Thoracic Diaphragm

00:01 So now let's move on to the diaphragm, which is a really important muscle parts of respiration.

00:07 We can see the diaphragm has this very broad, flat, central tendon.

00:12 So it's unlike other muscles that we've just described.

00:15 But it's similar to say muscles like the external oblique muscles, internal oblique muscles that don't have a fine tendon that inserts into a muscular point, but has a flat sheath.

00:27 And here we can see a very similar flat sheath.

00:29 And in the diaphragm, we call it the central tendon.

00:33 The muscle fibers coming from the thoracic cavity which we can see here from the thoracic cage, they converge towards this central tendon.

00:43 We can see passing through the central tendon and some of the muscle fibers posteriorly, towards the vertebral column, we have a number of openings.

00:52 Here we have the caval opening at the level of the 8th thoracic vertebra.

00:57 And this is important for the inferior vena cava to pass up through the diaphragm and into into the heart.

01:04 We also have passing through this spake the right phrenic nerve and this passes through this carval opening.

01:11 We have the esophageal hiatus as well.

01:14 And this is at the level of the 10th thoracic vertebra.

01:18 And this is where the esophagus passes through the diaphragm to go and blend with the stomach.

01:23 We also have both vagal trunks the anterior and posterior vagal trunks leaving the posterior mediastinum of the thorax and passing through this opening to go and provide parasympathetic innovation to the abdominal organs.

01:37 Finally, and the most inferior of these openings within the diaphragm is the aortic hiatus, and this occurs at the 12th thoracic level.

01:46 Passing through the aortic hiatus is the abdominal aorta.

01:50 We also have the thoracic duct that passes through this space as it ascends again within the posterior mediastinum of the thorax.

02:00 So now let's have another look at the diaphragm.

02:01 This time looking at it anteriorly.

02:03 And projecting onto this posterior aspect of the abdominal wall.

02:07 Just at the inferior boundary of the diaphragm.

02:11 You can see surrounding the aortic hiatus we have a right and a left crew.

02:16 And these are extensions of diaphragmatic muscle that extend down onto the vertebral column.

02:22 We can see running over the top and reinforcing this opening is the median arcuate ligament.

02:28 And the aortic hiatus is formed here with the aorta running through it.

02:33 We also then have another couple of ligaments.

02:35 Here we have the medial and the lateral arcuate ligaments and these allow the psoas major and quadratus lumborum muscles respectively, to pass through and go on to their attachments.

02:47 Here we can see a lumbar part of the diaphragm.

02:49 And this is an essential part as it runs around the lumbar vertebrae.

02:54 So we can see the diaphragm and it has two domes.

02:58 It has a dome on the right hand side which is slightly higher than that found on the left due to the presence of the liver on the right.