Description

This video covers the muscles of the thorax, including their origins, insertions, and classifications.

Superficial Muscles

• Thoracohumeral Muscles
• Subclavius
• Serratus Anterior
• Pectoralis Minor
• Pectoralis Major

Deep Muscles

• Proper Muscles of the Thorax
• External Intercostal Muscles
• Internal Intercostal Muscles
• Subcostal Muscles
• Transverse Thoracis
• Levatores Costarum

Superficial Muscles

Subclavius (Musculus Subclavius)

• Origin: First Rib
• Insertion: Lower surface of Clavicle

Serratus Anterior (Musculus Serratus Anterior)

• Origin: External Surface of Ribs 1-9
• Insertion: Medial Border of Scapula

Pectoralis Minor (Musculus Pectoralis Minor)

• Origin: External Surface of Ribs 3-5
• Insertion: Coracoid Process of Scapula (Processus coracoideus scapulae)

Pectoralis Major (Musculus Pectoralis Major)

• Clavicular Part: Pars Clavicularis
• Sternocostal Part: Pars Sternocostalis
• Abdominal Part: Pars Abdominalis
• Insertion: Crest of the Greater Tubercle (Crista tuberculi majoris humeri)

Deep Muscles

Subcostal Muscles (Musculi Subcostales)

• Origin: Lower Rib
• Insertion: Upper Rib

Transverse Thoracis (Musculus Transversus Thoracis)

• Origin:
  • Internal Surface of Sternum
  • Xiphoid Process
  • Cartilage of 4th-7th Rib
• Insertion: Cartilage of 2nd-6th Rib

Internal Intercostal Muscles (Musculi Intercostales Interni)

• Origin: Lower Rib
• Insertion: Upper Rib

External Intercostal Muscles (Musculi Intercostales Externi)

• Origin: Upper Rib
• Insertion: Lower Rib

Levatores Costarum (Musculi Levatores Costarum)

Levatores Costarum Breves

• Origin: Transverse Process C7-T11
• Insertion: One Rib Below

Levatores Costarum Longi

• Origin: Transverse Process T8-T11
• Insertion: Two Ribs Below

Transcript

Introduction
0:03
Hey what’s up. Meditay here and in this video,
0:06
we’re gonna talk about the superficial and the deep muscles of the thorax. Alright, depending
Division of the Thoracic Muscles
0:11
on the source you’re studying from, muscles of the thorax may be divided into 3 groups.
0:15
The first group are the superficial muscles of the thorax, or also called the thoracohumeral muscles
0:21
because they act on the upper limb movement as well. These are the Subclavius, Serratus Anterior,
0:26
Pectoralis Minor and Pectoralis Major. Then we have the Deep muscles of the Thorax,
0:32
which are also called the Proper muscles of the thorax because they both originate
0:36
and insert in the thorax. These are the External Intercostal muscle. Internal Intercostal muscles.
0:42
Subcostal muscles, transverse thoracis and then the levatores Costarum.
0:47
The 3rd group is the Diaphragm. It’s also considered as a muscle of the Thorax. We’re
0:52
not gonna talk about the diaphragm in this video, there’s gonna be a separate video on that one.
0:57
So in this video, we’re first going to talk about the 4 superficial muscles, and then do
1:02
the 5 deep muscles in the thorax. Awesome. So, the subclavius muscle is located here.
Subclavius Muscle
1:08
It’s sub-clavius so it’s under the clavicle. It originates at the first rib as you see here,
1:15
and it inserts at the lower surface of the clavicle. So, when this muscle contracts, it
1:20
stabilized the clavicle by pulling it downwards. Next, we have the Serratus Anterior muscle. These
Serratus Anterior
1:26
are large muscle fiber groups located on the lateral aspect of the 1-9th rib.
1:31
So it originates from the external surface of the ribs 1-9; and it inserts
1:37
at the medial border of the scapula, back here. Just to visualize it better, here you see the
1:42
superior view of it. You see it goes back and attaches to the medial margin of the scapula.
1:48
And when they contract, they pull the medial margin of the scapula forward,
1:53
which help flex the arm. So that’s the serratus anterior. Next is the Pectoralis Minor.
Pectoralis Minor
2:00
The pec minor is located here. It originates from the external surface of the 3rd to 5th ribs
2:06
and insert at the coracoid process of the Scapula. And when they contract, they pull the shoulder
2:13
down and medially. Stiffness in this muscle can harm your pose by bulging your shoulders forward,
2:19
so make sure you stretch this muscle as well whenever you can.
2:22
Alright. Next is the Pec Major, which is here. Fibers of this muscle are divided into three
Pectoralis Major
2:28
parts according to where they originate from. We have the Clavicular part which originates from the
2:34
clavicle, Sternocostal Part originating from the sternum and the costal cartilage and the Abdominal
2:39
part, which originates from the abdominal muscles. And they all unite and insert at a common place,
2:46
which is the crest of the greater tubercle, as you see here. This is the crest of the
2:50
greater tubercle on the humerus. So that was it for the superficial muscles of the Thorax.
Subcostal Muscles
2:56
Next, we have the deep muscles of the thorax. And the first one is the Subcostal Muscles
3:02
These are muscles located on the inside of the thorax on the back here. So let’s focus
3:07
on this area, and zoom in to see them better. All the muscle fibers of the subcostal muscles
3:14
originate from the lower rib, and they insert on the upper rib. And when they contract, they pull
3:20
the thorax downwards to aid with expiration. So they’re a part of the expiration muscles.
Transverse Thoracis
3:26
Then we have the Transverse Thoracis muscle, located here.
3:29
It originates from the Internal surface of the Sternum, the xiphoid process and the cartilage
3:35
of the 4th to 7th ribs. And they insert at the cartilage of the 2nd to 6th rib. They also pull
3:41
the chest downwards to aid with expiration. Then there’s the internal intercostal muscles,
Internal Intercostal Muscles
3:47
which is here between the ribs. These muscles originate from the lower rib, and they insert
3:52
into the upper rib. So when they contract, they’ll also pull the chest down to aid expiration.
External Intercostal Muscles
3:59
Superficially to the external intercostal muscles are the External intercostal muscles. They
4:05
originate from the Upper rib, and they insert at the lower rib. So these muscles are going
4:10
to Elevate the thorax, to help with inspiration, expanding the thoracic cavity to bring the air in.
4:17
After that we have the levatores costarum muscles.
Levatores Costarum Muscles
4:20
These are tiny muscles on the backside here and are divided into two groups.
4:25
First we have the Levatores costarum breves, which are short levatores costarum.
4:30
They originate from the Transverse process of C7 to T11, and insert one rib below.
4:37
So they’re short because thy don’t skip any ribs. The other one is the Levatores costarum
4:43
longi. These ones originate from the T8-T11, and insert two ribs below. They’re longer, because
4:51
they skip one rib completely and then insert two ribs below. And when they contract, they also
4:58
pull the thorax up to aid inspiration. So that the muscles of the thorax and I hope that was helpful.