Muscles of the Back

Anatomy  Team  434  

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 OBJECTIVES  
●  Dis&nguish  between  the  different  groups  of  back  muscles.  
●  Compare  between  groups  of  back  muscles  as  regard  their  nerve  supply  
and  ac&on.  
●  List  the  back  muscles  of  each  group.  
●  Describe  the  a@achments  of  each  muscle  of  the  superficial  group,  as  well  
as,  its  nerve  supply  and  ac&on.  
●  Describe  the  triangles  of  back  and  their  clinical  significance.  
Study Strategy * Don’t worry it’s an easy lecture.

First take an overview in the mind map.

Second read every slide carefully, after that go through the tables to
organize and differentiate between the information.

Third Take a final overview in the mind map.

Important note:
Finally watch videos and links.
*Don’t go directly to table,
you should read the
slides.
Mind Map
MUSCLES of the BACK They are organized into 3 groups:

Deep group:
- attached to & involved in the movement of vertebral column &
Intermediate group:
head
- attached to ribs & serve respiratory functions.
- they are Intrinsic muscles(A group of muscles located within
or situated deeper in a structure)
- Develop in the back and are supplied by posterior rami of
spinal nerves. Superficial group:
- attached to & involved in the movements of upper
limb.

both superficial and intermediate

groups are:
- Extrinsic muscles(A group of muscles lying
superficially on a structure,)

- Not be developed in the back but will later

migrate to the back after development and are
supplied by anterior rami of spinal nerves.
DEEP GROUP OF BACK MUSCLES (intrinsic muscles)

●  They extend from sacrum to skull.(remember:

similar to the anterior and posterior longitudinal
ligaments )

●  since both origin and insertion are on the

vertebral column, ,their action(extension and
rotation) will also be on the vertebrae) .

●  They include extensors and rotators of head &

vertebral column

●  Their tone is responsible for maintenance of

normal curvature of vertebral column.

●  The largest muscle of this group is “erector

spinae” which is formed of 3 vertical columns:
(from lateral to medial: iliocostalis, longissimus & spinalis)

Nerve supply: ? ( posterior rami of spinal nerves)

INTERMEDIATE GROUP OF BACK MUSCLES

intermediate group are attached to the ribs. it include 2 muscles:

- Serratus posterior superior (rib elevator).
- Serratus posterior inferior (rib depressor).
origin:vertebral column insertion: rips

action: lead to movement of ribs and help in respiratory

function.(no movement for the back)

Nerve supply: anterior rami of thoracic spinal

nerves.

It is separated from the deep group by thoracolumbar fascia (made up of

fibrous tissue).
 SUPERFICIAL GROUP OF BACK MUSCLES
1)Muscles connecting vertebral column to scapula
(move scapula through shoulder girdle joints) and
include:
- Trapezius.
- .Levator scapulae.
- .Rhomboid minor.
- .Rhomboid major.

Superficial muscles

Includes two
sets of 2)Muscle connecting vertebral column to humerus (move
muscles humerus through shoulder joint) and include:
- Latissimus dorsi.
Muscles of the back Back Muscles in a Nutshell - Anatomy Tutorial

Group Attachment Develop Muscles Nerve Other features

ment

Deep vertebral   intrinsic   erector  spinae  which   posterior  rami     -­‐extend  from  sacrum  to  skull    
column  &   is  formed  of  3   -­‐they  include  extensors  rotators  
head   ver9cal  column   of  head  and  vertebral  column    
(from  lateral  to   -­‐their  tone  is  responsible  for  
medial  )  :  iliocostalis  ,   maintenance  of  normal  
longissimus  &   curvature  of  vertebral  column    
spinalis  

Intermediate ribs   extrinsic   1-­‐serratus  posterior   anterior  rami   separated  from  deep  group  by  
superior     in  thoracic   thoracolumbar  fascia  
2-­‐  serratus  posterior   spinal  nerve    
inferior    

Superficial upper  limbs   extrinsic   1-­‐  trapezius     anterior  rami   will  be  discussed  later    
2-­‐  levator  scapulae   (except  
3-­‐  rhomboid  minor   trapezius  it’s  
4-­‐  rhomboid  major     supplied  by  the  
5-­‐  la9ssimus  dorsi   11th  cranial  
nerve)    
TRAPEZIUS

Origin: Spines of cervical and thoracic vertebrae Action: rotation of scapula during
abduction of humerus above
Insertion: lateral 1/3 of clavicle + acromion and horizontal.(above 90 degree )
spine of scapula.(if you pull the insertion end of the
muscle to its origin, 90% the muscle's action will be
triggered)

Nerve supply: Spinal part of accessory nerve (11th

cranial nerve)

it is made up of 3 types of fiber:

- Upper fibers: elevate scapula.
- Middle fibers: retract scapula
- Lower fibers: depress scapula.
(both the upper and lower fibers will help in the abduction of
humerus)
LEVATOR SCAPULAE,
LATISSIMUS DORSI
RHOMBOID MINOR & MAJOR
❖  Origin: ❖  Origin: spines
- Levator scapulae: cervical transverse processes of thoracic
- .Rhomboid minor & major: thoracic spines vertebrae.
❖  Insertion(for both): medial border of scapula. ❖  Insertion:
❖  Actions: bicipital groove
- .Levator scapulae: elevates scapula. of humerus.
- .Rhomboid minor & major: retract scapula. ❖  Nerve supply:
❖  Nerve supply: dorsal scapular nerve.
thoracodorsal
nerve.
❖  Actions:
extension,
adduction &
medial rotation
of humerus
(arm, shoulder
joint).
Muscles of the Back (Superficial Group)
MUSCULAR TRIANGLES OF BACK

Auscultatory Triangle:
Boundaries(very important): latissimus dorsi,
trapezius, and medial border of scapula.
Site: where breath sounds are most easily
heard with a stethoscope.

Lumbar Triangle: (Or triangle of Petit)

Boundaries : latissimus dorsi, posterior border
of external oblique muscle of the abdomen, and
iliac crest.
Site of an abdominal hernia or where pus may
emerge from the abdominal wall (in the case of
musculoskeletal TB of the spine due to bacterial infection →
pus formation → pus will accumulate in the lumbar triangle
or triangle of petit)
Muscular Triangles of Back
 MCQ’s
1- Latissimus dorsi origin is : 5- group of muscle developed in the back :
A) spines of thoracic vertebrae A) intermediate and superficial
B) spines of cervical vertebrae B) superficial group of back muscle
C) spines of sacral vertebrae C) deep group of back muscle
D) spines of lumbar vertebrae D) intermediate group of back muscle

2- the muscle of upper limb that is supplied by the spinal 6- the muscle group that involves in respiratory
part of accessory (11th cranial) nerve is: function is
A) trapezius A) deep and superficial group of back muscle
B) levator scapulae B) superficial group of back muscle
C) rhomboid minor C) deep group of back muscle
D) rhomboid major D) intermediate group of back muscle
Answe
3- Site where pus may emerge from the abdominal wall : 7- one of the following is an action of latissimus dorsi rs:
A) auscultatory triangle muscle 1) A
B) erector spinae A) flexion 2) A
C) lumbar triangle B) abduction 3) C
D)shoulder girdle joint C) medial rotation 4) B
5) C
D) lateral rotation 6) D
4- Site where breath sound are most easily heard with 7) C
stethoscope : 8- Action of levator scapula is : 8) C
A) lumbar triangle A) exensor vertebral
B) auscultatory triangle B) elevate clavicle
C) thoracolumbar C) elevate scapula
D) Latissimus dorsi D) depress scapula
Recommended Websites
MedicalMnemonics.com