ANATOMY OF TRACHEOBRONCHIAL TREE

PRESENTED BY- Dr. CHITRA

MODERATOR-Dr.AJAY SOOD

Respiratory System

TRACHEAIt is a cartilaginous and membranous tube

EXTENT - from 6th cervical vertebra till the body of 5th thoracic vertebra

During expiration the bifurcation rises by one vertebral level and during inspiration may be lowered as far as 6th thoracic vertebra

LENGTH - 11cm DIAMETER - 2 to 2.5cm CHILDREN - smaller, deeper, more moveable

STRUCTURE CARTILAGES-16to20 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

4mm deep and 1mm 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 2.5cm 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 5cm in length Smaller in caliber Enters the lung opposite 6th 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

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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 bronchus)

As bronchi become smaller, cartilages also become smaller and fewer in no

Bronchioles are formed which are less then 1mm 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 0.5mm,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 pneumocytes-

large 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,segmental artery,lymph vessels and autonomic nerves

Segmental vein lies between adjacent segments

BLOOD SUPPLY OF LUNGS By bronchial arteries which are

branches of descending aortaNERVE SUPPLY OF LUNGS Pulmonary plexus-efferent and

afferent autonomic nerve fibres Sympathetic efferent fibres produce

bronchodilation and vasoconstriction

Parasympathetic efferent produces bronchoconstriction,vasodilation,increase glandular secretions