Hello everyone, in this video we are going to discuss about general features and attachments of the humerus. Now humerus is a typical long bone. It has got two ends, upper end and lower end and intervening shaft.
The shaft is having three borders and three surfaces. Regarding side determination, you can watch my separate video. So here I have right humerus with me and let's just start with the general features and attachment of it. First is the upper end. The upper end is having a head which is globular, a neck which is constricted, a lesser tubercle which is a bony prominence which is facing from in front you can see over here and greater tubercle which is another bony prominence which is situated on lateral aspect and in between these two there is inter tubercular sulcus.
So upper part of this inter tubercular sulcus is included in upper end. So these many parts are there. in upper end. Let's see individual parts. Now first comes the head which is more than one third of a sphere which is smooth.
It is covered by articular cartilage. It is articular. It articulates with corresponding glenodal cavity of scapula which is again articular which is covered by articular cartilage and together these two will form glenohumeral articulation or shoulder joint. So when you compare both the articular surfaces, this is head of humerus and this is glenodal cavity, you can easily make out that glenodal cavity is less extensive and shallower as compared to the size of head of humerus and this will help in increasing range of movement. You can see over here the head of humerus can easily rotate, can easily move in different directions.
As I mentioned the head is covered by articular cartilage or highline cartilage which is thicker in the center whereas it is thinner in the periphery. So when you see humerus from in front you can easily make out that the head is directed upward and medially you can see over here whereas when you see it from above you can clearly make out that it is not only directed upward and medially but it is also directed slightly backward. Now to make it more easier to understand what I have done is I have tied a pencil along the long axis of the lower end of the humerus mimicking it as a long axis of the lower end and if I put this pointer along the long axis of the head you can clearly make out that the long axis of the head is twisted backward. okay it is not in line with the long axis of the lower end but it is little bit twisted backward so it is directed upward medially and slightly backward now the same thing has been explained in this diagram what you can see is this is a superior view of right humerus and the outline of upper and lower end are shown so the outline of upper end is drawn with orange color and lower end with blue color so what you can see is head of humerus, lesser tubercle, greater tubercle showing upper end whereas medial epicondyle outline of trochlea, capitulum and lateral epicondyle of lower end. Now there are certain axis drawn so when you draw an axis which is passing from tip of medial epicondyle to the tip of lateral epicondyle then it is termed as axis through distal end or it is also termed as inter epicondylar line another axis is drawn which is termed as articular axis of head which which should pass through center of the head through greater tubercle now that is what we have seen that there is a little bit posterior displacement of head of the humerus as compared to the long axis of the lower end or inter epicondylar line so there is formation of an angle between these two and that is termed as angle of retroversion now over here another angle is shown and that is termed as angle of humeral torsion.
Now what is it? It is an angle between the articular axis of head and perpendicular plane which is perpendicular to the axis which is passing from distal line right. So an angle is formed between these two which is termed as angle of humeral torsion.
Now next is a muscular impression which is termed as laser tubercle or laser tuberosity. The laser means we have got another greater one. So the anterior bony prominence or muscular impression is termed as laser tubercle or laser tuberosity which receives insertion of subscapularis muscle.
The lateral margin of lesser tubercle is sharp and it is separated from greater tubercle by upper part of inter tubercular sulcus. Now this part of inter tubercular sulcus will provide attachment to transverse humeral ligament. The most lateral part of upper end is greater tubercle.
which is separated from laser tubercle by upper part of intertubercular sulcus. Now when you connect humerus with the scapula you can clearly make out that the lateral convex prominent part of the greater tubercle projects beyond the acromion. This is acromion so this is projecting greater tubercle and this is responsible for rounded contour of the shoulder. Now in leaving portion is covered by deltoid which is separated by subacromial bursa which is deep to it now upper and posterior aspect of this greater tubercle present three flat muscular impressions one over here you can see if i bring it bit closer you can clearly make out this is the first flat muscular impression over here will be second and below to it over here will be third but the bone is bit broken over here but the third one would be over here so there are three flat impressions and three muscles are attached respectively from above downward namely supraspinatus infraspinatus and teres minor so three flat impressions for three muscles so if we consider attachment of subscapularis along the laser tubercle and the three muscles attached to the greater tubercle these four muscles subscapularis, supraspinatus, infraspinatus and teres minor. Together these four will form rotator cuff and that increases stability and strength of the shoulder joint.
Now the fourth bony landmark in upper end is neck. There are three types of necks, anatomical neck, surgical neck and morphological neck. The anatomical neck is a constriction situated just next to the head. So this is anatomical neck you can clearly make out okay all around there is a constriction This is termed as anatomical neck now next is surgical neck which is a constriction continuous with cylindrical shaft So when the upper end continues with cylindrical shaft at the junction there is a constriction this portion This is termed as surgical neck. Why it is termed as surgical neck?
because posteriorly it is related to axillary nerve which is also termed as circumflex nerve and as this portion is constricted it is vulnerable for fracture during fall in outstretched hand so that leads to damage of this axillary nerve and secondarily the deltoid which is supplied by axillary nerve will get paralyzed so that's why this is termed as surgical neck third is morphological neck which is an imaginary line situated approximately 0.5 cm above the surgical neck. So somewhere over here the morphological neck is situated. Now what is morphological neck?
It is nothing but presence of or line of presence of epiphytial plate of hyaline cartilage which is found in young humerus. So in adult humerus that has got fused so we won't be able to see the morphological neck but in case of young humerus Obviously over here along this line we will find the epifacial plate of the hyaline cartilage so that is morphological neck. Now along the anatomical neck it provides attachment to the capsular ligament of the shoulder joint with two exceptions. Number one is along the inter tubercular sulcus where we have discussed it is providing attachment to transverse humeral ligament.
So instead of attaching to the bone over here in this region. the capsule is attached to the transverse humeral ligament leaving a gap deep to it and this gap will allow passage of tendon of long head of biceps along with its sinoval shape second exception is along the medial aspect instead of attaching to the anatomical neck the capsule is attached one centimeter below to it along the surgical neck so inferiorly the capsule is lax and this will permit wide range of moment of humerus specifically abduction Next to the upper end is shaft on cross section in upper half It is cylindrical and in lower half the cross section is triangular Being a typical long bone. It has got three borders and three surfaces namely anterior medial and lateral borders and intervening and entromedial entrolateral and posterior surfaces.
Let's see individual borders and surfaces First is anterior border which extends from greater tubercle above to the line between radial fossa and coronoid fossa below over here. So this is the extent of anterior border. Now along its commencement it forms lateral margin of intertubercular sulcus. So this is the commencement of anterior border beyond greater tubercle.
Okay and along its course it limits the delta tuberosity which we will discuss later on this is the delta tuberosity which is situated along the entrolateral surface so along its course it limits delta tuberosity and in lower half it becomes more pronounced you can clearly make out anterior border and below as we have discussed it ends in between radial fossa and this coronoid fossa Next is medial border and you can recognize it from lower end. So in the lower end this is medial epicondyle and beyond medial epicondyle a sharp bony ridge commences. This is nothing but medial border.
So it is better to identify medial and lateral borders from lower end. So this is medial border and in the middle it forms a rough strip, small rough area you can see over here. and beyond that it is continuous as medial leap of intertubercular sulcus.
So over here you can say that the medial border commences as medial leap of intertubercular sulcus in upper half and then somewhere in the middle it forms a rough strip and below it is continuous as sharp bony ridge which is nothing but medial supracondylar ridge. so this sharp ridge is also termed as medial supracondylar ridge similarly to identify lateral border you can start from lateral epicondyle and beyond that there forms a sharp bony ridge you can see over here this is lateral supracondylar ridge which is nothing but part of lateral border of humerus so beyond the tip of lateral epicondyle this is lateral border initially it is lateral supracondylar ridge and above it fades away in the middle portion along the line of spiral groove beyond that it is continuous behind this posterior limb of delta tuberosity this is delta tuberosity it has v shaped structure which is having anterior and posterior limb so behind this posterior limb the lateral border is continuous above and it goes to and behind the greater tubercle along its posterior margin so this is entirely lateral border and as I have said you can identify it from below upward beyond lateral epicondyle now next is surfaces as I have mentioned it has got 3 surfaces so between this anterior border and medial border is anteromedial surface between anterior and Lateral border is the entero lateral surface and between medial and lateral borders posteriorly is the posterior surface now, let's see first Enteromedial surface in upper one-third this enteromedial surface forms inter tubercular sulcus You can see over here So as we have discussed in upper part it is situated between the two tubercles and below it is the entero medial surface Which forms this inter tubercular sulcus? Now as we have discussed this sulcus has got medial lip and lateral lip and a floor.
So the medial lip receives insertion of teres major muscle. Lateral lip receives insertion of bilaminar insertion of pectoralis major muscle and in the floor there is insertion of latissimus dorsi. The groove itself lodges tendon of long head of biceps brachii along with its sinoval sheath which is coming from the joint and from below one ascending branch goes inside and that is a branch of anterior circumflex humeral now along the medial border in the middle part as we have discussed there is a rough strip now this rough strip receives insertion of coracobrachialis and below to that generally along the medial border but over here in this case it is situated near the anterior border there is a nutrient foramen you can clearly see over here and this is directed downward okay so the upper end of humerus is growing.
Now lower half of entromedial surface along with related anterior border and lower half of entrolateral surface. These three structures will provide origin to brachialis muscle. Now this medial supracondylar reach will provide attachment to medial intermuscular septum which will divide anterior and posterior compartment. or flexor compartment in front and extensor compartment behind somewhere in the middle this medial intermuscular septum is pierced by ulnar nerve and superior ulnar collateral artery so from anterior compartment the ulnar nerve along with the corresponding artery will enter into posterior compartment of arm now lower part of this medial supra condylar reach just in front of medial intermuscular septum over here This portion provides origin to humeral head of pronator teres muscle.
Sometimes along the entromedial surface approximately 5 cm above the medial epicondyle, somewhere over here, we may find a hook-like bony structure which is termed as supracondylar process. Now this supracondylar process is generally connected with the medial epicondyle by a fibrous band. This connecting fibrous band is termed as ligament of shrudas which is phylogenetically a remnant of third head of coracobrachialis.
Now this fibrous band may compress median nerve and brachial artery. Now next surface is entrolateral surface which is situated between anterior border and lateral borders. Now in upper part you can clearly see a v-shaped rough area this is termed as deltoid tuberosity which receives insertion of deltoid muscle now upper part of the entrolateral surface above to this delta tuberosity this portion is covered by deltoid muscle and deep to that deltoid muscle we may find an extension of subacromial bursa separating muscle and the bone now below to delta tuberosity lower half of entrolateral surface provides origin to brachialis muscle that we have discussed along with the anterior border and corresponding entromedial surface.
Now the lateral supracondylar reach just in front of it forms a narrow rough strip. So if I bring it closer you can clearly make out there is a formation of narrow rough strip see this. Now this will provide attachment to lateral intermuscular septum.
So like medial intermuscular septum which is attached to the medial supracondylar reach the similar septum over here will separate anterior and posterior compartment or flexure and extensor compartment and in upper part the lateral intermuscular septum is pierced by radial nerve. So the radial nerve at this point will come in front from posterior to anterior compartment and it is accompanied by anterior descending branch of profunda brachii artery which will take part in formation of anastomosis around elbow. Now the same rough narrow strip in upper 2 third will provide origin to brachioradialis whereas in lower 1 third this strip will provide origin to extensor carpi radialis longus muscle.
Next is posterior surface which is found between medial and lateral borders. So this is the posterior surface which is interrupted by an obliquely running spiral groove or radial groove which will be extending from medial border to lateral borders. It is very faint over here but you can imagine a spirally running spiral groove or radial groove which is directed from medial to lateral in spiral manner extending from medial to lateral borders.
This spiral groove is lodged in living by radial nav and profunda brecai vessels. So somewhere over here will be the spiral groove and its upper margin is bounded by an oblique reach you can see over here this oblique reach will provide attachment to lateral head of triceps now the posterior surface above to this oblique reach in living is covered by deltoid muscle as well as this surface is related to axillary nerve and posterior circumflex umbral vessels at the level of surgical neck of humerus. rest of the posterior surface below spiral groove provides origin to flashy medial head of triceps muscle.
next is lower end which is expanded side to side and it is broadly divided into articular and non-articular areas. the articular areas include capitulum and trochlea whereas non-articular areas include radial fossa coronoid fossa olecranon fossa medial epicondyle and lateral epicondyle now let's see first capitulum which is less than half of a sphere which is articular in front and below whereas posteriorly it is non-articular the articular surface is covered by Highline cartilage or articular cartilage and it will articulate with superior articular surface of head of radius See this this is right radius. This is its disc like head and this is its superior articular surface So both the capitulum and this articular surface will come in contact like this and together they form part of elbow joint So during extension the inferior Articular surface of capitulum will come in contact with the head whereas during flexion the anterior articular surface of the capitulum will come in contact okay whereas posterior aspect of capitulum is non-articular so this is how during flexion and extension the capitulum and head of the radius will come in contact next is the trochlea which is an asymmetrical pulley it has got a medial flange and lateral flange the medial flange is more extensive you can see over here which is approximately six millimeter below the level of lateral flange and so as it is an asymmetrical pulley like capitulum it has articular surfaces which is covered by articular cartilage so it has got anterior inferior and posterior articular surfaces and this articular surfaces will come in contact with the trochlear notch of ulna let me show you so this is right ulna with its trochlear notch and it has got two processes coronary process and olecranial process in between these two there lies trochlear notch and which will fix with this trochlea like this okay so during extension the posterior and inferior articular surfaces will come in contact with trochlear notch of ulna whereas the same trochlear notch will come in contact with anterior articular surface of trochlea during flexion okay so this is how it looks during flexion and this is during extension so all these three articular surfaces will come in contact with trochlear notch during various moments at elbow joint now as i mentioned the trochlea is asymmetrical and the medial margin is extensive it is approximately 6 mm below the level of the lateral margin and this will disturb the alignment of the humerus with the ulna right so when you articulate both there is always formation of an angulation between these two and this is termed as carrying angle so when the forearm is extended and supinated there is always formation of an angle between long axis of arm and long axis of forearm that is termed as carrying angle which is approximately 163 degree in adults which opens literally the same angle disappears during pronation or flexion of the elbow say this now in non-articular areas as you know there are three fossas and two epicondyles so let's first see the radial fossa which is situated just above to capitulum and as it lodges anterior margin of head of radius let me join both these together the name given to it is radial fossa so when we join both these together like this see this when we do flexion just the anterior margin of head of radius will be lodging inside radial fossa say this Now there is another fossa medial to it. just above to trochlea this is termed as coronoid fossa as it is lodging anterior margin of coronoid process of ulna see this is how they are joined together and as i mentioned as it is lodging anterior margin of coronoid process of ulna during full flexion the name given to it as coronoid fossa say this during flexion the anterior margin of coronoid process is lodging inside okay so this is how the articulation will take place now posterior to it there is another depression which is termed as olecranon fossa similarly it is lodging olecranon process of the ulna during extended elbow see this when we do extension okay anterior margin of the olecranon process will be lodging inside the olecranon fossa humerus.
See this and during flexion the coronoid process will be lodging in coronoid fossa during extension the olecranon process will be lodging in the olecranon fossa. Now remaining non-articular areas are medial and lateral epicondyles. Let's just see first medial epicondyle. So this is a blunt bony projection.
directed medially and slightly backward see this this is medial epicondyle which is larger and more prominent as compared to the lateral epicondyle the tip of medial epicondyle provides attachment to anterior and posterior bands of ulnar collateral ligament now ulnar collateral ligament and radial collateral ligament are two strong collateral ligaments of elbow joint Anteroinferior aspect of medial epicondyle bears an impression for common origin of superficial flexors of the forearm. This is also termed as common flexor origin whereas posteriorly the medial epicondyle bears a groove which lodges ulnar nerve. Now at this place ulnar nerve can be rolled can be compressed and that leads to a characteristic tingling sensations.
Now lateral epicondyle which is comparatively less prominent projection and which is directed laterally and slightly forward. Its tip provides attachment to radial collateral ligament of elbow joint. Similar like medial epicondyle, entrolateral aspect of lateral epicondyle bears an impression which provides common origin of extensor muscles of forearm, superficial extensor muscle of forearm. which is also termed as common extensor origin the posterior aspect of lateral epicondyle provides origin to anconius muscle now to understand attachment of capsular ligament of elbow joint we have to draw a continuous line in front which should include capitulum, trochlea and these two fossa radial and coronary fossa like this we have to exclude both the epicondyles Similarly, posteriorly, the line of attachment will be including posterior aspect of trochlea and olecranon fossa. Again, both the epicondyles are excluded.
So this is regarding general features and attachments on the humerus. Hope you have understood well. Thanks for watching.