Topic 10: MUSCLES OF THE BACK, NECK AND ABDOMEN Flashcards
Muscles of the anterior abdominal wall
- rectus abdominus
- external obliques
- internal obliques
- transversus abdominus
- pyramidalis
- Rectus Abdominus
PA
xiphoid process of sternum, costal cartilages of ribs 5,6, and 7
- rectus abd
DA
pubic crest, and pubic symphysis
- Rectus Abdominus
Actions
- trunk flexion (bilateral contraction)
- lateral flexion (unilateral contraction)
what is the rectus abdominus enclose by at the front and back?
rectus sheath
What is the rectus sheath formed from?
the aponeuroses of the 3 lateral abdominal muscles
What happens to the rectus sheath fibres at the mid-line?
fibres meet and cross over to form a dense fibrous raphe called the linea alba
Where does the linea run from?
the xiphoid process to the pubic crest & pubic symphysis
- External Oblique
PA
outer border lower 8 ribs and costal cartilages
- External Oblique
DA
iliac crest, linea alba
- External Oblique
Actions
- trunk flexion (sag plane)- bilateral
- contralateral rotation
What happens to the lower edge of the external obliques?
it is free and forms the inguinal ligament
- Internal oblique
PA
lower border lower 4 ribs and costal cartilages
- Internal oblique
DA
iliac crest, linea alba
- Internal oblique
Actions
- ipsilateral rotation
- some trunk flexion
what happens to the lower edge of the internal obliques?
joints to the inguinal ligament to contribute to the inguinal canal
- Transverse abdominus
PA
inner surface of the costal cartilages of the lower 6 ribs
- Transverse abdominus
DA
iliac crest, thoracolumbar fascia (post), inguinal ligament (ant)
- Transverse abdominus
Functions
increases intra-abdominal pressure (expiration)
What happens to the lower edge of the transversus abdominus?
joins to the inguinal ligament to contribute to the inguinal canal
- Pyramidalis
PA
symphysis pubis and superior margin of pubis
- Pyramidalis
DA
linea alba
- Pyramidalis
Action
tenses the lower linea alba
Muscles of the posterior abdominal wall
- Quadratus lumborum
- Psoas major
- Psoas Minor
- Quadratus Lumborum
PA
lower border rib 12, transverse processes of L1- L5
- Quadratus Lumborum
DA
iliac crest & iliolumbar ligament
- Quadratus Lumborum
Actions
- trunk extension (not really)
- lateral flexion
- anterior pelvic tilt (also ipsilateral tilt)
- if pelvis fixed, depress rib 12 (expiration)
- Psoas Major
PA
TP’s of L1-5, bodies and discs of T12- L5
- Psoas Major
DA
lesser trochanter of femur
- Psoas Major
Actions
- hip flexion
- fixed femur; trunk flexion
- Psoas Minor
PA
bodies & discs of T12 & L1
- Psoas Minor
DA
pecten pubis, superior pubic ramus
- Psoas Minor
Actions
trunk flexion if present
Fun fact about the psoas minor
often absent in many people
INNERVATION OF THE ABDOMINAL WALL
What are the muscles of the anterolateral abdominal wall supplied by?
ventral rami of thoracic spinal nerves
Rec abd nerve supply
T6/7- L1
Ext obliques NS
T7-T12
Int obliques NS
T7-L1
Transversus abdominus NS
T7-L1
General features of muscles of the back
Arranged in “sheets” which extend along the vertebral column
3 groups of back muscles
- erector spinae group
- transversospinalis group
- uni-segmental group
Features of the erector spinae group
- vertical sheet
- superficial
- extends the length of the VC
Features of the transversospinalis group
- oblique sheet
- deep to erector spinae
Features of the uni-segmental group
deep to transversospinalis group
What are the muscles of the back supplied by?
the dorsal (posterior primary) rami of spinal nerves
- erector spinae group
Function
“erects” the spine
- erector spinae group
Muscles run…
in columns, posteriorly
- erector spinae group
Inferior attachment
at a common origin