BRONCHOPULMONARY SEGMENT

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BRONCHOPULMONARY SEGMENT:

BRONCHOPULMONARY SEGMENT DR ARNAB MAJI

WHAT IS BRONCHOPULMONARY SEGMENT :

WHAT IS BRONCHOPULMONARY SEGMENT These are well defined sectors of lung each of which is aerated by a tertiary or segmental bronchus Is a pyramidal shaped segment of lung with its apex facing the lung root and its base at the pleural surface It is largest subdivision of a lobe

BRONCHI AND THEIR DIVISIONS :

BRONCHI AND THEIR DIVISIONS Trachea bifurcates at the level of fifth thoracic vertebra into right and left main bronchi The left one runs more horizontally and right bronchus is more vertical and inferior lobar bronchi is continuation of right bronchus so tracheal bifurcation direct the foreign body towards right lung RIGHT BRONCHUS IS WIDER SHORTER AND MORE VERTICAL THAN LEFT BRONCHUS IT IS WIDER B/C IT SUPPLIES MORE VOLUMINOUS RT LUNG IT IS MORE VERTICAL B/C AT ITS BIFURCATION TRACHEA DEVIATES MORE TO THE RT SIDE

LEFT BRONCHUS:

LEFT BRONCHUS LENGTH - 5 cm RELATIONSHIP DIVISIONS - left main bronchus gives off upper and lower lobe bronchi. The upper lobe bronchus subdivides into apico -posterior and anterior segmental bronchi and a lingular bronchus that divides into superior and inferior bronchi. The left lower lobe bronchus gives off an apical bronchus and then divides into anterior , lateral and posterior segmental bronchi There is no left medial basal segmental bronchus

Left main bronchus and its divisions:

Left main bronchus and its divisions

RIGHT BRONCHUS:

RIGHT BRONCHUS LENGTH - 1- 2.5 cm RELATIONSHIP The right main bronchus divides into right upper lobe bronchus which in turn divides into anterior , apical and posterior segmental bronchi and the bronchus intermedius which latter gives off middle lobe and apical lower lobe bronchi which then divides into basal segmental bronchi: anterior, medial, posterior and lateral segmental bronchi

Right main bronchus and its divisions:

Right main bronchus and its divisions

At a glance:

At a glance

ANOMALY:

ANOMALY They are relatively infrequent Most common anomaly as given by BOYDEN and STRADLING is Sub-apical bronchi i n the lower lobes and a bronchus arising from the trachea to supply the apical segment of the right upper lobe In about 0.25% of right lungs, the so-called azygos lobe may be seen radiologically …….and there is no associated abnormality of bronchial anatomy A sequestrated lobe is a part of lung that has become isolated during development..its bronchi usually cystic and dialated , do not connect with bronchial tree and blood supply derived from the aorta

AZYGOS LOBE :

AZYGOS LOBE Chest x-ray PA view showing azygos lobe

Further divisions of airways:

Further divisions of airways The trachea, main bronchi and lower lobe bronchi are outside the lung substance All other bronchi are situated within the lung and as they enter it they take with them an invagination of the visceral pleura forming a peri -bronchial sheath separated from the bronchi by a potential space The lower divisions of bronchi contain sparse cartilages and become bronchioles, the final branch of this type being the terminal bronchiole Subsequent divisions contain increasing number of alveoli in their walls called respiratory bronchioles

Contd…………….:

Contd ……………. These give off alveolar ducts, the air-sacs and alveoli From the tracheal bifurcation the smallest bronchi are reached after some 8-13 divisions There are about 25000 terminal bronchi and these divides dichotomously to form respiratory bronchioles Up to 9 generations of alveolar ducts occur before the alveolar sac arise as the terminal unit of airways Thus there are about 28 divisions of tracheo -bronchial tree The total no of alveoli has been estimated to be b/w 200 and 600 millions

ACINUS:

ACINUS The acinus is the part of the lung distal to terminal non-alveolated bronchiole It thus consists of up to 3 orders of respiratory bronchioles , each with alveoli arisisng from its walls, usually 3 but up to 9 generations of alveolar ducts, terminal alveolar sacs and alveoli

Lung acini:

Lung acini

Structural details of airways:

Structural details of airways Trachea – lined by a mucous membrane of pseudostratified ciliated columnar epithelium containing goblet cells…. submucosa containing elastic fibres arranged in longitudinal brands and circular fibrocartilagenous layer. Tracheal cartilages are semicircular, the gap being on the posterior part where the circle is completed by membranous portion..the cartilages are connected to each other by fibrous tissue The fibrocartilagenous layer extends down to the smallest bronchus. Bronchioles by definition contain no cartilages

Contd…….:

Contd ……. The respiratory bronchioles contain some muscle bundles, diminishing in amount peripherally and muscle fibres may also be present at the orifices of alveoli that branch off alveolar ducts. The epithelium of respiratory bronchioles contain cuboidal cells away from alveolated portion The alveolar epithelium is flattened and composed largely of type 1 and type 2 pneumocytes Each respiratory bronchiole is accompanied by a muscular pulmonary artery and this side is devoid of alveoli

Contd…………:

Contd ………… Alveolar wall consists of— 1. alveolar epithelial cells 2. their basement membrane 3. a thin interstitial space 4. unmyelinated nerves and occasional macrophages 5. the capillary basement membrane 6. capillary endothelial cells The alveolar capillaries join together to form venules alongside the respiratory bronchioles, that in turn merge into pulmonary vein

Alveolar wall:

Alveolar wall

Contd…………………:

Contd ………………… These vessels lie in the interlobular septa. These septa are connective tissue divisions b/w what are known as secondary lung lobules A primary lobule is defined as an alveolar duct and its distal connections Ventilation of alveoli may occur via collateral pathways as well as directly down the bronchial tree, i.e. via pores of Kohn and also via short bronchiole-alveolar communications There is also evidence of large interbronchiolar communications occuring b/w adjacent respiratory bronchioles

Speciality of broncho-pulmonary segment:

Speciality of broncho -pulmonary segment Broncho -pulmonary segment is respiratory unit. Each BP segment has—pulmonary arteriole, bronchial artery and bronchiole Is separated from adjacent segments by connective tissue septa which from inter segmental planes Is surrounded by connective tissue which is continuous on the surface with the pleura Is supplied independently by a segmental ( tertiary bronchus) and a tertiary branch of the pulmonary artery

Contd……………..:

Contd …………….. Is drained by the inter-segmental parts of the pulmonary veins Pulmonary vein lies in inter-segmental spaces, so during segmental resection surgeon work along pulmonary vein Broncho -pulmonary segment is not a broncho -vascular segment, because it does not have its own vein Each segment has more than one vein and each vein drains more than one segments

APPLIED ANATOMY OF BRONCHOPULMONARY SEGMENT :

APPLIED ANATOMY OF BRONCHOPULMONARY SEGMENT FOREIGN BODY IS MORE LIKELY TO BE ASPIRATED IN RT LUNG WHEN THE SUBCARINAL ANGLE EXCEEDS 90 IT IS MORE LIKELY THAT SUB CARINAL NODES ARE ENLARGED D/T METASTATIC SPREAD FROM LUNG CANCERS OR FROM OTHER MEDIASTINAL GROWTH THE APICAL SEGMENTS OF LOWER LOBE AND POSTERIOR SEGMENT OF UPPER LOBE ARE COMMON SITES FOR LUNG ABSCESS BY ASPIRATIONS B/C THESE SEGMENTS ARE MOST DEPENDENT IN RECUMBENT POSITION…..IN SUCH CONDITION PT IS ADVISED TO LIE IN PRONE POSITION WHICH ALLOW THE INFECTED MATERIAL TO ACCUMMULATE IN THE STEM BRONCHI AND IN THE CARINA SO THAT THE PURULENT MATERIAL CAN BE COUGHED OUT

Contd….:

Contd …. THE APICAL SEGMENTS OF THE LOWER LOBE ARE MOST FREQUENTLY INVOLVED IN ASPIRATION PNEUMONIA ( MENDELSON’S SYNDROME) THE MIDDLE LOBE BRONCHUS IS LONG AND SURROUNDED BY A GROUP OF HILAR LYMPH NODES WHICH DRAIN LYMPHATICS FROM MIDDLE AND LOWER LOBE OF RT LUNG . THEREFORE ENLARGEMENT OF THESE HILAR LYMPH NODES D/T INFECTION OR MALIGNANAT GROWTH OF THE LOWER LOBE MIGHT COLLAPSE THE ENTIRE MIDDLE LOBE OF RT LUNG ( MIDDLE LOBE SYNDROME)