ANATOMY OF TRACHEOBRONCHIAL TREE PRESENTED BY Dr CHITRA

ANATOMY OF TRACHEOBRONCHIAL TREE PRESENTED BY- Dr. CHITRA MODERATOR-Dr. AJAY SOOD

Respiratory System

TRACHEA It is a cartilaginous and membranous tube �EXTENT - from 6 th cervical vertebra till the body of 5 th thoracic vertebra �During expiration the bifurcation rises by one vertebral level and during inspiration may be lowered as far as 6 th thoracic vertebra �LENGTH - 11 cm �DIAMETER - 2 to 2. 5 cm �CHILDREN - smaller, deeper, more moveable

STRUCTURE � CARTILAGES-16 to 20 in no. , each forms an incomplete ring, which occupies anterior two third of circumference of trachea � Are placed horizontally above each other, separated by narrow intervals � 4 mm deep and 1 mm thick � Outer surface is flattened in vertical direction and convex from inner side � Highly elastic, but may calcify in later stages � FIRST TRACHEAL CARTILAGE-broader, divided connected to lower end of cricoid by cricotracheal ligament � LAST TRACHEAL CARTILAGE-thick and broad in midlle, lower border is prolonged to a triangular hook shaped process which curves downward and backward between two bronchi

� FIBROUS MEMBRANE-cartilages are enclosed in an elastic fibrous membrane which consists of two layers, one passes over the outer surface the other one over the inner surface � At upper and lower margins they blend together to form a single membrane � MUSCULAR TISSUES-two layers of non –striated muscles longitudinal and transeverse � Longitudinal fibres are external, consist of few scattered bundles only � Transeverse fibers(trachealis muscle) are internal, extends between the end of cartilages

MUCUS MEMBRANE-continous above with larynx and below with bronchus � Consist of areolar and lymphoid tissue, basement membrane, supporting stratified epithelium , surface layer of which is columnar and ciliated � Beneath basement membrane there is a layer of longitudinal elastic fibre � Submucus layer, composed of loose meshwork of connective tissue VESSELS AND NERVES� ARTERIAL SUPPLY-Inferior thyroid arteries � NERVE SUPPLY-vagus nerve, recurrent nerve, sympathetic nerves

RIGHT BRONCHUS � 2. 5 cm long � Wider, shorter, more vertical � Divides into EPARTERIAL and HYPARTERIAL BRONCHUS based on right pulmonary artery

RIGHT UPPER LOBE BRONCHUS � It divides into three segmental bronchi which supply apical, anterior and posterior segments of upper lobe � APICAL SEGMENTAL BRONCHUS-divides into apical and anterior subsegmental branches � POSTERIOR SEGMENTAL BRONCHUS-divides into lateral and anterior subsegmental branches. It serves the posteroinferior part of superior lobe of lung � ANTERIOR SEGMENTAL BRONCHUS-runs anteroinferiorly to supply rest of the part of upper bronchus. Divides into lateral and anterior subsegmental branches

RIGHT MIDDLE LOBE BRONCHUS � Divides into lateral and medial subsegments RIGHT LOWER LOBE BRONCHUS � Continuation of principal stem beyond the origin of middle lobe bronchus � Supplies 5 segments of the lung � Apical segmental bronchus � Medial basal segmental bronchus � Anterior basal segmental bronchus � Lateral and posterior basal segmental bronchus

LEFT BRONCHUS � 5 cm in length � Smaller in caliber � Enters the lung opposite 6 th thoracic vertebra � RELATIONS-passes beneath the aortic arch, crosses in front of oesophagus, thoracic duct, descending aorta, has left pulmonary artery at first above and then in front

LEFT UPPER LOBE BRONCHUS � Cranially it divides into anterior , apical and posterior segmental branches � Caudally into superior and inferior lingual branches LEFT LOWER LOBE BRONCHUS � Divides into apical segmental bronchus, medial basal, anterior basal, lateral and posterior basal branches

BRONCHI • Right bronchus �- – Wider – More vertical – shorter – Supported by C shaped cartilages – 20 -30 degree angle – First generation • Left bronchus – Narrower – More angular – Longer – Supported by C shaped cartilages – 40 -60 degree angle – First generation

CLINICAL SIGNIFICANCE �Right main bronchus is more in line with trachea �Inhaled foreign bodies and gastric contents enter right bronchial tree �If patient is lying on his side, lateral subsegments of anterior and posterior segments are more likely to get such material �If patient is supine, then apical segmental bronchus which arise from right or left lower lobe bronchus is the most common part of lung for the aspirated material to collect

BRONCHOPULMONARY SEGMENTS �Anatomic, functional and surgical units of lung � 23 divisons or generations are involved in dichotomous division, starting from trachea till alveolar sacs �Each lobar bronchus(secondary bronchus) gives off branches called segmental bronchus(tertiary

�As bronchi become smaller, cartilages also become smaller and fewer in no �Bronchioles are formed which are less then 1 mm in dia, no cartilages and lined by ciliated columnar epithelium �Divide to form terminal bronchioles, which show delicate outpouchings from their wall �These are respiratory bronchioles, dia is 0. 5 mm, they end by branching into alveolar ducts

�Each alveolar sac consist of around 17 alveoli �Each alveolus surrounded by rich network of blood capillaries �Gas exchange primarily occurs on thin side of alveolocapillary membrane, thick side provides structural support

ALVEOLI �Type I pneumocyteslarge flattened cells, present a very thin diffusion barrier for gases �Type II pneumocytes -secretes surfactant, which decreases the surface tension between thin alveolar walls �macrophages

�Subdivision of lung lobe �Pyramid shaped, apex towards lung root �Surrounded by connective tissue �Segmental bronchus, segment al artery, lymph vessels and autonomic nerves �Segmental vein lies between adjacent segments

BLOOD SUPPLY OF LUNGS �By bronchial arteries which are branches of descending aorta NERVE SUPPLY OF LUNGS �Pulmonary plexus-efferent and afferent autonomic nerve fibres �Sympathetic efferent fibres produce bronchodilation and vasoconstriction �Parasympathetic efferent produces bronchoconstriction, vasodilation, increas e glandular secretions