CHAPTER 8: The Thorax and Lungs


Anatomy and Physiology

Study the anatomy of the chest wall, identifying the structures illustrated (Fig. 8-1). Note that the number of the intercostal space between two ribs is the same number as the rib above it.

FIGURE 8-1 Chest wall anatomy.

Chest wall anatomy.

Locating Findings on the Chest

Describe chest findings in two dimensions: along the vertical axis and around the circumference of the chest.

Vertical Axis

To locate findings in the thorax, learn to number the ribs and intercostal spaces (Fig. 8-2). Place your finger in the hollow curve of the suprasternal notch, then move it down approximately 5 cm to the horizontal bony ridge where the manubrium joins the body of the sternum, called the sternal angle or the angle of Louis. Directly adjacent to the sternal angle is the 2nd rib and its costal cartilage.

From here, using two fingers, “walk down” the interspaces on an oblique line, illustrated by the red numbers below. (Note that the ribs at the lower edge of the sternum may be too close together to count correctly.) To count the intercostal spaces in a woman, displace the breast laterally or palpate more medially. Avoid pressing too hard on the tender breast tissue.

FIGURE 8-2 Anterior ribs and intercostal spaces.

Anterior ribs and intercostal spaces.

Note special landmarks:

  • 2nd intercostal space for needle insertion for tension pneumothorax.
  • 4th intercostal space for chest tube insertion.
  • T4 for the lower margin of an endotracheal tube on a chest x-ray.

Neurovascular structures run along the inferior margin of each rib, so needles and tubes should be placed just at the superior rib margins.

Note that the costal cartilages of the first seven ribs articulate with the sternum; the cartilages of the 8th, 9th, and 10th ribs articulate with the costal cartilages just above them. The 11th and 12th ribs, the “floating ribs,” have no anterior attachments. The cartilaginous tip of the 11th rib usually can be felt laterally, and the 12th rib may be felt posteriorly. When palpated, costal cartilages and ribs feel identical.

Posteriorly, the 12th rib is a starting point for counting ribs and intercostal spaces and provides an alternative to the anterior approach (Fig. 8-3). With the fingers of one hand, press in and up against the lower border of the 12th rib; then “walk up” the intercostal spaces, numbered in red below, or follow a more oblique line up and around to the front of the chest.

FIGURE 8-3 Posterior ribs and intercostal spaces.

Posterior ribs and intercostal spaces.

Note the T7–T8 intercostal space as a landmark for thoracentesis with needle insertion immediately superior to the 8th rib.

The inferior tip of the scapula is another useful bony landmark; it usually lies at the level of the 7th rib or interspace.

The spinous processes of the vertebrae are also useful landmarks. When the neck is flexed forward, the most protruding process is usually the vertebra of C7. If two processes are equally prominent, they are C7 and T1. You can often palpate and count the processes below them, especially when the spine is flexed.

Circumference of the Chest

Visualize a series of vertical lines as shown in Figures 8-4 through 8-6. The midsternal and vertebral lines are easily demarcated and reproducible; the others are visualized. The midclavicular line drops vertically from the midpoint of the clavicle. To find it, accurately identify both ends of the clavicle (see p. 646).

FIGURE 8-4 Midsternal, midclavicular, and anterior axillary lines.

Midsternal, midclavicular, and anterior axillary lines.

FIGURE 8-5 Anterior, midaxillary, and posterior lines.

Anterior, midaxillary, and posterior lines.

FIGURE 8-6 Vertebral and scapular lines.

Vertebral and scapular lines.

The anterior and posterior axillary lines drop vertically from the anterior and posterior axillary folds, the muscle masses that border the axilla. The midaxillary line drops from the apex of the axilla.

Posteriorly, the vertebral line overlies the spinous processes of the vertebrae. The scapular line drops from the inferior angle of the scapula.

Lungs, Fissures, and Lobes

Picture the lungs and their fissures and lobes on the chest wall. Anteriorly, the apex of each lung rises approximately 2 to 4 cm above the inner third of the clavicle (Fig. 8-7). The lower border of the lung crosses the 6th rib at the midclavicular line and the 8th rib at the midaxillary line. Posteriorly, the lower border of the lung lies at about the level of the T10 spinous process (Fig. 8-8). On inspiration, it descends in the chest cavity during contraction and descent of the diaphragm.

FIGURE 8-7 The anterior lungs.

The anterior lungs.

FIGURE 8-8 The posterior lungs.

The posterior lungs.

Each lung is divided roughly in half by an oblique (major) fissure. This fissure may be approximated by a string that runs from the T3 spinous process obliquely down and around the chest to the 6th rib at the midclavicular line (Fig. 8-9). The right lung is further divided by the horizontal (minor) fissure. Anteriorly, this fissure runs close to the 4th rib and meets the oblique fissure in the midaxillary line near the 5th rib. The right lung is thus divided into upper, middle, and lower lobes (RUL, RML, and RLL). The left lung has only two lobes, upper and lower (LUL, LLL) (Fig. 8-10). Each lung receives deoxygenated blood from its pulmonary artery. Oxygenated blood returns from each lung to the left atrium via the pulmonary veins.

FIGURE 8-9 Right lung lobes and fissures.

Right lung lobes and fissures.

FIGURE 8-10 Left lung lobes and fissures.

Left lung lobes and fissures.

Locations on the Chest

Learn the general anatomical terms used to locate chest findings.

Anatomic Descriptors of the Chest

Supraclavicular—above the clavicles

Infraclavicular—below the clavicles

Interscapular—between the scapulae

Infrascapular—below the scapulae

Bases of the lungs—the lowermost portions

Upper, middle, and lower lung fields

Usually, physical examination findings correlate with the underlying lobes. Signs in the right upper lung field, for example, almost certainly originate in the right upper lobe. However, signs found laterally in the right middle lung field could come from any of the three different lobes.

The Trachea and Major Bronchi (the Tracheobronchial Tree)

Breath sounds over the trachea and bronchi have a harsher quality than those over the denser lung parenchyma. Learn the locations of these structures. The trachea bifurcates into its mainstem bronchi at the levels of the sternal angle anteriorly and the T4 spinous process posteriorly (Figs. 8-11 and 8-12). The right main bronchus is wider, shorter, and more vertical than the left main bronchus and directly enters the hilum of the lung.

The left main bronchus extends inferolaterally from below the aortic arch and anterior to the esophagus and thoracic aorta and then enters the lung hilum. Each main bronchus then divides into lobar then into segmental bronchi and bronchioles, terminating in the sac-like pulmonary alveoli, where gas exchange occurs.

FIGURE 8-11 Trachea and mainstem bronchi, anterior view.

Trachea and mainstem bronchi, anterior view.

FIGURE 8-12 Trachea and mainstem bronchi, posterior view.

Trachea and mainstem bronchi, posterior view.

Aspiration pneumonia is more common in the right middle and lower lobe because the right main bronchus is more vertical.

The Pleurae

Two continuous pleural surfaces, or serous membranes, separate the lungs from the chest wall. The visceral pleura covers the outer surface of the lungs. The parietal pleura lines the pleural cavity along the inner rib cage and the upper surface of the diaphragm. Between the visceral and parietal pleura is the pleural space, containing serous pleural fluid.

The surface tension of the pleural fluid keeps the lung in contact with the thoracic wall, allowing the lung to expand and contract during respiration. The visceral pleura lacks sensory nerves, but the parietal pleura is richly innervated by the intercostal and phrenic nerves.

Accumulations of pleural fluid, or pleural effusions, may be transudates, seen in heart failure, cirrhosis, and nephrotic syndrome, or exudates, seen in numerous conditions including pneumonia, malignancy, pulmonary embolism, tuberculosis, and pancreatitis

Irritation of the parietal pleura produces pleuritic pain with deep inspiration in viral pleurisy, pneumonia, pulmonary embolism, pericarditis, and collagen vascular diseases.


Breathing is primarily automatic, controlled by respiratory centers in the brainstem that generate the neuronal drive for the muscles of respiration. The principal muscle of inspiration is the diaphragm. During inspiration, the diaphragm contracts, descends in the chest, and expands the thoracic cavity, compressing the abdominal contents and pushing out the abdominal wall.

The muscles in the rib cage also expand the thorax, especially the scalenes, which run from the cervical vertebrae to the first two ribs, and the parasternal intercostal muscles, or parasternals, which cross obliquely from the sternum to the ribs. As the thorax expands, intrathoracic pressure decreases, drawing air through the tracheobronchial tree into the alveoli, or distal air sacs, filling the expanding lungs. Oxygen diffuses into the adjacent pulmonary capillaries as carbon dioxide exchanges from the blood into the alveoli.

During expiration, the chest wall and lungs recoil and the diaphragm relaxes and rises passively. Abdominal muscles assist in expiration. As air flows outward, the chest and abdomen return to their resting positions.

Normal breathing is quiet and easy—barely audible near the open mouth as a faint whish. When a healthy person lies supine, the breathing movements of the thorax are relatively slight. By contrast, the abdominal movements are usually easy to see. In the sitting position, movements of the thorax become more prominent.

During exercise and in certain diseases, extra work is required to breathe, and accessory muscles are recruited; the sternocleidomastoids (SCM) and the scalenes may become visible (Fig. 8-13).

FIGURE 8-13 Accessory muscles in the neck.

Accessory muscles in the neck.

The Health History

Common or Concerning Symptoms

  • Chest pain
  • Shortness of breath (dyspnea)
  • Wheezing
  • Cough
  • Blood-streaked sputum (hemoptysis)
  • Daytime sleepiness or snoring and disordered sleep

Chest Pain

Complaints of chest pain or chest discomfort raise concerns about the heart but often arise from other structures in the thorax and lungs. To assess this symptom, you must pursue a dual investigation of both thoracic and cardiac causes. Sources of chest pain are listed below. For this important symptom, keep all of these possibilities in mind.

See Table 8-1, Chest Pain, pp. 330–331.

TABLE 8-1 Chest Pain

Problem Process Location Quality Severity Timing Factors That Aggravate Factors That Relieve Associated Symptoms
Angina Pectoris Temporary myocardial ischemia, usually secondary to coronary atherosclerosis Retrosternal or across the anterior chest, often radiates to the shoulders, arms, neck, lower jaw, or upper abdomen Pressing, squeezing, tight, heavy, occasionally burning Mild to moderate, sometimes perceived as discomfort rather than pain Usually 1–3 min but up to 10 min. Prolonged episodes up to 20 min Often exertion, especially in the cold; meals; emotional stress. May occur at rest Often, but not always, rest, nitroglycerin Sometimes dyspnea, nausea, sweating
Myocardial Infarction Prolonged myocardial ischemia, resulting in irreversible muscle damage or necrosis Same as in angina Same as in angina Often, but not always, a severe pain 20 min to several hours Not always triggered by exertion Not relieved by rest Dyspnea, nausea, vomiting, sweating, weakness
Pericarditis Irritation of parietal pleura adjacent to the pericardium Retrosternal or left precordial, may radiate to the tip of left shoulder Sharp, knifelike Often severe Persistent Breathing, changing position, coughing, lying down, sometimes swallowing Sitting forward may relieve it Seen in autoimmune disorders, postmyocardial infarction, viral infection, chest irradiation
Aortic Dissection A splitting within the layers of the aortic wall, allowing passage of blood to dissect a channel Anterior or posterior chest, radiating to the neck, back, or abdomen Ripping, tearing Very severe Abrupt onset, early peak, persistent for hours or more Hypertension If thoracic, hoarseness, dysphagia; also syncope, hemiplegia, paraplegia
Pleuritic Pain Inflammation of the parietal pleura, as in pleurisy, pneumonia, pulmonary infarction, or neoplasm; rarely, subdiaphragmatic abscess Chest wall overlying the process Sharp, knifelike Often severe Persistent Deep inspiration, coughing, movements of the trunk Of the underlying illness
Gastrointestinal and Other
Gastrointestinal Reflux Disease Irritation or inflammation of the esophageal mucosa due to reflux of gastric acid from lowered esophageal sphincter tone Retrosternal, may radiate to the back Burning, may be squeezing Mild to severe Variable Large meal; bending over, lying down Antacids, sometimes belching Sometimes regurgitation, dysphagia; also cough, laryngitis, asthma
Diffuse Esophageal Spasm Motor dysfunction of the esophageal muscle Retrosternal, may radiate to the back, arms, and jaw Usually squeezing Mild to severe Variable Swallowing of food or cold liquid; emotional stress Sometimes nitroglycerin Dysphagia
Chest Wall Pain, Costochondritis Variable, including trauma, inflammation of costal cartilage Often below the left breast or along the costal cartilages Stabbing, sticking, or dull, aching Variable Fleeting to hours or days Coughing; movement of chest, trunk, arms Often local tenderness
Anxiety, Panic Disorder Unclear Precordial, below the left breast, or across the anterior chest Stabbing, sticking, or dull, aching Variable Fleeting to hours or days May follow effort, emotional stress Breathlessness, palpitations, weakness, anxiety

Note: Chest pain may be referred from extrathoracic structures in the neck (arthritis) and abdomen (biliary colic, acute cholecystitis).

Sources of Chest Pain and Related Causes

The myocardium Angina pectoris, myocardial infarction, myocarditis The pericardium Pericarditis The aorta Aortic dissection The trachea and large bronchi Bronchitis The parietal pleura Pericarditis, pneumonia, pneumothorax, pleural effusion, pulmonary embolus The chest wall, including the musculoskeletal and neurologic systems Costochondritis, herpes zoster The esophagus Gastroesophageal reflux disease, esophageal spasm, esophageal tear Extrathoracic structures such as the neck, gallbladder, and stomach Cervical arthritis, biliary colic, gastritis

Chest pain is reported in one in four patients with panic and anxiety disorders.1–3

This section focuses on pulmonary complaints, including chest wall symptoms, difficulty breathing (dyspnea), wheezing, cough, coughing up blood (hemoptysis), and daytime sleepiness or snoring and disordered sleep. For symptoms of exertional chest pain, palpitations, shortness of breath when supine (orthopnea) or at night relieved by sitting upright (paroxysmal nocturnal dyspnea), and edema, see Chapter 9, The Cardiovascular System (see pp. 355–358).

Your initial questions should be as open-ended as possible. “Do you have any discomfort or unpleasant feelings in your chest?” Ask the patient to point to the location of the pain in the chest. Watch for any gestures as the patient describes the pain. Elicit all seven attributes of chest pain to distinguish among its various causes (see p. 79).

A clenched fist over the sternum suggests angina pectoris; a finger pointing to a tender spot on the chest wall suggests musculoskeletal pain; a hand moving from the neck to the epigastrium suggests heartburn.

Lung tissue has no pain fibers. Pain in conditions such as pneumonia or pulmonary infarction usually arises from inflammation of the adjacent parietal pleura. Muscle strain from prolonged recurrent coughing or costochondral inflammation may also be responsible. The pericardium also has few pain fibers. The pain of pericarditis stems from inflammation of the adjacent parietal pleura. Extrapulmonary sources of chest pain include gastroesophageal reflux disease and anxiety, but the mechanism remains obscure.[1]–[4]