Anatomy of diaphragm in a nutshell

Anatomy of diaphragm

Components of the Diaphragm

1. Central tendon region = dense connective tissue.
2. Peripheral muscular part that surrounds tendon region & muscle fibers radiate inward:
   1. Anteriorly attached to sternum (sternal part) and 11^th-12^th costal margin (Costal part).
   2. Posteriorly attaches lumbar vertebrae (Lumbar part).
      • Right crus: fibers that anchor into the body of L1-L3 vertebrae.
        1. Fibers also wrap esophageal hiatus to form part of gastroesophageal sphincter.
        2. Inferiorly, the right crus attaches to the duodenum to form the ligament of Treitz.
        3. Usually larger than left crus.
      • Left crus: anchors into L1-L3 vertebrae.
        1. Fibers run out into the muscular part of the diaphragm.

•  Median arcuate ligament: Both crus have medial borders that form the median ligament formed behind lies aortic hiatus through which the aorta passes.

​​​

1-Sternak part; 2-Central tendon; 3- Esophageal hiatus; 4-Costal part; 5-Aortic hiatus; 6-Lateral crus; 7-Medial crus; 8-Intermediate crus; 9-Orifice for  v. cava

• Lateral to the median arcuate ligament is the medial arcuate ligament
  1. Is a gap in muscular attachment.  Arches where psoas muscle passes behind the diaphragm.
  2. This is a thickening of the fascia of the psoas muscle (This ligament is attached to TVP of L1)
• More laterally is the lateral arcuate ligament
  1. Has attachment from 12^th rib and TVP of L1.
  2. Is thickening of the fascia of quadratus lumborum.
  3. The diaphragm has attachments to both medial and lateral arcuate ligaments.
• Vertebrocostal triangle = lateral part of 12^th rib
  1. Not much skeletal muscle present here.
  2. A potential weak spot in the diaphragm.
  3. Herniation through the diaphragm often occurs at this point (present on both sides).

Structures passing through the diaphragm

1. Aortic hiatus (T12):
   • Aorta is bordered by the median arcuate ligament, thus, the aorta passes behind the diaphragm, not through it (does not move during inspiration).
   • Thoracic duct.
   • Branches of the azygous system also pass through, sometimes through aortic hiatus.
2. Caval hiatus/orifice for Inferior vena cava (T8):
   • fibers of the central tendon have opened.
   • contraction of these fibers helps with venous return.
   • passing laterally, have the right phrenic nerve. (left passes on its own)
3. Esophageal hiatus (T10): Esophagus along with anterior/posterior vagal trunks also passes through (moves during respiration.  inspiration dilates it and moves it inferiorly.)
4. Greater / Lesser splanchnic nerves pass through L/R  crus to enter the abdomen.
5. Superior epigastric arteries pass through the sternocostal hiatus (gap near costal margin)

Innervation of the diaphragm

1. Phrenic nerves are major innervation: from C3-5 contains both:
   • afferent- referred pain is to the upper part of the shoulder (indicates diaphragm irritation through contact with inflamed organ).
   • efferent- to muscle fibers.

1. The lateral portion of the diaphragm (last inch laterally) where attaches costal margin
   • afferents from intercostal/subcostal nerves give afferent innervation to the lateral portion.
   • Inflammation to the lateral diaphragm is perceived as lower rib pain / intercostal space pain.

Blood supply to the diaphragm

1. Right and Left internal thoracic artery 2 branches
   • Pericardio-phrenic artery – off of internal thoracic, runs on the internal surface of the pericardial sac. Inferiorly runs onto the diaphragm.
   • Musculophrenic artery- continuation of internal thoracic that supplies anterior region along costal margin.
2. Branches off of the aorta:
   • Superiorly: superior phrenic artery supplies the superior aspect as it comes off of the aorta before it penetrates into the diaphragm.
   • Inferior phrenic artery runs along (supplies) the inferior surface of the diaphragm.
3. Suprarenal is a branch off of the inferior phrenic

Also read:

1. The Diaphragm @ TeachMeAnatomy
2. Practice Anatomy tests for free!
3. Best Anatomy books for Medical students
4. Best Anatomy websites & journals
5. Anatomy syllabus in (CBME) in India
6. Anatomy syllabus in Russia & Other CIS
7. Anatomy syllabus in China

Also Watch:

• Diaphragm – Definition, Function, Muscle & Anatomy @ Kenhub

• Diaphragm @ Lecturio