Muscles of thorax

Question 1

Diaphragm actions

Answer 1

Prime mover for inspiration

Question 2

Diaphragm attachments

Answer 2

-Bodies and intervening discs L1-L3
-Inner surface of ribs 7-12 and their costal cartilages
-Posterior surface pf Xiphoid process of the sternum
-Central tendon

Question 3

Apertures of diaphragm

Answer 3

-Abdominal aorta
-Oesophagus
-Inferior vena cava

Question 4

Abdominal aorta

Answer 4

-T12
-behind diaphragm
-Not affected by diaphragm contraction

Question 5

Oesophagus

Answer 5

-T10
-Through muscle of diaphragm
-Sealed closed by diaphragm contraction

Question 6

Inferior vena cava

Answer 6

-T8
-Through the central tendon
-Opened by diaphragm contraction

Question 7

Intercostals

Answer 7

-From lower border of one rib to the upper border of the rib below.
-Three layers= External, Internal and innermost
-Stiffen space between ribs, role in breathing and in posture

Question 8

Inspiratory muscles

Answer 8

-Accessory muscles of inspiration
-Any muscle attaching to the ribs from above can lift the ribs and hence increase the thoracic volume.
eg serratus anterior, pec major, minor and sternomastoid

Question 9

Expiratory muscles

Answer 9

-Largely passive in awake humans
-Diaphragm contracts eccentrically for a short period at the commencement of expiration to slow expiratory rate.
Forced expiration=abdominal muscles and any other muscle that pull the ribs down eg serratus posterior inferior and quadratus lumborum