Anatomy of the Thoracic Region (Nursing)

00:01 Now, let's talk a little bit about the bony support structure and protection of the pulmonary cavity, which is the ribs or the ribcage.

00:13 Anteriorly in the midline, we have this bone called the sternum or the breastbone.

00:19 And going from superior to inferior, it's broken up into a manubrium, a body, and ziphone process which is this very pointy part at the very inferior edge.

00:32 And in fact, ziphone means sword like, and manubrium means handle, and it was thought that the sternum sort of looks like an upside down sword hence how it got this name.

00:43 And attaching to the sternum laterally, are these cartilages called the costal cartilages.

00:49 And they are the cartilaginous portions of the ribs of the ribcage.

00:55 As you can see inferiorly, several of them merge to form the inferior border of the ribcage here, and that's called the costal margin.

01:10 Typically, there are 12 ribs on either side of the sternum.

01:14 And the first ribs, one through seven as they're numbered from superior to inferior, are often called true ribs because they all connect directly to the sternum via one of their costal cartilages.

01:29 However, ribs eight through 12, don't.

01:32 And so therefore, they're called false ribs.

01:35 For example, ribs 8, 9, and 10 have costal cartilages that attached to the rib above them, and therefore only indirectly attached to the sternum.

01:44 Furthermore, ribs 11 and 12 are sometimes called floating ribs because they have no attachment direct or indirect to the sternum.

01:56 The major muscle of breathing is the diaphragm, which is this very wide flat muscle that separates the thoracic cavity from the abdominal cavity.

02:08 And you can see there's a dome on the left and a dome on the right, but they're not exactly horizontal.

02:16 The dome on the right is a little bit higher up because of the presence of a very large organ called the liver.

02:23 Centrally, it becomes tenderness is something called the central tendon.

02:27 And it's also where we're going to find some structures that have to pass from the thorax into the abdomen are going to pass through.

02:36 So let's look at the act of inspiration and expiration.

02:40 Here we have the diaphragm as its beginning the process of inspiration.

02:46 As a muscle it's going to contract.

02:48 And as it's going to contract, it's going to expand the volume of the thoracic cavity, therefore reducing the pressure and that's going to cause the lungs to expand and pull in air from the outside environment.

03:05 Here, the lungs are fully inflated as the diaphragm has fully contracted.

03:11 And now it's the beginning of exhalation.

03:15 Now at this point, the diaphragm is going to relax but that's not really what's going to cause exploration or exhalation.

03:23 Exhalation is generally a passive process carried out by elastic fibers inside the lung itself.

03:31 So as soon as the diaphragm relaxes, the elastic recoil of the lungs themselves is what allows air to escape.

03:43 The diaphragm being a very important muscle, the body has some very important nerves, and there's a left and right phrenic nerve that actually travels down from the cervical area in the area of the C 3-4 spine area and travels through the space between the lungs called the mediastinum in order to innervate the diaphragm.

04:04 And that's a very long course.

04:07 And that all has to do with the embryologic development of the diaphragm.

04:11 But it's always important to keep in mind that the phrenic nerves can be damaged at any point from the neck where they originate all the way down to the diaphragm.

04:21 And any injury to the phrenic nerves would cause paralysis of one or the other side of the diaphragm.

04:28 Now let's talk about the pleura which is the wrapping of the lung lungs and the chest cavity.

04:34 The lungs here are covered by a very thin membrane called the visceral pleura.

04:40 Until we reach the hilum, at which point that membrane becomes attached to the surrounding chest cavity, at which point it's called the parietal pleura.

04:51 So the primal and visceral pleura are contiguous with each other.

04:55 But the visceral is attached directly to the surface of the lung, while the parietal pleura lines the surface of the chest cavity.

05:04 There's usually only a tiny amount of space between them called the pleural cavity, in which there's a tiny amount of fluid called the pleural fluid.

05:13 And this pleural fluid helps reduce friction between the lungs and chest wall during breathing.

05:20 Unfortunately, the way breathing works can lend itself to some pathologies in certain situations.

05:26 Because the diaphragm is relying on a sealed the chamber of this pleura, That's going to cause problems if that chamber is no longer sealed.

05:36 So for example, we said the diaphragm contraction increases the volume of the chest cavity, reducing the pressure in the lungs causing it to expand and pulls air in from the outside environment.

05:49 However, if via stabbing gunshot wound or other sorts of accidents or trauma, we were to have some sort of damage to the chest wall leading to a direct connection between the outside air and the pleural cavity, then there will be a problem whenever that pressure is reduced, because it would actually draw in air from the outside world into the pleural cavity, leaving less room or space for air to be drawn through the mouth down into the trachea and into the lungs.

06:22 And this is something called a tension pneumothorax.

06:26 And there's tension essentially from the outside air being forced into the pleural cavity and collapsing the lung on that side.

06:37 And essentially, the damage or connection between the outside air and the pleural cavity needs to be sealed in order for that lung to reinflate with air coming in through the trachea.