the dominant anatomic entity in the interlobar approach to the left lung hilum.

Posterior Approach

(Fig. 6-29.3). The most superficial structures are the inferior pulmonary vein and the left pulmonary artery side by side. The left main bronchus lies anterior

to and between the vein and artery.

Remember

The root of the lung is enveloped by the mediastinal pleura, which inferiorly forms the pulmonary ligament.

The right lung root is located under the azygos venous arch, SVC, and both atria. The phrenic nerve lies posteriorly, and the esophagus and right vagus nerve lie

anteriorly.

The left lung root is located under the aortic arch, with the ligamentum arteriosum fixed to the right. The left vagus nerve and its branch and the left recurrent

laryngeal nerve are also associated with the left lung root. The left atrium and main pulmonary artery are related anteriorly to the left lung hilum; the descending

aorta lies posteriorly and laterally. The esophagus is related more medially to the left lung hilum.

On the left mediastinal surface (the hilum of the left lung) the pulmonary artery lies above the bronchus.

On the right mediastinal surface (the hilum of the right lung) the eparterial bronchus is located above the pulmonary artery.

To be more anatomically correct, the pulmonary artery crosses the bronchus anteriorly on the left, but on the right the pulmonary artery passes laterally to the

bronchus.



The bronchi do not have a connective tissue sheath. The veins are surrounded by a thin, tissue-paperlike sheath. The arteries have a well formed sheath.

Bronchial Trees

RIGHT BRONCHIAL TREE

(Figs. 6-30, 6-31, 6-32) The upper right lobe bronchus has a length of 1-1.5 cm. It originates from the lateral wall of the right main bronchus below the

carina, and gives off 3 segmental bronchi (apical, posterior, and anterior). The genesis of the segmental bronchi is quite variable. It is probable that they

form by trifurcation of the right upper lobe bronchus.

Fig. 6-30.

Right bronchial tree. A, anterior view. B, lateral view. Boyden's modification of numerical nomenclature used. (Modified from Shields TW. Surgical anatomy of the

lungs. In: Shields TW (ed). General Thoracic Surgery (5th ed). Philadelphia: Lippincott Williams & Wilkins, 2000, pp. 63-75; with permission.)

Fig. 6-31.



Tracheal bronchus supplying the apical segment of the right upper lobe. A, Anterior view. B, Lateral view. (Modified from Shields TW. Surgical anatomy of the lungs.

In: Shields TW (ed). General Thoracic Surgery (5th ed). Philadelphia: Lippincott Williams & Wilkins, 2000, pp. 63-75; with permission.)

Fig. 6-32.

Schema of the segmental bronchi of the right lung. A, Anterior view. B, Lateral view. (Modified from Hollinshead WH. Anatomy for Surgeons. New York: Hoeber-

Harper, 1961; with permission.)

The right middle lobe bronchus arises perhaps 1 cm below the orifice of the upper lobe. The lateral and medial segments are formed by bifurcation.

The right lower lobe bronchus is located inferiorly and posteriorly. For all practical purposes, it is the caudal end of the right primary bronchus. It provides

origin for five segmental bronchi (superior, medial basal, anterior basal, lateral basal, and posterior basal).

LEFT BRONCHIAL TREE



(Figs. 6-33, 6-34) The left upper lobe bronchus originates anterolaterally from the main bronchus, approximately 5 cm distal from the carina. It divides into

2 branches: the ascending superior and the descending inferior. The superior division bifurcates into: (1) the apicoposterior and the anterior bronchi, and

(2) the inferior, the well known lingula (Fig. 6-35), which divides into superior and inferior lingular bronchi.

Fig. 6-33.

Left bronchial tree. A, Anterior view. B, Lateral view. Boyden's modification of numerical nomenclature used. (Modified from Shields TW. Surgical anatomy of the

lungs. In: Shields TW (ed). General Thoracic Surgery (5th ed). Philadelphia: Lippincott Williams & Wilkins, 2000, pp. 63-75; with permission.)

Fig. 6-34.



Schema of the segmental bronchi of the left lung. A, Anterior view. B, Lateral view. (Modified from Hollinshead WH. Anatomy for Surgeons. New York: Hoeber-

Harper, 1961; with permission.)

Fig. 6-35.

Typical branchings of the chief bronchi of the left lung, anterior view. For identification of segmental bronchi, see Fig. 6-37. (Modified from Hollinshead WH. Anatomy

for Surgeons. New York: Hoeber-Harper, 1961; with permission.)

The left lower lobe bronchus is the caudal end of the main left bronchus. At approximately 0.5 cm below the orifice of the upper bronchus, it gives origin to

the superior segmental bronchus. The four remaining basal bronchi are formed by bifurcation and trifurcation. There are multiple variations, the most

common being the presence of a combined anteromedial basal segment.

Vascular Supply

The lungs have a dual blood supply: one for the interchange of gases (pulmonary arteries and veins) and the other for nutritional supply of the pulmonary

parenchyma (bronchial arteries and veins [see section on bronchi]).

ARTERIES

(Fig. 6-36)

Fig. 6-36.



Pulmonary arteries, segmental arteries. 1, Right pulmonary artery (mediastinal portion). 2, Pulmonary trunk. 3, Left pulmonary artery (mediastinal portion). 4,

Lingular artery. 5, Interlobar portion of the pulmonary artery. 6, Middle lobe artery. (Modified from Kubik S, Healey JE. Surgical Anatomy of the Thorax. Philadelphia:

WB Saunders, 1970; with permission.)

Pulmonary Trunk

The right and left pulmonary arteries arise from the pulmonary trunk, which in turn arises from the right ventricle. The pulmonary trunk may be considered in

two parts: intrapericardial (3.75 cm long) and extrapericardial (1.25 cm long). The extrapericardial portion lies to the left of the ascending aorta.

The pulmonary trunk bifurcates in the concavity of the aortic arch below the trachea and in front of the left main bronchus. This bifurcation forms the right

pulmonary artery (associated very closely with the ascending aorta) and a short left pulmonary artery (located above the left bronchus).

Right Pulmonary Artery. The right pulmonary artery is longer and larger than the left pulmonary artery (Fig. 6-37A). It is located below the carina and

anterior to the right main bronchus. Its anterior relations are as follows: ascending aorta, SVC, phrenic nerve. At the root, the right bronchus is above and

the pulmonary veins below.

Fig. 6-37.

Common pattern of branching. A, Right pulmonary artery. B, Left pulmonary artery. (Modified from Shields TW. Surgical anatomy of the lungs. In: Shields TW (ed).

General Thoracic Surgery (5th ed). Philadelphia: Lippincott Williams & Wilkins, 2000, pp. 63-75; with permission.)

Left Pulmonary Artery. The left pulmonary artery is attached to the concavity of the aortic arch by the ligamentum arteriosum (Fig. 6-37B). The artery

crosses over the left primary bronchus behind the upper lobe bronchus and it is situated at the dorsolateral area of the bronchial stem, with the superior

lobar and apical veins in front.

VEINS

(Fig. 6-38) The pulmonary veins are highly variable and do not contain valves. There are usually two pulmonary veins in each side, the superior and inferior.

The veins are formed by intersegmental tributaries, and do not follow the bronchi very closely.

Fig. 6-38.



Pulmonary veins, segmental veins. 1, Apical vein. 2, Posterior vein. 3, Anterior vein. 4, Lingular vein. 5, Apical basal vein. 6, Superior basal vein. 7, Inferior basal

vein. 8, Anterior basal vein. 9, Lateral basal vein. 10, Posterior basal vein. 11, Superficial intersegmental vein between segment 7 and segment 10. 12, Left inferior

pulmonary vein. 13, Left superior pulmonary vein. 14, Right superior pulmonary vein. 15, Right inferior pulmonary vein. 16, Middle lobe vein. (Modified from Kubik S,

Healey JE. Surgical Anatomy of the Thorax. Philadelphia: WB Saunders, 1970; with permission.)

Right Pulmonary Veins

The right superior pulmonary vein is located anterior and occasionally inferior to the right pulmonary artery. It is formed by four tributaries which drain the

upper and middle lobes of the right lung, three from the upper and one from the middle. The right inferior pulmonary vein is located inferior and posterior to

the right superior vein.

Left Pulmonary Veins

The left superior pulmonary vein is formed by 3 or 4 branches, which drain the upper lobe in toto. Its location is roughly anterior to the left pulmonary

artery. The left inferior pulmonary vein is formed by two branches and is located inferior and posterior to the superior vein.

LYMPHATICS

(Figs. 6-39, 6-21, and Table 6-5) For all practical purposes, the lymphatics of the lung belong to the greater group of the lymphatics of the thorax. This is

due to their rich intercommunication with each other, as well as their special groups of lymph nodes which also communicate with each other. There are

several classifications, confusing not only to the student but also to the practicing surgeon.

Table 6-5. Distribution of Bronchopulmonary Lymph Nodes

Right Lung Left Lung

Between upper and middle lobe bronchi Angle between left upper and lower lobe bronchi

Below middle lobe bronchus Above upper lobe bronchus

Medial to upper lobe bronchus Medial to left main bronchus

Above upper lobe bronchus Medial to superior segmental bronchus

Junction of oblique and transverse fissure lying on right pulmonary artery Medial to upper lobe bronchus

Medial to superior segmental bronchus Above superior segmental bronchus

Behind upper lobe bronchus Anterior to left main bronchus

Medial to middle lobe bronchus Behind left main bronchus

Between superior segmental bronchus and lower lobe bronchus Medial to lower lobe bronchus

Medial to lower lobe bronchi Behind upper lobe bronchus

Above superior segmental bronchus Lateral to left main bronchus

Between anterior and medial basal bronchi Lateral to lower lobe bronchus

Lateral to lower lobe bronchus Lateral to upper lobe bronchus

Between segmental bronchi of left upper lobe

Between superior segmental bronchus and basal bronchi

Note: Listed in order of decreasing frequency of the number of times lymph nodes identified in each location.

Source: Borrie J. Lung Cancer. Surgery and Survival. New York: Appleton-Century-Crofts, 1965; with permission.

Fig. 6-39.



Highly schematic diagram of the respiratory lymphatic system. 1 and 2 = Superficial groups of lymphatics. 3 and 4 = Deep groups of lymphatics. Rich

communications exist between superficial and deep groups, including hilar, lobar, and bronchopulmonary areas.

The pulmonary lymphatic network can be divided into two groups: superficial and deep. The superficial group is formed by the lymphatics under the visceral

pleura and by those of the interlobar septa. The deep group is formed by lymphatics located around vessels and bronchi. Rich communication between the

two networks takes place in the hilar area.

Remember

Intrapulmonary lymph nodes are rare.

Bronchopulmonary lymph nodes are common.

The hilar lymph nodes are located along the inferior area of the main bronchi or in the vicinity of the right or left pulmonary vessels, close to the reflection of the

visceral pleura.

The lobar lymph nodes are situated at the origin of the lobar bronchi, close to the pulmonary vessels.

The lungs have an extensive formation of lymphatic plexuses with intercommunication, and multiple nodes that communicate with each other.

The pathway of the pulmonary lymphatics from the periphery (visceral pleura) to the hilum and beyond is as follows:

subvisceral pleura

interlobar septa

bronchial vessels

bronchopulmonary lymph nodes

tracheobronchial lymph nodes



paratracheal lymph nodes

mediastinal lymph nodes

bronchomediastinal lymph trunks

thoracic duct

right lymphatic duct

Innervation

The lung is innervated by the sympathetic and parasympathetic systems. Both divisions contribute to form the pulmonary plexuses, which are located at

the root of the lung, anterior and posterior.

SYMPATHETIC

The sympathetic nervous system participates in the formation of the plexuses by postganglionic fibers. These arise from the first 5 thoracic sympathetic

ganglia, and supply blood vessels, glands, and smooth muscles of the bronchi. Their purpose is uncertain; perhaps they inhibit the action of the smooth

muscles.

According to Rosse and Gaddum-Rosse,27 the sympathetic visceral efferents are motor to the bronchial glands and also produce vasoconstriction of

pulmonary blood vessels. The same authors questioned whether such fibers terminate on bronchiolar muscles even though it is well established that

sympathomimetic drugs produce bronchial dilation.

PARASYMPATHETIC (VAGUS NERVE)

The contribution of the vagus nerve to the plexuses is by fibers which synapse upon intrapulmonary ganglion cells and their axons. Glands and the smooth

muscle of the bronchi may or may not be innervated by an antiinhibitory action. Most likely, sensory fibers carried by the vagus nerve affect the pulmonary

vessels. This may cause severe hypotension, and the heart rate changes. These vagal sensory fibers also innervate the bronchial mucosa and are involved

in the cough reflex.

Regarding innervation of the pleura, the parietal pleura is a somatic structure and thus receives generous general somatic sensory innervation via the

intercostal and phrenic nerves. These mediate touch and pain modalities. In some cases when the mediastinal and medial diaphragmatic areas of parietal

pleura are irritated, pain is referred to the root of the neck and over the shoulder region due to the overlap of spinal cord segments serving the phrenic

nerve (C3, C4, C5) and supraclavicular nerves (C3, C4). The visceral pleura's innervation via vagal fibers mediates no pain sensations, but it has been

reported to contribute in complex ways to the function of respiration.

Rosse and Gaddum-Rosse27 also stated that the vagus nerve is motor to bronchial and bronchiolar smooth muscle, and produces bronchoconstriction. Most

likely the vagus nerve does not innervate smooth muscle in the wall of the pulmonary vessels.

HISTOLOGY AND PHYSIOLOGY

The histologic features of the trachea and bronchi are practically the same. The four layers from the inside to the outside are:

1a. Mucous membrane with ciliated pseudostratified columnar epithelium

1b. Lamina propria

2. Submucosa with mixed seromucous glands

3. Cartilaginous smooth layer. Characteristically, this layer is formed by hyaline cartilage of incomplete rings, united by smooth muscle and some fibrous elements.

4. Adventitia

The physiology of the respiratory system concerns the transport and exchange of oxygen and carbon dioxide. It is not within the scope of this book to

discuss respiratory mechanisms, ventilation with transport and exchange, or pulmonary blood flow. But a very brief description of the physiology of the

trachea and bronchi, together with respiratory physiology, follows.

The formation of air flow depends upon the synergistic action of atmospheric, alveolar, and intrapleural pressures.

The following anatomic entities are related to the pressures

Atmospheric (nose and mouth)

Alveolar (alveolar ducts and alveoli)

When atmospheric pressure is higher than the alveolar pressure, air (containing oxygen) enters the lungs.

When atmospheric pressure is lower than the alveolar pressure, air (containing carbon dioxide) exits the lungs.

Intrapleural (thoracic cavity)

By its own intrapleural pressure, the thoracic cavity negotiates both atmospheric and alveolar pressure.

The inspiratory muscles are the



Diaphragm (the most effective muscle of inspiration)

External intercostals

Sternocleidomastoid muscles

Scalenes

Serratus posterior muscles (superior and inferior)

The diaphragm and external intercostal muscles are innervated by the phrenic and intercostal nerves, respectively. The sternocleidomastoid muscles and scalenes

(the upper airway muscles) are innervated by the cervical nerves.

The expiratory muscles are the

Three flat muscles (external oblique, internal oblique, transversus abdominis)

Rectus abdominis

Internal intercostals

The entire right ventricular output enters the lungs. The low-pressure, low-resistance pulmonary circulation causes the gas exchange.

The respiratory centers of the pontomedullary area of the brain are responsible for breathing.

SURGICAL APPLICATIONS

Trachea

Some of the most common surgical procedures of the trachea are tracheostomy, tracheal resection, treatment of tracheal stenosis, and treatment of

tracheoesophageal fistulas. The last is considered in the chapter on the esophagus.

At its beginning, the arch of the aorta is located anterior to the trachea; thereafter it is above the left main bronchus. The brachiocephalic artery is in front

of the trachea and then to its right. The left common carotid artery is at first anterior to the trachea and then passes to its left.

Deviation of the trachea to the right or left results from pressure in the neck and mediastinum. The inner surface of the tracheal bifurcation is a sharp ridge

(membranous or cartilaginous) called the tracheal keel or carina. It separates the proximal ends of both bronchi and is a bronchoscopic landmark.

Penetrating wounds of the neck and chest can involve the cervical or thoracic trachea or even one or both bronchi. Blunt chest trauma can produce severe

injuries of the trachea or bronchi, due to the various forces generated during the impact.

The usual site of a tracheostomy is between the second and fourth tracheal rings. The structures encountered are the skin and superficial fascia, investing

layer of deep cervical fascia, and the visceral compartment under the pretracheal fascia. The platysma lies in the superficial fascia, but is absent in the

midline. The anterior jugular veins may lie close to the midline. More importantly, they may be united by a jugular venous arch at the level of the seventh to

eighth tracheal rings.

The sternohyoid and sternothyroid muscles lie between the investing layer of fascia and the pretracheal fascia on either side of the midline.

The inferior thyroid veins arise as a venous plexus on the anterior surface of the isthmus of the thyroid gland. Left and right descending veins enter the

respective brachiocephalic veins (Fig. 6-40). The two veins may form a common trunk entering the superior vena cava or the left brachiocephalic vein.

Fig. 6-40.



The venous drainage of the thyroid gland. The inferior thyroid veins are quite variable. (Modified from Tzinas S, Droulias C, Harlaftis N, Akin JT Jr, Gray SW,

Skandalakis JE. Vascular patterns of the thyroid gland. Am Surg 1976;42:639-644; with permission.)

The isthmus of the thyroid gland commonly lies at the level of the second and third tracheal rings; it is often more cranial, less often more caudal. In about

10 percent of individuals, the two lobes of the thyroid are not connected by an isthmus.28 The isthmus can be retracted upward or downward to reach the

trachea; if necessary, it can be ligated and incised. The possibility of a thyroid ima artery (10 percent of individuals)29 should not be forgotten. A

suspensory ligament of the thyroid and a levator thyroid muscle may also be present in or close to the midline.

Remember

Tracheostomy in children remains controversial because of the possibility of complications. Rocha et al.30 considered the risks resulting from tracheostomy

and intubation acceptable for comatose children in need of prolonged ventilatory support. In an editorial comment on Rocha, Tepas31 questioned the

necessity of early tracheostomy.

Bronchi

To aid the healing of the bronchus, it is prudent for the bronchial stump to be covered by tissue (such as pleurae, muscles, or omentum); this avoids air

leaks and bronchopleural fistula.

Surgery of the bronchi, as well as their surgical complications, are described below in the discussion of the lungs.

Fernando et al.32 advise bronchial artery embolization for treatment of hemoptysis, thereby reducing the need for lung resections.

Lungs

Bronchoscopy, biopsy, segmentectomy, lobectomy, partial lobectomy, total pneumonectomy, and transplantation are done according to the underlying

pathology.

Segments

Each bronchopulmonary segment is an independent and separate unit from a surgical standpoint. It can be excised in toto since there is minimal

anastomosis between the adjacent segments. Pulmonary segmental veins are located between the segments; they are good landmarks for intersegmental

separation and segmental resection.

The apicoposterior segments of the upper lobes and superior segments of the lower lobes are common sites for tuberculosis.

Fissures

Congenital anomalies and variations as well as pathological processes can distort the pathway of the fissures. However, remember that the fissures may be

absent or not well developed, especially the horizontal one.

Thoracoscopy

McFadden and Robbins33 stated that video-assisted thoracoscopy may be used in selected patients. Yim et al.34 found it to be safe and effective both as

a therapeutic and a diagnostic modality for pulmonary tuberculosis in the absence of chronic inflammatory response and distorted anatomy. Liu et al.35

recommended thoroscopy as the treatment of choice for patients with pneumothorax requiring surgical treatment.

Thoracotomy

The lung can be approached by a posterior or anterior thoracotomy or a median sternotomy. The posterior thoracotomy is through the 5th intercostal

space; the anterior thoracotomy is through the 3rd intercostal space. Asaph et al.36 advocate median sternotomy instead of thoracotomy in treatment of

primary pulmonary carcinoma, citing completeness of lymph node staging and favorable wound infection and mortality rates.

Total Pulmonary Resection (Pneumonectomy)

The thin-walled pulmonary artery should be dissected with extreme care by sharp and blunt dissection and finger mobilization. Remember that the recurrent

laryngeal nerve on the left side passes under the aortic arch.

During ligation of the pulmonary veins, shunting of the blood takes place and pulmonary distention does not occur.37 If necessary, enter the pericardium in

order to have enough room for a good pulmonary vein ligation.

To prevent cardiac herniation, either open the pericardial defect widely or repair it with bovine pericardium or prostheses, or primarily.

Close the main bronchus near the carina. This prevents a blind pocket with subsequent breakdown of the bronchial stump or hemoptysis.

Successful video-assisted thoracoscopic lung resection for infants and children was reported by Rothenberg.38 Two patients with metastatic disease

requiring extensive resections were converted to standard thoracotomy.



requiring extensive resections were converted to standard thoracotomy.

Segmental and Lobar Resection

The surgicoanatomic features of segmental and lobar resection are the same as those of pneumonectomy. However, air leaks should be treated by careful

ligation of the small bronchi.

ANATOMIC COMPLICATIONS

Tracheostomy

Tracheostomy may be accomplished using open, percutaneous, or translaryngeal technique. MacCallum et al.39 reported that percutaneous and

translaryngeal tracheostomy have fewer complications than open tracheostomy.

Escarment et al.,40 while mentioning the convenience of percutaneous single-step dilatational tracheostomy, urged further study of long term sequela.

Vascular Injury

ARTERIES

The branches of the superior and inferior thyroid arteries may anastomose across the midline, especially the cricothyroid branches. A thyroid ima artery is

present occasionally, and must be ligated if found.

Overly aggressive sharp dissection can injure the brachiocephalic artery. Erosion caused by tracheostomy tube placement can result in a tracheoarterial or

tracheoesophageal fistula. The subclavian artery can be compromised by a tracheostomy tube that is incorrectly curved or is placed too low (Figs. 6-41A &

B).

Fig. 6-41.

Tracheostomy tubes. A. Tube too curved: the tracheal wall can be eroded and the subclavian artery occluded. B. Tube placed too low: subclavian vessel can be

occluded. C. Tube with correct curvature correctly place

Chapter 6 Respiratory System

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