Extrinsic muscles of the back – Anatomy Tutorial

Extrinsic muscles of the back – Anatomy Tutorial

Okay so this is a tutorial on the extrinsic
muscles of the back. The extrinsic muscles of the back are those muscles which are superficial
and are responsible for movements at the shoulder and upper limb. These are different to the
intrinsic muscles of the back which are deep, and which are responsible for controlling
posture and movement of the spine and head. So the extrinsic muscles of the back are the
trapezius, the latissimus dorsi, the rhomboid major and minor, and the levator scapulae.
So just working superficially to deep I’ll just show you these muscles. So I’ll start
with the trapezius, which is this muscle here which you probably all know – big trapezium
shaped muscle, which is why it’s called the trapezius. And it basically extends from the
external occipital protuberance here, all the way down to the lowest thoracic vertebra
T12 – the spine of T12. And laterally it inserts along the spine of the scapula and posteriorly
on the distal end of the clavicle, which you can’t quite see, but it inserts just at the
back of the clavicle here, and also on the acromion of the scapula. So this muscle is
responsible for elevating and depressing the scapula, and it can also retract the scapula.
It’s innervated by the axillary nerve, sorry, the accessory nerve, which is the eleventh
cranial nerve and it receives sensory innervation from the ventral rami of C3 and C4. All the
extrinsic muscles are innervated by the ventral rami, as opposed to the dorsal rami, because
these muscles insert onto the…insert onto the upper limbs, whereas the intrinsic muscles,
which are primarily innervated by the posterior rami, are deeper and are just responsible
for attaching to, and controlling the posture and movement of the spine. So that’s the trapezius,
this huge muscle here, just get rid of that. The next muscle is the latissimus dorsi, and
it’s called that because in Latin, “latissimus” means “the broadest”, and “dorsi” means “back”,
so it’s basically the “broadest muscle of the back”. So this muscle inserts into the
humerus in between the insertion points of the pec major and…what’s this one…the
teres major, and for that reason it’s often referred to as the “lady between two majors”,
so it inserts in the intertubercular groove of the humerus, in between the teres major
and the pectoralis major. So this huge muscle, the latissimus dorsi adducts the arm, extends,
and internally rotates the humerus. It’s innervated by spinal nerves C6, 7 and 8. So moving on,
just underneath the trapezius, which I’ve removed here, we now have, we can now see
the rhomboid muscles. So this is the rhomboid minor here…zoom in a bit closer…so the
rhomboid minor and the rhomboid major. So these just lie deep to the trapezius muscle,
and as you can see here they insert onto, or sorry, they originate on the spines of
the vertebra. So the rhomboid minor here originates on the spine of C7 and T1, and inserts onto
the medial border of the scapula. And the rhomboid major originates on the spinous processes
of T2 to T5 and inserts medially on the scapula. So these muscles basically keep the scapula
pressed against the thoracic wall and they can retract the scapula when the trapezius
is contracted. So they act as antagonists to the trapezius muscle. They are both innervated
by the dorsal scapula nerve, which comes of C3, spinal nerves C3 and C4. So these are
the rhomboids. The last extrinsic muscle of the back is the levator scapulae, or well,
collectively the levator scapulae. So I’ll just get rid of the rhomboids, so had a good
look at those, and underneath them you can see the levator scapulae. So it’s this muscle
here. And as you can tell by the name, this muscle elevates the scapula, so levator is
Latin I guess, for lifting, lifter, or something like that, so it elevates the scapula. So
we can see here, just at its origin, it’s covered by the sternocleidomastoid and the
splenius capitis. Okay so if we zoom in, you can see exactly where it originates on the
transverse process of the first vertebra, and then if we follow the path down, we can
see that it inserts on the superior angle of the scapula and the adjacent medial border.
So that’s the levator scapulae and it’s innervated by branches of C4 and C5, and it elevates
the scapula. So just to recap, the extrinsic muscles, you’ve got the trapezius, the latissimus
dorsi, the rhomboid major, the rhomboid minor, and the levator scapulae, so these two muscles

35 thoughts on “Extrinsic muscles of the back – Anatomy Tutorial

  1. @deigot Hi, thanks for the comment. You will be pleased to know that the software I use for these videos is available online for free. I use BioDigital Human and also Zygote Body and they are both great tools for learning anatomy. To record the videos I use Camtasia Studio. Good luck with the presentation!

  2. Im sure its bad posture cos i can barbell row 135lbs easy and im only 15, tbh i think its bad posture and it feels like a sort of burning sensation on my lower traps,but tbh it rarely happends now so i think its all good

  3. I just want to say thank you for these excellent videos, I have spent a great deal of time watching them preparing for an upcoming exam and bell ringer. Your explanations are very clear, and even though the model is not always perfect I can always follow what you are saying and look up any minor differences you point out in my text. These are the best anatomy videos I have seen on youtube other than actual dissections. Keep up the great work!

  4. just a quick question, are you a doctor or a teacher? because you know a lot of things and btw thank you for sharing i like your videos very much

  5. Appreciate this. My cousin's muscles grew really fast – as though he was using steroids. Funny. I've invariably struggled to build muscle mass. This man used the Muscle Building Bible (look for it)

    I'm going to test it.

  6. You have know idea how helpful your tutorials are.I am using them for my Anatomy class and I got an A in the class:))
    Thank you, thank you.

  7. i just want to confirm with u whether rhomboids are innervated by c5 nerve or c3 and c4 as u mentioned in the video… great video btw

  8. I was like "Nooo…!" when you said that the Trapezius is innervated by Axillary nerve, nice that you got that one sorted out quick

  9. Awesome video, it was a great help.

    Something to note is Rhomboid Major and Minor are innervated by C4 and C5 Spinal Nerves not C3 and C4

  10. Why are the rhomboids antagonists to the middle portion of the trapezius when they both act in scapular retraction? I thought they were synergists in this movement? time 5:05 in video. What is wrong with my thinking? Thank you for all these videos too!

  11. Thank you so much love r accent, so interesting and it is really difficult to get boring listening r tutorials…………………BIG THUMB

  12. Funny how everyones saying he has an accent when clearly americans are the ones with the accent :/

  13. Where are you from?

    The word trapezium, used to describe a geometric shape, has two contradictory meanings:

    (outside the US and Canada) – a quadrilateral with at least one pair of parallel sides, known in the US as a trapezoid.
    (in the US and Canada) – a quadrilateral with no parallel sides (a shape known elsewhere as a general irregular quadrilateral).

  14. I love all the videos, they are great with no errors. Short- Quick and Informative. BUT Why do you sound so lost and unsure in this one? Alot of mistakes and a lot of "uummss"

  15. in order to help me learn the form, I imagine myself a tiny insect flying in and out of the anatomical parts. Who else does this?

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