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Diaphragm - want to learn more about it?

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Diaphragm

The diaphragm is an unpaired, dome shaped skeletal muscle that is located in the trunk which separates the thoracic and abdominal cavities from each other by closing the inferior thoracic aperture. The diaphragm is the primary muscle that is active in inspiration. Contraction of the muscle facilitates expansion of the thoracic cavity. This increases volume of the the cavity, which in turn decreases the intrathoracic pressure allowing the lungs to expand and inspiration to occur.

As you can see, the diaphragm is much more than just a sheath separating your thoracic and abdominal cavities. This article will examine this intricate and crucial muscle in detail, looking at its attachments, innervation, and structures which pass through it.

Key facts about the diaphragm
Attachments

Sternal part: Posterior aspect of xiphoid process

Costal part: Internal surfaces of lower costal cartilages and ribs 7-12

Lumbar part: Medial and lateral arcuate ligaments (lumbocostal arches), Bodies of vertebrae L1-L3 (+intervertebral discs), Anterior longitudinal ligament

Relations Pleural cavities, pericardial sac, liver, right kidney, right suprarenal gland, stomach, spleen, left kidney, left suprarenal gland
Openings

Aortic hiatus (aorta, azygos vein, thoracic duct), esophageal hiatus (esophagus, vagus nerve), caval hiatus (inferior vena cava) - 'I ATE TEN EGGS AT 12'

Greater, lesser, least splanchnic nerves, superior epigastric vessels

Innervation Phrenic nerves (C3-C5) (Sensory innervation of peripheries via 6th-11th intercostal nerves)
Functions Depresses costal cartilages, primary muscle of breathing (inspiration)

Anatomy

The diaphragm is a musculotendinous sheet. It has three muscular parts (sternal, costal, and lumbar), each have their own origin and all insert into the central tendon of diaphragm. The diaphragm is shaped as two domes, with the right dome positioned slightly higher than the left because of the liver. The depression between the two domes is due to the pericardium slightly depressing the diaphragm. 

Thoracic surface of the diaphragm – an overview

The diaphragm has two surfaces: thoracic and abdominal. The thoracic diaphragm is in direct contact with the lungs and pericardium, while the abdominal diaphragm is in direct contact with the liver, stomach, and spleen.

Abdominal surface of the diaphragm – an overview.

Since one function of the diaphragm is to provide passageway for structures from the thorax to the abdomen, its surface has several openings: caval opening (vena caval foramen), esophageal hiatus, and aortic hiatus.

Anatomically, you can define hiatus as an opening, slit, or gap that allows structures to pass. These openings in the diaphragm allow the inferior vena cava, esophagus, vagus nerves, descending aorta, and other structures to pass through. 

Next, why not try quizzing how well you've learned the anatomy of the diaphragm? Anatomy quiz questions are the secret to your success!

An easy way to remember the location and structures passing through the diaphragm is by using this mnemonic: 'I ate ten eggs at 12.' - I (IVC) ate (T8) ten (T10) eggs (esophagus + vagus) at (azygos + thoracic duct) 12 (T12). 

Openings of the diaphragm and structures passing through
Caval opening (vena caval foramen)    

 Inferior vena cava    

Branches of the right phrenic nerve

Esophageal hiatus   

Esophagus

Anterior and posterior vagal trunks

Aortic hiatus

 Descending aorta

Azygos vein

Thoracic duct

There is a certain pathological condition called hiatal hernia, when part of the stomach protrudes from the abdomen into the thorax through the esophageal hiatus. You can learn more about this condition by reading this interesting clinical case.

Solidify your knowledge about the diaphragm, its surfaces, and openings by watching these videos and then quizzing yourself.

Function

The diaphragm is one of the main muscles of respiration. When the muscle fibers contract, the diaphragm is flattened. This increases the volume of the thoracic cavity vertically, which decreases intrapulmonary pressure, and air enters the lungs.

When the diaphragm relaxes, thoracic volume decreases, intrapulmonary pressure increases, and air flows out of the lungs. Learn more about the anatomy of breathing and respiratory organs with these resources.

When the diaphragm works with the anterolateral abdominal muscles, diaphragm contraction assists in increasing intra-abdominal pressure. This is needed in actions such as expelling vomit, defecation, micturition (urination), and parturition (childbirth). Another function of the diaphragm is to provide a passageway for certain structures from the thorax to the abdomen (inferior vena cava, esophagus, and aorta) as mentioned earlier.

Diaphragm Muscle

The diaphragm is a musculotendinous structure with a peripheral attachment to a number of bony structures. It is attached anteriorly to the xiphoid process and costal margin, laterally to the 11th and 12th ribs, and posteriorly to the lumbar vertebrae. The posterior attachment to the vertebrae is by tendinous bands called crura. The crura are attached to the anterior aspect of the bodies of the 1st, 2nd and 3rd lumbar vertebrae. The muscle fibres, extending from their bony attachments, converge on a central tendon.

Check out this article and download Kenhub’s ebooks containing muscle anatomy charts for all 600+ muscles of the human body.

Innervation

Motor innervation of the diaphragm comes from the phrenic nerves (C3-C5). These nerves innervate the diaphragm from its abdominal surface after they penetrate it. Sensory innervation (pain and proprioception) at the central tendinous part is innervated by the phrenic nerves, while the peripheral muscular portions are innervated by 6th to 11th intercostal nerves. 

Learn more about the diaphragm anatomy with our custom quiz which covers the anatomy, blood supply, innervation and function of the diaphragm!

Video tutorials

Quizzes

Clinical Notes

Hiccups

A very common disorder of the diaphragm that affects most people at some point is hiccups. Hiccups occur due to involuntary, intermittent contraction of the muscle. They are usually caused by consumption of large volumes of food over a short amount of time.

Hernias

Herniation may occur through the diaphragm. At the level of the esophageal hiatus, the stomach may herniate into the posterior mediastinum. A diaphragmatic hernia can be congenital.  These occur as a result of abnormalities in the development of the diaphragm in the fetus. Abdominal organs may protrude into the thoracic cavity and disrupt the development of the lungs, causing problems in lung development and the functioning of the lungs after birth.

Diaphragmatic hernias can also be acquired. These usually occur as a result of blunt force trauma, such as in a road traffic accident or a severe fall. Surgery is required to repair a diaphragmatic hernia.

Diaphragm - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,084,544 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • F. Netter: Atlas of Human Anatomy, 6th Edition, Elsevier Saunders (2014).
  • J.A. Gosling, P.F. Harris, J.R. Humpherson et al.: Human Anatomy, Colour Atlas and Textbook, 5th Edition, Mosby Elsevier (2008).
  • R. Drake, A.W. Vogl, A.W.M. Mitchell: Gray’s Anatomy for Students, 3rd Edition, Churchil Livingston Elsevier (2015).

Author:

  • Niamh Gorman
  • Jana Vaskovic
  • Nicola McLaren
  • Alexandra Osika

Illustrators:

  • Diaphragm - ventral view - Yousun Koh
  • Phrenic nerve - caudal view - Stephan Winkler
  • Hiatus of vena cava - caudal view - Stephan Winkler
  • Greater splanchnic nerve - ventral view - Yousun Koh
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

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