Anatomy, Thorax, Lung Pleura And Mediastinum


Article Author:
Navid Mahabadi
Alberto Goizueta


Article Editor:
Bruno Bordoni


Editors In Chief:
Yvonne Carter
Jason Wallen


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Frank Smeeks
Kristina Soman-Faulkner
Trevor Nezwek
Radia Jamil
Patrick Le
Sobhan Daneshfar
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
7/16/2019 2:01:26 PM

Introduction

A pleura is a serous membrane that folds back on itself to form a two-layered membranous pleural sac. The outer layer is called the parietal pleura and attaches to the chest wall. The inner layer is called the visceral pleura and covers the lungs, blood vessels, nerves, and bronchi. There is no anatomical connection between the right and left pleural cavities. [1] With the addition of pleural fluid, the lung pleura allows for easy movement of the lungs and inflation during breathing.

The mediastinum is a central compartment in the thoracic cavity between the pleural sacs of the lungs. It is divided into two major parts, the superior and inferior portions. The inferior portion is then further divided into the anterior, middle, and posterior portion. Each region of the mediastinum contains specific groups of structures. [2]

  • Superior mediastinum: Organs: thymus, trachea, esophagus; Arteries: aortic arch, brachiocephalic trunk, left common carotid artery, left subclavian artery; Veins and lymphatics: superior vena cava, brachiocephalic vein, thoracic duct; Nerves: vagus nerve, left recurrent laryngeal nerve, cardiac nerve, phrenic nerve
  • Anterior mediastinum: Organs: thymus; Arteries: small arterial branches; Veins and lymphatics: small branches; Nerves: none
  • Middle mediastinum: Organs: heart, pericardium; Arteries: ascending aorta, pulmonary trunk, pericardiacophrenic arteries; Veins and lymphatics: superior vena cava, azygos vein, pulmonary vein, pericardiacophrenic vein; Nerve: phrenic
  • Posterior mediastinum: Organs: esophagus; Arteries: thoracic aorta; Veins and lymphatics: Azygos vein, hemiazygos vein, thoracic duct; Nerve: vagus nerve

Structure and Function

The pleural cavity is a space between the visceral and parietal pleura. The space contains a tiny amount of serous fluid which has two key functions.

The serous fluid continuously lubricates the pleural surface and makes it easy for them to slide over each other during lung inflation and deflation. The serous fluid also generates surface tension, which pulls the visceral and parietal pleura adjacent to each other. This function will allow the thoracic cavity to expand during inspiration. 

NB; when air enters the pleural space, the surface tension will disappear, and the resulting condition is known as a pneumothorax.

Pleural Recesses

Located posterior and anterior, there are spaces where the pleural cavity is not totally filled by the lung parenchyma. This space is known as the recess - an area where the adjacent surfaces of the parietal pleura come into contact. The two recesses in the pleural cavity include the following:

  • Costomediastinal recess which is found between the mediastinal and costal pleura. The space is located just posterior the sternum.
  • Costodiaphragmatic recess is found between the diaphragmatic and costal pleura.

The reason these recesses are important is because they provide a space for fluid to accumulate. Pleural effusions usually collect in the costodiaphragmatic recess.

Blood Supply and Lymphatics

The visceral pleura receives its blood supply from the bronchial circulation while the parietal pleura receives its blood supply from the intercostal arteries.

Nerves

The costal and cervical portions of the parietal pleura are innervated by the intercostal nerve, and the diaphragmatic portion is supplied by the phrenic nerve. The parietal pleura is the only portion of the pleura that can sense pain. The visceral pleura is innervated by the autonomic nervous system (ANS) and lacks sensory innervation.

Surgical Considerations

Pneumothorax is a common clinical event, and it occurs when the pleural space is violated. The patient can present with a variety of symptoms depending on the size of the pneumothorax. With a small pneumothorax, the patient may be asymptomatic. But if the pneumothorax is large, the following symptoms will be present:

  • Chest pain
  • Dyspnea
  • Asymmetrical chest expansion

Percussion and auscultation will reveal a hyperresonant chest with no breath sounds.

The two types of pneumothorax include:

Spontaneous: These pneumothoraces occur without any traumatic event. they are most common in young males who smoke. The most common cause of a spontaneous pneumothorax is the presence of small blebs on the superior surface of the upper lobes.

Traumatic: Traumatic pneumothorax is very common and may occur as a result of a central line insertion, penetrating chest trauma or rib fracture.

The treatment of a pneumothorax again depends on the size and presence of symptoms. Most asymptomatic cases can be observed if the patient is reliable and agrees to follow up. Repeat chest x-rays are required to ensure that the pneumothorax is resolving. For patients with large and symptomatic pneumothorax, insertion of a chest tube is the simplest treatment. Unlike the past when large sized chest tubes were inserted, today several kits are available with small size 8-12 French tubes which can be inserted without causing too much pain.

Clinical Significance

Normally, there is a small amount of pleural fluid found in the pleural cavity. When there is a pathological collection of pleural fluid, it is called a pleural effusion. Pleural effusion is classified as either exudative or transudative and can be caused by multiple mechanisms including lymphatic obstruction, increased capillary permeability, decreased plasma colloid pressure, increased capillary, venous pressure, and increased negative intrapleural pressure.

The mediastinum is commonly a site for tumors, and specific regions of the mediastinum are prone to certain tumors. Pneumomediastinum can also develop when air is introduced into the mediastinum most commonly seen in ruptures of the esophagus. A widened mediastinum is a worrisome clinical sign for possible aortic aneurysm or rupture.

The mediastinum is also very important when it comes to lung cancer. All lung cancers when advanced involve the mediastinal lymph nodes. The treatment for a patient with a lung cancer without mediastinal lymph node involvement is surgery, and it has a high cure rate. However, once the mediastinal nodes are involved, surgery alone is not curative, and patients need chemotherapy. To determine if the mediastinal lymph nodes are involved, a CT scan of the chest is necessary. If the nodes are greater than 1 cm, then a biopsy is required. The lymph nodes are biopsied using mediastinoscopy. If they turn out to be negative, then lobectomy alone is sufficient.

The status of the mediastinal lymph nodes is also important when dealing with patients with sarcoidosis, lymphoma, and tuberculosis. In each of these cases, a mediastinoscopy is needed to assess the histology before treatment can be provided.


Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Anatomy, Thorax, Lung Pleura And Mediastinum - Questions

Take a quiz of the questions on this article.

Take Quiz
Which of the following statements about mediastinal masses is false?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which portion of the the thoracic pleura lacks sensory innervation?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which structure would be found in the superior mediastinum?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
How much pleural fluid is present in the chest cavity of a healthy adult?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Anatomy, Thorax, Lung Pleura And Mediastinum - References

References

Adeyinka A,Pierre L, Air Leak . 2018 Jan     [PubMed]
Volpe JK,Makaryus AN, Anatomy, Chest, Heart and Pericardial Cavity . 2018 Jan     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of Surgery-Thoracic. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for Surgery-Thoracic, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in Surgery-Thoracic, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of Surgery-Thoracic. When it is time for the Surgery-Thoracic board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study Surgery-Thoracic.