Prepladder anatomy upper limb video -7 axilla
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00:00Axilla is the armpit which has a pyramid shape with the four walls, a base and one apex. The four
00:13walls are anterior wall, posterior wall, lateral wall and medial wall of axilla. Base is at the
00:19floor of axilla and when we talk about the apex it is pointing towards the neck region. In fact
00:25there are some neurovascular bundle in the neck region, cervical region and they'll be entering
00:30the axilla through the apex of axilla. It is also called as cervico-axillary canal. Cervico means
00:36the neck and the content now moving into axilla say for example the subclavian vessels subclavian
00:43artery and vein as they enter the axilla they continue as axillary artery and axillary vein
00:49plus we understand the brachial plexus partly is in the neck region and passing behind the
00:54clavicle bone it enters the axilla. We can also discuss the three chords of brachial plexus in the
00:59axilla then. Now at the moment we want to know which muscles are contributing to the anterior
01:04wall of axilla. If you remember we have discussed a large muscle pectoral major and undercover of that
01:10pectoral minor. So two muscles in the anterior wall of axilla. What are the three muscles in the
01:16posterior wall of axilla? We have discussed a muscle coming from lower back the latissimus dorsi
01:21and it goes with the posterior major that is the teres major and along with the two is a muscle
01:26under scapula the subscapularis. So three muscles contributing to posterior wall of axilla. Now this
01:32anterior wall and posterior wall of axilla converge on the lateral wall of axilla which is quite
01:37narrow and contributed by the bicipital groove on the bone humerus along with the long head of
01:43biceps running there and when it comes to the medial wall of axilla it is the serratus anterior
01:48muscle along with the upper four ribs giving origin to the muscle. We understand that serratus
01:53anterior takes its origin from the anterolateral surface of upper eight ribs but in the axilla
01:59medial wall you have to include only the upper four ribs. Let us look at one diagram also to
02:05have a better orientation of the axilla region. In this diagram we can see that this is the right
02:12sided armpit we are going to focus upon and this axilla region is pyramid shape having four walls
02:19one floor one apex as is evident here this is going to be the floor of the axilla and towards
02:24the apex which is pointing to the neck region we have got three bones like anteriorly we can see
02:31the clavicle bone contributing to the inlet cervico-axillary inlet. So anteriorly we have the
02:37clavicle bone medially we have got the first rib which you can demarcate now this is the first rib
02:44part of which will be contributing to the apex of the axilla boundary and then there is one bone
02:50which is on the posterior boundary the scapula bone which you can demarcate here posteriorly
02:56now what about the structures which are passing through this inlet into the axilla as we understand
03:02the brachial plexus roots and trunks are in the neck region divisions pass behind the bone clavicle
03:07and then cords and branches are in the axilla so brachial plexus from the neck region will enter
03:12the axilla through this inlet bounded by the three bones passing behind the bone clavicle and in the
03:17axilla we have to discuss the three cords of brachial plexus there is one artery and vein in
03:22the neck region under the clavicle hence the name subclavian and as they cross the outer border of
03:28first rib to enter the axilla they change their name now to be called as axillary artery axillary
03:33vein as they are now content of the axilla and in relation to that axillary artery we have to
03:39discuss the three cords of brachial plexus the lateral cord the middle cord and the posterior
03:43cord of the brachial plexus in the axilla now talking about the four walls in the anterior
03:49wall you have got two muscles and which is evident here contributed chiefly by the large muscle
03:56pectoral muscle deep with that pectoral minor muscle also contributes to the anterior wall of
04:02the axilla and what about the three muscles contributing to posterior wall of axilla the
04:07armpit posteriorly we have got three muscles contributing like from the lower back comes the
04:14lady the latissimus dorsi and along with latissimus dorsi we have got two more muscles one muscle
04:20coming from the dorsum of the scapula to the humerus teres major and another one under scapula
04:26the subscapularis towards the humerus so total three muscles contributing to posterior wall of
04:32axilla and the two walls are converging on the lateral wall of the axilla which is the humerus
04:38bone in the region of the bicipital groove lodging the tendon of long head of biceps brachii and what
04:45about the fourth wall the medial wall of the axilla it is basically the upper four ribs along
04:51with the origin of the serratus anterior muscle that will form the medial wall of axilla can be
04:57drawn here as well the medial wall of the axilla but the upper four digitations of serratus anterior
05:03coming from the upper four ribs now for having a better orientation let us take a transverse section
05:10in the right axilla region which also appears in the exam and we need to discuss the boundaries
05:15once again and along with the contents but before you do that you must have good orientation let
05:20us look at the next diagram then as we continue with the details of the right axilla we want to
05:26take a transverse section here and look from the superior view it is like you are looking at the
05:31right shoulder joint from the superior view that transverse section is being shown here which we
05:37have to discuss like showing the humerus bone laterally the ribs medially the scapula posteriorly
05:43pectoral muscles anteriorly it is basically looking at the right-sided shoulder joint or right-sided
05:49axilla so let us magnify this region so that we can have proper orientation before we start
05:55discussing the diagram here we are going to zoom this area and as we have discussed earlier we can
06:00enumerate the bones which were at the apex of the axilla anteriorly we have the clavicle bone and
06:05medially we'll have the ribs especially the first rib forming the boundary of the axillary inlet
06:12from the neck region and then we have got one bone on the posterior side that is the scapula bone
06:18let us show it here and when we are talking about the bone on the lateral side it is the humerus bone
06:24which has to articulate with the scapula to form the shoulder joint and is at the lateral wall of
06:30the axilla we have learned there is a lateral lipobicipital groove, medial lipobicipital groove
06:36and floor of the bicipital groove that is where we have taken this section and in fact you can now
06:42show these details in the transverse section as well so you can correlate it better here is the
06:48humerus bone showing the lateral lipobicipital groove and the medial lipobicipital groove
06:54between the two we have floor of the bicipital groove now this is the humerus bone on the lateral
07:00relation of the axilla what about the medial bone? Medially we have got the four ribs and one of them
07:07is evident here so upper four ribs are forming the medial wall of the axilla what about the posterior
07:13bone? Posteriorly we have seen is going to be the scapula bone and we can show it in the transverse
07:20section as well and we have to be aware about its lateral border and medial border towards the rib
07:27we have the medial border of scapula and towards the humerus will have lateral border of scapula
07:32and bounded by these bones and muscles we have got the axilla the content will be axillary artery
07:38axillary vein and the three quads of brachial plexus giving some branches but before we talk
07:44about the contents what are the two muscles in the anterior wall of axilla the pectorals pectoral
07:50major and pectoral binder what is the origin of pectoral major? it has extensive origin but here
07:56you can see from the costal cartilages of the upper ribs then what will be the insertion? pectoral
08:03major will be inserting into the lateral lip of the bicipital groove on the bone humerus now once
08:09we have shown the pectoral major muscle under cover of that is the pectoral minor muscle both
08:15contributing to the anterior wall of axilla what about the three muscles in the posterior wall of
08:21axilla? posteriorly we have seen there is a lady from lower back coming and then inserting at the
08:27floor of the bicipital groove and along with that we have got the posterior major the teres major
08:33attaching to the medial lip of bicipital groove as is evident here and we remember this as a mnemonic
08:40the lady between two majors the anterior major is pectoral major on the lateral lip of bicipital
08:45groove and the posterior major is teres major on the medial lip of bicipital groove at the floor
08:50is the lady now these two muscles along with subscapularis will be contributing to posterior
08:55wall of axilla subscapularis muscle as the name is suggesting it is under the scapula bone as
09:01evident here so this is the subscapularis muscle contributing to posterior wall of axilla the
09:06posterior wall and anterior wall they are converging on the lateral wall on the lateral wall we have
09:13long head of biceps brachii running in the bicipital groove so you can show it here in the diagram
09:19as well and once we have talked about the lateral wall what about the medial wall medially we have
09:26got the upper foreribs giving origin to serratus anterior from the anterolateral surface you can
09:32show one digitation of serratus anterior attaching to the medial border of the scapula but on the
09:38anterior aspect so it is contributing to the medial wall of axilla and then we can look at
09:44the contents the contents there will be one artery the axillary artery and related to that
09:50as we have mentioned will be the three cords of brachial plexus which will be drawing a diagram
09:56ourselves but you can just mention here posterior cord is posterior to the artery lateral cord is
10:02lateral and then we have got medial cord of brachial plexus medial to the artery we also need
10:08to discuss a vein the axillary vein but that will be doing in our own diagram our diagram is a
10:14schematic diagram showing the upper foreribs on the medial aspect scapula on the posterior aspect
10:19hemorrhage bone with the bicipital groove on the lateral aspect and anteriorly the pectoral muscles
10:25let us do that now we start by mentioning the upper foreribs contributing to the medial wall
10:31of axilla and then we can also look at the posterior wall which is then contributed by the
10:37scapula bone we must take a note of medial border and lateral border of scapula so here is going to
10:44the medial border and this side lateral border the bone is scapula bone contributing to posterior
10:50wall of the axilla just mention and then we come to the lateral wall of axilla as well where we
10:56show the hemorrhage bone along with the medial lip and the lateral lip of the bicipital groove
11:02so here is the lateral lip and there lies the medial lip of bicipital groove and then we can
11:09discuss the muscles contributing to the four walls the muscle on the anterior wall will be pectoral
11:15major and minor we know pectoral major has extensive origin but it takes origin from the
11:21upper costal cartilages as well which can be demonstrated here and then the insertion is into
11:27the lateral lip of the bicipital groove and this muscle contributing to the anterior wall of axilla
11:34along with the pectoral minor which lies deep to it so these two muscles contribute to the anterior
11:42wall of the axilla and hence we have described the four walls of the pyramid shape axilla the
11:48anterior wall posterior wall the medial wall and the lateral wall in the lateral wall will have the
11:54long head of biceps brachii in the bicipital groove which can be shown here and then we can
12:00move on to the medial wall of axilla as we understand medial wall of axilla you have
12:05serratus anterior muscle the origin is from the anterolateral aspect of the upper ribs and the
12:12insertion on the medial border of scapula anterior surface so as we show it these are the fibers
12:20of serratus anterior muscle inserting on the medial border of the scapula and then we can
12:26look at the lateral border as well because we understand from the dorsal aspect of the lateral
12:32border of the scapula one muscle is going to take origin contributing to the posterior wall of axilla
12:39so which muscle are we talking about the posterior major at the iris major as we look at the fibers
12:46of teres major it will be inserting on the medial lip of the bicipital groove and we can mention
12:52this major along with the lady that is latissimus dorsi contributes to posterior wall of axilla
12:58now this lady inserts into the floor of bicipital groove whereas its origin is from the lower back
13:05and along with a muscle under scapula it will be contributing to the posterior wall of axilla this
13:11muscle under scapula is the subscapularis muscle and now we have got the three muscles contributing
13:17to posterior wall of axilla latissimus dorsi, teres major, subscapularis once we have described
13:23the walls of the axilla we have to look into the contents which will be the brachial plexus
13:28and the subclan artery continuing as axillary artery actually there is a covering of cervical
13:34fascia over these structures which continue down into the axilla and becomes the axillary sheet
13:41inside the axillary sheet we will have the axillary artery and the brachial plexus let us
13:47zoom this area a little bit now so as to describe the details this axillary sheet which is continuation
13:53of the cervical fascia contains the artery the axillary artery and in relation to the artery
13:59we have got three chords of brachial plexus if posterior it is the posterior chord of brachial
14:04plexus laterally the lateral chord of brachial plexus and medially which goes slightly anterior
14:11as well is the medial chord of brachial plexus these chords are named according to their relation
14:17with the axillary artery in the axilla now what is the continuation of posterior chord of brachial
14:22plexus posterior chord of brachial plexus continues as the radial nerve and the lateral chord the
14:29muscular cutaneous nerve and what about the medial chord of brachial plexus continues as the ulnar
14:35nerve here we have shown the axillary artery where is the axillary vein and there you be careful
14:42axillary vein is not a content of the axillary sheet it lies outside more medially as you can
14:48show this is the location of the axillary vein outside the axillary sheet and let us zoom out a
14:54little bit so as to understand their relation the posterior chord of brachial plexus lateral chord
15:00medial chord which is actually anteromedial in relation to the axillary artery this is all inside
15:05the axillary sheet while outside is the axillary vein the contents of the axilla here the examiner
15:10sometimes gives hand-drawn diagrams with the markers a b c d