Introduction to Abdomen (Nursing)

by Darren Salmi, MD, MS

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    00:01 Now we're going to talk about the abdomen, which contains many important organs.

    00:07 But before we get to those organs, we're going to talk a little bit about the abdominal wall muscles that surround and protect the abdominal cavity.

    00:16 In addition to surrounding protecting these important organs, the abdominal wall muscles themselves have some important functions, including very flexible movements of the trunk, as well as things like forced exhalation, because if you think about it, a very rapid contraction of your abdominal wall muscles is going to push the diaphragm up very quickly.

    00:39 For example, coughing is something that we can thank the abdominal wall muscles for.

    00:46 So let's start by looking at the outermost muscle, called the external oblique.

    00:52 External because it is the most external and oblique because of the orientation of the fibers that are running diagonally.

    01:00 Just deep to the external oblique, we have the internal oblique, which as the name implies, is just deep or more internal to the external oblique.

    01:10 Although in this case, the oblique fibers run in the opposite direction of the external obliques.

    01:17 We also have deep to the internal oblique, a muscle that has fibers running transversely, hence the name transversus abdominus.

    01:27 And then on either side of midline, we have a muscle running up and down longitudinally called the rectus abdominus.

    01:35 And rectus means straight, hence why it gets that name as opposed to oblique.

    01:41 And if we were to remove the external oblique, we could actually see the bottom part of the ribcage that we call the costal margin here.

    01:51 And within the rectus abdominus itself, we have these little tenderness intersections that break it up into separate muscle bellies.

    02:01 And that's actually what's responsible for what's commonly called the six pack.

    02:05 And those tenderness intersections can vary a number from two to five, so it can vary how many individual muscle bellies can be seen on a person.

    02:14 In the midline, connecting all of these muscles to a very thick sheet of connective tissue is something called the linea alba.

    02:23 Linea alba means white line and it's a white line because it's essentially just connective tissue.

    02:30 And there's no muscle at this point.

    02:32 And it's going to run all the way from the sternum down to the pelvic bones never really helped bridge the space between the thorax and the pelvis.

    02:45 Superficially, there are a lot of surgical incisions that take place through the abdominal wall muscles.

    02:53 For example, just along that costal margin, we might have an anterior subcostal incision, which on the right side might be something for a gallbladder surgery.

    03:04 Also, on the right side, about a third of the way from the pelvic bone to the umbilicus, or belly button, there's something called McBurney's point where you would find the appendix and that's where you would find or make the McBurney incision.

    03:21 There may also be incisions down in the crease area at the inferior edge of the abdomen called the inguinal area and that's where you might make inguinal incisions for for example, inguinal hernias.

    03:34 There's also a more horizontally shaped incision called the Pfannenstiel incision for pelvic organs and surgeries such as C-sections or cesarean sections.

    03:45 And then a lot of incisions are going to be through the midline through that connective tissue structure called the linea alba.

    03:51 And that's because linea alba again means white line and it's white because there's no blood vessels there.

    03:58 So you can make the incision through the linea alba without cutting through really any sort of arteries or veins.

    04:06 If we look at a sagittal view here, we can see some of the body cavities.

    04:12 Anteriorly, we have the thoracic cavity and the abdominal cavity separated by the diaphragm and then more inferiorly we have the pelvic cavity.

    04:23 Now there's no separation between the two like there is between the abdomen and thorax.

    04:29 And so sometimes the abdominal cavity and pelvic cavity are referred to as the abdominal pelvic cavity because they are continuous.

    04:35 Although, developmentally, we really had all one single cavity called the ventral cavity until the diaphragm actually separated abdomen from thorax.

    04:47 Posteriorly, we sometimes think of this folding events of development as creating the cranial cavity and the spinal cavity and call these together the dorsal cavity.

    05:01 Now we're going to talk about the lining of the abdominal cavity as well as the surface of abdominal structures, something called the peritoneum, which is exactly the same as the pleura.

    05:14 Both in how the terminology is referred to but also in its actual makeup because the pleura and peritoneum were the same thing until the diaphragm came along to separate the thorax from the abdomen.

    05:27 So just like with the pleura, the peritoneum that lines, the abdominal cavity itself is called the parietal peritoneum.

    05:37 And just with visceral pleura, visceral peritoneum is the peritoneum that's on the surface of these abdominal organs themselves.

    05:47 And the space between them is called the peritoneal cavity.

    05:51 Usually filled with a small amount of peritoneal fluid produced by the peritoneum.

    05:58 Here's a cross section view where we can see the peritoneum lining again the abdominal cavity.

    06:06 And we see that there are a lot of structures that sit posterior to the peritoneal cavity.

    06:14 So they're not actually within this peritoneum.

    06:16 We call those collectively the retroperitoneum because they're behind the peritoneum.

    06:25 And organs in that area will be called retroperitoneal, whereas things like the small intestine, for example, actually sit within this cavity surrounded by visceral peritoneum and we call those intraperitoneal.

    06:37 Again, things like the superior vena cava, or the aorta, or the kidney aren't and therefore they're called retroperitoneal.

    06:50 Again, we have the parietal peritoneum that actually connects and is continuous with the visceral peritoneum through various connections or folds that get different names called mesentery, or omentum, or ligaments even.

    07:05 But they are connected they are continuous, just like visceral and parietal pleura we're.

    07:12 In for example, something called the mesentery is a little fold of that visceral peritoneum that will come off.

    07:18 For example, a piece of small intestine and actually connect to and be continuous with the posterior body wall and its parietal peritoneum.

    07:27 And again, the peritoneal cavity is what's left of the space between visceral and parietal peritoneum.

    07:35 Another form of mesentery or visceral peritoneum that sort of comes off in organ is the first thing you would see if we were to open up the abdominal wall to look into the abdomen, the abdominal cavity per se, and that would be this apron of fat called the greater omentum.

    07:54 And we see here a horizontally oriented piece of colon we're going to talk about later called the transverse colon.

    08:01 That essentially this apron of fat is attaching to.

    08:05 The greater omentum comes down and is actually unconnected down at this inferior edge you can see and then connects posteriorly to the transverse colon after having been connected to parts of the stomach.

    08:20 The important thing to note about this greater omentum is that it is a loose flapper apron that can be retracted to reveal the underlying abdominal organs behind it, which is what we're going to look at in the next sections.

    About the Lecture

    The lecture Introduction to Abdomen (Nursing) by Darren Salmi, MD, MS is from the course Anatomy of the Gastrointestinal System (Nursing).

    Included Quiz Questions

    1. External oblique
    2. Internal oblique
    3. Transversus abdominis
    4. Rectus abdominis
    5. External lateralis
    1. Connective tissue
    2. Muscle
    3. Bone
    4. Hyalin
    5. Yellow marrow
    1. McBurney incision
    2. Anterior subcostal
    3. Inguinal incision
    4. Pfannenstiel incision
    5. Midline incision
    1. Small intestine
    2. Kidney
    3. Aorta
    4. Vena cava
    5. Adrenal gland

    Author of lecture Introduction to Abdomen (Nursing)

     Darren Salmi, MD, MS

    Darren Salmi, MD, MS

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