Lecture 21 - Muscles Of The Anterior Trunk

Question 1

What are the main actions of the obliques?

Answer 1

• rotation & side flexion

Question 2

What is abdominal rotation?

Answer 2

• Contraction of external & internal obliques on OPPOSITE sides
• I.e., trunk rotation to the right = left EAO + right IAO
• i.e., trunk rotation to the left = right EAO + left IAO

Question 3

What is abdominal side flexion?

Answer 3

• Contraction of external & internal obliques on the SAME SIDE
• I.e., trunk side flexion to the right = right EAO + right IAO
• i.e., trunk side flexion to the left = left EAO + left IAO

Question 4

What are the 5 muscles of the anterolateral abdominal wall?

Answer 4

• external abdominal obliques (EAO)
• internal abdominal obliques (IAO)
• transverse abdominus (TA)
• rectus abdominus (RA)
• pyramidalis

Question 5

What is the origin/insertion/innervation/main action of the external abdominal obliques?

Answer 5

• O: External surfaces of ribs 5-12
• I: Linea alba, anterior half of iliac crest
• Inn: Segmental
• MA: Trunk rotation & side flexion

Question 6

What is the origin/insertion/innervation/main action of the internal abdominal obliques?

Answer 6

• O: Thoracolumbar fascia, anterior 2/3 iliac crest, lateral half inguinal ligament
• I: Inferior borders of ribs 10-12, linea alba
• Inn: Segmental
• MA: Trunk rotation & side flexion

Question 7

What is the origin/insertion/innervation/main action of the transverse abdominus?

Answer 7

• O: internal surface costal cartilages ribs 7- 12, thoracolumbar fascia, iliac crest, connective tissue deep to lateral 1/3 inguinal ligament
• I: Linea alba
• Inn: Segmental
• MA: Acts as a corset to stabilize the spine and increase intra-abdominal pressure

Question 8

What is the origin/insertion/innervation/main action of the rectus abdominus?

Answer 8

• O: Pubic symphysis & pubic crest
• I: Costal cartilages of ribs 5-7, xiphoid process
• Inn: Segmental
• MA: Trunk flexion

Question 9

What is the Pryamidalis? What is its main action?

Answer 9

• Lies anterior to the inferior end of rectus abdominals
• Main Action = Tenses linea alba

Question 10

What are the 4 muscles that facilitate respiration?

Answer 10

• diaphragm
• intercostals (3): external, internal, innermost

Question 11

What is the external/internal/innermost intercostal muscles?

Answer 11

• External Intercostal: Extends down & anterior (hands in pocket)
• Internal Intercostal: Extends down & posteriorly
• Innermost Intercostal: Incomplete, thin & closely adhered to the internal intercostals

Question 12

What are the origins of the diaphragm?

Answer 12

• 3 divisions based on peripheral attachments:
• Sternal: xiphoid process
• Costal: inferior surfaces ribs 6-12
• Lumbar: medial & lateral arcuate ligaments, L1-L3

Question 13

What is the insertion/innervation/main action of the diaphragm?

Answer 13

• I: Central Tendon
• Inn: Phrenic nerve (C3, C4, C5)
• MA: Facilitates respiration

Question 14

What is the linea alba?

Answer 14

• Extends from diploid process to pubic symphysis
• Created by the abdominal muscles