How many abs exercises categories are there?!

How many abs exercises categories are there?

How many abs exercises categories are there? I know there are upper and lower abs exercises, but I was wondering if these are all.

And can someone give me a list of the best abs exercises for each category? Because I want to do abs workouts 4 days a week with each day devoted to a certain part of the abs.

Thanks

The list below are the areas of the abs. At the end of each section are some sample exercises:

Obliques (Internal and External). Your obliques are located on the side and front of your midsection, right around your waist. The internal obliques are located just below your external obliques. As you can see in the picture, the internal obliques cross the external obliques diagonally. The obliques are responsible for twisting movements and bending at the side.

Exercises: Oblique Crunch on Exercise Ball, Russian Twist

Rectus Abdominis. For most people, this muscle is the one that they are thinking of when they say they want six pack abs. This pair of muscles runs along the front of the abdomen and is separated vertically by the linea alba. It is crossed by 3 or 4 fibrous bands called the tendinous inscriptions. These bands are what produces the six pack when the abdominal region is well defined. This is the muscle that makes up what people call the upper and lower abs.

Exercise: Standard Crunch on Exercise Ball, Hanging Leg Raises, Cable Crunch

Transverse Abdominis. The Transverse abdominis is the depest muscle in the abdominal region and is located just under the internal oblique muscle. Though you cannot seen the tranverse abdominis, it acts as a "corset" to help hold your stomach flat and aid with pelvic stability. Not only will this muscle help with definition for your six pack abs, but it will also help you to use more weight in all of your lifts, due to its "weight belt" effect.

Exercise: Vacuum

These three groups of muscles make up your six pack abs. However, there is one other group of muscles that should not be ignored to round out your core muscles.

Erector Spinae. The Erector Spinae is a collection of three muscles running from your neck to your lower back. The are called the splenius, logissimus, and the Iliocostalis. These muscles act to extend your back and are important for overall posture. Working these muscles balances the work you are doing with your abdominal muscles and should be worked when performing your ab workout.

Exercise: Back Extentions on Exercise Ball