Hello students, welcome to osteology classes of upper limb. The first topic under osteology of upper limb is the clavicle. So the clavicle is here in this picture which is the superior view of right clavicle. It is the only long bone which is present horizontally in our human body.
and it is subcutaneous throughout so it is also called as collar bone or beauty bone it is the first bone to start ossifying which ossifies in membrane the ossification begins during fifth and sixth week of intrauterine life it is the only long bone which has two primary centers usually all the long bones in our body the shaft has only single primary center but for the clavicle there are two primary centers of ossification. It is generally said that to have no medullary cavity. So it is a controversial thing. Some say it is having medullary cavity and some anatomists say it is not having any medullary cavity.
It is occasionally pierced by nerve called as middle supraclavicular nerves which are subcutaneous nerves getting origin in the posterior triangle of the neck. So starting with the side determination of the clavicle which is right which is left. So see for the medial end of the clavicle. So the medial end here it is.
This is the medial end of the clavicle which is round or quadrangular in shape. It articulates medially with the sternum to form sternoclavicular joint. So this is the medial end of clavicle.
Lateral end is flat. And it articulates with the acromion process to form acromioclavicular joint. So here is the lateral end.
And superior surface of the clavicle is quite smooth. And inferior surface it is identified by rough impressions. So one is for the subclavian groove.
which we see on the inferior surface. It is in the middle of the shaft. So here is the subclavian groove which is present inferiorly and subclavian groove lodges subclavian vessels means subclavian artery and vein and we can see conoid, tubercle and trapezoid ridges present laterally on the inferior surface. The rough portion on the lateral side on the inferior aspect is the Conoid tubercle and trapezoid ridge.
Both gives the rough impression on the inferior surface on the lateral side of the clavicle. And shaft of the clavicle. So observe now the shaft of the clavicle.
Medial two thirds of the clavicle is convex. So if you see the anteriorly. So here is the anterior.
And this is the posterior. So this is the convexity of the anterior side. So medial two thirds of the clavicle is convex anteriorly. So what we are having here is the right clavicle. So this is the superior surface of right clavicle.
Okay, let's talk about the muscle attachments. We know medial two-thirds anterior surface is convex and provides attachment to the clavicular head of pectoralis major. So, medial two-thirds anterior surface provides attachment to the clavicular head of pectoralis major, which is a chest muscle.
and it has got the clavicular head and sternal head. So the clavicular head of pectoralis major gets origin from the medial two-thirds. Superior surface gives origin to the sternocleidomastoid on medially.
So medial two-thirds superior surface gives origin here to the sternocleidomastoid. Sterno because it is getting origin from sternum also. clido means from the clavicle and inserts into the mastoid process So, medial two-thirds anteriorly it gives origin to clavicular head of pectoralis major and superiorly sternocleidomastoid muscle. Inferior surface, medial two-thirds it is costoclavicular ligament.
Medially, it gives attachment to a ligament called as costoclavicular ligament. So, here is the costo means the ribs. Costoclavicular and middle part of the inferior surface gives insertion to subclavius muscle.
So the middle part we have seen the subclavian groove. So this part it gives insertion to subclavius muscle. And lateral one third. Lateral 1 3rd, first we will see on the superior aspect.
Lateral 1 3rd anterior border gives attachment to anterior fibers of deltoid. So, it provides origin to anterior fibers of deltoid and posterior border of lateral 1 3rd and also the superior surface. It provides attachment to the upper fibers of trapezius. So the upper fibers of the trapezius gets inserted on the posterior and as well as from the superior surface of the lateral one third of the clavicle.
Trapezius is a muscle which is present on the neck posteriorly. Superficial muscle it is. And inferior surface exhibits trapezoid ridge and conoid ridge which gives attachment to a ligament called coracoclavicular ligament.
So, here is the inferior surface where we already discussed about trapezoid, ridge and conar tubercle which provides attachment to a ligament called as coracoclavicular ligament. Inferiorly, the trapezoid and the conoid tubercle provides attachment to coraco-clavicular ligament means it is the ligament between the coracoid process of the scapula and clavicular it is between the lateral end of the clavicle so it is called as coraco-clavicular ligament. So these are the attachments important attachments of the clavicle Let's talk about ossification of the clavicle because we said it is the first bone to start ossifying in the body and there are two primary centers for the clavicle which appear in the medial and the lateral part of the shaft of the clavicle. So the primary centers usually appear during fifth to sixth weeks of intrauterine life and the time of fusion or by 45th day of intrauterine life. So both the centers diffuse by 45th day of intrauterine life.
And secondary center is for the sternal end that is for the medial end, sternal end it appears and it appears usually during 19 to 20 year after birth and it fuses with the shaft by 25th year. Primary centers fuses by 45th day. And secondary center for the acromial end, that is for the lateral end, it appears occasionally.
It is not always present. Suppose if it is present, it appears during 20th year. So, 20th year for the acromial end and it fuses immediately as soon as it appears.
So this is about the ossification of the clavicle. We will talk about some important clinical aspects of the clavicle. So fracture of the clavicle usually occurs in the middle third that is lateral one third and middle two thirds junction. So here this is the site of fracture at the junction of medial two thirds and lateral one third and it results in the upward displacement of the proximal.
fragment due to the pull. So the proximal fragment will be the medial side. So it will be displaced usually upwards because of the pull of the sternocleidomastoid muscle which is attached from above and downward displacement of the distal fragment is due to the pull of deltoid muscle due to gravity because laterally we know anterior fibers of deltoid is attached. So this completes about the osteology of clavicle.