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The diaphragm is a curved musculo fibrous
sheet that separates the thoracic from the
pierced by structures that pass between
these two regions of the body.
primary muscle of respiration.
dome shaped and consists of a peripheral
muscular part and central tendinous part.
muscular part arises from the margins
of the thoracic opening and gets inserted
into the central tendon.
attachments to the thoracic wall are low
posteriorly and laterally, but high
Rarely affected by intrinsic diseases
complex embryological development is
subject to number of congenital
ORGIN IN VERTEBRAL , COSTAL
AND SPINAL ATTACHMENTS FROM
WHICH MUSCULAR FIBERS CURVE
UPWARDS AND INWARDS FROM
PERIPHERY TO BE INSERTED INTO
THE FIBROUS SHEET CALLED
Develops from 4 sources
Medial dorsal portion of primary oesophageal
Marginal ingrowths of the body wall
Third week of devpt.
Mass of mesoderm situated cranially to
the pericardial cavity
Contributes to the ventral portion like the
sternal and costal parts
Is a paired dorsolateral portion
Fuses with dorsal mesentry of oesophagus
and dorsal portion of the septum transversum
to complete the partition between thorax &
Forms the primitive diaphragm at 7th wk of
Medial portion of the diaphragm
From the medial dorsal portion of
primary oesophageal mesentry.
Fuses with septum transversum &
Curves of diaphragm – develop from
growth of muscle fibres into the dorsal
mesentry of the oesophagus.
At 9-12 th week , the souce is
contributed by – the marginal outgrowth
of the body wall.
these contibutions from thoracic
myotome contain nerve fibers of lower
six or seven intercostal nerves -
distribute the sensory fibers to periphery
At the 5 th week , nerve fibers from the
3rd, 4th & 5th cervical segments of spinal
cord grow into septum transversum, via
the pleuropericardial membrane to form
the PHRENIC NERVE
At the 8th week – diaphragm attached to
dorsal body of 1st lumbar vertebrae,
giving rise to the domed contour
character of the diaphragm.
Origin of the diaphragm
sternal part- arising from the posterior
surface of the xiphoid process.
costal part arising from the deep
surfaces of the lower six ribs and their
costal cartilages & forms the right & left
vertebral/lumbar part arising from upper
three lumbar vertebrae; forms the right &
left crura & the arcuate ligaments.
Crura:The right crura is from the bodies of
first three lumbar vertebrae. The left crus,
from the bodies of first two lumbar
Arcuate ligaments:Lateral to the crura
on both sides.
Medial arcuate ligament is thickened
upper margin of fascia that covers the
Lateral arcuate ligament is thickened
upper margin of the fascia covering the
quadratus lumborum muscle.
Shape of the Diaphragm
It is studied as
(b)Right & left crus
(c)Right & left dome
Insertion of the Diaphragm
The diaphragm is inserted into the central
tendon that is trifoliate (like three leaves).
On the superior side, the surface of
the tendon is partially fused with the
Some of the muscle fibers of the right crus
pass up to the left and surround the
esophageal orifice in a slinglike loop.
These fibers appear to act as a
sphincter and possibly assist in the
prevention of regurgitation of the
stomach contents into the thoracic part
of the esophagus.
After forced expiration the right dome is
level anteriorly with the fourth costal
cartilage and therefore the right nipple,
whereas the left dome lies
approximately one rib lower.
With maximal inspiration, the dome
will descend as much as 10 cm, and on
a plain chest radiograph the right dome
coincides with the tip of the sixth rib.
body is lying on one side, the dependent half
of the diaphragm will be considerably higher
than the uppermost one.
higher in short, fat people than in tall, thin
Overinflation of the lung, as occurs for
example in emphysema, causes marked
depression of the diaphragm.
Functions of the Diaphragm
Muscle of inspiration: On contraction the
diaphragm pulls its central tendon down
and increases the vertical diameter of
the thorax. The diaphragm is the most
important muscle used in inspiration.
Muscle of abdominal straining: The
contraction of the diaphragm assists the
contraction of the muscles of the anterior
abdominal wall in raising the intra-abdominal
pressure for micturition, defecation, and
Weight lifting muscle: In a person taking a
deep breath and holding it (fixing the
diaphragm), the diaphragm assists the
muscles of the anterior abdominal wall in
raising the intra-abdominal pressure.
Thoraco-abdominal pump: The descent of
the diaphragm decreases the intrathoracic
pressure & increases the intra-abdominal
This compresses the blood in the inferior
vena cava and forces it upward into the
right atrium of the heart.
Within the abdominal lymph vessels is also
compressed, and its passage upward within
the thoracic duct is aided by the negative
intrathoracic pressure. The presence of
valves within the thoracic duct prevents
three main openings.
The caval opening lies at the level of the
T 8 vertebra in the central tendon.
It transmits the inferior vena cava and
terminal branches of right phrenic nerve.
Openings in the Diaphragm
The esophageal opening lies at the level
of the T 10 vertebra in a sling of muscle
fibers derived from the right crus at the
left of median plane.
transmits esophagus, left and right
vagus nerves, esophageal branches of
the left gastric vessels and lymphatics
from lower third of the esophagus.
The aortic opening lies anterior to the body of
the T 12 vertebra between the crura.
transmits aorta, thoracic duct and azygous
Other minor openings
Sympathetic trunk (pass posterior to the
medial arcuate ligament on both sides).
Superior epigastric vessels (pass
between the sterna and costal origins of
the diaphragm on each side).
Left phrenic nerve (pierces the left dome
Neurovascular bundles of lower six intercostal
spaces (pass between the muscular slips of
costal origin of diaphragm)
Lower five intercostal and subcostal
arteries- supply the costal margins of
Phrenic arteries- supply the main central
portion of the diaphragm.
The phrenic veins follow the
corresponding arteries on the inferior
Nerve supply of diaphragm
sensory supply of the central tendon of
diaphragm that is covered by parietal and
peritoneal pleura is from phrenic nerve.
Sensory supply to the periphery of
diaphragm is from lower six intercostal
The motor nerve supply of diaphragm is
only from the phrenic nerve.
descends anterior to the pulmonary hilum,
between the fibrous pericardium and
mediastinal pleura, to the diaphragm,
accompanied by the pericardiophrenic
supplies sensory branches to the
mediastinal pleura, fibrous pericardium and
parietal serous pericardium.
The right phrenic nerve is shorter and more
vertical than the left