Thoracic wall

Write vertebral level of the following.

Name the structures forming boundaries of superior thoracic aperture (thoracic inlet).

Boundaries of  thoracic inlet:

• Posteriorly: first thoracic vertebra
• Laterally : first pair ribs  and their costal cartilage .
• Anteriorly: superior border of  manubrium sterni. 

Name the structures that pass through the superior thoracic aperture (thoracic inlet).

 Structures that pass through the superior thoracic aperture include:

1. Trachea
2. Oesophagus
3. Thoracic duct
4. Nerves
   • Vagus
   • Phrenic
   • Left recurrent laryngeal
   • Sympathetic trunks
5. Vessels
   • Arteries
     • Left and right common carotid arteries
     • Left and right subclavian arteries
   • Veins
     • Internal jugular veins
     • Brachiocephalic veins
     • Subclavian veins
   • Lymph nodes and  lymphatic vessels

Enumerate the contents of a typical intercostal space.

Contents of a typical intercostal space are:

1. Intercostal muscles ( external, internal and innermost intercostal)
2. Intercostal nerve and its branches
3. Anterior and posterior intercostal arteries
4. Anterior and posterior intercostal veins. 

Enumerate the intrinsic muscles of thoracic wall.

 Intrinsic muscles of thoracic wall are:

1. External intercostals (outer layer)
2. Internal intercostals ((intermediate layer)
3. Innermost intercostals
4. Sternocostalis
5. Subcostalis

Enumerate the branches of a typical intercostal nerve (3rd -6th Name the structuresintercostal nerves) 

 Branches of a typical intercostal nerve (3^rd – 6^th intercostal nerves ) are:

1. Two communicating branches (white and gray ramus) which connect it to the corresponding sympathetic ganglion.
2. Muscular branches: Number of muscular branches that suppy intercostal muscles, subcostalis and sternocostalis.
3. Collateral branch that supplies parietal pleura and periosteum of rib besides supplying intercostal muscles.
4. Cutaneous branches:
   • Lateral cutaneous branch (reaches skin by piecing muscles at midaxillary line and divides into anterior and posterior branches)
   • Anterior cutaneous branch(reaches skin by piecing muscles about 1cm. lateral to the sternum and divides into medial and lateral branches).

Name the arteries that supply thoracic wall.

   Arteries supplying thoracic wall are:

1. Superior intercostal artery ( a branch of costocervical trunk from the second part of subclavian trunk) gives posterior intercostals arteries first two intercostal spaces.
2. Two anterior intercostal arteries for each intercostal space (in upper six intercostal spaces they are direct branches of internal thoracic artery(ITA) and in 7^th , 8^th & 9^th  they aris from musculphrenic artery ,a branch of ITA, 10^th and 11^th intercostals spaces don’t have anterior intercostal arteries ).
3. Posterior intercostal arteries: for 3^rd to 11^th intercostal space they arise from descending thoracic aorta.

Name the structures present at the level of sternal angle.

Structures  present at the level of sternal angle:

1. Ascending aorta ends
2. Arch of aorta begins and ends
3. Descending aorta begins
4. Trachea bifurcates into right and left principal bronchii.
5. Pulmonary trunk divides into right and left pulmonary arteries.
6. Azygous veins drains into superior vena cava
7. Upper border of heart lies at this level

* Sternal angle(angle of Louis) which can be easily palpated is used for counting ribs. The second costal cartilage articulates with sternum at this level.

Draw labelled diagram showing structures passing through the thoracic inlet (transverse section).

Structures passing through the thoracic inlet (transverse section)

Draw labelled diagram  of a typical intercostal space.

 Typical intercostal space

Draw  transverse section (TS) of intercostal space showing intercostal muscles and course & branches of intercostal nerve.

TS  of intercostal space showing intercostal muscles and course & branches of intercostal nerve.

Draw  labelled diagram showing tributaries of azygous vein.

Tributaries of azygous vein

Enumerate the factors responsible for the increase in various diameters of the thoracic cavity during  inspiration.

During inspiration the volume of thoracic cavity increases to allow expansion of lungs. The following factors are responsible for increase in the diameters of thoracic cavity.

• Vertical diameter is increased by contraction of diaphragm.
• Anteroposterior diameter is increased by anterior movement of sternum due to elevation of vertebrosternal (1^st-7^th) ribs (Pump handle movement).
• Transverse diameter is increased due to elevation of vertebrochondral (8^th, 9^th & 10^th ) ribs ( bucket handle movement).

Name the muscles that are responsible for inspiration and expiration.

The muscles that  are responsible for inspiration and expiration are: