Origin , insertion, action and clinical anatomy of pectrolis major , serratus anterior, deltoid muscles

2. Made by Himanshu Arora.

3.  It is the largest muscle of the pectoral
region.
 It is thin fan shaped like muscle.
 It has two heads.
1) Clavicle head
2) Sternocoastal head

4. Origin of pectoralis major
 Clavicle head is
originated by the anterior
aspect of medial half of
clavicle.
 Sternocostal head is
originated by the anterior
surface of sternum of
laterally upto 6th coastal
cartilage.

5. It is inserted
lateral side of
bicipital groove
of Humerus and
anterior side of
the deltoid
tuberosity

6. Nerve supply
Nerve supply is lateral pectoral
nerve(C5,C6)
Medial pectoral nerve (C8,T1)
Action
The clavicular head flexes the arm
Sternocostal head adducts and medially
rotates the arm.

7. Clinical testing
 On lifting a heavy rod, the
clavicular head becomes
prominent and when one
attempts to depress the rod,
the sternocostal head become
prominent.
Clinical correlation
 Occasionally the part of the
pectoralis major, usually the
sternocostal part is absent at
birth this cause weakness in
adduction and medially
rotation of the arm.

8. The deltoid is a three in
one muscle.
It is thick, powerful and
curved triangular muscle.
It covers the shoulder.
The deltoid is shaped like
the inverted Greek letter
Delta(D), Hence its name
deltoid.

9. Origin of Deltoid
It has three parts:
1) Clavicular part- It is originated
by the lateral one third of the
clavicle.
2) Acromion part- It is originated
by the lateral border of the
Acromion process of the
scapula.
3) Spinous part- It is originated
by the lower lip of spine of
scapula.

10. Insertion of Deltoid
Deltoid tuberosity of humerus
Nerve supply
It is supplied by the Axillary nerve
(C5,C6)

11. Action of Deltoid
1) Flexion and medial rotation by the
anterior fibers
2) Abduction (15-90 degree) of the
arm by the medial fibers
3) Extension and medial rotation of
the arm by the posterior fiber

12. Clinical correlation of
Deltoid
 Site of intramuscular injection in
deltoid: The intramuscular are
commonly give in the lower half of
the deltoid to avoid injury to the
axillary nerve which winds around
the surgical neck of the humerus.

13. The Serratus anterior
is a broad sheet of
muscle that close the
side wall of thorax.
 It is not a muscle of
pectoral region. But
for convenience, it is
described with the
pectoral region.

14. Origin of serratus anterior
It is arise from eight
digitations from
upper 8 ribs. First
digitations from 1st
and 2nd ribs, where
as all other
digitations arise
from their
corresponding ribs.

15. Insertion of serratus anterior
It is inserted in costal surface
of the scapula along its
medial border.
The first 2 digitations are
inserted into the superior
angle.
Next two digitations into the
medial border
The lower 4 or 5 digitations
into the inferior angle of
the scapula.

16. Nerve supply
 It is supplied by long thoracic nerve
(C5,C6,C7)
Action
1) Scapular abduction
2) Upward rotation of scapula
3) Protraction and stabilization of scapula
4) Punching action (Boxing)

17. Clinical correlation
Paralysis of serratus anterior: The paralysis of
serratus anterior muscle following an injury to Long
thoracic nerve by stab injury or during removal of
the breast tumor leads to the following effects:
1) Protraction of scapula weakened
2) Inferior angle and medial border of scapula becomes
unduly prominent particularly when patient pushes
his hands against the wall, producing a clinical
condition called winging of scapula.