The document outlines the anatomy of the trachea, bronchi, and lungs, detailing their structure, development, and clinical significance. It emphasizes the embryological milestones for the lower respiratory tract, the differences between the right and left main bronchi, and the intricacies of lung anatomy including blood supply and nerve innervation. Furthermore, it highlights the clinical considerations related to these anatomical structures, such as the implications for procedures like endotracheal intubation and potential congenital anomalies.

1. Anatomy Of
Trachea, Bronchi
And Lungs
Modulator : Dr . Diriba G( MD,
Assistant Professor Of Surgery)
Presenter : Dr. Gizachew A (GSR-I)
May 22, 2024
Ambo
2024/6/12 Anatomy of trachea, bronchus and lungs 1

2. Outline
• Introduction
• Surgical Embryology
• Anatomy of Trachea
• Anatomy of Bronchi
• Anatomy of Pleura and Lung
• Surgical Importance of the Anatomy and Clinical
Correlations
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3. Introduction
• Development of lower respiratory tract begins to form
during 4th weeks (laryngo tracheal groove).
• The trachea is a midline structure and lies just anterior
the esophagus.
• The trachea divides into the left and right main stem
bronchi at junction point carina.
• The lungs are the vital organs of respiration.
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4. Embryology
Lower respiratory tract has five milestones of
development.
• Embryologic period (3 - 6 weeks)
• Pseudo glandular period (5 -17 weeks)
• Canalicular period (17 - 25 weeks)
• Terminal Sac period (24 weeks - birth)
• Alveolar period (32 weeks- 8 years)
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5. Trachea
• AKA the windpipe
• Is a cartilaginous tube that connects the larynx to
the bronchi of the lungs.
• Has an inner diameter of about 1.5 to 2cm.
• Length of about 10 to 11 cm.
• Wider in males than females.
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7. Cont...
• It begins at the lower edge of the cricoid cartilage
of the larynx C6 and
• Ends at the carina, the point where the trachea
branches into left and right main bronchi T4
• Is surrounded by 16–20 rings of hyaline cartilage;
• These 'rings' are 4mm high in the adult, incomplete
and C-shaped.
• Ligaments connect the rings.
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8. Cont...
• The trachealis muscle connects the ends of the
incomplete rings
• Adventitia, which is the outermost layer of
connective tissue that surrounds the hyaline
cartilage
• Can be displaced normally to the right by the aortic
arch.
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10. Relations of trachea in the neck
• Anteriorly: skin, fascia, isthmus of the thyroid gland
(ring 2-4), inferior thyroid vein, jugular arch, thyroid
ima artery, the left brachiocephalic veins in
children, overlapped by the sternothyroid and
sternohyoid muscles.
• Posteriorly: right and left recurrent laryngeal
nerves and esophagus
• Laterally: lobes of the thyroid glands and the
carotid sheath and its contents.
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11. Relations of trachea in the thorax
• Anteriorly: the sternum, the thymus, he left
bracheocephalic vein, the origins of
bracheocephalic and left common carotid arteries
and the arch of aorta.
• Posteriorly: the esophagus and the left recurrent
laryngeal nerve
• Right side: the azygos vein, the right vagus nerve
and the pleura
• Left side: the arch of the aorta, the left common
carotid and left subclavian arteries, the left vagus
and left phrenic nerves and the pleura.
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13. Blood supply
• The proximal trachea supplied by the inferior thyroid
artery and innominate artery.
• The distal trachea, carina, and bronchi are supplied
by the bronchial arteries.
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15. Nerve supply
Para sympathetic:
• Vagus and recurrent laryngeal nerves
Sympathetic:
• Middle cervical ganglion (vasomotor)
Lymphatic Drainage
• Pretracheal
• Para tracheal lymph node
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17. Cont...
Development
• In the fourth week the tracheoesophageal septum is
formed.
• Divides the foregut tube into the laryngotracheal tube.
• By the start of the fifth week, the left and right main
bronchi have begin to form, initially as buds at the
terminal end of the trachea.
• The trachea is no more than 4 mm in diameter during the
first year of life, expanding to its adult diameter of
approximately 2cm by late childhood.
• The trachea is more circular and more vertical in children
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18. Microanatomy
• The trachea is lined by psedostratified ciliated
columnar cells.
• The epithelium contains goblet cells, which are
glandular, column-shaped cells that produce
mucins, the main component of mucus.
• Mucociliary clearance.
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20. Clinical significance of trachea
• The insertion of an endotracheal tube is a procedure that
may be required for resuscitation of the newborn at birth
and subsequently to enable artificial ventilation.
• The tube is introduced usually orally initially and guided
through the vocal cords with the help of a laryngoscope.
• The length of the trachea in the neonate can be as short as
3.1 cm in premature infants, and the T1-to-carina distance
ranges from 1.4 cm in babies weighing 500–1000 g, to 1.8
cm in those weighing 3001–3500 g.
• Once in place, the tip of the tube should be in the mid
trachea, above the carina.
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21. Cont...
• The required length of the tube can be estimated according to
birth weight.
• Confirmation of correct positioning of the endotracheal tube is
obtained from a chest X-ray.
• The anatomical reference points used for the X-ray to assess the
position
 the clavicles,
 the bodies of the vertebrae and
 the carina (although not always visible on X-ray).
• Previously, it was advised that the tip of the endotracheal tube
should be placed just below the clavicles, at the level of the first
rib or 1–2 cm above the carina.
• It is now suggested that the body of the first thoracic vertebra
(T1) is a more stable reference point as the target for the tip of
the endotracheal tube.
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22. Clinical Correlations Of Trachea
Congenital & others
• Tracheoesophageal fistula
• Tracheal injury
• Tracheal stenosis
• Tracheomalacia
• Infectious disease( tbc,
histoplasmosis,..)
• Burn trauma
• Post-intubation and post-
tracheostomy injuries
• Tracheal resection complication
• Tracheal agenesis/ atrsia
External lesions vs trachea
• Goiter( compressive effect)
• Vascular compression(vascur
rings)
• Mediastinal masses(e.g m.
neoplasms)
• Postpneumectomy syndrome
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23. Anatomy of Bronchus
• Is a passage or airway in the lower respiratory tract
that conducts air into the lungs.
• The first or primary bronchi to branch from the
trachea at the carina are the right main bronchus
and the left main bronchus.
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24. Anatomical differences of The right main
bronchus and left main bronchus
Right main Bronchus
• Shorter(2,5cm)
• Larger diameter (5cm)
• More vertical (susceptible
to aspiration)
• Passes directly to the hilum
of the lung.
• Gives 3 lobar bronchi(RSLB,
RMLB, RILB), RSLB branches
before entering hilum
• Enters hilum @ opposite to
T5.
Left main Bronchus
• Longer (5cm)
• Smaller diameter
• More horizontal relative to
trachea
• Gives 2 lobar bronchi after
entering hilum @ T6
• Passes to the left inferior to
the aortic arch, it crosses
anterior to the oesophagus,
thoracic duct and
descending aorta; the LPA is
at first anterior and then
superior to it.
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25. Cont....
• Within the lungs, the bronchi branch in a constant
fashion to form the branches of the tracheobronchial
tree.
• The main bronchi branch into narrower secondary
bronchi or lobar bronchi.
• Each lobar bronchus divides into several tertiary or
segmental bronchi that supply the bronchopulmonary
segments.
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26. Cont...
The bronchopulmonary segments are:
• The largest subdivisions of a lobe. Usually 18-20 in
number (10 in the right lung; 8-10 in the left lung).
• Separated from the rest of the lung by a septum of
connective tissue.
• Surgically resectable.
• Drained by intersegmental parts of the pulmonary
veins that lie in the connective tissue between and
drain adjacent segments.
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28. Cont...
• Beyond the tertiary segmental bronchi there are 20 to
25 generations of branching conducting bronchioles
that eventually end as terminal bronchioles.
• Bronchioles lack cartilage in their walls.
• Conducting bronchioles transport air but lack glands or
alveoli.
• Each terminal bronchiole gives rise to several
generations of respiratory bronchioles, characterized
by scattered, thin-walled out pocketings (alveoli) that
extend from their lumens.
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29. Cont...
• The pulmonary alveolus: is the basic structural unit of gas
exchange in the lung.
• Due to the presence of the alveoli, the respiratory
bronchioles are involved both in air transportation and
gas exchange.
• Each respiratory bronchiole gives rise to 2-11 alveolar
ducts, each of which gives rise to 5-6 alveolar sacs.
• Alveolar ducts are elongated airways densely lined with
alveoli
• New alveoli continue to develop until about age 8 years,
by which time there are approximately 300 million
alveoli.
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31. Blood supply
The bronchial arteries:
• Provide 1% of total blood flow to the lungs and
• Supply the visceral pleura, intrapulmonary blood
vessel walls, and lymphatic system.
The pulmonary arteries:
• Provide the other 99% of the total blood flow to
the lung
Venous drainage
• Into the azygous and hemiazygous systems
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33. Bronchi cilinical cosideration
• Foreign body aspiration
• Broncoscopy
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34. Anatomy of Lungs
The lungs are separated from each other by the
mediastinum.
• Each lung has:
An apex and a base.
Two or three lobes, created by one or two fissures.
Three surfaces (costal, mediastinal, and diaphragmatic).
Three borders (anterior, inferior, and posterior).
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35. Cont...
• The anterior borders of the lungs lie between the
2nd and 4th costal cartilages.
• The anterior border of the left lung is more deeply
indented by its cardiac notch.
• The inferior margins of the lungs reach:
MCL at the level of the 6th rib
MAL at the 8th rib, and
 SL at the 10th rib, proceeding toward the spinous
process of T10 vertebra.
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36. Cont...
• The oblique fissure of the lungs extends from T2
vertebra posteriorly to the 6th costal cartilage
anteriorly.
• The horizontal fissure of the right lung extends
from the oblique fissure along the 4th rib and
costal cartilage anteriorly.
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38. Cont...
• The lungs are attached to the mediastinum by the
roots of the lungs—that are :
The bronchi (and associated bronchial vessels)
Pulmonary arteries
Superior and inferior pulmonary veins
The pulmonary plexuses of nerves
Lymphatic vessels .
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39. Blood supply of the lungs
Arterial supply
1. Bronchial arteries:
• Supplies the bronchial tree, the connective tissue stroma,
and visceral pleura
• The two left bronchial arteries usually arise directly from
the thoracic aorta.
• The single right bronchial artery may also arise directly
from the aorta
2. Pulmonary arteries:
• Arise from the pulmonary trunk.
• Each lung receives one pulmonary artery
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40. Cont...
Veneous
Bronchial veins:
• They drain into the azygos (rt) and hemiazygos
veins (lt)
Pulmonary veins:
• Superior and inferior
• The middle lobe vein is a tributary of the right
superior pulmonary vein.
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41. Cont...
• The arteries and bronchi are paired in the lung,
branching simultaneously and running parallel
courses.
• The pulmonary veins run independently of the
arteries and bronchi in the lung.
• Each pulmonary artery divides to secondary lobar
arteries
• Lobar arteries divide into tertiary segmental
arteries.
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42. Cont...
• The veins from the visceral pleura and the
bronchial venous circulation drain into the
pulmonary veins
• Veins from the parietal pleura join systemic veins
in adjacent parts of the thoracic wall.
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44. Lymphatic drainage
• The lymph from the lung is drained by two sets of
lymph vessels.
Superficial vessels
Deep vessels
• All the lymph is drained into tracheobronchial lymph
nodes (located at the hilum), which in turn drain into
bronchomediastinal lymph nodes.
• The lymphatic drainage of the lung is clinically
important because lung cancer spreads by lymphatic
path.
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46. Nerve supply
Nerves of Lungs and Pleurae
• Are derived from the pulmonary plexuses anterior and
(mainly) posterior to the roots of the lungs.
• These nerve networks contains :
• Parasympathetic ,sympathetic and visceral afferent
fibers.
The parasympathetic fibers
• Are presynaptic fibers from the vagus nerve (CN X).
• Are bronchoconstrictor, vasodilator and
secretomotor
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47. Cont...
The sympathetic fibers
• Derived from T2 to T5 spinal segments.
• Are bronchodilator, vasoconstrictor and secretory
The visceral afferent fibers
• Are either reflexive (conducting subconscious
sensations associated with reflexes that control
function) or nociceptive (conducting pain impulses
generated in response to painful or injurious stimuli,
such as chemical irritants, ischemia, or excessive
stretch).
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49. Anatomy of pleura
1. The visceral pleura and 2. The parietal pleura
The visceral pleura
• Invests all surfaces of the lungs
• Is pulmonary pleura
• Produce and reabsorb fluid.
• Insensitive to pain.
• Cannot usually be dissected
• It provides the lung with a smooth slippery surface,
• Is continuous with the parietal pleura at the hilum of the
lung.
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50. Cont...
The parietal pleura
• Lines the pulmonary cavities.
• It is thicker than the visceral pleura .
• Can be dissected or separated from the surfaces it covers.
• Limit fluid loss and reduce friction.
• Sensetive to pain
• Consists of three parts—
Costal
 Mediastinal, and
 Diaphragmatic—and the cervical pleura.
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51. Cont...
The costal part of the parietal pleura
• It is separated from the internal surface of the thoracic
wall by endothoracic fascia.
The mediastinal part of the parietal pleura
• (mediastinal pleura) covers the lateral aspects of the
mediastinum.
• It continues superiorly into the root of the neck as
cervical pleura.
The diaphragmatic part of the parietal pleura
• covers the superior (thoracic) surface of the diaphragm
on each side of the mediastinum
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52. Cont...
The cervical pleura
• Is reinforced by a fibrous extension of the
endothoracic fascia, the supra pleural membrane
(Sibson fascia). The membrane attaches to the
internal border of the 1st rib and the transverse
process of C7 vertebra .
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53. Cont...
Pleural Recesses
• An area where adjacent surfaces of the partial
pleura come in to contact.
• Are two in numbers
The costo diaphragmatic recesses
The costo mediastinal recesses
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55. Surgical Importance and Clinical
Correlations
Lung and Pleura
• Thoracostomy
• Pneumothorax
• Hemothorax
• Pneumohemothorax
• Lung resection
• Lung cancer
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56. Reference
• Moore, K. L., & Dalley, A. F. (2018). Clinically
oriented anatomy. Wolters kluwer india Pvt Ltd.
• Illman, J. (2020). Seymour Schwartz: surgeon,
editor, cartographer, and historian.
• Lee John Skandalakis - Surgical Anatomy: The
Embryologic and Anatomic Basis of Modern
Surgery-Paschalidis (2004)
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57. Thank you for you
Attention!
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