Transcript 20-trachea

Trachea
It is a mobile tube about 13 cm ( 5 inch )
long & 2.5 cm ( 1 inch ) in diameter. It
has a fibroelastic wall in which are
embedded a U- shaped bars of hyaline
cartilage that keep the lumen patent.
The posterior free ends of the cartilage
are connected by smooth muscle
( trachealis ) .
It lies in the neck below the cricoid
cartilage of the larynx at the level of the
body of the 6th cervical vertebra. It
ends below in the thorax at the level of
the sternal angle ( lower border of the
4th thoracic vertebra ) by dividing into the
right & left principal ( main ) bronchi.
The bifurcation is called the carina. In
deep inspiration the carina descends to
the level of the 6th thoracic vertebra.
Relation of the trachea
Anteriorly: The sternum; thymus; left
brachiocephalic vein; the
origins of the brachiocephalic
& left common carotid arteries
and the arch of aorta.
Posteriorly: The esophagus & the left
recurrent laryngeal nerve.
Right side: The azygos vein ; the right vagus nerve and the pleura.
Left side: The arch of aorta ; the left common carotid & the left subclavian arteries
; the left vagus & the left phrenic nerves and the pleura.
Nerve supply of the trachea are branches of the vagus & recurrent laryngeal nerves
and the sympathetic trunks. They are distributed to the trachealis
muscle and to the mucous membrane lining the trachea.
Principal Bronchi
The main right bronchus is wider ; shorter
and more vertical than the left and is about
2.5 cm ( 1 inch ) long.
Before entering the hilum of the right lung ,
the principal bronchus gives off the
superior lobar bronchus.
On entering the hilum, it divides into a
middle & an inferior lobar bronchus.
The left main bronchus is narrow , longer
and more horizontal than the right & is
about 5 cm ( 2 inches ) long.
It passes to the left below the arch of the
aorta & in front of the esophagus.
On entering the hilum of the left lung, it
divides into a superior & an inferior lobar
bronchus.
Bronchopulmonary Segments
They are the anatomic, functional
and surgical units of the lungs.
Each lobar ( secondary )
bronchus, which passes to a
lobe of the lung gives off
branches called segmental
( tertiary ) bronchi.
Each segmental bronchus passes to a
structurally & functionally independent
unit of a lung lobe called a
bronchopulmonary segment which is
surrounded by connective tissue.
The segmental bronchus ( tertiary ) is
accompanied by a branch of the
pulmonary artery.
But the tributaries of the pulmonary veins
run in the connective tissue between
adjacent bronchopulmonary segments.
Each segment has its own lymphatic
vessels & autonomic nerve supply
On entering a bronchopulmonary
segment each segmental bronchus
divides repeatedly.
As the bronchi become smaller , the U –
shaped bars of the cartilage found in the
trachea are gradually replaced by
irregular plates of cartilage which
become smaller & fewer in number.
The smallest bronchi divide & give rise
to bronchioles which are less than 1
mm in diameter.
Bronchioles posses no cartilage in their
walls & are lined with columnar ciliated
epithelium
The submucosa posses a complete
layer of circularly arranged smooth
muscle fibers.
The bronchioles then divided & give rise to
terminal bronchioles which show delicate
outpouching from their walls.
Gases exchange between blood & air takes place
in the walls of these outpouchings which explains
the name respiratory bronchiole. The diameter of
a respiratory bronchiole is about 0.5 mm.
The respiratory bronchioles end by branching
into alveolar ducts which lead into tubular
passages with numerous thin–walled
outpouching called alveolar sacs.
The alveolar sacs consist of several alveoli
opening into single chamber.
Each alveolus is surrounded by a rich network
of blood capillaries.
Gases exchange takes place between the air in the
alveolar lumen through the alveolar wall into the
blood within the surrounding capillaries.
The respiratory zone includes the respiratory
bronchioles , alveolar ducts, alveolar sacs &
alveoli. It is the only site of gas exchange
The main characteristics of a
bronchopulmonary segment are as
follows:
1- It is a subdivision of a lung lobe.
2- It is pyramid shaped with its apex
toward the lung root.
3- It is surrounded by connective
tissue.
4- It has a segmental bronchus ; a
segmental artery ; lymph vessels
and autonomic nerves.
5-The segmental vein lies in the
connective tissue between adjacent
bronchopulmonary segments.
6- A diseased segment because it is a
structural unit can be removed
surgically.
The main bronchopulmonary
segments are as follows:
Right lung
Superior lobe ( upper ) :
Apical; posterior and anterior.
Middle lobe :
Lateral & medial.
Inferior lobe :
Superior ( apical ) ; medial
basal ; anterior basal ; lateral
basal and posterior basal.
.
Left lung
Superior lobe :
Apical ; posterior ;
anterior ;superior
lingular and inferior
lingular.
Inferior lobe:
Superior ( apical ) ;
medial basal ;
anterior basal ;
lateral basal and
posterior basal.
Clinical Notes
pleurisy
It is an inflammation of the pleura
( pleuritis ). It is secondary to
inflammation of the lung ( pneumonia ).
The pleural surface becomes coated
with inflammatory exudate causing the
surfaces to be roughened. This
roughening produces friction and a
pleural rub can be heard with the
stethoscope on inspiration and
expiration.
Often the exudate becomes invaded
by fibroblasts which lay down
collagen and bind the visceral pleura to
the parietal forming pleural adhesions.
Pleural fluid
The pleural space normally contains 5 to 10 ml of
clear fluid which lubricates the apposing surface of the
visceral & parietal pleurae during respiratory
movements.
The formation of the fluid results from hydrostatic and
osmotic pressures ( proteinates). Because the
hydrostatic pressure ( ionates ) are greater in the
capillaries of the parietal pleura than the visceral
pleura. The pleural fluid normally absorbed into the
capillaries of the visceral pleura.
The mediastinum is
displaced to the left.
The right lung is compressed
The bronchi are narrowed.
Auscultation reveal faint breath
sounds over the compressed
lung and absent breath sounds
over fluid in the pleural cavity.
Any condition that increase the production of the fluid
( inflammation; malignancy and congestive heart failure
or impairs the drainage of the fluid results in the
abnormal accumulation of fluid ( pleural effusion ) and
collapsed lung.
The presence of 300 ml of the fluid in the
costodiaphragmatic recess in an adult is sufficient
to enable it clinical detection .
The clinical sings include decreased lung expansion
on the side of effusion with decreased breath
sounds and dullness on percussion over the effusion.
Pneumothorax
1- Spontaneous pneumothorax
It is a condition in which air enters the pleural
cavity suddenly without its cause being
immediately apparent. After investigation, it is
found that air has entered from a diseased lung
and a bulla ( bleb ) has ruptured.
2- Open pneumothorax:
Stab or gunshot wounds of the thoracic wall may
pierce the parietal pleura so that the pleural
cavity is open to the outside air. Each time the
patient inspires, it is possible to hear air under
atmospheric pressure begin sucked into the
pleural cavity.
3- Tension pneumothorax:
The air may pressed on the wounded side and
pushes the mediastinum toward the opposite
side. In this situation a collapsed lung is on the
injured side and the opposite lung is
compressed by the deflected mediastinum.
Air in the pleural cavity
associated with huge amount
of serous fluid is known as
hydropneumothorax.
If it is associated by pus as
pyopneumothorax.
If is associated with blood as
hemopneumothorax.
blood enters the pleural cavity
through stab or bullet wounds
to the chest wall or from
lacerated lung.
A collection of pus without
air is called an empyema.
Fluid ( serous, blood, or pus ) can be drained from the pleural cavity through
a wide- bore needle.
Inhalation Foreign Bodies
Because the right bronchus is
the wider and more direct
continuation of the trachea
foreign bodies tend to enter
the right instead of the left
bronchus.
From there, they usually pass to
the middle or lower lobe
bronchi.
Foreign bodies may be pins;
toys; parts of teeth which may
be inhaled while a patient is
under anesthesia and parts of
chicken bones.