Muscular System Pt. 8 - Muscles of The Thorax and Abdominal Wall

Question 1

Which muscle is the cut off between the abdominal muscles and thorax muscles?

Answer 1

Diaphragm

Question 2

Origin for the Diaphragm

Answer 2

Lumbar vertebrae, inferior ribs, and xiphoid process

Question 3

Insertion of Diaphragm

Answer 3

Central tendon

Behind the xiphoid process in the middle of all three origins

Question 4

Actions of Diaphragm

Answer 4

Increases vertical dimensions of thorax

Allows lungs to push down when the diaphragm contracts

Question 5

What are the muscles (of the diaphragm) doing when contraction occurs?

Answer 5

Insertion moves towards the origin so it flattens out

Question 6

What are the three intercostal muscles? What’s the main distinguishing feature for them?

Answer 6

External, Internal and Innermost intercostal muscles
Distinguishing feature is how superficial and deep they are to one another

Question 7

Origin of the three intercostal muscles

Answer 7

Superior border of the rib below or Inferior border of above (external intercostal only)

Question 8

Insertions of the three intercostal ribs

Answer 8

Superior border of each rib below (External) or Inferior border of rib above (Internal & Innermost)

Question 9

Which direction do the fibres run for External Intercostal and how do their movements affect the rib movement

Answer 9

Fibres (down and forward); Inspiration allows for the ribs to raise

Question 10

Which direction do the fibres run for Internal Intercostal and how do their movements affect the rib movement

Answer 10

Fibres (down and backward); Expiration allows ribs to be lowered

Question 11

Which direction do the fibres run for Innermost Intercostal and how do their movements affect the rib movement

Answer 11

Fibres (down and backward); lowers ribs during expiration

Same as internal

Question 12

How many abdominal muscles are there?

Answer 12

4 - Rectus abdominus, External Oblique, Transversus abdominus and Internal Oblique

Question 13

What are the rectus sheath and the linea alba?

Answer 13

Contains rectus abdominus underneath is and the linea alba joints the rectus sheath of both left and right rectus abdominus

Question 14

Origin of External Oblique Muscles

Answer 14

Ribs

Question 15

Insertion of External Oblique

Answer 15

Linea Alba & Iliac crest

Question 16

Actions of External Oblique

Answer 16

• Trunk Flexion
• Trunk lateral rotation
• Trunk rotation
• Compresses abdomen

• Compressing abdomen would be contracting all the abdominal muscles
• Lateral rotation of trunk means tipping to the side

Question 17

Origin of Internal Oblique

Answer 17

• Lumbar fascia (on back)
• Iliac crest
• Inguinal ligament

Lumbar fascia is like the rectus sheath except it’s on the back

Question 18

Insertion of Internal Oblique

Answer 18

• Linea Alba
• Lower ribs

Question 19

Actions of Internal Oblique

Hint: Exact same as external

Answer 19

• Trunk flexion
• Trunk lateral rotation
• Trunk rotation
• Compresses abdomen

Question 20

Origin of Transversus Abdominus

Deepest Muscle

Answer 20

Lumbar Fascia, Iliac crest, Inguinal ligament

Distinguish them from other abdominal muscles because they run horizontal

Question 21

Insertion of Transversus Abdominus

Answer 21

• Linea Alba
• Pubis

Question 22

Actions of Transversus Abdominus

Answer 22

Compresses abdomen

Question 23

Origin of Rectus Abdominus

Answer 23

Pubis Bone

Question 24

Insertion of Rectus Abdominus

Answer 24

Xiphoid Process & Lower Ribs

Question 25

Actions of Rectus Abdominus

Answer 25

• Trunk flexion
• Compresses abdomen