Muscles of the Anterior Abdominal Wall – 3D Anatomy Tutorial

Muscles of the Anterior Abdominal Wall – 3D Anatomy Tutorial

Okay! So this is a tutorial on the muscles
of the abdominal wall. So I’m going to do this in two parts. The first part will be
on the muscles of the anterior abdominal wall and the second part will cover the muscles
of the posterior abdominal wall. So the muscles of the abdomen have several
different functions. They protect the viscera, which are the soften organs contained in the
abdominal cavity. They assist in breathing. In inspiration, the abdominal muscles relax
and allow the thoracic cavity to expand downwards. And in expiration, these muscles can contract
and push the viscera upwards. And also, contraction of these muscles is useful in coughing and
throwing up. Another function is to assist in defecation,
urination and giving birth. These are assisted by increasing the intra-abdominal pressure.
The pressure inside the abdominal cavities increase by a contraction of these muscles
and this can help force things out of the body like urine, feces and babies. So in the anterior abdominal wall, you’ve
got five muscles. These are all innervated by the anterior rami of spinal nerves T7-L1.
So you’ve got the rectus abdominis, the pyramidalis, the external oblique, internal oblique and
transversus abdominis. So I’ll just take you through these muscles now. So first, we’ve got this muscle here lying
right in the midline. It’s a paired muscle, which are separated by this white line running
down the middle. This white line is called the linea alba and this literally means ‘white
line’ in Latin. This linea alba is formed by the aponeurosis of the various abdominal
muscles. So the lateral three muscles (which I’ll come on to talk about), the external
and internal obliques and the transversus abdominis form this flat tendinous sheath
called aponeurosis which join together in the midline forming this linea alba. This
separates the two sides of the rectus abdominis muscle. So I’ve just isolated the muscle and we’ll
take a look at the origin and the insertion. The rectus abdominis muscle originates on
the pubic symphysis and pubic tubercle. Superiorly, it inserts along the costal margin (so the
costal cartilages) and also on the xiphoid process. So you can see the xiphoid process
here. So what this muscle does is it can flex the
vertebral column and it’s also involved in the other functions I mentioned at the start
of this tutorial. So a couple of other things to just point
out. You can see another white line which lies on the edge of the rectus abdominis muscle
on either side. This is called the linea semilunaris. And then you can see these horizontal intersections
which separate up the muscle bellies of the rectus abdominis. These are called tendinous
intersections. This can be seen on people who have low body fat and a lot of muscle
mass in the rectus abdominis. You can see in this picture the sort of surface
anatomy. You can see the linea alba down the midline and you can visualize the tendinous
intersections between the muscle bellies of the rectus abdominis. So the second muscle which lies anteriorly
in the abdominal wall is called the pyramidalis muscle. This is a tiny little muscle and it
isn’t always present. It attaches to the pubis inferiorly and in the midline, it attaches
to the linea alba. This muscle is innervated by the anterior ramus of T12, spinal nerve
T12. So I’ve just switched over a diagram to show
you this. What we’re looking at is the left side. This left side has been dissected away
and you can see one-half of the rectus abdominis muscle (so the right side of the rectus abdominis
muscle. Just at the bottom — so this is the pubis here and in the midline, you’ve got
the linea alba — the pyramidalis is this tiny little muscle here, which attaches from
the pubis to the linea alba. These two muscles, the rectus abdominis and
the pyramidalis muscle are actually enclosed in something called the rectus sheath. This
is a tendinous sheath formed by the aponeurosis of the three lateral muscles, which I’ll come
on to talk about next. So the upper three-quarters of the rectus
abdominis — so this area that I’m showing you here. The upper three-quarters are fully
enclosed by this rectus sheath, whereas the bottom quarter is actually — so only the
anterior surface is covered by the rectus sheath. So what I’m going to do now is I’m going to
switch over to a cross-section to show you this rectus sheath. So we’re now looking at a cross-section. This
is anterior. So you’ve got the rectus muscle (both half of the rectus muscle) and in the
middle, you’ve got the linea alba. And then laterally, you’ve got the three muscles, lateral
muscles, which I haven’t talked to you about yet. But just briefly, you’ve got the outer
muscle called the external oblique. The muscle below that is called the internal oblique.
And the innermost muscle is called the transversus abdominis. So as you can see, these muscles form this
flat tendon, which is known as an aponeurosis. So the aponeurosis of these three muscles
enclose the rectus abdominis muscle in what is called the rectus sheath. These aponeurosis
meet at the midline to form the linea alba. So this is a cross-section taken from the
upper three-quarters. So you can see how both surfaces of the rectus abdominis are enclosed.
So the anterior surface is covered; and so is the posterior surface. You can see how
the internal oblique splits. So it passes anteriorly and posteriorly behind the rectus
abdominis. So this next picture I’m showing you is from
the lower quarter, so the bottom quarter of the rectus abdominis muscle. You can see that
this sheath is slightly different because it doesn’t go behind the rectus abdominis
muscle. All three aponeurosis pass in front along the anterior surface of the rectus abdominis
muscle. So next we’ve got the muscles which sit laterally.
You know what these are. There are three muscles — the external oblique, internal oblique
and transversus abdominis (from superficial to deep). So first is this muscle here, the external
oblique. This muscle originates on ribs 5-12, which you can see here. It inserts inferiorly
on the iliac crest, the pubic crest and pubic tubercle in this area here. It inserts on
the midline on the linea alba and also on the xiphoid process up here. So you can see
how this muscle forms this flat tendon, which is called an aponeurosis. And you saw how
this aponeurosis surrounded the rectus abdominis muscles to form part of the rectus sheath. So the external oblique on either side joins
together in the midline, fuses to form the linea alba, which I showed you earlier. So if both muscles contract, it can flex the
trunk. But if one side contracts, it can laterally flex the trunk. It can flex the trunk to the
same side. The fibers of the external oblique pass inferomedially.
They pass downwards and towards the midline in this direction. So if we just remove the external oblique,
we’ve got the internal oblique which lies below it. These fibers pass in the other direction.
So they pass superiorly and medially. So one way of remembering the direction that
the fibers are oriented is to use the mnemonic ‘hands in pockets, hands on tits’. So how
does this help you to remember? So if your hands are in your pockets, imagine
your hands kind of like this. Pockets has the letters ‘e’ in it for external oblique.
The direction your forearm is the direction of fibers, so in this direction. For the external
oblique, you’ve got your hands in pockets, pockets has an ‘e’, external oblique. So the
fibers are in the inferomedial direction. Hands on tits — sorry for being crude, but
that’s the mnemonic — ‘hands on tits’, they’re up in that direction, so the fibers pass superiorly
and medially. So ‘tits’ has an ‘i’ in it, so ‘internal’ oblique. So the fibers are superomedial. So just going back to the external oblique
muscle, there’s one important thing I forgot to tell you about. The bottom part, the inferior
margin of the aponeurosis of the external oblique muscle actually forms the inguinal
ligament. I’ve just isolated it here and you can see
the bottom part of the aponeurosis forming this ligament, which runs from the anterosuperior
iliac spine here down to the pubic tubercle. That’s important to remember. Just going back to the internal oblique (and
you now know which direction the fibers pass), the internal oblique muscle originates on
the iliac crest and also on the lateral part of the inguinal ligament. And it inserts on
the lower ribs. So you can see these ribs, 10-12 (or bottom four ribs, 9-12) and it also
inserts in the midline in the linea alba. So it joins the other aponeurosis as you know.
And it also inserts in the pubic crest here. So the aponeurosis isn’t shown here, but you
know that it extends into the midline and joins the linea alba. So similar to the external oblique, when both
of the internal oblique muscles contract, it flexes the trunk. So it brings the truck
like this. And if one side, one muscle contracts, it laterally flexes the trunk. It brings the
trunk to the same side. So the last muscle we’ve got is the transversus
abdominis muscle. If I just remove the internal oblique, we’ve got this muscle that sits underneath
it. It’s called the transversus abdominis muscle because the fibers are oriented transversely,
so horizontally like this. Let’s just take a look at the origin. It originates
on the iliac crest (so you can see that here) and also on the lateral parts of the inguinal
ligament. And also, you can see the origin at the top on the costal cartilages. And then
again, it inserts on the linea alba and inferiorly, it inserts on the pubic crest. You can see its attachments here. So iliac
crest. The inguinal ligament is gone, but it attaches on the lateral part of the inguinal
ligament over here. It attaches on the costal margin and it attaches in the midline at the
linea alba and also inferiorly at the pubic crest. So those are the muscles of the anterior abdominal
wall. It’s pretty easy. You’ve just got five to remember. You’ve got two which sit anteriorly.
You’ve got the large rectus abdominis and you’ve got the tiny little pyramidalis. And
then you’ve got the three lateral muscles (the external and internal oblique muscles
and the transversus abdominis muscle).

Comments (100)

  1. Why there is no deep fascia on abdominal wall but we call superficial fascia divisible into two parts like scarpas and fatty layer of fascia. instead ?

  2. Thanks a lot for making these videos ! They are the only reason i am not flunking anatomy =p

  3. hands on tits. thats fucking gold. thanks!

  4. you are a much better teacher than my textbook! thank you!

  5. Hands on tits! HAHAHA! You said it so seriously I lost it! HAHAHA! Thanks!

  6. You teach anatomy better than medical school faculty.

  7. You're saving my life/grades here at the moment, mate. Good on you xD

  8. I never understood anatomy this well! Thank you

  9. wtf are there  8 ab muscles?

  10. In my anatomy book there seems to be these muscles too: M. quadratus lumborum and M. iliopsoas with 3 parts: psoas major, minor and psoas iliacus. Is this more related to the abdominal cavity and that is then the reason why it's not mentioned or is there another reason? Hope to get an answer.

  11. This is very useful! I'll go and throw my gray's anatomy book into the trash right now!

  12. externus and internus, how about opposite rotation? c'mon!?

  13. "..and this can help force things out of the body like urine, feces, and… babies"

  14. thank you so much very helpful

  15. Hey, I find these videos extremely helpful. One thing though, I think it might be a mistake? The external and internal oblique muscles have their origins on two opposite sides, the more of the upper, costal cartilages for the external whereas the internal oblique originate on the iliac crest with their fibers pointing in quite the opposite direction. Doesn't this mean that they can't both have the same function of flexing the spine? wouldn't one be flexion of the spine and the other flexion of the hip towards the spine? which is which? Would appreciate a little bit of clarification for this, thanks!

  16. I couldn't stop myself from laughing at the part where you said "and….babies". Was it intended? LOL. Nonetheless, thanks a lot for this tutorial. I do hope that I pass my test on Anatomy tomorrow. fingers crossed

  17. It's pretty helpful and not too long. Thank you. 🙂

  18. no tits = no internal obliques

  19. What color are the tendons?

  20. omg that moment when he showed the guido xD

  21. Bwa ha ha ha! Love the mnemonic for the fibers of the internal/external obliques!!

  22. your are genious!!! I remember EVERYTHING

  23. I didn't see were the pyramid muscle is

  24. Hands in pockEts. Hands on tIts. I'll never confuse the direction of the muscles again 😀 Thank you

  25. this is helping me a lot! your words r easy to comprehend. thanks a lot! You got lectures on Head and neck too?

  26. Love these tutorials, you make them easy to remember, thanks!

  27. what is the connection of diaphragm and lower abdominal?

  28. You r the best man..
    Hands on tits lol…girls will love this lesson.

  29. wow ! I was lost until watching your video !
    thanks a lot !!
    I hope you keep up this amazing work so that help people 😀

  30. very helpfull. thank you 🙂 keep up the good work

  31. Instead of saying superior 3 quarters and inferior 1 quarter of the rectus abdominus, you can use the Anterior Superior Iliac Spine (ASIS) as a reference point for explaining that there is a rectus sheath anteriorly and posteriorly above ASIS and only anteriorly below ASIS

  32. Thanks so much. This was an excellent explanation!

  33. you make anatomy so easy ..thumps up

  34. I liked the real picture of the ab comparison

  35. one little mistake:
    the m. rectus abdominis ORIGINATES at the xiphoid process and 5th-7th rib and INSERTS at the symphsysis

  36. Are the DIAGRAMS from an atlas, or ?

  37. urine,feces and babies lol that cracked me up almost sounded like babies are just waste products hahaha!

  38. What muscle are used doing sneezing?

  39. Hi Peter. Have been following your work for a few years now. Great stuff. Can you please post a video demonstrating how the right external oblique and the left internal oblique lead to rotation of the trunk to the right.

  40. Thank you so much! Have watched far too many videos trying to find information on the transversus abdominis and none of them were of any use. Your video is the exact correct balance between technical and common language and brilliantly informative.

  41. trumps wallllllll!!!!!!!!!!!!!!!1

  42. Amazing Explanation

  43. lmao. classic. you say tits for internal obliques, how about gEnitals for external obliques hahahahahahhahahahaha. love your vids. keep up the great work, I'm learning so much.

  44. its very useful, you make them easy to remember thanks!!!

  45. I could not imagine in my life that I would be a student of medical sciences and would find the great teacher by great communicative source of USA electronic media. I appreciate and praise from the deep of my heart that may almighty Allah increase and develop the knowledge of Americans so we be able to get knowledge from the great teachers and provide health services to the humanity easily after watching these great collections…..thank you YouTube and all teachers and organizers who did this great act of kindness. In the last of my comment I thank of this teacher really  has used easiest way  and really he has given very approachable methodology. I salute your way of teaching.

  46. It's so useful to study abdominal muscles. Thank you so much! But I have a question, 'Origin' and 'Insertion' you said in the video means the muscle's direction? I mean that the muscle contracts from 'origin' into 'insertion' is right?

  47. Hands on tits 😂

  48. Thank you so much. It was very helpful

  49. your saliva is so annoying

  50. ausum brilliant fabuls

  51. best video thank you sir

  52. What type of tissue is sheath made of? Is it possible that the sheath get thicker or stronger over time and with certain training? Can it cover or inhibit the definition of the rectus abdominus muscles?

  53. I used your tutorials when studying for Pilates exam. Thanks. Very helpful. You mentioned action of the obliques during flexion and lateral flexion. I would love to see rotation: comparing opposite sides and internal vs external during rotation.

  54. am i the only one who thinks his voice sounds kinda like sam claflin haha

  55. You forgot most important function, pushing, pulling, lifting etc thats daily body functions and oh, belly dancing

  56. Thank you soo much!!!!

  57. Now I know all the muscles missing from my six pack

  58. The best demonastration which outstanding explaination

  59. Can u please do lecture on inguinal canal , peripheral nerve courses.
    U are too amazing Sir. Thank you sir.

  60. Superb explanation..very easy to understand

  61. i am passing anatomy lab because of you

  62. thankyou so muuuch fellas

  63. I lost it at urine,feces and babies. A really good video though

  64. Raise ur voice pls

  65. Best!👍 Thankyou!!

  66. Loved this video, very helpful indeed. Lots of love all the way from India.

  67. Bir de yutkunmaların olmasa… Anlatımdan önce git bir su iç boğazını temizle arkadaşım.

  68. Urine, feces, babies stuff was so proffessional and yet so funny.
    But the "tits" mnemonics was so vague and impracticle. At least it was kind of funny because of the surprising jargon.

  69. Amazing how God designed the human body! He definitely knew what he was doing!

  70. I'm 32 and I can't keep from laughing every time he says rectus

  71. You could have said hands on heart! Shame you used such a derogatory word, a little respect to those parts of the body that have enabled all living mammals to survive their first months/years of life!!!

  72. Am I dumb or the sound is not good

  73. your explanation was concise and simple thanks

  74. 3:48 – is that zyzz?!

  75. Can anyone else see the face in the middle of the external obliques? 8 minutes or so into the video? There’s also another, alien, looking face below it! Maybe I need to stay off the mushroom coffee 🍄?

  76. thank you.. its very helpfull 🙂

  77. Thank you so much about this amazing video👏👏👏

  78. You are very amazing thanks 🙏🙇

  79. NOTICE: contraction of the abs, increasing interior abdominal pressure, can also push out intestines by way of hernia.
    I just had Desarda mesh-free hernia repair, bilateral inguinal – one direct and one indirect – with ab floor rebuild. No foreign body will remain inside me after the sutures dissolve. I'll wait a long time before resuming weight lifting.

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