Intercostal space

Dr. Mohamed El fikyProfessor of anatomy and embryology

Floating ribs11&12

True ribs 1-7

False ribs8-10

Skeleton of the thoracic wall

Joints related to the sternum

Superior thoracic apertureThoracic inlet

• The superior thoracic aperture

consists of the body of vertebra TI

posteriorly, the medial margin of rib I

on each side, and the manubrium

anteriorly.

• The superior margin of the

manubrium is in approximately the

same horizontal plane as the

intervertebral disc between vertebrae TII and TIII.

• The first ribs slope inferiorly from

their posterior articulation with

vertebra TI to their anterior

attachment to the manubrium..

• The inferior thoracic aperture is large and

expandable. Bone, cartilage, and

ligaments form its margin

• The inferior thoracic aperture is closed

by the diaphragm, and structures

passing between the abdomen and

thorax pierce or pass posteriorly to the

diaphragm.

Inferior thoracic apertureThoracic outlet

• Skeletal elements of the inferior thoracic aperture are:

• the body of vertebra T XII posteriorly;

• rib XII and the distal end of rib XI posterolaterally;

• the distal cartilaginous ends of ribs VII to X, which unite to form

the costal margin anterolaterally; and the xiphoid process

anteriorly.

Joints of Skeleton of the thoracic wall

The intervertebral disc in between T2 and T3 vertebrae

The intervertebral disc in between T4 and T5 vertebrae

The Upper border of 9th Thoracic vertebra

T3

T4

T5

T6

T7

T8

T9

Intercostal spaces

Thoracic wallLayers of thoracic wall :

1- skin

2- superficial fascia

3-intercostal muscles

4- pleura

5- lung

.

ArteryVein

Nerve

Intercostal

Collateral branches

Intercostal muscles

1-They are arranged in three layers.

2- Are supplied by intercostal and

subcostal nerves.

3- Act in respiratory movements

External intercostal

Internal intercostal

Transversus thoracis

Intercostal muscles

Origin: From the sharp lower border

of the rib above.

Insertion: In the blunt upper border

of the rib below.

Direction of fibers : Downwards and

forwards.

Extension : From the tubercle of the

rib behind to the costo-chondral

junction where it is replaced by the

external (anterior)

intercostal membrane.

Action: Inspiratory.

External intercostal muscle

Internal intercostal muscle

Origin: From the inner surface of

the rib above (lateral to the costal

groove).

Insertion: In the blunt upper

border of the rib below.

Direction of fibres: Downwards

and backwards.

Extension: From the lateral

margin of the sternum infront to

the angle of the rib, where it is

replaced by the internal

(posterior) intercostal membrane.

Action : Expiratory.

Transversus thoracis muscle Represented by 3 sheets of muscles :

• sterno-costalis

• innermost intercostal

• Subcostales ,

A- Sterno-costalisOrigin: From the lower part of the internal

surface of the body of the sternum and xiphoid process.

Direction of fibres: Form 5 digitations, which diverge from the origin upwards and laterally.

Insertion: Inner surface of the 2nd to 6th

costal cartilages.

B- Innermost intercostals ( Intercostalis intimis)

Origin : From the inner surface of the rib above (medial to the costal groove). Direction of fibers : Downwards and backwards crossing more than one intercostal space. Insertion: Into the upper border of the 2nd or 3rd rib below.

Subcostalis

Origin: From the inner surface of the rib Direction of fibres: Downwards & backwards crossing more than one space Insertion : Into the upper border of the 2nd or 3rd rib below. @ Action of transversus thoracis : Support the sterno-costal & costo-transverse joints during movements of ribs.

Intercostal NervesThere are 11 pairs of intercostal nerves and one pair below 12th rib (subcostal nerve).

Typical intercostal nervesFrom 3rd to 6th

Atypical intercostal nerves

1- 1st

2- 2nd

3- lower five intercostal and subcostal

@Course & relations: u Posteriorly : Intercostal nerves There are 11 pairs of intercostal nerves and one pair below 12th rib (subcostal nerve). ØThe nerve lies between the parietal pleura and posterior intercostal membraneØ It crosses behind the intercostal vessels. Ø Laterally : (in the costal groove). o It runs in the costal groove.o It lies between the internal intercostal and the innermost intercostal muscles.o It runs below the intercostal vessels. From above downwards the arrangement is vein, artery & nerve (VAN). uAnteriorly :(medial to costo-chondral junction).Ø It crosses in front of the internal thoracic artery. •u Terminally:Ø It is directed forwards piercing the internal intercostal muscle, then the external intercostal membrane to end in the skin as the anterior cutaneous nerve.

Typical Intercostal Nerves

1.Branches:

1- Rami communicantes: A white and grey rami to the corresponding thoracic ganglion.

2. Collateral branch:

Ø Runs parallel to the main nerve along the upper border of the next rib

Ø It supplies parietal pleura, periosteum of the rib and muscles of the space.

Ø It has no cutaneous branch.

3- Lateral cutaneous branch:

Ø Pierces the internal and external intercostals and come out in the mid-axillary line.

Ø Each divides into anterior and posterior divisions.

4- Anterior cutaneous branch:

ØIt is the termination of the intercostal nerve.

Ø Pierces the internal intercostal muscle and external intercostal membrane

Ø Each divides into medial and lateral divisions.

5- Muscular branches: Supply the intercostal muscles.

1- Rami communicants

2- Muscular branches

3- CollateralBranch

4- Lateral cutaneous branch

Anterior branch

Posterior branch

Sternocostalis

Sternum

5- Anterior branchLateral branchMedial branch

Atypical Intercostal Nerves

1- 1st intercostal nerve:

Its main part ascends in front of the neck of the 1st rib to join lower trunk of the brachial plexus.

2- 2nd intercostal nerve:

Its course and branches are similar to the typical intercostal nerves , but it differs in that its lateral

cutaneous branch does not divide into anterior and posterior branches, but directed posteriorly and

crosses the axilla to supply the skin of the upper part of the medial side of the arm, so called inter-

costo- brachial nerv.e

3- Lower 5 intercostal nerves (7th to 11th ):

•• They supply the anterior abdominal wall.

•• The 10th nerve supplies the skin at the level of the umbilicus. 4- Subcostal nerve (12th)

•Runs below the 12th rib and ends above the symphysis pubis.

The intercostobrachial nerve of the Second Intercostal Nerve

The Lower 5 intercosal nerves

3- The Lower 5 Intercostal Nerves

Aorta

Left Subclavian Artery

Internal Thoracic (mam

mary) A

rtery

Costocervical TrunkSuperior Intercostal Artery

SuperiorEpigastric Artery

MusculophrenicArtery

1

2

3

4

5

6

7

8

9

1

2 3

4

5

6

7

8

9

collateral

collateral

collateral

collateral

collateral

collateral

collateral

collateral

collateral

The Anterior and The Posterior Intercostal ArteriesThe Intercostal Arteries

Two small arteries in each space except the last 2 spaces which have no anterior arteries. Origin : q Upper 6 spaces from the internal mammary

artery. q 7th, 8th & 9th spaces from the musculo-

phrenic artery. q 10th & 11th spaces there are no anterior

arteries.

Anterior intercostal arteries Subclavian artery

Internal mammary artery

Superior epigasteric artery

Musclophrenic artery

Ø Arises from the 1st part of subclavian artery.

Ø Descends vertically one finger breadth lateral to the sternum.

Ø Accompanied by venae commitantes from 3rd to 6th space.

Ø It ends in the 6th space by giving two terminal branches; musculo-phrenic & superior epigastric arteries.

Branches: 1- Pericardiaco-phrenic artery

2- Anterior intercostal arteries: 2 in each of the upper 6 spaces. 3- Perforating branches: They accompany the anterior cutaneous branches of the intercostal nerves 4- Musculo-phrenic artery: Passes along the costal margin. 5- Superior epigastric artery: Descends vertically and endsby anastomosing with theinferior epigastric artery

1.Internal thoracic (mammary) artery

1.Posterior intercostal arteries 1.Each space contains 2 anterior and 1 posterior arteries. 2.Each posterior artery anastomoses with the 2 anterior arteries. 1st and 2nd arteries:

Ø Arise from the superior intercostal artery, a branch of the costo- cervical trunk of the 2nd part of subclavian artery. Ø It descends in front of the neck of the 1st rib.

Lower 9 intercostal and subcostal arteries: Ø Arise from descending thoracic aorta.

Branches: · Dorsal: - Arises at the neck of the rib to supply the

back. - It gives off a spinal branch for the spinal cord. · Collateral: Arises near the angle of the rib.· Lateral cutaneous: Arises near the angle of the rib.

q 9 in number in each space.

q From the 9th, 8th and 7th spaces, end in the venae

commitantes of the musculo-phrenic artery.

q From the 6th to 3rd spaces; end in the venae

commitantes of the internal thoracic artery.

q From the 1st & 2nd spaces; end in the internal

thoracic vein which runs medial to the artery.

Anterior intercostal veins

venae commitantes of the

musculo-phrenic artery.

venae commitantes of the

superior epigasteric

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Posterior intercostal veins - There are 11 pairs arranged as follows:

- 1st space drains into corresponding

brachio-cephalic vein.

- 2nd & 3rd spaces drain into superior intercostal vein

which:

q On the right side ends in the arch of azygos

vein.

q On the left side ends in the left brachio-

cephalic vein.

•- 4th to 11th spaces.

•- On the right side: end in the azygos vein.

•- On the left side:

o From 4th to 8th join the accessory hemi-azygos vein.

o From 9th to 11th join the hemi-azygos.

-The 12th vein ( subcostal vein) unites with the

ascending lumbar vein.

AZYGOS VEIN q It arises in the abdomen from the back of inferior vena

cava. q It enters the thorax with the aorta, where it ascends to

its right border. q At the level of the sternal angle, it forms an arch which

ends in the superior vena cava. q Runs on vertebral bodies on the right side of the

descending thoracic aorta q and then behind the right border of the oesophagus. q Ascends behind the root of right lung and then curves

forwards above the root, forming the arch of vena azygos which crosses on the right side of oesophagus, trachea and right vagus nerve to end in the middle of the superior vena cava.

q · Tributaries :o Right ascending lumbar vein in the abdomen.o Right subcostal vein.o Right posterior intercostal veins from the 4th to 11th.o Right superior intercostal vein.o Superior and inferior hemi-azygos veins.o Bronchial veins from right lung.o Some oesophageal and pericardial veins.N.B. All venous blood from thoracic wall drains into superior vena cava.

Hemi-azygos veins q • These 2 veins lie on the left side of the vertebral column and drain the left side of the thoracic wall. q • They are the superior and inferior hemi-azygos veins :

1.• It receives the left posterior intercostal veins from the 4th to 8th spaces. 2.• It crosses the median plane to the right side at the 7th thoracic vertebra 3.behind the aorta, oesophagus and thoracic duct to join the azygos vein.

1.Superior hemi-azygos vein

1.Inferior hemi-azygos vein q It arise either from the back of the left renal vein or from union of the left ascending lumber and

left subcostal veins q It enters the thorax by piercing left crus of diaphragm q It receives the lower left posterior intercostals veins from 9th to 11th q It receives also oesophageal and mediastinal veins q It crosses the median plane to the right side at 8th thoracic vertebra to q join the azgos vein .

Thank You

Dr. Fiky Thorax