Anatomy L. 23 Lungs and Pleura

What are the fluids that can accumulate in the pleural cavity?

Fluids that can accumulate in the pleural cavity include *serous fluid* (hydrothorax), *blood* (hemothorax), and *chyle* (chylothorax).

Describe normal inspiration and expiration. What are their effects on the vertical dimension of the thorax and intrathoracic pressure?

*Normal inspiration* involves contraction of the diaphragm and relaxation of the abdominal muscles. Combined, they *increase* the vertical dimension of the thorax and *decrease* intrathoracic pressure. As a result, air enters the lungs. *Normal expiration* involves relaxation of the diaphragm and contraction of the abdominal muscles. Combined, they *decrease* the vertical dimension of the thorax and *increase* intrathoracic pressure. As a result, air is forced out of the lungs.

What is pneumothorax? What are the three basic types?

*Pneumothorax* is the presence of air or gas in the pleural cavity. It is often due to trauma (fractured rib, gunshot, stab wound) or lung disease (cystic fibrosis, emphysema, asthma, lung cancer). It presents with chest pain and shortness of breath. The three basic types are *spontaneous pneumothorax* in which there is no underlying disease; usually a bleb or cyst ruptures (mountain climbing, scuba diving), *open pneumothorax* which a "sucking chest wound", and *tension pneumothorax* which is a progressive build-up of air in the pleural cavity that pushes mediastinum to one side and pressure obstructs venous return to the heart deviation of trachea and hyperexpanded chest and may require a *needle thoracostomy* in the 2nd - 4th ICS MCL

What is the clinical significance of the cervical pleura?

A penetrating wound in the root of the neck may tear the *cervical pleura*, allowing air to enter the pleural cavity (pneumothorax) and causing the lung to collapse

What are the bronchopulmonary segments? What are their clinical relevance?

Each lung can be divided into different *bronchopulmonary segments* which are different functional divisions of the lungs. If a segment is removed surgically, the lung can still function normally.

What can result from a lesion of the phrenic nerves? Describe the referred pain that involves the phrenic nerves.

Each phrenic nerve (C3,4,5) is the sole motor innervation to its half of the diaphragm (hemidiaphragm), and bilateral phrenic nerve lesions result in *respiratory paralysis*. That is why patients with spinal cord injuries at or above the C4 level usually don't survive without respiratory assistance. The phrenic nerve also supplies sensation to all but the periphery of the diaphragm. Therefore, the origin of the phrenic nerves from the cervical spinal cord provides the basis for sensations produced by irritation of the diaphragmatic pleura or peritoneum by thoracic or abdominal disease (e.g., from inflammation of the gallbladder) to be "felt" by the patient in the shoulder region in the C3,4 dermatomes (referred pain).

Why are each pleural cavities separated? What does inflammation of the pleurae cause?

Each pleural cavity is a separate compartment which allows for isolation of an infection. Inflammation or disease can cause *pleurisy* (pleuritis). The inflamed pleural layers rub against each other every time the lungs expand to breathe in air. This can cause sharp pain when breathing. Such adhesions produce pain during exertion. Even in the absence of adhesions, the roughness of the pleural surfaces resulting from pleurisy produces a pleural friction rub detectable with a stethoscope.

What are the muscled used for Inspiration/Expiration (whether it's normal or forced)

For normal Inspiration: the *Diaphragm* which is innervated by the *Phrenic nerves*, and the *intercostal muscles*. These muscles are attached between the ribs and are important in manipulating the width of the rib cage. No muscles are required for normal expiration, however the *anterior abdominal wall muscles* are recruited for forced expiration.

How does an open pneumothorax differ from a tension pneumonthorax with respect to a cardiac shift?

In an open pneumothorax air can go in and out, the lung is collapsed and you get a cardiac shift, but as the patient exhales, the heart returns to its normal position In an tension pneumothorax are cannot get out, and a cardiac shift continues to happen which can compress the vena cava along with the lungs.

What do you need to be aware of when placing a chest tube (Thoracocentesis)

Location of the VAN Location of the Costodiaphragmatic recess Location of the lung

How are oxygen and nutrients provided to lungs?

Oxygen and nutrients are provided to the tissues of the lungs through the *bronchial arteries*, which has two sides. The left side has a *superior and inferior left bronchial artery* that arise directly from the *anterior surface of the thoracic aorta*. The right side has a single right bronchial artery, which typically arises from the proximal part of one of the *posterior intercostal arteries* (usually the right third) or from a *common trunk with the left superior bronchial artery*.

What are the borders of the triangle of auscultation? What part of the lung can be heard there?

Superiorly and medially, by the inferior portion of the *Trapezius*, inferiorly, by the *Latissimus Dorsi* and laterally, by the medial border of the *scapula* You are listening to the *inferior lobe of the lung*

What is the Hilum of the Lung and Pulmonary Ligament?

The *Hilum of lung* is the region on the medial surface of the lung outlined by the *pleural reflection*, where the structures that make up the root of the lung enter The *Pulmonary ligament* is a thin reflection of pleura connecting the lung hilum to the mediastinum

What is the Root of the Lung? How does it relate to the phrenic and vagus nerves?

The *Root of lung* is the collection of tubular structures connecting the lung to structures in the mediastinum: 1º bronchus, pulmonary artery, pulmonary vein, bronchial vessels, nerves, lymphatics Note: The phrenic nerve runs anterior to the root of the lung and the vagus nerve runs posterior to the root of the lung

Describe the costodiaphragmatic recess and the costomediastinal recess. What is pleural effusion?

The *costodiaphragmatic recess*, which occurs between the costal and diaphragmatic parts of the parietal pleura, and the *costomediastinal recess*, which occurs anteriorly between the costal and mediastinal parts of the parietal pleura (larger on the left side due to the cardiac notch). Fluids may collect in these spaces (*pleural effusion*). Fluid may accumulate within the costodiaphragmatic recess in upright patients with pathological conditions or following injury. It may have to be removed with a hypodermic needle (thoracocentesis) or by insertion of a chest tube.

What are Pleurae? What are their parts?

The *pleurae* are closed sacs of serous membrane that enclose each lung and consist of 2 parts: the *Parietal pleura* and the *Visceral pleura*

Describe the Parietal Pleura. What are the regions it is divided into? What is the clinical significance of the endothoracic fascia?

The Parietal Pleura is the outer pleura. It encloses the entire pleural cavity and separates it from the other regions of the thorax. It is divided into regions based on the structure that it comes into contact with: The *Costal pleura*, *Diaphragmatic pleura*, *Mediastinal pleura* and *Cervical pleura/Cupola*. Separated from the thoracic wall by a loose connective tissue layer, the *endothoracic fascia* provides a natural cleavage plane for surgery

Describe the Visceral Pleura

The Visceral Pleura is the inner pleura. It surrounds the lung and is tightly adhered to the lung surface.

What are the arteries that supply the diaphragm?

The arteries supplying the diaphragm are the: *Pericardiacophrenic* (from internal thoracic artery), then *Musculophrenic* (the terminal branch of internal thoracic along w/ superior epigastric arteries), the *superior phrenic* (from thoracic aorta) and the *inferior phrenic arteries* (which are variable, but often from abdominal aorta)

What is the clinical relevance of the lungs and the thoracic inlet?

The cupola of the lung extends into the root of the neck. Penetrating wounds to the neck or poor technique in attempting to access the subclavian vein can result in a *collapsed lung*

What is the diaphragm? What is it innervated by and what are its opening?

The diaphragm is the main muscle involved with breathing. It separates the thoracic and abdominal cavities. The diaphragm is innervated by the *phrenic nerves* (C3-5) and has three openings: at *T8* is the caval opening for the inferior vena cava, at *T10* is the *Esophageal hiatus* for the esophagus & vagal trunks and at *T12* is the *Aortic hiatus* for the aorta & thoracic duct

What are the specific features of the left lung?

The left lung has *2 lobes* (Superior and inferior), the *Lingula* (segment that has a tongue shape), *1 fissure* (Oblique), a *Cardiac impression* and grooves for: Aorta, Esophagus, left subclavian artery, left brachiocephalic vein and the 1st rib.

How does the left parietal pleura differ from the right? What is the clinical significance of this difference?

The left parietal pleura deviates away from the body of the sternum in the region of the fifth intercostal space, forming a shallow notch. This *pleural notch* and the corresponding cardiac notch in the left lung allow insertion of a needle into the pericardium (e.g., to drain fluids from the pericardial cavity (*pericardiocentesis*) without entering the pleural cavity or damaging the lung. The area of the pericardium exposed by the pleural and cardiac notches is the bare area of pericardium.

What are the different parts of the lung?

The lung consists of a *Base* (diaphragmatic surface), *apex*, *Costal surface*/*mediastinal surface* and *Inferior*, *anterior*, and *posterior borders*

What are the lungs? How do air, oxygenated and deoxygenated blood enter/leave the lungs?

The lungs are the organs of respiration. The right normally slightly larger than left Air enters and leaves via the *primary bronchi*. Deoxygenated blood enters via the *pulmonary artery* and oxygenated blood leaves via *pulmonary veins*

Describe the movement of the ribs during respiration

The movement of the ribs during respiration can be described as a *Pump handle* (superior/anterior movement the sternyms) and a *bucket handle* (elevation of the lateral shaft of the rib).

What is the Pleural Cavity? What are the spaces that are associated with the pleural cavitiy?

The parietal and visceral pleura are separated by a potential space called the *Pleural Cavity*. Normally the two pleural layers are separated only by a thin layer of serous fluid which allows them to slide across each other easily. The lungs do not fill the entire pleural cavity so there are normally some actual spaces present as well as potential space: The *Costomediastinal recess*, and the *Costodiaphragmatic recess* which is the "real" space (as opposed to potential space) and has clinical significance in multiple areas of medicine.

What are the specific features of the right lung?

The right lung has *3 Lobes* (Superior, Middle, and Inferior), *2 fissures* (Horizontal and Oblique) and has grooves for: Azygos v., Esophagus, R. subclavian a., Vena cavae and the 1st rib.

How does the right main bronchus differ from the left main bronchus? What does this result in? What is the clinical relevance?

The right main bronchus is wider, shorter, and more vertical than the left main bronchus. As a result, inhaled objects are more likely to enter the right main bronchus and right lung. The right inferior (lower) lobar bronchus is in line with the right main bronchus, and foreign objects often lodge there

What does the thoracic cavity consist of? What is the mediastinum?

The thoracic cavity consists of right and left pleural cavities, each surrounding a lung and a central mass of tissue, called the *mediastinum*, that separates the left pleural cavity and lung from the right pleural cavity and lung .

Describe the pathway from the trachea to bronco-pulmonary segements.

The trachea descends into the thorax and splits into left and right *main* (primary) bronchi. The main bronchi divide into *lobar* (secondary) bronchi, which divide into *segmental* (tertiary) bronchi. Each segmental bronchi supplies a *bronco-pulmonary segment*, the functional unit of the lung

What is the clinical significance of the pulmonary veins?

Unlike the bronchi and pulmonary artery branches, the larger tributaries of the pulmonary veins occupy *intersegmental positions* and are used as surgical landmarks during *segmentectomies*.

What are the superior and inferior thoracic apertures?

superior thoracic aperture (*Thoracic Inlet*) refers to the opening at the top of the thoracic cavity The inferior thoracic aperture (*Thoracic Outlet*) is much larger than the thoracic inlet. The thoracic outlet is the lower opening of the thoracic cavity whose edges are the lowest ribs. It is closed by the diaphragm, which separates the thoracic cavity from the abdominal cavity.