Download Pectoralis Major - University of Nottingham Surgical Society

Rachel Holmes

Explain the actions of the pectoral muscles and
investigate the roles of intercostal muscles in
respiration

Examine the neurovascular contents of the intercostal
space

Clinical relevance: Chest drains










Skin
Fascia (connective
tissue/fat)
Nerves
Vessels
Muscles
Cartilages
Bones
Protects organs
Allows for respiration
Supports upper limbs

Pectoralis major and minor
◦ Axioappendicular muscles
(connect upper arm-appendix to
thorax-axis

Pec major and deltoid form
deltopectoral groove in which
the cephalic vein runs
◦ More on this when you cover the
upper limb

Pec major forms the
anterior axillary fold
(axilla=armpit)

Pectoralis major
◦ Fan shaped muscle, covers superior part
of thorax

Pectoralis minor
◦ Located deep to pec. major
◦ Anterior wall of axilla (armpit) useful
anatomical landmark (will be discussed
in more detail later)
◦ Receive their blood supply from a
branch of acromiothoracic aa (will cover
in more detail later in course)
Muscle
Attachments
Innervation
Main Actions
Pec. major
Two heads:
Clavicular head: anterior
surface of medial half of
clavicle
Sternocostal: anterior of
sternum, upper 6
costalcartilages
To lateral lip of bicipital
groove of humerus
Medial and
lateral
pectoral
nerves
C5-8, T1
Adducts and medially
rotates arm at shoulder
joint.
Clavicular head alone
flexes the humerus
Sternocostal head
extends it from flexed
position
Pec. minor
3rd-5th ribs, near their
costal cartilage to
coracoid process of
scapula
Medial
pectoral
nerve
C8,T1
Stabilises scapula
(draws it anteriorly and
inferiorly against
thoracic wall)

3 layers of muscles
Inter-costal ‘between the ribs’

External Intercostal

Internal Intercostal

Innermost Intercostal

Attach from inferior border of
superior rib to superior border of
inferior rib

Innervation: intercostal nn

◦ Superficial
◦ Middle
◦ Deep
Important to know the
direction the fibres run!

External- hands in
pockets

Internal-hands on
chest
◦ Innermost the same as
internal
Also,
• Anteriorly external intercostals become
membranous
• Posteriorly internal intercostals become
membranous

External intercostals
◦ Fibres inferomedial
◦ Raise ribs when contracted,
during inspiration

Internal and innermost
intercostals
◦ Fibres superomedial
◦ Lower ribs during forced
expiration

Contents of a typical intercostal
space
◦ VAN bundle (intercostal vein, artery,
nerve from superior to inferior)
◦ Collateral bundle (branches from
VAN bundle)


The VAN bundle runs along the
inferior border of each rib in the
costal groove
In between the internal and
innermost intercostals
Rib (cross
section)
VAN bundle
External
Internal
Innermost
Collateral bundle





12 pairs of thoracic spinal nerves
Anterior rami of T1-T11 form the intercostal nerves
T12 is not intercostal- it runs under rib 12 and is known
as the ‘subcostal nerve’
Dermatome- area of
skin supplied by a
single spinal nerve
Myotome-the
muscles supplied by
a single spinal nerve
(including anterior
and posterior rami)

Thoracic aorta gives
rise to posterior
intercostal aa

Internal thoracic
arteries (branches
of subclavian aa)
give rise to anterior
intercostal aa

Veins drain in a similar
way

Anterior intercostal vv
drain into internal
thoracic veins

Posterior intercostal vv
drain into
azygos/hemiazygos
system of veins (which
drains into IVC)


Clinical cases to consider in tasking booklet
Cover the relevant anatomy!

Anatomy alone can explains many
conditions/diseases/procedures you will come across
in clinical practice

In the Summer you will have an exam on anatomy
surrounding clinical cases



For draining air/liquid from the pleural
cavity that shouldn’t be therepneumothorax/haemothorax
Pleural cavity
◦ Between visceral and parietal pleura
◦ Usually a ‘potential space’ filled only with
pleural fluid
Insert needle just superior to inferior rib
to avoid damaging VAN bundle, between
rib 4 and 5 in the midaxillary line
Visceral
pleura
Pleural
cavity
Parietal
pleura
An anatomy text (essential)
 Moore and Agur, ‘Essential Clinical Anatomy’
or
 Drake and Vogl, ‘Gray’s Anatomy for Students’
Others you may find useful (not essential unless you’re super
keen!):
 Lumley’s ‘Surface Anatomy’ (the be all and end all of surface
anatomy)
 McMinn’s ‘Clinical Atlas of Human Anatomy’ (images of
dissections, useful for the spotter)

Pictures
◦
◦
◦
◦

Moore and Agur, ‘Essential Clinical Anatomy’ 4th edition
Drake and Vogl, ‘Gray’s Atlas of Anatomy’
Drake and Vogl, ‘Gray’s Anatomy for Students’ 1st edition
http://alfa.saddleback.edu/N172/maintainChestTube.aspx
Support reading
◦ Moore and Agur, ‘Essential Clinical Anatomy’ 4th edition
Any questions?
[email protected]