Back Lecture 1 : Muscles Flashcards
What does the back provide?
The Back provides musculoskeletal axis of
support for the trunk
What do the bony elements of the back consist of?
The Bony elements consist mainly of vertebrae
What does the back contain?
The Back contains the spinal cord and proximal
parts of the spinal nerves
List the functions of the back.
The back :
o supports the body’s weight
o transmits forces through the pelvis
to the lower limbs
o carries and positions the head
o braces and helps maneuver upper
limbs
The vertebral column consists of :
33 vertebrae
The 33 vertebrae consist of :
▪ 7 cervical ▪ 12 thoracic ▪ 5 lumbar ▪ 5 sacral ▪ 3-4 coccygeal vertebrae
What does the sacral vertebrae fuse into?
The Sacral vertebrae fuse into a single bony
element, the sacrum
What do the coccygeal vertebrae vary in? What do they often fuse into?
Coccygeal vertebrae vary in number
from three to four, and often fuse into
a single coccyx
What groups do the muscles of the back consist of?
Muscles of the back consist of extrinsic and intrinsic groups
What does each group of muscles do?
- Extrinsic muscles - move the upper limbs and ribs
* Intrinsic muscles - maintain posture and move vertebral column
The movements of the muscles include :
Movements include flexion (anterior bending), extension, lateral flexion, and rotation
What are the extrinsic muscles involved in? What are they innervated by?
EXTRINSIC MUSCLES: involved in
movement of the Upper Limb (UL)
and thoracic wall and are innervated
by the anterior rami of spinal nerves or cranial nerve XI(trapezius).
What is the superficial group(of the extrinsic muscles) related to and involved in?
The Superficial group is related to and involved in the movement of the upper limb
What is the intermediate group(of the extrinsic muscles) related to and what does it serve as?
Intermediate group - is related to the
thoracic wall and serve as a
respiratory function.
Describe the position of the intrinsic muscles.
INTRINSIC MUSCLES: are deep in
position
What are intrinsic muscles innervated by?
The intrinsic muscles are innervated by the posterior rami
Name the superficial muscles of the back.
- Latissimus dorsi
- Levator scapulae
- Rhomboid major
- Rhomboid minor
- Trapezius
What are the superficial muscles of the back generally involved in?
These muscles are generally involved in movements of the shoulder
Describe each trapezius.
Each trapezius is flat and triangular with the base
situated along the vertebral column and the
apex pointing towards the tip of the shoulder
Origin of the trapezius :
- Superior nuchal line
- External occipital protuberance
- Ligamentum nuchae
- Spinous processes of C7 to T12
- Corresponding supraspinous ligaments
Insertion of the trapezius :
Insertion: Lateral 1/3 of clavicle;
acromion and spine of scapula
The action performed by the trapezius :
Assist in rotating scapula during abduction of humerus ❑upper fibers elevate scapula ❑middle fibers adduct scapula ❑lower fibers depress scapula
Which nerve is responsible for the innervation of the trapezius?
Accessory nerve (motor) [CNXI]
Describe the Latissimus Dorsi.
The Latissimus Dorsi is large, flat and triangular at lower
portion of back and ends in tendon that
attaches to the humerus.
Origin of the Latissimus Dorsi :
- Spinous processes of T7 to T12
- Posterior layer of lumbar fascia
- Outer lip of iliac crest
- Ribs (lower 4 – rib 8-12)
- Inferior angle of the scapula
Insertion of the Latissimus Dorsi :
Floor of the intertubercular sulcus
of the humerus
The action performed by the Latissimus Dorsi :
Extends, adducts, medially
rotates humerus
Which nerve is responsible for the innervation of the Latissimus Dorsi?
Thoracodorsal nerve (motor)
Describe the Levator scapulae.
The Levator scapulae is a slender muscle
Origin of the Levator scapulae :
Origin:
• Transverse processes of C1 &C2
• Posterior tubercles of the transverse
processes of C3 & C4
Insertion of the Levator scapulae :
Superior angle and upper part of
medial border of the scapula
The action performed by the Levator scapulae :
Elevates scapula
Which structures are responsible for the innervation of the Levator scapulae?
Innervation: dorsal scapular nerve (C5) and
C3-C4 anterior rami (motor)
Describe the Rhomboid Minor and state what it arises.
Rhomboid minor - small,
cylindrical and arises from
ligamentum nuchae, spinous
processes of C7-T1
Origin of the Rhomboid Major :
T2 to T5 spinous
processes and supraspinous ligaments
Insertion of the Rhomboid Minor :
•Rhomboid minor - Medial scapula
border
Insertion of the Rhomboid Major :
•Rhomboid major - Medial scapula
border below rhomboid minor
The action performed by the Rhomboid major and minor :
Work together to retract the
scapula to the vertebral column
Which nerve is responsible for the innervation of the Rhomboid major and minor?
Dorsal scapular nerve
Name the intermediate muscles.
- Serratus Posterior Superior
* Serratus Posterior Inferior
What is the Serratus Posterior Superior?
❑ Two flat muscular sheets that lie in the superior and inferior aspects of the back
Where do the fibres from the Serratus posterior superior and inferior?
❑The fibres from Serratus posterior superior and inferior pass outwards from the
vertebral column to attach to the ribs. Referred to as the respiratory group
Origin of the Serratus posterior superior :
• Deep to the rhomboid muscles
• Nuchal ligament & spinous process of
C7 to T3
• Fibres descend from vertebral column
Insertion of the Serratus posterior superior :
Upper borders of the 2-5 ribs
Action performed by the Serratus posterior superior :
Elevates ribs 2-5 and aids deep
Inspiration
Which structure is responsible for the innervation of the Serratus posterior superior?
Anterior rami of T2-T5
Origin of the Serratus posterior inferior :
- Deep to Lattisimus dorsi
- Spinous processes of T11 to L2
- Fibres ascend from vertebral column
Insertion of the Serratus posterior inferior :
Inferior borders of the 9-12 ribs
Action performed by the Serratus posterior inferior :
Depresses ribs 9-12 & aid in expiration
Which structure is responsible for the innervation of the Serratus posterior inferior?
Anterior rami of T9-T12
What is the action of a muscle based on?
Action of a muscle is based on its origin and
insertion – contraction of the muscle will
pull towards the origin point
What do deep muscles include?
➢ Extensors and rotators of the head and neck – SPINOTRANSVERSALES: splenius capitus and
splenius cervicis
➢ Extensors and rotators of the vertebral column - erector spinae and transversospinales
➢ Short segmental muscles – interspinales and intertransversarii
Which structures are responsible for the innervation of the deep muscles?
Posterior rami of spinal nerves
What are the deep muscles of the back responsible for?
Deep muscles of the back are responsible for keeping the body in the erect
position
The erector spinae is the…
strongest muscles in the back and take on most of the work.
What are the spinotransversales?
The spinotransversales are 2 muscles that run from the spinous processes and
ligamentum nuchae vertically upwards and laterally
Actions performed the Spinotransversales -Splenius capitus and splenius cervicus :
o Together: Extend neck
o Individually: rotate head to one side
Origin of the Splenius capitus :
Lower ½ Ligmentum Nuchae & spinous
processes of C7 to T3/4
Insertion of the Splenius capitus :
Mastoid process and
occipital bone of the skull
The structures responsible for the innervation of the Splenius capitus :
Posterior primary rami of middle cervical nerves (C3-C4)
Origin of the Splenius cervicus :
Spinous process of T3 to T6
Insertion of the Splenius cervicus :
Transverse process of C1-C3
The structures responsible for the innervation of the Splenius cervicus :
Posterior rami of lower cervical nerves
What are the Erector Spinae covered by? What are they inferior to?
The Erector Spinae are covered by thoracolumbar fascia and serratus post and are inferior to the rhomboids and splenius muscles
Where is the iliocostalis located?
❑Iliocostalis is the Outermost/laterally placed column of muscles
The Longissimus is the…
Middle/intermediate column
Describe the Longissimus.
The longissimus is the Largest of the subdivisions of erector spinae
The Spinalis is the…
Most medial column
Describe the Spinalis.
The spinalis is the Smallest of the subdivision
ERECTOR SPINAE : Where is the iliocostalis muscle located?
The iliocostalis muscle is located laterally within the
erector spinae
What is the iliocostalis muscle associated with?
It is associated with the ribs, and can be divided into three
parts – lumborum, thoracis, and cervicis
What does the Spinalis interconnects?
The spinalis interconnects the spinous processes of adjacent vertebrae.
Action performed by the Erector Spinae :
PRIMARY EXTENSORS of the vertebral column and head.
Acting unilaterally: they bend the vertebral column laterally
ERECTOR SPINAE - Origin of the iliocostalis :
Common tendinous origin
Insertion of the iliocostalis :
- Costal angle of the ribs
* cervical transverse processes
The structures responsible for the innervation of the iliocostalis :
Posterior rami of the spinal nerves
Actions performed by the iliocostalis muscle :
o Acts unilaterally to laterally flex the vertebral column.
o Acts bilaterally to extend the vertebral column and head.
Erector Spinae :Where is the Longissimus situated?
The longissimus is situated between the iliocostalis and spinalis
The Longissimus is the…
largest of the three columns
The longissimus can be divided into three parts, namely :
thoracic,
cervicis and capitis.
Origin of the Longissimus :
Common tendinous origin
Insertion of the Longissimus :
❑to the lower ribs
❑transverse processes of C2–T12
❑mastoid process of the skull
Innervation of the Longissimus :
Posterior rami of the spinal nerves
Actions performed by the Longissimus :
o Acts unilaterally to laterally flex the vertebral
column.
o Acts bilaterally to extend the vertebral column
and head.
Where are the transversospinales located?
The transversospinales are deep intrinsic muscles are located underneath the erector spinae.
The transversospinales are a…
Group of short muscles, run obliquely upward and medially from transverse
process to spinous process.
There are three major muscles in the transversospinales group, namely :
the semispinalis, multifidus and
rotatores.
What is the Semispinalis?
The semispinalis is the most superficial of the deep intrinsic muscles
Origin of the Semispinalis :
Transverse processes of C4-T10
Insertion of the Semispinalis :
❑Spinous processes of C2-T4
❑Occipital bone of the skull
The structures responsible for the innervation of the Semispinalis :
Posterior rami of the spinal nerves
Actions performed by the Semispinalis :
Extends and contralaterally rotates the
head and vertebral column.
Where is the multifidus situated? Where is it best developed?
❑ Beneath semispinalis muscle. Best developed in the
lumbar area.
Origin of the multifidus :
Sacrum, posterior iliac spine, common
tendinous origin of the erector spinae, mamillary
processes of lumbar vertebrae, transverse processes of
T1-T3 and articular processes of C4-C7.
Insertion of the multifidus :
Spinous processes of the vertebrae
The structures responsible for the innervation of the multifidus :
Posterior rami of the spinal nerves
The action performed by the multifidus :
Stabilises the vertebral column
The Rotatores are the…
Most prominent in the thoracic region
Origin of the Rotatores :
Vertebral transverse processes
Insertion of the Rotatores :
Lamina and spinous processes of the
immediately superior vertebrae
The structures responsible for the innervation of the Rotatores :
Posterior rami of the spinal nerves
The action performed by the Rotatores :
Stablises the vertebral column & has a
proprioceptive function
What are the 2 groups of segmental muscles innervated by?
TWO GROUPS OF SEGMENTAL
MUSCLES - INNERVATED BY THE
POSTERIOR RAMI
Origin of the Levatores Costarum :
Transverse processes of vertebra C7 - T11
Insertion of the Levatores Costarum :
The rib below the vertebra of origin.
The action performed by the Levatores Costarum :
Contraction elevates the ribs
Where do the Interspinales pass?
Interspinales pass beween adjacent spinous
processes.
Where do the Intertransversarius pass?
Intertransversarius pass between adjacent
transverse processes.
The action performed by the Interspinales and the Intertransversarius :
They stabilize the vertebrae during
movements of the vertebral column.
Where does muscle strain occur?
Low back pain/muscle strain or ruptures
can occur in the back just like they can
anywhere else in the body.
What is a muscle strain in the back usually caused by?
A muscle strain
(or tear) in the back is usually caused by a
sudden movement or trying to lift
something that is too heavy.
Why is low back pain a long time coming?
The low back pain however is often a long
time coming on as the muscles in the back
gradually tighten up due to bad posture
and overuse.
Why do the muscles of the back become weak?
These muscles go into spasm and do not
get enough blood through them resulting
in weakness.
