CHAPTER 2: THORAX PART II: THE THORACIC CAVITY Flashcards

1
Q

OBJECTIVES

■■ To understand the general arrangement of the thoracic viscera and their relationship to one another and to the chest wall.

■■ To be able to define what is meant by the term mediastinum and to learn the arrangement of the pleura relative to the lungs. This information is fundamental to the comprehension of the function
and disease of the lungs.

■■ Appreciating that the heart and the lungs are enveloped in
serous membranes that provide a lubricating mechanism for these mobile viscera and being able to distinguish between such terms as thoracic cavity, pleural cavity (pleural space),
pericardial cavity, and costodiaphragmatic recess.

■■ To learn the structure of the heart, including its conducting system and the arrangement of the different chambers and valves, which is basic to understanding the physiologic and pathologic features of the heart.

The critical nature of the
blood supply to the heart and the end arteries and myocardial
infarction
is emphasized.
■■ To understand that the largest blood vessels in the body are located within the thoracic cavity, namely, the aorta, the pulmonary arteries, the venae cavae, and the pulmonary veins.

Trauma to the chest wall can result in disruption of these
vessels, with consequent rapid hemorrhage and death.
Because these vessels are hidden from view within the
thorax, the diagnosis of major blood vessel injury is often
delayed, with disastrous consequences to the
patie

A
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2
Q

What are the bounderies of the Chest Cavity?

A

The chest cavity is bounded by the chest wall and below by the diaphragm. It extends upward into the root of the neck about one fingerbreadth above the clavicle on each side (see
Fig. 3.5).

The diaphragm, which is a very thin muscle, is the
only structure (apart from the pleura and the peritoneum) that separates the chest from the abdominal viscera.

The
chest cavity can be divided into a median partition, called the mediastinum, and the laterally placed pleurae and lungs (Figs. 3.1, 3.2, and 3.3).

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3
Q

What is the only structure (apart from the pleura and the peritoneum) that separates the chest from the abdominal viscera.

A
The diaphragm, which is a very thin muscle, is the
only structure (apart from the pleura and the peritoneum) that separates the chest from the abdominal viscera.
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4
Q

The chest cavity can be divided into a :

A
  • median partition, called the mediastinum,
  • and the laterally placed pleurae andlungs (Figs. 3.1, 3.2, and 3.3).
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5
Q

Describe the mediastinum.

A

The mediastinum, though thick, is a movable partition that extends superiorly to the thoracic outlet and the root of the neck and inferiorly to the diaphragm.

It extends anteriorly to the sternum and posteriorly to the vertebral column.

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6
Q

The mediatstinum contains the:

A

It contains the remains of the thymus, the heart and large blood vessels, the trachea and esophagus, the thoracic duct and lymph nodes, the vagus and phrenic nerves, and the sympathetic trunks.

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7
Q

The mediastinum is divided into __________-by an imaginary plane passing from the sternalangle anteriorly to the lower border of the body of the 4th thoracic vertebra posteriorl

A

superior and inferior mediastina

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8
Q

The inferior mediastinum
is further subdivided into the ___________

A
  • middle mediastinum
    • ​which consists of the pericardium and heart; the anterior mediastinum, which is a space between the pericardium and the sternum
  • and the posterior mediastinum,
    • which lies between the pericardium and the vertebral column.
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9
Q

For purposes of orientation, it is convenient to remember
that the major mediastinal structures are arranged in
the following order from anterior to posterior

A
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10
Q

What are the bounderies of the Superior Mediastinum?

A

Superior Mediastinum

The superior mediastinum is bounded by

  • front :manubrium sterni
  • behind: first four thoracic vertebrae (see Fig. 3.2).
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11
Q

What are the contents of the Superior Mediastinum?

A
  • (a) Thymus,
  • (b) large veins,
  • (c) large arteries,
  • (d) trachea,
  • (e) esophagus and
  • thoracic duct, and
  • (f) sympathetic trunks
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12
Q

What are the contents of the Inferior Mediastinum?

A
  • (a) Thymus,
  • (b) heart within the pericardium with the phrenic nerves on each side
  • , (c) esophagus and thoracic duct,
  • (d) descending aorta, and
  • (e) sympathetic trunks
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13
Q

What are the bounderies of inferior mediastinum?

A

The inferior mediastinum is bounded in

  • front: body of the sternum and
  • behind by the lower eight thoracic vertebrae
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14
Q

Deflection of Mediastinum

A

In the cadaver, the mediastinum, as the result of the hardening effect of the preserving fluids, is an inflexible, fixed structure.

In the living, it is very mobile; the lungs, heart, and large arteries are in rhythmic pulsation, and the esophagus distends as each bolus
of food passes through it.

If air enters the pleural cavity (a condition called pneumothorax), the lung on that side immediately collapses and the mediastinum is displaced to the opposite side.

This condition reveals
itself by the patient’s being breathless and in a state of shock; on examination, the trachea and the heart are found to be displaced
to the opposite side.

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15
Q

Mediastinitis

A

The structures that make up the mediastinum are embedded in loose connective tissue that is continuous with that of the root of the neck.

Thus, it is possible for a deep infection of the neck
to spread readily into the thorax, producing a mediastinitis.
Penetrating wounds of the chest involving the esophagus may produce a mediastinitis.

In esophageal perforations, air escapes into the connective tissue spaces and ascends beneath the fascia to the root of the neck, producing subcutaneous emphysema

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16
Q

What is subcutaneous emphyema?

A

In esophageal perforations, air escapes into the connective tissue spaces and ascends beneath the fascia to the root of the neck, producing subcutaneous emphysema

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17
Q

Mediastinal Tumors or Cysts

A

Mediastinal Tumors or Cysts

Because many vital structures are crowded together withinthe mediastinum, their functions can be interfered with by an enlarging tumor or organ.

A tumor of the left lung can rapidly
spread to involve the mediastinal lymph nodes, which on enlargement may compress the left recurrent laryngeal nerve, producing paralysis of the left vocal fold.

An expanding cyst or
tumor can partially occlude the superior vena cava, causing severe congestion of the veins of the upper part of the body.

Other pressure effects can be seen on the sympathetic trunks, phrenic nerves, and sometimes the trachea, main bronchi, and esophagus

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18
Q

Mediastinoscopy

A

Mediastinoscopy is a diagnostic procedure whereby specimens of tracheobronchial lymph nodes are obtained without opening the pleural cavities.

A small incision is made in the
midline in the neck just above the suprasternal notch, and the superior mediastinum is explored down to the region of the bifurcation of the trachea.

The procedure can be used to determine
the diagnosis and degree of spread of carcinoma of the bronchus.

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19
Q
A
FIGURE 3.1 Cross section of the thorax at the level of the eighth thoracic vertebra. Note the arrangement of the pleura and
pleural cavity (space) and the fibrous and the serous pericardia.
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20
Q

The pleurae and lungs lie on either side of the mediastinum within the chest cavity (Fig. 3.3).

Before discussing the
pleurae, it might be helpful to look at the illustrations of
the development of the lungs in Figure 3.4.
Each pleura has two parts:

A
  • a parietal layer
  • a visceral layer
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21
Q

What does the parietal layer lines?

A

a parietal layer, which lines
the thoracic wall,
covers the thoracic surface of thediaphragm
and the lateral aspect of the mediastinum and
extends into the root of the neck to line the undersurface
of the suprapleural membrane at the thoracic outlet

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22
Q

What is the visceral layer?

A

visceral layer, which completely covers the outer surfaces
of the lungs
andextends into the depths of the interlobar
fissures

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23
Q

What is the pulmonary ligament?

A

The two layers of the pleura become continuous with one another by means of a cuff of pleura that surrounds the structures
entering and leaving the lung at the hilum of each lung

(Figs. 3.3, 3.4, and 3.5).

To allow for movement of the pulmonary
vessels and large bronchi during respiration, the
pleural cuff hangs down as a loose fold called the pulmonary ligament

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24
Q

What is pleural cavity?

A

The parietal and visceral layers of pleura are separated
from one another by a slitlike space
, the pleural cavity
(Figs. 3.3 and 3.4).

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25
(Clinicians are increasingly using the term **pleural spac**e instead of the anatomic term pleural cavity. This is probably to **avoid the confusion between the pleural cavity [slitlike]**space and the**larger chest cavity.)**
26
What is the funciton of the pleural flurid?
The pleural cavity normally contains a small amount of tissue fluid, the pleural fluid, which **covers the surfaces of the pleura**as a thin**film and permits the two layers to move on each other with the minimum of friction.**
27
For purposes of description, it is customary to divide the parietal pleura according to the region in which it lies or the surface that it covers. The cervical pleura extends up into the neck, lining the undersurface of the suprapleural \ membrane (see Fig. 2.13). It reaches a level 1 to 1.5 in. (2.5 to 4 cm) above the medial third of the clavicle.
28
What is costal pleura?
The costal pleura **lines the :** * **inner surfaces of the ribs**, * the **costal cartilages,** * the **intercostal spaces**, * the **sides of the vertebral** **bodies**, and * the **back of the sternum** (Fig. 3.3).
29
What is the diaphragmatic pleura?
The diaphragmatic pleura **covers the thoracic surface** of the diaphragm (Figs. 3.3 and 3.5). In quiet respiration, the costal and diaphragmatic pleurae are in apposition to each other below the lower border of the lung. In deep inspiration, the margins of the base of the lung descend, and the costal and diaphragmatic pleurae separate. This lower area of the pleural cavity into which the lung expands on inspiration is referred to as the costodiaphragmatic recess (Figs. 3.4 and 3.5).
30
What is the mediastinal pleura?
The mediastinal pleura **covers and forms the lateral boundary of the mediastinum**(see Figs. 3.3 and 3.5). At the hilum of the lung, it is reflected as a cuff around the vessels and bronchi and here becomes continuous with the visceral pleura. It is thus seen that each lung lies free except at its hilum, where it is attached to the blood vessels and bronchi that constitute the **lung root.** During full inspiration, the lungs expand and fill the pleural cavities. However, during quiet inspiration, the lungs do not fully occupy the pleural cavities at four sites: the right and left costodiaphragmatic recesses and the right and left costomediastinal recesses.
31
What is the costodiaphragmatic recesses?
The costodiaphragmatic recesses are **slitlike spaces between the costal and diaphragmatic parietal pleurae**that are**separated only by a capillary layer of pleural fluid.** During **inspiration**, the lower margins of the lungs **descend into the recesses.** During **expiration**, the lower margins of the lungs **ascend so that the costal and diaphragmatic pleurae come together again.**
32
What is the costomediastinal recesses?
The costomediastinal recesses are situated along the anterior margins of the pleura . They are slitlike spaces between the costal and mediastinal parietal pleurae, which are separated by a capillary layer of pleural fluid. During inspiration and expiration, the anterior borders of the lungs slide in and out of the recesses. The surface markings of the lungs and pleurae were described on pages 54 and 55.
33
Nerve Supply of the Pleura The parietal pleura (Fig. 3.7) is sensitive to pain, temperature, touch, and pressure and is supplied as follows:
■■ The **costal pleura** is segmentally supplied by the **intercostal nerves.** ■■ The **mediastinal pleura** is supplied by the **phrenic nerve.** ■■ The diaphragmatic pleura is supplied over the domes by the phrenic nerve and around the periphery by the lower **six intercostal nerves.**
34
The visceral pleura covering the lungs is insensitive to stretch but is sensitive to common sensations such as pain and touch. It receives an autonomic nerve supply from the pulmonary plexus T or F
False The visceral pleura covering the lungs is **sensitive to stretch** but is **insensitive to common sensations** such as **pain and touch**. It receives an autonomic nerve supply from the pulmonary plexus
35
Describe the Trachea.
The trachea is a **mobile cartilaginous** and **membranous tube** (Fig. 3.9).
36
Where does the trachea begins and ends?
It begins in the **neck as a continuation of** the **larynx at the lower border of the cricoid cartilage** at the **level of the 6th cervical vertebra.** It **descends in the midline of the neck**. In the thorax, the trachea **ends below at the carina**by**dividing into right and left principal (main)**bronchi at the**level of the sternal angle (opposite the disc between the 4th and 5th thoracic vertebrae).** During expiration, the bifurcation rises by about one vertebral level, and during deep inspiration may be lowered as far as the 6th thoracic vertebra
37
How long is the trache in adults?
In adults, the trachea is about **4 1/2 in. (11.25 cm)** long and **1 in. (2.5 cm) in diamete**r (Fig. 3.9).
38
What keeps the fibroelastic tube of the trachea?
The fibroelastic tube is **kept patent by the presence of U-shaped bars** **(rings) of hyaline cartilage e**mbedded in its wall.
39
What connects the posterior free ends of the cartilage of trachea?
The posterior free ends of the cartilage are connected by smooth muscle, the trachealis muscle.
40
The relations of the trachea in the neck are described on page 651. The relations of the trachea in the superior mediastinum of the thorax are as follows:
■■ Anteriorly: * **The sternum,** * **the thymus,** * **the left brachiocephalic vein,** * **the origins of the brachiocephalic and** * **left common carotid arteries, and** * **the arch of the aorta** (Figs. 3.6A, 3.9, and 3.30) ■■ Posteriorly: * The esophagus and the left recurrent laryngeal nerve (Fig. 3.6A) ■■ Right side: * The azygos vein, * the right vagus nerve, and * the pleura (Figs. 3.6, 3.15A, and 3.16) ■■ 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 (Figs. 3.6, 3.15B, and 3.17)
41
Blood Supply of the Trachea
The **upper two thirds** are supplied by the **inferior thyroid arteries** and the **lower third is supplied by the bronchial arteries** **T:​UILB**
42
Lymph Drainage of the Trachea
The lymph drains into the **pretracheal and paratracheal** **lymph nodes and the deep cervical nodes**
43
Nerve Supply of the Trachea
The sensory nerve supply is from the vagi and the recurrent laryngeal nerves. Sympathetic nerves supply the trachealis muscle.
44
The pleural space normally contains \_\_\_\_\_\_\_\_\_of clear fluid, which lubricates the apposing surfaces of the visceral and parietal pleurae during respiratory movements
Pleural Fluid The pleural space normally contains **5 to 10 mL** of clear fluid, which **lubricates the apposing surfaces of the visceral and parietal pleurae during respiratory movements**.
45
How is the pleural fluid form?
The formation of the fluid results from hydrostatic and osmotic pressures. Since the hydrostatic pressures are greater in the capillaries of the parietal pleura than in the capillaries of the visceral pleura (pulmonary circulation), the pleural fluid is normally absorbed into the capillaries of the visceral pleura.
46
What is pleural effusion?
Any condition that **increases the production of the fluid** (e.g., inflammation, malignancy, congestive heart disease) or impairs the drainage of the fluid (e.g., collapsed lung) results in the abnormal accumulation of fluid, called a pleural effusion.
47
What is the amount of fluid in costrodiaphragmatic recess in an adult that is sufficient to enable its clinical detection?
The presence of **300 mL** of fluid in the costodiaphragmatic recess in an adult is sufficient to enable its clinical detection.
48
What are the clinical signs of pleural effusion?
The clinical signs include **decreased lung expansion on the side of the effusion,** with **decreased breath sounds** and **dullness on percussion over the** **effusion** (Fig. 3.8).
49
What is Pleurisy?
Pleurisy Inflammation of the pleura (pleuritis or pleurisy), secondary to inflammation of the lung (e.g., pneumonia), results in the pleural surfaces **becoming 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 pleura, forming **pleural adhesions.**
50
What is artificial pneumothorax?
As the result of disease or injury (stab or gunshot wounds), air can enter the pleural cavity from the lungs or through the chest wall (pneumothorax). In the old treatment of tuberculosis, air was purposely injected into the pleural cavity to collapse and rest the lung. **This was known as artificial pneumothorax.**
51
What is spontaneous pneumothorax?
A spontaneous 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.**
52
What is open pneumothorax?
Stab wounds of the thoracic wall may pierce the parietal pleura so that the pleural cavity is open to the outside air. This condition is called **open pneumothorax.** Each time the patient inspires, it is possible to hear air under atmospheric pressure being sucked into the pleural cavity. Sometimes the clothing and the layers of the thoracic wall combine to form a valve so that air enters on inspiration but cannot exit through the wound. In these circumstances, the air pressure builds up 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. This dangerous condition is called a tension pneumothorax.
53
What is tension pneumothorax?
In these circumstances, the air pressure builds up 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**. This dangerous condition is called a **tension pneumothorax.**
54
What is hydropneumothorax?
Air in the **pleural cavity associated with serous fluid** is known as hydropneumothorax.
55
What is pyopneumothorax?
Air in the pleural cavity associated with pus as pyopneumothorax.
56
What is hemopneumothorax?
Air in the pleural cavity associated with blood as hemopneumothorax.
57
What is empyema?
A collection of pus (without air) in the pleural cavity is called an empyema.
58
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.
59
In hemopneumothorax, blood enters the pleural cavity. It can be caused by stab or bullet wounds to the chest wall, resulting in bleeding from blood vessels in the chest wall, from vessels in the chest cavity, or from a lacerated lung.
60
Where does the trachea bifurcates?
The trachea bifurcates behind the arch of the aorta into the **right and left principal (primary or main) bronchi** (Figs. 3.9, 3.18, and 3.19).
61
What is the division of bronchi?
The bronchi divide **dichotomously,** **giving rise to several million terminal bronchioles** that **terminate in one or more respiratory bronchioles.** Each respiratory bronchiole **divides into 2 to 11 alveolar** **ducts that enter the alveolar sacs.** The alveoli arise from the walls of the sacs as diverticula (see page 71
62
Describe the right principal (main) bronchus.
The **right principal (main) bronchus** (Fig. 3.11) is **wider, shorter, and more vertical than the left**(Figs. 3.9, 3.18, and 3.19) and is **about 1 in. (2.5 cm) long**.
63
Before entering the hilum of the right lung, the principal bronchus gives off the \_\_\_\_\_\_\_\_\_\_\_\_\_\_
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 and an inferior lobar bronchus.**
64
Describe the left principal bronchus.
The left principal (main) bronchus is narrower, longer, and more horizontal than the right and is about 2 in. (5 cm) long. It passes to the left below the arch of the aorta and in front of the esophagus. On entering the hilum of the left lung, the principal bronchus divides into a **superior** **and an inferior lobar bronchus.**
65
On entering the hilum of the **left lung,** the p**rincipal bronchus** divides into a :
* superior and * an inferior lobar bronchus.
66
On entering the hilum, the right principal bronchus will divide into:
a middle and an inferior lobar bronchus.
67
What is Tracheitis or Bronchitis?
Tracheitis or Bronchitis The **mucosa lining the trachea** is **innervated by the recurrent laryngeal nerve** and, in the region of its bifurcation, by the pulmonary plexus. A tracheitis or bronchitis **gives rise to a raw, burning sensation felt deep to the sternum instead of actual pain.** Many thoracic and abdominal viscera, when diseased, give rise to discomfort that is felt in the midline (see page 224). It seems that organs possessing a sensory innervation that is not under normal conditions directly relayed to consciousness display this phenomenon. The afferent fibers from these organs traveling to the central nervous system accompany autonomic nerves.
68
Where does Inhaled Foreign Bodies mostly dislodged and why?
Inhaled Foreign Bodies Inhalation of foreign bodies into the lower respiratory tract is common, especially in children. Pins, screws, nuts, bolts, peanuts, 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 continuation of the trachea (Figs. 3.18 and 3.19), foreign bodies tend to enter the right instead of the left bronchus. From there, they usually pass into the middle or lower lobe bronchi.
69
What is Bronchoscopy?
Bronchoscopy Bronchoscopy enables a physician to examine the interior of the trachea; its bifurcation, called the **carina**; and the main bronchi (Figs. 3.12 and 3.13). With experience, it i**s 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 possible to obtain biopsy specimens of mucous membrane and to remove inhaled foreign bodies (even an open safety pin). Lodgment of a foreign body in the larynx or edema of the mucous membrane of the larynx secondary to infection or trauma may require immediate relief to prevent asphyxiation. A method commonly used to **relieve complete obstruction is tracheostom**y (see page 654
70
What is carina?
bifurcation of the trachea, called the carina
71
During life, the right and left lungs are **soft and spongy and very elastic.** * *If the thoracic cavity were opened,** the * *lungs would immediately shrink to one third or less in volume. **
72
What is the appearance of lungs in childs?
In the child, they are pink.
73
What is the appearance of the lungs when we age?
, but with age, **they become dark and mottled**because of the inhalation of dust particles that become trapped in the phagocytes of the lung. This is especially well seen in city dwellers and coal miners. The lungs are situated so that one lies on each side of the mediastinum. They are therefore separated from each other by the heart and great vessels and other structures in the mediastinum.
74
What is the shape of the lungs?
Each lung is conical, covered with visceral pleura, and suspended free in its own pleural cavity, being attached to the mediastinum only by its root (Fig. 3.4).
75
What is the appearance of the apex of the lungs?
Each lung has a **blunt apex**, which **projects upward into the neck for about 1 in. (2.5 cm)** above the clavicle;
76
What is the appearance of the base of the lungs?
a concave base that sits on the diaphragm;
77
What is the shape of the costal surface of the lungs?
a **convex costal surface,** which **corresponds to the concave chest wall**
78
What is the shape of themediastinal surface of the lungs?
concave mediastinal surface, which is molded to the pericardium and other mediastinal structures (Figs. 3.20 and 3.21). At about the middle of this surface is the hilum, a depression in which the bronchi, vessels, and nerves that form the root enter and leave the lung.
79
Where can you find the cardiac notch?
The anterior border is thin and overlaps the heart; it is here on the left lung that the cardiac notch is found. The posterior border is thick and lies beside the vertebral column
80
Which is larger, right or left lung?
The **right lung is slightly larger than the left**
81
The right lobe of the lung is divided by what fissures?
and is divided by the **oblique and horizontal fissures into three lobes:** * the upper, * middle, and * lower lobes (Fig. 3.20).
82
Where does the oblique fissure runs?
The oblique fissure **runs from the inferior border upward and backward across the medial and costal surfaces until it cuts the posterior border about 2.5 in**. (6.25 cm) below the apex.
83
Where does the horizontal fissure runs?
The horizontal fissure runs horizontally across the costal surface at the level of the 4th costal cartilage to meet the oblique fissure in the midaxillary line.
84
Describe the middle lobe of the right lung?
The middle lobe is thus a small triangular lobe bounded by the horizontal and oblique fissures.
85
The left lung is divided by a \_\_\_\_\_\_\_\_\_\_\_\_\_
similar oblique fissure into two lobes: the upper and lower lobes (Fig. 3.21). * *There is no** * *horizontal fissure in the left lung.**
86
What are the bronchopulmonary segments?
The bronchopulmonary segments are the **anatomic, functional, and surgical units of the lung**s. **Each segmental bronchus passes to a structurally** and **functionally independent unit of a lung lobe** called a bronchopulmonary segment, which is surrounded by connective tissue (Fig. 3.22).
87
What is segmental (tertiary) bronchi ?
**Each lobar (secondary) bronchus,** which passes to a lobe of the lung, gives off branches called **segmental (tertiary) bronchi** (Fig. 3.18). ``` Each segmental bronchus passes to a **structurally and functionally independent unit of a lung lobe called a bronchopulmonary segment**, which is surrounded by connective tissue (Fig. 3.22). ``` The segmental bronchus 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 and autonomic nerve supply.
88
On entering a bronchopulmonary segment, each segmental bronchus divides repeatedly (Fig. 3.22). As the bronchi become smaller, the **U-shaped bars of cartilage found** in the trachea are **gradually replaced by irregular plates of cartilage,** which become smaller and fewer in number.
89
What are bronchioles?
The **smallest bronchi** divide and **give rise to bronchioles, whichare \<1 mm in diameter** (Fig. 3.22). Bronchioles **possess no cartilage in their walls and are lined with columnar ciliated epithelium.** The **submucosa possesses a complete layer of** **circularly arranged smooth muscle fibers.**
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What are terminal bronchioleS?
The bronchioles then divide and give rise to terminal bronchioles (Fig. 3.22), which show delicate **outpouchings rom their walls.**
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What are respiratory bronchioles?
Gaseous exchange between blood and air takes place in the walls of these outpouchings, which explains the name **respiratory bronchiole**. The diameter of a respiratory bronchiole is abou**t 0.5 mm**.
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What are alveolar sacs?
The respiratory bronchioles end by branching into alveolar ducts, which lead into tubular passages with numerous thin-walled outpouchings called **alveolar sacs**
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Alveolar sacs consist of?
. The alveolar sacs consist of **several alveoli opening into a single chambe**r (Figs. 3.22 and 3.23).
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Where does gaseous exchange happens?
Each alveolus is surrounded by a rich network of blood capillaries. Gaseous exchange takes place between the air in the alveolar lumen through the alveolar wall into the blood within the surrounding capillaries Gaseous exchange between blood and 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 outpouchings called alveolar sacs.
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The main characteristics of a bronchopulmonary segment may be summarized as follows:
■■ It is a **subdivision of a lung lobe.** ■■ It is **pyramid shaped**, with its apex toward the lung root. ■■ It is **surrounded by connective tissue.** ■■ It has a **segmental bronchus, a segmental artery, lymph vessels, and autonomic nerves**. ■■ The s**egmental vein lies in the connective tissue between adjacent bronchopulmonary segments**. ■■ Because it is a **structural unit, a diseased segment can be removed surgically**
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The main bronchopulmonary segments (Figs. 3.24 and 3.25) are as follows
■■ Right lung * **Superior lobe**: Apical, posterior, anterior * **Middle lobe**: Lateral, medial * **Inferior lobe**: Superior (apical), medial basal, anterior basal, lateral basal, posterior basal
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The main bronchopulmonary segments (Figs. 3.24 and 3.25) are as follows
■■ Left lung * **Superior lobe**: Apical, posterior, anterior, superior lingular, inferior lingular * **Inferior lobe**: Superior (apical), medial basal, anterior basal, lateral basal, posterior basal
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Although the general arrangement of the bronchopulmonary segments is of clinical importance, it is unnecessary to memorize the details unless one intends to specialize in **pulmonary medicine or surgery**
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Describe the root of the lung.
The root of the lung is formed of structures that are entering or leaving the lung. It is made up of the bronchi, pulmonary artery and veins, lymph vessels, bronchial vessels, and nerves. The root is surrounded by a tubular sheath of pleura, which joins the mediastinal parietal pleura to the visceral pleura covering the lungs (Figs. 3.5, 3.15, 3.16, and 3.17).
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What makes up the root of the lung?
It is made up of the : * bronchi, * pulmonary artery and veins, * lymph vessels, * bronchial vessels, and nerves.
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Blood Supply of the Lungs What does bronchial artery supply?
Blood Supply of the Lungs The **bronchi, the connective tissue of the lung**, and the **visceral pleura** receive their blood supply from the bronchial arteries, which are branches of the descending aorta.
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Bronchial Artery is a brach of:
Descending aorta
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Where does bronchial vein drain?
``` The bronchial veins (which communicate with the pulmonaryveins) drain into the azygos and hemiazygos veins. ```
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How does the blood exchange in alveoli happens?
The alveoli receive deoxygenated blood from the **terminal branches of the pulmonary arteries.** The oxygenated blood leaving the alveolar capillaries drains into the tributaries of the pulmonary veins, which follow the intersegmental connective tissue septa to the lung root. **Two pulmonary veins** leave each lung root (Fig. 3.15) to empty into the left atrium of the heart.
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How many pulmonary veins leave each lung root?
Two pulmonary veins leave each lung root (Fig. 3.15) to empty into the left atrium of the heart.
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The lymph vessels originate in\_\_\_\_\_\_\_\_\_\_\_\_\_(Fig. 3.26); they are not present in the alveolar walls.
superficial and deep plexuses The **superficial (subpleural) plexus** lies beneath the visceral pleura and drains over the surface of the lung toward the hilum, where the lymph vessels enter the **bronchopulmonary nodes.** The deep plexus travels along the bronchi and pulmonary vessels toward the hilum of the lung, passing through pulmonary nodes located within the lung substance; the lymph then enters the **bronchopulmonary nodes** in the hilum of the lung. All the lymph from the lung leaves the hilum and drains into the tracheobronchial nodes and then into the bronchomediastinal lymph trunks.
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Nerve Supply of the Lungs
At the root of each lung is a pulmonary plexus composed of efferent and afferent autonomic nerve fibers. The plexus is formed from branches of the sympathetic trunk and receives parasympathetic fibers from the vagus nerve. The **sympathetic efferent** fibers produce bronchodilatation and vasoconstriction. The **parasympathetic efferent** fibers produce bronchoconstriction, vasodilatation, and increased glandular secretion Afferent impulses derived from the bronchial mucous membrane and from stretch receptors in the alveolar walls pass to the central nervous system in both sympathetic and parasympathetic nerves.
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Respiration consists of two phases—
**inspiration and expiration—** which are accomplished by the alternate increase and decrease of the capacity of the thoracic cavity. The rate varies between **16 and 20 per minute in normal resting patients** and is **faster in children** and **slower in the elderly.**
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Quiet Inspiration Compare the thoracic cavity to a box with a single entrance at the top, which is a tube called the trachea (Fig. 3.29). The capacity of the box can be increased by elongating all its diameters, and this results in air under atmospheric pressure entering the box through the tube. Consider now the three diameters of the thoracic cavity and how they may be increased (Fig. 3.29).
* Vertical Diameter * Anteroposterior Diameter * Transverse Diameter
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Describe the Vertical Diameter during Quiet Inspiration.
Vertical Diameter Theoretically, the roof could be raised and the floor lowered. The roof is formed by the **suprapleural membrane and is fixed.** Conversely, the floor is formed by the **mobile diaphragm.** When the diaphragm contracts, the domes become flattened and the level of the diaphragm is lowered
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Describe the Anteroposterior Diameter during quiet inspiration.
Anteroposterior Diameter If the downward-sloping ribs were raised at their sternal ends, the anteroposterior diameter of the thoracic cavity would be increased and the lower end of the sternum would be thrust forward (Fig. 3.29). This can be brought about by **fixing the 1st rib by the contraction of the scaleni muscles of the neck and contracting the intercostal muscles** (Fig. 3.10). By this means, all the ribs are drawn together and raised toward the first rib.
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Descirbe the tranvers diameter in Quiet inspiration.
Transverse Diameter The ribs articulate in front with the sternum via their **costal cartilages and behind with the** **vertebral column.** Because the ribs curve downward as well as forward around the chest wall, they resemble bucket handles (see Fig. 3.29). It therefore follows that **if the ribs are** **raised (like bucket handles),** the **transverse diameter of the** **thoracic cavity will be increased.** As described previously, **this can be accomplished by fixing the 1st rib** and raising the other ribs to it by contracting the intercostal muscles (Fig. 3.10). An additional factor that must not be overlooked is the **effect of the descent of the diaphragm** on the **abdominal viscera and the tone of the muscles of the anterior abdominal wall.** As the diaphragm descends on inspiration, **intra-abdominal pressure rises.** Thi**s rise in pressure is accommodated by the reciprocal relaxation of the abdominal wall musculature**. However, a point is reached when no further abdominal relaxation is possible, and the liver and other upper abdominal viscera act as a platform that resists further diaphragmatic descent. ***On further contraction, the diaphragm will now have its central tendon supported from below, and its shortening muscle fibers will assist the intercostal muscles in raising the lower ribs (Fig. 3.10). Apart from the diaphragm and the intercostals, other less important muscles also contract on inspiration and assist in elevating the ribs, namely, the levatores costarum muscles and the serratus posterior superior muscles***
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What is forced inspiration?
In deep forced inspiration, a **maximum increase** in the **capacity of the thoracic cavity occurs.** Every muscle that can raise the ribs is brought into action, including the **scalenus anterior and medius and the sternocleidomastoid.** In **respiratory distress, the action of all the muscles already engaged becomes more violen**t, and the**scapulae are fixed by the trapezius, levator scapulae,** and rhomboid muscles, enabling the serratus anterior and the pectoralis minor to pull up the ribs. If the upper limbs can be supported by grasping a chair back or table, the sternal origin of the pectoralis major muscles can also assist the process
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What are the lung changes during inspiration?
In inspiration, the **root of the lung descends and the level ofthe bifurcation of the trachea may be lowered by as much as two vertebrae.** The **bronchi elongate and dilate and the alveolar capillaries dilate**, thus assisting the pulmonary circulation. Air is drawn into the bronchial tree as the result of the positive atmospheric pressure exerted through the upper part of the respiratory tract and the negative pressure on the outer surface of the lungs brought about by the increased capacity of the thoracic cavity. With **expansion of the lungs, the elastic tissue in the bronchial walls and connective tissue are stretched.** As the **diaphragm descends**, the **costodiaphragmatic recess of the pleural cavity opens,** and **the expanding sharp lower edges of the lungs descend to a lower level**
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Discuss Quiet expiration?
Quiet expiration is **largely a passive phenomenon** and is **brought about by the elastic recoil of the lungs,** the **relaxation of the intercostal muscles and diaphragm,** and an **increase in tone of the muscles of the anterior abdominal wall**, which forces the relaxing diaphragm upward. The **serratus posterior inferior muscles** play a minor role in pulling down the lower ribs.
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Discuss force expiration.
Forced expiration is an **active process** brought about by the **forcible contractio**n of the **musculature of the anterior abdominal wall.** The **quadratus lumborum also contracts** and **pulls down the 12th rib**. It is conceivable that under these circumstances s**ome of the intercostal muscles may contract, pull the ribs together, and depress them** to the lowered 12th rib (Fig. 3.10). The **serratus posterior inferio**r and the**latissimus dorsi muscles** may also play a minor role
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Lung Changes on Expiration
In expiration, the **roots of the lungs ascend along with the bifurcation of the trachea.** The **bronchi shorten and contract.** The **elastic tissue of the lungs recoils**, and the **lungs become reduced in size**. With the upward movement of the **diaphragm, increasing areas of the diaphragmatic and costal parietal pleura come into apposition**, and the costodiaphragmatic recess becomes reduced in size. The lower margins of the lungs shrink and rise to a higher level
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Types of Respiration
1. abdominal type of respiration. 2. thoracic type of respiration
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What is abdominal type of respiration?
In babies and young children, the ribs are nearly horizontal. Thus, babies have to rely mainly on the descent of the diaphragm to increase their thoracic capacity on inspiration. Because this is **accompanied by a marked inward and outward excursion of the anterior abdominal wall,** which is easily seen, r**espiration at this age is referred to as the abdominal type of respiration**
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What is thoracic type of respiration?
After the second year of life, the **ribs become more oblique**, and the**adult form of respiration** is established. In the adult, a **sexual difbference exists in the type of respiratory movements**. The female tends to rely mainly on the **movements of the ribs rather than on the descent of the diaphragm on inspiration**. This is referred to as the **thoracic type of respiration.** The male uses both the thoracic and abdominal forms of respiration, but mainly the abdominal form.
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In the adult, a **sexual difbference exists in the type of respiratory movements.** What type of breathing does the female uses?
The **female tends to rely mainly** on the **movements of the rib**s rather than on the descent of the diaphragm on inspiration. This is referred to as the **thoracic type of respiration.**
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In the adult, a sexual difbference exists in the type of respiratory movements. What type of breathing does the male uses?
The male uses both the thoracic and abdominal forms of respiration, but mainly the abdominal form.
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Physical Examination of the Lungs For physical examination of the patient, it is helpful to remember that the **upper lobes of the lungs are most easily examined from the front of the chest**and the**lower lobes from the back.** In the axillae, areas of all lobes can be examined.
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Trauma to the Lungs
A physician must always remember that the **apex of the lung projects up into the neck (1 in. [2.5 cm] above the clavicle**) and can be damaged by stab or bullet wounds in this area. Although the lungs are well protected by the bony thoracic cage, a splinter from a fractured rib can nevertheless penetrate the lung, and air can escape into the pleural cavity, causing a pneumothorax and collapse of the lung. It can also find its way into the lung connective tissue. From there, the air moves under the visceral pleura until it reaches the lung root. It then passes into the mediastinum and up to the neck. Here, it may distend the subcutaneous tissue, a condition known as **subcutaneous emphysema.** The changes in the position of the thoracic and upper abdominal viscera and the level of the diaphragm during different phases of respiration relative to the chest wall are of considerable clinical importance. A penetrating wound in the lower part of the chest may or may not damage abdominal viscera, depending on the phase of respiration at the time of injury.
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Lung tissue and the visceral pleura are devoid of pain-sensitive nerve endings, so that pain in the chest is always the result of conditions affecting the surrounding structures. T or F
True Lung tissue and the visceral pleura are devoid of pain-sensitive nerve endings, so that pain in the chest is always the result of conditions affecting the surrounding structures. In tuberculosis or pneumonia, for example, pain may never be experienced.
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When does a lung disease becomes a prominent feature of pain?
Once lung disease **crosses the visceral pleura** and the **pleural cavity to involve the parietal pleura, pain becomes a prominent feature**. Lobar pneumonia with pleurisy, for example, produces a severe tearing pain, accentuated by inspiring deeply or coughing. Because the lower part of the costal parietal pleura receives its sensory innervation from the lower five intercostal nerves, which also innervate the skin of the anterior abdominal wall, pleurisy in this area commonly produces pain that is referred to the abdomen. ***This has sometimes resulted in a mistaken diagnosis of an acute abdominal lesion**.*
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When does a lung disease can produce a referred pain on the shoulders?
In a similar manner, **pleurisy of the central part** of the **diaphragmatic pleura**, which **receives sensory innervation from the phrenic nerve (C3, 4, and 5)**, can lead to **referred pain over the shoulder** because the skin of this region is supplied by the supraclavicular nerves (C3 and 4).
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Surgical Access to the Lungs can done by:
Surgical access to the lung or mediastinum is commonly undertakenthrough an intercostal space (see page 46). Special rib retractors that allow the ribs to be widely separated are used. The costal cartilages are sufficiently elastic to permit considerable bending. Good exposure of the lungs is obtained by this method.
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When do you do **Segmental Resection of the Lung?**
Segmental Resection of the Lung A localized chronic lesion such as that of tuberculosis or a benign neoplasm may require surgical removal. If it is restricted to a bronchopulmonary segment, it is possible carefully to dissect out a particular segment and remove it, leaving the surrounding lung intact. Segmental resection requires that the radiologist and thoracic surgeon have a sound knowledge of the bronchopulmonary segments and that they cooperate fully to localize the lesion accurately before operation.
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Bronchogenic Carcinoma
Bronchogenic carcinoma accounts for about one third of all cancer deaths in men and is becoming increasingly common in women. It commences in most patients in the mucous membrane lining the larger bronchi and is therefore situated close to the hilum of the lung. The neoplasm rapidly spreads to the tracheobronchial and bronchomediastinal nodes and may involve the recurrent laryngeal nerves, leading to hoarseness of the voice. Lymphatic spread via the bronchomediastinal trunks may result in early involvement in the lower deep cervical nodes just above the level of the clavicle. Hematogenous spread to bones and the brain commonly occurs.
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Conditions That Decrease Respiratory Efficiency
* Constriction of the Bronchi (Bronchial Asthma) * Loss of Lung Elasticity * Loss of Lung Distensibility
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What disease that cause **Loss of Lung Distensibility?**
Many diseases of the lungs, such as **emphysema and pulmonary fibrosis**, destroy the elasticity of the lungs, and thus the lungs are unable to recoil adequately, causing incomplete expiration. The **respiratory muscles in these patients have to assist in expiration**, **which no longer is a passive phenomenon.**
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What diseases cause Loss of Lung Distensibility?
Loss of Lung Distensibility Diseases such as **silicosis, asbestosis, cancer, and pneumonia** interfere with the process of expanding the lung in inspiration. A decrease in the compliance of the lungs and the chest wall then occurs, and a greater effort has to be undertaken by the inspiratory muscles to inflate the lungs.
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What is Postural Drainage?
Postural Drainage Excessive accumulation of bronchial secretions in a lobe or segment of a lung can seriously interfere with the normal flow of air into the alveoli. Furthermore, the stagnation of such secretions is often quickly followed by infection. To aid in the normal drainage of a **bronchial segment, a physiotherapist often alters the position of the patient so that gravity assists in the process of drainage.** **Sound knowledge of the bronchial tre**e is necessary to determine the optimum position of the patient for good postural drainage.
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Development of the Lungs and Pleura
A longitudinal groove develops in the entodermal lining of the floor of the pharynx. This groove is known as the **laryngotracheal** groove. The **lining of the larynx, trachea, and bronchi and the epithelium**of the alveoli develop from this groove. The margins of the groove fuse and form the laryngotracheal tube (Fig. 3.27). The fusion process starts distally so that the lumen becomes separated from the developing esophagus. Just behind the developing tongue, a small opening persists that will become the permanent opening into the larynx. The laryngotracheal tube grows caudally into the splanchnic mesoderm and will eventually lie anterior to the esophagus. The tube divides distally into the surrounding the tube, and the upper part of the tube becomes the larynx, whereas the lower part becomes the trachea. Each lung bud consists of an entodermal tube surrounded by splanchnic mesoderm; from this, all the tissues of the corresponding lung are derived. Each bud grows laterally and projects into the pleural part of the embryonic coelom (Fig. 3.27). The lung bud divides into three lobes and then into two, corresponding to the number of main bronchi and lobes found in the fully developed lung. Each main bronchus then divides repeatedly in a dichotomous manner, until eventually the terminal bronchioles and alveoli are formed. The division of the terminal bronchioles, with the formation of additional bronchioles and alveoli, continues for some time after birth. Each lung will receive a covering of visceral pleura derived from the splanchnic mesoderm. The parietal pleura will be formed from somatic mesoderm. By the seventh month, the capillary loops connected with the pulmonary circulation have become sufficiently well developed to support life, should premature birth take place. With the onset of respiration at birth, the lungs expand and the alveoli become dilated. However, it is only after 3 or 4 days of postnatal life that the alveoli in the periphery of each lung become fully expanded.
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Esophageal Atresia and Tracheoesophageal Fistula
If the margins of the laryngotracheal groove fail to fuse adequately, an abnormal opening may be left between the laryngotracheal tube and the esophagus. If the tracheoesophageal septum formed by the fusion of the margins of the laryngotracheal groove should be deviated posteriorly, the lumen of the esophagus would be much reduced in diameter. The different types of atresia, with and without fistula, are shown in Figure 3.28. Obstruction of the esophagus prevents the child from swallowing saliva and milk, and this leads to aspiration into the larynx and trachea, which usually results in pneumonia. With early diagnosis, it is often possible to correct this serious anomaly surgically
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