Anatomy of chest

Question 1

What is the thoracic inlet and outlet?

What is the abdominal inlet and outlet?

Answer 1

Thoracic inlet is neck and outlet is diaphragm

Abdominal inlet is diaphragm and outlet is pelvic diaphragm

Question 2

What are the anterior articulations of each rib?

Answer 2

All ribs articulate anteriorly with costal cartilage via a primary cartilaginous joint (hyaline).

True ribs (cc1-7) articulate directly with sterrnum via synovial joints to allow movement - except CC1 which is a primary cartilaginous joint making thoracic inlet more stable.

False ribs (cc8-10) articulate with the costal cartialge above to form the costal margin

Floating ribs (cc11-12) have no anterior articulation

Question 3

What are the intercostal space arterial supplies in anterior?

Answer 3

Internal thoracic (mammary)

• Branch of the first part of the subclavian artery
• Lies along margin of sternum
• Terminates as the superior epigastric and musculophrenic arteries
• Also supplies medial half of breast

Anterior intercostal arteries

• 2 per space in spaces 1-6
• 7-10 from musculophrenic
• 11 and 12 have no anterior supply

Question 4

What are the intercostal space arterial supplies in posterior?

Answer 4

First part of the subclavian artery
- Costocervical trunk suppleis first two spaces via supreme intercostal artery

Thoracic aorta

• 9 pairs of posterior intercostal arteries
• 2 per space in spaces 3-11 (passing with the intercostal nerves and their collateral branches)
• 12th branch is subcostal artery

Ant and post arteries anastomose in the space (remember coarctation of the aorta)

Question 5

Venous drainage of intercostal spaces?

Answer 5

Venae comitantes of the anterior and posterior intercostal arteries

Anteriorly, to the internal thoracic vein

Posteriorly:

• 1st space drains to the brachiocephalic vein
• 2nd and 3rd space - the veins form a superior intercostal vein
• On the right it drains to the arch of the azygos and on the left to the left brchiocepahlic vein (crossing the aortic arch between the phrenic and vagus nerves)
• All other intercostal spaces drain to the Azygos system - azygos vein on the right and hemi-azygos (upper and lower) on the left

Question 6

Lympathic drainage of thoracic wall

Answer 6

Anteriorly, drains to parasternal nodes that lie alongside the internal thoracic (mammary) artery and rain into the bronchomediastinal trunks
Posteriorly, drains to intercostal nodes that lie on heads of ribs and rain to either the thoracic duct (inferiorly) or to the bronchomediastinal trunks (superiorly)

More superficial structures (skin, breast, superficial muscles) drain to the axillary nodes, as may lung tumours eroding into tissues superficially

Question 7

Thoracic spinal nerves (T1-T12)

Answer 7

Mixed spinal nerves divide into ventral and dorsal rami

Ventral ramus of T1 goes to Brachial plexus - upper limb but it does supply muscles of 1st intercostal space

Ventral rami of T2-T11 are intercostal nerves and carry:

• motor fibres to intercostal muscles
• sensory fibres from skin and parietal pleura
• sympathetic fibres to body wall structures via WRC (white rami communicantes, 1y or pre-ganglionic) and GRC (grey rami communicantes, 2y or post-ganglionic)

The ventral ramus of T12 is subcostal nerve

Question 8

Mechanisms of respiration

Answer 8

Inspiration - diaphragmatic contraction to create a negative pressure, rib elevation pushes sternum up and forwards and ribs outward to increase anteroposterior and lateral diameters

Exhalation - muscle relataxtion and elastic recoil

Question 9

Embryonic development of heart tube folds into two sinuses within the serous pericardium - what are they?

Answer 9

1. Transverse sinus - between arterial and venous ends

2. Oblique sinus - potential space behind the left atrium

Question 10

From what structures is the apex of heart formed and where is it palpable?

Answer 10

Left ventricle - palpable in 5th left intercostal space, mid-clavicular line