Thoracic Cage - The thoracic cage consists of the sternum, the

ribs, and the thoracic vertebrae.- It has a narrow inlet and a wide outlet.I. Thoracic inlet: (the upper opening of the

thoracic cage)Boundaries:a. Anterior -------------- Supra-sternal notch of the

manubrium sterni.b. On each side --------- First rib.c. Posterior -------------- First thoracic vertebra.

RibsClassification of ribs according to their attachments to the

sternum:- There are twelve ribs on each side classified as:A: True ribs --------- Upper seven ribs (their anterior end is attached

to the sternum).B: False ribs --------- Lower five ribs (they are not attached anteriorly

to the sternum).- The lower two ribs are called the floating ribs because they are

free anteriorly. Classification of ribs according to their structure:A: Typical ----------- 3rd - 9th ribs.B: Atypical ---------- 1st, 2nd, 10th, 11th, and 12th ribs. (first two and

last 3) ribs)

Typical rib

Typical thoracic vertebra

Superior surface

Lateral surface

It contains:1- Intercostal muscles.2- Intercostal nerves.3- Intercostal arteries.4- Intercostal veins.

Intercostal musclesI. Outer layer ----- External intercostal

muscle II. Intermediate layer ----- Internal

intercostal muscle III. Inner layer ----- Transversus

thoracis group, subdivided into:1. Innermost inter-costalis 2. Sterno-costalis3. Sub-costalis

Intercostal MusclesLateral view

Transversus thoracis group Arrangements and extension of the muscles

Sub Costalis muscle in the posterior part of the wall

Intercostal Arteries

Intercostal Arteries: 1- Anterior Intercostal Arteries. 2- Posterior Intercostal Arteries. •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  

Anterior Intercostal Arteries Each anterior intercostal space contains two anterior intercostal arteries (except in the lower two inter-costal spaces).a. The upper 6 pairs arise from the internal thoracic artery.b. The 7th, 8th, and 9th pairs arise from the musculo-phrenic artery.

Internal thoracic (mammary) artery

Origin: From the first part of the subclavian artery.

Termination: opposite the sixth intercostal space by dividing into superior epigastric and musculo-phrenic arteries.

a

Internal thoracic (mammary) vein

- It is formed by the union of the two venae comitantes of the internal thoracic artery behind the third costal cartilage.- It ascends close to the artery to terminate in the corresponding innominate vein.

Posterior Intercostal Arteries- Each posterior intercostal space contains one posterior

intercostal artery which runs in the costal groove .

- Each artery gives a collateral branch

which runs over the upper border of the rib below.

*The upper two posterior intercostal

arteries superior intercostal artery (from the costo-cervical trunk) 2nd part of subclavian artery.

* From 3 - 11 posterior intercostal arteries and subcostal artery

descending thoracic aorta.

Intercostal Nerves- There are 11 intercostal nerves in the upper

11 intercostal spaces and a subcostal nerve below the last rib (on each side).

- Each intercostal nerve arises from the ventral ramus of the corresponding thoracic nerve.

- They are classified into:I. Typical Intercostal NervesII. Atypical Intercostal Nerves: which are the first intercostal nerve, second intercostal

nerve and lower five intercostal nerves .

 

I. Typical Intercostal Nerves

I. Typical Intercostal NervesBranches

1. Communicating branch to the sympathetic trunk.

2. Collateral branch which runs over the upper border of the rib below.

3. Anterior cutaneous branch .4. Lateral cutaneous branch which divides into

anterior and posterior branches.5. Muscular branches to the intercostal muscles.6. Sensory branches to the pleura.

II. Atypical Intercostal Nerves

1. First intercostal nerve- It has a small lat. Cut. Branch to the axilla and ends

as a small anterior cutaneous branch.2. Second intercostal nerve- Its lateral cutaneous branch is called the

intercosto-brachial nerve which supplies the base of the axilla and upper part of the medial side of arm and does not divide into anterior and posterior branches.

3. Lower five intercostal nerves - They reach the anterior abdominal wall at the

anterior ends of the spaces and supply its structures in addition to the diaphragm.

 

Arrangement of intercostal nerve and vessels in the costal groove

In the posterior end of the space the nerve is above the vessels.

Then, it crosses behind the vessels to continue below them (VAN).

In the posterior part , the vessels& nerve are midway between the two ribs.

In the lateral& anterior parts In the costal groove

Applied anatomy:

1. Stab wounds in the posterior part of the intercostal spaces lead to injury of the posterior intercostal nerve and vessels because they run midway between the ribs.

-But in the lateral part of the intercostal spaces, they do not injury the posterior intercostal nerve and vessels because these structures are protected by the costal groove.

 

Applied anatomy:

2. Needles introduced into the intercostal spaces (to remove collection in the pleura)

Site: They are done in the lateral part of the chest wall to avoid injury of the posterior intercostal nerve and vessels.

(It is also better to be introduced near the rib below).

Prof.: Dr. Wafaa Abdel-Rahman