Once again, you will use the cross sections for identifying and learning some of these muscles. When directed, locate and click on the cross-sectional anatomy. This will highlight it in the cross section area AND add/highlight it in the dissection area. Essentially, you will build your model by adding muscles to the skeleton. Pretty cool, eh?
This dissection should cause you to "sit up" and take notice of a few more muscles. The anterolateral abdominal wall is composed of skin, fascia, and four muscle pairs: the external oblique, internal oblique, transversus abdominis, and rectus abdominis. As you'll soon see, the first three are arranged from superficial to deep.
Locate each of the following in the cross section area by "mousing over" the anatomy and clicking to select it. Notice that you "add" the structure to the specimen on the right. I want you to locate and add these in the order shown below. These muscles are arranged from deep to superficial so you will be adding them from the inside out.
These anterolateral abdominal muscles help contain and protect the abdominal viscera. They are also responsible for abdominal flexion and rotation. Additionally, they compress the abdomen during forced exhalation and produce the force required for defecation, urination, and childbirth. (PLEASE realize I'm drawing no analogy there! It just happens to be an anatomical coincidence! :-) )
The following sheet-like tendons enclose each of these muscles and form the rectus sheaths, which enclose the rectus abdominis muscles, too. The muscles have been dissected away just leaving these aponeuroses for easier observation.
Your specimen now has both the muscles AND the aponeuroses in place. Identify each muscle and its corresponding aponeurosis. As you just learned, you'll need to start with the superficial muscles and aponeuroses and dissect them away to reveal deeper layers.
The inferior free border of the external oblique aponeurosis along with some additional collagen fibers, forms the inguinal ligament. It runs from the anterior superior iliac spine to the pubic tubercle. The inguinal canal is the opening through the aponeurosis that passes the ilioinguinal nerve. In males, this canal is larger and contains the spermatic cord. In females it contains the uterine round ligament. Rotate your specimen to a lateral perspective to get a better view of the inguinal ligament's attachments.
An inguinal hernia is a rupture or separation of a portion of the inguinal area of the abdominal wall resulting in the protrusion of a part of the small intestine. This is much more common for males because the inguinal canal is larger making this an especially weak point in the abdominal wall.
Several muscles are involved in breathing. The three primary muscles are listed below. Identify the following:
Dissect away both sets of intercostals to more fully reveal our next muscle.