12 ana lungs september 30 cinio

ANATOMY - Lungs DR. CINIO September 30, 2013

Lung and its FeaturesLungs -found on each side of the heart with other mediastinal contentParts: apex, 3 borders- anterior, posterior and inferior, three surfaces- costal, diaphragmatic and mediastinalBlunt apex-projects upward into the root of the neck; covered by cervical pleuraConcave base-sits on the diaphragmConvex costal surface-corresponds to chest wallConcave mediastinal surface more pronounced at the left due to concavity of the heart, molded to the pericardium and other mediastinal structures.Hilum-depression in which the bronchi, vessels, and nerves that form the root that enter and leave the lungAnterior borderthin and overlaps the heartPosterior border- lies beside the vertebraCardiac notch- found in the left lungRight lung -625 grams; Left lung -565 grams

Lobes and fissures:Right lung

Has upper, middle and lower lobe divided by horizontal and oblique fissure

Larger than left Broader, has greater capacity Vertically shorter by 2.5 cm

Oblique fissure of right lung corresponds closely to the left oblique fissure, although it is

less vertical crosses the inferior border of the lung 7.5 cm behind its

anterior end on the posterior border it is either levelled with the spine

of T4 or slightly lower descends across the 5th ICS and follows the 6th rib to the

6th costochondral junction from inferior border, upward and backward across the

medial and costal surface until it cuts the posterior border 2.5 in/6.25 cm below the apex

Horizontal fissure of right lung passes from the oblique fissure, near the midaxillary line,

horizontally forwards to the anterior border of the lung, level with the sternal end of the 4th costal cartilage, then passes backwards to the hilum on the mediastinal surface

runs horizontally at the level of 4th costal cartilage and meets the oblique fissure in the midaxillary line

*Middle lobe –small, triangular lobe bounded by oblique and transverse fissure

Left LungOblique fissure of the left lung extends from the costal to the medial surfaces of the lung

both above and below the hilum superficially this fissure begins on the medial surface at

the posterosuperior part of the hilum ascends obliquely backwards to cross the posterior

border of the lung 6 cm below the apex, then descends forwards across the costal surface, to reach the lower border almost at its anterior end

finally ascends on the medial surface to the lower part of the hilum

at the posterior border of the lung the fissure usually lies opposite a surface point 2 cm to the side of the midline between the spines of T3 and T4 but it may be above or below this level

traced around the chest, the fissure reaches the 5th ICS (at or near the midaxillary line) and follows this to intersect the inferior border of the lung close to, or just below, the 6th costochondral junction (7.5 cm from the midline)

more vertical than the right, and is indicated approximately by the medial border of the scapula when the arm is fully abducted above the shoulder

left horizontal fissure is a normal variant found in c.10% of patients.

Apex of lungs: protrudes above the thoracic inlet rises 3-4 cm above the level of the costal cartilage,

posterior of the neck of the first rib summit is 2.5 cm above the medial third of the clavicleRelations of the apex are as follows: Anterior: subclavian artery, anterior scalene muscle,

subclavian vein, phrenic nerve, vagus nerve

*Subclavian artery: arches up and laterally over the suprapleural membrane; groups the anterior surface of the apex near its summit

Posterior: cervicothoracic or sympathetic ganglia, ventral ramus of the 1st thoracic nerve, superior intercostal artery

Medial: Right lung (bracheocephalic trunk, right bracheocephalic vein, trachea); Left lung (left subclavian artery and left bracheocephalic vein)

Lateral: scalenus medius muscle, first rib

Base of lungs: Semilunar and concave Rest upon the superior surface of the diaphragm Diaphragm extends higher on the right Concavity is deeper on the right lung Posterolaterally the base has a sharp margin that projects a

little into the costodiaphragmatic recess


Surfaces of lung:Costal SurfaceSmooth and convexShape is adopted to that of the thoracic wall which is

vertically deeper posteriorly At contact with the costal pleura and exhibits in specimens

preserved in situ, grooves then corresponds with the overlying ribs

Medial Surface Vertebral part…Lies in contact with: thoracic vertebrae and intervertebral

disc, posterior intercostals vessels, splanchnic nervesMediastinal part…Deeply concave adapted to the cardiac impression, much

larger and deeper on the left lung where the heart projects more to the left of the median plane

Hilum and pulmonary ligament

Other Impression on the Lung Surface:Right LungCardiac impression is related to the anterior surface of the

right auricle, anterolateral surface of the right atrium and partially to the anterior surface of the right ventricle

Impression ascends anterior in the hilum as a wide groove for the superior vena cava and the end of the right bracheocephalic vein

Posteriorly the groove is joined by a deep sulcus which arches forwards above the hilum and is occupied by the azygous vein.

Groove for right side of the esophagusShallow vertical groove behind the hilum and pulmonary

ligament Towards the diaphragm it inclines left and leaves the right

lungPosteroinferiorly the cardiac impression is confluent with a

short wide groove adapted to the inferior vena cavaBetween the apex of the groove for the azygous, the

trachea and right vagus are close to the lung

Left LungCardiac impression is related to the anterior and lateral

surface of the left ventricle and auricleThe anterior infundibular surface of the right ventricle

related to the lung as it ascends in front of the hilum to accommodate the pulmonary trunk

A large groove arches over the hilum descends behind it and the pulmonary ligament

Summit – a narrower groove ascends to the apex for the left subclavian artery

Behind and above the aortic groove the lung is in contact with the thoracic duct and esophagus

In front of the subclavian groove, faint linear depression for the left brachiocephalic vein

Inferiorly – the esophagus mould the surface in front of the lower end of the pulmonary ligament

Borders of the lung:INFERIOR BORDER thin and sharp where it separates the base from the costal

surface and extends into the costodiaphragmatic recess more rounded medially where it divides the base from the

mediastinal surface corresponds, in quiet respiration, to a line drawn from the

lowest point of the anterior border which passes to the 6th rib at the midclavicular line, then to the 8th rib in the midaxillary line (10 cm above the costal margin), and then continues posteriorly, medially and slightly upwards to a point 2 cm lateral to the tenth thoracic spine

POSTERIOR BORDERSeparates the costal surface from the mediastinal, and

corresponds to the heads of the ribsNo recognizable markings and is really a rounded junction

of costal and vertebral (medial) surfaces

ANTERIOR BORDERThin, sharpOverlaps the pericardiumON THE RIGHT - Corresponds closely to the

costomediastinal line of pleural reflection and is almost vertical

ON THE LEFT – approaches the same line above; however, below the 4th costal cartilage, it shows a variable cardiac notch, the end of which passes laterally for 3.5 cm before curving down and medially to the 6th costal cartilage 4 cm from the midline

Bronchopulmonary Segments:Structurally separate, functionally independent, unit of lung

tissueEach of the principal bronchi divides into lobar bronchi’Each segment is surrounded by connective tissue that is

continuous with the visceral pleura, and is a separate respiratory unit

The main characteristics of a bronchopulmonary segment may be summarized as follows:

It is a subdivision of a lung lobe It is a pyramid shaped, with its apex toward the lung root It is surrounded by connective tissue It has a segmented bronchus, a segmental artery, lymph

vessels, and autonomic nervesThe segmental vein lies in the connective tissue

between adjacent bronchoplmonary segmentsBecause it is a structural unit, a diseased segment can be

removed surgically


Table: Major Structures and Corresponding Generations of the Tracheobronchial Tree

Conducting zone

Structures of the Lungs

Generations*

Cartilagenous airways

Trachea 0Main stem bronchi

1

Lobar bronchi

2

Segmental 3Subsegmental bronchi

4-9

Bronchioles 10-15 Noncartilagenous airwaysTerminal

bronchioles16-19

Respiratory zone

Respiratory bronchioles†

20-23Sites of gas exchangeAlveolar

ducts†24-27

Alveolar sacs†

28

*Note: The precise number of generations between the subsegmental bronchi and the alveolar sacs is not known.

†These structures collectively are referred to as a primary lobule (see pages 36–39) or lung parenchyma; they are also called terminal respiratory units and functional units

Pulmonary HilaPrincipal bronchus, pulmonoary artery, bronchial vessels, a

pulmonary autonomic plexus, bronchopulmonary lymph nodes and loose connective tissue

Pulmonary roots pedicles, lie opposite the bodies of the 5th

to 7th thoracic vertebraeCommon anterior relations: Phrenic nerve,

pericardiophrenic artery and vein, and anterior pulmonary plexus

Common posterior relations: vagus nerve and posterior pulmonary plexus

The pulmonary ligament is inferior

The major structures in both roots are similarly arranged:Upper of the two pulmonary veins – in front The pulmonary artery and principal bronchus are behindBronchial vessels - most posterior

RIGHT HILUMRoot is situated behind the superior vena cava and right

atrium, and below the terminal part of the azygous veinThe sequence from above downwards;Superior lobar bronchusPulmonary arteryPrincipal bronchus Lower pulmonary vein

LEFT HILUMRoot lies below the aortic arch and in front of the

descending thoracic aortaThe vertical sequence at the left hilum:Pulmonary arteryPrincipal BronchusLower pulmonary veinThe pulmonary artery is longer in the left lung

Secondary Pulmonary Lobules:Each segmental bronchus – supplies a bronchopulmonary

segmentProgressive subdivision of the bronchus occur within each

segments All intrapulmonary bronchi are kept patent by cartilaginous

plates, which decline in size and number and finally disappear when the tubes are less than 1 mm in diameter (bronchioles)

The primary lobule is the lung distal to the respiratory bronchiole (?)

The secondary lobule is the smallest subsection of the peripheral lung bounded by connective tissue septa and consists of approximately six terminal bronchioles

The connective tissue septa are uneven in both size and shape

Vascular Supply and Lymphatic Drainage:Two functionally distinct pathways- Pulmonary vessels: convey deoxygenated blood to the

alveolar walls; drain oxygenated blood back to the left side of the heart

- Bronchial vessels: from the systemic circulation; provide oxygenated blood to lung tissues which do not have close access to atmospheric Oxygen e.g. those of the bronchi and larger bronchioles

Pulmonary artery – right and left arteries pass to the hila of the lungs- divide into branches that accompany segmental and subsegmental bronchi and mostly dorsolateral

Pulmonary capillaries from plexuses immediately outside the epithelium in the walls and septa of alveoli and alveolar sacs

Pulmonary veins – two from each lung, drain the pulmonary capillaries

Their radicles coalesce into larger branches which traverse the lung independently of the pulmonary arteries and bronchi

Communicating freely, they form large vessels that ultimately accompany the arteries and bronchial tubes to the pulmonary hilum, where the bronchi often separate the dorsolateral artery and the ventromedial vein


The pulmonary vein open into the left atrium and convey oxygenated blood for systemic distribution by the left ventricle

Pulmonary hepatic vessels originate in a superficial subpleural plexus

A deep plexus accompanies the branches of the pulmonary vessels and bronchi

Superficial efferents turn normal lung borders and the margins of fissures to converge in the bronchopulmonary nodes

There is little anastomosis between the superficial and the deep lymphatics, except in the hilar regions

Deep in the fissures, lymphatic vessels of adjoining lobes connect

Consequently, although there is a tendency for vessels from the upper lobes to pass to the superior tracheobronchial nodes, and those from lower lobes to the inferior tracheobronchial group, these groups are not exclusive.

RIGHT LUNGSuperior right pulmonary vein …union of apical, anterior and posterior veins (draining the

upper lobe) with a middle lobar vein (formed by lateral and medial tributaries) in the hilum

Inferior right pulmonary vein …hilar union of superior (apical) and common basal veins

from the lower lobeThe union of superior and inferior basal tributaries forms

the common basal veinThe right pulmonary artery divides into two large branches

as it emerges behind the superior vena cava A lymph node usually occupies the bifurcationSuperior branch – smaller of two, goes to the superior lobe

and usually divides into the further branches, which supply the majority of that lobe

Inferior branch – descends anterior to the intermediate bronchus and immediately posterior to the superior pulmonary vein

…Provides a small recurrent branch to the superior lobe …Middle lobe anteriorly and the branch to the superior

segment of the inferior lobe posteriorly …Inferior lobe segments

LEFT LUNGSuperior left pulmonary vein

Drains the upper lobeUnion of apicoposterior (draining the apical and posterior

segments) anterior and lingular veinsInferior left pulmonary vein

Drain the lower lobe Hilar union of the superior apical and common basal

(superior and inferior basal vein)Tributaries of pulmonary vein receive smaller tributaries

Innervation: Vagal fibers

Supply the bronchial muscles and glandsBrochoconstrictor and secretomotor

Efferent sympathetic fibers InhibitoryRelax the bronchial smooth muscleVasoconstrictor effects

Pulmonary plexusesThe pulmonary plexuses are anterior and posterior to the

other hilar structures of the lungsThe anterior plexus is much smaller and is formed by rami

from the vagal and cervical sympathetic cardiac nerves as direct branches from both sources

The left plexus also receives branches from the left recurrent laryngeal nerve

Blood supply of the lungs is two foldUnoxygenated blood is pumped to the lung from the right

ventricle by the way of pulmonary veinAfter oxygenation in the lung, the blood is returned to the

left atrium by the way of pulmonary veinBlood supply to the bronchi is from the systemic circulation

by bronchial arteries arising from the superior thoracic aorta or the aortic arch, either as discrete branches or in combination with the intercostal arteries

In most individuals, there are 2 left and 1 right main bronchial artery

The bronchi, the connective tissue of the lung and the visceral pleura receive their blood supply from the bronchial arteries which are branches of descending aorta.

The bronchial vein which communicate with the pulmonary vein drains into the azygus and hemi azygus vein

Lymph drainage pathway:

Superficial and deep plexus ----- pulmonary nodes -----brochopulmonary nodes ----- tracheobronchial ----tracheomeddiastinal ----- cephalad

The lymphatic sump of Borne includes the groups of lymph nodes that receive lymphatic drainage from all pulmonary lobes of the corresponding lung.

Lymphatic vessels are present throughout the parenchyma and gradually coalesce toward the hilar area of the lungs.

Generally, lymphatic drainage from the lungs affect the ipisilateral lymph nodes, however the flow of lymph from the left lower lobe may drain to the right mediastinal lymph vessels

Reference for reading: Gray's Anatomy, 39th Edition.Susan Standring.2008.

12 ana lungs september 30 cinio

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