Lecture 7 materials - Thoracic muscles

Question 1

What are epaxial muscles?

Answer 1

Epaxial muscles lie dorsal to the transverse processes on the vertebrae and extend the vertebral column

Epaxial muscles produce lateral movements when acting on one side

Question 2

What are hypaxial muscles?

Answer 2

Hypaxial muscles run ventral to the tranverse processes. They represent all trunk muscles not included in the epaxial muscles.

This includes muscles of the thoracic and abdominal walls

Question 3

Name the epaxial muscle groups

Answer 3

Transversopinalis, Longissimus, Iliocostalis

Question 4

Which epaxial muscle group does not have a cervical component?

Answer 4

Iliocostalis

Question 5

What are many of the thoracic muscles involved with?

Answer 5

Respiration

Question 6

How do thoracic muscles assist with inspiration?

Answer 6

Inspiratory muscles move to enlarge the volume of the thoracic cavity

This decreases the pressure within the thoracic cavity which moves air in to the lungs

Question 7

How do thoracic muscles assist with expiration?

Answer 7

Expiratory muscles increase the pressure within the thoracic cavity which expels air from the lungs

Question 8

What is the most important muscle of inspiration?

Answer 8

Diaphragm.

Question 9

What muscles draw the ribs cranially and laterally?

Answer 9

Scalenus - attached to transverse processes of the cervical vertebrae cranially and the first ribs caudally

Serratus dorsalis cranialis - attached to the thoracolumbar fascia and courses caudoventrally to the craniolateral surface of ribs 2 - 10

Question 10

Is expiration active or passive?

Answer 10

Passive

Question 11

How is expiration accomplished?

Answer 11

A contraction of the abdominal wall and muscles of the thoracic wall draw ribs caudally and medially

Serratus dorsalis caudalis

Question 12

Describe intercostal muscles

Answer 12

Intercostal muscles run from rib to rib to draw the ribs together (neither inspiratory or expiratory)

Question 13

How to differentiate between external and internal intercostal muscles?

Answer 13

External intercostal muscles have fibers that run caudoventrally

Internal intercostal muscle fibers run cranioventrally

Question 14

Describe the movement of the ribs and diaphragm

Answer 14

During inspiration the ribs move forward and out which moves the diaphragm caudally and increases the thoracic cavity space (decreases pressure and moves air in)

Question 15

Are external intercostal muscles always superficial to internal intercostal muscles?

Answer 15

No, internal intercostal muscles move down the trunk farther than external intercostal muscles and can be seen towards the ventral portion of the trunk