Download MUSCLES OF THE SHOULDER

MUSCLES OF THE SHOULDER
MUSCLES CROSSING THE SHOULDER JOINT
6 INTRINSIC SHOULDER MUSCLES:
DELTOID
INFRASINATUS
SUBSCAPULARIS
TERES MAJOR
SUPRASPINATUS
TERES MINOR
1 ANTERIOR THORAX: PECTORALIS MAJOR
1 POSTERIOR THORAX: LATISSIMUS DORSI
1 SMALL ANTERIOR ARM: CORACOBRACHIALIS
PECTORALIS MAJOR
LARGE FAN SHAPED
MUSCLE
(CONVERGENT)
TWO HEADS,
CLAVICULAR AND
STERNAL
FORMS ANTERIOR
WALL OF THE AXILLA
POWERFUL
ADDUCTOR AND
MEDIAL ROTATOR
DELTOID
PECTORALIS
MAJOR
SERRATUS ANTERIOR
LATISSIMUS
DORSI
(WIDEST OF THE
BACK)
COVERS LOWER
HALF OF BACK
INSERTS INTO
HUMERUS
EXTENDS,
ADDUCTS AND
ROTATES THE
HUMERUS
MEDIALLY
FORMS
POSTERIOR
AXILLARY FOLD
TRIANGLE OF
AUSCULATION (TO
LISTEN)
LATERAL BORDER SCAPULA
MEDIAL
BORDER TRAPEZIUS
LOWER BORDER
- LATISSIMUS
DORSI
DELTOID
ROUNDED PART OF
THE SHOULDER,
DELTA SHAPED !
3-PARTS ACT
TOGETHER ABDUCT
ARM
ANTERIOR PART
FLEXION AND MEDIAL
ROTATION
POSTERIOR PART
EXTENSION AND
LATERAL ROTATION
INTERMUSCULAR
INJECTIONS
TRAPEZIUS
DELTOID
LATISSIMUS
DORSI
SUBSCAPULARIS
FILLS IN
SUBSCAPULAR
FOSSA,
UNDERNEATH THE
SCAPULA (DEEP)
INSERTS ONTO
LESSER TUBERCLE
PRIMARY MEDIAL
ROTATER OF ARM
ROATOR CUFF
MUSCLE, HOLD
HEAD OF HUMERUS
IN GLENOID
CAVITY
PECTORALIS MINOR
SUBCLAVIUS
SUBSCAPULARIS
SERRATUS ANTERIOR
DELTOID
PECTORALIS
MINOR
SERRATUS ANTERIOR
?
PECTORALIS
MAJOR
SUPRASPINATUS
SUPRASPINOUS FOSSA
MUST REFLECT THE
TRAPEZIUS AND
DELTOID TO SEE THIS
MUSCLE
INITIATION OF ARM
ABDUCTION, AFTER 15º
DELTOID BECOMES
EFFECTIVE
ROTATOR CUFF
INSERTS ON GREATER
TUBERCLE
INFRASPINATUS
OCCUPIES
INFRASPINOUS FOSSA
REFLECT DELTOID
AND TRAPEZIUS TO
SEE
POWERFUL LATERAL
ROTATOR
ROTATOR CUFF
MUSCLE
INSERTS INTO
GREATER TUBERCLE
OF HUMERUS
TERES MINOR
THIN BAND OFTEN
NOT DISTINCT FROM
THE LOWER EDGE
OF THE
INFRAPINATUS
WORKS WITH
INFRASPNATUS TO
LATERALLY ROTATE
ARM
ROTATOR CUFF
MUSCLE
INSERTS INTO
GREATER
TUBERCLE OF
HUMERUS
ROTATOR CUFF MUSCLES
NOTE THAT 3 MUSCLES OF THE ROTATOR CUFF
INSERT ON THE GREATER TUBERCLE OF THE
HUMERUS:
SUPRASPINATUS
INFRSPINATUS
THESE THREE MUSCLES SIT
TERES MINOR
ON THE TUBERCLE
THE 4TH MUSCLE
SUBSCAPULARIS INSERTS
ONTO THE LESSER TUBERCLE
TIS
S
ROTATOR CUFF MUSCLES - ACTIONS
SUPRAPINATUS - INITIATES ABDUCTION
INFRASPINATUS - LATERAL ROTATOR
TERES MINOR - LATERAL ROTATOR
SUBSCAPULARIS - MEDIAL ROTATOR
ALL - TONIC CONTRACTION TO HOLD HUMERAL
HEAD
SUPRASPINATUS MOST COMMONLY INJURED
TERES MAJOR
THICK CYLINDER
SHAPED MUSCLE,
(TERES – ROUND)
HELPS FORM
POSTERIOR
AXILLARY FOLD
WORKS WITH
LATISSIMUS DORSI
HOLDS HEAD OF
HUMERUS IN
PLACE AGAINST
PULL OF DELTOID
THREE MUSCLES INSERT
INTO THE
INTERTUBERCULAR
SULCUS OR GROOVE OF
THE HUMERUS
ADDUCT
PECTORALIS
MAJOR
LATISSIMUS
DORSI
TERES
MAJOR
CORACOBRACHIALIS
SUPERIOR AND MEDIAL
PART OF THE ARM
HOW DOES IT GET ITS
NAME?
OFTEN FUSED
SUPERIORLY WITH THE
SHORT HEAD OF BICEPS
BRACHII
ANTERIOR VIEW
SUBSCAPULARIS
DELTOID
CORACOBRACHIALIS
ANTERIOR VIEW
Muscle Movement - How does it happen?
What makes a muscle contract when you want it to?
Think about moving - planning the movement: this is called intentional or
volitional movement.
This planning occurs in the cortex of the brain, but where?
A message is then sent to an other
group of neurons in the cortex of
the brain which will send the
specific movement message.
These are called upper motor neurons.
Were are they located?
Where will the nerve fibers from the upper motor neurons
end?
How is the place or area of the body where they end
determined? (think homunculus)
This message is sent down a group of nerve fibers (this is an Action
Potential - AP) which arise from a specific area of the homunculus.
What is the name for a group of nerve fibers in the central nervous
system?
What is the name of this specific group of fibers that delivers a message
about intentional movement?
If the movement is to be in the head or neck, were will the nerve fibers in
the tract end?
If the movement is to be in the body, where will the nerve fibers in the
tract end?
What is the name of the type of neurons
located in these areas that will
ultimately cause movement?
The nerve fibers from these lower motor neurons will exit the brain stem
or spinal cord sending an AP to the muscle fiber.
The nerve fibers end in a structure called the terminal boutons (axonal
terminal.
With what structure do the terminal
boutons synapse?
Now what happens?
The “Excitation - Contraction Coupling” which causes the muscle fibers
to slide past one another and shorten. (To be discussed later…..)
In response to the excitation - contraction coupling the muscle will
contract or shorten .
The muscle is attached at two points. What are these?
When the muscle shortens it will pull the more movable point toward the
more stable point or it will pull the _______ toward the ___________
which results in movement.
Can these points be reversed?
How would this happen?
What would happen if the neurons in the premotor cortex or primary
motor cortex (upper motor neurons) did not function?
What would happen if the nerve fibers in the tract from the cortex were
cut?
What would happen if the nerve cell bodies in the brain stem or spinal
cord (lower motor neurons) were injured?
What would happen if the nerve fibers which exit from the lower motor
neurons of the spinal cord or brain stem were cut?
How do these differ?
X indicates the upper motor neuron in
the primary motor cortex.
X
The red line is the pyramidal tract
(corticospinal tract).
* Indicates the lower motor neuron in
the spinal cord.
The blue line is the peripheral nerve, in
this case the musculocutaneous nerve.
*