Description

Small correction: The rectus abdominis originates from the pubic crest and symphysis and inserts into the xiphoid process and costal cartilages of ribs 5–7. I mistakenly swapped the origin and insertion in the video. Apologies for the error!

Muscles of the Abdomen

• Lateral Group
  • External Oblique
  • Internal Oblique
  • Transverse Abdominal
• Anterior Group
  • Rectus Abdominis
  • Pyramidalis
• Posterior Group
  • Quadratus Lumborum

Posterior Group

Quadratus Lumborum (Musculus Quadratus Lumborum)

• Origin:
  • Iliac Crest
  • Iliolumbar Ligament
• Insertion:
  • 12th Rib
  • Costal Process of L1-L4
• Function:
  • Extension of Trunk (Bilateral Contraction)
  • Lateroflexion of Trunk (Unilateral Contraction)

Anterior Group

Pyramidalis (Musculus Pyramidalis)

• Origin: Superior Pubic Ramus
• Insertion: Linea Alba
• Function: Tenses Linea Alba and Strengthens the Rectus Sheath

Rectus Abdominis (Musculus Rectus Abdominis)

• Origin:
  • Pubic Crest
  • Pubic Symphysis
• Insertion:
  • Xiphoid Process
  • Costal Cartilage of 5th – 7th Rib
• Function:
  • Ventral Flexion of Trunk
  • Expiration Muscle

Lateral Group

Transverse Abdominal (Musculus Transversus Abdominis)

• Origin:
  • Inguinal Ligament
  • Iliac Crest
  • Thoracolumbar Fascia
  • 7th – 12th Ribs
• Insertion: Linea Alba
• Function:
  • Rotation of the Trunk
  • Expiration Muscle

Internal Oblique (Musculus Obliquus Internus Abdominis)

• Origin:
  • Inguinal Ligament
  • Iliac Crest
  • Thoracolumbar Fascia
• Insertion:
  • Linea Alba
  • 10th – 12th Ribs
• Function:
  • Ventral Flexion of Trunk (Bilateral Contraction)
  • Tilts the Trunk to the Side (Unilateral Contraction)
  • Expiration Muscle

Cremaster (Musculus Cremaster)

• Formed by: Internal Oblique and Transverse Abdominal Muscles

External Oblique (Musculus Obliquus Externus Abdominis)

• Origin: 5th – 12th Ribs
• Insertion:
  • Linea Alba
  • Iliac Crest
• Function:
  • Ventral Flexion of Trunk (Bilateral Contraction)
  • Tilts the Trunk to the Side (Unilateral Contraction)
  • Expiration Muscle

Transcript

Introduction 0:03 What’s up. Meditay here and in this video, we’ll be going through the 0:07 muscles you’ll find in the abdominal region. So here you see the anterior view of the Abdomen. Division of the Abdominal Muscles 0:12 And here I’ve cut through all the muscles of the abdomen in order to se them all. The most 0:17 external muscle of the abdomen is the External Oblique Muscle. 0:21 Then there’s the Internal Oblique muscle, and then the Transverse Oblique Muscle. These three muscles 0:27 are a part of the Lateral Abdominal Muscles, or lateral groups. So the muscles of the abdomen 0:31 are organized into three groups. And these are the lateral group. Then we have the Rectus Abdominis, 0:37 and a tiny muscle called Pyramidalis. These two are considered the Anterior Group of muscles. 0:44 And then the Posterior group has only one muscle, which is this one, 0:48 called the quadratus lumborum. So, these are the muscles we’re going to focus on in this video. 0:53 All of the muscles of the abdomen corporate in their function. 0:57 They corporate in flexing your abdomen, rotating it from one side to another and so on. All of them 1:03 also corporate with the diaphragm during breathing, and they do that by regulating 1:08 the intra abdominal pressure by either squeeze your abdomen, to push your air out, or releasing 1:13 the pressure off from your abdomen to allow the diaphragm to expand volume of the thoracic cavity 1:19 to push air into the lungs. Awesome. Now let’s start with the posterior group. 1:23 Then we’ll do the anterior group and then end with the lateral group. So the Quadratus Lumborum, Quadratus Lumborum 1:28 again, is situated on the posterior abdominal wall, as you see here. It originates from the 1:34 Iliac crest and the Iliolumbar ligament. And it inserts at the 12th rib, as well as 1:39 the costal processes of L1 to L4. And its function is either extension of the trunk during bilateral 1:46 contraction, or Lateral flexion of the trunk, if only one side contracts. So that was this one. Pyramidalis 1:53 Now the anterior group consists of two muscles. The first one is a tiny muscle located here. 2:00 Down here, this tiny muscle. It originates from the Superior Pubic Ramus, 2:05 and insert at Linea Alba, which are fibers in the midline. And its function is really just 2:10 to tense the linea alba and strengthen the rectus sheath, which are the tendons of the 2:16 lateral group of muscles. So it helps to tense the tendon of the lateral abdominal muscles. Rectus Abdominis 2:22 The other anterior muscle of the abdomen is the rectus abdominis, as you see here. 2:27 This one is going to originate from the xiphoid process and the costal cartilage of the 5th 2:32 to 7th rib. And then it’s going to insert at the body of pubis between the pubic symphysis 2:38 and the pubic tubercle, as you see here. Its function is to ventrally flex the trunk, 2:44 and it also increases the intraabdominal pressure to push the diaphragm up and aid with expiration. 2:50 So that’s these. Then the last group is the lateral group of the abdomen. Transverse Abdominal Muscle 2:56 The first one is the transverse abdominal muscle. The transverse abdominal muscle is going to 3:01 originate from a couple of structures located on the lateral and posterior region og the body. 3:06 So, it’s going to originate from the Inguinal ligament and the iliac crest, 3:10 as you see here. It’s also going to originate from the thoracolumbar fascia, which is a fascia on the 3:16 lumbar region as you see here. And it’s going to originate from the 7th-12th rib. And then 3:22 its tendons is going to insert at linea alba. Its function is to rotate the trunk, and also 3:29 increase the intraabdominal pressure to aid with expiration. Notice that the rectus abdominis run 3:36 through the transverse abdominis muscle. That means that the upper part of the transverse 3:40 abdominis lie behind the rectus muscle, and its lower part is in front of the rectus abdominis. 3:47 So that was this one. Then we have the Internal Oblique muscle, which is here. Internal Oblique 3:52 It Originates from the Inguinal Ligament, and the iliac crest. As well as from the 3:58 thoracolumbar fascia as well. Then it’s going to insert at the 10th to 12th rib 4:03 as you see here, as well as the Linea Alba. And its function is ventral flexion of the trunk, 4:09 if both sides contract. Or tilt the trunk to the side is one side contract. 4:15 It’s also going to adjust the intraabdominal pressure and aid with 4:18 expiration by pushing your diaphragm upwards. Now the Internal Oblique and the transverse Cremaster Muscle 4:24 abdominal muscles are a little special in that, they’re both going to fuse at the very bottom 4:29 of the abdomen, and form a muscle called the cremaster muscle, specifically in male. 4:34 Because this muscle is going to surround the spermatic cord and the scrotum, as you see here. 4:40 And this is actually the main reason why the testes are able to regulate its temperature. 4:45 Whenever its cold outside, the cremaster muscle will contract and pull the testes towards the 4:50 body to maintain its temperature. And when it’s warm outside, well then they’ll relax since they 4:56 don’t need the body temperature anymore. So that’s these ones. The last muscle is External Oblique 5:02 the external oblique muscle. It originates from the 5th to 12th rib, so back here, 5:07 5th to 12th rib, and they insert at linea alba, as well as the iliac crest. 5:13 And its function is bilateral contraction will cause ventral flexion of the trunk, 5:19 and unilateral contraction will tilt the trunk to the side. And this also aids with expiration. 5:23 So that was all the muscles of the abdomen, and I hope that was helpful.