The diaphragm is a dome-shaped muscle that separates the thoracic and abdominal cavities. It has three origins - sternal, costal, and vertebral. It contains several openings, including the venacaval, esophageal, and aortic openings. The diaphragm contracts during inspiration, increasing the volume of the thoracic cavity. It receives motor innervation from the phrenic nerves and sensory innervation from intercostal nerves. The diaphragm can be involved in hernias such as congenital Bochdalek's hernia or hiatal hernia through the esophageal opening.

1. DIAPHRAGM
& MECHANISM 0F
RESPIRATION
DR. SUNDIP CHARMODE
ASSISTANT PROFESSOR

2. DEFINITION
• Dome shaped musculo-aponeurotic partition which intervenes
between the thorax and abdomen.

7. STRUCTURE
• The thoracic surface is convex on right and left sides (summit =
cupolae) and is depressed in the middle.
• The peripheral part is muscular and the central part is tendinous
which is occupied by the central tendon.

8. ORIGIN
• Three groups:
1. Sternal
2. Costal
3. Vertebral (Lumbar)

9. STERNAL ORIGIN
• By two slips from the back of the xiphoid process

10. COSTAL ORIGIN
• From the Inner surface of the lower six ribs and their costal cartilages
interdigitating with the transversus abdominis.

11. VERTEBRAL ORIGIN
• Arises from three sources:
1. From a pair of crura, right and left
2. From a pair of medial arcuate ligaments
3. From a pair of lateral arcuate ligaments

12. VERTEBRAL ORIGIN
RIGHT CRUS
• Arises from front of the bodies
and intervertebral discs of upper
three lumbar vertebrae
• Longer and more muscular
LEFT CRUS
• Arises from front of the bodies
and intervertebral discs of upper
two lumbar vertebrae

13. MEDIAN ARCUATE LIGAMENT
• Both the crura are connected across the middle line by a Median
arcuate ligament.

14. MEDIAL ARCUATE LIGAMENT
• Each ligament bridges across the front of psoas major and is formed
by the thickening of psoas fascia.
• Medially: Body of first or second lumbar vertebra
• Laterally: Tip of transverse process of first lumbar vertebra

15. LATERAL ARCUATE LIGAMENT
• Each ligament arches in front of Quadratus lumborum and is formed
by the thickening of anterior layer of thoraco-lumbar fascia.
• Medially: Tip of transverse process of first lumbar vertebra
• Laterally: Lower border of 12th rib

16. INSERTION
• All the fibers are inserted into the central tendon which is situated in
the median depressed part of the diaphragm close to the sternum.
• Central tendon: Trefoil leaf shaped presenting median, right and left
leaflets.

17. OPENINGS OF DIAPHRAGM
• Major openings:
• Vena-caval
• Esophageal
• Aortic
• Minor openings:

19. VENACAVAL OPENING
 Situation:
• Situated in central tendon at the junction of median and right leaflet.
• Opposite the disc between 8th and 9th thoracic vertebrae
• About 2.5 cm to the right of middle line.
 Shape: Quadrilateral

20. STRUCTURES PASSING THROUGH VENACAVAL
OPENING
1. Inferior vena-cava
2. Few branches of Right Phrenic Nerve
3. Few lymph vessels from the Liver.
 Effect of contraction: When diaphragm contracts in inspiration, vena-
caval opening dilates and more blood enters right atrium.

21. ESOPHAGEAL OPENING
 Situation :
• Situated in Muscular part of diaphragm
• Situated at 10th thoracic vertebrae
• About 1.25 cm to the Left of middle line.
 Shape: Elliptical in shape and is formed by splitting of fibers of the
Right Crus.

22. STRUCTURES PASSING THROUGH ESOPHAGEAL
OPENING
1. Esophagus
2. Anterior and Posterior Vagal Trunks (formed by Left and Right Vagus
nerves respectively)
3. Esophageal branches of Left gastric artery and corresponding
tributaries of Left Gastric vein.
4. Lymphatics from the Liver
5. Phreno-esophageal ligament

23. STRUCTURES PASSING THROUGH ESOPHAGEAL
OPENING
 Effect of contraction:
• It prevents regurgitation of food from the stomach to the
esophagus.
• During inspiration the opening is constricted hence inspiration and
deglutition can not take place simultaneously.

24. AORTIC OPENING
 Situation :
• Situated behind the diaphragm (Osseo-aponeurotic)
• Situated at the level of lower border of 12th thoracic vertebrae
• Slightly to the Left of median plane.
 Shape : Rounded in shape.

25. BOUNDARIES : AORTIC OPENING
• In front : Median Arcuate ligament
• Behind : Body of 12th Thoracic vertebra
• On each side : Corresponding crus

26. STRUCTURES PASSING THROUGH AORTIC
OPENING
1. Abdominal aorta
2. Thoracic duct
3. Sometimes Azygous vein
 Effect of contraction : No change

27. MINOR OPENINGS
• Each crus is pierced by Greater and Lesser splanchnic nerves.
• Sympathetic chain passes behind the Medial Arcuate ligament.
• Subcostal nerve and vessels pass behind Lateral Arcuate ligament.
• Right crus is sometimes pierced by Azygous vein.
• Left crus is usually pierced by Inferior hemi-azygous vein.

31. MINOR OPENINGS
• ‘Space of Larrey’ – A triangular gap is present between the origin of
diaphragm from xiphoid process and 7th costal cartilage, through
which Superior Epigastric vessels and some lymphatics pass. When
enlarged it is called ‘Foramen of Morgagni’.
• Between the digitations of costal origins of the diaphragm and
transversus abdominis – lower five intercostal vessels and nerves.

32. MINOR OPENINGS
• Between the costal origins of the diaphragm from the 7th and 8th
cartilages – Musculo-phrenic vessels

33. RELATIONS
 Superiorly :
1. Pleurae and lungs
2. Pericardium
 Inferiorly :
1. Peritoneum
2. Liver
3. Fundus of stomach
4. Spleen , Kidneys, Supra-renal glands

34. NERVE SUPPLY - MOTOR
• Phrenic nerves (Ventral rami of C3,C4,C5). Each phrenic nerve pierces
diaphragm, ramifies on abdominal surface and supplies the muscle.
• On abdominal surface it divides into:
i. Antero-medial
ii. Antero-lateral
iii. Postero-medial
iv. Postero-lateral

35. NERVE SUPPLY - MOTOR
 Right phrenic nerve: Supplies right part of diaphragm up to the right
margin of esophageal opening.
 Left phrenic nerve: Supplies left part of diaphragm up to the left margin
of esophageal opening.

36. NERVE SUPPLY - SENSORY
 Central part : Phrenic nerve
 Peripheral part : Lower 6 -7 Intercostal nerves
Sympathetic supply
• From Coeliac plexus via Inferior phrenic plexus

37. BLOOD SUPPLY
1. Musculo-phrenic and Peri-cardio-phrenic arteries: Branches of
Internal Thoracic artery.
2. Lower 5-6 Posterior Intercostal arteries
3. Superior phrenic artery: Branch of Descending thoracic aorta
4. Inferior phrenic artery: Branch of Abdominal aorta.
• Veins correspond with the arteries and drain into systemic veins.

38. ACTIONS
 On thoracic cavity: It is the principal muscle of inspiration
 On abdominal cavity: It is a compressor of abdominal viscera.
Increases intra abdominal pressure.
 On three major openings: Dilates IVC, constricts esophagus and no
effect on aortic opening.

39. APPLIED ANATOMY
1. Hiccough
2. Shoulder tip pain
3. Unilateral paralysis of diaphragm
4. Eventration
5. Diaphragmatic Hernia
• Congenital
• Acquired

40. DIAPHRAGMATIC HERNIAS
 Congenital hernia:
1. Retro-sternal Hernia – common on Right side
2. Postero-lateral Hernia – through a triangular gap called Costo-
vertebral trigone / Bockdalek’s traingle.
 Hiatal hernia : Through dilated esophageal hiatus

41. MORGAGNI HERNIA
• On rare occasions, foramen of Morgagni may be present due to
failure of sternal origin of the diaphragm. Abdominal viscera may
herniate into the thorax.

43. BOCHDALEK TRIANGLE
• Sometimes diaphragm fails to arise from the lateral arcuate ligament on
one or both sides forming a triangular gap – Costovertebral trigone
• A congenital diaphragmatic hernia takes place through that opening
and abdominal viscera herniate into the thorax due to intra abdominal
pressure.
• Bochdalek’s hernia is observed on left side usually.

46. HIATUS HERNIA
• Through dilated esophageal hiatus
• It consists of two types:
1. Sliding
2. Rolling

47. SLIDING TYPE HIATUS HERNIA
• More common
• Takes place when the gastro-esophageal junction slides into thorax
through the lax hiatus.
• Associated with acid regurgitation – heart burn

50. ROLLING TYPE HIATUS HERNIA
• The gastro-esophageal junction remains in normal position.
• The hernial sac containing usually the fundus of stomach projects into
the thorax by the side of esophagus (para-esophageal).
• Associated with nausea and dysphagia.

51. MUSCLES OF INSPIRATION
1. Diaphragm
2. Intercostal muscles
3. Erector spinae muscle
4. Scalene group of muscles
5. Pectoral group of muscles
6. Serratus anterior
7. Quadratus lumborum

52. MUSCLES OF EXPIRATION
1. Flat muscles of abdominal wall
2. Latissimus dorsii

53. THANK YOU