When talking around muscular attachments, it’s important to know and also understand the difference between the origin and also insertion. They are not interchangeable and also have totally different meanings, though you have the right to say muscular attachment or attachments site and also be talking about either the beginning or the insertion.

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What’s the difference?When a muscle contracts, the beginning pulls the insertion closer. Always! muscles pull. The origin is the fixed suggest that doesn’t move during contraction, when the insertion go move. Her bones room the levers and also your muscles space the pulley. Basically, we room all super complicated puppets on strings. To discover this further, let’s take it a look in ~ the rhomboids.


Rhomboids Minor and Major

Firstly, there room two rhomboids and also they’re both deep come the multidirectional fibers of the trapezius. Rhomboid minor sits on height of, or premium to, its larger counterpart rhomboid major. Boy originates ~ above the spinous processes of C7 and also T1 while significant originates top top the spinous procedures of T2-T5. You have the right to pretty conveniently feel because that T1 on yourself, it’s just at the base of the posterior neck and it bump out a little bit posteriorly. The transverse processes stick out to the sides while the spinous processes, i beg your pardon we are talking about here, rod out and a bit downward posteriorly. They remind me that a stegosaurus. It’s native these tiny posterior projections that both rhomboids originate.

Back to rhomboid minor, the inserts on the upper section of the medial border the the scapula, across from the spine the the scapula. The insertion for levator scapula is best there too and also is easily palpable on you yourself or someone else. Rhomboid major inserts on the medial border the the scapula together well, basically between the spine that the scapula and the inferior angle of the scapula. The actions of the rhomboids space to retract or adduct the scapula, elevate the scapula and also downwardly rotate the scapula.

WHOA, WAIT.How go a muscle that elevates the scapula downwardly turn it together well? If you look at the direction the fibers run, they’re on a little bit of a downward edge going native the spine to the scapula. Due to the fact that of this, as soon as the muscles contract, they have the pulling capacity to attract the shoulder knives closer together. Bottom rotation deserve to be a tricky one since the scapula is the only bone in the human body to perform it, yet we’re referring an ext specifically come the activity of the acromion, i beg your pardon is the level bony process at the lateral finish of the posterior scapula. When the rhomboids contract, they have the ability to tilt the acromion downward. That a slight action but it’s over there nonetheless. Ultimately the rhomboids can also elevate the scapula together a whole. Every time the muscle contracts (concentrically, the is, however that’s an additional post for one more day), the beginning says ‘come come me’, and so the insertion does. This is true for all the muscles in the body.

When examining anatomy, learn to look very closely at the direction that the muscle fibers, and determine which end is the origin and also which finish is the insertion. That info will take it you a long method in figuring out what action a muscle can do.

ANOTHER EXAMPLELet’s look at a neck muscle- the sternocleidomastoid, or SCM. It has actually two top which means it originates in 2 spots: the top of the manubrium (sternum) and the medial third of the clavicle. Its insertion is increase behind the ear on the mastoid procedure and the outer portion of the occiput. Once both the left and also right ideal SCM contract together, the origin (which is down on the clavicle and sternum) traction the insertion toward it to create neck flexion and also assist to lift the rib cage come make more space because that inhalation.

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My expect is the this provides sense but if you nothing understand and also would choose to, you re welcome send me an email and I’ll rest it down even more! If you teaching and get confused about what’s the origin and also what’s the insertion, you can simply to speak attachment. However do trust yourself! If you take it a minute to think around how the body moves and also works, and also you recognize the beginning is fixed and also the insertion moves, you have the right to likely number it out for yourself.