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THORAX
THE THORACIC CAGE :Boundaries:
Behind:
 Bodies of twelve thoracic
vertebra and their
intervening discs
 Posterior parts of ribs
In front:
 Sternum
 Anterior part of ribs and
their costal cartilages
On each side:
Twelve ribs
Inlet of thorax:
It is reniform in shape
Outlet:
It is closed by the diaphragm
Skeleton of thorax:
 Thoracic vertebra
 Ribs
 Sternum
Thoracic vertebra:
 They are 12 in number
 They are recognized by the
presence of costal facets on
sides of the bodies and
transverse process
Classification:
Typical thoracic vertebra:
Second to Eight
Atypical thoracic vertebra:
First, Nine to Twelve
Features of typical thoracic vertebra:
Body , Vertebral foramen,
Superior articular facets
Transverse process & Spinous process
Body:
☻ It is heart shape
☻ Presence of two two costal demifacets
Vertebral foramen:
☻ Small and circular in shape
☻ Pedicles are short
☻Lamina are short, thick and broad
The transverse process:
☻ Tips bear oval costal facets
Spinous process:
☻ Long and slopes downward
Sternum:
Consists of three parts
☻Manubrium
☻Body
☻Xiphoid process
Manubrium:
Body:
Xiphoid process:
THE RIBS:
☻ Arranged in twelve pairs
☻Posteriorly it articulates
with the thoracic vertebra
☻Anteriorly joins with the
sternum through their
respective costal cartilages
directly or indirectly
Classification of
ribs:
☼True ribs:
Upper seven pairs
(Vertebrosternal ribs)
☼False ribs:
Lower five pairs
(Vertebro-chondral ribs)
‡Typical ribs:
3rd to 9th ribs
‡Atypical ribs:
1st, 2nd, 10th 11th and 12th ribs
Typical ribs:
☻ Sternal end
☻Vertebral end
☻Intervening shaft
Sternal end:
☻ Lower than vertebral end
and receives its own costal
cartilage
Vertebral end:
It includes:
- Head
- Neck
- Tubercle
Shaft:
It is thin flat and curved
Applied anatomy:
Fracture of ribs:
Pneumothorax or Haemothorax
INTERCOSTAL SPACE
Intercostal space:
Eleven in number on each side
Last two intercostal spaces are open in front
Typical Intercostal space:
• Those spaces intervening between typical ribs and
traversed by vessels and nerves which are confined to
the thoracic wall, are known as typical intercostal
space
• As such 3rd , 4th, 5th and 6th intercostal space are
typical
Boundaries of typical intercostal space:
Above:
Lower margin of upper rib
and its cartilage
Below:
Upper margin of the lower
rib and its cartilage
In front:
Lateral border of sternum
between the costal notches
Behind:
Body of corresponding
thoracic vertebra
Contents of space:
Muscles
Vessels and
 Nerves
Muscles:
They are arranged in three sheets from outside to
inside:
Intercostalis externus
Intercostalis internus
Intercostalis intimus
Intercostalis externus:
Intercostalis internus:
Intercostalis intimus:
† It occupies middle 2/4th of
typical intercostal space
† Intercostal vessels and nerves
passes between intercostalis
internus and intimus muscle
Intercostal vessels:
Arteries:
Anterior intercostal arteries
In each space the arteries are
Posterior intercostal arteries
arranged in two groups
Anterior intercostal arteries:
Upper six spaces:
Internal thoracic artery
Lower three spaces:
Musculo-phrenic artery
Posterior intercostal arteries:
Upper two spaces:
Superior intercostal artery
Lower nine spaces:
Descending thoracic aorta
intercostal veins:
In each space the veins are arranged in two groups
Anterior intercostal veins
Upper six spaces
Internal thoracic vein
Lower three spaces
Musculophrenic vein
Posterior intercostal veins
On right side
Azygous vein
On left side
Hemiazygous vein
intercostal Nerve:
ɸ They are eleven in number
ɸ Each nerve is ventral ramus of a thoracic nerve
ɸ Ventral ramus of 1st thoracic nerve forms lower trunk of
brachial plexus
ɸ Lateral cutaneous branch of 2nd intercostal nerve remains as
intercostobrachial nerve
ɸ 3rd to 6th intercostal nerves are called as typical intercostal
nerves
ɸ 7th to 11th intercostal nerves appears in anterior abdominal wall
Branches:
† Rami communicantes
† Collateral branch
† Lateral cutaneous branch
† Muscular branches run to
the intercostal muscles.
† Pleural sensory branches
go to the parietal pleura.
† Peritoneal sensory
branches (7th to 11th
intercostal nerves only) run
to the parietal peritoneum
Applied anatomy:
Intercostal neuralgia:
It is a sharp burning pain in the area of skin supplied by
thoracic spinal nerve produced by rib fracture
Herpes zoster
Caused by a virus called as varicella-zoster virus