Thoracic Inlet Relations and Cross Sectional Anatomy

THORACIC INLET RELATIONS AND CROSS SECTIONAL ANATOMY

Learning Objectives

At the end of this class the student will be able to,

•Under stand the location of the thoracic inlet.

•Under stand the boundaries of thoracic inlet.

•Under stand the important relations of different structures at this level

THORACIC INLET

•Thoracic inlet is reniform.

•About 5 cm anterioposteriorly.

•About 10 cm transversely.

•Plane of inlet slops downwards and inwards.

BOUNDARIES

•Behind is the first thoracic vertebrae.

•In front is superior border of manubrium sternae.

•On each side is first rib.

•In female thoracic inlet is more oblique than in man.

Structure traversing the superior thoracic aperture:

•Form two groups.

•1.Those in or near the median plane.

•2.Those on each side (closely related to the cervical parts of pleurae and lungs).

Suprapleural membrane

•Thickening of endothoracic fascia

•Tent shaped fibrous sheet

•covers lateral part of inlet

Attachment

•Laterally

–medial border of first rib and costal cartilage

•at its apex

–transverse process of 7th cervical vertebrae

•Medially

–fascia investing the structures passing through inlet

Function

•Protects underlying cerviacal pleura

•Resist changes in intrathoracic pressure

•NEAR THE MIDLINE.

•1.Behind the manubrium:

•The lowest parts of the sternothyroid muscles enter the thorax.

•Behind are the sternothyoid muscles,thymic vestiges and inferior thyroid veins passing down to brachiocephalic veins.

2.In children.

•Particularly the left brachiocephalic veins it self may be in the thoracic inlet.

3.Posteriorly.

•Trachea and oesophagus with the recurrent laryngeal nerves (which occupy the median region).

4.Behind the left oesophageal margin.

•Thoracic duct enters the neck.

5.Anterior to the vertebral column.

•The longus colli muscles and anterior longitudinal ligament.

ON EACH SIDE.

1.The upper part of the pleura and pulmonary apex occupy the inlet.

2.Between the pleura and neck of first rib (mediolaterally), are the sympathetic trunk.Superior intercostal artery and ventral ramus of first thoracic nerve passing (superolaterally) to the brachial plexus.

3.Anteriorly. Between pleura and first costal cartilage, the internal thoracic artery enters the thorax, medial to the artery its vein leaves the thorax.

ON THE RIGHT.

•The brachiocephalic artery leaves the thorax between the trachea and pleura.

•The vagus nerve, having passed between subclavian artery and veins, is between pleura and the brachiocephalic artery at the inlet.

•The right brachiocephalic artery at the inlet.

•Right brachiocephalic vein enters the thorax anterolateral to its artery.

•The right phrenic nerve crosses the internal thoracic artery and its lateral to the first costal cartilage.

ON THE LEFT.

•The left common carotid and subclavian arteries leaves the thorax between the pleura and trachea, the left vagus nerve descending lateral to the interval between them.

•Anterolateral to this is the left brachiocephalic vein.

•The left phrenic nerve crosses the internal thoracic artery at a higher level than on the right hand and, at the inlet, it is between the left brachiocephalic vein anterolaterally and subclavian and common carotid arteries posteromedially.

STRUCTURES RELATED TO RIGHT CERVICAL PLEURA FROM BELOW

STRUCTURES RELATED TO RIGHT CERVICAL PLEURA FROM BELOW