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Veterinary Anatomy: Forelimb Muscles · Acedra
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Veterinary Anatomy: Forelimb Muscles
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0:12
Hello everyone and welcome back to another anatomy video. This is Dr. Al Aiyan from the Veterinary Anatomy channel. In this video we will go through the muscles which we can dissect or see after removing the forelimb completely. Most of these muscles are related to the uh inspiratory muscles. So let's get started guys. As you can see here, we remove the left forelimb completely from the body. The... I mean cut all the muscles connecting the forelimb to the trunk here and to
0:39
the neck. Uh before we go and talk about the muscles we can find there, let me just like quickly go through some of the muscles which we cut to be able to remove the forelimb completely. And I will start with the pectoral muscles here. The pectoral muscles if you remember we say that we have two pectoral muscles. We have the superficial pectoral muscle, these two here, and we have the deep pectoral muscle. The superficial pectoral muscle which
1:10
has two parts here. We can see both of them. We have here the descending pectoral muscle which will start from the cranial part of the sternum... and inserts to the uh cranial part of the sternum there and inserts to the humerus. Let me just put the humerus in place. So it will... it will insert to this area of the humerus. So um this is the descending pectoral muscle. The other part of the superficial pectoral muscle is the transverse pectoral muscle
1:45
or transverse part of the superficial pectoral muscle. This one originates also from the sternum, cranial part of the sternum, and inserts also to the um cranial surface of the humerus in the proximal region here somehow. So this is the transverse pectoral muscle. So um here we have the deep pectoral muscle which will originate... it originates from the sternum, the whole sternum actually here, and moves all the way and inserts to the lesser tubercle of
2:19
the humerus. So this tubercle of the humerus... and we found that part of this muscle can also go to the greater tubercle of the humerus. So this is the insertion of this muscle. What are the name? The deep pectoral muscle. So we cut both of them of course to be able to remove the forelimb. Now we can put them a little bit on the side. The first muscle I would like to discuss in this video and we cut also like to be able to remove the forelimb is the serratus ventralis
2:51
muscle. Serratus ventralis muscle has also two parts. One part comes from the neck area, exactly originates from the transverse processes of the cervical vertebrae. These processes here. So this is the cervical vertebrae. Let me just put it in view. So it originates from the transverse process of the cervical vertebrae and inserts to the vent... to the serrated face of the scapula. Yeah. Where the serrated face of the scapula is on the
3:27
medial surface of the scapula. So where exactly? This here, this rough area here of the scapula, the serrated face, the insertion of the serratus ventralis muscle. In this case, this part here from the transverse process of the cervical vertebrae to the serrated face, to this area here: the cervical part of the serratus ventralis muscle. While the other part of the serratus ventralis muscle, this part here, originates from the
4:00
ribs. As you can see, it has several small uh finger-like... no uh structures. One comes from each rib. If you count them, 1, 2, 3, 4, 5, 6, 7. In this case, the serratus ventralis muscle thoracic part in the dog originates from rib number one up to the rib number seven. All to come together as you can see and inserts to the... to the caudal, if we put it in again here, to the caudal part or caudal surface of the serrated face. So yeah to this area, serrated
4:40
face or serrated surface of the scapula, this is the insertion of the thoracic part of the serratus ventralis muscle. So that's why both parts we had to cut to be able to remove the forelimb. Yeah. Look at the shape of this muscle. It has like a finger shape or teeth shape. That's why we name it as serrated muscle. Serrated muscle. So the serratus ventralis muscle, cervical part and thoracic part. According to the origin and insertion you will understand the function of
5:17
it. So regarding the thoracic part for example, in addition of course to fix the forelimb to the trunk and to the neck, the thoracic part of the serratus ventralis muscle uh the contraction of this muscle will move the ribs, at least the first seven ribs here, away from the body increasing the volume of the thoracic cavity and that's why we can consider this part as a helper muscle as inspiratory muscle. So it helps in inspiration. Okay. So this was the serratus ventralis muscle.
5:55
So as we we we say serratus ventralis muscle that means we have also serratus dorsalis muscle. I put it just like this so that you can keep seeing this muscle, cervical, thoracic part. Here we can see the serratus dorsalis muscle. Why is serrated? Again it has the same shape. Can you see this part of the muscle? So this is the serratus dorsalis muscle. If we move a little bit caudally we can find another kind of muscle which looks similar and it... I mean we will name
6:30
it also serratus dorsalis muscle and that's why the serratus dorsalis muscle could be divided into two parts. That part located cranially is the cranial serratus dorsalis muscle. Wait, that one... that one located caudally is the caudal serratus dorsalis muscle. The cranial serratus dorsalis muscle. I will put just the forceps just under it. So you can see the tendon of it. So it originates also from the ribs as you can see here and inserts to the
7:08
median raphe in this area and to the uh spinous processes, specifically of course the supraspinous ligament, supraspinous ligament there. If you look at the origin and insertion of this muscle, you will understand that contraction of this muscle will also move the ribs away from the midline of the body increasing the volume of the thoracic cavity and that's why we have to consider this muscle as an inspiratory muscle. So the cranial serratus dorsalis muscle is an inspiratory muscle.
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Well, if we move to the caudal... caudal serratus dorsalis muscle. So this here... it's... it has several small parts of course like fingers like this. So it originates from the caudal surface of the last ribs and inserts to the fascia in that area and that's why contraction of this muscle will move the ribs toward the body, toward the body, decreasing the volume of the thoracic cavity and that's why this muscle
8:21
is considered as expiratory muscle. So the caudal serratus dorsalis muscle is expiratory muscle. Okay. Cranial serratus dorsalis muscle, caudal serratus dorsalis muscle. Now um in this view we can see another very cute small muscle here. This muscle here. Can you see that? So it's it's a muscle which will start somehow from the second and the third rib and starts somehow to the first rib. This one here, we just put the forceps in under it. Can you see
9:08
it? This muscle here called the straight muscle of the thorax or rectus thoracis muscle. Yeah. Rectus thoracis. This muscle according to the origin and insertion you will understand that uh contraction of this muscle will move these two ribs, three ribs here, away from the midline, that means increasing the volume of the thoracic cavity, that means helping with the inspiration. That's why we will consider this one as inspiratory muscle. What are the name of it? Is the straight
9:44
muscle of the thorax or the rectus thoracis. If you follow the tendon actually of this muscle, just for your information, can you see the tendon here? You will see it continued with the tendon of this muscle here which is the straight muscle of the abdomen or rectus abdominis just for your information. So you can easily find the two muscles. Okay, this one the rectus thoracis. Another muscle we can see in this view here, this very interesting muscle. So here, I don't know if
10:20
I can highlight it here. I just put the forceps under this part and that part. Can you see this part? This one. So this one and that one and that one. Here we are talking about the scalenus muscle. Scalenus muscle. Very famous muscle which is normally have three parts. Scalenus muscle has three parts: the dorsal, middle, and ventral scalenus muscle. So I'm always like telling my students to put their fingers like this to remember that the scalenus muscle has three parts:
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dorsal, middle, and ventral. And as a comparative anatomy you will find that in the dog we have only the dorsal and the middle part. There is no ventral part of the scalenus muscle. In the horse, it's exactly the opposite. We don't have in the horse the dorsal part. We have only the middle and the ventral. In ruminants, all three parts are present of the scalenus muscle. Here, let's go. We have a dog here. That's why we can find only one... two parts. Only these
11:36
two parts. So this is here the dorsal part of the scalenus muscle. If you look at it exactly, you will find it originating from the lateral surface of the ribs. So these ribs here all the way and inserts to the... to the transverse processes of the last few cervical vertebrae. It inserts to this area here which I can palpate this view here. Yeah. While the middle scalenus muscle it starts
12:15
from the first rib. So this here is the first rib and inserts also like the other to the transverse process of the last three uh cervical vertebrae in the dog. So if you look at this muscle, you will find that contraction of this muscle will also move the ribs. Yeah. Contraction of this muscle, both of them, they will move the ribs away like this, away from the midline of the body, increasing the volume of the thoracic cavity, helping with the inspiration. That's why
12:53
the scalenus muscle is one of the inspiratory muscles. Scalenus muscle. Very interesting muscle. What else in this view? We can also find yeah some other muscles. So we are talking about respiratory muscles. So let me also tell you something about the intercostal muscles here. As you can see between the ribs, between the ribs, there's another muscle located between the ribs called the intercostal muscles. I said intercostal muscles,
13:37
not only one. Why? Because if you dissect this muscle carefully, and very carefully, you will find that between the ribs at this level, we have two intercostal muscles located on each other.
13:53
Both are very thin. The outside located one, the one you can see in this view, is the external intercostal muscle. External intercostal muscle. And if you look at the... the muscle fiber direction, you will find it going like cranioventrally... caudoventrally. Caudoventrally. If you dissect it, and we will do this very soon... uh you will find another muscle just below this muscle. I will try now to do this. So you have to be really very careful
14:27
guys because the external intercostal muscle is really very thin muscle, very thin muscle. So I will cut only the external intercostal muscle here and I will try to show you the underlying muscle. Now as we said before we dissected the intercostal muscles in the way that we separated the external intercostal muscles as you can see here, this view, from the internal located one. If we move the external intercostal muscle here to the side, we can see the next layer
15:08
is the internal intercostal muscle. If you look at the muscle fibers guys of these two muscles, you will find first that the muscle fibers of the external intercostal muscle is going like caudoventrally. Start from this... to... from this rib to this rib ventrally, ventrally. While if you look at the internal intercostal muscle, yeah, you will find that the fibers, muscle fibers are directed cranioventrally, cranioventrally. Yeah. Um another example we did here. So here we can see
15:46
the external intercostal muscle with the muscle fibers caudoventrally directed. If we dissect it, move it to the side, you will find the deep-located one which is the internal... I will remove my finger. So the internal intercostal muscle with the muscle fibers directed cranioventrally. Yeah, as we said before the external intercostal muscle is inspiratory muscle while the internal intercostal muscle is expiratory muscle. Let's just put them in place.
16:23
So we talked about these muscles. What else? I will try now to remove the... serratus ventralis muscle completely, the scalenus muscle, maybe the rectus thoracis so that we can have a better view of the deeper muscles. Before we end now, let me just remind you about some of the structures which we can find in this area here. We have this very interesting lymph node which we can... we we found
16:54
just under the forelimb. Just under the forelimb was like this on the medial side of the forelimb, exactly medial to the shoulder joint somehow between the muscles there. It's the axillary lymph node. This is the axillary lymph node. Next to it we can of course and we had to cut a lot of nerves which belong to the brachial plexus. As you know the brachial plexus sends a lot of nerves to the forelimb. So we had to cut all of these nerves. So we can see them in the depth there.
17:29
I can see big artery. Can you see the big artery here coming as a continuation of the subclavian... artery and going to the forelimb. So this artery we will name it as axillary artery. Next to it we have one vein, the big vein to the forelimb or from the forelimb called the axillary vein. Okay guys that's everything. Of course uh stay with us in the next video we will be dissecting uh a very important muscles including the abdominal muscles which we can find here
18:06
and there. So um before we end this video as we agreed I will... I have some questions for you. Um if you watch the previous video in this area we dissected the muscles of the neck and I would like to ask you to name this muscle. So this is the question number one hint for you. This muscle starts from the wing of the atlas. Let me just show you exactly from where it starts, from the wing of the atlas and inserts to the acromion. Inserts to the acromion of the scapula. So I need
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you to write the name of this muscle which we had to cut to be able to remove the... the forelimb. It inserts to the acromion. So we have to cut this muscle. This is the question number one. Question number two will be this muscle here. There's another muscle which we had also to cut to be able to remove the forelimb. Hint for you: this muscle starts from the clavicular insertion. You have to find out what is clavicular insertion and inserts to the mastoid process
19:32
of the skull. So I need you to write the name of this muscle. This is question number two. And the last question in this case... the last question in this case is this muscle here. So I need you to write the name of this muscle which we explained of course in details in the previous videos. And this muscle has two parts. Yeah. So I will not tell you actually even the... the origin and insertion of of this muscle. It will
20:01
be very easy to know of course if I tell you. So this muscle here starts from there. Okay. And inserts to the occipital bone, the part which we cut here, and inserts also to the mastoid process. I need you to write the name of this muscle. This is question number three. So that's everything for this video. Yeah as I said before the next video will be very interesting. So subscribe, share these videos with your friends if they are interested. If
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you have any question, write them in the comments below and I will try my best to answer your questions. So thank you very much. See you very soon. Bye-bye for now.
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