Upper Limb. Bones and Muscles Proximal Region
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00:00:00We are going to focus upon some of the bones and the muscle attachments for the
00:00:11upper limb and especially in the proximal region. So that will include the
00:00:15bones of a pendicular skeleton for the upper limb starting with clavicle bone
00:00:19then we have got the scapula bone and the humerus bone. Then we'll be focusing
00:00:23upon some of the muscles like pectoral major, pectoral minor. Under scapula we
00:00:28have some scapularis muscle, laterally we have the deltoid muscle, there's a
00:00:32biceps muscle which has two heads coming from the scapula bone inserting on the
00:00:36radius bone and there's a triceps muscle which is on the posterior aspect of the
00:00:41arm. It has origin from scapula bone and also from the humerus bone inserting on
00:00:45the ulna bone. We also need to discuss a muscle attaching to humerus bone coming
00:00:49from the lower back that is the latissimus dorsi muscle and one upper
00:00:53back muscle which is the trapezius muscle. Under cover of trapezius we have
00:00:57got some scapular muscles like levator scapula, the rhomboid major minor. In fact
00:01:02you have to understand that though this information can be elaborate but we are
00:01:06not supposed to remember each and everything. We'll just focus upon that
00:01:10information which is important from examination point of view and clinically
00:01:15as well. Presently we are looking at the front view of the left upper limb region
00:01:20focusing upon three bones basically the clavicle bone, scapula bone and the
00:01:25humerus bone in the appendicular skeleton. Actually the examiner sometimes
00:01:29should be putting the markers A, B, C, D in an x-ray or maybe in the surface
00:01:35marking and you need to know where exactly the bony landmarks are present.
00:01:39So let us begin with the clavicle bone, the collarbone. As you see it will have
00:01:43one medial end and is going to have one lateral end. So this is the lateral end
00:01:50and here is the medial end. Medially it is articulating with the sternum bone to
00:01:54form sternoclavicular joint which is a saddle synovial joint helping us in
00:01:59shoulder abduction which is basically elevation of the humerus away from the
00:02:04body and for shoulder abduction we are also being helped by laterally present
00:02:08acromioclavicular joint where the lateral end of clavicle is articulating
00:02:13with the acromion process forming a plain synovial joint. This acromion
00:02:17process belongs to scapula bone and comes from the posterior side. Before you
00:02:22show that let us mark the clavicle bone in the x-ray here. So that is the lateral
00:02:27end of the clavicle and you can proceed to the medial end as well. This is the
00:02:31medial end of the clavicle and then you can mark the shaft of the clavicle. So
00:02:36this is the shaft of the clavicle and as we were discussing laterally the
00:02:40clavicle has to articulate with the acromion process of the scapula to make
00:02:45the acromioclavicular joint and this acromial process of scapula is coming
00:02:51from the posterior aspect because basically scapula bone is present on the
00:02:55posterior side on the posterior thoracic wall. This is just one anterior
00:02:59projection the acromion process. You can demarcate the acromion process in this
00:03:04diagram as well as we mentioned it is an anterior projection coming from the
00:03:09scapula bone, the acromion process and articulating with lateral end of the
00:03:13clavicle to form acromioclavicular joint. Now there is one more process of the
00:03:18scapula which we need to know projecting anterior under the clavicle in
00:03:22infraclavicular fossa and we call it as coracoid process of scapula. So here is
00:03:27the anterior projection of the scapula the coracoid process in the
00:03:31infraclavicular fossa. Let us show that in the x-ray as well. So this is the
00:03:36coracoid process an anterior projection from the scapula in the
00:03:40infraclavicular fossa under the clavicle. Now in the scapula we need to discuss
00:03:45glenoid cavity which is on the lateral border of the scapula. Scapula does not
00:03:49give you clear demarcation from the front view because as I mentioned it is
00:03:53on the posterior thoracic wall but some demarcation is available. So this is the
00:03:58lateral border of the scapula on which we have got the glenoid cavity of
00:04:02scapula that is where the humerus bone will be articulating to form the
00:04:05shoulder joint. This is the front view of the left shoulder joint. Let us show the
00:04:10same structure that is the glenoid cavity or glenoid fossa in this diagram
00:04:15as well. It is the lateral border of the scapula which will have this glenoid
00:04:20cavity or glenoid fossa where the head of the humerus is articulating ball and
00:04:25socket sonovial joint. The front view of left shoulder joint and here we are
00:04:30looking at the head of the humerus articulating with the glenoid cavity of
00:04:34the scapula which can be represented here as well the head of the humerus
00:04:39forming the shoulder joint. On the upper end of the humerus we will see there are
00:04:44two tubercles also the lesser tubercle and the greater tubercle. The lesser
00:04:48tubercle is more prominent as compared with the greater tubercle. If you're
00:04:53looking from the front view though the greater tubercle is comparatively bigger
00:04:57but is seen more clearly from the superior and posterior aspect. So greater
00:05:03tubercle is posterior superior better seen from posterior aspect whereas lesser
00:05:07tubercle which is smaller as the name is telling lesser is more evident from
00:05:11the front view and between the two we have intertubercular sulcus or
00:05:15intertubercular groove which can also be mentioned in this particular diagram. So
00:05:20here we got the lesser tubercle and the greater tubercle on the upper end of the
00:05:24bone humerus. Between the two we have got the intertubercular sulcus also called
00:05:29as intertubercular groove or bicipital groove that is where we see the long
00:05:34head of biceps and then is passing through this region and now we will move
00:05:39on to the next diagram to discuss more details of the bone clavicle in terms of
00:05:43its ossification that is the embryology and one clinical aspect the fracture of
00:05:48clavicle. So as we keep focusing upon the clavicle bone we have to understand that
00:05:54it is a long bone but actually is present in horizontal disposition. See
00:06:01normally the long bones like the humerus bone, radius bone, thalna bone or in the
00:06:06lower limb the femur bone, tibia fibula bone these are all long bones in
00:06:10anatomical position their disposition is longitudinal vertical but clavicle bone
00:06:16despite being a long bone is not put in vertical disposition it is in horizontal
00:06:21disposition that is a peculiar feature of clavicle bone plus it's the only long
00:06:27bone which will have two primary centers of ossification normally a long
00:06:32bone will have only one primary center but clavicle has two primary center of
00:06:36ossification which will appearing in the intrauterine life and forming the shaft
00:06:41of the clavicle. Now if we talk about the secondary centers of ossification they
00:06:47appear after birth and for clavicle there is one secondary center of
00:06:51ossification as per Gray's anatomy though there are some authors who might
00:06:55be mentioning more than one secondary center but it is better you remember
00:06:59clavicle has two primary center of ossification and one secondary center of
00:07:04ossification there are some other peculiar features of clavicle bone this
00:07:08bone is subcutaneous throughout you can palpate the clavicle all along its
00:07:14length and most of the authors will say clavicle bone has no bone marrow cavity
00:07:19Gray's anatomy has some difference of opinion but most of the authors mention
00:07:24it does not have a bone marrow cavity so you follow that then we notice it has
00:07:29one anterior convexity in its medial two-third and anterior concavity in the
00:07:35lateral one-third and wherever is the junction point that becomes a weak point
00:07:40and most of the fractures occur at this point let us demonstrate the same thing
00:07:45here as well the fractures of the clavicle occur at a junction which is
00:07:50the meeting point of medial two-third of clavicle bone and the lateral one-third
00:07:56of the clavicle bone but according to few authors they divide the clavicle
00:08:00into three parts they say this is the lateral one-third of clavicle then we
00:08:04have got the middle one-third of clavicle and the medial one-third of
00:08:09clavicle so according to this description as we are dividing the
00:08:14clavicle into three parts some of the orthopedicians they are mentioning the
00:08:19fracture in the clavicle is occurring at the junction of lateral one-third and
00:08:23the middle one-third now information is the same it is just the interplay of
00:08:28words but you should be aware of all the descriptions to handle the MCQs and we
00:08:34have got one let us tackle that but since we are here let us just mention
00:08:38few muscles which are attaching to clavicle like we have got a large muscle
00:08:43in the anterior thoracic wall pectoralis major it has several origins but it is
00:08:49also taking origin from the anterior aspect of the medial two-third of the
00:08:54clavicle bone so that is the origin of the pectoralis major muscle insertion
00:08:59will be on the humerus bone which we'll be seeing in a short while now what is
00:09:03attaching to the lateral one-third of clavicle where we had the anterior
00:09:08concavity that is the origin of deltoid muscle which also inserts into humerus
00:09:13but the origin it has multiple origins and one of the origin is clavicle bone
00:09:19so one part of the deltoid muscle is taking origin from the lateral one-third
00:09:24of the clavicle anteriorly exactly a mirror image of that attachment but on
00:09:30the posterior aspect is the insertion of trapezius muscle the upper back muscle
00:09:35so trapezius has origin from the skull bone and the vertebral spines but its
00:09:41insertion is on scapula bone and the clavicle bone since it is coming from
00:09:46the posterior aspect it is inserting on the posterior border of the lateral one-third
00:09:50of clavicle as making a mirror image of the deltoid attachment so that means
00:09:56lateral one-third of clavicle is sandwiched between deltoid muscle
00:10:00anteriorly and trapezius muscle posteriorly we'll be talking about these
00:10:05muscles the attachments once again and this is the question we were talking
00:10:09about it is asking us about the bone clavicle and we have to mark the
00:10:14exception that means the wrong statement here as we notice most of the authors
00:10:20they will mention clavicle bone has no bone marrow cavity so choice A is a true
00:10:25statement and we also have seen clavicle is a long bone but is disposed in
00:10:31horizontal fashion so that is also a correct statement but choice number C is
00:10:36little controversial because we have learnt in grazer anatomy it is mentioned
00:10:41clavicle having only one secondary center two primary and one secondary
00:10:46center so following the grazer anatomy if you are searching for the exception
00:10:50this is the wrong statement and that should be our answer though as I
00:10:55mentioned earlier there are some authors who might say there are two secondary
00:10:59center of ossification for clavicle but doesn't match with grazer anatomy so here
00:11:03we can take this choice number C as the exception and our answer then what about
00:11:08choice number D we have learnt fractures of the clavicle bone are at the junction
00:11:13of lateral one third and medial two third but it can also be mentioned as
00:11:19lateral one third and the middle one third so intermediate third is nothing
00:11:25else but the middle it is just the interplay of some of the words but the
00:11:29information is same junction of lateral one third and middle one third that is
00:11:34where we saw most of the fractures in clavicle are happening so choice number
00:11:38D is also fine the only wrong statement is choice number C and that should be
00:11:42our answer of exception now we have got one question which is about the
00:11:47ligaments which are connecting appendicular skeleton to the axial
00:11:51skeleton in appendicular skeleton we have to include the humerus bone, scapula
00:11:55bone, clavicle bone and weight of the appendicular skeleton needs to be
00:11:59shifted towards the axial skeleton which is the sternum and the ribs which are
00:12:04also called costa so there will be some ligaments involved the question is
00:12:08asking which of the following ligament is not helping us in this weight
00:12:13transmission from the upper limb that is appendicular skeleton to the axial
00:12:18skeleton the sternum and the ribs now before we choose our answer let us look
00:12:22at some diagrams first first of all we should know what is the importance of
00:12:27transmitting the weight of upper limb towards the axial skeleton say there is
00:12:32a case of fall on the outstretched hand so whenever there's a fall on the
00:12:38outstretched hand there are chances of multiple fractures in the upper limb but
00:12:43that doesn't happen because the thrust which is taken by hand bones is shifting
00:12:48to the forearm bones to the humerus bone and from the humerus bone it is
00:12:53shifting to scapula bone, clavicle bone and then to the sternum and the ribs so
00:12:59what is this line of weight transmission? a schematic diagram is given here the
00:13:04hand has taken the thrust from the hand bones the thrust is given to the forearm
00:13:09bones to the humerus bone and from the humerus bone this thrust is passed on to
00:13:13the scapula bone and from the scapula bone it moves on to the clavicle bone
00:13:18that is the line of weight transmission and then from the clavicle bone towards
00:13:22the ribs and the sternum which is basically the axial skeleton so axial
00:13:27skeleton is the sternum and the ribs whereas appendicular skeleton or upper
00:13:32limb skeleton includes the clavicle bone scapula humerus bone and all that now in
00:13:37this weight transmission there are several ligaments involved like one of
00:13:40the important ligament is costoclavicular ligament as the name is
00:13:44suggesting it is attaching to the ribs and the clavicle but it is also attaching
00:13:49to the sternum bone as is evident here so this is the number one ligament which
00:13:54should be answered whenever we are talking about weight transmission of
00:13:57upper limb to the axial skeleton though there are other ligaments also which are
00:14:02important like you see here the coracoclavicular ligament as the name is
00:14:06suggesting it is between the coracoid process of scapula and the clavicle bone
00:14:11and there are several other ligaments like there'll be one interclavicular
00:14:15ligament also which is important for weight transmission you know the weight
00:14:19of the upper limb was shifted to the clavicle and from the clavicle to the
00:14:23sternum there is a ligament which is interclavicular ligament but since it is
00:14:28attaching to sternum also the interclavicular ligaments also help us
00:14:32in transmitting weight to the axial skeleton we need to know this to deal
00:14:36with the questions and now we have to talk about one ligament here which is
00:14:40actually connecting coracoid process of scapula with the acromion process of
00:14:44scapula and as is evident this ligament cannot help us in weight transmission
00:14:50and why is that so? because for weight transmission the ligament must be
00:14:55connecting one bone to the next bone to the next bone to the next bone like the
00:14:59humerus is connected to the scapula is connected to the clavicle and to the
00:15:04ribs or sternum but this coracoacromial ligament is connecting one part of
00:15:09scapula to other part of scapula so it is not connecting one bone with the next
00:15:13bone this ligament cannot help us in weight transmission that gives us the
00:15:18idea to deal with the question and by the way what will happen if these
00:15:22ligaments like costoclavicular coracoclavicular ligaments are damaged
00:15:26compromised in that scenario if there is a fall on the outstretched hand there
00:15:32won't be a proper line of weight transmission working and leading to
00:15:36multiple fractures in the upper limb region let us go back to the question we
00:15:42were dealing with we needed to tell that which of the following ligaments are the
00:15:47exception not helping us in weight transmission if you look at the
00:15:50costoclavicular ligament that is the most important ligament for weight
00:15:54transmission and what about the coracoacromial ligament yes it is the
00:15:59coracoacromial ligament that should be the answer of exception because we have
00:16:03seen coracoid processes on the scapula, acrobin process on scapula this is
00:16:08scapula to scapula ligament cannot help us in weight transmission then what
00:16:13about the coracoclavicular yes coracoid process of scapula to the clavicle in
00:16:18the line of weight transmission and interclavicular we have mentioned
00:16:22interclavicular ligament is between the clavicle but also attaching to sternum
00:16:26one bone to the next bone so you mean to say the answer of exception should
00:16:31remain as twice number B yes now if a question comes which of the following
00:16:36ligament are the most important for weight transmission which is your first
00:16:41answer first answer should always be costoclavicular ligament and number two
00:16:46the coracoclavicular ligament and number three number three four five there are
00:16:51several but here number three will be the interclavicular ligament but
00:16:55obviously this ligament does not help us in the purpose choice B should remain
00:17:00the answer then as we move forward we encounter another question asking for
00:17:05some exception in fact it is about some bony attachment of the muscles and some
00:17:12pairs are given we have to find which pair is incorrectly matched and as we
00:17:18notice these are the muscles found around the shoulder joint now when it
00:17:23comes to latissimus dorsi a muscle of the lower back if you remember we have
00:17:27seen that in a diagram it will be coming and inserting on the bone humerus at the
00:17:32floor of the bicipital groove and this bicipital groove is also called as
00:17:36intertubercular sulcus or intertubercular groove so choice number A
00:17:41is fine there is no problem here we'll be looking at this again in a diagram
00:17:46then what about the choice number B the short head of biceps brachii is it
00:17:51attaching to the tip of coracoid process yes that is correct in fact the
00:17:56tip of coracoid process will have one more muscle taking origin and the name
00:18:00is coracobrachialis muscle and what about choice number C subscapularis a
00:18:05muscle which is under scapula that is the origin and the insertion is on the
00:18:09bone humerus is it at the lesser tubercle yes lesser tubercle is the
00:18:14insertion of subscapularis muscle you mean to say the answer of exception is
00:18:18choice number D yes the answer is choice number D because it is a wrong
00:18:23matching you have to tell the exception and why choice number D is the answer
00:18:28because it is not the teres major it is the teres minor which attaches to the
00:18:33greater tubercle you need to remember one mnemonic it is the sit muscles which
00:18:38sit on the greater tubercle and what is the expansion of sit muscle that's for
00:18:42supraspinatus, I for infraspinatus and T for teres minor so if it is the
00:18:48teres minor attaching to greater tubercle on the bone humerus then where
00:18:52is teres major attaching? teres major is attaching to the medial lip of
00:18:57bicipital groove on the upper end of the bone humerus lady between two majors
00:19:02what is this lady between two majors that we will find out but it is not the
00:19:08teres major it is teres minor which inserts on greater tubercle hence the
00:19:13answer of exception should remain choice number D and let us look at the detailed
00:19:17diagrams now in the present diagrams we will be looking at some of the features
00:19:21of the bone scapula from the anterior view as well as from the posterior view
00:19:27here we are focusing upon the right-sided scapula and as you notice
00:19:30this is the front view or anterior view of right-sided scapula, scapula cannot be
00:19:37seen from the front view as such because it is lying on the posterior thoracic
00:19:41wall so it must be seen from the posterior view like here it be more
00:19:46clearly evident now if we look at the scapula it'll have three angles and the
00:19:52three borders there is a medial border, a lateral border, a superior border which
00:19:57you can show here as well this is going to be the medial border of scapula as
00:20:01mentioned here and then we have got the lateral border of scapula then we have
00:20:06got one superior border of scapula as well then what about the angles we have
00:20:11got three angles there is a superior angle of scapula, inferior angle of
00:20:16scapula and at the lateral angle of scapula there is a modification we are
00:20:21calling it as the glenoid cavity of scapula that is where the head of the
00:20:26humerus will come and form a ball and socket joint which is shoulder joint so
00:20:31that is the lateral angle of scapula. Now there are two processes we can talk
00:20:35about if you remember the coracoid process and the chromium process the
00:20:40coracoid process is projecting anteriorly as is evident here and so is
00:20:45the acromion process but acromion process comes from posterior aspect
00:20:50actually it is the continuation of the spine of the scapula which lies
00:20:55posteriorly and when it projects anteriorly it is converted into acromion
00:20:59process so let us look at the spine of scapula which is actually evident from
00:21:05the posterior view and as you see it is the right-sided scapula itself seen from
00:21:10the posterior view this is the spine of scapula which we are talking about and
00:21:15as we follow it anteriorly it will convert itself into acromion process of
00:21:20the scapula and once again you can talk about the three borders and the three
00:21:25angles of scapula like we have seen there is a medial border of scapula this
00:21:30was from the front view this is medial border of scapula from the posterior
00:21:34view and what about the lateral border this is lateral border for the front
00:21:39view this is the lateral border from the posterior view as is evident here and
00:21:44then we can show the superior border as well this is going to be the superior
00:21:49border and that's where we have superior angle as well so the superior angle from
00:21:53the front view this is superior angle from the posterior view and we have got
00:21:58one inferior angle and what was the modification at the lateral angle this
00:22:03is the lateral angle from the front view and that is the lateral angle from
00:22:07the posterior view this is the glenoid cavity where you have got the head of
00:22:11humerus articulating so we are looking at the posterior view of the right
00:22:15shoulder joint here and now we need to talk about some of the muscle
00:22:20attachment on scapula in these diagrams we'll be talking about some of the
00:22:24muscles attaching to the bone scapula we need to remember that if a muscle is
00:22:29taking origin from the scapula it has to insert on a next bone maybe it is the
00:22:34humerus bone or the radius ulna bone wherever the insertion is that insertion
00:22:40moves that bone moves the origin remains fixed but then there can be some muscles
00:22:44which are taking origin from one bone say for example ribs and inserting on
00:22:50the scapula bone in that case it's the insertion which moves so you can move
00:22:54the scapula also provided that you had insertion of a muscle upon that let us
00:22:59first talk about the muscles which take their origin from the scapula bone we'll
00:23:03make a diagram ourselves showing the anterior view of the right scapula here
00:23:08as we know it has a middle border, a lateral border, a superior border and it
00:23:12is the lateral border where we have got the glenoid cavity we also understand
00:23:17that if we are looking at the scapula from the front view it will have an
00:23:21anterior projection called as the coracoid process which you can mark here
00:23:25this coracoid process we have learned there are two muscles taking origin then
00:23:30we were talking about a question and those muscles are the shorted of biceps
00:23:35brachii and the other one the other one is called as the coracobrachialis
00:23:41muscle so attaching to the tip of the coracoid process we have got the origin
00:23:47of coracobrachialis muscle as well these are all coming as MCQs then what
00:23:52are the other muscles taking origin now you have talked about the short head of
00:23:56biceps taking its origin from coracoid process what about the long head of
00:24:00biceps brachii it is taking its origin from the supraglenoid tubercle and
00:24:05remember one peculiar thing about the long head of biceps brachii which is
00:24:10taking origin from supraglenoid tubercle the tendon is intracapsular it goes
00:24:15inside the capsule of shoulder joint so what is peculiar about that see the
00:24:21muscles the tendons they are never intracapsular they are always
00:24:25extracapsular except few like the long head of biceps brachii tendon which is
00:24:30intracapsular then what about the long head of triceps muscle the long head of
00:24:35triceps muscle takes its origin from infraglenoid tubercle now what about the
00:24:40tendon of the long head of triceps is it also intracapsular no as I told you
00:24:45muscles never go inside the capsule they're always extracapsular except few
00:24:51of them then we have to talk about a muscle which is undercover of scapula
00:24:55hence called subscapularis muscle here is the origin of the subscapularis
00:25:00muscle from the subscapular fossa you can show that here as well but if this
00:25:05is the origin of subscapularis muscle then where is the insertion the
00:25:10insertion is on humerus bone if you remember it is on the lesser tubercle of
00:25:15the bone humerus so that means it can move the humerus yes it is the insertion
00:25:19that moves the origin remains static most of the time do we have any muscle
00:25:25which is inserted on scapula because we have just discussed only the origins yes
00:25:29there is one muscle which come from the anterolateral aspect of the ribs and
00:25:34inserts into the medial border of scapula on the anterior or costal
00:25:40surface and what is the name of this muscle that is called as serratus
00:25:44anterior muscles so the serratus anterior muscle is inserted on the
00:25:49medial border of the scapula on the anterior aspect or the costal aspect and
00:25:55serratus anterior can pull the scapula forward as needed in protraction of
00:26:01scapula so when we pull the scapula forward the protraction of scapula it is
00:26:05being done by serratus anterior anyhow we have to talk about some of the
00:26:09muscles attaching to the scapula on the posterior aspect as well so let us draw
00:26:14the scapula posterior view now this being the medial border the superior
00:26:18border the lateral border and on the lateral border we have got the glenoid
00:26:21cavity we have learnt it was the supraglenoid tubercle which was giving
00:26:26us the origin of long head of biceps brachii which was having intracapsular
00:26:32origin whereas the long head of triceps which come from infraglenoid tubercle
00:26:38has extracapsular origin so whatever we have seen from the front view can also
00:26:44be visualized from the posterior view biceps is a muscle which has two heads
00:26:49and is on the anterior arm aspect whereas triceps will have three heads
00:26:53and is present on the posterior aspect of the arm and these are the origins a
00:26:58very prominent structure on the posterior view of the scapula is the
00:27:02spine of scapula so let us draw the spine of scapula which is projecting
00:27:07anteriorly to become the acromion process of scapula can be seen here as
00:27:11well the spine of scapula continuing anteriorly as the acromion process of
00:27:15scapula now once you have discussed this detail there is a muscle which is above
00:27:20the spine and one muscle below the spine so hence called as the origin of
00:27:25supraspinatus muscle and the origin of infraspinatus muscle if it is above the
00:27:30spine supraspinatus muscle origin if it is below the spine infraspinatus muscle
00:27:36origin then we will be looking at some of the muscles attaching to the lateral
00:27:40border and middle border as well but on the dorsal aspect of the scapula we find
00:27:45there is a tereus minor and major muscle taking origin from the lateral border
00:27:50here is the origin of tereus minor muscle on the lateral border of the
00:27:54scapula and you can also draw the origin of tereus major muscle as well even the
00:28:00tereus major muscle is taking its origin from the dorsum of the scapula lateral
00:28:05border of scapula if these are all origins then they will not be moving the
00:28:09scapula can you tell some muscles which are inserting on scapula which are
00:28:13moving the scapula yes they are actually inserted on the dorsal aspect of the
00:28:18medial border of the scapula let us enumerate them now taking origin from
00:28:23the vertebral spine and inserting on the middle border scapula on the dorsal side
00:28:27are rhomboid muscles there is a rhomboid major muscle inserting here which can be
00:28:33shown here in the diagram and then there is a rhomboid minor muscle the
00:28:38insertion is slightly higher so this is rhomboid minor as will be evident here
00:28:42still higher to that is a muscle inserting which can elevate the scapula
00:28:47and since this muscle is helping us to elevate the scapula its name is elevator
00:28:53scapula or levator scapula will be working with the trapezius muscle to
00:28:58elevate the scapula you mean to say trapezius is also pulling the scapula it
00:29:04must be inserted on scapula yes and where exactly it is on the spine of
00:29:09scapula okay but where exactly on the superior border of the spine of scapula
00:29:14let us show the insertion of trapezius muscle here so trapezius muscle is
00:29:19getting inserted on the superior border of the spine of scapula and also the
00:29:23inner or medial border of the acromion process which you can show in the
00:29:28diagram above here as well trapezius muscle is inserting on the superior
00:29:32border of the spine of scapula and the medial or inner border of the acromion
00:29:37process in a J shape fashion and this trapezius which takes its origin from
00:29:43the skull bone and the variable spine is inserting on the spine of scapula pulling
00:29:49the scapula upwards hence elevating it or helping in shrugging of the shoulder
00:29:54now in the same J shape manner there is a mirror image of another muscle
00:29:59attaching to the spine of scapula but it is outer J trapezius is attached in a
00:30:05inner J fashion and it is the deltoid muscle which is attaching in a outer J
00:30:10fashion and what is this outer J fashion it is the origin of the deltoid muscle
00:30:16which you can show here as well the deltoid muscle is taking its origin from
00:30:21the spine of the scapula but inferior border and also the lateral border of
00:30:26the acromion process this is the outer J so we have got one outer J and one inner
00:30:32J it's kind of a mirror image inner J the insertion of trapezius and outer J
00:30:38is the origin of deltoid muscle if it is the origin of the deltoid muscle then
00:30:43where is the insertion insertion is on the hemorrhage bone it takes origin from
00:30:48the spine of scapula insert on hemorrhage bone that is how it can pull the
00:30:53hemorrhage bone and as it is pulling the hemorrhage bone it is a powerful abductor
00:30:58at the shoulder joint we'll be looking at more detailed diagrams of deltoid as
00:31:05well as the trapezius in the later discussions this is just an overview of
00:31:10the muscles attaching to the scapula bone in these diagrams we are going to
00:31:14look at some details on the upper end of the bone humerus presently we are
00:31:20focusing on the right humerus and magnified view you can see here we can
00:31:25talk about the head of the humerus here which is going to articulate with the
00:31:29glenoid cavity of the bone scapula to participate in ball and socket synovial
00:31:35joint that is a shoulder joint so this is the head of the humerus bone
00:31:40articulating with the glenoid cavity of scapula anterior view of right shoulder
00:31:45joint and then we have to tell head of the humerus is a pressure epiphysis it
00:31:50will be helping in weight transmission and it is intra capsular within the
00:31:56capsule of the shoulder joint this is in comparison to the other type of epiphysis
00:32:01which is called traction epiphysis so traction epiphysis versus pressure
00:32:06epiphysis the pressure epiphysis they are intra capsular and they help in
00:32:11weight transmission and then we can talk about traction epiphysis see this lesser
00:32:16tubercle and the greater tubercle both of them are traction epiphysis we have
00:32:23seen that greater tubercle will be more evident posterior superiorly whereas the
00:32:28lesser tubercle is evident anteriorly now both of them may it be the lesser
00:32:32tubercle or the greater tubercle they are called as traction epiphysis because
00:32:38they are formed by some tendons which are pulling on the bone so which
00:32:43tendons are pulling on these tubercles so as to cause traction and resulting in
00:32:48a bony prominence traction epiphysis as compared with pressure epiphysis
00:32:52remember traction epiphysis are always extra capsular outside the capsule of
00:32:59the joint which is quite evident because we have said earlier almost all
00:33:03the muscles are extra capsular there are very few muscles which are intra capsular
00:33:07so these muscles attachment which are extra capsular which muscle is pulling
00:33:12here so as to produce the lesser tubercle traction epiphysis the
00:33:17insertion of subscapularis muscle is here if you remember subscapularis
00:33:23muscle which is under the scapula that is the origin and it will be inserting
00:33:27on lesser tubercle on the bone humerus it can pull the bone humerus traction
00:33:32then which muscles are pulling on the greater tubercle the sit muscles and
00:33:38what is this sit muscles the sit muscles are sitting on the greater tubercle
00:33:43supraspinatus, infraspinatus and teres minor not D major it is the minor which
00:33:50is inserting on the greater tubercle then where is teres major inserting this
00:33:55major is actually inserting here on the medial lip of bicipital groove lady
00:34:00between the two majors and what is this lady between the two majors actually it
00:34:06is a pneumonic which will help us to remember the insertion of the three
00:34:09muscles here you remember the lady latissimus dorsi a muscle from the lower
00:34:14back comes and inserts here on the floor of the bicipital groove between the two
00:34:19majors that's what we need to discuss here but first we have to find out the
00:34:24details of the bicipital groove which is also called intertubercular groove or
00:34:28intertubercular sulcus between the two tubercles and the magnified view is here
00:34:33between the two tubercles we have got the intertubercular sulcus or it is
00:34:39called intertubercular groove or bicipital groove let us demonstrate that
00:34:43here this is the groove we are talking about and passing through this groove is
00:34:49the long head of biceps brachii tendon hence it is also called bicipital groove
00:34:54now intertubercular sulcus has a floor and on the floor we see the insertion of
00:35:00the latissimus dorsi muscle so on the floor of the bicipital groove we have
00:35:05the insertion of the latissimus dorsi muscle flanked by two majors the
00:35:10pectoralis major and teres major the pectoralis major inserting on the
00:35:15lateral lip of the bicipital groove as written here whereas it is the teres
00:35:20major which is inserted on the medial lip of bicipital groove that is why we
00:35:26are having a mnemonic lady between two majors the lady L is latissimus dorsi
00:35:31and the majors are anteriorly coming pectoralis major and coming from
00:35:36posterior side teres major let us look at a better diagram to appreciate their
00:35:42insertions at this particular location as we look at the front view of the
00:35:47right humerus bone at the upper end and discuss the attachments lady between two
00:35:53majors you'll find this is the area in a magnified view and the lady that is
00:35:57latissimus dorsi is coming from the lower back so originating from lower
00:36:03back this muscle will be inserting at the floor of the bicipital groove and
00:36:07let us look at its attachment here we are shedding the fibers of the muscle
00:36:12and then we can show its attachment on the humerus at the floor of the
00:36:16bicipital groove here lady between two majors and then we can talk about one
00:36:21major attaching to the lateral lip of bicipital groove and one on the medial
00:36:25lip of the bicipital groove medially you have got the teres major as evident here
00:36:30and laterally we have got pectoralis major let us look at the insertion of
00:36:34pectoralis major then as we are telling it is on the lateral lip of bicipital
00:36:39groove and then we can focus upon the teres major here we see it is major
00:36:44takes its origin from the lateral border of the scapula but on the dorsal aspect
00:36:50and from there you can show the muscle fibers running towards the humerus bone
00:36:54and inserting on the medial lip of bicipital groove now here we have to
00:36:59understand these muscles they contribute to the walls of the axilla axilla is the
00:37:03armpit which will be having anterior wall and posterior wall in the anterior
00:37:07wall you have to remember two muscles and in the posterior wall you have to
00:37:11remember three muscles anteriorly we have seen one of the muscle pectoralis
00:37:15major attaching here there is one more muscle pectoralis minor and together the
00:37:20pectoral major and minor form anterior wall of the axilla of the armpit
00:37:25whereas posteriorly you have got three muscles this lady goes with the posterior
00:37:29major and contribute to the posterior wall of axilla so in the posterior wall
00:37:33of axilla you have latissimus dorsi, the teres major and one more muscle that
00:37:37muscle is under the scapula has the name subscapularis it takes its origin
00:37:41from subscapular fossa and then inserts on the lesser tubercle here so this is
00:37:46the subscapularis muscle the origin and the insertion so these are the three
00:37:51muscles contributing to posterior wall of axilla inferior to superior it is the
00:37:55latissimus dorsi, teres major and the subscapularis muscle now let us draw a
00:37:59diagram ourselves for the upper end of the right humerus showing the lesser
00:38:03tubercle, greater tubercle, inter tubercle sulcus and the muscle
00:38:07attachments which we have just mentioned so here is the upper end of right
00:38:11humerus and we are showing the greater tubercle and the lesser tubercle and
00:38:16then we understand between the two tubercles we have got inter tubercular
00:38:20sulcus which is also called as inter tubercular groove or bicipital groove
00:38:25the name bicipital groove comes because the tendon of the long head of
00:38:29biceps brachii is passing here as we remember this long head of biceps
00:38:34brachii takes its origin from the supraglenoid tubercle above the glenoid
00:38:39cavity and passes through the inter tubercular sulcus then we can also show
00:38:44the two lips of the bicipital groove as we understand there is a lateral lip of
00:38:48bicipital groove and there is the middle lip and we have discussed the lady that is
00:38:53latissimus dorsi at the floor of bicipital groove which will be attaching
00:38:57here whereas on the lateral lip you have one of the major the pectoralis major
00:39:01and on the medial lip on the medial lip we have discussed it is the teres major
00:39:06so there are three muscles inserting here out of which we have discussed the
00:39:10pectoral major is contributing to anterior wall of axilla whereas the
00:39:14teres major and latissimus dorsi contribute to posterior wall of axilla
00:39:18along with one more muscle which was inserted on the lesser tubercle and that
00:39:22was the subscapularis muscle whereas if we are talking about the greater
00:39:26tubercle it is not evident from the anterior aspect but it is posterior
00:39:30superior and on that you have three muscles attaching the sit muscle the sit
00:39:35muscle sitting on the greater tubercle of the bone humerus as for supraspinatus
00:39:40I for infraspinatus and T for teres minor the teres minor not the major as
00:39:45the teres major attaches to the medial lip of bicipital groove and we need to
00:39:50understand this lesser tubercle and greater tubercle they are traction
00:39:53epiphysis produced by traction of the muscles attaching there they are
00:39:58extracapsular muscles are usually extracapsular with few exceptions like
00:40:03we have seen long head of biceps brachii the tendon is intracapsular it is a
00:40:08peculiar finding as such and now we are going to look at some of the details at
00:40:13the lower end of the humerus bone one diagram is from the front view and the
00:40:18other diagram is looking at the right humerus only but from the posterior view
00:40:23now before we move on to the posterior view let us have the details of the
00:40:28anterior aspect we can zoom the diagram a little bit to have a better look at
00:40:33the lower end of the humerus so there we are going to have the two condyles and
00:40:39epicondyles at the lower end of the humerus there is a lateral condyle and
00:40:44medial condyle the lateral condyle is called as the capitulum and it is
00:40:49working like a cap on the lateral bone that is the radius bone in the
00:40:55articulation so this is the capitulum like a cap on the head of the radius
00:41:00bone and it is actually the lateral condyle of the bone humerus on the
00:41:04middle side there is a pulley shaped structure hence called as the trochlea
00:41:09so trochlea is the medial condyle at the lower end of the bone humerus and is
00:41:14going to articulate with the trochlear notch of the alar bone here contributing
00:41:20to the elbow joint which is basically humeral joint. now may it be the
00:41:25trochlea or the capitulum both of them are pressure epiphysis and they are
00:41:30involved in weight transmission so pressure epiphysis are intracapsular
00:41:36within the capsule of the joint here you can notice the attachment of the capsule
00:41:41of the elbow joint and it is evident that both the condyles are intracapsular
00:41:47this is in contrast to the traction epiphysis which are always extracapsular
00:41:53so where do we see the traction epiphysis here it is the lateral
00:41:56epicondyle and the medial epicondyle so here is the medial epicondyle which is a
00:42:02traction epiphysis and is extracapsular and we can also look at the lateral
00:42:07epicondyle another traction epiphysis but which muscles are producing traction
00:42:13here actually the lateral epicondyle is the common extensor origin the extensor
00:42:18muscles of the posterior forearm they take origin from here as you will notice
00:42:23at the lower end of the humerus lateral epicondyle anteriorly we have the common
00:42:29extensor origin giving extensor muscles of the posterior forearm similarly we
00:42:34have got one common flexor origin the anterior aspect of the medial epicondyle
00:42:40and it will be giving anterior forearm muscles which are flexor muscles hence
00:42:44the name is common flexor origin sometime this medial epicondyle or
00:42:49common flexor origin can be inflamed medial epicondylitis golfer's elbow
00:42:55whereas the common extensor origin the lateral epicondyle can be involved in
00:43:00tennis elbow if you're talking about tennis elbow lateral epicondylitis and
00:43:05if you're talking about golfer's elbow medial epicondylitis so in golfer's
00:43:10elbow the common flexor origin is involved the medial epicondyle is
00:43:15involved as compared with the tennis elbow where you have the involvement of
00:43:18lateral epicondyle there is itis inflammation now let us look at some
00:43:23details on the posterior aspect of the humerus as well and that is the diagram
00:43:29here again you can notice this is the capitulum sitting like a cap on the head
00:43:35of the radius this is the lateral condyle of the bone humerus whereas
00:43:40trochlea shaped is the medial condyle it is evident from the posterior aspect as
00:43:46well and as we have mentioned since they are pressure epiphysis involved in weight
00:43:52transmission they are intra capsular inside the capsule of the elbow joint as
00:43:58you can see this is the attachment of the capsule of the elbow joint now you
00:44:02will notice one more thing here even the olecranon fossa is intra capsular what
00:44:08is this depression for this depression is for the olecranon process of the bone
00:44:13ulna as you notice here this is the posterior view of the ulna bone the
00:44:18olecranon process going into the olecranon fossa at the lower end of the
00:44:24bone humerus on the posterior aspect so olecranon fossa is also intra capsular
00:44:30comes as a question so what is the attachment of the capsule then?
00:44:34attachment of the capsule is excluding the epicondyles but including the
00:44:39condyles so it will be the capsular attachment for the elbow joint from the
00:44:44posterior aspect and the same you can discuss from the anterior aspect as well
00:44:49as we are talking about the capsular attachment it is understood it has to
00:44:54include the condyles and some fossas within the capsule and which fossas are
00:44:59seen from the anterior aspect see the radius bone which was articulating with
00:45:03the capital M will be coming in contact the lower end of the humerus during
00:45:08elbow flexion so this space the depression is meant for the radial bone
00:45:13and is called radial fossa even that is intra capsular and during elbow flexion
00:45:18the coronoid process of ulna will come in contact with lower end of the humerus
00:45:24as you see the coronoid process is coming to the fossa in the lower end of
00:45:29humerus and it is also intra capsular we are calling it as the coronoid fossa
00:45:34accordingly to receive the coronoid process of the bone ulna so eventually
00:45:39we can tell made with a capital M trochlea or the radial fossa coronoid
00:45:44fossa they are all intra capsular the extra capsular are the epicondyles the
00:45:50lateral epicondyle and the middle epicondyle and they are the examples of
00:45:54traction epiphysis traction by the common extensor muscle origin and common
00:45:59flexor muscle origin muscles of axial appendicular skeleton when we talk about
00:46:05these muscles they are coming from the axial skeleton to the appendicular
00:46:09skeleton initially we will look at the anterior aspect then we have to
00:46:13enumerate the posterior aspect muscles as well but these are the muscles which
00:46:17are coming from the axial skeleton towards the appendicular skeleton so what
00:46:21do we include in the axial skeleton in the axial skeleton you have to include
00:46:26the sternum and the ribs as you see here the sternum bone and the ribs they are
00:46:32considered as the axial skeleton and from there some muscles are going
00:46:36towards the appendicular skeleton which includes the shoulder girdle the humerus
00:46:41the scapular bone the clavicle bone the bones which are shown in green color they
00:46:46constitute the appendicular skeleton and even here we are specifically focusing
00:46:51upon the pectoralis major and the serratus anterior though the pectoralis
00:46:57minor and subclavius may also sometime come in the questions but our focus
00:47:03should remain upon these two major muscles the pectoralis minor is a small
00:47:07muscle under pectoralis major and when it comes to subclavius it is a muscle
00:47:11under the bone clavicle presently let us move on to this large muscle in the
00:47:16pectoral region the pectoral major it is a large muscle on the anterior thoracic
00:47:22wall and is a convergent muscle means its origin is quite extensive but the
00:47:28insertion is where the fibers are converging so big origin and smaller
00:47:32insertion the fibers are converging convergent fibers and along with the
00:47:38fibers being convergent it is also having spiral fibers now what do we
00:47:43understand by the term spiral let us look at that aspect as well by first
00:47:48looking at the origin of the muscle it originates from the anterior aspect of
00:47:53the clavicle bone sternum bone and the costal cartilages attaching there of the
00:47:58upper ribs and a lower origin from external oblique aponeurosis there is a
00:48:03muscle in the anterior abdominal wall external oblique muscle its aponeurosis
00:48:08gives the lower fibers of pectoralis major muscle origin the same you can
00:48:13depict here as well it has a clavicular origin and a sternal origin from the
00:48:19anterior surface of the sternum along with the costal cartilages of the upper
00:48:23ribs giving some fibers and then we have got external oblique aponeurosis as the
00:48:28origin and after taking such an extensive origin the fibers are now
00:48:32converging into a narrow area that will be the insertion which is lateral lip of
00:48:38the bicipital groove if you remember we have discussed lady between two majors
00:48:43and this is the lateral major pectoralis major now there is one more description
00:48:47when the fibers are inserting on the lateral lip of bicipital groove the
00:48:51upper fibers are inserting at a lower level whereas the lower fibers are
00:48:55inserting at the upper level you can see that here the muscle is having spiral
00:49:01fibers it is twisted by 180 degree at the insertion that means the upper
00:49:06fibers of the muscle as you follow them they are going to be inserted at a lower
00:49:12level and if we are talking about the lower fibers then you will see they are
00:49:17going to be inserted on the upper aspect here so there is basically spiraling of
00:49:23the fiber by total of 180 degree and that is why it is known as a spiral
00:49:29muscle it will become more evident when you look at a magnified diagram see the
00:49:33upper or the clavicular fibers as they are coming they are going to be
00:49:37inserted at a lower level and if you are comparing them with the lower fiber
00:49:42you notice that they are spiraling now to be inserted at the upper aspect of
00:49:47the insertion level so what it means is there is a total of 180 degree spiraling
00:49:54of the fibers while they are inserting it becomes more evident when you look at
00:49:58this diagram this is the clavicular origin the upper fibers which are now
00:50:03coming to insert at our lower level and if we are talking about the lower fibers
00:50:09which come from the external oblique aponeurosis, lower costal cartilage or
00:50:13lower sternum you can see them these fibers are converging on to upper level
00:50:19and that is what we are telling it is 180 degree spiraling of the fibers. What
00:50:24about the middle fibers? as you see the middle fibers are staying in the middle
00:50:30as evident here which you can show even here the middle fibers taking origin
00:50:35from sternum staying in the middle region so these are converging fibers
00:50:40and they are also spiral fibers. Now we want to talk about its nerve supply and
00:50:45action as well and we notice that this muscle is being supplied by lateral and
00:50:51medial pectoral nerves. As we understand that in the axilla we have brachial
00:50:56plexus there are three chords of brachial plexus the lateral chord will
00:51:00give lateral pectoral nerve and the middle chord of brachial plexus gives
00:51:03medial pectoral nerve and since this muscle is a large muscle supplied by two
00:51:09motor nerves it qualifies being called as hybrid muscle, muscle with more than
00:51:14one motor supply. Now what about its action? remember a simple rule any muscle
00:51:19which will cross the shoulder joint anteriorly and inserts on the humerus
00:51:23bone it will pull the humerus towards the midline or what you call as ADD
00:51:30plus as it is pulling the humerus inside it is also doing medial rotation as is
00:51:35mentioned here adduction and medial rotation plus you have to understand
00:51:40pectoral major especially the clavicular fibers they continue pulling the humerus
00:51:45towards the midline and this is what we call as flexion at the shoulder joint so
00:51:51as you're folding the humerus it is flexion and if you take it back it is
00:51:56extension so which muscles will be doing extension? the muscles which are on the
00:52:01posterior spec they'll pull the humerus posterior causing extension. One more
00:52:05thing as you mentioned if the fibers are crossing the shoulder joint anteriorly
00:52:09they were medial rotator but if the fibers are crossing shoulder joint
00:52:13posteriorly they'll rotate the humerus posteriorly that means lateral rotators
00:52:18so posterior fibers are going to be lateral rotators and also extensors
00:52:23which we'll discuss in some of the muscles which belong to posterior
00:52:27axial appendicular skeleton see here pectoral major is anterior axial
00:52:33appendicular will have some muscles which are posterior and will be
00:52:36antagonizing the action of pectoral major then. Now we are looking at one
00:52:41more axial appendicular muscle the serratus anterior origin is the axial
00:52:47skeleton that is the ribs and insertion into appendicular skeleton that is a
00:52:51scapula it takes origin from the anterior lateral aspect of the upper
00:52:56atrips and then inserts on the medial border of scapula as is evident here we
00:53:01are focusing upon the right-sided serratus anterior and for the origin it
00:53:06has eight digitations anterior lateral aspect of upper atrips and then it is
00:53:11going to insert posteriorly into the medial border of the scapula as is
00:53:17evident here but you have to be careful to mention that it is going to be the
00:53:21costal surface of scapula the anterior or ventral surface of the scapula not
00:53:27the dorsal as is evident in the table it is going to be supplied by long
00:53:31thoracic nerve with root value c567 if you remember it comes directly from the
00:53:37roots of c567 given in the neck region and then it runs on the anterior lateral
00:53:43aspect of the thorax supplying this muscle serratus anterior what is going
00:53:47to be the function of this muscle since it is inserting on scapula it will pull
00:53:51the scapula forward what is called as protraction of scapula so as the scapula
00:53:56is being pulled forward which we are calling as the protraction of scapula it
00:54:01is also holding the scapula close to the thoracic wall and it is also helping in
00:54:08lateral rotation of the scapula now what is the need of rotating the scapula
00:54:13laterally it is important for overhead abduction like if you want to comb your
00:54:18hair you have to do overhead abduction and for that purpose serratus anterior
00:54:23along with trapezius muscle together they are working for overhead abduction
00:54:27see normally in the scapula the glenoid cavity is facing laterally like this and
00:54:33the serratus anterior along with trapezius will help elevating the glenoid
00:54:38cavity from lateral aspect to superior aspect so turning the glenoid cavity
00:54:43superiorly will help us in moving the humerus bone from 90 degree towards the
00:54:48180 degree which is overhead abduction this will see in another diagram as well
00:54:52but in that process the serratus anterior is going to rotate the scapula
00:54:57lateral along with the trapezius muscle so that is why it is mentioned here it
00:55:02rotates the scapula laterally for overhead abduction will become more
00:55:07clear in the next coming diagrams at present we want to know what will happen
00:55:11if there was injury to the long thoracic nerve then it will be paralysis of
00:55:16serratus anterior and there will be winging of scapula and how do you
00:55:20explain winging of scapula let us look at the next diagram before we talk about
00:55:24the pathology we will revise the function of the serratus anterior this
00:55:28is looking from the superior view of the right shoulder joint left shoulder joint
00:55:32and what we mentioned is the scapula bone is being pulled forward what is
00:55:37called as protraction by the muscle called as serratus anterior though it is
00:55:42being held by a small muscle pectoralis minor as well and the serratus anterior
00:55:47since it is inserted on the anterior aspect of the middle border of the
00:55:52scapula it holds the scapula close to the posterior thoracic wall now if one
00:55:57group of muscle is causing protraction there must be another group of muscle
00:56:01which will cause retraction and that you can see are mentioned here some
00:56:06muscles in the back tomboyed major minor and also some fibers of the trapezius
00:56:12they're going to pull the scapula backward or what you are calling as
00:56:16retraction of the scapula so you can understand when we are pushing our hands
00:56:21forward it is protraction of scapula which is being done by serratus anterior
00:56:25held by pectoralis minor but the opposite movement when we are taking the
00:56:29scapula backward towards the midline the retraction of scapula is being done
00:56:33by the back muscles tomboyed major minor and middle fibers of the trapezius
00:56:39muscle now it is obvious that if long thoracic nerve has been compromised and
00:56:44serratus anterior is compromised if you ask the patient to do protraction this
00:56:49is a problem of serratus anterior on the right side you are looking from
00:56:53posterior view you have asked the patient to push the wall which requires
00:56:58protraction of scapula so it will be weak and there is undue prominence of the
00:57:04medial border of scapula now why the medial border of scapula becomes
00:57:08prominent which is also called winging of scapula as if some wings are coming
00:57:13out in the back region it happens because serratus anterior which normally
00:57:17keeps the scapula close to the thoracic wall is unable to so scapula moves away
00:57:23from the thoracic wall and number two if the protractors are weak the retractors
00:57:28become more powerful which are the muscles like rhomboid minor rhomboid
00:57:33major and the middle fibers of trapezius they'll be pulling the medial border of
00:57:37scapula towards the midline making it more prominent so this is a condition
00:57:43called winging of scapula due to paralysis of serratus anterior maybe
00:57:46due to injury of long thoracic nerve then as we proceed we find there is a
00:57:51table showing some muscles belonging to the posterior axial appendicular
00:57:57classification that means attachment is on axial skeleton then on to appendicular
00:58:02skeleton plus there are some muscles which are scapula humeral category where
00:58:06they are originating from the scapula bone but inserting on the humerus bone
00:58:11now wherever the insertion is that portion will move so you can move the
00:58:15humerus using these muscles we'll be looking at all of them one after the
00:58:19other but at the moment let us focus upon the first two that is the upper
00:58:24back muscle trapezius and the lower back muscle latissimus dorsi and among
00:58:28the two let us first focus upon trapezius muscle this trapezius muscle is
00:58:33taking its origin from the occipital bone and the cervicothoracic spines
00:58:38that will be the origin where is the insertion the insertion is on the
00:58:43scapula bone in a J-shaped manner starting from the spine of scapula moving
00:58:49on to acumen process and entirely going on to clavicle bone will have three set
00:58:54of fibers the upper fibers are inserting on clavicle and the middle fibers are
00:59:00inserting on the acumen process whereas the lower fibers are inserting on the
00:59:04spine of the scapula it will become more clear in this magnified view so as we
00:59:09talk about the origin it is taking its origin from the skull bone and the spine
00:59:13of the vertebra as is evident of the skull it is occipital bone and they are
00:59:18cervicothoracic spines the 12 thoracic spines and in the cervical region we
00:59:24have seven attaching the spine is ligamentum nucae so that is giving the
00:59:29attachment and on the occipital bone you have a protuberance and a nuchal line
00:59:33now that was the origin what about the insertion as we mentioned insertion is
00:59:38J-shaped on the spine of scapula the acumen process and clavicle anteriorly
00:59:45we need to zoom this area to look at that J-shape insertion and as we do that
00:59:50here is the J-shape insertion as is evident on the posterior aspect of the
00:59:55scapula bone we have got a spine of scapula which further continues as the
01:00:01acromion process and this acromion process is then articulating with
01:00:05clavicle bone acromioclavicular joint so we can show the clavicle more
01:00:10anteriorly here and then we can mention about the three set of fibers the upper
01:00:14fibers they are going to be inserting on the posterior border of the lateral
01:00:19one-third of the clavicle bone whereas if we are talking about the middle
01:00:25fibers they are inserting on the acromion process the medial margin or
01:00:30you can say the inner margin of the acromion process and when it comes to
01:00:35spine of scapula it receives the lower fibers as are evident here and they will
01:00:40be inserting on the upper lip of the spine of the scapula we need to know the
01:00:46three set of fibers and their respective attachment because that will tell us
01:00:50about the different action of the trapezius muscle and as is evident this
01:00:55muscle is triangular in shape if you combine the two triangular muscles then
01:01:00it will become trapezium shaped and that is why the name trapezium but
01:01:04unilaterally it is triangular in appearance talking about its nerve
01:01:08supply trapezius muscle is supplied by spinal accessory nerve and we would like
01:01:14to know what will happen if this nerve is lesioned but first we must know what
01:01:19are the actions this muscle is supposed to do now since there are different set
01:01:23of fibers inserting like a J-shape fashion we find the upper fibers of the
01:01:30trapezius muscle are going to elevate the clavicle bones scapula bone or the
01:01:35shoulder joint elevation at the shoulder joint shugging of the shoulder
01:01:40and how do you explain the depression then? it will be the inferior fibers of
01:01:45the trapezius as we have seen they can pull the scapula downward hence
01:01:50depression can be explained and what about the middle fibers? middle fibers
01:01:55they can pull the scapula towards the midline what is called as the
01:01:59retraction of the scapula as we have seen it is working along with the
01:02:04muscles like rhomboid major and minor so here you see the trapezius is helping
01:02:09in retracting the scapula then we have to talk about the trapezius working with
01:02:14serratus anterior for overhead abduction abduction more than 90 degree so how does
01:02:20it work with serratus? it will be taking the glenoid cavity superiorly as we know
01:02:25the glenoid cavity normally is directed laterally this the glenoid cavity of the
01:02:31bone scapula here and if we want the haemorrhage bone which is articulating
01:02:35here to make the shoulder joint to move beyond 90 degree of abduction then this
01:02:41glenoid cavity must be facing upwards so which kind of rotation do you require to
01:02:47take the glenoid cavity upwards as we remember along with serratus it will be
01:02:52causing lateral rotation of scapula and for this lateral rotation of scapula
01:02:58which will rotate the scapula outside and the glenoid cavity will now face
01:03:03superiorly taking the haemorrhage bone along with that for more than 90 degree
01:03:07of abduction the fibers working for this movement are upper fibers of trapezius
01:03:13and lower fibers of trapezius they are working in synchronization and rotating
01:03:18the scapula lateral for overhead abduction by turning the glenoid cavity
01:03:22superior now what will happen if there is a lesion of spinal accessory nerve
01:03:26and paralysis of trapezius muscle the first thing is patient will come to us
01:03:31with a drooping of the shoulder and if you ask the patient to shrug the shoulder
01:03:36there will be a difficulty in shrugging the shoulder plus there will be a
01:03:40weakness of overhead abduction as well a difficulty in taking the haemorrhage bone
01:03:46beyond 90 degree of abduction so that will be the clinical presentation of the
01:03:51paralysis of trapezius muscle then we move on to the details of
01:03:55latissimus dorsi muscle a muscle of lower back it is also axial appendicular
01:04:01muscle of the posterior aspect so what is the origin in the axial skeleton you
01:04:06will notice it is taking its origin from thoracolumbar spine and also the
01:04:11thoracolumbar fascia and then some fibers are coming from the hip bone the
01:04:16iliac crest plus there is one more origin and that is the inferior angle of
01:04:22scapula but on the dorsal aspect so these are all the origin what about the
01:04:27insertion as we notice these fibers are now moving towards the appendicular
01:04:32skeleton and we need to zoom to understand two features of this muscle
01:04:36number one a wide origin and a narrow insertion so the fibers are converging
01:04:42convergent muscle and number two it also has spiral fibers and to explain those
01:04:47spiral fibers you can notice just like pectoral major not only it is having
01:04:52converging fibers these fibers take 180 degree spiral before getting insertion
01:04:58as you will notice we zoom this area the lower fibers are turning by 180 degree
01:05:05and they are inserting at a upper level on the bone humerus as we make out and
01:05:11if we talk about the upper fibers which are coming from the lower thoracic
01:05:16spines under cover of trapezius muscle that is where it is taking its origin
01:05:21and also from the inferior angle of scapula these are the upper fibers of
01:05:24latissimus dorsi they are undergoing a spiral of 180 degree and finally
01:05:29inserting at a lower level so as is evident the upper fibers they insert at
01:05:35a lower level whereas the lower fibers they insert at a upper level spiral
01:05:40fibers converging fibers but where exactly is the insertion it is the lady
01:05:45between two majors floor of the bicipital groove on the anterior aspect
01:05:50of the upper end of the bone humerus so that means it will be moving the
01:05:55humerus bone what is the action of this muscle and what is the nerve supply for
01:05:58that we need to look at the next diagram since this muscle is on the dorsal side
01:06:04of the thorax on the lower back it is being supplied by thoracodorsal nerve
01:06:09and if you remember this is a branch of the posterior caudobrachial plexus the
01:06:14stars in the stars the T was thoracodorsal nerve supplying the
01:06:19latissimus dorsi muscle then what is the action of this muscle it will help us to
01:06:23scratch the back and how do we scratch the back see here you can notice this
01:06:29muscle is not helping us in abduction but it is helping in a double the
01:06:33reduction and number two it is not doing lateral rotation it is doing medial
01:06:39rotation that is how you can scratch the back and number three it is not helping
01:06:43in flexion at shoulder joint it is extension at the shoulder joint that is
01:06:48how you can carry out this movement so you mean to say it is extension at the
01:06:53shoulder joint a double reduction and medial rotation yes three activities now
01:06:59if you remember I have mentioned this muscle maybe it is coming from the lower
01:07:03back but its fibers are crossing the shoulder joint anteriorly so as to
01:07:08insert at the floor of the bicep groove and the rule is any muscle whose fibers
01:07:13are crossing shoulder joint anteriorly what the muscle will be doing no one
01:07:18pull the humerus close to the body that is a double the reduction number two as
01:07:23you pull the humerus towards the body it is medial rotation now tell me along
01:07:27with a double deduction and medial rotation can it do flexion no it cannot
01:07:32and why because it is a muscle coming from posterior side so it will pull the
01:07:37humerus posterior that means extension and that is how it is different from
01:07:41pectoral major muscle see pectoral major muscle also the fibers are crossing the
01:07:46shoulder joint anteriorly hence it is helping in a double deduction and medial
01:07:51rotation but since the fibers come from anterior aspect it is causing flexion at
01:07:55the shoulder joint while latissimus dorsi coming from posterior aspect causes
01:08:00extension so these two muscles the pectoral major and latissimus dorsi they
01:08:05work as agonist and antagonist as well what will happen if these two muscles
01:08:09are working together then the flexion of pectoral major and extension of
01:08:14latissimus dorsi will be cancered and together both of them can do number one
01:08:18a double deduction and number two medial rotation so both of them can do a double
01:08:24deduction and medial rotation since the fibers of these muscles are crossing the
01:08:29shoulder joint anterior remember that rule it helps you at several points as
01:08:35we continue with the muscles which are on the posterior aspect and attaching to
01:08:39axial skeleton that being the origin insertion on the appendicular skeleton
01:08:44in this category the posterior axial appendicular muscles we have got three
01:08:49names the levator scapulae rhomboid major and minor this levator scapulae or
01:08:55the rhomboids they are taking origin from cervical thoracic spines and then
01:08:59inserting on the dorsal aspect of the medial border of the scapula so we want
01:09:05to know about their nerve supply and action as well let us first zoom this
01:09:09area to look at their attachments as is evident the levator scapulae muscle is
01:09:14taking its origin for the first four cervical vertebra their transverse
01:09:19process and then inserts on the medial border of scapula till the superior
01:09:24angle of scapula and as the name is suggesting it will be elevating the
01:09:29scapula but look at the vector of the pull of this muscle as you resolve this
01:09:33vector you'll find in the YNX axis this vector is resolving into two
01:09:38components number one of course it is going to elevate the scapula but number
01:09:44two it is also pulling the scapula towards the midline that means it is
01:09:47working like a retractor muscle also now once we have discussed the two action
01:09:53you must remember the chief retractors of the scapula are basically here the
01:09:58rhomboid muscles so levator scapulae the first answer should always be
01:10:01elevation of scapula now talking about the rhomboid muscles there is a minor
01:10:05and major the rhomboidus minor is taking its origin from c7 t1 spine and inserts
01:10:11on medial border of scapula on the dorsal aspect and in the same line even
01:10:17the rhomboidus major called major because it has bigger bulk as compared
01:10:21with the minor it is taking its origin from the spine of thoracic vertebra and
01:10:25inserting on the dorsal aspect of the medial border of scapula just like the
01:10:30other muscles so what are these rhomboid muscles doing you can resolve the vector
01:10:34here this is the way the muscles are pulling because that is the origin this
01:10:38is the insertion they can pull the scapula towards the midline and as you
01:10:42resolve the vector in Y and X component they are chiefly pulling the scapula to
01:10:47the midline so retractors but they have also one vector upwards that means they
01:10:53are also elevators but the thing is if you have to choose between the two
01:10:58answers for rhomboid major minor the chief component is retractor though they
01:11:04can also elevate the scapula so what is the muscle which is elevating the
01:11:07scapula the elevator scapula and which muscles are retractors the rhomboid
01:11:11muscles but along with that they have one more action these three muscles make
01:11:15a group of muscle which will be antagonizing another group of muscle let
01:11:19us discuss that action as well so as we zoom out we notice the elevator scapula
01:11:25muscle is basically elevating the scapula whereas the rhomboid muscles
01:11:30they are the retractors along with one more action which is rotation of the
01:11:35scapula and is explained here so we focus here you know we have discussed
01:11:40when we want to do overhead abduction abduction beyond 90 degree we need two
01:11:44muscles the trapezius and serratus anterior and these muscles they are
01:11:49elevating the glenoid cavity of scapula superiorly as you notice here this is
01:11:55the glenoid cavity of scapula and you have to elevate it for overhead abduction
01:11:59then by the trapezius and the serratus anterior muscle by doing lateral
01:12:05rotation of scapula now this much we have seen earlier but if there is a set
01:12:10of muscle for lateral rotation of scapula then there will be another group
01:12:14of muscle to bring it back and they are the three muscles here elevator scapulae
01:12:20and the rhomboid minor major so look what they are doing they are rotating
01:12:24the scapula backward that means medial rotation the muscles being elevator and
01:12:29the rhomboid major minor and hence they can turn the glenoid cavity back from
01:12:34superior to inferior hence counteracting these two muscles serratus and trapezius
01:12:39and the same is written here the elevator scapulae rotate glenoid cavity
01:12:43inferiorly the same is being done by the rhomboid muscles which involves the
01:12:48medial rotation of scapula what about their nerve supply there's a nerve which
01:12:52is running dorsal to scapula and if you remember this nerve called as the
01:12:56dorsal scapular nerve running undercover of these three muscles supplying these
01:13:00three muscle came directly from the root of brachial plexus the dorsal scapular
01:13:07nerve so dorsal scapular nerve which come directly from the roots of the
01:13:11brachial plexus given the neck region will pass dorsal to scapula and supply
01:13:15the three muscle elevator scapulae rhomboid minor and major as you see the
01:13:20course of the nerve and will be counteracting the nerves like spinal
01:13:25accessory nerve for trapezius lung threshing nerve to serratus anterior it
01:13:29has antagonistic action to this group of muscles