Thorax

Question 1

Define Thorax and its boundaries

Answer 1

• Thoracic cage = Protective enclosure of the thoracic cavity and the superior viscera of the abdominal cavity
• Thoracic outlet= Area between collarbone and 1st rib. Contains blood vessels.
• The thoracic inlet= also known as the superior thoracic aperture, refers to the opening at the top of the thoracic cavity.

The function of Bones and Cartilage of thoracic wall: Providing protection, providing attachment sites for muscles of respiration and attachment sites for muscles that belong to other regions of the body.

Question 2

Describe the articulation between ribs and vertebrae

Answer 2

• Sternum = articular surface for clavicle and ribs 1-10
• Ribs 1-7 = articular with sternum directly. These are true ribs.
• Ribs 8-10 = Articular with sternum indirectly. False ribs
• Ribs 11-12 = do not articular with the sternum. Floating ribs

Question 3

Features of a rib

Answer 3

• Typical vs atypical rib

Question 4

Muscles of Respiration

Answer 4

• Intercostal muscles: Ext. (elevate ribs in inspiration), Internal (depress ribs in expiration) and innermost (elevates ribs in inspiration.
• Transversus thoracism = Aids depression of ribs and compression of the chest for forced expiration.
• Subclavius muscles = When contracts, elevates 1srt rib and depresses clavicle as well as protecting subclavian vessels that lie posterior to it.

Question 5

Contents of the intercostal space

Answer 5

• 3 layers of intercostal muscles = Innermost, internal and external
• Superior-> inferior = Posterior Vein, Artery, Nerve (VAN)
• Also subcostal V,A,N under,

Question 6

Explain inspiration and expiration

Answer 6

Inspiration:

• E.Intercostal muscles + diaphragm contract -> Ribs move superiorly and sternum moves anteriorly and diaphragm inferiorly.
• Increase intrathoracic volume (reduce pressure in alveoli)< so air gores from higher external atmospheric pressure and flows into the lungs

Expiration:

• Respiratory muscles relax -> ribs move inferiorly -> diaphragm moves up
• Decreases intrathoracic volume ( and increases pressure in alveoli). The difference between alveolar pressure and external atmospheric pressure, causes air to be expired from the lung

Function Diaphragm = fibres in vertical direction so when it contracts, it pulls centre portion of diaphragm inferior to increase space in thorac and this increases volume in lungs. In expiration it decreases vol to help force air out.