Thorax

Question 1

in living subjects, in the erect posture, the bifurcation of trachea

Answer 1

lies at the lower border of the sixth thoracic vertebra and descends still further during inspiration

Question 2

Trachealis

Answer 2

Posteriorly there is a gap which is closed by a fibroelastic membrane and contains transversely arranged smooth muscle known as trachealis.

As the tracheal rings are incomplete posteriorly the oesophagus can dilate during swallowing. This also allows the diameter of the trachea to be controlled by the trachealis muscle. This muscle narrows the caliber of the tube, compressing the contained air if the vocal cords are closed. This increases the explosive force of the blast of com- pressed air, as occurs in coughing and sneezing.

Question 3

Arterial supply of trachea
Venous drainage
Nerve supply

Answer 3

Inferior thyroid arteries brachiocephalic vein

1. Parasympathetic: Nerves through vagi and recurrent laryngeal nerves. It is:
   a. Sensory and secretomotor to the mucous
   membrane.
   b. Motor to the trachealis muscle.
   2 Sympathetic: Fibres from the middle cervical ganglion reach it along the inferior thyroid arteries and are vasomotor

Question 4

Tracheal Tug

Answer 4

During swallowing when the larynx is elevated, the trachea elongates by stretching because the tracheal bifurcation is not permitted to move by the aortic arch. Any downward pull due to sudden and forced inspiration, or aortic aneurysm will produce the physical sign known as ‘tracheal tug’

Question 5

Contents passing through diaphragm

Answer 5

1. Opening of IVC
      Right phrenic nerve
2. Superior epigastric vessels
3. Oesophageal opening
      Oesophageal branch of Left epigastric artery and veins
      Vagus nerves

With aorta : azygous vein and thoracic duct
Behind lat. arcuate lig. Subcostal vessles & nerves
Behind med. arcuate lig. Sympathetic chain