Trachea and bronchi pdf - Thorax

Basic Anatomy

by dividing into right and left principal (main)

carina

line of the neck. In the thorax, the trachea ends below at

level of the 6th cervical vertebra. It descends in the mid

the larynx at the lower border of the cricoid cartilage at the

tube (Fig. 3.9). It begins in the neck as a continuation of

The trachea is a mobile cartilaginous and membranous

Trachea

monary plexus (Fig. 3.7).

touch. It receives an autonomic nerve supply from the pul

but is insensitive to common sensations such as pain and

The visceral pleura covering the lungs is sensitive to stretch

the

nerve

first rib

trachea

cervical dome of

pleura

right vagus

right phrenic

nerve

brachiocephalic

artery

infrahyoid

muscles

thymus left common carotid artery

left internal jugular vein

internal thoracic artery

left phrenic nerve

left vagus nerve

left subclavian artery

left recurrent laryngeal

nerve

first thoracic nerve

thoracic duct

sympathetic trunk

esophagus

superior vena

cava

right phrenic

nerve

right lung

azygos vein

right vagus nerve

trachea

esophagus

sympathetic

trunk

thoracic duct

left recurrent laryngeal

nerve

left lung

left vagus nerve

left phrenic nerve

arch of aorta

manubrium sterni

thymus

FIGURE 3.6

Cross section of the thorax.

below.

At the 4th thoracic vertebra, as seen from

At the inlet, as seen from above.

Phrenic nerves
(C3, C4, and C5)

Intercostal

nerves

(T1-T11)

Parietal pleura

Visceral pleura

Nerves of
pulmonary plexus
(vagus and
sympathetic)

FIGURE 3.7

Diagram showing the innervation of the parietal

and visceral layers of pleura.

CHAPTER 3

muscle.

laryngeal nerves. Sympathetic nerves supply the trachealis

The sensory nerve supply is from the vagi and the recurrent

Nerve Supply of the Trachea

lymph nodes and the deep cervical nodes.

The lymph drains into the pretracheal and paratracheal

Lymph Drainage of the Trachea

ies and the lower third is supplied by the bronchial arteries.

The upper two thirds are supplied by the inferior thyroid arter

Blood Supply of the Trachea

left phrenic nerves, and the pleura (Figs. 3.6, 3.15B,

carotid and left subclavian arteries, the left vagus and

The arch of the aorta, the left common

Left side:

the pleura (Figs. 3.6, 3.15A, and 3.16)

The azygos vein, the right vagus nerve, and

Right side:

The Thorax: Part II—The Thoracic Cavity

■

and 3.17)

Pleural Fluid

bleeding from blood vessels in the chest wall, from vessels in the

In hemopneumothorax, blood enters the pleural cavity. It can

deflected mediastinum. This dangerous condition is called a

on the injured side and the opposite lung is compressed by the

toward the opposite side. In this situation, a collapsed lung is

builds up on the wounded side and pushes the mediastinum

through the wound. In these circumstances, the air pressure

form a valve so that air enters on inspiration but cannot exit

the clothing and the layers of the thoracic wall combine to

pressure being sucked into the pleural cavity. Sometimes

patient inspires, it is possible to hear air under atmospheric

Each time the

pleura so that the pleural cavity is open to the outside air.

Stab wounds of the thoracic wall may pierce the parietal

wall (pneumothorax). In the old treatment of tuberculosis, air was

As the result of disease or injury (stab or gunshot wounds), air

the surfaces to be roughened. This roughening produces fric

surfaces becoming coated with inflammatory exudate, causing

), results in the pleural

inflammation of the lung (e.g.,

decreased breath sounds and dullness on percussion over the

decreased lung expansion on the side of the effusion, with

cient to enable its clinical detection. The clinical signs include

The presence of 300 mL

nancy, congestive heart disease) or impairs the drainage of the

increases the production of the fluid (e.g., inflammation, malig

into the capillaries of the visceral pleura. Any condition that

(pulmonary circulation), the pleural fluid is normally absorbed

the parietal pleura than in the capillaries of the visceral pleura

Since the hydrostatic pressures are greater in the capillaries of

of the fluid results from hydrostatic and osmotic pressures.

parietal pleurae during respiratory movements. The formation

which lubricates the apposing surfaces of the visceral and

The pleural space normally contains 5 to 10 mL of clear fluid,

fluid (e.g., collapsed lung) results in the abnormal accumula-

tion of fluid, called a pleural effusion.

of fluid in the costodiaphragmatic recess in an adult is suffi-

effusion (Fig. 3.8).

Pleurisy

Inflammation of the pleura (pleuritis or pleurisy), secondary to

pneumonia

tion, 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 pleura, forming pleural adhesions.

Pneumothorax, Empyema, and Pleural Effusion

can enter the pleural cavity from the lungs or through the chest

purposely injected into the pleural cavity to collapse and rest the

lung. This was known as artificial pneumothorax. A spontane-
ous pneumothorax is a condition in which air enters the pleural

cavity suddenly without its cause being immediately apparent.

After investigation, it is usually found that air has entered from a

diseased lung and a bulla (bleb) has ruptured.

This condition is called open pneumothorax.

tension pneumothorax.

Air in the pleural cavity associated with serous fluid is known

as hydropneumothorax, associated with pus as pyopneumo-
thorax, and associated with blood as hemopneumothorax.

A collection of pus (without air) in the pleural cavity is called an
empyema. The presence of serous fluid in the pleural cavity is

referred to as a pleural effusion (Fig. 3.9). Fluid (serous, blood, or

pus) can be drained from the pleural cavity through a wide-bore

needle, as described on page 45.

be caused by stab or bullet wounds to the chest wall, resulting in

chest cavity, or from a lacerated lung.

C L I N I C A L N O T E S

bronchi at the level of the sternal angle (opposite the disc

geal nerve (Fig. 3.6A)

The esophagus and the left recurrent laryn

Posteriorly:

(Figs. 3.6A, 3.9, and 3.30)

left common carotid arteries, and the arch of the aorta

cephalic vein, the origins of the brachiocephalic and

The sternum, the thymus, the left brachio

Anteriorly:

num of the thorax are as follows:

The relations of the trachea in the superior mediasti

page 651.

The relations of the trachea in the neck are described on

trachealis muscle.

ends of the cartilage are connected by smooth muscle, the

of hyaline cartilage embedded in its wall. The posterior free

tube is kept patent by the presence of U-shaped bars (rings)

and 1 in. (2.5 cm) in diameter (Fig. 3.9). The fibroelastic

In adults, the trachea is about 4 1/2 in. (11.25 cm) long

6th thoracic vertebra.

and during deep inspiration may be lowered as far as the

ration, the bifurcation rises by about one vertebral level,

between the 4th and 5th thoracic vertebrae). During expi-

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Basic Anatomy

esophagus

trachea

brachiocephalic

artery

arch of aorta

right principal

bronchus

descending aorta

stomach

esophagus

left principal
bronchus

left common
carotid artery

left subclavian
artery

left recurrent
laryngeal nerve

thoracic duct

lumen of right principal bronchus

right principal bronchus

left principal bronchus

carina

FIGURE 3.9

Thoracic part of the trachea. Note that the right

viewed from above is also shown.

ation of the trachea than the left. Bifurcation of the trachea

principal bronchus is wider and has a more direct continu-

trachea
displaced to left

pleural effusion

serous

fluid

absent breath

sounds

collapsed

right lung

diminished breath

sounds

FIGURE 3.8

Case of right-sided pleural effusion. The

inferior lobar bronchus.

superior

the left lung, the principal bronchus divides into a

On entering the hilum of

in front of the esophagus.

(5 cm) long. It passes to the left below the arch of the aorta

and more horizontal than the right and is about 2 in.

The left principal (main) bronchus is narrower, longer,

inferior lobar bronchus

middle

it divides into a

On entering the hilum,

superior lobar bronchus.

off the

the hilum of the right lung, the principal bronchus gives

and 3.19) and is about 1 in. (2.5 cm) long. Before entering

shorter, and more vertical than the left (Figs. 3.9, 3.18,

The right principal (main) bronchus (Fig. 3.11) is wider,

walls of the sacs as diverticula (see page 71).

ducts that enter the alveolar sacs. The alveoli arise from the

Each respiratory bronchiole divides into 2 to 11 alveolar

that terminate in one or more respiratory bronchioles.

mously, giving rise to several million terminal bronchioles

(Figs. 3.9, 3.18, and 3.19). The bronchi divide dichoto

right and left principal (primary or main) bronchi

The trachea bifurcates behind the arch of the aorta into

and absent breath sounds over fluid in the pleural cavity.

reveal only faint breath sounds over the compressed lung

pressed, and the bronchi are narrowed. Auscultation would

mediastinum is displaced to the left, the right lung is com-

The Bronchi

the

Principal Bronchi

and an

and

and an

Compression of the Trachea

lateral or bilateral enlargement of the thyroid gland can cause

The trachea is a membranous tube kept patent under normal

conditions by U-shaped bars of cartilage. In the neck, a uni-

gross displacement or compression of the trachea. A dilatation

of the aortic arch (aneurysm) can compress the trachea. With

each cardiac systole, the pulsating aneurysm may tug at the tra-

chea and left bronchus, a clinical sign that can be felt by palpat-

ing the trachea in the suprasternal notch.

C L I N I C A L N O T E S

(continued)

CHAPTER 3

The Thorax: Part II—The Thoracic Cavity

Tracheitis or Bronchitis

immediate relief to prevent asphyxiation. A method commonly used

membrane of the larynx secondary to infection or trauma may require

Lodgment of a foreign body in the larynx or edema of the mucous

Bronchoscopy enables a physician to examine the interior of the

to enter the right instead of the left bronchus. From there, they

traveling to the central nervous system accompany autonomic

display this phenomenon. The afferent fibers from these organs

not under normal conditions directly relayed to consciousness

It seems that organs possessing a sensory innervation that is

give rise to discomfort that is felt in the midline (see page 224).

pain. Many thoracic and abdominal viscera, when diseased,

burning sensation felt deep to the sternum instead of actual

monary plexus. A tracheitis or bronchitis gives rise to a raw,

The mucosa lining the trachea is innervated by the recurrent

laryngeal nerve and, in the region of its bifurcation, by the pul-

nerves.

Inhaled Foreign Bodies

Inhalation of foreign bodies into the lower respiratory tract is

common, especially in children. Pins, screws, nuts, bolts, pea-

nuts, and parts of chicken bones and toys have all found their

way into the bronchi. Parts of teeth may be inhaled while a

patient is under anesthesia during a difficult dental extraction.

Because the right bronchus is the wider and more direct con-

tinuation of the trachea (Figs. 3.18 and 3.19), foreign bodies tend

usually pass into the middle or lower lobe bronchi.

Bronchoscopy

trachea; its bifurcation, called the carina; and the main bronchi

(Figs. 3.12 and 3.13). With experience, it is possible to examine

the interior of the lobar bronchi and the beginning of the first

segmental bronchi. By means of this procedure, it is also pos-

sible to obtain biopsy specimens of mucous membrane and to

remove inhaled foreign bodies (even an open safety pin).

to relieve complete obstruction is tracheostomy (see page 654).

scalenus anterior
and medius muscles

intercostal
muscles

inspiration

forced
expiration

intercostal
muscles

quadratus lumborum
muscle

diaphragm

rib

liver

FIGURE 3.10

diaphragm to raise the lower ribs.

How the liver provides the platform that enables the

12th rib is fixed or is made to descend by the abdominal muscles.

How the intercostal muscles can be used in forced expiration, provided that the

or, in forced inspiration, raise the 1st rib.

How the intercostal muscles raise the ribs during inspiration. Note that the scaleni muscles fix the 1st rib

Basic Anatomy

trachea

left principal bronchus

right principal
bronchus

right
upper
bronchus

left pulmonary
artery

pulmonary trunk

right

pulmonary

artery

FIGURE 3.11

Relationship of the pulmonary arteries to the

bronchial tree.

FIGURE 3.12

The bifurcation of the trachea as seen through

(Courtesy of E.D. Andersen.)

the right, which is a more direct continuation of the trachea.

the center and the opening into the right main bronchus on

an operating bronchoscope. Note the ridge of the carina in

FIGURE 3.13

The interior of the left main bronchus as seen

lobe bronchus are indicated. (Courtesy of E.D. Andersen.)

left upper lobe bronchus and its division and the left lower

through an operating bronchoscope. The openings into the

FIGURE 3.14

Position of the heart valves. P, pulmonary

least interference.

indicate position where valves may be heard with

Arrows

valve; A, aortic valve; M, mitral valve; T, tricuspid valve.

the lung. This is

y well seen in city dwellers and

especiall

dust particles that become trapped in the phagocytes of

become dark and mottled because of the inhalation of

volume. In the child, they are pink, but with age, they

lungs would immediately shrink to one third or less in

and very elastic. If the thoracic cavity were opened, the

During life, the right and left lungs are soft and spongy

only by its root (Fig. 3.4).

its own pleural cavity, being attached to the mediastinum

cal, covered with visceral pleura, and suspended free in

other structures in the mediastinum. Each lung is coni

rated from each other by the heart and great vessels and

each side of the mediastinum. They are therefore sepa

coal miners. The lungs are situated so that one lies on

Lungs