TBL9 - Pleurae and Lungs

Question 1

What separates the right and left pleural cavities?

Answer 1

Continuity of the parietal and visceral pleurae at the roots of the lungs completely separates the right and left pleural cavities (i.e., space between the visceral and parietal pleurae)

Question 2

Cite the 4 regional parts of the parietal pleura

Answer 2

The parietal pleura consists of three parts—costal, mediastinal, and diaphragmatic—and the cervical pleura

Question 3

Do the lungs fully occupy the pleural cavities during normal respiration? What creates the costodiaphragmatic recesses?

Answer 3

1) During normal respiration, the lungs do not fully occupy the pleural cavities
2) Thus, contact of the lowest part of the costal pleura with the peripheral part of the diaphragmatic pleura creates the costodiaphragmatic recesses

Question 4

How does the thin fluid layer in the pleural cavity normally sustain inflation of the lungs during inspiration?

Answer 4

1) Normal lungs in situ remain distended even when the airway passages are open because the outer surfaces of the lungs (visceral pleura) adhere to the inner surface of the thoracic walls (parietal pleura) as a result of the surface tension provided by the pleural fluid
2) The elastic recoil of the lungs causes the pressure in the pleural cavities to be sub-atmospheric

Question 5

How is fluid sampled in the costodiaphragmatic recess without damaging the inferior border of the lungs? How do contents of the ribs’ costal grooves determine proper execution of the procedure?

Answer 5

1) To avoid damage to the intercostal nerve and vessels, the needle is inserted superior to the rib, high enough to avoid the collateral branches
2) Inserting the needle into the 9th intercostal space in the midaxillary line during expiration will avoid the inferior border of the lung
3) The needle should be angled upward, to avoid penetrating the deep side of the recess (a thin layer of diaphragmatic parietal pleura and diaphragm overlying the liver)

Question 6

Why can irritation of the parietal pleural produce either local or referred pain?

Answer 6

The parietal pleura is richly supplied by branches of the intercostal and phrenic nerves. Irritation of the parietal pleura may produce local pain or referred pain projected to dermatomes supplied by the same spinal (posterior root) ganglia and segments of the spinal cord

Question 7

What is the apex of the lungs covered by? Where does this extend?

Answer 7

1) The apex of the lungs is covered by cervical pleura

2) It extends into the root of the neck

Question 8

What causes Pancoast’s Syndrome?

Answer 8

When an apical lung tumor compresses the trunks of the brachial plexus, pain extending down the ipsilateral arm into the hand constitutes Pancoast’s Syndrome that is usually associated with a history of smoking

Question 9

What causes Horner’s Syndrome?

Answer 9

If the apical tumor compresses the sympathetic trunk, the ipsilateral eye could be affected and this constitutes Horner’s Syndrome

Question 10

What creates a pneumothorax? What would cause the ipsilateral lung to collapse?

Answer 10

1) A penetrating wound through one side of the thoracic wall would rupture the parietal pleura and allow air to enter the pleural cavity and thereby create a pneumothorax
2) The atmospheric pressure in the pleural cavity would collapse the ipsilateral lung

Question 11

What would occur if the pneumothorax created a tissue flap that allowed air to enter but not leave the pleural cavity? What would progressive compression of the heart from a pneumothorax cause?

Answer 11

1) If the wound created a tissue flap that allowed air to enter but not leave the pleural cavity, continuous expansion of the ipsilateral cavity would collapse the lung and permanently push the heart to the contralateral side
2) Progressive compression of the heart and contralateral lung would create a tension pneumothorax that could be fatal

Question 12

Why is the cervical pleura vulnerable during infancy and early childhood?

Answer 12

1) The cervical pleura reaches a relatively higher level in infants and young children because of the shortness their necks
2) Consequently, the cervical pleura is especially vulnerable to injury during infancy and early childhood

Question 13

What are common causes of a pneumothorax, hydrothorax, and hemothorax?

Answer 13

1) Entry of air into the pleural cavity (pneumothorax), resulting from a penetrating wound of the parietal pleura from a bullet, for example, or from rupture of a pulmonary lesion into the pleural cavity (bronchopulmonary fistula), results in collapse of the lung
2) Fractured ribs may also tear the visceral pleura and lung, thus producing pneumothorax
3) The accumulation of a significant amount of fluid in the pleural cavity (hydrothorax) may result from pleural effusion (escape of fluid into the pleural cavity)
4) With a chest wound, blood may also enter the pleural cavity (hemothorax). Hemothorax results more commonly from injury to a major intercostal or internal thoracic vessel than from laceration of a lung

Question 14

With a pneumothorax, why is the mediastinum only shifted toward the affected side during expiration?

Answer 14

1) When a lung collapses, it occupies less volume within the pulmonary cavity and the pulmonary cavity does not increase in size (in fact, it may decrease in size) during inspiration
2) This reduction in size will be evident radiographically on the affected side by elevation of the diaphragm above its usual levels, intercostal space narrowing (ribs closer together), and displacement of the mediastinum (mediastinal shift; most evident via the air-filled trachea within it) toward the affected side

Question 15

What creates lobulation of the lungs? What is at the inferior border of the right 4th rib and costal cartilage?

Answer 15

1) The oblique and horizontal fissures create lobulation of the lungs and use
2) The horizontal fissure is located at the inferior border of the right 4th rib and costal cartilage

Question 16

What forms the anterior aspect of the lungs? What forms the posterior aspect of the lungs? Recognize the cardiac notch and lingula of the left lung

Answer 16

1) The superior lobe of the left lung and the superior and middle lobes of the right lung form the anterior aspect of the lungs
2) The posterior aspect of the lungs is formed mainly by the inferior lobes of both lungs

Question 17

What forms impressions on the mediastinal surfaces of embalmed lungs? What forms lobar impressions on the right lung? What forms lobar impressions on the left lung?

Answer 17

1) Impressions on the mediastinal surfaces of embalmed lungs are created by the heart, great vessels and esophagus
2) Lobar impressions are formed by the superior vena cava and esophagus on the right lung
3) The lobar impressions are formed by the heart and aorta on the left lung

Question 18

What is the hilum? What are the primary structures in the hilum?

Answer 18

1) The hilum is a “doorway” for structures to enter and leave the lungs
2) The right and left main bronchi, the pulmonary arteries, and the two right and two left main pulmonary veins are the primary structures in the hilum

Question 19

What occurs at the level of the sternal angle? What do the main pulmonary arteries and bronchi divide into?

Answer 19

1) At the level of the sternal angle, the trachea and pulmonary trunk bifurcate into the left and right main bronchi and pulmonary arteries
2) The main arteries (and bronchi) subsequently divide into lobar arteries and bronchi that supply the lobes of the lungs

Question 20

Which main bronchus is more likely to lodge an aspirated foreign body?

Answer 20

Because the right main bronchus is wider and shorter and runs more vertically than the left main bronchus, aspirated foreign bodies or food is more likely to enter and lodge in it or one of its branches

Question 21

What is the primary cause of bronchogenic carcinomas and where do primary tumors most commonly arise? Why is the brain a common site of hematogenous metastasis?

Answer 21

1) Lung cancer (carcinoma—CA) is mainly caused by cigarette smoking; most cancers arise in the mucosa of the large bronchi and produce a persistent, productive cough or hemoptysis
2) The primary tumor, observed radiologically as an enlarging lung mass, metastasizes early to the bronchopulmonary lymph nodes and subsequently to other thoracic lymph nodes. Common sites of hematogenous metastases (spreading through the blood) of cancer cells from a bronchogenic carcinoma are the brain, bones, lungs, and suprarenal glands

Question 22

How are bronchopulmonary segments formed? Why is thin connective tissue septa that separates these segments clinically important?

Answer 22

1) Lobar bronchi generate multiple segmental bronchi that create bronchopulmonary segments in each lung
2) Thin connective tissue septa separate the segments; thus, the segments are surgically resectable

Question 23

Cite the bronchopulmonary segments derived from segmental bronchi in the superior and middle lobes of the right lung and the superior lobe of the left lung

Answer 23

1) Superior lobe of right lung:
a) Apical
b) Posterior
c) Anterior
2) Middle lobe of right lung:
a) Lateral
b) Medial
3) Superior lobe of left lung:
a) Apical**
b) Posterior**
c) Anterior
d) Superior lingular
e) Inferior lingular
* * Typically combine into apicoposterior segment

Question 24

What do branches of segmental bronchi terminate into? What are alveolar sacs formed by?

Answer 24

1) Branches of the segmental bronchi terminate into multiple generations of bronchioles that progressively taper and unite with the alveolar sacs
2) The sacs are formed by clusters of pulmonary alveoli

Question 25

What supplies pulmonary capillaries within the walls of the alveoli? What do these capillaries drain into?

Answer 25

1) The tapering bronchioles are accompanied by tapering branches of the pulmonary arteries that supply pulmonary capillaries within the walls of the alveoli
2) The capillaries drain into venular tributaries of the pulmonary veins

Question 26

How do clinical outcomes from an embolus lodged in the main pulmonary artery differ from one lodged in a segmental pulmonary artery?

Answer 26

1) When a large embolus occludes a pulmonary artery, the patient suffers acute respiratory distress because of a major decrease in the oxygenation of blood, owing to blockage of blood flow through the lung. Death may occur in a few minutes
2) A medium size embolus may block an artery supplying a bronchopulmonary segment, producing a pulmonary infarct, an area of necrotic (dead) lung tissue

Question 27

What supplies the bronchial capillaries within the walls of the bronchi and bronchioles? Where do bronchial veins travel?

Answer 27

1) Bronchial arteries arise from the aorta and pass through the hilum to supply bronchial capillaries within the walls of the bronchi and bronchioles
2) Bronchial veins exit the hilum and return venous blood from the bronchial and bronchiolar walls to the superior vena cava

Question 28

Where do plexuses of lymphatic vessels in the lungs drain into? Where does lymph from the hilar nodes drain into?

Answer 28

1) Plexuses of lymphatic vessels dispersed throughout the lungs drain into hilar lymph nodes (i.e., lymph nodes at the hilum)
2) Lymph from the hilar nodes drains into the tracheobronchial lymph nodes at the tracheal bifurcation

Question 29

Where does lymph course from the tracheobronchial nodes to?

Answer 29

1) From the tracheobronchial nodes, lymph courses through multiple paratracheal lymph nodes before emptying into the right and left bronchomediastinal trunks
2) The trunks return pulmonary lymph to veins in the neck

Question 30

Where are post-synaptic sympathetic fibers from paravertebral ganglia at T1-T5 located and where do they travel?

Answer 30

The cardiopulmonary splanchnic nerves consist of post-synaptic sympathetic fibers from paravertebral ganglia at T1-T5, which rather than returning to the spinal nerves via the gray communicating rami, directly enter the hilum of the lungs

Question 31

Where do presynaptic parasympathetic fibers of the vagus nerve travel?

Answer 31

Presynaptic parasympathetic fibers of the vagus nerve (10th cranial nerve or CN X) enter the hilum and synapse with postsynaptic neurons of parasympathetic ganglia within the walls of the bronchi and bronchioles

Question 32

What nerve fibers accompany all branches of the bronchi and bronchioles?

Answer 32

The parasympathetic and sympathetic fibers form the right and left pulmonary plexuses (vagus nerve + sympathetic trunk) that accompany all branches of the bronchi and bronchioles

Question 33

What causes bronchoconstriction? What causes bronchodilation?

Answer 33

1) Parasympathetic-mediated contraction of smooth muscle in the walls of the bronchi and bronchioles causes bronchoconstriction
2) Sympathetic-mediated inhibition of the smooth muscle contraction induces bronchodilation